OF TH E

•School oj^i^edicine.

THE

RUDIMENTS

OF

CHEMISTRY

THE

RUDIMENTS

OF

CHEMISTRY;

ILLUSTRATED BY EXPERIMENTS

AND

COPPER PLATE ENGRAVINGS OF CHEMICAL APPARATUS.

BY

SAMUEL PARKES, F.L.S. F.S.A. Ed.

Memb.-r of the Royal Institution of Great Britain ; Fellow ot the Geological Society ot 1 /inrion, and of the Wernerian, Horticultural, and Highland Societies of Scotland ; Member of the American Philosophical Soci' ty, the Imperial Natu- ral History Society of Moscow, and the Academy of Me- dicine .it Marseilles ; Honorary Memberof the Royal Geo- logical Society of Cornwall, the Antiquarian Society of Newcastle-upon-Tyne, the Agricultural Soneties of Phila- delphia and Massachusetts, and Hi- Society for the Pro- motion of National Industry and the Arts ai Lisbon ; Cor- responding Member of the Literary and Philosophical So- ciety of Manchester, the Academy of Natural Sciences in Philadelphia, the Philomathique Socifilj. ot Paris, and the Imperial Agricultural Society of Moscow, &c. AVTHOU of the CHEMICAL CATECHISM, THE CHEMICAL ESSAYS, &c. &c.

A NEW EDITION,

Carefully corrected, and adapted to the present state < Chemical Science. *^0

£>■*• tf

PHILADELPHIA*.

PRINTED AND PUBLISH' D BT ABllAHAM SMALL

1823.

PREFACE

TO THE FIRST EDITION

The Author of the following pages had often been requested to compose an Elementary Treatise on Chemistry, which, while it possessed the simplicity and perspicuity at which he aimed in composing the " Chemical Cate- chism," might, by a reduction of its size, be af- forded at a much lower price : but a variety of avocations had induced him to decline this pro- posal, until the applications became too numer- ous and respectable to be refused. He has however now entered on the proposed task ; and, having made the Chemical Catechism the basis, he has taken pains to accommodate that system to the improved state of chemical know- ledge ; in hopes that this little volume may not only be acceptable to those masters of semina- ries, and other friends, at whose particular so- licitation it was at first projected, but also have some claim to general patronage.

In pursuing the plan of the Chemical Cate- chism, this work is also divided into Thirteen

VI PREFACE.

Chapters ; and it has been the Author's endea- vour to draw up the whole in such language as might be easily comprehended by any capacity. The principal chemical facts are here print- ed in a larger type, and numbered progressive- ly. These should be considered as axioms to be treasured up in the mind of the student, as a foundation for the superstructure of all his future chemical attainments ; they should there- fore be read first without any attention to the smaller type ; for, as one position frequently arises as it were from others that precede it, the connection of the whole will be more rea- dily perceived by this method, and the facts re- membered with more certainty.

All the illustrations and experiments are given in a smaller letter, which distinguishes these sufficiently from the axioms. They are print- ed immediately under the respective axioms which they serve to elucidate ; and, being thus connected, the rationale of each example will be at once understood by the student. This part of the plan is the most striking feature peculiar to this book, in which it differs essen- tially from the Chemical Catechism, where the experiments stand unconnected with the work; in order that the student might exercise his in- genuity and memory, to discover the different laws of Nature by which they are governed.

To render the work still more instructive, a very large addition has been made to the num- ber of the experiments, besides a collection of copper-plate engravings, containing some of the more approved and useful chemical implements*

PREFACE. VII

The Author hopes therefore, that, while the Chemical Catechism is better calculated for the more advanced students, this small essay will be found suitable to those who are just enter- ing on the study of this science ; and that, where the young people are encouraged by the preceptor to perform the experiments alone, and make themselves thoroughly acquainted with the chemical principles on which they are founded, their progress must ultimately be cor- rect, rapid, and pleasing.

ADVERTISEMENT

TO THE THIRD EDITION.

The motives which induced me to undertake this little work, and the reasons which deter- mined me to adopt the peculiar plan on which it is arranged, have been so fully explained in the preface, that very little need be added on presenting a new edition to the public. To those who are already in possession of the Ru- diments of Chemistry it will be obvious that this is printed on a larger and better paper, and that the new matter which has been added since the publication of the first edition, has enlarged the volume full one-fourth beyond its original size.

In preparing for this impression, the whole work has been carefully examined, and a great part of it re-written, in order to adapt it to the present state of chemical science. The Vo- cabulary of Chemical Terms has also been en- larged and corrected, and a considerable ex- pense has been incurred in engraving new Plates.

Neatness as well as utility having, been thus studied in the publication of this edition, I

V1U ADVERTISEMENT.

flatter myself that not only the Tyro, but the more advanced student, may find it a conve- nient pocket volume, and be induced to use it as a kind of vade-mecum, or memoranda che- mica, on all occasions.

London, October 28, 1822.

CONTENTS.

Chap

	Pages.
9. 1. Introduction,	13
2. Of Atmospheric Air,	- 19
3. Of Caloric, -	31
4. Of Water,	- 47
5. Of Earths, -	57
6. Of Alkalies, -	- 74
7. Of Acids	89
8. Of Salts,	117
9. Of Simple Combustibles,	- 147
10. Of Metals,	174
11. Of Oxides, -	- 247
12. Of Combustion,	263
13. Of Affinity and Repulsion,	- 275

An Explanation of Chemical Terms, 287

General Index, - 303

in iji m i:\rs or chemistky. ;■/„/,■//

HI DJMI.VTS i '.'■ < ■ I! KM IS THY y,///A, ///

mi: vr.v or chemistry. /■/<//,• /\:

J-iu. //.

/ e>	©	o
	/>,/ /;>
V			\l

Via 16

era

Rl'lJlMEXTS OT CMEMJSTKS //„,,. V

In, 13.

v

I

//,/ /!>

Cb '"""

Rl DIM i:\TS t T ( MBMIS THY JVl//t, , y

Tin 23

—

Tw 24.

V

Tia 25

/■'h j W

fli'DJME.VTS Ol CJBFEMrSTHY, IfafplT.

-R1ZDIMENTS OF i UHMISTRY. r v<, r///

DESCRIPTION OF

THE PLATES.

Plate I.

Fig. 1. Represents an apparatus useful foi many kinds of . distillation. A the furnace, B a tubulated retort containing the materials to be distilled. I) a glass balloon, supported by the stand E, to receive the first products of the distillation. C is an adopter for connecting the retort with the receiver, so as to keep the latter at a sufficient distance from the heated materials. F a series 6f tubulated glass bottles, connected together by bent tubes, and forming what is usually called a Woulfe's apparatus.

Fig. 2. represents a common glass retort ; an instrument much used in chemical laboratories for various purposes.

Fig. 3. is a tubulated retort, that is, an in- strument like the latter, with an orifice at the bend and with a ground stopper to fit it. This is the most useful kind of retort, as materials 1#

XIV DESCRIPTION OF THE PLATES.

may be put in through the tubulure during an operation.

Figs. 4. 5. and 6. are crucibles of various de- scriptions. They may be made of metal, of black-lead, or of any refractory argillaceous earth. Those made of baked and raw clay, and of the shape marked fig. 4. are usually called Hessian crucibles ; fig. 5. is the common shape of the black-lead crucible; and fig. 6. is com- monly called a melting-pot.

Plate II.

Fig. 7. is a glass-bell to be inverted over wa- ter and filled with oxygen gas, for the combus- tion of phosphorus, iron wire, &c.

Fig. 8. a bent funnel, with Welter's tube of safety. A glass funnel of this description is extremely convenient, as, on account of the curvature in the stem, any acid or liquid may be affused upon other ingredients, while nova- pour or gas is suffered to escape out of the ves- sel ; and this, in many chemical processes, is often essentially requisite.

Fig. 9. is an apparatus for obtaining hydro- gen gas, and may be thus described. C an iron barrel passed through the furnace B, so as to be made red-hot. A is a bent funnel for convey- ing water very gradually into the heated tube. In this way the water becomes decomposed, and the hydrogen, now converted to hydrogen gas, and passing along the tube D, is collected within the glass jar E which stands inverted in a bason of water to receive it.

DESCRIPTION OF THE PLATES. XV

Fig. 10. represents a glass matrass standing on a common wreath or cushion of straw. This vessel is very useful for making digestions, as from the length of its neck it more readily prevents any loss from an unexpected ebullition of the materials within it. In a great variety of experiments, however, nothing answers bet- ter than a comuiuu oil-flask.

Fig. 11. A bladder-gas-receiver. This may be furnished either with a metallic tube and stop-cock as here represented, or fixed on a piece of common tobacco-pipe, which, if firmly inserted in the cork of the jar, will often be suf- ficiently accurate. The bladder should first be moistened, and the common air pressed out pre viously to the admission of any other gas.

Plate. III.

Fig. 12. an apparatus for collecting gas from coal for lighting mines, manufactories, &c, and which may be seen described at some length, with an account of the method of employing the gas, in the 3d edition of the Chemical Catechism, page 539.

Fig. 13. an apparatus for the distillation of phosphorus from from phosphoric gla:*s. A is a section of the furnace. B an earthen re- tort, C a vessel with a long neck and partly filled with water, to receive the phosphorus as it comes over from the retort.

XVI DESCRIPTION OF THE PLATES.

Plate IV.

Fig. 14. represents a sand-heat constructed with several flat iron plates rabbeted together and secured by a fire lute. A is an iron rim for holding the bed of sand. B the bars of the fire-place, C a flat vessel of glass or earthen- ware for containing the liquor to be evaporated, several of which may be arranged on the same bed of sand.

Fig. 15. a small wooden stand for the sup- port of funnels, the feet of which should be high enough to admit of vessels standing underneath to receive the liquors as they pass through.

Fig. 16 Dr. Black's portable furnace, very useful in various operations of chemistry.

Plate V.

Fig. 18. of this plate, and fig. 34 in Plate VII. represent different views of a furnace in- vented by Mr. Knight. These furnaces, which have some advantages peculiar to themselves, are sold by the inventor, in Foster-lane, Cheap- side, and a particular description of them may be seen in Henry's Epitome of Chemistry.

Fig. 19 a pneumatic trough filled, and ajar B placed on the shelf; — this jar, for some pur- poses, may be close at the top, as represented in the figure, or, if open, the neck should be so contrived as to admit either a glass stopper, or a stop-cock ; Ihus with great ease any gas, col- lected in this jar, may be readily transferred into another vessel, or into the bladder receiver,

DESCRIPTION OF THE PLATES. XVII

fig. 11. Plate II. The bottle A, which hangs by its bent tube to the side of the trough, is the same as the gas bottle, fig. 27. Plate VII. de- signed for the extemporaneous formation of elastic fluids, which, as they are evolved, pass through the tube to the inverted jar on the shelf of the pneumatic trough.

Fig. 20. represents a wind furnace employed by the refiners of gold and silver, for melting the metal in crucibles, after it has undergone the operation of parting.

Fig. 21. a glass funnel made with small chan- nels on its surface to allow of the passage of air from the vessel, while the liquid drops in and supplies its place.

Fig. 22. an utensil of cast iron, called a plumber'' s pot> useful for many purposes, and particularly to form a sand-heat for a single retort.

Plate VI.

Fig. 23. is a representation of another variety of Woulfe's apparatus, being more simple than that described Plate 1. fig. 1. A is a small moveable lamp ; B the retort to be heated by the lai»p A- C a glass receiver standing on a wreath of straw. DD are the connecting tubes to convey the gas from one vessel to another, as the contents of each become saturated ; EE are tubulated bottle receivers ; and FF tubes of safety which dip into the liquor sufficiently to make the apparatus air-tight, and yet not far

IV1U DESCRIPTION OF THE PLATES.

enough to prevent the escape of gas whenever there might otherwise be a danger of explosion.

Fig. 24. a hydrostatic balance for ascertain- ing the specific gravity oi solid substances. The solid is here represented as immersed in a jar of distilled water.

Fig. 25. represents a glass jar, inverted over the flame issuing from the combustion of hy- drogen gas. In this case the oxygen of the at- mosphere combines with the hydrogen, and wa- ter is formed, which will evidently appear at- tached to the inside of the inverted jar.

Fig. 26. a dish for evaporating small quanti- ties of any fluid. Such utensils are made of glass, earthenware, silver or platinum. For many purposes, however, nothing answers bet- ter than a common watch glass.

Plate VII.

Fig. 27. is a gas -bottle the same as that de- scribed at fig. 19, Plate V.

Fig. 28. an adopter of earthen-ware or glass, for connecting a retort with a l^ceiver, as shown in Plate 1. tig. 1.

Fig. 29. a gravity-bottle for ascertaining the specific gravity of any kind of fluid, whan com- pared with that of distilled water. By Wing the neck of the bottle very small, and always filling it to a certain mark on the neck, the specific gravity of any liquid may be found very accurately.

Fig. 30. a glass utensil for dropping liquids regularly. By immersing it in any fluid, and

DESCRIPTION' OF THE PLATES. XIX

then emptying it of air by the mouth, it will be filled by the pressure of the atmosphere to any height that may be wished ; and then by placing the thumb on the larger orifice, the liquor may be preserved within it, and on removing the thumb the liquor issues out in regular drops at pleasure.

Fig. 31. a glass-jar with a tube firmly luted into one of its tubulures, for the purpose of forming the philosophical candle.

Fig. 32. an alembic. The whole of this may be made either of glass, porcelain-clay, silver or platinum. The head, which is moveable, may be luted on with putty, or any other suita- ble lute, during an operation. It may be seen that the head is hollowed in such a way, that whatever condenses there and trickles down must collect in the interior current, and pass on through the spout into a receiver.

Fig. 33. a pair of tongs for removing cruci- bles or melting-pots, &c. from the furnace.

Fig. 34. another representation of Mr. K. night's furnace, described fig. 18. Plate V.

Plate VIII.

Fig. 35. a distilling apparatus. The retort and its receiver are placed on the same stand ; the receiver has an opening on one side fitted with a glass stopper, and its tubulure is inclined so as to receive the beak of the retort, to which it is to be luted. When things are thus prepared for an operation, an Argand's lamp may be

XX DESCRIPTION OF THE PLATES.

placed beneath the retort to give it the required heat.

Fig 36. a common blow-pipe.

Fig. 37. a self-acting blow-pipe, the globular part of which contains alcohol, the vapour of which is made to pass through the flame of the lamp by which it is raised into vapour.

Fig. 38. a retort funnel. The use of this in- strument is to fill a retort after it is fixed in a sand-heat, or when its beak stands in a horizon- tal position.

Fig. 39. a copper utensil employed for eva- poration or digestion.

Fig. 40. an iron ring for suspending a retort within a furnace, whenever we wish to expose it to the direct action of the fire. This ring is itself supported above the fuel, by means of the three small projections which appear in the drawing.

Fig. 41. is -a refrigeratory, or worm -tub, for condensing the fluid products of distillation. The outer vessel for containing the cold water may be made of wood, earthenware, or metal, but here it is supposed to be formed of japanned tin. The curved tube or worm which passes throughthe water, is usually made of fine tin or pewter.

RUDIMENTS

CHEMISTRY.

CHAPTER I.

INTRODUCTION.

1. Chemistry is the science which enables us to discover the peculiar properties of all natural bodies, either in their simple or com- pound state.

The following was Dr. Black's definition of chemistry: " Chemistry (said he) is the study of the effects of heat and mixture, with the view of discovering their general and subor- dinate laws, and of improving the useful arts."

2. The chemical examination of bodies is in general effected by producing a change in the nature or state of the body under examination.

This change is frequently effected b\ the addition of some substance which can form a combination witli a part of the substance under examination, and leave the othi r part in a detached state: On this principle reagents, or chemical tests, are employed.

Experiment. — Epsom salt is composed of sulphuric acid and magnesia. If some of this salt be dissolved in water, it will form a transparent solution : but the moment a little of the solution of caustic soda is poured in, the sulphuric acid will unite with the soda, and the magnesia will be precipitated in the form of a white powder.

B

14 INTRODUCTION. [Ck. 1.

3. A change in the qualities or state of any substance is generally effected by means of/teat, or by the mixture of some other matter with the matter intended to be examined.

Heat has a tendency to separate the pai tides of all bodies from each other.

Exp. 1. — If water be poured into a solution of camphor in spirit of wine or alcohol, the camphor will be immediately precipitated.

Exp. '2. — When (he whole of the camphor has fallen down, pour the fluid into a small retort, and apply a gentle heat. By this means the alcohol maybe raised in the form of vapour, oondei sed in the recipient and thus separated from the water, •which will remain in the retort.

4. By these means we effect the decomposi- tion of a compound body, and thus acquire a knowledge of the nature of its ingredients.

This is also called analysis, and is distinguished by chemists into the simple and the complicated analysis.

Exp. — Take a few grains of citric acid, and twice as much dry carbonate of potass, or of soda, both in powder; mix them, ai;d put them into a dry glass. Whilst the mixed powders remain in this state no chemical change will take place in either of these salts; but the moment water is poured upon them, an effe: vesce nee will ensue ; affording an instance of the necessity of water to promote some chemical decom- positions.

5. Tn chemical language, decomposition* means the art of dividing a body into its simple elements.

By various processes wiiter may be decomposed, and re- duced intooxygen and hydrogen, which are simple substances, incapable of further decomposition,

6. The matter which constitutes this lower world is usually divided by philosophical wri- ters into four classes; viz. solid, liquid, aeri- form, and imponderable.

When cohesive ^ffi dtj between the particles of a body is] strong, that body is a solid ; when this affinity is considera- bly diminished by heat, the body becomes fluid ; but when suf-

Ch. 1.] INTRODUCTION. 15

ficient heat is applied to destroy the cohesion altogether, the particles of the body then begin to repel each other, and thus a vapour or a gas is formed.

7. Solidity is that quality of bodies whereby their parts cohere firmly, so as to resist impres- sion.

8. Liquid substances are those whose parts do not cohere firmly, but readily yield to any impression, and have free motion among them- selves. They also assume, when in small masses, the spherical form, as may be observed in de- tached portions of mercury, and are incapable, by any common mechanical force, of being compressed into a smaller compass.

We have no reason to suppose that fluidity is an essential property of any liquid substance whatever; but rather that solidity is the natural state of all bodies, for we are able to reduce most substances toa s'ale of fluidity by means of heat.

On th«> contrary, 'the g i at< ^t number erf liquid substances take a solid form by reduction of temperature. A< in the in- stancr ol water, which, *h n deprived ol a certain portion of its beat, congeals and forms ice.

9. All elastic fluids, usually called vapours and gases, belong to the class of aeriform sub- stances.

These aeriform substances are call -d elastic, because they are ail capable ot being reduced into a smaller compass by pressure, and of expanding again to their usual volume when- ever the pressure is removed.

10. The imponderable bodies with which we ! are acquainted, are only four ; viz. light, caloric,

electricity, and magnetism. They are also sometimes denominated unconfinable,or.ethereal substances.

In this introductory chapter, it has been found most conve- nient to n-eat only of the solid and liquid state of bodies ; the aeriform and imponderable states of matter will be consi- dered hereafter.

16 INTRODUCTION. [CIl. 1.

11. It must be recollected that liquid sub- stances are merely solids converted into liquids by heat, a certain increase of which would con- vert any liquid into an elastic vapour.

Fluidity is owing to the matter ofJieat being interposed be- tween the particles of the fluid; which heat would dissipate all fluids into the air, were it not for the pressure of the at- mosphere, and the mutual attraction which subsists between those particles.

Exp. 1. — A little bees' wax placed near the fire will show that heat alone is sufficient to render the solid wax a fluid.

Exp. 2. — A little lead melted in the bowl of a tobaccn-pipe ■would furnish a familiar instance of the metals becoming fluid by heat.

12. Liquids are likewise called fluids: we call the air a fluid.

13. The air is called a fluid, because it flows like a fluid : because, like a fluid, it presses in every direction ; and because light substances will swim in it.

The facilit> and rapidity of thf> motions of atmospheric air cannot be explained on any principle but its fluidity. Some of the winds move at the rate of 3000 feet in a minute. The air is also known to be a fluid, by the easy conveyance which it afforls to sound.

Exp. — To show that the air presses in every direction, fill a wine-glass with water, and place a moistened card upon it ; if the glass be then carefully inverted, the water will not es- cape, as the pressure of the atmosphere upon the outside of the card will, enable it to support the water.

14. It is an established law of nature, that all substances will swim in fluids which are specifically heavier than themselves.

If a cork be placed at the bottom oi a bason of water, it will rise immediately to the surface, because it is specifically light- er than the fluid in which it is immersed ; whereas a stone, being heavier than water, would sink if placed on its surface.

15. Not that the stone is heavier than the iv hole of the water in the vessel ; for, if it be

Ch. 1.] INTRODUCTION". 17

heavier than a portion of water of its own bulk, it must sink.

16. Every substance which swims on water, displaces so much of the water as is exactly equal to its own weight ; whereas, when a sub- stance sinks in water, it displaces water equal to its bulk.

Exp. — Take a piece of hard wood, balance it accurately in a pai. of scales with water, and then place it gently on the sur- face of water in a vessel exactl) filled with that fluid, and it will displace a portion of the water, which will flow over the top of the vessel. If the wood be now taken oat with care, it will be found that the water in the scale will exactl} fill the vacancy left by the wood.

17. The term made use of to express the re- lative weight of bodies, is specific gravity. Thus the specific gravity of one body may be much greater than that of another, though their abso- lute weights be the same.

The specific gravity of bodies is denoted in chemical writ- ings by comparing it with the sp- cifie gravity of pure * iter, in decimal figures, water being always considered as 1.000. Hence if a substance be fire tenths heavier than water, it ie denoted thus, 1.500. TIip specific gravity of all bodies is noted 1 in the same way, throughout this little volume.

18. When one body is larger or takes up more room, than another of the same weight, the first is said to be specifically lighter than the other, and vice versa.

In ordet to ascertain the specific gravity of any solid, it is necessary first to weigh it in common scales in air, and then by means of an hydrostatic balance in watc, (see Plate VI. fig. 24.) and calculate from the diff. rence in its weight when weighed in these two media. For moiv particular directions, see The Chemical Catechism, Tenth Edition, page 24, &tc.

19. A pint measure of hydrogen gas weighs little more than half a grain, whereas a pint of atmospheric air weighs nearly nine grains, and

2b

18 INTRODUCTION. [CIul,

the same measure of pure water weighs up- wards of one pound avoirdupois.

The measure here alluded to is the common wine pint. From this one may deduce by calculation, that a cubic foot of atmospheric air weighs nearly one ounce and a quarter, and a cubic foot of water 1000 ounces, avoirdupois.

20. If the specific gravity of water be so much greater than that of atmospheric air, it may be asked, how is water retained in the at- mosphere ? When bodies change their state, their specific gravity is generally altered.

Water exists in the atmosphere in abundance even in the driest seasons, and under the clearest sky. There are sub- stances which have thr power of absorbing water from the air at all times, such as thn fixed alkalies and sulphuric acid ; the latter of which will soon absorb more than its own weight of water from the air wh^n exposed to it.

21. The water which is taken up by the at- mosphere is not. in an aqueous state, but is con- verted into vapour by the matter of heat.

Exp. — By inverting a glass goblet over a cup of hot water, the vapour will be seen to rise into it, to condense upon the cold glass, and then to run down its inside ; which will show that steam is reel water, and will, when the caloric is ab- stracted, become water again.

Here the pupil may be informed that water not only be- comes converted into steam by heat, but that when it is re- ceived into the atmosphere, if the air be warm it becomes sp far changed- by its union w;th the-matjer of heat as to be per- fectly invisible. In this state it occupies a space 1400 times greater than its ordinary liquid state.

The vapour arising from boiling water is visible only in consequence of it^. being partially condensed by a cold atmos- phere, as may be demonstrated by causing water to bojl in a Florence flask ever a tamp; for in this case, the steam within the neck of th<- flask will be found to be entirely invisible.

22. This principal of evaporation is of very- general utility : it is subservient to many natu- ral and artificial processes, and is of perpetual use to man in every occupation of life.

Cfl. 2.J ATMOSPHERIC AIR. J 9

The effects of evaporation are of eminent importance to the practical chemist. By this means fluids are separated from solids and one salt from another in various operations of the laboratory. Sometimes artificial and at others spontaneous evaporation is employed for these purposes.

Whenever fire is used to separate the water from aqueous solutions, it is called artificial evaporation ; when this is effect- ed by exposing the mixture to the action of the sun and air, it is called spontaneous evaporation. In separating common salt from sea water, both these methods are adopted.

A little consideration would convince any one of th" im- portance of this principle of evaporation even in the common affairs of life. Innumerable instances of its use might be ad- duced : suffifte it to say, that without it neither grass nor corn could be sufficiently dried to lay up for use. Our clothes when washed could not be dried ; neither could a variety of the most common operations be carried on, which conduce much to our comfort and convenience.

CHAPTER II.

OF ATMOSPHERIC AIR.

23. The air is that very light fluid which surrounds us every where : it is the medium in which we live, and without which we could not exist.

24. This great body of air is called the at- mosphere.

25. The obvious properties of atmospheric air are fluidity, elasticity, expansibility, and gravity.

26. If atmospheric air be compressed into a small compass, it has the property of recover- ing its former state, as soon as the pressure i* removed ; which is called its elasticity.

20 ATMOSPHERIC AIR. [Ch. 2.

Atmospheric air may be compressed into about the 128th of its usual volume. It is now generally supposed that the air owes its elasticity to caloric ; and that if it could be entire- ly deprived of the matter of heat, it would lose its elastic form.

Exp. — If a bladder be tied up with a very small quantity of atmospheric air within it, and put under the receiver of an air pump, it will be seen to inflate gradually as the receiver is exhausted, till it attains its full size; owing to the elasticity of the small quantity of air within the bladder, which dilates in this manner, as the atmospheric pressure is removed.

27. The expansibility of the air is its proper- ty of being rarefied by heat, so as to occupy a larger space than it would be at a lower tempe- rature.

It has been calculated, that the air which is disengaged in the firing of gunpowder is rarefied by the heat, so as to occu- py a thousand times the space of the whole of the gunpowder employed.

Exp. — If the neck of a bladder, containing a small quantity of air, be closely tied up and held to the fire the swelling of the bladder, by the rarefaction of the air within it, will afford an idea of thr expansibility of the air.

28. The atmosphere is necessary for the sup- port both of animal and vegetable life.

It has been ascertained by experiment, that no other gase- ous body with which we are acquainted can be substituted for atmospheric air. All the known gases have been tried ; but they all prove fatal to the animal which is made to breathe them.

29. The atmospheric air is indispensable in all the common processes of combustion.

Exp. — Light a small taper, place it upon a plate, and hav- ing poured a little water upon the plate, invert a glass jar over it. In this situation the taper will burn for some time ; but when the air within the jar is consumed, the taper will be extinguished.

30. It gives buoyancy to the clouds, and en- ables the feathered creation to transport them

Ch. 2.] ATMOSPHERIC AIR. £1

selves with ease from one part of the earth to another.

This fact affords a fresh instance of the harmonies of nature , and of the suitableness of every creature to the medium, in ■which it was designed to live. The density of th-? air, near the surface of the earth, we see is exactly what was re- quisite for the residence of the feathered race ; and the spe- cific gravity of every individual, of every species, is just suffi- cient to enable it to occupy that element, and to move with- in it at all times with ease and safety.

31. The atmosphere extends several miles above the surface of the earth.

If the atmospheit" were of the same density throughout, its height might be known by its effect in raising a column of mercury in a tube ; but as it increases in rarity the higher it ascends, we cannot possibly tell how far it may extend. This however, has been estimated by the length of our twilight j and it is now supposed to be about 45 miles high.

32. It is this great extension of the atmo- sphere which occasions its weight ; and the pressure of such a weight produces many im- portant effects in the economy of nature.

Exp. 1. — Invert a tall glass jar in a dish containing a little watf^r, and place a lighted taper under it as directed No. 29. As the taper consumes the air in the jar, its pressure becomes lesson the water immediately under the jar; while, the pres- sure of the atmosphere on the water without the circle of the Jar remaining the same, part of the water in the dish will be forced up into the jar, to supply the place of the air which the taper has consumed. Nothing but the pressure we are speak- ing of could thus cause a part of the water to rise within the jar, above its own level.

Exp. 2. — The reality of atmospheric pressure may be ex- plained and demonstrated by a common barometer, merely by showing how it acts upon that instrument.

" In tubes of glass mercurial columns rise, Or sink, obedient to the incumbent skies."

33. It is owing to the weight of the atmo- sphere that we are enabled to raise water from beneath the surface of the earth, by the com-

22 ATMOSPHERIC AIR. Ck. 2] I

mon pump, and to perform many other useful I operations.

The atmosphere presses equally upon the whole surface of the water in the well, until the rod of the pump is moved ; but by forcing the rod down, the bucket compresses the air in the lower part of the pump tree, which being elastic forces its way out of the tree through the valve ; so that, when the buck- et is again raised, that part of the pump tree under the buck- et is void of air ; and the weight of the atmosphere pressing I upon the body of water in the well, forces up a column of water to supply its place ; the next stroke of the pump rod causes another column of water to rise : and so long as the bucket fits the pump tree close enough to produce a vacuum, a constant stream of water may be drawn from below.

"Press'd by the incumbent air, the floods below,

Through opening valves, in foaming torrents flow,

Foot after foot in lessen'd impulse move,

And rising seek the vacancy above." On the tops of very high mountains, water will boil much sooner than on the plains, where the atmosphere is heavier; I at the top of Mont Blanc it has bt en known to boil at the tem- perature of 187p of Fahrenheit ; and it has been observed that many spirituous liquors, such ascther ;md spirits ot wine, lose the best part of their qualities when exposed at such heights.

34. If we had little or no atmosphere, we should have no water ; for the waters on the face of the earth would all evaporate at a very inferior temperature.

Exp. — The quick evaporation which would take place if ' we had no atmosphere, may be shewn by a common instru- ment, invented by Dr. Franklin, called a pulse glass. It is a small tube with a bulb at each end, exhausted of air, and con- taining a small quantity of spirits of wine. If this instrument be held sloping, with one end in the palm of the hand, the heat of the hand will quickly cause the spirit to boil ; but tiie va- pour rising to the other end becomes condensed as soon as it comes in contact with the cold glass. This simple experi- ment shows that a very small degree of heat would be suffi- cient to evaporate most of our fluids, if we had no atmos- sphere.

35. The weight of the atmosphere, pressing •n the water, binds it down as it were, and pre-

Eh. 2.] ATMOSPHERIC AIR. 23

vents the usual heat of the sun frflm converting this and all other fluids on the face of the earth into vapour.

£.r/>.— That the waters on the face of the faith would he dissipated in vapour by a small degree of heat, if we had no atmosphere, may be shown by the following easy experi- ment: — Procure a common oil flask, let this be-about one thin) filled with water, and heat it over a lamp. YVben the water boils, remove the flask, cork it closely so as to exclude the air, and plunge it for a moment into cold water, nearly up to the mouth of the flask. This will not only cool the hot water in some measure, but it will entirely condense the vapour which occupied the upper part of the flask, and occa- sion so great a vacuum, that the water which had been thus partially cooled, will be seen to recommence its boiling with great violence. This effect can be attributed to nothing but the vacuum which has been formed in the upper part of the flask, and to the cork preserving the water from the pressure of the atmosphere. In like manner, wafer wbich has been COOlfcd many degrees below boiling will begin to boil again, if placed under the receiver of an air pump, as soon as wc begin to exhaust the receiver of its air.

36 Each square foot of the eartlvs surface sustains about 2160 pounds of atmospheric air. A column of air an inch square weighs about fifteen pounds.

It has been computed that the weight of the air which presses upon the whole surface of the earth, is equal to that of a globe of lead sixty mileS" in diameter.

It is necessary to remark that the air presses upwards, downwards, and sideways, in every direction ; and that it is owing to tli is equal pressure that we are not injured by the vast weight of the atmosphere ; for the equal pressure on all sides resists as much as it is resisted.

Ejp — Whenever I hold my hand out in this fluid, I feel no weight upon it, because the pressure under and above my hand is equal ; but if I lay my hand on a hollow cylinder of glass, placed on the plate of an air pump, and exhaust the cy- linder of air, I become immediately conscious of something that presses it so forcibly to the glass, that I cannot endure it. The prop is now gone ; I have no pressure under my hand; a column of air 45 miles high forces it down by its weight,

%tk ATMOSPHERIC AIR. [CIl. 2.

and I must let inthe air under it before the hand can be with- drawn.

37. This immense atmosphere is composed of oxygen and nitrogen, two different airs, which are intimately mixed in certain definite proportions.

It has been determined that the air of Europe, Asia, Africa, and America, differs very little in the proportion of its ingre- dients.

Atmospheric air is not a chemical compound of nitrogen and oxygen, but a mere mixture of those gaseous substances, with a small proportion of carbonic acid gas. The uniformity of this mixture has been accounted tor by Mr. Dalton in a very satisfac'ory manner. This gentleman discovered that the gases act as vacuums to each other ; and that if two jars of different kinds of gas are placed one above the other, and the lighter gas be placed uppermost, with a proper connexion between the two vessels, a portion of the lighter gas will soon be found to have descended through the heavier gas, and part of the heaviest gas will also be found to have ascended through ;he lighter one; and this interchange will continue to go on until an uniform mixture of the whole is produced.

38. Atmospheric air contains also about one part in every thousand of carbouic acid gas, and several adventitious substances.

It has been calculated that the absolute quantity of carbonic acid gas, dispersed throughout the atmosphere, ameunts to more than one hundred millions of hundred millions of pounds avoirdupois. For an account of the rises of this enormous quan- tity of cauboi ic act.' ga? in the atmosphere, "consult Chem. Catechism, Tenth Edit, page 249—254.

Exp. — If 80 acid be poured upon a pure alkali, no effer- vescence wiP be perceived ; but t^ke a little of the same kind of alkali and expose 't to the air for a few hours, it will then effervesce b< th ! addition of an acid; which shows that it has absorbed eai bonie acid from the atmosphere.

39. Besides carbonic acid gas, it holds a portion of water in solution ; and sometimes contains hydrogen and carburetted hydrogen gases.

Ch. 2.] ATMOSPHERIC AIR. 25

Upon an average, atmospheric air contains about 1 per cent, •f water in the state of elastic vapour, and it is remarkable, that whenever aqueous vapour is united to atmospheric air, an augmentation of volume is the consequence, and damp air is always specifically lighter than dry air.

40. When solid substances are rendered per- manently aeriform by heat, the air thus pro- duced is called a gas, to distinguish it from those aeriform substances which return to the solid or fluid state when the heat is abstracted.

All the gases art; compounds of solid matter and caloric. It is caloric w hich separates the particles, and gives to the whole a gase'ousform.

The simple gases are elastic, transparent, and permanently aeriform, unless condensed by chemicaJ combinations. Few of them possess any colour.

The permanency of the gases appears to be owing to the strength of the affinity existing between caloric and their bases, which affinity resists every redoctiou of temperature.

41. By the operation of different agents, the several gases may be separated from each other, and the quantity of each ascertained.

A pneumatic trough is generally employ, cl for collecting gases, and for transferring them from one vessel to another. See Plate V. fig. 19.

42. With respect to the proportions of these gases, there are 21 parts of oxygen gas, and 79 of nitrogen gas, in every 100 measures of at- mospheric air, or 23 of the former and 77 of the latter, (fractions omitted,) if the calculation be made by weight.

Exp. — The pupil may be satisfied of the truth of these pro- portions in various ways; — the following is the: easiest: A light- ed taper will not burn in nitrogen gas a moment; if immeised in oxygen gas, it burns with a splendour too great for the eye to endure ; but if four measures of nitrogen gas and one "of oxygen gas are put into ajar inverted ovei wattr, and a light- ed taper put into such mixture, it will burn exactly the same as it does in atmospheric air.

c

26 ATMOSPHERIC AIR. [C/l. 2 J

43. These gasses are of different and oppo-J site qualities.

They are of such opposite qualities, that the one is some- • times called vital air ; while the other, from its causing the death of those who breathe it, has been called azotic gas.

44. The oxygen gas in atmospheric air is the principal supporter of combustion, and the vehicle of heat ; and is, as was before mention- . ed, absolutely necessary for the support of ani- mal life.

Exp. — Pour a little water on a flatdish, place two or three lighted wax tapers of different lengths in the water, and in- vert a tall glass jar over them. The flame of the different ta- pers will soon be seen to giow smaller, and at length will be extinguished in succession. That which is highest will be ex- tinguished first, and the shortest taper the last, owing to the purer air occupying the lower part of the jar.

An account of a melancholy accident which happened to two men in consequence of iheir being deprived of atmosphe- ric air, may be seen in the Chemical Catechism, Tenth Edi- tion, page 48.

It has been asserted that oxygen is neeessary to promote the vigour of plants as well as that of animals.

"Leaves, Lungs, and Gills, the vital ether breathe On earth's green surface, or the waves beneath."

45. Pure oxygen gas has the property of ac- celerating the circulation of all the animal fluids, and occasions the most rapid combus- tion of -all combustible substances; so that it is the most energetic and powerful agent that we are acquainted with.

Exp. 1. — It is an interesting experiment to place a glow- worm within a jar of oxygen gas, in a dark room. The in- sect will shine with much greater brilliancy than it does in at- mospheric air, and appear more alert. As the luminous ap- pearance depends on the will of the animal, this experiment probably affords an instance of the stimulus which this gas communicates to the animal system.

Exp. 2. — Attach a piece of common sulphur about the size ©fa small bean, to the end of an iron wire, and set fire to it.

Ch. 2.] ATMOSPHERIC AIR. 27

It will bum with a slow combustion ; but if it be plunged in an ignited state into ajar of oxygen gas, it will then burn with a splendour almost too strong fop the eye to endure. The jar made use of should be similar to that employed for burning iron wire. See Plate II. fig. 7.

46. Ox}gen gas is a little heavier than at- mospheric air, and about 750 times lighter than water.

A>. the temperature of fi0° when the barometer stood at 30° it was determined by Messrs. Allen and Pepyslhat 100 cubical inches of oxygen gas weigh S3.S2 grains. Sir Hum- phry Davy states it al 3i grains.

Oxygen gas is plentifully procured from nitre, or from the black oxide of manga. iese.

47. Nitrogen gas, or azote, is chiefly distin- guished by certain negative qualities, such as its being incapable of supporting combustion and animal life. It is uninflammable, and some- what lighter than atmospheric air.

Nitrogen forms a part of all animal substances. It is also the base of ammonia, and of the nitric acid. It appears to be favourable to plants, as they grow and vegetate freely in this gas.

ExJj. — Take a few iron filings, mix them with a little sul- phur, and moisten the mass with water. Put this mixture into a large glass jar, and cork it close. In a few days the oxygen will be absorbed by the mixture from the air which was previously in the glass, and the residuum will be found to be nitrogen gas. It may be procured also by digesting pieces of flesh or the muscular fibre in very dilute nitric acid.

48. Nitrogen gas has the effect of neutraliz- ing, in some measure, the properties of oxygen gas, and rendering it fit for respiration and com- bustion.

[Though nitrogen gas is, by itself, so noxious to animals, it answers an important end when mixed with oxygen gas in at- mospheric air. Were it not for this large quantity of nitro- gen in the atmosphere, the blood would flow with too great rapidity through the vessels ; the consequence of which would

28 ATMOSPHERIC AIR. [Ch, 2.

be, that the life of man would not be protracted to the length that it now is.

"From Nature's chain whatever link you strike, Tenth, or ten thousandth, breaks (he chain alike."

49. The atmospheric air which is produced by this mixture, supports animal life by giving out its oxygen and caloric to the blood.

The bio od in the veius is pu pie, approaching to black ; but when it arrives at the lungs, having there thrown off hydro- gen arid charcoal, it imbibes the vital air of the atmosphere, which changes its dark colour to a brilliant red, rendering it the spur to the action of the heart and arteries ; the source of animal heat; and the cause of sensibility, irritability, and motion.

Black venous blood, exposed to the air, becomes red on its surface ; and air, remaining confined over venous blood, loses its oxygen, so that what remains is found to be unfit for com- bustion. These facts prove that the vermillion colour of the blood is owing to the inhalation of oxygen gas.

"The internal surface of the lungs, or air vessels, in man, is said to be equal to the external surface of the whole body ; it is on this extended surface that the blood is exposed, through the medium of a thin pellicle to the influence of the respired air"

50. Caloric is the name which modern che- mists have given to lire, or the matter of heat ; a large portion of which is intimately combined with atmospheric air.

This name was given by the framersof the new nomencla- ture to the matter of heat, which they always distinguish from the effect." Caloric is applied to fire, or the substance which produces the sensation we call heat, but never to the sensa- tion itself, or the effect produced by fire. In this case it is said that caloric raises the temperature of bodies, or, on the contrary, that the temperature is lowered by the loss of caloric.

51. Animal heat is preserved chiefly by the inspiration of atmospheric air. The lungs, which imbibe the oxygen gas from the air, im- part it to the blood ; and the blood, in its cir-

Ch. 2.] J ATMOSPHERIC AlK. 29

culation, gives out the caloric to every part of the body.

A man generally consumes 32 ounces troy of oxygen gas in 24 hours ; that is, the lungs separate this quantity of oxygen gas from the air which he respires in that time.

Nature has provided for those animals which do not breathe, such as fishes and inst cts, by giving them a bodily tempera- ture but little superior to the medium in which they live. The temperature of other animals is in proportion to the quan- tity of air which they breathe in a given time.

52. As the temperature of the atmosphere in this climate is always inferior to the animal temperature, clothes are necessary to prevent the sudden escape of that heat from the surface of the body which the lungs have separated from the atmosphere.

Clothes keep the body. warm in consequence of the air which they infold within them ; all confined bodies of atmo- spheric air being non-conductors of heat. It is on this prin- ciple that double -windows preserve the warmth of apartments at an equable temperature, and that light spongy substances, such as furs and down, afford the warmest clothing.

53. With regard to the nitrogen that is com- bined with atmospheric air, the greatest part of that is thrown out of the lungs at every re- spiration ; and being somewhat lighter than at- mospheric air, it rises into the atmosphere to await fresh combinations.

It may be remarked, thai the interval which there is be- tween every inspiration seems to have been designed, to allow time for the nitrogen gas which is thrown out of the lungs to mount in the air above the head, in order that a fresh portion of air might be taken in, and that the same air might not be repeatedly breathed. How provident has the Almighty been, in thus foreseeing the operation of those laws which were designed to promote the welfare of every species of animated beings !

54. The loss of that vast quantity of oxygen which respiration and combustion are perpetu-

e 2

30 ATMOSPHERIC AIR. [Ch. 2.

ally taking from the atmosphere, would soon render the air unfit for those purposes, if na- ture had not made provision for its restoration.

Exp. — Take a bladder with a stop-cock similar to that de- scribed in Plate II. fig. 2, and folding the lips carefully round the end of the pipe, begin to draw the air out of the bladder into the lungs, and immediately return it into the bladder by respiration. Thus continue to breathe the same air for some minutes, and then close the stop-cock. If the air be now re- moved from the bladder into a pneumatic glass jar, and a lighted taper immersed within it, it will at once be seen that the process of respiration has rendered the air unfit for sup- porting combustion.

55. The leaves of trees and other vegetables give out during the day .a large portion of oxy- gen gas, which uniting with the nitrogen thrown offby animal respiration, keeps up the equilibri- um, and preserves the salubrity of the atmo- sphere.

The upper side of the leaf is the organ of respiration ; hence some vegetables (as they give out oxygen only in the day) close the upper surfaces of their leaves during the night.

Exp. — To show the production of oxygen gas from the leaves of plants, fill a glass bell with water, introduce leaves under it, and place the bell inverted in a fiat dish of water. Expose the apparatus to the raysof the sun, and very pure oxygen gas will be disengaged, which will displace the water in the jar, and occupy its place. In like manner a sprig of mint, corked up with a small portion of carbonic acid air and placed in the light, renders it again capable of supporting life. The plant purifies what the animal had poisoned.

(C/j. S.] CAJL0R1C. 31

CHAPTER III.

OF CALORIC.

56. Heat is the well-known sensation which we perceive on touching any substance whose temperature is superior to that of the human body.

The sensation of heat and cold arises from the tendency which caloric has to diffuse itself equally amongst all sub- stances that come in contact with it. If the hand be put upon a hot body, part of the caloric leaves the hot body, and enters the hand : this produces the sensation of heat. On the con- trary, if the hand be put upon a cold body, part of the caloric contained in the hand leaves the hand to unite with the cold body : this produces the sensation of cold.

57. Chemists have agreed to call the matter of heat caloric, in order to distinguish it from the sensation which this matter produces.

In order to give precision to chemical language, it was ne- cessary to find a term to distinguish the matter of heat from its effect ; for, whenever caloric becomes fixed in a body, it loses its property of affording he;tt.

58. Caloric is every where indispensable to the existence of man. " It is with fire that, in every country, he prepares his food, that lie dis- solves metals, vitrifies rocks, hardens clay, sof- tens iron, and gives to all the productions of

! the earth the forms and combinations which his necessities require."

59. There are six sources from whence we procure caloric ; viz. from the sun's rays, by combustion, by percussion, by friction, by the mixture of different substances, and by means of electricity and galvanism.

32 CALORIC, [Ch. SM

60. The sun is the chief fountain which fur- I nishes the earth with a regular supply, and ren-' ders it capable of supporting the animal and vegetable creations.

Caloric, it is said, comes to us from the sun at the rate of 200,000 miles in a second of time ; but Dr. Herschel has prov- I ed, that the solar rays which occasion heat, are distinct from I those which illuminate and produce vision.

It is now a prevailing opinion, that the sun is not the origi- 1 nal source of heat, but that the earth, and each planet belong-* ing to this system, is furnished with the necessary portion of caloric, and that the rays of the sun impinging upon the earth I and the other planetary bodies, elicit the native caloric which is inherent in them, and occasion what is called heat.

Exp. — That caloric is as necessary for the support of vege~ table as it is for that of animal life, may be proved by direct experiment. If in the midst of winter a hole be bored in a ' tree, and a thermometer put into it, it will be seen that the tree is many degrees warmer than the atmosphere.

61. The second source we have mentioned is combustion : in this process the oxygen gas of the atmosphere is decomposed, and caloric, one of its component parts, is set at liberty.

For a more particular account of this curious natural phe- nomenon, see the w boh of Chapter XII.

62. The heat produced by percussion is ge: nerally occasioned by the compression of the particles of the body, which compression forces out a portion of its latent caloric.

A:- ?vaporation produces cold, condensation always occa- sions heat : that is, caloric is always evolved from those bo- dies which have undergone any degree of condensation. la onr case caloric is absorbed, in the other it is set at liberty.

By the collision of flint and steel so much caloric is disen- gaged, that the metallic particles which are struck off are ac- tually melted thereby. This is evident, from their being al- ways found in a spherical form.

Exp. 1 . — Mix three grains of sulphur with nine grains of dry nitrate of silver, and lay the mixture in a small heap on an anvilj or on any piece of solid metal. If the mixture be

Ch. 3.] caloric. 53

now struck smartly with a cold hummer, the sulphur will in- flame, but no detonation will ensue. This is an instance of a metallic salt being decomposed and a combustible substance inflamed by percussion.

Exp 2. — lithe experiment be repeated, and the mass be struck with a hot hammer, the mixture detonates, and the silver is reduced.

63. It is not known how friction produces caloric, unless we suppose it to be a succession of percussions.

The original inhabitants of the New World, throughout the whole extent from Patagonia to Greenland, procured fire by rubbing pieces of hard wood against other very dry pieces, till they emitted sparks, or kindled into a flame. Some of the people to the north of California had the method of inserting a kind of pivot in the hole of a very thick plank, aud by its circular motion produced the same effect.

Instances have occurred, where whole forests have been burnt down, by fires kindled from the violent friction of the branches, against each other by the wind.

Exp. — Having a common phosphorus box, take out a small portion of its contents on the point of a brimstone match, and rub it briskly on the cork. In this case a sufficient quantity of caloric will be evolved by friction to occasion the phosphorus to burst into flame.

64. By the discharge of an electrical battery, or by the galvanic apparatus, a more intense de- gree of heat may be obtained than by any other means whatever.

By means of an electrical battery metals may be suddenly fused, and gases united, which we are unable to combine by any other mode.

Exp. 1. — If fine metallic wire be made part of a powerful galvanic circle, it will be melted in an instant, and give out the most beautiful coruscations t>f light, of various colours, ac- cording to the nature of the metal employed.

Exp. 2. — Sul>mita little gold or sdver leaf to the action of a galvanic battery : either of which will burn with great splen- dour, and afford a beautiful spectacle.

Exp. 3. — If a piece of charcoal, from hard wood, be in- flamed by galvanism, the light produced seems to vie with that of the sun, being too intense for the eye to endure.

34 CALORIC. [Ch. 3.

65. When heat is produced by the mixture of two or more substances, it is owing to the fluid part of the mixture taking a more solid form ; for neither water nor any other fluid can acquire an increase of density without giving out a portion of its latent caloric.

Whenever two gases or liquids unite chemically, the com- pound has greater density than the mean density. Thus the vapour of water, at the heat ot" ebullition, occupies much less space than the hydrogen gas and oxygen gas, which compose it, would have occupied at the same temperature.

Exit. 1.— Take a small phial about half full of cold water ; grasp it gently in the left hand, and from another phial pour a little sulphuric acid very gradually into the water. A strong sensation of heat will immediately be perceived, This, by the continued addition of the acid, may be increased to raa-' ny degrees beyond that of boiling water.

Exp. 2. — Put a little fresh calcined magnesia in a tea-cup upon the hearth, and suddenly pour over it as much concen- trated sulphuric acid as will cover the magnesia. In an in« stant sparks will be thrown out, and the mixture will be com- pletely ignited.

66. Mixture does not uniformly produce heat. The mixture of some substances pro- duces an intense cold.

Whenever suhstai.ces become more condensed by mixture, heat is evolved ; when they expand, cold is produced ; or, in other words, the compound has a greater or 1-ss capacity for caloric than the separate ingredients. The mixture of crys- tallized muriate of lime and snow produces the greatest de- gree of cold yet known.

Exp. — Take a small phial containing some pulverized mu- riate of ammonia; pour a little water upon it, and shake the mixture. In this instance a sensation of cold will be immedi- ately felt.

67. Caloric is uniform in its nature; but there exists in all bodies two portions of ca- loric, very distinct from each other.

How the same bubstai>ce may exist in a body in two distinct states, may easily be explained by the familiar example of a piece of common bread which has been dipped in water. This

Ch. 3.] caxoric. . 35

bread will contain two portions of water very distinct ; one of them is in a state of combination, and forms a constituent part of the bread ; the other is only interposed between the parti- cles of the bread, and ma» aijain be forced out by pressure.

68. The one is called sensible heat, or free caloric ; the other latent heat, or combined ca- loric.

Exp. 1 . — Wrought iron, though quite cold, contains a large portion of latent caloric; and if it be briskly hammered for some time on an an\ il, it will become red hot by the action of this species of caloric, which by the percussion of hammering is now evolved and forced out as sensible heat.

Exp. 2. — If a little sulphuric acid be mixed with about an ounce ot the strongest nitrous acid, and th>- mixture be poured into oil of turpentine, the whole will birst into flame. This is owing to the compound having less capacity tor caloric than these separate fluids. The phial containing the mixed acids should be fixed to a rod, and its contents poured :?t armslenglh and as quickly as possible upon the o<l in a cup. The cup containing the oil of turpentine should be placed in the open air, or under a large- chimney, to prevent any accident from the sudden combustion. •

69. Sensible caloric is the matter of heat dis- engaged from other bodies, or, if united, not chemically united with them.

Some writers have called the matter of heat whtn in this state interposed caloric.

70. Latent caloric is that portion of the matter of heat which makes no sensible addition to the temperature of the bodies in which it exists.

Caloric, as it penetrates bodies, frequently forms a chemical

combination with them, and become s essential to their com- position. This is always the case when a solid is converted to a liquid, or when a liquid passes to < gaseous state. But if caloric be superadded to a body when ii is in a state of satura- tion, it merely traverses its surface, ami passes from it, in the form of sensible heat, to some ot the adjacent bodies.

Exp. — If a pan of snow be hung ovei a large fire, the snow will receive a great accession of caloric from the fire without being at all sensibly warmer. The caloric, as it enters the snow, becomes chemically combined with it, and the fire will

36 CA10R1C. [CIu

not in the least alter its temperature, till the whole become fluid.

71. Caloric in a latent state exists in all sub stances that we are acquainted with.

Caloric pervades all bodies; this is not the caae with an; other substance we know of — not even light.

Whenever caloric quits its latent state, how long soever may have lain dormant and inactive, it always resumes itfc proper qualities and character, and affects the thermometer and the sense of feeling as if it had never been latent.

72. Caloric combines with different substances in very different proportions ; and for this rea- son one body is said to have a greater capacity for caloric than another.

Exp. — The propriety of this term may be shown to a pupil- by dipping a lock of wool and a piece of sponge in water, ancfc directing him to observe how much more water the sponge is capable of taking up than the wool. Hence sponge may bee said to have a greater capacity for water than wool has.

73. The same bodies have at all times th& aame capacity for caloric, unless some changer takes place in the state of those bodies.

Whenever a body changes its slate, it either combines with, or separates from, caloric.

74. When gaseous substances become liquid, or liquid substances become solid, they lose in' a great measure their capacity for caloric.

The caloric which is evolved during the slaking of quick- lime, escapes from tlie water in consequeuce of its changing from a liquid to a solid form by its union with the lime. The same effect is produced in making butter. When the cream changes from a fluid to a solid, a considerable degree of heat is produced.

Exp. 1 . — If when the air is at 22° we expose to it a quantity of water in a tallglasi, with a thermometer in it and covered, the water gradually cools down to 22* without freezing, though 10" below the freezing point. Things being in th» situation, if the water be shaken, part of it instantly freezes into a spongy mass, and the temperature of the whole rises t9

Ch. 3.] CALORIC. sr

the freezing point ; so that the water has acquired 10° of ca- loric in an instant.

Exp. 2 — If a small thermometer be placed in a glass ves- sel containing about an ounce of a solution of soda ; on adding a sufficient quantity of muriatic acid to saturate the soda, the mercury in the thermometer wili expand; affording an in- stance of heatbein . produced by the formation of a ball.

Exp. 3. — Let the last experiment be repeated with car- donate of soda, instead of pure soda ; the mercury will now sink in the thermometer. Here, though the sam-i kind of salt is formed, cold is produced. This must be attributed to the evaporation of the carbonic acid.

Evcp, 4. — Charge a small glass retort with strong muriatic acid, and insert its beak into a tubulated receiver containing u little water ; then into this receiver insert two small ther- mometers, the one immersed in the water, the other suspend- ed above it. Hv applying the beat of a lamp to the retort, muriatic acid gas will be disengaged in abundance ; and if the thermometers be examined, that which is suspended in the gas will be found to have lis n only a few degrees, while that which was immersed in the cold water has acquired a boiling beat.

75. When solid bodies become liquid or gaseous, their capacity for caloric is propor- tionately increased.

By the solution of some salts water qMJ be deprived of so large a portion of its caloric as to be frozen in the midst of summer.

/..<•/;. 1. — Disssolve five drachms of muriate of ammonia and live drachms of nitre, both finely powdered, in two ounces of water. A thermometer immersed in th< solution will show that the temperature is reduced below 32". If a ther- mometer tube, filled with water, bb now suspended within it, the wat« i will soon be effectually frozen.

Exp. 2. — Dip the hulb of a thermometer in melted rosin so as to coat the glass with it, and suffer it to cool ooraplen iv. If the flame of a taper be now applied to the bulb soa^ to melt the rosin, the mercury in th>. thermometer will not rise at tbt approach of the taper, '>ut w"ill actually be seen to con- tract as 'he rosin becomes liquid.

76. Whenever a body has its capacity for caloric thus increased, it requires a larger por-

D

38 CALORIC. [Ch. 9

lion of the matter of heat to raise it to a given $ temperature, than another body does which has a less capacity for caloric.

If equal weights of water and mercury, cooled down to the; same point, be afterwards separately heated to the heat of' boiling water, the water will be found to have required more than three times the quantity of caloric than the mercury did | to bring it to that temperature.

The difference in the capacity which different bodies have for caloric, 13 owing to one substance having a chemical affini- ty for caloric superior to that of another. See this fully ex-' plained by Dr. Henry in the fifth rolume of the Manchester JWemoirs.

Exp. — This property may be shown more readily by the following experiments. — Take I lb. of water at 100°, and mix it with 1 lb. of water heated to 200*, the mixture will be found to give the exact mean temperature of 150° ; but 1 lb. of mercury, at 100°, and 1 lb. of water at 200Q, will produce a heat much higher than the mean temperature : mercury has not therefore so great a capacity for caloric as water.

77* The portion of caloric necessary to raise a body to any given temperature is called the specific caloric of that body.

This term is always used in a comparative sense, expres- sive of the relative portions of caloric contained in equal weights or measures of different bodies at the same tempera- ture, or the comparative quantity of caloric which can pro- duce the sarae effect. Thus, if the specific caloric of mercu- ry be saif '■ to be 1 , that of water may be said to be 3, as noted in an experiment just related.

78. An instrument called a calorimeter is used for ascertaining the specific caloric of dif- ferent bodies, and comparing the relative ca- pacity of each for caloric.

The substances to be tried are heated to the same tempera- ture, and then placed in this machine surrounded with ice. By observing how much ice each of them melts in cooling down to a given point, the specific caloric which each of them contained is determined.

Ice has the property of absorbing all the caloric with which it comes in contact, and communicates no part of it to the sur-

Ch. 3.] CALORIC. 39

rounding bodies till the whole of the ice is melted ; therefore the specific caloric of bodies may easily be calculated by its means.

79. The instrument which is in common use to measure the temperature of bodies is called a thermometer.

80. The thermometer consists of a glass tube containing a portion of mercury, with a graduated plate annexed to it. The glass is usually sealed hermetically, to preserve the metal and the inside of the tube from the ac- tion of dust or moisture.

Thermometer* are made by putting mercury into small glass tabes with bulbs, and heating these bulbs till the mer- cury boils. Tbis ebullition forces out the air, and the tubes I are hermetically sealed while the mercury is boiling. They are afterwards graduated by a correct scale.

81. When a thermometer is brought in con- tact with any substance, the mercury expands or contracts till it acquires the same tempera- ture ; and the height at which the mercury then stands in the tube, indicates the exact tempe- rature of the substance to which it has been ap- plied.

Though mercury has a capacity for caloric inferior to that of many liquids, it has such an attraction for it that it absorbs sufficient to keep it in a fluid state in the common heat of our atmosphere. Owing to this affinity, it expands very readily by every addition of the matter of heat. It is also equally affected by equal increments of heat at every temperature be- tween its freezing and boiling points; which is not the case with some other fluids, such as water, ardent spirit, ice- hence it is the most proper substance for thermometers.

To measure the degrees of heat in high temperatures, Mr. Wedgwood contrived a very useful instrument, which he call- ed a pyrometer, including a range of nearly 32,000 degrees of Fahrenheit.

82. The thermometer will not show the ab-

40 CALORIC. [Ch. 3.

solute caloric in all substances ; for it cannol measure that portion which is latent, or chemi- cally combined with any body.

Every suusiauee reqiiirt s its own quantity of caloric to rais It 10 a given temperature; but when raised to that tempera- ture, every further addition of caloric is precisely shown bj the thermometer.

83. Thus fluids require a certain portion ol caloric to keep them in a state of fluidity which portion is not indicated by the thermo- meter.

£xp i .—if a quantity of snow be placed in a bason befot a fir , and a thermometer be piunge<l in it, the thermometei -will stand al 32° ; if the thermomet* r be removed, and the snow suffered to remain before the fire some time longer, anc then tried by the thermometer, it will still indicate the st«me temperature, though it has all along been i eceivmg an trees- sion of caloric ; but the moment that the -whole of the snow is melted, the thermometer will begin to rise.

Exp. 2.— IE a piece of ice cooled 20° below the freezing point be exposed to a fire with a thermometer stuck in it; thg thermometer will rise very unifornly until it comes to the freezing point 32°, and there make a tull stop till the jce lM all liquefied, as though (he fire had lost its faculty ot heating if1 but the instant that all the ice is melted the thermometer will begin to rise again, and will continue to rise gradually till the water beconv s heated to 212°, the boiling point.

84. Notwithstanding this, all fluids operate, upon the thermometer in the same manner asj solids ;- for, whatever sensible caloric be con-j tained in any liquid, that portion may be mea-j sured by the thermometer.

Exp.—U we plunge a thermometer ever so often into boiling water, it will always stand at the same point, provided the

pressure of the atmosphere be the same. Melting snow will always show th<- san.e degree upon the thermometer, in; whatever state the atmosphere may be.

85. That portion of caloric which is a neces- sary part of fluids, is called the" caloric of fluid-

Ch. 3.] CALORIC. 41

ity; but different fluids require different portions of it to preserve them in the state of fluids.

The caloric of fluidity of water is 140°. That is, water re- duced to 32° must lose 140 degrees more of caloric before it becomes ice, and still its temperature will be 32°.

Exp. 1. — If four parts of sulphuric acid and one part of ice, both at the temperature of 32Q, he mixed together, the ice melts instantly, and the temperature of the mixture rises to 212°, the heat of boiling water. But if four parts of ice and one of the same kind of acid at 32° be mixed, the temperature sinks to about — 4°. In the first of these experiments, as the ice and acid combine, they become more dense than their mean density ; consequently they bqlh give out l part of their caloric of fluidity, and retain only the caloric of fluidity which is necessary for the new compound. In the other ca -<■ , the ice, assuming a liquid form, requires a large dose of caloric to give it fluidity ; and the sudden fall of the thermometer is ow- ing to the suddenness with which the ice absorbs the caloric from the acid, and which it requires before it can become liquid.

Exp 2. — Take an emalgam of lead and mercury, and an- other amalgam of bismuth, let these two solid amalgams be mixed in a mortar by triture, and they will instantly become fluid.

86. The general effects of caloric are to in- crease the bulk of the substances with which it unites, and to render them specifically lighter than they were before; but in whatever quantity it is accumulated in bodies, it never adds to their absolute weight.

Some bodies are much more dilatable by heat than others ; thus iron is more dilatable than wood, and wood is more dila- table than a stone. Of the metals, platinum dilates the least, and lead and zinc the most, by increase of temperature.

Exp. I. — In order to be convinced that solids increase in bulk by combination with caloric, procure a piece of iron wire, of an exact length to slip lengthways within a ring, or within some metallic box ; then if the wire be heated, it will be found increased in It ngth so as not to pass through the ring or box.

Exp.2. — Fill a Florence flask with water to about the mid- dle of the neck, mark the place to which it rises, and then D 2

42 caloric. [Ch. 3.

immerse it in boiling water; when it will be seen to expand in the glass till it nearly runs over the neck of th; fia^k.

87. Caloric favours the solution of salts, and promotes the union of many substances.

Exp — If two ounces of Bulfihate of soda (Glauber's salt,) in powder, be put into a tea cup holding two ounces of cold water, the water will dissolve only a portion of it; but if a boiling heat be applied, the whole will be dissolved. If the liquor be left to cool, the salt will be seen to shoot again into ©rysfals. This little experiment will also have its use as an example of crystallization.

88. In other cases it serves to separate bo- dies already united ; so that in the hands of chemists it is the most useful and powerful agent we are acquainted with.

This is the case in distillation, whereby the most subtile parts of a compound body are dissolved b\ caloric, and sepa- rated from the mass in the state of gas or vapour. Every kind of distillation may be performed in a common retort, (see Plate I. fig. 2. and fig. 3.) with common receivers attached to it, similar to the apparatus, fig. 23, Plate VI. For strong heats' Wedgwood's retorts are preferable to glass.

Caloric promotes also the decomposition of bodies, by rea- son of its counteracting the attraction of cohesion which exists in all bodies. For a more particular explanation of the effects, of caloric in chemical processes, consult the article Repulsion in Chapter XIII.

Exp. 1. — Ice and soda have no more action on each other than soda and silica; but raise the temperature of the ice, and it unites to the soda.

Exp. 2.— Potash and silica if mixed have no action whatever on each other ; but if submitted to a great heat, the potash melts, and attracts the silica, which melts with it into a sub- stance that may be dissolved in water; or, if the silica be in proper proportion, the compound will be glass.

89. It is the cause of fluidity in all substances which are capable of becoming fluid, from the heaviest metal to the lightest gas.

Let it be remembered that ail fluids are formed from solids by an addition of caloric ; and that, by abstracting this eajoric, solids would be reproduced.

Ch. 3.] CALORIC. 43

90. It insinuates itself among their particles, and itnariably separates them in some mea- sure from each other. Thus ice is converted into water, and by a further portion of caloric into s earn.

h the temperature of steam b^ no more than that of bo •> , or '21 2°, yet it hut been demonstrated by some

ver) ingenious experiments of Mr. Watt, that it contains ne;"U 10008 more caloric ; -and that this keeps it in the form of stream.

Exp. I. — The expansion of valatile bodies by heat may be shown by the following; experiment :— Pol a little ether into a small retort, tie abUdder toth. b ik of it, and bold the re- tort over a lamp. The ether will quickly boil, and the gas which arises from it will soon oeeupj thr bladder and distend it to its full size. If the bladder be then held in wal . 'lie gas will be condensed by the loss of its heat, and the bladder

[will collapse. In order for this experiment to succeed, it is necessary previously to warm tin* bladder to 80 or 90 degrees,

| to prevent the gas from b. ins: condensed in the fii st instance. Exp 2. — Fill a small oil flask with any kind of coloured

I water, having previously put in a few tea-spoonful of ether : then invert the flask in a shallow vessel of the same kind of co- loured water, and by degrees pour boiling water upon its bulb.

IBy the sudden accession of heat the « ther will be changed

'into vapour; which will fore* f>wt the coloured water, and fill the whole of the vessel. If cold water b' now poured on the

■flask, th« vapour will be condensed, and the coloured water

i^vill again rise within it.

91. We have reason to believe that every I solid substance on the face of the erfrth might be converted to a fluid, or even to a vapour or ia gas, where it submitted to the action of a very high temperature in peculiar circumstances.

Sir James Hall has succeeded in fusing chalk, limestone, marble, and even common coal, by means of a pressure suffi- ciently strong to prevent the escape of the more volatile parts of the substances which he submitted to the experiment.

When a very intense beat is required, it is sometimes pro- cured by collecting the sun's rays by means of a double con- vex lens, or a concave mirror.

44 CALORIC. [Cll. 5.

92. Calorific rays, or rays which elicit calo-f ric, are transmitted to us from the sun accom-" panied with light : these are perpetually thrown off from that immense body with astonishing velocity, in every direction.

Whether caloric itself is in any degree transmitted from the son, is now considered to be extremely doubtful. See Note, No. 60.

Since the discoveries of Dr. Herschel, Ave have reason to believe the sun to he an opaque body, probably a habitable world ; and that the light and heat we receive from it are ow- ing to an atmosphere which it has, of elastic fluids of a phos- phorescent nature, by the decomposition of which, light is evolved, and heat produced in the planetary bodies.

93. As caloric passes with such velocity from the sun, it would never be retained by those substances which receive it, were it not for its affinity for those bodies, or rather their mutual affinity for each other.

Caloric (like light) moves at the rate of 200,000 miles in a second ; therefore it never could be accumulated in any body, ■were it not retained by its affinity for that body, but would pass through it with the rapidity oflightning.

The rays of the sun seem to afford heat, only when they meet "with an opaque substance, and not when they pass through a transparent one, as air or water ; or when they are I reflected by a white or polished one. The air is not heated immediately by the rays of the sun passing through it; but on their meeting with an opaque body, as the earth for instance, heat is elicited, and is thence gradually communicated to the i surrounding atmosphere. Hence, the further we remove from the earth's surface the greater is the degree of cold.

94. The chemical affinity of bodies for calo- ric, is notwithstanding one of the weakest of all known affinities.

It is worthy of remark, that this was wisely and kindly or- dered by the Creator ; for, owing to this, organized bodies have no difficulty in separating a sufficient quantity of caloric from the substances around them, and of securing to them- selves the quantity necessary for their wants. It is obvious

ph. 3.] calori*. 45

Jiow dreadful would have been the consequence, if caloric had •had as strong an affinity for bodies, -is some simple substances have for each other. A small deviation from the pn sent or- |der of things would probably occasion infinite mischief.

95. This is evident from the facility with which heated bodies part with their caloric to all surrounding bodies.

The facility with which calorie passes from one body to another ma) be owing to the re pulsion which is known to ex- ist among; tin' particles of caloric. This repulsion gives it a [tendency to fly oft' in every direction.

96. It is one of the laws of nature, that heated bodies should give out part of their free caloric (to the neighbouring bodies at a lower tempe- rature, till the whole become of an equal tie* gree of temperature.

Watei however affords a curious exception to this law of jjnature ; this fluid having a ven Blight tendency to conduct ca- plorjc downwards-. Had it b. en otherwise, thr ocean . nd Other large bodies of water would have opt rated very unfa- vourably on the temperature of the atmosphere. ! JEpcp. 1. — Take a gla;js of cold water, pour a litdp stdphu- jric ether upon its surface, and inflame ii by a slip of lighted The ether will bit- n tor it considerublt brae and pro- duct- a large volume of flame, bur when extinguished the wal ! will b»- found not to have, increased in temperature. [The design of this exp. rim< nt is to show th:.i water is a bad rcObduclor ol ealo ic, and that when we wish to heat water, the heal ought not to !j,j applied at its surface.

Some bodies give '>ut their superabundant caloric much sooner than others Iron is a quicker conductor of caloric thati glass, and glass is a better conductor than wood. Hence the us<- of wooden bandies to metallic tea-pots and other uten- sils.

Ex[>. 2. — I take a piece of iron in one hand, and a piece of wood ^ the other ; the iron feels cold, the wood warmer, though the thermometer shows that their temperature is tb-j same. How is this? The iron has a stronger alfimu lore* loric than wood, and conducts it from the bund much swifter than the wood, and hence gives me a more livejv sense of •old.

46 caloric, [Clu 3*|

97. Thus, wnen the temperature of the at- mosphere is reduced below 32°, water gives out its superabundant caloric by degrees, till at length the cold atmosphere robs it of its ca- loric of fluidity also, and it becomes ice.

The quantity of heaf given out in freezing, occasions the progress of congelation to be extremely slow. The constant emission of caioiic from the freezing substances operates fa- vourably ; for thus the severity ot the frost is mitigated, and I its progress retarded. This accounts for its often feeling "warmer after a great fall of snow.

98. By this change the ice becomes speci- fically lighter than the subjacent water, and is thus enabled to swim upon its surface.

Ice is lighter than water, owiig to air bebbles produced in the ice while freezing: but Monsieur de Mairan attributes the increase in the bulk ot water in freezing to a different ar-£ range ment of its particles: ice being a crystallization com-; posed of filaments, which are found to be uniformly joined aty an angle of 60°, and by this disposition occupy a greater vo- lume than if they were parallel.

Exp. 1. — Drop small pieces ot ice into a tall glass full of hot water ; as the ice melts, bubbles of air will be seen to rise from it, and burst at the surface of the water.

Exp. 2. — If hot water be poured into a glass jar of cold wa- ter, it will remain on the surface ; but if cold water be pour- ed upon hot water, it will sink to the bottom of the vessel. This experiment may be rendered more obvious by colour- ing tiiat portion of the water which is poured in. The design of this experiment is to show the change of the specific gravity of the same body, merely by the agency of caloric,

Exp. 3. — Fill a thermometer tube with tepid water, and immerse it in a glass vessel of water of the same temperature, coniaining a mercurial thermometer. If the whole be now placed in a bed of snow, or in a frigorific mixture, the water in the tube will suffer a progressive diminution of volume, un- til it arrives at about 40° ; it will then begin to expand gra- dually, until it becomes solid. This shows how ice is enabled to swim on the surface of water.

Exp 4. — Another example on this subject may be shown. Fill a thermometer tube with cold water, at about 32°, and immerse it in a vessel of warm water. In this case, the

?h. 4.] WATER, 47

ater in the tube will contract in volume till it arrives at about 2°, when it will appear for a time nearly stationary. If the leat be now continued, the effect will be reversed, for the vater, in the tube will expand as its temperature is increased. This is a curious instance of a chemical anomaly.

99. Substances usually become more dense )j the loss of caloric ; but the freezing of water s a striking exception to this general law of mature, and is a memorable instance of the .visdom and provident care of the Almighty, ♦vhen he established the laws of the universe.

In general, all bodies, whether solid orfluid, contract their •limensions and become of more specific gravity in cooling ; aut -water affords a remarkable and striking exception. Wa- ter as it cools below 42°. 5, instead of contracting and becom- ng of greater specific gravity, actually becomes increased in pulk, and its specific gravity contiuues to lessen as it cools, flow admirable the wisdom, how skilful the contrivance, that, 'jy subjecting water to a law contrary to what is observed by ither fluids, the water .as it freezes becomes specifically light- er, and, swimming upon the surface, performs an important jervioe by preserving a vast body of caloric in the subjacent fluid from the effects of the surrounding cold, ready to receive Its own accustomed quantity upon the first change of the at- nosphere !

CHAPTER IV.

OF WATER.

160. Water is a compound consisting of lydrogen and oxygen.

Water was always considered to be a simple substance, and :hemical philosophers were for a long time unwilling to allow if its being otherwise. Its compound naturs was however ully proved, in the year 1784, bv Mr. Cavendish.

101. It is found in four states, viz. solid or

*8 WATER. [Ch. 4«

ice; liquid or water; vapour or steam ; and ir£ a state of composition with other bodies.

Water is said to be in a state of* composition with other bo*i dies, because in many cases it becomes fine of their component; parts and unites with them only in a definite proportion. Bfi this union it occasions the transparency of" crystallized saltjfl and in other cases it unites with bodies, and forms what are(f called hydrates

Exp. 1. — Take an ounce of sulphate of soda in dry pow-# der, dissolve this in as small a portion of hot water as is neees4 sary for its solution. If it be then suffered to remain at rest until the solution is perfectly cold, crystals of sulphate ofsoda^ will be. found in the vessel. On weighing thes^ crystals ifl will be perceived that the ounce of dry sulphate of soda has produced more than two ounces of the crystals of that saltJ The water, which is thus become united with the salt, i*( known by the name of the -water of crystallization.

Exp. 2. — If a little fresh burnt lime be carefully slacked with water and suffered to remain until the whole becomes a perfectly dry powder, and then weighed, it will be found that, even 100 grains of the lime have united with 'more than thirty, grains of water. This dry compound is called a hydrate of lime.

102 The most simple state of water is that of ice.

103. The difference between liquid water and ice, is merely that water contains a large** portion of caloric. '

Exp — Take (my quantity by weight of ice or snow at 32°, and mix it with an equal weight of water heat- d exaeth to 172°. The snow instantly Kit-Its, and the temperature of the mixture is stil! onlv at thiity-t'wo degrees. Here the waff is cooled 140° while the temperature of the snow is not ii creased at all ; so that 140° of caloric have disappeared There can be nodonbt, then, but water owes it? fluidity to its lateut calorie. See Exp. 1, at No. 85.

104. Vapour is water combined with a still greater quantity of caloric.

Howevei lo; g «e boil a fluni in an opi- n vessel, we CMnof make it in the smallest degree hotter than its boiling point.

:!1C

c

pi. 4.]

WATER. 49

Ij-Vhon arrived at this point, the vapour absorbs the heat, and arries it off as fast as it is generated.

Exp. — Those who have an air-pump may easily see that /ater requires a vast portion of caloric to convert it into team ; for, if a cup of hot water be put under the receiver, nd the pump be set to work, the water1 will soon begin to oil furiouslv, and the receiver v. ill be covered with vapour, f the receiver be now taken off, the Wnter will be found aivly lukewarm, owing to the vapour having carried off the ;i( at. st part of its heat.

105. Owing to the large quantity of caloric hat liquids require to convert them into va- lour, all evaporation produces cold.

! An animal might be frozen to death in the midst of sum- mer, by repeatedly sprinkling ether upon him. Its evapora- lion would shortly carry off the whole of his vital heat. Wa- fer thrown on hot bodies acts in the same way ; it becomes, in fn instant, converted into vapour, and thus deprives these pfties of a great portion of tlie caloric they contain. 8 Exp. 1. — Take a glass thermometer tube, fill it with cold water, and suspend it .by a string If the bulb be frequently

»nd eontinuall) moistened with pure sulphuric ether, tlie wa-

er will presently be frozen, even in summer. I Exp. 2. — If the student be in possession of an air-pump, the following experiment may be easily performed : — Let him

ix a small tin cup of 'ether within a large watch-glass contain- ,ng a little water, and place both under the receiver of the Mr-pump. The exhaustion of the receiver will cause one of [he fluids to boil, and the other to freeze at the same instant.

106. Vapour, owing to the large quantity of [caloric which is combined with it, takes a gase-

Ipus form, and acquires great expansive force.

Water, in ot utti converted into vapour, combines with I, more than fives times the quantity of caloric that is required

(•to bring ice-cold water to a boiling heat, and occupies a space S00 times greater than it does when in the form of water. I The expansive force of steam is found by experiment to t <e much greater than that of gunpowder. Some volcanio I 'eruptions and earthquakes, it is supposed, owe their terrible I effcis to this power of steam: the water of the sea finding its J way to subt i raneous fi.»s.

1107. These properties of steam render it ca- E

[Ch. 4.

weights, and of rerful agent for nd for other im/l

was a vast acquisition iWe that, in time, steam, il purposes of which at presenfl we have no1 lffea'. lu America, vessels have long been navi- gated by steam, and of late years such vessels have become very common in several districts of Great Britain.

108. Water is composed of 88 parts by; weight of oxygen, and 12 of hydrogen, in every 100 parts of the fluid.

Both these terms are derived from the Greek language; the former signifies to generate acids, the latter to generate'' ■water.

Water is found to be a compound of 1 part hydrogen and 7£ parts oxygen by weight : this will give, in the 100 parts, the proportions of nearly 11 ^ of hydrogen and 88£ of oxygen. If the gases are estimated by their volume, water will be found to be composed of two measures of hydrogen and one, oi oxygen.

Exp. — Put a little alcohol in a tea-cup, set it on fire, and invert a large bell glass over it. In a short time an aqueous vapour will be seen to condense upon the inside of the bell, which by mea»s of a dry sponge niay be collected, and will be found to be pur water.

109. Several methods have been contrived, whereby water may be decomposed, and the exact proportion of its constituent parts ascer- tained.

This was discovered by Mr. Cavendish, in the vear 1781. Dr. Priestley h*d previously combined the two gases by com- bustion; but Mr. Cavendish was the first who drew the pro- per conclusion fi om the Doctor's experiment

110. It may be done by forcing it through a tube over red-hot charcoal, by passing re- peated electrical shocks through it, and also by means of the galvanic apparatus.

?A. 4.] WATER. 51

"Water cannot be decomposed without a combustible bo- v," or th" agency of elecficity or galvanism, '■ as i lie hy- rogen requires a very large dose of calorie to put it in a aseous state. This t.ppears Irom the lightness ol bydr< u^n as compared with water. A cubic fool of water weighs C)lZ^ ounds, whereas a cubic fool oJ hydrogen gas weighs less lan 40 grains."

Exp — When Iwo wires from the opposite extremities of a alvanic battery are placed in a tube cont lining wat«r, so lhat icy asv distant from each other £ or ^ an inch, a stream of as issues from each wire — from the positive wire oxygen, x>m the negative, hydrogen gas ; and these are in the.pro- ortions which when exploded, either by galv.nism or elec- 'icity, i" -form water.

111. Nature also decomposes water in many f her operations, particularly by means of very living vegetable.

Sei Axiom 35, and tli<- Notes.

112. Likewise fish in general, and all cold- looded amphibious animals, we have reason to

think, are endowed with the same faculty of de- composing water.

i Ahjongntli r cases, we read of a fish that was kept three fears in h vessel and fed only with water, and that at last it jecame too large to live any longer in the vessel. Whence • his increase of animal substance, if we deny it the power of Decomposing w«t< r P Rondelet de PUcibus. lib. i. cap. 12.

'f 113. Vegetables, in decomposing water, com- fcjine part of its hydrogen, as well as of its oxy- igen, with the carbon of the atmosphere and of ithe soil, to form the vegetable compounds oil, wax, gum, resin, sugar, &c. ; while the super- fluous oxygen is abundantly evolved by the leaves.

I li should always be recollected that the oil found in vege- tables is produced by this process of vegetation. Tin oils, bitumens, Sec. in minerals, must all have had a vegetable origm. )\\ China, vegetable wax is extracted from plants by mace-

5% WATEK. [Ch. 4,

ration in boiling water, and employed in the manufacture of candles.

Bees* ' xvux is doubtless a vegetable product. The bees extract it unaltered from the leaves of trees and other vege- tables.

114. Oxygen is the basis of vital air, as well as one of the constituent parts of water ; it is ; the chief support of life and heat; and performs* an important part in most of the changes whicra take place in the mineral, vegetable, and animal' kingdoms.

iv.ture, in economising the primary materials of the uni-' rerse, has constituted oxygen the basis both uf the atmosphere which surrounds ihe earth, and ot the water which forms itfr seas and oceans :

" For mark how oxygen with azote gas Plays round the globe in one aerial mass, Or, fused with hydrogen in ceaseless flow, Forms the wide waves which foam and roll below."

115. Hydrogen, the other constituent part of water, is the base of the gas which was former- ly called inflammable air, and is, when in aeri- form state, the lightest of all ponderable things.

Hydrogen gas, from its great levity, has generally b< en used to fill air-balloons. This gas can be procured pure only from water, which in ail cases must suffer a decomposition. See a further account of hydrogen and its compounds iu-i chap. xi.

Exp. — Put a quantity of filings of zinc into a vessel which has a glass tube adapted to it ; then pour upon them sulphuric acid diluted with 6 or 8 times its quantity of water ; an efFer. vescence will immediately take place, the water will be de- composed, the oxygen of it will become united to the metal, and the hydrogen gas will be disengaged, and maybe con- veyed by the glass tube into any proper receiver.

116. Several methods have been discovered of forming water artificially by a mixture of oxygen and hydrogen, so that the composition

Jk. 4.]

WATER. 53

}f this fluid is now ascertained beyond all loubt.

Exp. 1. — Add gradually one ounce of sulphuric acid to

"our ounces of water in a huge phial containing a few ir<»n

filings. The temperature of the mixture will be so much

.raised by itie union of the water with the acid, as to enable

l,he iron to decompose a part of (he water. If a hole be neatly

made through a cork which fits the mouth of the phial, and a

)iece of tobacco-pipe with a very small orifice be fitted into

t, and the whole cemented into the phial with a mixture of

esin and bees' wax, the hydrogen gas as it is separated from

■ the water will pass in a continued stream through the pipe,

• <uid may be set on fire by the flame of a candle brought iti

•contact with it.

. Exp. '2. — That water may be re-formed by the combus- i tion of this gas, may be shown by holding a glass bell over the I flame of the gas : as the hydrogen burns, ii unites with the J oxygen of the atmosphere, and the anion of the two gases pro- duces water, which will soon be seen to deposit "uselt like I dew on the inside of the ^lass. It is advisable to fold a cloth 1 round the bottle to prevent any injury from the fragments of J glass, in case of an explosion, -which sometimes iviLl happen j during this experiment , if atmosplienc air be left in lite phial;

I .or let the gas burn for a moment, before the cork and pipe are

I I fixed into the neck of the bottle.

11T. Thus, if a mixture of oxygen and hy- drogen gases, in proper proportion, be tired, the inflammation will unite the bases of the two leases, without separating the whole of their ca- iloric, and water will be the product.

M. Hint Iras Uieeeeded in forming water from hydrogen and

•oxygen, by compression only, independently of the electric

" sp rk. The compression, "by bringing the particles of gas into

intimate union, makes them throw out heat sufficient to set the

• hydrogen on fire ; and the product of the combustion is wat;r.

118. It is even probable that the torrents of rain which generally accompany thunder storms, ' may arise trom a sudden combustion of hydro- gen and oxygen gases.

This combustion is piobably occasioned by lightning. The aurora borealis may be owing to the existence of a

e2

54 WATER. [Ch. 4.

stratum of hydrogen gas in the higher regions of the atmo- sphere. The volgar entertain strange conceits about this cu- rious phenomenon of nature.

i

119. Hydrogen gas is only one fourteenth o the weight of atmospheric air, and occupies space fifteen hundred times greater than it pos sessed in its aqueous combination.

120. Hydrogen is continually emanating from vegetable and animal matters during their de- cay, and is a certain consequence of their putre- faction ; it is also evolved from various mines, volcanoes, and other natural sources.

The ignis fatuus, or will-o-wisp. originates from decayed vegetables, ami the decomposition of pyritic coals; it consists . generally of hydrogen combined with carbon; and, perhaps, occasionally with phosphorus or sulphur.

121. A wine-pint measure of water weighs I rather more than one pound ; and a cubic foot of water weighs about 1000 ounces, or 62| lbs. avoirdupois.

It is very necessary for the student to bear in mind the spe- cific gravity of water, because this is always taken for n.ity in the measure of the specific gravit) of every other substance. An accurate wine-pint holds 7272 grams of distilled water, which is 272 grains more than one pound avoirdupois.

According to the last experiments of Sir George Shuck-' burgh, when the barometer is at 30 inches and the thermo-' meter between 50° and 60°, water is 825 times heavier than atmospheric air.

122. The atmosphere, when its temperature is sufficiently low, deprives the water of a cer-. tain portion of its caloric ; crystallisation then ensues, and the water solidifies and becomes ice.

Water in freezing crystallises in filaments, which are uni- formly jomed at angles of 60 and 120 degrees. The word crystal originally signified ice.

It is owing to the expansion of water in freezing, that rocks

Vh. 4.] WATER. O.

uid trees are often split during intense frosts. According to the calculations of the Florentine academicians, a spherule, Dr little globe of water, only one inch in diameter, expands in freezing with a force superior to the resistance of 13| tons

?ight.

It may be remarked, that though fresh water freezes when reduced to the temperature of 32°, sea water does not freeze II cooled down to 28.5°.

123. By crystallisation is understood the concretion of certain substances into regular forrus, occasioned by the loss of a portion of their caloric ; but the term is generally applied to compound bodies of the saline kind, and to their separation in regular and peculiar figures,

Ifrom the water in which they were dissolved. 124. Near the poles water is eternally solid : there it is similar to the hardest rocks, and may be formed by the chisel of the statuary, like stone.

N< i>r Hudson's Bay there are islands of ice which are im- .mersed above 100 fathoms beneath the surface of the sea, and which measure three or four miles in circumference.

" There can be no doubt but that the quantity of ice at the ! north pole is the principal source of the coldness of our win- ters, which is occasioned by the regious of air blowing from ft he north al that season."

" Where, for relentless months, continual night

Holds o'er the glittering waste her start) reign." "It is related that at 'he whimsical marriage of Prince ' Gallitzin, in 1739, the Russians applied ice to the same pur- ' poses as Stone A house consisting of two apartments was ; built with large blocks of ice; even the furniture of the rooms i was made with ice ; and the icy cannon, which were fired in i honour of the day, performed their office more than once ! without bursting."

125. The great solidity of ice at the poles is

i occasioned by the very low temperature of the

circumambient air ; for in very cold countries

56 water. [Ch. 4.n

ice may be ground as fine as to be blown away by the wind, and will still be ice.

We need not look tor an) cause for the conversion of water into ice, but the loss of its caloric ; for in the Grotto of Besan-jB con water is frozen during the heats of summer. In this sin- I gular place the variation of the thermometer between winter and summer is very inconsiderable.

126. Water becomes still more solid in the'^ composition called mortar and in cements, having parted with more of its caloric in that' ; combination than it does in the act of freezing."

Though water takes a solid form in its various cornbina-'W tions, such as with lime and saline crystals, it was thought im-'s 4 possible to compress it when in a fluid state. The Fioren-julJ tine academicians filled a globe of gold perfectly full of water, . and submitted it to a very powerful press ; but could not. per-" ] ceive that they were able to make it occupy less space than j it did at first. They gave it such a degree of pressure, that at length the water exuded through the pores of the metal. I

127. Water is also combined in a state of solidity in marble, in crystals, in spars, in gems, and in many alkaline, earthy and metal-- lie salts, both natural and artificial, to all of which substances it imparts hardness, and to. most of them transparency.

Most stones and salts lose their solidity and transparency by being deprived even of a part only of the water which they' contained, and generally become pulverulent.

If water be thrown on quicklime, it will be retained by it with such force that nothing less than an intense red heat will separate it. Saussure has proved that alumina, when mixed with water, retains a tenth of its weight of that fluid at a heat which would melt iron.

Exp. 1. — Take some ground plaster of Paris, fresh calcined, anil mix it up with a little water. The affinity of the plaster for the water is so great, that in a few minutes the whole of this pulverulent matter will be converted to a solid.

Exp. 2.— 'Boil a few copper filings in concentrated sulphu- ric acid to which a small portion of nitric acid has been added,

%. 5.]

THE EARTHS. . 57

»nd when the copper is dissolved dilute the mixture with ittle water, and then lew it where it can cool gradually. If the mixture be thus suffered to remain undisturbed a few iouis, beautiful crystals of blue vitriol will be found at the Dottom of the vessel, as hard as some minerals. It is the wa- er which gives them their solidity.

CHAPTER V.

OF THE EARTHS.

128. The earths are incombustible bodies, md in general are unalterable in the fire, mil lately they were thought to be unsuscep- tible of decomposition ; they are insoluble in. water, or nearly so, when combined with car- bonic acid ; and are of a specific gravity never exceeding five times that of water.

Baron Born, many years ago, was ot opinion that the earths were compound bodies. Sir H. Davy has now succeeded in decomposing most of them ; and from his experiments we have reason to suspect that they are all metallic oxides.

The insolubility of the earths in water, when combined with carbonic acid, forms a striking distinction betwe n (his slass of bodies and the carbonated fixed alkalies, which are Tery soluble in water.

129. There are nine distinct earths known at present, viz. silica, alumina, zirconia, glu- cina, yttria, barvtes, strontites, lime, and mag- nesia.

i Notwithstanding the varied appearance of the earth under 'ourfeet, of that of the furrows of the field, and of the moun- tainous parts of the world, whose diversified strata present to 'our view substances of every texture and of every shade, the i whole iscomposed of only nine primitive earths ; and as three of these occur but seldom, the variety which is produced by •the other six becomes the more remarkable.

58 .THE EARTHS. [Ch. 5.$?

To give a still greater variety to the works nf Nature, these / earths are endowed with an affinity for acids and metallic oxides, whence arise the spars, gems, and precious stouts, of' every colour and every species.

Besidfs the nine earths here enumerated, we have now thorina, which is a rare earthy substance, lately discovered by Berzelius in a species of gadolinite. Its properties are at. present but little known, jet it is presumed to be, like the I other earths, a metallic oxide.

130. Barytes, strontites, and lime, are call« ed alkaline earths, because they agree with the i alkalies in taste, causticity, solubility in water, and in their effect upon vegetable colours! Magnesia agrees with the alkalies in the latter | property only.

Baryt' s. strontites, lime, and magnesia, are found in nature, always combined with acids None of the combinations are] very hard, as either of them may be scratched with a knife." The acids, which are found united by nature with these alka- line earths, are generally the carbonic, the sulphuric, the fluoric, the boi acic, and the phosphoric.

131. Silica, or pure flint, is a white, inodo- rous and insipid earth ; it is insoluble in waterj and in every acid except the fluoric ; it en-) dures the strongest heat without alteration;, but, when mixed with soda or potash, becomes fusible in a strong fire into glass. Its specific gravity is 2.65.

Some properties that are common to all the earths, do not pertain to silica; among others, it has no attraction whoever for carbonic acid, nor does it form a regular suit with any other acid.

Sir H. Davy has not yet succeeded in exhibiting the base of this earth in a separate state, though from the result ot his experiments there is great reason to believe that silica, like the other earths, is a metallic oxide. Elem. Chem. Plu~ los. part i. page 362.

132. Silica is found in almost all solid mi- neral substances, particularly in gravel, sand,

[Ch. 5. THE EARTHS. 59

quartz, and flint, of which it forms nearly the whole substance. It is also the chief ingre- dient of those rocks which constitute the most bulky material of the solid parts of our globe.

Pure silica may be procured for chemical experiment, by fusing common fli'it stones with three or four times their -weight of potash, dissolving the product in water, and then akhg up the alkali by the addition of an acid, which will jrecipitate the silica, which is to be well Washed for use. The siliceous ston< s should be previously heated red in a cru- bK and plunged in that state into cold water. This will render them brittle, so that the> may easily be reduced to powder before they are mixed with the potash.

There is a granite mountain, about 30 miles from the Cape of Good Hope, which rises out of th*" ground to the height ot 400 feet, is half a mile in circumference, and is formed of a single block of granite.

133. Silica has such various uses in the arts, that it is one of the most valuable earths that

jwe are acquainted with.

134. It is the most durable article in the »state of gravel for the formation of roads ; it is u necessary ingredient in earth ern- ware, porce- lain, and cements ; is the basis of glass, and of all vitreous substances ; and is an indispensable Article in many of our chemical furnaces and Utensils.

The manufacture of glass wns known very early ; but glass (perfectly transparent was reckoned so valuable, that Nero is said to have given a sum equal to 50,000/. for two glass cups with handles.

The manufacturing rf pastes, or artificial gems, is a branch [of the art of glass-making. The basis of these is a v.-ry hard and pure silica, obtained by melting pounded quartz with an lkali, with the addition of br rax, nitre, and oxide of lead, ifferent metallic oxides being added to imitate the colour of the different gems.

135. In making glass, silica is the chief in- gredient. It is rendered fusible by a due mix

60 THE EARTHS. [Ch. M

ture of alkali, which acts as a flux to the silica, and renders the whole transparent.

Glass cannot be made without great heat, as the alkali re- tains the last portions of carbonic acid and water with singu- lar obstinacy, and it is only at a very high temperature that the alkali fuses, and then it prefe'.s the silica ; for it is one of the laws of nature, (to which there are few exceptions) that,** in order that two bodies may become chemically united, on of them must be in a state of fluidity.

136. Alumina, or pure clay, is an earl whose specific gravity is 2.0.

Pure alumina may be procured by decomposing commc alum with carbonate of ammonia. It has notb<-en found na tive in a state of purity any where, except at Halle in Ger many.

137. This earth is soft to the touch ; adhe- sive to the tongue ; emits a peculiar odour when moistened ; forms a paste with water ; has great affinity for colouring matter ; will unite with most acids ; and acquires a great hardness, an$ contracts in the fire. Like silica, it is soluble in caustic potash, or soda.

Common clay is a mixture or alumina and silica. It fre* quently contains metallic oxides, chalk, and other earths. Alumina united to the oxides of iron is plentifully procured, in Staffordshire and Derbyshire; in which state it is culled* raddle, an article v ry useful in colour-making. FuilerY earth is alumina combined with very fine silica.

138. Alumina is distributed over the face of the earth in the form of clay, and from this cir- cumstance acquired the name of argil.

139. It is found also in a state of crystallisa- tion in the sapphire, and other precious stones, i and is united to the oxides of iron in the ochres. It obtained the name of alumina from its being i the base of the salt called alum.

140. Alumina, on account of its aptitude for

Ck. 5. THE EARTHS. 61

moulding into different forms, and its property )f hardening in the fire, is employed in various ways, such as for making bricks, crucibles, &c; >ut the alumina which is made use of for these urposes is always impure.

141. Aluminous earth is employed for vari- >us purposes by the dyer and the calico printer,

specially in its combination with acetic acid is a mordant for fixing madder reds and some ,)ther colours on calico ; and upon the continent .t is artificially combined with sulphuric acid, In order to form alum.

. In England it is not necessary to form alum by art, as the .ilum-slate is found in great abundance, and it is only requi- site to add potash, ammonia, or salts containing either of these pases, in order to complete the process.

Exp. — If a little fustic, querciton hark, or other dve, be 30iled in water, the colouring matter will be extracted, and a colcured solution formed. On adding a small quantity of iissolved alum to this decoction, the alumina, or base of the ka\t, will attract the colourmg matter, forming an insoluble jompound, which in a short time will subside, and may easily pe separated.

142. Alumina, mixed with silica, is used by £he potter in the manufacture of porcelain and earthern-ware.

, Earthenware, according to the Old Testament, was known lat an early period to the Jews ; and the potter's wheel, there Ispoken of, was probably the same simple machine as is used ■at the present day to form round vessels with plain sur- faces.

Alumina is of inestimable value for securing the bottoms •and sides of canals and reservoirs of water, and composes (in a great measure those tenacious earihs called arable soils.

143. In making earthen-ware a due propor- tion of both these earths is necessary ; for if

i alumina alone were used, the ware could not f be sufficiently burnt without shrinking too much,

r

62 THE EARTHS. [C'A. 5.

and even cracking ; and a great excess of si- lica would lessen the tenacity, and render the ware brittle.

144. Stone-ware, like other pottery, is chief- ly composed of alumina and silica, but a cer-' tain quantity of old pottery finely ground ig generally introduced into its composition. The difference, however, between this and common earthen-ware, chiefly consists in the burnin and glazing ; stone-ware being always submi ted to a much higher degree of heat, and in i being glazed with muriate of soda instead the oxide of lead.

145. On account of the superior strength oi stone-ware, its very compact texture, and the wholesome nature of its glaze, it is greatly to be wished that its use were considerably ex- tended, and that every article for culinary pur-* poses were to be manufactured with it.

146. Porcelain is not esteemed good, unless it be very compact, quite white, and semitrans- parent; indeed, it is chiefly the last quantity that constitutes the principal difference be- tween earthern-ware and porcelain, for earthen- ware is always opaque.

147. Barytes occurs chiefly in combination with sulphuric acid ; it wa« first discovered by Scheele in a mineral called ponderous spar, af- terwards terra ponderosa. It is chiefly found in this state in England, and in other parts of the globe. In Derbyshire it is known by the popular name of cauk.

Barytes is always found united either with the sulphuric or the carbonic acid.

]Ch. 5. THE EARTHS. 63

Bergman gave it the name of barytes from the Greek word farys {heavy ,) thisbeingthe most ponderous of all substances jxcept the metals and the earth called yttria.

Exp. — Dissolve the Carbonate of barytes in very weak ni- rousacid,by which meatus the carbonic acid will be expc lied, jnd then in the usual way, by proper evaporation, i ratals of Utrate of barytes will be formed. By exposing this salt to a trong heat, the nitric acid will be dissipated, aud pure bary- 2S will be procured.

148. It has also been fouud, combined with arbonic acid, in several parts of the British empire, particularly in Northumberland, Cum- berland, and Lancashire : and in France, in combination with the oxide of manganese. : 149. Barytes when pure is of a greyish white bolour; like the alkalies it changes the vege- table blues to a green ; has a pungent caustic kste ; has the property of enabling oil to unite kith water ; and is in all its combinations, ex- cepting that of the sulphuric acid, a violent poi- son.

1 Pure barytes changes quickly when exposed to the air ; it swells like quick-lime, and like it falls into a white powder ; .butthis slacking is much more violent and speedy than that of lime. It combines intimately with water, and the water, becomes solidified in the barytic earth.

150. Barytes is a non-conductor of electri- city ; and may be known from the other earths by its solubility in water, by its forming an in- soluble compound with sulphuric acid, and by its imparting to feme a yellow colour. Its spe- cific gravity is 4.90.

Barytes is soluble in about 20 parts of water at the tempe- .tureot'60°; but boiling water will dissolve half its weight f this earth, part of which will crystallise on cooling. The most singular property of this earth is the tenacity ith which itholds the sulphuric acid when combined with it, It has such an affinity to it, that it will not part with it even

64 THE EARTHS. [Ch, 5.

to pure alkalies. The solution of this earth in water, ai in various acids, furnishes excellent tests for chemical ana lysis.

Exp. 1. — Into a solution of pure barytes pour some sol tion of sulphate of soda, both solutions being previously clea and transparent. The barytes will instantly quit the watei and attach itself to the sulphuric acid. Pure soda will noi remain in the supernatant liquor, aud sulphate of barytes b deposited in a white powder.

Exp. 2. — Prepare two glasses of pure water, and into one' of them drop a single drop of sulphuric acid, and mix it with the water. Pour a little muriate of barytes into the other glass, and no change will be perceived : pour some of the same solution into the first glass, containing the sulphuric acid, and a white precipitate of sulphate of barytes, will be produced.

Exp. 3 — Prepare two glasses of water as before, conduct i the experiment in the same way as the last, but instead o i muriate of barytes use nitrate of lead. In this case sulphate of lead will bf precipitated.

Exp. 4. — If a spoonful of good alcohol and a little pure ba rytes be stirred togeth r in a tea-cup, and then set on fire, brilliant yellow flame will be produced.

151. Barytes forms some of the most usefi chemical tests, whether in its pure state, dis- solved in water, or combined with particular! acids. It is capable of making a very tenacious cement, but has not yet been used much in the arts, except by limners as a most excellent wa- ter colour.

This is the only -white for water painting that never changes,

152. Strontites was discovered by Dr. Hope about the year 1791, in a mineral brought from the lead-mine of Strontian in Argyleshire. That mineral, which is a ca ■••' on ate of stronti- tes, has been found but in small quantities in any other place.

It will be advisable for the preceptor to procure specimens of this and other minerals, that the pupils may learn how to

Ch. 5. THE EARTHS. 6a

istingui9h them. It will also serve to give a variety to the essons, and prevent sati* ty.

153. Strontites is more abundantly produced y Nature, when in union with sulphuric acid; articularly near Bristol, where it is in such uantity as to be employed in the repairs of

e neighbouring roads.

154. Strontites, when separated from its kcid, is considered to be a pure earth, and like Wytes, is then soluble in water; it is of a grey- sh white colour; its taste is acrid and alka- ine, but less so than barytes or the alkalies.

In order to procure this earth in a state of purity, carbonate hf strontites may be treated in the same way as carbonate of parytes is treated, to procure pure barytes.

155. The solution of this earth in water is capable of crystallisation. It is distinguished Irom barytes chiefly in not being poisonous, and also in giving a purple colour to flame.

' Stroulites is not soluole in less than 200 pans of cold wa- ter; hot water dissolves it much easier; it then crystallises .Dn cooling, and is similar to barytes in many of its habitudes. Exp. — Mix a spoonful ot goo<l alcohol with a little pow- dered slrontian, and set fire to the mixture. The whole will ourn with a flame the colour of carmine.

156. Though strontites combines readily with all the acids, and possesses alkaline properties, :it has not hitherto been employed for any use- ful purpose. Hereafter it may be found to pos- sess valuable properties ; for it exists in abun- dance, and the Auihor of Nature has formed nothing in vain.

157. Lime is of a white colour, and of a hot caustic taste ; it forms peculiar salts with acids, which is perhaps the most decisive proof that

F 2

66 THE EARTHS. [Ch. 5.

can ever be obtained to identify this or any other earth.

The specific gravity of pure lime is 2.3. It is soluble in 200 parts of water.

Lime forms with sulphuric acid's* compound soluble in wa. ter to a certain degree; so that ibis earth is easily distinguish- ed from barytes and strontian, whose sulphates are insoluble. Oxalic acid is the usual test for this earth, with which it'. farms an insoluble precipitate.

£>p. 1. — Pour a little lnne-water into a wine glass, and put some solution of oxalate of ammonia, equally transparent, into another glass. If the two clear liquors be poured to- gether, a white precipitate of oxalate of lime will immediate- » ly become visible

Exp. 2. — Pour some lime-water in(o a glass, and a solution of Epsom salt into another glass. When th< se transparent : fluids are poured together, a ilnxed precipitate of carbonate,' of magnesia, and sulphate of lime, will be produced ; show- ing the affinity of lime for sulphuric acid.

Exp. 3. — Fos another experiment, tak^ in the same man- ner st parately, lime water, and a solution ot alum The union* of these solutions will produce a mixed precipitate of alumina? and sulphate of lime.

158. This earth changes vegetable blues to a green ; it is incapable of fusion ; it solidifies water, when sprinkled with that fluid, occa- sioning it to give out a great quantity of calo- ric ; it absorbs moisture and carbonic acid when exposed to atmospheric air ; but is itself very sparingly soluble in water, and possesses the pe- culiar property of dissolving more copiously in cold than in hot water.

Quick-tune has such an affinity to water that it will absorb one-third of its weight of that fluid, forming what is called hydrate of lime ; and yet remain perf- ctly dry. The water becomes solidified and identified with the earth. The heat therefore that is evolved in the process ot slacking lime, pro- ceeds from the w i r as it passes to the solid state, and not from the earth as is generally supposed.

Exp. 1. — Pour a little lime-water into a phial, and throw

Ch. 5.] THE EARTHS. 67

some carbonic acid into it. The carbonic acid will seize the iime, and precipitate it in the slate of carbonate of lime.

Exp. 1. — Take the phial made use of in the last experi- ment, with its contents, and convey an additional portion of carbonic acid into it. The carbonate of lime will now be re- tlissolved, and (he liquor rendered transparent. ; Exp. 3. — Take the transparent liquid produced in the last experiment, and give it heat. Th.; earth will now be pre- cipitated in the state of carbonate of lime, as before. : Exp. 4. — Pour some lime-water into a wine-glass, and a little solution of carbonate of potash into another glass. When these two transparent fluids are thrown together, an abun- dant precipitate of carbonate of lime will be the cons-qu. nee.

Exp. 5. — Fill a glass tumbler half full of lime-watfer ; then breathe into it frequently ; at the same time stirring it with a piece of glass. The fluid, which before was perfectly tran- sparent, will presently become quite white, and, it suffered to remain at rest, real chalk will be deposited.

Exp. 6. — Mix in a wine-glass equal quantities of a satura- ted solution of muriate of lime, and a saturated solution of carbonate of polush, both transparent Jluids : stir the mix- ture, and a solid mass will be the product.

159. Lime is never found pure ; it is always in a state of combination, generally with an acid, and more frequently with the carbonic acid, as in chalk, marble, limestone, &c.

The vast mountains of calcareous earth which occur in different parts of the world, owe their origin, in general, it is supposed, to the destruction of marine testaceous animals, which in long process of time formed these extensive and ac- cumulated heaps.

To make quick-lime, the carbonate of lime, by whatever name it is called, whether chalk, marble, limestone, oyster- shell, &c. is broken into convenient pieces, and stratified in alternate layers with coal, furze, or any other fuel, in proper kilns, where it is kept for a considerable time in a -white heat. By this means the carbonic acid and water are driven off, and tolerably pure lime is the product.

160. It is found also in vegetables, and it is the basis of animal bones. It occurs likewise in the waters of all springs and rivers, but always in combination with an acid.

68 ' THE EARTHS. [Cll. 5.

This earth is dissolved in such quantities in the waters Tuscany, that the artists there are said to form basso-relievos, of very considerable hardness, merely by frequently fillir their moulds with the waters.

161. Lime united with the acids is applied t various useful purposes, and, next to silica,; forms a material portion of the solid fabric of the terrestial globe.

The inhabitants of t'owns and houses built on a chalky or limestone foundation are observed to be less liable to infe< tious or epidemic disorders than those of any other situation

162. In its pure state it is used in many of the arts, particularly in making mortar for build- ings. It is employed by the farmers as a ma-, nure ; also by bleachers, tanners, sugar-bakers,., soap-boilers, iron-masters, and others, in their several manufactories, and in medicine.

Lime is used in the manufacture of glue. The design of it is to prevent its becoming flexible by the absorption of|| moisture, and to add to its strength. Some persons use alum* for the same purposes.

] 63, Pure lime has, when united to a certain portion of water, a very strong affinity for silica^ another most essential ingredient in all mortar and cements ; for without this it never hardens.

The nature of the sand which is mixed with lime to lorm < mortar or cement, is of the utmost consequence ; the harder and sharper the sand the better, tor if this matter be of a friable nature like chalk, the mortar must be weak.

164. If pure lime be slacked with water and then mixed with a proper proportion of sili- ca, the gradual absorption of carbonic acid from the atmosphere occasions it in a series of years to become as hard as unburnt limestone.

When lime is made into mortar, it tak^s a long time in ac- quiring the portion of carbonic acid which it possessed in the j quarry ; but the mortar hardens as this absorption takes place. ; This accounts for the great strength of some ancient buildings, ,

K. 5.]

THE EARTHS. 69

which the mortar is found to have a greater degree of firm- than even limestone itself.

165. The use of lime in agriculture may be ttributed to the property which it possesses

hastening the dissolution and putrefaction of 11 animal and vegetable matters, and of impart- lg to the soil a power of retaining a quantity f moisture necessary for the nourishment and jgorous growth of the plants.

. Hence lime and chalk, are found to be particularly useful n sandy soils. Marie is a mixture ot carbonate of lime and iay.

Every tanner should ascertain the nature of his lime before e uses it in agriculture, as there are man) extensive districts l England where the lime contains magnesia, which renders | injurious to the growth of vegetables. See Mr. Tennant's oemon- on this subject in the Pliibsophical Transactions for 799. The limestone of Hie< don in Leicestershire, contains .alt' its weight of magnesia That of Humbleton hill near underland, 45 per cent, of carbonate of magnesia. — Thom- bn's Annals of Philosophy , vol. iv. page 417.

Magnesian limestone is generally of a fawn colour, but it oay be known by its being much longer in dissolving in an cid than common limestone. This is the lime which the i.rorkshire farmers call hot lime. Common lime soon be- omes mild after it is spread upon the land ; and hence it can- ot injure the young plants, as explained in a former note : '•uf where there is a large portion of magnesia in the lime it 's otherwise, because the magnesia does not absorb carbonic iicid with the same facility as lime, and therefore does not •eadily acquire that degree of mildness which is necessary for .he safety of the young crop.

166. There is no good soil that does not con- tain a certain portion of lime, though always, without exception, combined with carbonic acid.

Maries are useful in agriculture only in proportion to the calcareous earth they contain. Unless they contain more han 30 per cent, of lime, they are of no value to the farmer. i Exp. — Take an ounce of marie and dissolve it in a certain veight of diluted muriatic acid. An effervescence will take ilace, and carbonic acid gas will escape from the mixture.

70 THE EARTHS. [C/l. 5.

When the effervescence has entirely ceased, weigh the whole again to ascertain what portion of its weight it has lost by the escape of this air. If the ounce has lost only 40 grains, it ma be concluded that the ounce of marie contained only 100 grain of calcareous earth, and that it would be the interest of a fat mer to pay seven times as much for a load of lime as he mi pay for a load of such marie at the same distance.

167. Lime is used by the tanner in a state of solution ; in this the hides are immersed itt order to dissolve the gelatinous part of the] skin, and to facilitate the removal of the hair.3

The theory of Uuning is shortly this: Alter the impurities of the skins are removed, they are steeped in an infusion «tt oak-bark, which consists of two distinct substances, viz. line gallic acid, and the tanking principle ; the latter of these com- bines chemically with the gelatine and albumen of the sk and forms leather.

168. Lime is used in refining sugar, becaus by boiling the sugar in lime-water the manufac turer, deprives it of a certain uncombined aci which prevents its crystallisation.

Lime is frequently used by chemists in processes where the is a superabundant and injurious quantity of acid. The li seizes the acid, and frees the solution from it, by forming wii it a neutral salt.

169. In the manufacture of soap, lime mixed with the alkali in order to deprive it carbonic acid. The alkali is thus rendere what is called caustic, and by this means i fitted to combine with the oil or tallow which is thereby converted into soap.

As different alkalies require different proportions of lime to render them perfectl\ caustic, every soap-maker should be acquainted with a test by which he may precisely ascertain the necessary quantity.

170. We have hitherto spoken only of lime and of carbonate of lime : but lime is found na- tive in several other states of combination.

hk. 5.]

THE EARTHS. 71

; 171. It occurs in combination with sulphuric cid forming gypsum ; with the fluoric acid Constituting fluor spar ; with the phosphoric cid in a mineral called apatite, and#in some recious stones.

Gypsum, or, as it is also called, selenite or sulphate of lime, hen crystallised, is composed of about 33 lime, 46 parts of ilphuric acid, and 21 water.

Lime combined with the fluoric acid forms those beautiful uor spurs which are brought from the mines of Derbyshire, ^he most usual colour of this mineral is that of a deep pur- le ; but by exposing it to the rays of a hot sun, or to different egrees of artificial temperature, the artist has found the leans of forming u suit of colours of great variety and beauty.

The bones of all kinds of animals are formed of lime and hosphoric acid in the proportion of 48.5 parts of that earth nd51.5 of phosphoric acid.

172. Magnesia is a very soft, white, light arth, with little taste or smell; unalterable in :he fire, and almost insoluble in water.

< Magnesia converts vegetable blues to a green. In this res- ject it resembles the alkalies. It was formerly confounded ivith carbonate of lime. Hoffman was the first who distin- guished it from all other earths.

Though this earth is infusible of itself, it assists the fusion

M" every other body. It requires 2000 times.its weight of wa-

er to hold it in solution : notwithstanding this it has the pro-

)erty of rendering camphor, opium, and resins, soluble in wa-

er. In specific gravity is about 2.33.

Magnesia dissolves in alkaline carbonates, but is not soluble n the caustic alkalies.

Exp. — Magnesia when combined with muriatic acid has

he property of communicating a peculiar colour to flame. If

ome muriate of magnesia be mixed with a little alcohol and

hen set on fire, a very beautiful orange-coloured flame will

foe produced.

Sulphate of magnesia (the Epsom salt of commerce) is found in several mineral waters. The bitter saline waters nerally owe their taste to this salt. That which is found in the shops is generally procured from the mothers which re- after the separation of common salt from sea-water, by

72 THE EARTHS. [dt. 5.

subsequent evaporation and crystallization. All the salti formed with this earth are bitter, and generally very soluble.

173. Magnesia is never found in a state of purity, tjnt always in combination with some acid. It is generally procured from sulphate of magnesia, which exists with the muriate of this earth in sea water, and in many springs.

Exp. — Make hot a saturated solution of suiphate of mag- nesia, and pour into it some solution of carbonate of potash, An immediate decomposition will take place, and carbonate of magnesia will precipitate in a white light powder. Thil' is the process by which the common magnesia of the shops is prepared.

174. Magnesia is also a component part oi several minerals.

Inveraiy-House is built with a stone called lapis ollaris. which contains 16 per cent, of magnesia. Magnes;a is found also in talc, steatites, asbestus, fossil cork, and other minerals. The stones which contain a large portion of this earth have generally an unctuous feci, a fibrous texture, and a silkj lustre.

175. Pure magnesia, as well as the sulphate and carbonate, has important uses in medicine.

When agnefiia is taken as «n aperient, it ought to be ic the state of carbonate 'of magnesia, or what is called mild mag. nesia. When as an absorbent to correct acidities, calcined or caustic magnesia is most proper. On several accounts it is, ©f consequence tn attend to this distinction.

176. It is also required in some chemical pro- cesses, and is employed bv the manufacturers of enamels and porcelain. Calcined magnesia is also the most effectual antidote in case oJ poison by the mineral acids.

li is probable thai some of the most esteemed of the por- celain clays may owe their estimable properties to an admix* turr- of magnesia. Magnesia is of use in porcelain, by b ssen- ing the degree of contraction to which it is liable in the process ■ of bum in »

177. Three other earths are at present known, I

ih, 5.] THE EARTHS. 73

)eside those already enumerated, viz. zirconia,

lucina, and yttria.

As these earths are so extremely pare th;<t it is probable he stodi nt may never be abl to procii* e evt n Bpeeimei s of hem, I have thought it useless to enumerate their prop jc. here.

178. We have hitherto spoken only of the ^ine distinct earths; but minerals are found n every part of the world, in which the earths re combined in different proportions by pro- esses unknown to us, which nature employs o produce that endless variety of what, in ommon language, we call rocks, stones, gems, <:c.

Alumina and silica are the earths which have the greatest ffi iky ; thcv are found in nature off-net' unit' d than any UVr. Some of the hardest stones are formed of these iwa

ill,*.

179. The earths have several properties ia ommon ; yet as every earth possesses different nd specific properties, it is evident that Na- il re designed them for different and distinct urposes of utility.

Maif) of the advantages that these earths might yield to i:*u are probably still unknown ; but thos< benefits which

e now derive from lime, silica, clay, md magnesia, are very umerous, and of the utmost importance.

A few sh" t directions for analysing stone9 are given in Mr.

arkinsoii's Chemical Pocket-book, last edition, page -21 6.

180. Some of the more important uses of lose earths with which we are best acquaint- d, are these: — Lime has an extensive and im- ortant use in agriculture ; it is employed in uildings, and adds much both to the neatness nd durability of our dwellings. Silira is the asis of all mortar and cements, and is a neces-

G

74 THE ALKALIES. [Ch. 6.

i

sary ingredient in earthen-ware, porcelain, and glass. Barytes is employed as a. re-agent. Magnesia, besides being the basis of several salts, is of great use in medicine ; and Alumina, by a due mixture with silica, is capable of form- ing vessels for chemists that will resist the ac- tion of the most concentrated acids ; it is th< material of which the bricks are formed whict construct the walls of our habitations, and if also spread out by the great Author of natun in strata within our hills and mountains, to ar rest the progress of subterraneous waters, am to produce those springs that fertilise the val leys, and which take such diversified course upon the surface of the globe.

CHAPTER VI.

OF THE ALKALIES.

181. The alkalies are distinguished by a acrid and peculiar taste ; they change the bin juices of vegetables to a green, and the yello to a brown ; and have the property of renderic'i oils miscible with water. They themselves a]] soluble in water; they form various salts lk\ combination with acids, and act as powerf] caustics when applied to the flesh of animals.

The word alkali is of Arabian origin, and signifies the «' dre of bitterness."

To a person who has not had an opportunity of e xat-itni an alkali, no written description that can be given will conv any correct idea of the taste or properties of this class of t

THE ALKALIES. 75

Jh. 6.]

ies : let the pupil therefore procure a specimen of each kind, efore he enters upon this chapter. It will be necessary for jim to taste ami examine one of these bodies, in order to ac- uire any thing like a just idea of their nature. Let him torm tash or soda into a neutral salt by saturating it with one of s acids, and he will perceive still more of the nature of these odies.

Exp. 1 . — Take an ounce of a solution of potash, pour upon half an ounce of sulphuric acid ; lay the mixture aside, ami hen cold, crystal* of sulphate of potash will be formed in e liquor. Here a mild salt has been formed from a mix- ire of two corrosive substances.

Exp. 2. — Take caustic soda one ounce, pour over it one

Ijnnce of muriatic acid, both of these corrosive substances.

he produce will be our common table salt.

Exp, 3 — Pour bailing water upon a little red cabbage

iced, and when cold decant the clear infusion. Divide the

fusion into three wine glasses To one add a solution of

lura, to the second a little solution of potash, and to the

bird a few drops of muriatic acid. The liquor in the first

lass will assume a purple, the Second a bright green, and the

nhird a beautiful crimson.

I Exp. 4. — Prepare, a little tincture of litmus. Its colour pill be a bright blue with a tinge of purple. Put a little of it i a phial, and add a few drops of diluted muriatic acid ; its olour will change to a vivid red. Add a little solution of iotash ; the red will now disappear, and the blue will be re- tored. By these means the liquor may be changed alter- lately from a red to a blue, and from a blue to a red, at plea- ure. An instance of the effects of acids and alkalies in changing vegetable colours.

Exp.5. — Take a slip of turmeric paper, and dip it into any dkaline solution; this will change the yellow to a deep brown, ^n many cases turmeric is preferable to litmus paper for de-

r eiing alkali in solution, as it suffers no change from carbo- ale of lime, which is ofte.:> found in mineral waters. This baper will delect the presence of soda, though it should

I mount to no more than-^L-^ih part of the watt r. The »aper thus changed by an alkali, would, if dried, be still use- ul as a test for acids, as these restore its original yellow. Exp. 6. — Add a drop or two of solution of potash to tinc- ure of turmeric. This will change its original bright yellow olour to a dark broivn : a little colourless diluted acid will . restore it. By this tincture we can detect the most minutt portion of anv alkali in solution.

76 THE ALKALIES. [Ch. 6.

Exp. 7. — Immerse a piece of animal flesh in a strong so- lution ot potash or soria.it will immediately be s<> aeud upon by the rikali,as to be soon entirely dissolved.

182. There are three alkalies; two of which have been called fixed alkalies, the other the volatile alkali.

A n w alkali has been discovered by M. Arfvredson, a young Swedish chvmist, in a mineral called petalite This alkali, which is called lithia, isdistingiiished both from potash and soda by its power of neutralising a much larger quantity of any acid. Sir Humphry Da>y has shown that this new sub- stance, like potash and soda, is a metallic oxide. Seven salts have already been formed by the artificial combination of lithia with the acids. Sue Chemical Cutechism, 10th edit, p. 267.

Three new vegetable alkalies have also been discovered viz. morphia, picrotoxine and vauqu- hne. For some accou of their properties consult the Introduction to the xiiith v ume of Thomson's Annals, page Ivi. &c.

183. The epithet fixed is applied to two o ihese alkalies, because they will endure a great heat without being volatilised ; and jet in very high temperature they are dissipated in vapour.

184. Potash and soda are the names now ge- nerally adopted for the two fixed alkalies.

Potash was formerly procured by burning vegetables'] large iron pots; hence it acquired the name of potash. Sod acquired its name from tbe plant salsola soda, which gro on the Spanish coast, and is burnt for its preparation.

135. Formerly the fixed alkalies were con- sidered to be simple substances, no one having been able to decompose them ; but they are now found to be compound bodies.

It will be recollected, tbat, in theirs* edition of the Che- mical Catechism, written seventeen years ago, I offered this opinion of the compound nature of the alkalies. The gal- vanic experiments of Sir Humphry Davy have confirm mI the truth of this conjecture, and proved beyond all doubt, that

[Ch. 6.

THE ALKALIES. 77

potash and soda are both metallic oxides ; as will appear from I the following experiments.

Exp. 1 — Take a small piece of pure potash, gently breathe on its surface, and place it on an insulated plate connected with the negative side of a powerful galvanic battery in a state ofintefise activity. Then bring a metallic wire from the positive side of the battery in contact with the upper surface of the alkali, and soon a v<-ry vivid action will be observed. Small globules, having a high metallic lustre, anil of the ap- pearance of quicksilver, will be seen, some of which will burn with explosion, aod a bright flame as soon as they are formed. Thus potash may be decomposed, and its metallic base rendered visible in a separate state.

Exp. 2. — Take the metallic substance formed in the last expi i iment, called potasium, make it very hoi, and confine it in a small glass vessel of oxygen gas. Here a rapid com- bustioii, with a brilliant white flame, will be produced, and the metallic globules will be converted into a white and solid mass, which will be found to be regenerated pure potash.

Exp. 3. — Place a small piece of potasium within a dry wine glass, and in order to acquii e an idea of its specific gra- vity, pour a little alcohol, ether, or naphtha upon it; when, quitting the bottom of the glass, it will immediately rise to the surface of the liquid, it being, notwithstanding its metal- lic app^ arance, one of the lightest bodies known.

Ext',\ 4. — It i little potasium be dropped into ajar of chlo- rine gas, it burns spontaneously, and emits a bright red light. In tins experiment a white salt is formed, being a true muri- aU of potash.

Exp. 5. — If a globule of potasium be thrown upon water. it decomposes it with great violence ; an instantaneous explo- sion is produced with brilliant flame, and a solution of pure potash is the result.

Exp. 6. — II a similar globule be placed upon ice, it will spontaneously burn with a bright flame and perforate a deep hole ki the ice, which will contain a solution of potash.

Exp. 7. — Take ;» piece of moistened turmeric paper, and drop a globule of potasium upon it. At the moment that it comes in contact with the w«ter, it burns aud moves rapidly upon the paper, as if in search of moisture, leaving behind it a deep reddish brown trac-

186. Potash is chiefly procured by lixivia- tion from the ashes of burnt wood, and other

G2

78 THE ALKALIES. [Ch. 6,

vegetable substances ; but as it exists in mine- rals and earths, there is reason to believe that plants receive it from the earth during vege- tation : hence it may be proper to discard the word vegetable entirely, when speaking of this substance.

It has been ascertained by experiment that potash is form- - ed in what are termed nitre-beds, or collections of the mate- rials from which nitre is procured, though it could have pre- existed in none of them. How this takes place we are quite ignorant.

Potash is prepared in large quantities in wine countries, by the incineration of wine-lees and must. This article is known in France by the name of cendres gravetees.

Potash was called the vegetable alkali, because it was sup- posed to exist only in vegetables. Soda was called mineral alkali, because it exists in rock salt. Soda, as distinguished from potash, has been known but of late years ; and yet some of the properties of soda were known in times of remote an- tiquity. A Hebrew writer speaks of washing with natron. Jeremiah ii. 22.

187. Soda is generally procured from the ashes of marine plants ; but its great depository is the ocean, soda being the base of sea-salt, or « muriate of soda.

The salsola soda, which grows among the cliffs on the sea- coast, is said to be endowed with the property of decompo- sing sea-salt, and that by some process of vegetation it sepa- rates the muriatic acid and absorbs the soda. Hence it ac- quired the name of saltwort. This plant is collected by the i Spaniards with great care, and burnt for the manufacture of barilla, which is a considerable article of commerce.

By means of a galvanic apparatus, soda also may be de- composed and its metallic base exhibited entire.

Exp. 1. — Take 10 or 15 grains of pure soda, treat it in the same way as directed for potash, Exp. 1. p. 77, and small globules of a metallic appearance will be produced.

Exp. 2. — When a globule of the sodium, produced by the last experiment, is thrown into hot water, the decomposition of the water is so violent that small particles of the metal are

Of I. 6.] THE ALKALIES. 79

thrown out of the water, and actually burn with scintillations and flame in passing through the atmosphere.

188. Soda combined with carbonic acid is found in great plenty in the natron beds of Egypt, and in the East Indies ; it occurs also in various other parts of the world, though never in a state of purity.

The natron lakes of Eg; pt annually produce a large" quan- tity of mineral alkali. In summer the water of theae Ink s is

evaporated by the sun, which leaves a bed of natron generally two feet thick; ami this is broken up by wedges, and sent to the European markets.

189. The two fixed alkalies are very similar in their general properties ; but are easily dis- tinguished by the variety of salts which they form with the acids ; and by potash being more deliquescent than soda.

The sulphuric acid and soda form a salt very soluble in water, which crystallises in long separate six-sided prisms, effloresces in the air, and undergoes watery fusion b\ the ac- tion of heat: whereas, the same acid and potash form a salt extremely difficult of solution, which crystallises either in dodecahedrons with triangular faces, or in short In xahedral prisms terminated by hexahedral pyramids, is not affected by the action of the air, and decrepitates in the fire.

The oxalic acid has been used as a test to distinguish the mineral f om the vegetable alkali. With the latter it forms a very soluble salt, but, with the former, one of difficult so- lubility.

The acetic acid is one that may be employed, as it forms a crystallisable salt with soda, and a deliquesce/it salt with potash. Potash may also be known from soda by supersa- turating it with tartaric acid, with which it forms a salt very insoluble in water.

Sir H. Davy has shown that the affinity of the alkalies for acids is owing to their being in opposite states of el< ctricity, the one being naturally in a positive, the other in a negative state; and that the formation of every chemical compound entirely depends on the electrical state of the matei ials of which it is composed. The affinity that the alkalie? have na- turally for acids, will appear from the following experiment,

80 THE ALKALIES. [Ch. 6.

Exp. — Let ft clear saturate)! solution of suphrate of mag. nesia be poured into a strong solution of caustic potash; The potash has such an affinity to the sulphuric acid of the Epsom salt, that it will immediately decompose (hat salt; which will appear from the abundant precipitate that, will result from the union ot these two transparent fluids.

190. There are also several chemical tests, by which these alkalies can be distinguished ; a solution of the ore of platinum in nitro-mu- riatic acid will answer this purpose most com- pletely.

Exp. t. — If a little of any alkaliue solution he poured into a solution of the ore of platinum in nitro-muriatic acid, a yel- low precipitate will be seen; if the alkaline solution contains potash ; but if it contains only soda, no precipitate will occur.

Exp 2. — Into a glass of Aix-la-Chapelle water, or water holding a small poilion of potash, drop a little of the solution of nitro-muriate of platinum, and an immediate yellow pre- cipitate will be produced. This affords an instance of the nature of the means usually employed to detect whatever sub* stances may lie dissolved in mineral waters.

191. The fixed alkalies have various uses in surgery and medicine ; they are the bases oi several salts ; are employed much in the arts ; and are of great importance to the analytical chemist.

192. In the arts they are employed in large quantities by the glass-maker, the dyer, the soap-maker, the colour-maker, and by various, other manufacturers.

Soda and potash are also both used in washing, and for othet domestic purposes; as liny powerfully unite with all greasj substances, which the) render soluble in water.

Exp. — Boil equal parts c.f arnotto »nd common potash ir water till the whole are dissolved. Th s will produce th< pale reddish buff" so much in use, and sold under the name o Nankeen dye.

193. In dyeing, they are employed to extrac the colouring matter from a few of the foreigr i

\Ch. 6.] THE ALKALIES. 81

woods, and, in some processes, to precipitate :he colours from metallic salts.

The fix ;.ik . s facilitate the solution of the colouring )art r>f dye-go* "s and generally render th< colours darker.

194. An alkali is an essential ingredient in common soap, as it is the only article capable of converting tailow or oil into a saponaceous substance similar to the soap of commerce, and enabling it to combine with water.

Exp. — Four a litth water into a phial containing about an ounce of olive oil. Shake the phial, and if the contents be observed we shall find that no union has taken plate. Rut if Iflorae solution of caustic pota-h be added, an<! the phial he then shaken, an intimate combination of the materials will be torm- ied by the disposing affinity of the alkali, and a perfect soap produced.

195. The nature of the action of the alka- lies in making colours is not fully understood, though many colours are now manufactured

I in this country which cannot be made without an alkali.

196. Animal matters are always incinerated (with an alkali to form Prussian blue ; a fixed

alkali is also employed as a flux in the forma- tion of the potter's blue from cobalt; and what I are called French and mineral greens are made Lby precipitating copper from its solutions by | means of these alkalies.

Rrp 1. — Mix -i drachma of potash with an equal weight of < ; dried bullock's blood ; calcine the mixture in a covered cruei- |i ble until it cease to emil any flame, and then wash the cal-

II ciu.-d mass till lh< w bole of the saline matter be dissolved, , and filter the lixivium. N'ow <lissr.lv. 4 drachms of alum in 1 four ounces of water, and add to the solution half a drachm of [ strong nitrate of iron. If these solutions are mix d, the whole will acquire an intense blue colour, and a bulky precipitate will qnicklv be seen at tiie bottom of the vessel, which is a '.rue Pritsfian blue.

82 THE ALKALIES. [Ck.

Exp. 2. — Dissolve some sulphate of copper in a large pc tion of pure water, and, while hot, add to it graduall} a warm solution of carhonate of potash, or carbonate of soda ; this will precipitate a beautiful green colour, similar to that known in' commerce by the name of French green.

Exp 3. — Prepare some sulphate of copper as in the la experiment, and suffer the solution to become quite cold.', Into this cold solution pour a very dilute solution of arseniatft of potash. Here a very different colour will be produced; and which, when dried, will be similar to that used for paint- ing in oil, called mineral green.

197. These alkalies are employed also making alum ; in bleaching linen ; in scouring; wool ; and in many other processes too various to be enumerated.

Alum, which is a triple compound, cannot be perfect with- out the addition of a portion of potash or ammonia.

The design of using alkali in bleaching is to loosen and car- ry off that particular substance in the cloth which occasions it brown colour, and which Dr. Home says is a kind of heav oil.

198. The alkalies are seldom sold in a state of purity, for both potash and soda always con-* tain carbonic acid and water; and are often con- taminated with earths, sulphur, and other im- purities.

The potash and soda of commerce contain nearly one-fil'tb of their weight of carbonic acid, besides lime, silica, &c.

Exp. — Dissolve some soda or potash ot commerce in water, and pour diluted sulphuric acid into the solution. This will occasion an immediate extrication of carbonic acid gas.

199. Both potash and soda, as well as am- monia, have a strong affinity for sulphur; they combine by trituration or heat, and form snl- phuret of alkali, formerly called hepar sulphu- risy or " liver of sulphur."

Such compounds are now generally named from the sub- tance combined with the sulphur ; thus we have sulphurets

Ch. €.] THE ALKALIES. 83

3f potash, soda, lime, &c. Also, those of iron, lead, and the |other metallic bodies.

! Sulphuret ef potash or soda is similar in colour to the liver of animals : it cannot exist but m a dry state, for it decomposes water when dissolved, and then sulphuretted hydrogen is pro- duced.

If equal parts of sulphur and pure potash be triturated to- gether in a mortar, the sulphur will soon acquire a green co- lour, the temperature of the mixture will be raised, and a sitt- phuret of potash formed. Carbonate of potash or soda will answer for this purpose as well as the pure alkalies, if heat |be employed.

200. The alkalies of commerce are purified for the use of the chemist or manufacturer, bj tmixing them with a portion of quick-lime to [divest them of carbonic acid ; they are then lixiviated in proper vessels to obtain a solution of the caustic alkali, free from other impuri- ties.

Exp. — If a little of the solution of carbonate of potash be poured into a glass of lime-water, an abundant precipitate of carbonate of lime will be occasioned by the mixture of these two transparent fluids. This is owing to the readiness with which the lime absorbs carbonic acid.

201. If potash or soda be required perfectly pure for nice purposes, the alkali must be dis- solved in alcohol, and purified by a peculiar process.

202. The fixed alkalies are sometimes used in a stale of combination with carbonic acid, for carbonic acid gives potash and soda the proper- ty of crystallising readily : it also renders them mild, and fit for purposes in which caustic al- kali would be improper.

Carbonate of soda and carbonate of potash are of U9e in che- mical laboratories as re-agents, being employed for purposes which could not be effected by the caustic alkalies. Thus the two fixed alkaline carbonates will precipitate barytes,

84 THE ALKALIES. [Ch. 6.

strontites, lime, magnesia, manganese, and iron, from the solutions, bv means of double affinity

Exp 1. — Dissolve a little common Americas potash in wa- ter, and divide the clear solut'on into two portions. Th saturate one portion with carbonic acid gas, and place hot1 solutions in a cool situation where ihey may remain until th next day undisturbed. If then examined, the one solution wT appear unaltered, while that which was impregnated wit carbonic acid will be found in a crystallised state.

Exp. 2. — Pour some barvtie water, or a little of a solution Of put e stroi.tites, into a wine-glass, and add a small portion of the solution of carbonate of potash or soda. An immedi- ate precipitate of the barytes or strontites will be perceived. Hence the use of carbonated alkali in precipitating these earths.

203. The other alkali, ammonia, when un combined with water, or any other substance, exists in the state of gas, and is then so ex- tremely volatile as to exhale at all known tem- peratures.

204. Its volatility is diminished in some de- gree by combination with water, still more so by combining with carbonic acid, and most when combined with the mineral acids.

205. In the gaseous state it has a remarkably pungent smell, it instantly extinguishes flame, and would be fatal to any animals that were obliged to breathe it. It is lighter than atmo- spheric air in the proportion of 6 to 10. ,

Exp — By th following process ammonia may be formed so as to become evident to the senses in a short time. Take some filings of tin or zinc, pour on them some moderate]! diluted nitrous acid. After a short time stir into the mixture some quick lime, or caustic alkali, and a very strong pungent Smell of ammonia will be produced.

206. There is a strong mutual attraction be- tween ammonia and water ; they form the li- quid ammonia ; in which state this alkali is ge- nerally used.

ik. 6.] THE ALKALIES.

85

It is owing to the levity of ammonia, that water bccomts pecifieally lighter in proportion to the quantity of gas it con- wins. Next to hydrogen, ammonia is Hie lightest of all the aseous bodirs.

JExp. — Mix two parts of fresh burnt lime in powder, with toe part of powdered muriate of ammonia ; put the mixture nto a small glass retort, to which a receiver i<- connected, iimilar to the apparatus, fig. 23. Pluto VI. Iflheheat of a amp be now applied to th~ retort, the g-is will be disengaged n abundance, and will combine with the pure water in the receiver. When the water is saturated, the strongest liquid ammonia will be formed by the process. If the liquid be now weighed, the specific gravity of the water will be found to be [•educed bv the addition of the ammonia from thai of 1.000 to hat of about 0.910.

207. Ammonia has another peculiar property, jthat of reducing the oxides of metals to a me- tallic state.

Ammonia being composed of hydrogen and nitrogen, the hydrogen seizes the oxygen from the m< tal and forms water, while the nitrogen escapes in a gaseous form. Some metals are oxidized and dissolved by liquin" ammonia.

208. Ammonia is a compound of hydrogen and nitrogen, in. the proportion of about one part of the former, and four parts of the latter when calculated by weight ; or if calculated by volume, of one measure of nitrogen and three of hydrogen, condensed into two measures by the combination.

One thousand parts of ammonia consist of 807 parts of ni- trogen, and 193 parts of hydrogen. This is the result of ex- periment ; but Sir H. Davy has lately, bv means of galvanism, separated oxygen and a metallic substance from ammonia.

209. Ammonia may be decomposed by the electric spark. Oxygen gas will also decom- pose it by the assistance of heat, and then ni- trous acid and water will be the result.

Dr. Priestley was the first chemist who decomposed am- raoniacal gas; indeed he was the first who procured it in a

H

86 THE ALKALIES. [Cll. 6.

state of purity ; but I believe Berthollet was tbe first person who proved its composition by synthesis as well as analysis.

Exp — Fill four-fifths of a long glass tube with water satu- rated with chlorine gas, and the remaining fifth with water strongly impregnated with ammonia, and invert it in a saucer of water. When the tube is inverted, the ammonia, on ac- count of its lightness, will pass through the solution of chlo- rine, but by its passing a strong effervescence is produced, and a decomposition ensues. When the effervescence has ceased, a portion of nitrogen gas will he found in the tube.

210. A very different result may be obtained if ammonia be decomposed in contact with m cury, by means of galvanism; for in this ca a metallic substance of a very uncommon n ture may be separated from this alkali.

This experiment was first made in the year 1808 by Tfl Zeobeck of Jena, and also about the same time by MM. His- singer and Berzelius of Stockholm. Mercury, by combina- tion with about one twelve-thousandth part of its weight of new matter, is thus rendered a solid, and at the same time so expanded in volume that its specific gravity is reduced fro 13.5 to less than 3 ; while all its metallic characters of colon lustre, opacity, and conducting powers, remain unimpaired.

As the quantity of ammonia obtained from different su" stances corresponds with the quantity of nitrogen which th contain, and knowing that ammonia is one of the products putrefaction, it has occurred to me that a manufacture of i latile alkali might be established with advantage on any part of the coast where ht rrings, pilchards, &c. arrive in su<" shoals as to be employed in manure for land. Besides, asfii bom s contains more phosphoric acid than those of quadrupe the bones ought be advantageously employed afterwards the manufacture of phosphorus, &e.

2H. All animal and vegetable substance when in state of putrefaction, will furnish am monia : this alkali is, however, generally pro- cured in England by a dry distillation of bones, horns, and other animal substances.

Ammonia is also found in mineral waters. According to Dr. Austin, ammonia is formed whenever iron rusts in watei which has a free communication with the air. Large quan-

ft. 6.]

THE ALKALIES. 87

ties of ammonia are now procured from the waste liquor in

ie manufactories ot" the gas-light companies at a very cheap

ite. Exp. I. — Mix one part of powdered sal-ammoniac with

wo parts of powdered quick-lime in a retort, and apply the

eat of a lamp. This will disengage the gas in abundance. )n account of its affinity for water, this gas must be received >ver mercury, when it is intended to exhibit it in the slate >fgas. Exp. 2. — Ammnniacal gas may be procured also by heat-

)g strong liquid ammonia, and colli cttng lh^ gas as before. Exp. 3. — li muriatic or acetic acid he held over any thing

vnlving ammonia, wb>te fumes will appear, which are ow- ng to the ammonia uniting with the acid, and forming a visible

loud, which is a true neutral salt in vapour. These acids

re the tests usually employed it) discover the presence of

mmonia.

Exp 4. — Whenever uncombined muriatic or any volatile icid is suspected to be present in any chemical mixture, it

t may be detected by ammonia. A single drop of ammonia in a feather, or small slip of paper, and held over the mix-

ure, will immediately render the vapour visible.

Exp. 5. — Let sulphuric acid be poured into a saucer upon Lome acetate of potash. Into another saucer put a mixture of about two parts quick-lime, and one ol sal ammoniac, both in powder, adding to these a very small quantity of l>oiling water. Both saucers while separaie will yield invisible gases; but the moment they are brought close together, the operator will be enveloped in a cloud of very visible vapours.

212. Ammonia is applied to various pur- poses, as well in our manufactories as in me- dicine; but in its combination with water it is preferred ; it is also a valuable re-agent to tlit chemist.

Ammonia is of use in making archil, an article in great de mand with dyers; it is constantly employed in chemical labo ratories to distinguish zinc from other metals, and to delect •he presence of copper, cobalt, kc.

1. — Pour a bide caustic ammonia into a clear solu- tion of sulphate of zinc. This will precipitate the metal in a white powder. If the phial be now shaken, the zinc will be immediately re-dissolv< d, thus serving as a test to distinguish ziuc from iron and various other metals.

88 THE ALKALIES. [C7i. 6.

Exp. 2. — Drop as much nitrate of copper into water as Will form a colourless solution; then add a little ammonia, equally colourless, and an intense blue colour will arise from' the mixture

Exp. 3. — Take the blue solution formed by the last expel riment, »dd a i.ithj sulphuric acid, and the colour will disoM pear; pour h a little solution of caustic -ammonia, and the blue coloui will be restored. Thus ma> the liquor be alien nat ly changed a~1 pleasure.

Exp 4. — Dissolve soon- oxide of cobalt in caustic ammoB nia; ihis will produce a red solution different in colour from I that of all other metallic solutions.

213. This alkali, when combined with car-*" bonic acid, takes a concrete form and a beauti- ful white colour ; being then the article known in commerce by the name of volatile sails.

Exp - Wh< n ammoniac*] gas is passed into carbonic aci. gas, tin two gases become condensed, and a crystallisation I carbonate of ammonia, in silky fibres or fine powder, takes place upon the internal surface of the vessel. This is a beau- tiful «.-xp riment ; but it must be made over mercury, and not upon water, h« water would absorb the ammoniacal gas

214. Ammonia is serviceable in dyeing, and in staining ivory; but its principal use is ii making the muriate of ammonia, of which it i the basis.

215. The muriate is formed by combining ammonia with muriatic acid. It is known i commerce by the name of sal-ammoniac.

Exp 1. — Convey some muriatic acid gas into a glass jar containing a portion ofa'mmoniacal gas. From the inixluw of these" tvo invisible gases, a solid substance will be produc ed ; viz. the common sal ammoniac: this may he pereeivedtq deposit itself Upon the sides of the vessel in a neat crystallised for in.

Exp 2 — Take carbonate of ammonia, (the common vola- tile smelling salt,) and pour upon it muriatic acid so long as any fferve.se ^nce continues, The poduce will be a solid salt, p :l. etl;. inodorous, and of lit H tasi .

216. Sal-ammoniac is also employed in many

Hi. 7.] THE ACIDS. 89

four manufactories, particularly by dyers to ive a brightness to- certain colours; also by raziers, tin-plate workers, and others ; and in ledicine.

Sal-ammoniac is used also by some dyers in what they call imposition, to prevent the tin from precipitating. In lin- ing metals it is of use to cleanse the surfaces, and to prevent lem from oxidising by the heat which is given to them in the beration. This salt is employed also in the assay of metals, o discover the presence of iron.

217. Formerly we were indebted to Egypt )r the chief supply of this very useful salt, ut now it is made in various parts of Great Britain.

CHAPTER VII.

OF THE ACIDS.

218. The name acid, in the language of fhemists, has been given to all substances, whe-

er liquids or solids, which produce that sen- sation on the tongue which we call sour : some iiowever are comprehended in this class which jo not possess this character.

219. Acids change the blue, green, and pur- ile juices of vegetables to red ; and combine ,vith alkalies, earths, or metallic oxides, so as :o form those compounds called salts.

It is desirable as soom a<> possible to give the chemical stu- lent correct ideas of the properti.es of the acids and alkalies. To this end, let him be early instructed in the use of chemi- cal tests. If he be accustomed to carry a few test papers in lis pocket-book, it will be a verv rational amusemeot to try H2

:

90 THE ACIDS. [Cll, 7.

the succulent vegetables which h> will meet with in his walks, many of which will be found to contain acids of different kinds. The hope of making an important discovery will fur- nish arr additional zest to tliid employment.

Exp. 1. — Make an infusion of red roses, violets, or mal- low flowers ; treat it with solution of potash, and it will be- come green ; the addition of diluted muriatic acid will convert, it immediately to red. This experiment may be frequent- ly varied, and furnishes an excellent test tor acids and alka- lies.

Exp. 2. — Pour a little tincture of litmus into a wine-gla and into another some diluted sulphate of indigo; pour the two blue fluids together, and the mixture will become pei feet I y red.

Exp. 3. — Take a slip of blue litmus paper, dip it into ace tous acid, and it will immediately become red. This is a test so delicate, that, according to Bergman, it will detect the presence of sulphuric acid, even if the water contain Only one part of acid to thhty-five thousand parts of water. Litmus paper which has been thus changed by immersion in acids, is, when dried, a good test for the alkalies; for, if it be 'lipped in a fluid containing the smallest portion of alkali, the red will disappear, and the paper be restored to its original blue colour.

Exp. 4. — Take some water impregnated with carbonic acid, and add to it a little blue tincture of litmus. The who! will b,j changed to a red.

Exp. 5. — Take some of the same carbonated water, boil it. Then add a little tincture of litmus, and the biu colour w 11 experience no ehatrge.

220. Most of the acids owe their origin t the combination of certain substances wi ' oxygen, which was formerly called the acidify iug principle. These axioms must, however, be now received with some limitation.

the metals, and the other simple combustibles, hydrogen not exc -pted, a> e all coiiver1 hie into acids.

The term oxygkx is derived from the Greek words oxys geinomai, signifying that which produces or generates acids;

fJh. 7.] THE ACIDS. 91

[but as Sir Humphry Davy has discovered thnt this substance lis necessary also to the production of the alkalit-s, some other term, surely, should be found that would be more applicable

ideprivi

221. Some acids may be decomposed, and 'ed of their oxygen, and others may be

Iformed artificially by a direct combination of oxygen with certain radicals.

Any combustible body, that has a greater affinity for oxy- gen than oxygen has for the radical of the acid, will decom- pose lliat acid. Charcoal, when made red-hot, will in this way decompose sulphuric acid.

Exp.l. — Put a little common sulphur into an iron dish, place it under a jar of oxygen gas, and set fire to it, and sul- phuric acid will be formed. This is an example of the for- mation of an acid by combustion.

Exp. 1. — Take the acid formed in the last experiment, concentrate it by boiling, mix it with a little powdered char- coal, and submit the mixture in a Florence flask to the heat of an Argand's lamp. By this process sulphur will be rege- nerated, and will sublime into the neck of the flask. An ex- ample of the decomposition of an acid.

222. Some of these acidifiable radicals com- bine with different proportions of oxygen, and consequently produce different states of acidity.

The hist portion of oxygen converts some bodies into ox- ides, as is the case with carbon, forming carbonic oxide ; and sulphur, forming oxide of sulphur : the second, into that chss of acids of which the specific names drawn tiom their parti- cular bases terminate in ous,s\s the sulphurous acid: the third degree of oxygenisement changes some of these into that division of acids which are distinguished by the termi- nation in ic, as the sulphuric acid, &c.

223. When two acids have the same radical, but contain different quantities of oxygen, they are distinguished by their termination. The name of that which contains most oxygen ends in ic, the other in ous. Thus we say sulphuric

92 THE ACIDS. [Ch. 7.

acid, and sulphurous acid ; phosphoric acid, and phosphorous acid.

224. A variety of substances are capable of being acidified by oxygen ; for the mineral, the vegetable, and the animal kingdoms, all furnish bases or radicals, which become acid by their union with this important agent.

The mineral acids are generally formed with a peculiar base and oxygen ; the vegetable acids, with carbon, hydrogen, and oxygen ; while the animal acids are composed of the same substances united with nitrogen.

Some of the mineral acids are decomposable, as already mentioned, by charcoal heated to redness. Some of the ve- getable acids are also decomposed, and reduced into water and carbonic acid, by leaving them in an exposed situation to the action of their own principles: others may be changed into different acids, by imparting or abstracting a portion of oxygen.

The animal acids are of all others the most liable to decom- position. In an elevated temperature the carbon and oxygen unite to form carbonic acid, and the hydrogen and nitrogen oombine to produce volatile alkali.

2,2,5. There are substances however that pos- sess acid properties which contain no oxygen. '' Until lately, there were also three acids whose composition was unknown.

Those acids were, the muriatic, the fluoric, and the boracic; these, however, have now yielded to the power of voltaic electricity, and their bases have been separated.

Sulphuretted hydrogen has all the properties of an acid without oxygen; but the following experiments show that it has a great affinity for that substance. And it has not yet been proved that prussic acid contains any oxygen. Iodine and chlorine also are capable of forming distinct and peculiar acids by combination with hydrogen.

Exp. I. — If a bit of silk be immersed in diluted acetate of lead, and exposed while wet to a stream of sulphuretted hy- drogen gas, a brown tinge will instantly diffuse itself, like a passing shadow, over the whole surface of the silk, accompa- nied with a bright coat of reduced lead resembling silver.

Exp. 2. — If a piece of silk be immersed in an aqueous so-

lu 7.] THE ACIDS, 93

tion of muriate of tin, and exposed while ivet to a stream of e same gas, reduced tin of great brightness will immediate* cover the surface, and in a little time this will u? aecom- ni'-d b) various colours, such as blue, orange, and purple. Erp. 3. — A piece of silk tn uted in the same way, out dip- ■ ! .n an aqueous solution of mu;-iate of arsenic, will be co- p ii with resplendent metallic arsenic, attended with a citron •How colour.

226. The acids were formerly divided into iree classes, viz. the mineral, the vegetable, id the animal acids ; but the more useful and ;ientific way of dividing the acids is into two asses only.

227. The undecomposable acids, and those hich are formed with two principles, are com- rised in the first class; while those acids winch

e formed with more than two principles corn- use the second class.

Poorcroy, in his wot k entitled PhVf)soj)lde Chimirpm, di- rtes the ae.i-'s into four classes: 1st, those with known i\.di- Is ; 2d, in-known ditto; 3d, single ditto; 4th, compound tto; but I conceive that the above division Is better eale** !ted for an elementary treatise.

. 228. The acids of the first class are, the lulphuric, the sulphurous, and the muriatic cids ; the nitric, the carbonic, the phosphoric 'nd phosphorous; the fluoric, the boracic, the Irsenic and arsenous ; the tungstic, the molvb- fcic and molybdous ; the telluric and the chromic I cids.

229. The acids of the second class are, the jcetic, the oxalic, the tartaric, the citric, the ialic, the lactic, the gallic, the mucous, the enzoic, the succinic, the camphoric, the sube- ic, the laccic, the prussic, the sebacic, the uric,

e amniotic, and the fluoboric acids.

94 THE ACIDS. \Ch. 7.

JJs several of these acids are rare, and are seldom used in the arts, it will not be necessary here to give any account of their origin or properties . Confining- myself therefore to the acids -winch more generally occur, 1 shall begin -with those of the first class.

230. Sulphuric acid is procured by burning sulphur, in contact with some substance con- taining oxygen; by which process the sulphur combines with the oxygen, and becomes acidig fied. In commerce it is commonly called oil of vitriol.

The pupil maybe satisfied that sulphuric acid is really pro- duced by the combustion of sulphur, by burning a little sul- phur, mixed with an eighth of its weight of nitre, in a glaw jar of oxygen gas inverted over water, as directed in the I Chemical Catechism, 10th edition, page 143. He may see that sulphuric acid has actually been formed, by adding a few1 ! drops of a solution of muriate of barytes to the water; for as this is the proper re-agent for discovering the presence of sulphuric acid, it will not fail in this case to precipitate the barytes.

231. The sulphuric is a very ponderous, corrosive acid, destitute of colour and smell, and has a very strong acid taste. It has a great attraction for water, and, when com- bined with the alkalies, the earths, or the me- tallic oxides, forms with them those salts called sulphates.

Sulphuric acid and water combine so intimately that (he eompound gives out a large portion of caloric.

Sulphuric acid is a test for barytes: a single drop poured into any solution of this ear'h instantly causes a white preci- pitate. It is also a good test for lead.

Exp — Weigh one pound of water into a vessel capable ol bearing a sudden heat. Pour gradually four pounds of sul- phuric acid upon the water, and stir the mixture. So great will be the condensation of the water by this mixture, that the temperature ef the whole will instantly rise to 300°.

£32. The sulphurous acid, like the sulphu-

?h. 7.] THE ACIDS, 95

ic, is a combination of sulphur and oxygen, >ut with less oxygen, or, we may say, with nore sulphur, than the latter.

Sulphurous acid gas is produced by the sloio combustion of ulphtir. If tli is gas be received in water, the gas combines viih it, and sulphurous acid will be the result. Witter at 40° bsorbs one third of its weight of sulphurous acid gas.

Exp. — Put into a glass retort two parts of sulphuric acid, nd one of mercury, and apply the heat of a lamp ; the mix- jre effervesces, and a gas issues from the beak of the retort,

hich may be received in glass jars filled with mercury and

andjng in a mercurial trough. In this process the mercury i the retort combines with a part of the oxygen of the sul- furic acid ; and the sulphuric acid, having lost a certain por- lon of its oxygen, is converted into sulphurous acid.

233. Sulphurous acid in the gaseous state is nvisible like air, but of a strong suffocating [mell. It is readily absorbed by water, and hen forms liquid sulphurous acid. It is capa- >le of uniting with various bases, and forms the salts called sulpldtes.

Sulphurous acid gas is very abundant in the environs of vol- anos. It was the vapour of sulphurous acid which suffocated ?liny the naturaliat in that eruption of Vesuvius by which ierculaneum was swallowed up in the year of Christ 79. Sulphurous acid gas is composed of 68 parts sulphur and 32 rnrts oxygen. Its weight is double that of atmospheric air.

Sulphurous acid possess' s very slight acid properties. In- itead of changing vegetable blues to a red, as acids generally lo, it invariably renders them white.

Ext).- -Suspend a red rose within a glass jar similar to that described at fig 25, Plate VI. and in that situation expose it :o the confined fumes of a brimstone match. This will soon jjproduce a change in its colour, and at length the flower will become quite white.

234. That peculiar acid which we call mu- riatic is usually obtained from sea salt. Until [lately, the radical or base of this acid was en- tirely unknown.

Muriatic acid is disengaged from muriate of soda in thr

96 THE ACIDS. [Ch. 7.

state of gas, by a process similar to that for drawing the nitric acid. It preserve its gaseous state even in the coldest tempe- rature, unless it come in contact with water; and if thrown upon ice it melts it in an instant. It is nearly double the spe- cific gravity of atmospheric air. It may here be remarked tha' all acids contain water as an essential pa> t of their com- position, and that the whole of the water cannot be separated from any of them without occasioning the destruction of the acid.

Exp. — Prepare ajar of muriatic acid gas; suffer the gas to become quite cold, and then suspend a solid lump of ice with- in it. and notice the effect. The gas, in consequence of;B great affinity for water, will give out so-much of its latent calo^ ric, thai the ice will be melted in an instant.

235. This acid in the gaseous state is invisi- ble like air ; and has a pungent suffocating smell. With water it forms the liquid muriatic acid, which preserves the smell of the gas, and gives out white fumes when exposed lo the at: mosphere. This acid is much employed in the arts and in chemical laboratories. With va* rious bases it forms the salts called muriates*

Liouid muriatic acid, or water, saturated with this gas, I about the spec. grav. 1.196. The muriatic acid of com men* varies from about 1.120 to about 1.164.

Sulphuric, phosphoric, nitric, and some other acids maybe decomposed b> charcoal ; muriatic acid is unalterable by anj of the combustibles with which we are acquainted.

Muriatic acid is the best test for silver, owing to the affinitj of this acid for silver, and the insolubility of muriate of silver*

Exp. I. — Pour one part of sulphuric acid upon two parti of dry muriate of soda in a tubulated retort, and collect th( gas, as it becomes disengaged, over mercury in a pneumatii apparatus. This is muriatic acid gas.

Exp 2. — Take some of the muriatic acid of commerce heat it in a glass retort, and muriatic acid gas may be collect ed as in the last experiment.

Exp, 3. — Proceed as in the first experiment, but insteai of coveting the gas over mercury, receive it in a vessel con tabling a small portion of wate'r. By these means liquid mu riatic acid will be formed.

Exp. 4.—Take a small quantity of silver, or a piece of ai

Ch. 7.] THE ACIDS. 97

Ore containing silver, and digest it in some purified nitric acid, which will dissolve ifce whole of the silver. A single drop of muriatic acid will separate a portion of the silver in white flakes, which will fall (o the bottom of the glass in an insolu- ble precipitate.

Exp. 5. — Proceed as in the last experiment ; hut instead of using muriatic acid, drop in a portion of common salt, which •will as effectually precipitate the silver. By these m(;ansany Ore may he divested of the whole of the silver that it contains.

236. It is now a prevailing -opinion that the oxyinuriatic acid, or chlorine as it is called, is a simple substance. It is known in the gaseous state, and in combination with water : but in the latter form, or, when combined with the alkalies or alkaline earths, it is more coinmon- r used in the arts.

The gaseous substance which was formerly called oxyge- nised muriatic acid and now chlorine, is not a compound of muriatic acid and oxygen as has already been remarked, but a simple body obtained from common salt by distillation with the black oxide of manganese and sulphuric acid. The modern theory is this : that common salt is a true muriate of soda only while it remains in an aqueous solution: and that »hen re- duced to dryness, both the mm iatic acid and the soda become decomposed; ;nd the hydrogen of the muriatic acid uniting with the oxvgen of the soda, they both pass off in the form of wa- ter ; while the chlorine of the muriatic ;icid uniting with the metallic base of the soda forms cldoride of sodium, which is the true character of our common atJt when in a dry state.

Exp. 1 . — Chlorine gas may he obtained for chemical ex- periments by the following method : Put into a retort a little black oxide of manganese in powder ; ami pour upon this double its weight of strong muriatic acid ; connect the retort with the pneumatic trough, and receive the gas ov< r water. When the ascension of the gas slackens, apply tin h t of I lamp, and it will be disengaged in abundance. Its s, gravity is to that of hydrogen, nearly as Si to 1.

Exp. 2 — If a small quantity of liquid oxymurialic acid he wanted for experiment, it may readily be formed, mixt d with a little euchlorine, by dissolving a few grains of oxymuriate or chlorate of potash, and adding the solution to an ounce of common muriatic acid. It is of a yellowish green colour,

98 THE ACIDS. [Ch. 7.

which was the cause of its being called chlorine t a name given to it by Sir Humphry Davy.

237. Chlorine gas is so suffocating, that it cannot be breathed without great injury; yet it will support combustion. This gas discharges vegetable colours ; it burns all the metals, and even when combined with water, will dissolve gold and platinum : with various alkaline and earthy bases it forms salts, called chlorides.

Aciiis in general change blue vegetable colours to red ; but chlorine destroys colour. Instead of considering it as one of the acids, it would be more proper to call it an acidifying principle, tor it possesses few properties which characterise that class of bodies lis taste is not acid, but astringent ; and, unlike the acids, it combines very sparingly with water. It has not been decomposed either by electricity or galvanism; which is a presumptive proof of its being a simple substance.

The great use of chlorine is in bleaching. A full account of the methods of applying it may be seen in mv Essay on Bleaching in the 4th volume of the Chemical Essays.

Esp. 1. — If a few strips of dyed linen cloth, of different co- lours, be dipped into a phial ot oxy muriatic acid, the colours will be quickly discharged ; for there are few colours that can resist its energetic effects. This experiment may be con- sidered as a complete example of the process of bleaching coloured goods.

Evp. 2. — Procure a glass jar, such as is generally used for deflagrating the gases, and fill it with otymuriatic acid gas. If nickel, arsenic, or bismuth in powder be thrown into this gas, and the temperature of the atmosphere be not lower than 70°, the metal will inflame, and* continue to burn with the most brilliant combustion.

Ei'p. 3. —Prepare a jar of chlorine (oxymuriatic gas,) and suspend in it a piece of Dutch metal, or copper-foil ; it will immediately inflame, and the combustion will continue till the whole is consumed, affording a very striking spectacle. It will however soon subside in the jar, and form a substance exactly similar to the native muriate of copper brought from Peru.

238. Chlorine will combine with oxygen, with hydrogen, and with nitrogen ; also with carbu- retted hydrogen, and with the carbonic oxide \

Ch. 7.] THE ACIDS. 99

some of which combinations possess very curi- ous properties.

Exp 1. — Chlorine and oxygen do not unite by simple mix- ture ; but il chlorate of potash, formerly calh d byperoxyma- riate of potash, be distilled by a gentle heal in a glass retort with diluted muriatic acid, a gas will be set at liberty which consists of chloi ine and oxygen. II this gaseous compound he received over mercury, it will be found to possess a bi colour than chlorine, more inclined to yellow ; and its sm^ll will be different, being like that of burnt sugar.

Exp. 2. — Hydrogen and chlorine unite readily. If equal measures of each he mixed ami exposed to the light of day, {he two gases will gradually combine without condensation, and the result will be muriatic acid gas. In making this ex- periment the mixed gases must not he submitted to the ac- tion of the sun's rays, as this would occasion them toexplode.

Nitrogen does not unite with chlorine by simple mixture, but this compound may be termed by passing chlorine gas into a solution of nitrate of ammonia. By this proci salt is decomposed, and part of its nitrogen unites with the ehlorine to form the compound in question, called chloride of azote, a substance possessing some very singular and danger- ous properties.

The mixture of carburetted hydrogen with chlorine has been treated on by Dr. John Davy in the Philosophical Trans- fictiojxs for 1S14. This also possesses some very remarkable properties.

Carbonh oxide and chlorine when united by peculiar man- agement f rra a singular compound, which the discoverer, Dr. John Davy, has n:>med phosgene gas. This compound gas, which Dr. Thomson now calls chloro- carbonic acid, has a verv peculiar and remarkably pungent odout ; it is the heaviest of all the known gaaes, 100 cubical inehesofit weigh- ing nearly 112 grains, which is almost four times as much as an equal volume of atmospheric air.

239. By peculiar management chlorine may likewise, be combined with sulphur, with phos- phorus, and with the metals, including also the metals of-the earths and alkalies.

When sulphur is heated in contact with chlorine, a red fuming fluid is obtained of the specific gravity of 1.60. It is called chloride of sulphur, but has not yet been found to be of any use in the arts.

The combination of chlorine with phosphorus has very pe=

[GVi.7.

ubslance ; very

boiling water;

o ling cr)Stal-

Ihophorana.

and perchloridM

"all the metals, and ia

m:inv rl?^NiiSE£^jWM¥tT»HHttrjjf^TB--^^::T" y ' *' with inflammal

tion, those metals which are most readily oxidised burning I with the most brilliancy.

By heating potassium or sodium in chlorine gas, compounds I m:iy be formed resembling those which result from heating'.; those metals in common muriatic acid gas. Ten grains of po- ' tassium or sodium absorb about eleven cubic inch measures of chlorine: but the combination is accompanied with a more-j brilliant combustion than when these alkaline metals are burnt in oxygen gas.

240. Chlorine has no action whatever upon charcoal, even though the charcoal be intensely hot when plunged into it. This fact has been adduced as a decisive proof that chlorine con- tains no oxygen.

241. Nitric acid is one of the constituent parts of nitre or saltpetre. It is a compound* of oxygen and nitrogen, in the proportion of about 26 parts by weight of nitrogen, to 74 of oxygen.

_fcrp. 1. — Take three measures of oxygen gas and one mea- sure and a quarter of nitrogen gas, and pass a number ot elec- tric explosions through the mixture. This will occasion a union of these gases, and nitric acid will be the product.

Exp. 2:— Upon an ounc^ or two of nitrate of potash, in a J retort to which a proper receiver isjoint d, pour some sulphu- ric acid, and by means of the heat ot a l^mp the nitrous acid, may be readily obtained.

242. Pure nitric acid is clear and colourless, like water ; its smell is pungent, its taste ex- ceedingly acid, and its action on animal sub- stances very corrosive. It has the property of permanently staining the skin yellow. It has

III. 7.] THE ACIDS. 101

i great affinity for water; is capable of oxidising nost of the metals, and with various bases forms he salts called nitrates.

243. The common nitrous acid, improperly o called, is merely nitric acid impregnated vith variable portions of nitrous acid gas.

Exp I. — If nitric acid be poared on iron filings, the acid vill in part l>e decomposed ; its oxvgen will rentier the rae- u soluble, and nitrous gas will be thrown out in copious red unv s.

Exp. 2 — Take a few shreds or tilings of copper, and pour tverthema little diluted nitrous acid, in the proportion of bout three parts of water to one of acid. The gas evolved s nitrous g-is.

ExU. 3. — Take a portion of dried sulphate of iron, and an

ual quantity of nitrate of potash, grind them together in a .uort.r. and put the whole into a small glass retort. Adapt

r- ceiver to the- retort with one or two bottles, according to be plan of Woulfe's apparatus, Plate I. fig. 1. and apply the fiea' of an Argand's lamp. After some time a gas will be lisengag d, which will be condensed by the cold receiver, arming th< ti lie nitrous acid. We have here a enrrnsiw fluid rodnoerl from the mixture of two mild and solid substances.

244. Nitrous acid is similar to nitric acid n its properties ; but its colour varies accord- ing to the proportions of nitrous acid gas, which it has absorbed, and the water that it con- tains.

i) . Priestley having separated nitrous gas from nitric acid; by meat s dfjrWn, be received the gas under an inverted ves- sel filled with water, and found it a transparent colourless gas, n =• mbline air ; wh< oce it appears that it is red or coloured, onl' when combined « ith atmospheric air.

Sitrous acid is generally used for purposes of manufacture ar,(i • xperimewt The nitric acid is principally employed in medicine. Two parts of either nitrous or nitric acid, and one ot muri tic acid, form aqua regia, or nitro-muriatic acid, the tru" solvent of gold.

The changes which take place on the addition of water to strong nitrous acid exhibit very curious phenomena. Differ- ent portions change its coloui to a blue, a green, a yellow, I 2

102 THE ACIDS. [Cfo. f.\

&c. while the vapours which rise from it preserve their ori- gin h I flame coloured red.

Exp. 1 — If four parts of water, by measure, he added to twelve parts of strong fuming nitrous acid, the colour will be changed from a deep yellow to a green.

Exp. 2. — Mix four measures more of water with the di- luted acid produced in the last experiment, and the colour! will thereby be changed to a paler green, mixed with yellow*

Exp. 3. — Add four measures more of water to the abovej and the green will disappear, and mpale yellow acid will bd produced.

Exp. 4. — If 40 measures of water be now added to the yel-J low acid produced in the last experiment, you will have an acid as colourless as pure water.

245. Carbonic acid is a combination of car- bon and oxygen. It was formerly called fixed air, on account of its being so intimately com- bined in chalk, limestone, magnesia, &c.

Carbonic acid is composed of 27. 5 parts carbon and 72.5| oxygen ; which has been ascertained b) anal) sis as well asl synthesis.

Exp. 1. — Put a small piece of phosphorus into a crucible,' cover it closely with common chalk, so as to fill the crucible. Let another crucible be inverted upon it, and both subjected?! to the fire. When the whole has become perfectly red-hot, remove them from the fire ; and when cold, the carbonic acid of the chalk, will have been decomposed, and the black char" coal, ihe basis of the acid, may be easily perceived among the mat rials.

Exp. 2 Put about an ounce of marble grossly pul

into an eight ounce phial, with about an equal quantity ter. Pou1 upon it a little sulphuric acid, and carbonic gas will bf evolved.

246. Carbonic acid is invisible when in the state of gas, and unfit for combustion, or re- spiration. Water, by pressure, may be made to absorb three times its bulk of this gas ; by which it acquires an acidulous and not unplea- sant taste. Carbonic acid in the proportion in which it exists in atmospheric air is favourable to the growth of vegetables, but in a large pro

lv< rised ' * of wa- il ic acid

Vl. 7.] THE ACIDS. IGo

jortion is highly injurious. This acid enters (into combination with the alkalies, with earths, ind metallic oxides, and forms with them those [salts called carbonates.

The ea ill) carbimaies are insoluble in water. Hence [breathing into . ph *l < f lime-water renders it turbid. Thus [lime- water is a g'>od lesl for the presence of carbonic acid.

Carbonic acid gas is found in abundance in warn natural Iwat-rs. Those of Pvrm mi, Spa, and S Itzer, are instances ^ the last particular!) is highl) impregnated with this acid.

M. Sauware, iun. found by experiment that an atmosphere containing even an eighth pari of carbonic, acid aid9 the growth of vegetables, but that when in a larger proportion it is inju- rious.

Exp. 1. — To a glass of water, suspected to contain car- bonic acid, add a small quantity of any of the other acids. If carbonic acid be present, it will become visible by a spark- ling appearance on the sides ol the glass and surface of the fluid.

Exp l2. — Place a lighted wax taper within a narrow glass jar. ihen take ;» jar or phial of carbonic acid gas, and cautious- ly pool it into (he jar containing the taper. This being an oi- visible gas, the op< rator will appear to invert merely an empty vessel, though the taper will be as effectually and in- i too si) extinguished as if water its- If bad been used.

Exp. 3. — Fdl ajar with carbonic aekl gas, then pour into It a small quantity of a solution of caustic potash, or soda; and having tied the month over with a wetted bladder, move is< 1 so as to spread the alkali over its inner surface, when a vacuum will be quickly formed hy the absorption ot the gas, whtch will appear by the bladder being pressed in- wards by the weight oi the atmosphere. If this experiment be made in a glass vessel, its inner surfac will be seen co- vt red with crystals of the alkali, as the carbonic acid always promotes the crystallisation of the fixed alkalies,

247. Phosphoric acid is a compound of oxy- gen and a peculiar substance called phospho- rus. It was formerly procured only by burn- ing phosphorus in oxygen gas ; but since it is known that this acid is a component part of animal bones, we now procure it from that source.

104 THE ACIDS. [C/i. 7.

When animal bones are divested of their oil and jelly, the earth which v mains is chiefly lime, united with phosphoric acid, and this phosphate of lime is often employed for the preparation of tin- medicinal salt called phosphate of soda But Mons. Chapial,jun. son of the Count Chaptal, employs bones in Paris, as I am informed, in a very different manner. Having a large establishment for the preparation of soda hi which process a larger quantity of muriatic acid is afforded ' than can be consumed in the ordinary way, he emplovs per- sons to collect bones from all parts of the city, and digests them in this