IN THE CUSTODY Or THE
BOSTON PUBLIC LIBRARY.
SHELF N°
•T^'
/
/
CHEMICAL ESSAYS,
B Y
R. WATSON, D.D. F.R.S.
AND REGIUS PROFESSOR OF DIVINITY IN THE UNIVERSITY OF CAMBRIDGE,
V O L. I,
THIRD EDITION.
L O N D O N:
PRINTED FOR T. EVANS, PAT ERNOSTER-ROW.
MDCCLXXXiy.
T O
HIS GRACE
THE
DUKE OF RUTLAND,
My Lord Duke,
YOUR Grace, whllft I had the honour of being in- trufted wkh your Education In this place, fliewed a difpofition to the Study of Chemiftry : I wifli that any thing contained In the a z fol-
( " )
following Eflays may tend t® revive it.
Chemiftry is cultivated abroad by perfons of the firft Rank^ Fortune, and Ability; they find m it a never falling foiirce of honourable amufement for their private hours ; and as public men, they confider its cultivation as one of the moft certain means of bringing to their utmoft perfedion, the manufadlures of their country.
That
C iil )
That your Grace's private life may continue to be bleffed with every domeftic con^fort ; an.d that your public life may be diftinguifhed by principles and aftions ufeful to your country, and honourable to yourfelf, is the fincere prayer of
Your Grace's
Moft affeftionate
And obliged Servant,
Cmnbridge^ Feb» 20, 1 78 1.
R. WATSON.
PREFACE.
THE fubjefts of the following EfTays have been chofen, not fo much, with a view of giving a Syftem of Chemiftry to the world, as with the humbler defign of convey- ing, in a popular way, a general kind of knowledge, to perfons not much verfed in chemical inquiries.
Two other volumes, which are nearly ready for the prefs, would finilh the whole of my plan; but being quite doubtful how far either the fubjedt itfelf, or at leall, how far the manner in which I have been able to treat it, may be acceptable to the Public, I dare not at prefent venture to folicit the Reader's atten- tion
PREFACE.
tion to them : If they fhould never fee the light, the world will fufFer little lofs ; and as to the trouble and cxpence which I have been at in compofmg them, they are more than compenfated by the knowledge I have gained.
There are two fets of men of whom I particularly crave indul- gence — Chemifts, and Divines. Chemifts muft excufe me, as well for having explained common mat- ters, with what will appear to them a difgufting minutenefs, as for hav- ing paffed over in filence fome of the moil interefting queflions : fuch are thofe which refped the analyfis of air and fire, the produdion and tranfmutation of faline fubflances, the fpontaneous deftrudlion and ge- neration of minerals.
Divines^j
P R E F A C E.
Divines, I hope, will forgive me, if I have ftolen a few hours, not, I trull, from the duties of my office, but certainly from the ftudies of my profeffion, and employed th^m in the cultivation of natural philofophy : I could plead in my defence the example of fome of the greateil characters^ that ever adorned either this Univerfity or the Church of England. The books of Nature and of Revelation equally elevate our conceptions, and incite our piety 3 they mutually illufirate each other ^ chey have an equal claim to our regard, for they are both written by the finger of the one eternal
INCOMPR cHENSIBLE G C D, TO
whom be glory for ever_j
Amen,
Ear
PREFACE.
For the miftakes I may have fallen into in treating of fuch a variety of matter, and for the imperfedion in the defign and execution of the "Work itfelf, I generally intreat the Reader's excufe in the words of Pliny,
Occupatifumus oficiis^ Juhfedvifque horis ifta curamus.
CON-
CONTENTS.
ESSAY
L On the Ri/^ and Progrejs of Che-- miftry Page i
II. On the principal Terms and Opera- tions ufed in Chemijiry* 49 ill. Of f aline Subftances, 109
IV. Of Fire y Sulphur ^ and PhUgifton^
149
V. Of the Origin of Subterraneous Fires. 181
VI . Of Vitriols^ andthereptittd'Trafif- mutation of Iron into Copper, 208
VII. Of Nitre or Saltpetre^ and the Application of its Acid to the In-
fiammation of Oils and the Con- gelation of ^ickfilver, 247 VIII. Of
CONTENTS.
VIII. Of the Manner of making Salt- petre in Europe^ and of its Ge- neration, 283
iX. Of the Manner of making Salt-
petre in the Eaft Indies. 313
X. Of the Time when Gunpowder
*u^as difcovered, 327
ESSAY
X
ESSAY
ON THE RISE AND PROGRESS OF CHEMISTRY,
^f^HE beginnings of every art, Jl which tended either to fupply the neceflitiesj or to alleviate the more preffing inconveniences of hu- man life, v.^ere probably coeval with the firft eilablifhment of civil fo- cietieSj and preceded by many ages, the invention of letters, of hieroglyphics, and of every other mode of tranfmitting to pofterity the memory of pail' tranfadions* In vain iliall we inquire who in- vented the firil plough, baked the
VOL. I, A fti*^
( i )
firfl bread, fhaped the firft pot, wove the firft garment, or hollowed out the firft canoe. Whether men were ori- ginally left, as they are at prefent, to pick up cafual information concern- ing the properties of bodies, and to inveftigate by the Ilrength of natural genius the various relations of the obje6ts furrounding them; or were, in the very infancy of the world, fu- pernaturally affifled in the difcovery of matters efTential, as it fhouldfeem, to their exiftence and veil-being, muft ever remain unknown to us.
There can be little doubt that in the fp ace of, at leaft, 1656 years, from the creation of the world to the deluge, a greatvariety of economical arts muft have been carried to a very confiderable degtee of perfedtion. The knowledge of many of thefe pe-
rifhed.
//
( 3 )
rilhed, in all likelihood, with the then inhabitants of the earth; it be- ing fcarcely poflible for that fingle family which efcaped the general ruin to have either pradlifed, or been even fuperficially acquainted with them all. When men have been long united in civil focieties, and human nature has been exalted by a reciprocal communication of knowledge, it does not often hap- pen, that any ufeful invention is in- tirely loft : but were all the prefent inhabitants of the earth, except eight perfons, to be deftroyed by one fudden calamity, v/ho {cqs not that moft of thofe ferviceable and elegant arts, which at prefent confti- tute the employment, and contri- bute to the happinefs of the greateft part of the human race, would pro- A 2 bably
( 4 ) bably be buried in long oblivion ? Many centuries might flip away, before the new inhabitants of the globe would again beconne ac- quainted with the nature of the com- pafs, with the arts of painting, print- ing, or dying, of making porcelane, gun-powder, fleel, or brafs.
The interval of time which elapfed from the beginning of the world to the firfl deluge, is reckoned by pro- fane hiftorians, to be wholly uncer- tain as to the events which happen- ed in it: it was antecedent, by many centuries, not only to the sra when they fuppofed hiftory to commence, but to the moft cdilant ages of he- roifm and fable. The only account relative to it^ which we can rely upon, is contained in the firil: fix chapters of the book of GenefiSj three of which being employed in
the
( s )
the hiilory of the creation, and of the fall of manj and a fourth con- taining nothing but a genealogical narration of the patriarchs from Adam to Noah; it cannot reafon- ably be expeded, that the other two ihould enable us to trace the various, fleps by which the human intelle6t advanced in the cultivation of arts. and fciencesj. or to afcertain, with: much precifion, the time when any of them was firfl: introduced into the. world. It is fomewhat remarkable that from this account,, fhort as it is,, the chemifts lliould be authorized, with fome propriety, to exalt the antiquity of their art to the earlicil times. Tubal-caini5 there mention- ed as an infirudtor of every artificer in copper and iron*.. This circum- ftance proves beyond difpute^ that. A 3 one-
* Gen. iy, iz^.
( 6 )
one part of metallurgic chemiflry
was well underftood at that time, for copper and iron are of all the metals mod difficultly extraded from their ores, and cannot, even in our days, be rendered malleable without much {kill and trouble ; and it proves alio that the arts in general were in an improved ftate amongft the antedi- luvians. It is faid, indeed, that fome tribes of Hottentots (v/ho can have no pretenfions to be ranked amongft the cultivators of the arts) know how to melt both iron and copperf; but this knowledge of theirs, if they have not derived it from an inter^ courfe with the Europeans, is a very extraordinary circumftance, fince the mxclting and manufadluring of metals are juftly confidered, in ge- neral^ t Former's Voy. Vol. I. p. 8i.
( 7 )
neral, as indications of a more ad- vanced ftate of civilization than the Hottentots have yet arrived at. But not to dwell upon this ; Cain we know built a city^ and fome would thence infer that metals were in ufe before the time of Tubal-cain, and that he is celebrated principally for his ingenuity in fabricating them for domefiic purpofes. Hiftory feems to fupport our pretenfions thus far. As to the opinion of thofe who, too zealoully contending for the dignity of chemiflry, make the difcovery of its myfteries to have been tliG pretium amoris which angels paid to the fair daughters of men, we in this age are more difpofed to apo- logize for it than to adopt it. We may fay of arts what the Roman hiftorian has faid of flates — datur A 4 h^ec
( 8 )
h£c venia antiquitati^ uty mijcendohu- mana divinisy primordia artium au- gufiiora faciat §.
For many ages after the flood we have no certain accounts of the ftate of chenaiftry. The art of making wine indeed, was known, if not be- fore, foon after the deluge; this may be collected from the intoxicatioa of Ncah||, there being no inebriat- ing quality in the unfermented juice of the grape. The Egyptians were ikilled in the manufacturing of me- tals, in medicinal chemiilry, and in the art -of embalming dead bodies, long before the time of Mofes, as appears from the mention made of Jofeph's cup *, and from the phyfi-^ cians being ordered to embalm the body of Jacob f. They pradifed
alfo § Livy*s Praef. 1| Gen, ix. 21, * Gen. xiiv. 2. f Gea. 1. 2<»
• ( 9 )
alfo the arts of dying and of making
coloured glafs at a very early pe- riod 5 as has been gathered, not only from the teftirpony of Strabo, but from the relics found with their mummies, and from the glafs beads with which their mummies are fometimes Hudded §. But we cannot from thefe inilances conclude that chemiilry v/as then cultivated as a feparate branch of fcience, or di- ftinguifhed in its application, from a variety of other arts which mull have been exercifed for the fupport and convenience of human life. All of thefe had probably fome depend- ance on chemical principles, but
they
§ See Deleval's ingenious Inquiry into the. Caufe of the Changes of Colours, Pref. i \ i : and Duten's learned Inquiry into the Drl-i coveries attributed to the Moderns, p. 241 •
( 10 )
they were then, as they are at pre- fent, pradifed by the feveral ar- tifts without their having any theo- retical knowledge of their refpec- tive employments. Nor can we pay much attention in this inquiry to the obfcure accounts which are given of the two great Egyptian philofo- phers, Hermes the elder, fuppofed to be the fame with Mizraim grand- fon of Noah; and Hermes furnamed Trifmegiftus the younger, from whom chemifliry has by fome beea affededly called the Hermetic art.
The chemical fldll of Mofes dif- played in his burning, reducing to an impalpable powder, and render- ing potable the golden calf in the wildernefs, has been generally ex- tolled by writers on this fubjetl; and conilantly adduced as a proof of the
then
( II )
then flourifhing ftate of chemiftry amongft the Egyptians, in whofe learning he is faid to have been well verfed. If Mofes had really reduced the gold of which the calf confided, into afhesj by calcining it in the fire ; or made it any other way folu- ble in water, this inllance would have been greatly in point ; but nei- ther in Exodus nor in Deuteronomy where the fa6b is mentioned, is there any thing faid of its being difTolved in water. The enemies of revelation on the other hand, conceiving it to be impofTible to calcine gold, or to render it potable, have produced this account as containing a proof of the want of veracity in the facred hiftorian. Both fides feem to be in an error; Stahl and other chemifls have fhewn that it is poiTible to make
gold
C 12 )
gold potable, but we have no rea- fon to conclude that Mofes either ufed the procefs of Stahl, or any other chemical means for eftefting. the purpofe intended — he took the calf which thsy had made ^ and burnt it in the fire ^ and ground it to powder ^ and ftrewed it upon the water ^ and made the children of Ifrael to drink of it *. Here is not theleaft intimation given of the gold having been dlflblved^ chemically fpeaking, in watery it was llamped andground^or, as the Arabic and Syriac verfions have it;, filed into- a fine dull;, and thrown into the river of which the children of Ifrael ufed to drink : part of the gold would remain, notw-ithftanding its greater fpecific gravity, fufpended foratime^ (as happens in the wafhing of cop- per * Exod. xxxii. 20..
( 13 )
per and lead ores,) and might be ■Iwallowed in drinking the water, the reft would fmk to the bottom, or be carried away by the flux of the ftream.
Never thelefs, though nothing fa- tisfadlory can be concluded concern- ing the Egyptian chemiitry from what is faid of Mofes in this in- ftance, yet the ftrudure of the ark, and the fafliion of Aaron's garments, clearly indicate to us that the arts of manufaduring metals, of dying lea- ther red and linen blue, purple, and fcarlet; of diftinguiihing preci- ousftones, and engraving upon them, were at that time pradifed in a very ■eminent degree *. The Ifraelites 'had unqueftionably learned thefe arts in Egypt, and there is great rea-
fon ^ -Exod, xx;Yi. and xxv-iii*
( 14 )
fon to fuppofe not only that learning of every kind firil flourifhed in Egypt, but that chemiftry, in parti- cular, was much cultivated in that country when other fciences had palTed into other parts of the world. Pliny in fpeaking of the four periods of learning which had preceded the times in which he lived, reckons the Egyptian the firft: and Suidas, who is thought to have lived in the tenth century, informs us that the Empe- ror Diocletian ordered all the books of chemiftry to be burned, left the Egyptians learning from them the art of preparing gold and filver, ihould thence derive refources to op- pofe the Romans *. It is worthy of notice that Suidas ufes the word chemiftry in a very reftridled fenfe,
when Lexicon, Vox Xrjy,ugc»
( IS )
when he interprets it by — the pre- paration of gold and filver; — but all the chemifts in the time of Suidas, and for many ages before and after him, were alchemifts. The edi6t of Diocletian in the third century, had little efFed in reprefling the ardour for this ftudy in any part of the world, fince we are told that not lefs than five thoufand books, to fay nothing of manufcripts, have been publilhed upon the fubjed of al- chemy fince his time *.
At what particular period this branch of chemillry, refpe6i:ing the tranfmutation of the bafer metals into gold, began to be diftinguifhed by the name of alchemy, cannot be determined. An author of the fourth century, in an aftrological
work, '^ Chem, Waller, p, 40.
C i6 )
work, fpeaks of the fcience of al- chemy as well underftood at that timei and this is faid to be the firft place in which the word alchemy is ufed *. But Voffius aflerts that we ought in the place here referred to mi^G3,d of alcbemia to read cbemia-f:, be this as it may, we can have no doubt ofalchemia being compound- ed of the Arabic a I (the) and chemia^ to denote excellence and fuperiority, as in al-manack, al-koran, and other words. Whether the Greeks in- vented, or received from the Egyp- tians, the do6lrine concerning the tranfmutation of m.etals, or whether the Arabians were the firil: who pro- feffed it, is uncertain. To change
iron,
* Jul. Fermi. Mater. Aftronomicon. LiU c. 15. f Vof&, Etymo, Vox Akhemia,
3. c. 15
( 17 ) iron, lead, tin, copper, quickfilver
into gold, feems to be a problem
more likely to aninaate mankind to
attempt its folution, than either that
of fquaring the circle, or of finding
out a perpetual motion ; and as it
has never yet been proved, perhaps
never can be proved to be an impof-
fible prohleniy it ought not to be ef-
teemed a matter of wonder, that
the firft ch-emical books we meet
with, are almoft intirely employed
in alchemical inquiries.
Chemiftry, with the reft of the fciences, being banifhed from the other parts of the world, took re- fuge among the Arabians. Geber in the feventli, or as fome will haVe It in the eighth, and others in the iiinth century, wrote feveral chemi- •cal or rather alchemical books in
VOL, u B Arabic.
C js )
Arabic. In thefe works of Geber are contained fuch ufeful diredtions concerning the manner of conduc- ing diilillation, calcination, fubii- mation, and other chemical opera- tions, and fuch pertinent obferva- tions relpeding various minerals, as juflly feem to entitle him to the cha- rader, which fome have given him, of being the father of chemi'ftry; though, in one of the moil celebrated of his works, he modeftiy acknow- ledges himfelf to have done little clfe than abridge the dodrine of the ancients concerning the tranfmuta- tion of metals *. Whether he was
pre-
* Totam noflram metallorum tranfinu- tandorum fcientiam, quam ex libris antiquo- rum philolbphorum abbreviavimus, tompi- latione diverfa, in noilris vohiminibus, hie in unam fumman redegimus. Gebri Alch, cap. I. edition by Zetzner in 1512. In Tancken*s edition in 1681, the words me- tallorum tranfinutandorum are omitted.
t ^ )
J)receded by Mefue and Rhazes^ or followed by them, is not in the pre- fcnt inquiry a matter of much im- portance to determine^ frnce the forementioned phyficians as well as Avicenna, who, from all accounts, was pofterior to Geber, fpeak of many chemical preparations^ and thus thoroughly eftablifh the opini- on, that medical chemiftry, as well as alchemy, was in thofe dark ages well underftood by the Arabians.
Towards the beginning of the thirteenth century Albert the great in Germany^ and Roger Bacon in England, began to cultivate che- miftry with fuccefs, excited there- to, probably, by the perufal of fome Arabic books, which about that time were tranflatcd into Latin. Thefc two monks, efpecially the B 2 latter,
( 20 )
latter, feem to have as far exceeded the common ftandard of learning in the age in which they lived, as any philofophers who have appeared in any country either before their time or fmce. They were fucceeded in the fourteenth and fifteenth centu- ries, by a great many eminent men both of our own country and fo- reigners, who, in applying them- felves to alchemy, made, inciden- tally, many ufeful difcoveries in va- rious parts of chemiftry : fuch were Arnoldus de Villa Nova in France; our countryman George Ripley; Raymund Lully of Majorca, who iirll introduced or at ieaft more largely explained the notion of an univerfal medicine; and Bafile Va- lentine, vv^^iofe excellent book inti^ tied Currus Antimonii triumphalisy has contributed more than any thing
clfe
( 21 )
elfe to the introdndion of that mofl: ufeful mineral into the regular prac- tice of moil phyficians in Europe y it has given occafion alfo to a va- riety of beneficial, as well as (a cir- cumftance which might be expe6l- cd, when fo tickliih a mineral fell in- to the hands^ of interefted empirics) to many pernicious noftrums. To this, rather than to the arrogant fe- verity with which Bafile Valentine treats the phyficians his cotempora- ries, may we attribute the cenfure of Boerhaave, who, in fpeakingof him, fays, " he erred chiefly in this, that he commended every antimonial preparation, than which nothing can be more foolifh, fallacious, and dangerous ; but this fatal error has infc6led every medical fchool from that time to this f." The
t Boerh. Ch. Vol. I. p. i8.
( 22 )
The attempting to make gold jDf filver by alchemical proccfles had been prohibited by a conftitution of Pope John the xxii, who was ele- vated to the pontificate in the year 1316 *; and within about one hun- dred and twenty years from the death of friar Bacon, the nobility and gen^ try of England had become fo infa- tuated with the notions of alchemy, and wafted fo much of their fub- ilance in fearch of the philofopher^s Hone, as to render the interpolition of government neceiiary to reftrain their folly. The following a6t of parliament, which lord Coke calls the fhorteft he ever met with. Was paiTed 5 H. 4. *^ None from hence- forth ihall ufe to multiply gold or filver, or ufe the craft of multiplica-
tion^ * Kirch. Miin. Sub. L« xi, Seft. iv* c. i*
( ^3 )
tion, and if any the fame do, he fliall
incur the pain of felony." It has been fuggelled, that the reafon of pafTing this ad; was not an appre- henfion left men Ihould ruin their fortunes by endeavouring to make gold, but a jealoufy left government fhould be above af^ing aid of the fubjed. " After Raymund Lully, and Sir George Ripley, had fo large- ly multiplied gold, the lords and commons, conceiving fome danger that the regency, having fnch im- menfe treafure at command, would be above afking aid of the fubjed, ,and might become too arbitrary and tyrannical, made an ad againft mul- tiplying gold and filverf," This a6t, whatever might be the occafion of pafTing it, though it gave fome B 4 ob-
f Opera Mineralia explicata, p. lo.
( 24 ) obftrudlion to the public exercife of alchemy, yet it did not cure the dif- pofition for it in individuals, nor re- move the general credulity; for in the 35 H. 6, Letters Patent were granted to feveral people, by which they were permitted to inveftigate an iinivcrfal medicine, and to perform the tranfmutation of metals into real gold and filver, with a non-obftantc of the forementioned ftatute, which remained in full force till the year 1689, when being conceived to ope- rate to the difcouragement of the melting and refining of metals, it was formally repealed *. The
* Mr. Boyle is faid by liis irrtereft fo have procured the repeal of this lingular ftatute, and to have been probably induced thereto^ in confeqence of his having been perfuaded of the poffibility of the tranimutation of me- tals into gold. See his life prefixed to the folio ed. of his works, p. 83.
(25 )
The beginning of the fixtecnth century was remarkable for a great revolution produced in the Europe- an pradice of phyfic, by means of chemiftry. Then it was that Para- celfus, following the fteps of Bafile Valentine, and growing famous for curing the venereal difeafe, the le- profy, and other virulent diforders> principally by the means of mercu- rial and antimonial preparations, wholly rejedled the Galenical phar- macy, and fubftituted in its ftea<l the chemical. He had a profefTor's chair given him by the magiftracy of Ba:- fil, was the firft who read public lec- tures in medicine and chemiflry, and fubjeded animal and vegetable as well as mineral fubftances to aa examination by fire.
It feldom happens that a man of but common abilities, and in the
moft
( 26 )
moft retired fcenes of life, obferves fuch a flrift uniformity of condu(5l^ as not to afford prejudice and par- tiality fufficient materials for draw- ing his charader in different colours ; but fuch a great and irregular genius as Paracelfus, could not fail of be- coming alike, the fubjedt of the ex- tremes of panegyrick and fatire. He has accordingly been efteemed by fome, a fecond Efculapius; others have thought that he was poffefTed of more impudence than merits and that his reputation was more owing to the brutal Angularity of his condu6b> than to the cures he performed. He treated the phyficians of his time, with the moft fottiili vanity and il- liberal infoience; telling them, that the very down of his bald pate had more knowledge than all their wri- ters^,
( ^7 );
tcfs,- th)5 buckles of his fhoes more learning than Galen or Avicenna, and his beard more experience than all their univerfities *. He revived the extravagant dodlrine of Ray- mund Liilly, concerning an univer- fal medicine, and untimely funk into his grave at the age of forty-feven, whilft he boafted himfelf to be m poffefTion of fecrets able to prolong the prefent period of human life to that of the Antediluvians,
But in whatever eftimation the merit of Paracelfus as a chemift may be held, certain it is, that his fame excited the envy of fome, the emu- lation of others, and the induftry of alL Thofe who attacked, and thofe who defended his principles, equally
promoted
■^ Preface to his book entitled Paragranum, where there is more in the fame ll:yle.
C ^8 )
promoted the knowledge of che-
miflry; which from his time, by attrafting the notice of phyficians^ began every where to be fyftemati- cally treated, and more generally underllood.
Soon after the death of Paracelfus^ which happened in the year 1541^ the arts of mining and fluxing me- tals, wbich had been pradtifed in moft countries from the earlieft times, but had never been explain- ed by any writers in a fcientific man- ner, received great illuflration from the works of Georgius Agricola, a German phyfician. The Greeks and Romans had left no treatifes worth mentioning upon the liibjeft, and though a book or tv/o had appeared in the German language, and one in the Italian, relative to metallurgy,
before
( 29 )
before Agricola publifhed his twelve books De Re Metallicay yet he is juftly efteemed the firft author of re- putation in that branch of chemiftry. Lazarus Erckern (afTay-mafler general of the empire of Germany) followed Agricola in th€ fame pur- fuit. His works were firft publifh- ed at Prague m 1574, and an En- gliih tranflation of them by Sir John Pettus, came out at London ia 1683. The works of Agricola and Erckern are ftill highly efteemed, though feveral others have been publiftied, chiefly in Germany, upon 4;he fame fubjed fmce their time. Amongft thefe we may reckon 'Schindler*s Art of Aflaying Ores and Metals i the metallurgic works of Orfchall; the works of Henckcll; ofSclutterj of Cramerj of Lehman;
and
( 30 ) and of Gellert-. Germany, indeed> iias for a long time been the great fchool of metallurgy for the reft of Europe; and we, in this country, owe the prefent flourifhing condi- tion of our mines, efpecially of our copper mines, as well as of our brafs manufadtory, to the wife policy of queen Elizabeth, in granting great privileges to Daniel Houghfetter, .Chriftopher Schutz, and other Ger- mans ; whom fhe had invited into England, in order to inftru6t her fubjedts in the art of metallurgy.
It was not, however, till towards the middle of the laft century, that general chemiftry began to be culti-- vated in a liberal and philofophical manner. So early as the year 1645 feveral ingenious perfons in London, in order to divert their thoughts
from
C 31 )
from the horrors of the civil war which. had then broken out, had formed themfelves into a fociety, and held weekly meetings, in which they treated of, what was then called, the new or experimental philofo- phy. Thefe meetings were conti- nued in London till the eftablifh- ment of the Royal Society in 1662; and before that time, by the re- moval of fome of the original mem- bers to Oxford, fimilar meetings were held there, and thofe ftudies brought into repute in that univer- lity. Mr. Boyle, who had entered tipon his chemical ftudies about the year 1647, was a principal per- fon in the Oxford meetings: he publifhed at that place his Scepti- cal Chemift, in 1661, and by his various writings and experiments
greatly
( 32 )
:grcatly contributed to th« intro- 4ucing into England, a tafle for ra- tional chemiftry.
Next to Boyle, or perhaps before him as a chemift, ftands his cotem- porary the unfortunate Beccher, whofe Fhyfua Suhterranta^ j^ft^y i^^- titled opus fine fariy was firll pub- lifhed in 1669. After having fuf- fercd various perfecutions in Ger- niany, he came over into England, and died at London in 1682, at the age of 57 . He refided fome time be- fore his death in Cornwall, which he calls the mineral fchool, owning that from a teacher, he was there become a learner. He was the au- thor of many improvements in the manner of working mines, and of fluxing metals; in particular he firll introduced into Cornwall the me- thod
( 33 )
thod of fluxing tin by means of the fiame of pit-coal, inftead of wood or charcoal *.
Lemery's very accurate courfe of pradtical chemiftry appeared in
1675.
* Beccher wrote his Alphabethum Mine- rale, at Truro in Cornwall, in 1682, not long before his death. In his dedication of this tra6t to Mr. Boyle, he has the following words : — " ignis ufus, ope, flammarum li- thantracum ilannum et mineralia fundendi, Cornubiae hadtenus incognitas, fed a me in- trodu6tus." — This account which Beccher gives of himfelf, is not quite agreeable to what is advanced by an author every way qualified to come at the truth of this mat- ter.— " Neceffity at lait fuggelled the in- troduftion of pit-coal for the Imelting of tin ore; and among others, to Sir Bevil Gran- ville of Stow in this county, temp. Car. I. who made feveral experiments, though with- out fuccefs ; neither did the effectual fmelt- ing of tin ore with pit-coal, take place till the fecond year t)f Queen Anne." Pryce's Miner. Cornub. p. 282. VOL. I, C
( 3+ ) i6j^, Glauber's works had been
publiflied at different times, from 165 1 to 166 1, when his trad, enti- tled Philofophical Furnaces, came out at Amfterdam. Kunckel died in Sweden in 1702; he had prac- tifed chemiftry for above 50 years, under the aufpiccs of the Eledor of Saxony, and of Charles XI. of Swe- den. He wrote his chemical obfer- vations in the German language, but had them tranflated into Latin in the year 1677; the tranflation is dedicated by its author to our Roy- al Society. They were afterwards tranflated into Englilh in 1704. Having had the fuperintendency of feveral glafs-houfes, he had a fine opportunity of making a great va- riety of experiments in that wayj and I have been informed by our
ena-
( 3S )
cnamellers, and makers of artificial gems, that they can depend more upon the procefTes and obfervations of Kunckel, than of any other author upon the fame fubje6b. The chemi- cal labours of thefe and many other eminent men, too numerous to men- tion, were greatly forwarded by the eftablilhmcnt of feveral focieties, for the encouragement of natural philofophy, which took place in various parts of Europe about that period.
The Philofophical Tranfa6cions at London, the Hifloire de V Aca- demie Royale des Sciences at Paris, the Saggi d' Efperienze di Acad, del Cimento at Florence, the Journal des Scavans in Holland, the Ephe- merides Academic Nature Curio- forum, in Gernaany, the A6ls of the C 2 Academy
( 36 )
Academy of Copenhagen, and the
A6ta Eruditorum at Leypfic; all thefe works began to be publifhed within the fpace of twenty years from 1665, when our Royal So- ciety firft fet the example, by pub- iifliing the Philofophical Tranfac- tions. To thefe may be added, the works of the Academies of Berlin, Peterfbiirgh, Stockholm, Upfal, Bononia, Bourdeaux, Montpelier, Gottingen, and of feveral others which have been eftablilhed within the courfe of the prefent century. Near a thoufand volumes have been publifhed by thefe learned focieties within lefs than 120 years. The number of fads which are therein related refpecSting chemiftry, and every other branch of natural philo- fophy, is exceedingly great 5 but the
fubjedl
■( 37 ) fubje^l Is dill greater, and muft for ever mock the efforts of the human race to exhauft it. Well did Lord Bacon compare natural philofophy to a pyramid ! Its bafis is indeed the hiftory of nature, of which wc know a little, and conjedure much; but its top is, without doubt, hid high among the clouds; it is " the work which God morketh from the beginning to the endy' infinite and infcrutable.
By the light which has been in- cidentally thrown upon various parts of chemillry from thofe vaft undertakings of public focicties, as well as from the more exprefs la- bours of Stahl, Newman, Hoffman^ Juncker, Geoffry, Boerhaave, and of many others equally worthy af cam- mendation; by the theoretic con- ciufions and fyftematic divifions C J which
( 38 )
which have been introduced into it j
from the didadlic manner in which the fludents of this art have been inflru6led in every medical fchooU chemiflry has quite changed its ap- pearance. It is no longer confi- dered merely in a medical view, nor reflridled to fome fruitlefs ef- forts upon metals ; it no longer at- tempts to impofe upon the credulity of the ignorant, nor afFe6ts to afto- nilh the fimplicity of the* vulgar by its wonders, but is content with ex- plaining them upon the principles of found philofophy. It has fhaken t)ff the opprobrium which had been thrown upon it, from the unintelli- gible jargon of the alchemifts, by revealing all its fecrets in a lan- guage as clear and as common, as the nature of its fubjeds and opera- tions will admit, Cpn>
( 39 )
Confidered as a branch of phy-
ficksj chcmiilry is but yet in its in- fancy ; hov/ever, the mutual emu- lation and unwearied endeavours of fo many eminent men as are in every part of Europe engaged in its cultivation, will in a little time ren- der it. equal to any part of natural phiiofophy, in the clcarnefs and fo- lidity of its principles. In the uti- lity refulting to the public from its conclufions, with refped to the practice of medicine, of agricul- ture, arts and manufactures of every kind, it is even in its prefent ftate inferior to none.
The ufes of chemiflry, not only in the medical, but in every econo- mical art are too extenfive to be enumerated, and too notorious to want illuftration^ it may juft be ob- C 4 ferved.
( 40 )
ferved, that a variety of manufac- tures, by a proper application of chemical principles, might, proba- bly, be wrought at a lefs expence, and executed in a better manner than they are at prefent. But to this improvement there are impe- diments on every hand, which can- not eafily be overcome. Thofe who by their lituations in life are re- moved from any defign or defire of augmenting their fortunes by making difcoveries in the chemical arts, will hardly be induced to di- minifh them by engaging in expen- five experimental inquiries, which not only require an uninterrupted atention of mind, but are attended with the wearifomenefs of bodily la- bour. It is not enough to employ operators in this bufinefs s a man muft
blacken
C 41 )
blacken his own hands with char- coalj he muil fweat over the furnace, and inhale many a noxious vapour l)efore he can become a chemift. On the other hand, the artifts them- felves are generally illiterate, timid,, and bigotted to particular modes of carrying on their refpedlive opera- tions. Being unacquainted with the learned, or modern,, languages, they feldom know any thing of new dis- coveries, or of the methods of work- ing pradifed in other countries. De- terred by the too frequent, but much-to-be lamented examples of thofe, who, in benefiting the public by projects and experiments, have ruined themfelves, they are unwil- ling to incur the leaft expence in making trials, which are uncertain with refped to profit. From this ap-
prchenfion^
( 42 ) prehenfion^ as well as from the myf- tcrious manner in which moil arts, before the invention of printing, and many ftill continue to be taught, •they acquire a certain opinidtrete, which efFedually hinders them from making improvements, by depart- ing from the ancient traditionary precepts of their art. It cannot be queftioned, that the arts of dying, painting, brewing, diftilling, tan- ,ning, of making glafs, enamels, porcelane, artificial ftone, common fait, fal ammoniac, falt-petre, potafh, fugar, and a great variety of others, have received much improvement from chemical inquiry, and are ca- pable of receiving much more.
Metallurgy in particular, though one of the moft ancient branches of chemiftry, affords matter ^aough for
new
( 43 )
new difcoveries. There are a great many combinations of metals which have never been madcj many of which, however, might be made, and in fuch a variety of proportions, .as, very probably, would furnifh us with m.etallic mixtures more fer- viceable than any in ufe. The me- thod of extrading the greateft pof- liblc quantity of metal from a given quantity of the fame kind of ore, has, perhaps, in no one inftance been afcertained with fufBcient preciiion. There are many forts of iron and copper ores which cannot be con- verted into malleable metals, with- out much labour, and a great ex- pence of fuel } it is very probable, that by a well-condu6i:ed feries of experiments, more compendious ways of working thefe minerals
might
( 44 ) might be found out. In our own times three new metallic fubftances have been difcovered*, and their properties abundantly afcertained by experiment; and it may reafon- ably be conjedtured, that future ex- perience will yet augment their number. Till Marggraf fhewed the manner of doing it, no metallic fub- ftance could be extradled from ca- lamine, and all Europe was fupplied with zinc f either from India or from Germany. A manufactory of this metallic fubflance has not many years ago been eflabliihed in our own country, and the copper works near Briftol have fupplied Birming- ham
* Platina^ Regulus of Cobalt, Nickel.
f Zinc is a metallic fubflance, of the co« lour of lead J when united with copper, it conftitutes brafs, pinchbeck, and other me* tallic mixtures -refembling gold.
( 45 )
ham with zinc extrafted from ca- lamine. Black-jack was not long fincc employed in Wales for mend- ing the roads -, its value is not yet generally known in Derbyfhire ; but it is now well underftood by fomc individuals to anfwer the purpofe of calamine for the making of brafs *. Monf. Von Swab in 1738 was, I be- lieve, the firft perfon who difcilled zinc from black-jack f 3 and a work ' which he eredled, probably gave the hint to the cftabliihers of our En- gliih manufadlory: indeed, I have been well informed, that they pur- chafed the fecret from him when he
was
* T%e cobalt ores in Hefle, which at pre- fent produce a net profit of about 14000I. a- year, were formerly ufed for the fame pur* pofe as black-jack was lately in Wales.— Bom's Travels by Rafpe, Pre. xxvi.
f Croniledt's Miner, Sec. 231.
( 46 )
was in England. The various kinds of black lead, from which neither tin nor iron can at prefent be pro- cured to advantage; the mundicks, fome cobalt ores, cawk, kebble, and other mineral fubftances, which are now thought to be ufelefs, may fome time or other, perhaps, be applied to good purpofe. Cawk and kebble, which are found in great quantities in mining countries, efpecially in Derbyfhire, and which are univer- fally thrown away, may, perhaps, be nothing but different kinds of fpar, and deftitute of all metallic matter *i yet it may not be impro- per to remark, that the external ap- pearance of the yellowifti cawk is wholly fimilar to that of calcined
hlack^
* Sec Mr. Woulfe's ingenious Experi- ments in Philof. Tranf. 1779, p. 15.
( 47 ) Mack-jack, fhat it is much of the fame weight as black-jack, may- appear from the annexed table : Weight of a cubic foot of White cawk 4047 \ Yellow cawk 41 12 I Kebble 43^9 ) avoirdup. oz.
Black-jack 4093 I Water 1000 /
In a word, the improvement of metallurgy, and the other mechanic arts dependent on chemiftry, might beft be made by the public eftablilh- ment of an Academy, the labours of which fhould be dellined to that particular piirpofe. The utility of fuch eftablifhments has been expe- rienced in Saxony and other places; and as mines and manufaflures are to the full as important to us, as to any other European ftate, one may
hppc^
( 48 )
hope, that the conftituting a Chemi- cal Academy may, in times of peace and tranquillity, become an objedt not unworthy the attention of the King or the Legiflaturc of the Britifh nation*.
* The reader who vvilhes to become more fully acquainted with the hiliory of che- millry, may confult what Borrichius has faid in his Diflertation de Ortu et ProgrefTu Che- mise, publiflied at Copenhagen in 1668; and in his book entitled Hermetis, ^gyp- tiorum, et Chemicorum fapientia ab Her- manni Couringii animadverlionibus vindi- cata, publifhed at the fame place in 1674. He will alfo find fomething worth his notice on this fubjed in Boerhaave's Chemiftry ; and in a work of Wallerius, called, Chemiae Phyficae Pars Prima, publiflied at Stockholm in 1760; where there is an ufeful catalogue of the mofl: approved writers on the various parts of chemillry.
ESSAY
ESSAY n.
ON THE PRINCIPAL TERMS ANE) OPERATIONS USED IN CHEMISTRY. •
^f^HIS EfTay, in which I mean JL to give a general account of the principal terms and operations ufed in chemiftry, will, perhaps, be more troublefome to the reader, than any other which I ihall have occafion to write : but he muft not be dis- couraged^ nor conceive a difgufi: againft the fcience itfelf, from an inconvenience neceflarily attending all fciences. Chemiftry has as few technical terms belonging to it, as navigation, law, medicine, or any other art or fcience, which may have VOL. u D chanced
( 50 )
chanced to engage his attention* The more ancient chemifts, indeed, were fond of coining abftrufe terms, and frequent in the ufe of them; but this afFeftation is, at prefent, pretty generally and very juftly ex- ploded.
OF SOLIDITY AND FLUIDITY.
Though, in philofophical pro* pricty of fpeech, water be as folid a body as a diamond, yet in the com- mon acceptation of the word foli- dity, we confider it as oppofed to fluidity. Natural philofophers have agreed to call that principle, by which the conftituent parts of Hones, glafs, metals, and other fubftances cohere together, Attra^ion, They illuftrate the agency of this princi- ple, by a variety of decifive experi- ments 5
( s^ )
merits ; decifive as to the proof of the exiftence of fuch a power, but indicating nothing at all of the caufe of it. As the unknown principle t)f mutual attradlion between the conftituent parts of folid bodies, is the caufe of thcirjoliaityy fo the un- known principle of fire, is the caufe of their fluidi'tj, I call the princi- ple of fire unknown, becaufe^ tho* its effedls are fufficiently manifell, the caufe of it is wholly queftion- able. But in whatever manner fire may be fuppofed to exert its agen- cy, it feems to be the great inftru- mcnt of fliiidity upon thie furface of the earth. Without a certain degree of heat, water, fpirits of wine, oil, quickfilver, and perhaps the air it- felf, would be converted into folid bodies 3 and with a certain degree
D 2 of
( 52 )
of Keat all fluid bodies would be
changed into elaftic vapours, and all folid bodies would either be wholly diflipated, or in part diflipated, and in part converted into fluid glafs. Thefe are extreme cafes, to which no portion of the earth is obnoxious ; no climate is fo hot, but that it abounds with water in a fl:ate of flui- dity ; and none has yet been difco- vered fo cold, but that the air and the blood, of aquatic animals at leafl:, continue fluid in it.
OF VOLATILITY AND FIXITY,
The changes produced in bodies by the adion of fire arc various, ac- cording to the confl:itution of the bodies themfelves, and the degree of heat to which they are expofed. Some bodies, in a certain degree of
heat.
( S3 )
heat, may be wholly diffipated, others only in part, others not at all. Thus the fame degree of heat which will intirely difTipate camphor, and con- vert water into vapour, will only pro - duce a partial difperfion of the con- ftituent principles of turpentine, blood, or milki and will not effect any change or diminution of weighty in feveral woods, metals, earths^ falts, and oils. Thofe bodies whicli by heat fuffer no diminution of their weight, are faid to htfixedy and thofe which do lofe of their weight, arc faid to ht volatile -y and they are faid to be more or lefs volatile, according as a lefs or a. greater degree of heat 15 requifite for producing a fepara- tion of their parts. It is obvious>, that volatility belongs to moil bo- dies^ folid as. well as fluid \ fince the D 3 heat
heat of the atmofpherc is fufficient to diminilh the weight of many, and artificial applications of fuperior de- grees of heaty that of many more : but it is not certain, whether abfo- lute/^//j belongs to any body in na- ture, fince the fame body which is lixed in one degree of heat, may be- come volatile in another: thus dia^ mondsi which remain unchanged in 'Ji fmail degree of heat, may be wholly diflipated in open veflels by a great- er ; and gold, which can refift the moil violent fires excited in our fur- naces, without lofmg any thing of its v/eight, may not be able to fuilain tht fiercer adlion of the folar rays, when united in the focus of a large burning-glafs.
The fixity of bodies is not in pro- portion to their hardnefs, for a dia- mond
C 55 )
itiond is harder than a ruby> yet a dia- mond may be wholly difTipated by a degree of heat which produces no manner of change in a ruby. We are indebted to the Emperor Francis I. for this experiment. He put dia- monds and rubies, to the worth of fix thoufand florins, into different vefTels, and expofedthem to a violent fire for 24 hours ; at the end of that time the vciTels were taken out of the fire and opened, and there was not remaining the lead veftige of the diamonds, the whole had been difli- pated; but the rubies were found to have undergone no fort of change^ cither with refpe(5t to colour, ihape, or weight *. of
* See Magaiin de Hambourg, Tom. xviii.
p. 164. or an extraft in the notes annexed to
Henckel's Works, publiilied at Paris in 1760,
Vol. II. p. 413. — Similar experiments have
D 4 lately
( 56 )
OF EVAPORATION, VOLATILIZATION^ EXHALATION.
When folid or fluid bodies fufFer a diminution of their weight, the parts which become volatile and fly away, are faid to be evaforafedy vola- tilizedy exhaled^ for thefe three terms are often ufed promifcoufly, though it would be an eafy matter to diflin- guifli them. The parts themfelves are either humid, fuch are thofe which are feparated from all fluid s,^ (except quickfilver) and the watery parts of folid bodies; or they are dry; fuch are the volatile parts fepa- rated from marble or chalk, during the burning of lime, from volatile
falts,
lately been made in France : See Chymie par M. Bamne, Vol. I. p. 105. A good tranfla- tion of this excellent work is miich wanted »
( 57 )
falts, and refms of various kinds, by the heat of the atmofphere. The terms, evaporation, &:c. as limply indicating a lofs of weight, may be applied to both. Evaporation is not folely efFeded by the mediation of heat; ftrong dry winds in cold frof- ty weather, are often more powerful agents in promoting the evaporation of water and other fluids, than the greateft heat of the fun in fummer. The fuperficial parts of fluids are the only ones which are evaporated ei- ther by heat or air; and hence, in fimilar circumftances, the quantity evaporated, in any definite portion of time, will be greater as the fur- face of the fluid is greater. For this reafon, the pans in which brine is boiled for the making of fait, and the pits, in which fea water is eva- porated
( 58 ) _ porated by the fun and air for the fanne end^ are ufually made very fliallow, and of a large area j and a proper attention to this circumftance might be fcrviceable to fugar- ba- kers, confedlioners, and other artifls who are under the neceffity of eva- porating large quantities of water. However^ as a fluid contained in a deep veflel, when heated to a cer- tain degree, retains its heat longer than it would do, if it was fprcad over a Ihallower vefTel, and heated to the fame degree; it may become a doubt, whether the quantity eva- porated in confequence of its retain- ing heat longer, may not be equal to or exceed the quantity evaporated from the fhallower velTel, in confe- quence of its larger furface. It might, perhaps, be an ufeful pro- blem
(59 )
blcm to determine, by more accui-
rate experiments than any which have been hitherto made^ the length, breadth, and depth of a vefTel which, with the confumption of a definite quantity of fuel, would evaporate the grcateft: pofTible quantity of any fluid in a certain time.
OF DISTILLATION ANI> SUBLIMATION.
Though, in the procefs of evapo- ration, the volatile parts of bodies are ufually difperfed in the air, and the remaining ones only preferved, yet it often becomes necelTary to colled the volatile parts themfeives : when this is the cafe, proper veiTels are made ufe of for the purpofe, and the operation, if the parts are fluid, is called, difiillaUon, from their being collcded drop by drop, Jiillatim. If
the
( 6o )
the volatile parts when colledled, are dry and in a concrete form, the procefs is called, Juhlimation^ from the parts being driven upwards by the force of the fire, and colleded at a diilance from the remaining parts. The volatile parts thus colleded, may in general be called fublimatesj they are of different confiflencies, fome being in hard malTes, others in the form of a fine powder. Chemifts have agreed to apply the name of Juhlimatey to fuch as are in confident mafTes, the others, they call flowers : thus we hear of corrqfive Juhlimatey and Ci{ ftowers ofjulphur. The foot of a chimney is a matter fublimed from the fuel, and it comes under the denomination of flowers, orfub- limate, according as it is of a pow- dery or confiltent appearance. Du- ring
( 6i )
ring the fmelting of lead ore, that impalpable fubftance which iffues out of the chimney of the furnace, and falling upon the adjoining grounds, renders the grafs unwhole- fome for cattle, may properly be called the flowers of lead ore. This diftinftion between diflillation, as coUcdlingthe fluid, and fublimation, as colle6tingthefolid parts of bodies, is not always fcrupuloufly adhered to; fince the bell authors fpeak of the diftillation of fulphur, and of other bodies whofc volatile parts are dry.
The chemifts ufualiy diftinguifh diftillation into three kinds, accord- ing to the different manners in which the diftiiied vapour is colle(5led. The vapour in all cafes flics from the fire; hence when the fire is placed above the vcflcl which contains the matter
to
( 6a )
tobediftilled, the vapour in efcaping frbm the fire^ will defcend, and be- ing colledted in a proper velTel, the •diftillation is faid to be made>, ;per de^ Jcenfum^ by defcent. When the fire is placed under the vefTel containing matter to be diftilled, the vapour will afcend, and the diflillation is called, ^fr ajcenjum^ by afcent; this is the common manner of diftilling low wines and fpirits. Befides thefe two kinds of diftillation, there is a third, which ufually takes its deno- mination from the form of the vef- icl, in which the matter to be diftil- led, is put. This vcfTel is bent, and hollow, fomewhat refembling in ihape, a bullock's horn ; it is from thence, called by the French, a cor-- nue; more generally, from its curved ihape, a retort. The lower and more
capa-
( 63 )
capacious part of the retort is called
its belly J this is fometimes made al- moft globular, that it may contain the more -, the tapering crooked part is called its neck, and this part is joined to the belly, with various de- grees of obliquity, according to the life to which the retort is defigned. A large pear, with a long bent neck, may give an idea of the fhape of a retort. The matter to be diftiiled, be it liquid or folid, is put in at the neck : it defcends into the belly of the retort ; the heat is applied to the belly s the vapours in flying from the heat, ftrike againft the upper fide or roof, as it is called,, of the retort ; 'finding no exit there, they are forced out laterally through the neck ; the neck of the rdtort is clofely joined to •another hollow velTel, which from
its
( 64 )
its office, in colle6ling the diftilled vapour, is called the receiver or reci- pient-, the diftillation is faid to be made, per latusy by the fide, or per retortam, by the retort. The retorts are made of various materials, as of glafs, iron, earth, according to the degree of heat to which they are to be expofed.
It is not certainly known when, or by whom, the art of diftilling was firft found out. A diligent fcarcher into antiquity, informs us, "that about the year 1 150, the Moors of Spain firft introduced the art of di- ftillcry into the weft of Europe, they having learned it from the African Moors, who had it from the Egyp- tians i but how long before the faid African Moors had been in poffeiTion of this curious art, does not clearly
appear.
(6s )
appear. Certain it is that this art
■was not known to the ancient Greeks and Romans, fince neither Pliny, nor any other Latin or Greek author makes mention of it*."
To me it feems probable that the art of fublimation was known before that of diitillation. The term alem- bic or alamMc, is compounded of the Arabic particle ^/ (the), and the Greek word arnbixy a kind of cup, or cover of a pot 3 it is now ufed to de- note the whole of a certain diftilling apparatus; it formerly denoted only one part of it, namely the head, or that part in which the diftilled mat- ter was colle6ted. Diofcorides is thought by Suidas, to have been phyfician to the celebrated Queen
Cleo-
* Andeifon on Comm. Vol. I. p. 83, VOL. I. E
( 66 )
Cleopatra; he certainly knew the
manner of fubliming quickfilver from its ore, and he calls that part of the apparatus, in which the fub- limed quickfilver was colleded, ambix*i the addition of a fpout or beak to his ambix, would have fur- nifhed him with a complete inftru- ment for diftilling, as well as fublim- ing. But no one who confiders how near the ancients were to the difcb- very of printing without finding it out, can be furprifed at their know- ing fublimation, and at the fame time being ignorant of diilillation; for that Diofcorides was ignorant of the art of diftilling, may be reafonably conje6tured, when we confider the fad Ihift he was put to in order to colled an oil which arofe from boil- ing * L. V, c, no.
C 67 )
ing pitch i he orders a clean fleece of wool to be ftretched over the pot in which the pitch was boiled, and the oil to be prefled out of the wool as often as it became fuiEciently wet with it.
It mull be owned, that this argu- ment is not intirely conclufive againft the opinion of thofe who think that the art of diftillation v/as known to the more ancient Greeks and Ro- mans. For Diofcorides might have had his reafons for making ufe of the contrivance here mentioned, though he had been acquainted with diftil- lation. It feems moil natural to ex- pe6l fome account of this procefs in the writings of the phyficians Hip- pocrates and Galen^ had they been acquainted with it; but there are no paflages in their works, from which £ 1 any
( 68 )
any certain conclufion can be drawn relative to their knowledge of this operation. Geber, the Arab, was well acquainted with it, for he has given us a chapter on the fubjed, in which he lays down rules for diflil- iing per dejcenjum, and per ajcenjum^ but he fays nothing of diftillation per retort am. But diftillation was known, to the Egyptians at leaft, fome centuries before the age of Geber: for Zofimus of Panopolis in Egypt, who lived in the fourth century after Chrift, if not fooner, has exhibited fonie figures of a di- ftilling apparatus *. of
* Thefe figures may be feen in Borrichius* Hermetis et ^gyptionim fapientia, p. 156. The word Chemia firft occurs in the works of this Zolimus. He fays, though one may wonder whence he got his information, that it was in ufe before the Deluge, and that it
lignifies
( 69 )
OF DEPHLEGMATION, CONCENTRA- TION, RECTIFICATION.
The word phlegm ufually denotes; the moft watery parts of bodies, and when thefe parts are feparated, ei- ther wholly, or in a great degree, ei- ther by diftillation or fublimation,
the
fignifies Ibmething concealed. The Arabic tongue, according to Bochart, furnifhes u-s with the word Kemi fignifying concealment, and thence he derives C hernia, rather than from Cham the Hebrew root. Egypt is call- ed by Plutarch in OJiridey Chemia, which Ortelius expounds for Chamia, from Cham the fon of Noah. As the Arabians do not always copy exadly the proper names they borrow from the Hebrew ; may it not be conje6lured, that the Arabic Kemiy fignifying concealment, was introduced into that lan- guage, from the fecret and hieroglyphic manner, in which the priefts of Cham (Egypt,) concealed their knowledge of cliemiflry and other arts ?
E 3
( 70 )
the bodies, be they folid ar fluids are faid to be dephlegmated. When the watery parts of any compound fluid are by any means taken away, the remaining parts approach nearer to each other, and may on that account be faid to be concentrated-, though . the term concentration is chiefly ap- plied to the feparation of water from acidiiquors. It frequently happens that the produ6ts obtained by one operation, are not fufficiently pure and homogeneous, and that a fecond or third difl:illation or fublimation becomes neceflary to exhibit them in a proper form : this procefs of puri- fying the fame body, how often fo- cver it be repeated, is called reEiifi^ cation. Thus when we hear of an oil, or volatile fait, eight or ten times rectified, we are to underfland that
it
( 7r )
it has been fb often rediftilled or re- fublimed. If the impurity, to be taken away, 'be a fimple phlegm, it is obvious that the terms redlifi- cation, concentration, and dephleg- mation, may be fynonymous; and indeea mey are often ufed promif- coufly. Thus weak vinous fpirits, and weak vinegars are redified,, concentrated or dephlegmated by froft; for the water contained in thefe fluids being frozen and taken away in the form of inftpid ice, the remaining fluids become fbronger.
OF THE DEGREES OF HEAT COMMONLY USED IN" CHEMISTRY.
From what has been faid relative
to the fixity and volatility of bodies>
it may readily be conceived, that the
operations of diftillation, and fubli-
E 4 mation^
( 72 )
mation, by which the volatile parts- of bodies are colle6led, will require different degrees of heat, according to the nature of the body v/hofe parts are to be diftilled or fublimed. It would be endlefs to enter into all the fancies and contrivances of che- mifls upon this fubjedl^ yet there are four modes of applying heat, which, though they are not fo well defined that the degree of each can be accurately afcertained, ought to be particularly noticed, — the heat of boiling water-, — a Jand heat; — a naked fire heat ;^— and a Jolar heat.
Water, highly re6tified fpirits of wine, and other homogeneous fluids, cannot be heated in open velTels, and in agivenilate of the air,beyond a cer- tain degree peculiar to each. Asfoon as they fully boil, no continuance or
in-
( 73 ) increafe of fire can communicate to
them any increafe of heat ; hence a
vefTel, containing a body to be di-
ftilled, being expofedtothe a£tion of
boiling water, all the parts of the
body which are volatile, with the
degree of heat in which water boils,
will be elevated from the body*, and
may
* This obfervation is not probablj, perfeftly jufl. — It is a very remarkable phenomenon, that a vefiel containing water will never hoil^ how long foever it be ex- pofed to the action of hoiUng water. The reader may convince himfelf of this by an eafy experiment. Fill a common bot- tle with water, put the bottle thus filled into a pan of water, fo that the mouth of the bottle may be a little above the water in the pan ; fet the pan on the fire, and when the water in the pan boils in the moll violent manner, that in the bot- tle will be obferved not to boil, and if its heat be examined by a thermometer of
Fahrenheit*s
( 74 ) may be colle6ced in proper vefiels^ whilft the other parts, if the body confifts of different principles, will remain at the bottom of the veifel. This heat of boiling water is one of the moft definite degrees known in chemiflry -, there are many delicate operations, efpecially on vegetables, in which it would be improper to ufe fo great a heat as that of boiling water ; but it is not necelTary to enlarge up-
oa
Faherenheit's fcale, it will not be found to amount to above 202 degrees, whilft that of the boihng water in the pan is 21 z degrees. Hence it lliould feem, that bodies, diftiiled in vefTels expofed to the aftion of boiling water, do not experience the heat of boiling water. This pheno- menon is mentioned from Bartholin's Ada Medica, in the Fhilof. Tranf. for 1673, No. 97. — See alfo FrofelTor Eraun's Exper* Nov. Comm. Petrop. Tom, XII. p. 289.-— and Rozier's Journ. 1773.
( 75 ) on this obfervation in this place* Boiling mercury, boiling lead, boil- ing copper, would afford other defi- nite degrees of heat; and boiling oil might be very properly ufed as a mean of diftilling bodies, notwith- ftanding that oil thickens in boiling,, and thereby becomes hotter as the more fubtile parts are difperfed.
There are many bodies, and parts of bodies, which cannot be rendered volatile by the heat of boiling watery, thefe are ufually diftilled by immer- fing the veffel containing them in fand, and applying the fire fo as to heat the fand; for the fand gradually communicates its heat to the veffel which it touches : the fand is gene- rally put into an iron pot; it is evi- dent that the fire which is employ- ed to heat the pot, may communi- cate
( 76 ) cate any degree of heat to the fand, from the fmalleft^ to that which is fufficient to melt the iron, fo that it would no longer hold the Tand. — When the heat is communicated to the vefTel, containing the body to be diililled, through any medium, as that of boiling water, or hot fand, the body is faid to be diftilled in a water bath, or fand bath, the che- mifts having agreed to call the me- dium, ferving for the communica- tion of heat to the diftilling or fub- liming veiTel, a bathi and formerly, befides water and fand, they ufed vapour, iron filings, wood aihes, &c. for this purpofe.
When neither the heat of boiling water, nor of ignited fand, is fuf- ficient to feparate the volatile parts of a body from the remainder ; the
vef-
( 77 ) veflel containing the body is ex- pofed to a naked fire ; that is, it is furrounded with burning fuel, and by a contrivance in the ftrudlure of the furnace, the flame of the fuel is often made to reverberate upon it. This degree of heat is alfo indefinite; it may be augmented, by bellows and other means, to fuch a pitch as to melt the furnace containing the fuel, or the velTel containing the body to be diflilled. The degree of heat which may be excited in furnaces is undoubtedly very great, yet it is far inferior to that of the fun's rays when colleded into a focus by a burning glafs or fpeculum : the force of this folar heat cannot, perhaps, be fubje6b to any other limit, except what arifes from the difliculty of forming large fpeculums.
OF
( 78 )
OP SOLUTION, SATURATION, AND CRYSTALLIZATION.
When the parts of a folid body, :as common fait or fugar, are fo united to a fluid, as water, that they compofe with it an apparently ho- mogeneous fluid, remain fufpended in it, and do not deflroy its tranfpa- tcncy, the folid body is faid to be diffohed in the fluid ; the operation is csAlcd/olution j the fluid, being look- ed upon as the principal agent in difTolving the body, (though all ac- tion is mutual and equal) is called the /olvenf, or more commonly, ac- cording to fome filly or indelicate ideas of the alchemiils, the menftru^ urn-, the compound refulting from the union of the fluid and the body, is called a Jolution of this or that
body.
C 79 )
body, in this or that menfiruum. Thus we fpeak of a folution of common fait or fugar in water, of a folution of fulphur in oil of tur- pentine, of camphor in fpirits of wine, of filver in aqua fortis, and fo on. The term folution is alfo fometimes applied to the union of two fluids j thus the air is faid to be difiblved in water, becaufe all na- tural water contains air 5 and water is faid to be diffolved in air, becaufe the moft tranfparent air contains a confiderable portion of water : thus alfo various forts of oils are faid to be diffolved in fpirits of wine. And laftly, folution is applied to the union of two folid bodies : thus glafs is a compounded body refult- ing from the mutual folution of an earth and a fait.
It
( 80 )
It may be worthwhile to explain, a little more fully, the firft and moft obvious notion of folution; that in which a folid body is united to a fluid. If you take an ounce of common fait, and throw it into a quart of water, it will fall to the bottom of the water, as an ounce of fand or chalk would do ', but it will not, like them, flay there ; in a very little time, efpeci- ally if the water be ftirred, the fait will intirely difappear, it will be uni- formly difperfed through the whole body of the water, no one drop of water will contain more particles of fait than another, nor will any of them contain fo much fait as it is able to do. For if you add another ounce of fait, that will alfo be dif- folved, but not quite fo fpeedily as the firfli and that v/iil alfo be uni- formly
( 8i ) fo rmly diffufed through the whole body of the water, fo that each drop of water will now contain twice as much fait as it did before. This pow- er which tlie water has of taking up and keeping fufpended the particles of fait is not unlimited ; you may add fo much fait to it, that it will not diflblve one particle more, the wa- ter in that ftate is properly enough faid to htjaturated. AH other men- ftruums are likewife faid to be fatu- rated, when they will not take up and keep fufpended any more of the bo- dy diflblved in them: thus a pint of fpirits of wine will only take up a definite portion of camphor; a pint of oil of turpentine will only keep dijTolved a definite portion of ful- phur; and a pint of aqua fortis will be fo faturated with a definite portion VOL. I. F of
'( 82 )
of filver, that it will have no fort of adion upon any additional quan- tity which fhall be put into it.
We do not know either the fize or the ihape of the particles of wa- ter, nor whether they are contiguous to each other, nor how they come to attra6b the particles of fait more flrongly than they attraft each other; but it is notwithftanding, to this prevalent attra5fion^ that we at- tribute the folution of the fait in wa- ter, and of every other body in its proper menftruum. We are certain that every particle of water attradts to itfelf, and keeps fufpended a par- ticle q( fait, of a definite weight; otherwife an equal number of thefc particles, conftituting drops or par- ticles of equal bulks, would not have equal weights, nor contain equal
quan-
(83 )
quantities of fait, which we are cer- tain they do. Now if we fuppofe a fingle particle of water to be evapo- rated, or any how taken away from a faturated folution of fait, then the particle of fait which was kept fui"- pended by the attra6tion of that par- ticle of water, muftofneceflity have a tendency to fall down to the bot- tom; becaufe every other particle of water, being fuppofed to have as much fait united to it as it is able to fuftain, can contribute nothing to its fupport; and if inflead of one parti- cle of water we fuppofe a thoufand, or ten hundred thoufand to be eva- porated, then will a thoufand, or ten hundred thoufand particles of fak be left without any fubflance to fup- port them -, and having no furround- ing fluid to hinder their mutual at- F 2 - traftions
{ H )
tra6lions from taking place, they will coalefcc together upon the fur- face of the folution from which the water has been evaporated, and by their union conftitute a faline pelli- cle, which will be vifible to the na- ked eye. This pellicle, as foon as it becomes heavy enough to over- come the tenacity of the fluid upon which it floats, will by its gravity defcend from the furface where it was formed, to the bottom of the vefTel containing the folution j or, meeting with afperities on the fides, it may attach itfelf in part to them. But the taking away a part of the diffolving fluid is not the only mean by v/hich the particles of the dif- folved body may be made to unite; there is another, and in many in- ilances, full as efficacious a one, the
taking
( 85 )
taking away a part, not of the fub-
fiance, but of the heat of the diiTolv- ing fluid. Thus if you put into a quart of boiling water as much falt- petre as it will difiblve, and filling a bottle with the boiling folution, in- ftantly cork it up; then you are fure that no part of the water can efcape^ and if the diminution of the quan- tity of a menflruum was the only way by which the parts of the dif- folved body could be made to unite, then would the particles of the dif- folved faltpetre, in this inflance, not unite at all, fince there can be no di- minution of the quantity of the dif- folving water: you will, hov/ever, on the contrary, obferve the parti- cles of the fait coalefcing together, as the Iblution grows cold, and forming large and regular cryfcals. F j ' . — The
( 86 )
— The word cryftal is derived from the Greek words cryos^ froft, and ftelluo^ to contra6l. The ancients fup- pofed a particular mineral, known by the name of rock cryftaU to be nothing but congealed watery this mineral is of a determined angular figure, and hence all falts and other fubllances which from being dif- folved in menftrums, or fufed in fire, concrete into regular figures, are faid to be cryftallized.
There are a great many circum- ilances relative to the manner in v/hich different falts cryfballize, which cannot be infilled on in this place i one thing deferves particu- larly to be remarked, — that every fait in cryftallizing, invariably af- fumes its own peculiar form. You may diflblve common fait, or falt-
petre.
( 87 ) petre, a thoufand times, and cryflal- lize them as often by evaporating or cooling the water in which they are diflblved, yet will you ftill find the common fait will be conftantly cry- ftallized in the form of a cube, and the faltpetre in the form of a prifm ; and if you examine with a micro- fcope fuch faline particles as are not vifible to the naked eye you will ob- ferve thefe particles to be of the fame fhape with the larger mafTes. The definite figure appropriate to every particular fpecies of fait, may admit a little variety from the acci- dental admixture of other bodies, or fromfome fingular circumftances at- tending the evaporation and cryftal- lization of the folution; but thefe varieties are foreign to the nature of thefalc, and are not greater than what F 4 attend
( 88 )
attend almoft every fpecies of vege- tables, and even of animals, from change of food and climate.
Here a large field of inquiry opens to our viewi and though it be bet- ter, as Seneca has it, de re ipfa qua- ver e quam mirari', yet all our attempts to invefligate the works of God, are Vv'eak and ineffe6tual : we feel his in- terference every where, but we can- riot apprehend the nature of his agency anywhere. A blade of grafs cannot fpring up, a drop of rain can- not fall, a ray of light cannot be emitted from the fun, nor a particle of fait be united, with a never-fail- ing fymmetry, to its fellow, without him : every fecondary caufe we dif- cover, is but a new proof of the ne- cefTity we are under of ultimately recurring to him, as the one primary
caufe
( 89 )
caufe of every thing. Yet notwith- ftanding this our utter inability to fearch far into the nature of things, philofophical inquiries are by no means without their ufe. He who finds his endeavours to comprehend the works of creation checked at every turn; who underflands that every the minuteft part of this little earth, which is itfelf nothing, as it were, when compared with the infi- nity of the divine works, is to him one great miracle; will not be over- zealous in affirming that God can- not interfere by his pr.ovidencey in the management of what he hath made, or that he has interfered in this or that particular way. In the ccnfci- ous abafement of his own intelledl, which phiiofophy will have taught him, he will be cured of all attach- ment
( 90 )
ment to fyftem, whether it be a fyf- tern of bigotry or infidelity: he will not be fond of anathematizing every one who cannot think with him in religious matters; nor, on the other hand, will he contend that a revela- tion from God muft be an impoffi- bility, from any abftradt notions he may have framed of the nature and works of the Supreme Being. But to return to our fubjed.
If what has been faid relative to cryftallization, be not perfedly in- telligible to the reader, I would ad- vife him to make the following eafy experiment, which will give him a better notion of the matter than a thoufand words. Into a bafon full of boiling water, put as much falt- petre as the water will take up; if the faltpetre was purified, the tran-
fparency
( 91 )
fparency of the water will not be in-
jured, it will ftill appear to be an homogeneous fluid : when the water will take up no more faltpetre, then he may conclude that it is faturated: let it Hand without being llirred, till it grows cold. As it cools^ a great many cryftals, all of the fame fhape, may be feen fhooting out from the fides and bottom of the bafon, and increafing in fize till the folution be» comes quite cold. When no more cryftals can be formed by that de- gree of cold which prevails in the apartment where the experiment is made, pour the liquor from the folid cryftals ; this liquor is ftill faturated with faltpetre j and in order to make it part with more of its faltpetre, fome of the water which keeps it dif- folved muft be evaporated : upon the
taking
( 92 )
taking away a part of the water, a correfpondent part of the fakpetre lofes the power by which it is fuf- pended, and ought, upon that pre- fumption, inftantlytofall to the bot- tom: yet it mAift be remembered, that the water from its increafed heat during the evaporation, is able to fupport more fakpetre than if it was cold s and therefore the fakpetre will not begin to cryftallize, notwith- llanding the lofs of part of its men- flruum, till the remainder begins to cool. By repetition of this pro- cefs of evaporation and cryftalliza- tion, vve may obtain all the fakpetre which was at firfl: diffolved, as no portion of it can be evaporated with that degree of heat which is ufed in evaporating the water.
OF
( 93 )
'OF MIXTURE AND FILTRATION.
There is a difference betweenyb//^- tion and mixture fufficiently obvious, though not always attended to. — Thus water v/hich fprings from chalk, has often, when the fprings are low, a milky caft arifing, from fome very fine particles of chalk which are mixed with it, but not dif- Jolvedin it; for perfect folution is al- ways acompanied with tranfparen- •cy. Briflol and Matlock waters are very tranfparent, though they con- tain a large portion of €arth ; but the earth is in the ftate of a fait, and perfe6lly diffolved in them. — Turbid waters, turbid folutions of falts, and other liquors which con- tain, mixed with their fubilance;, any iieterogeneous matter, are purified
to
( 94 )
to a certain degree by filtration y that is, by being made to pafs through certain fubftances, whofe pores are large enough to give a pafTage to the particles of water, and to the parti- cles of any fait difTolvedin water, but not to the earthy or oily foeculences which may happen to be mixed with it. The fubftances made ufe of are CdXltdi filters -y they are either fand, or a porous kind of ftone, thence called a filtering ftone, or flannel, or linen, or leather, or brown paper into the compofition of which no fize has entered. This laft fubftance is gene- rally ufed in fmall chemical experi- ments 5 it is made up into a conical form, and placed in a funnel, or other convenient inftrument to fupport it. Filters are ferviceable inftruments, not only for the purifying of liquors,
but
( 95 )
but for the feparating of any kind of fait from a mixture of fait and earth, and enabling us to afcertain the pro- portion of fait and earth contained in any propofed fpecimen. An inftance will illuftrate my meaning. It 'is commonly known, that wood alhes, fern alhes, and the alhes of moft ve- getables, confifl partly of a particular kind of fait, partly of earth. Sup- pofe i;. was required to determine the proportion of fait and earth con- tained in any fpecimen of alhes, the procefs muft be condu6bed in the following manner: — Take a pound of the alhes, previoufly well dried, boil them in a quart of water, pour the water apd the aihcs into a filter, the water will pafs through the filter, bringing with it the fait con- tained in the alhes 3 for water dif-
folves
C 96 ) folves all kinds of fait, and no kind
of earth : the earth therefore of the alhes will be left in the filter : waih the earth remaining in the filter, by- pouring upon it hot water, till the water in filtering through it, comes off wholly without taftes then eva- porate all the water in which the alhes were boiled, and with which the earth in the filter was wafhed, and when all the water is diflipated, there will be left a greyifh kind of fait, of a very pungent tafle. When this fait has been dried as much as the afhes were, it muft be weighed whilft warm from the fire, and its weight noted; then dry in the fame manner the earth remaininer in the filter; and the weight of the earth thus dried, added to the weight of jthe fait, which has been extraded,
will
( 97 )
ivill, when the experiment has been properly made, amount to the weight of the alhes employed in
making it^
OF THE ANALYSIS OF BODIES,
Mofl of the bodies which we meet with upon the furface of tht earth or below it, are compounded of hetero- geneous principles ; thefe principles muft, in many inflances, be feparated from each other, before either the nature of the body can be properly underftood, or the principles them- fclves be applied to any ufeful pur- pofe. Thus the juice muft be preff- ed from the earthy part of the grape, the fugar-cane, and the olive, before we can obtain either wine, fugar, or olive oil. The faline matter muft he extraded from the earthy part of
VOL. I. G the
( 98 )
the alhes mentioned in the iaft trx-
periment, before it can in many cafes become ufeful as a fait. Sulphur or arfenick, or both, muft in many in- ftances be feparated from the ores of metallic fubftances with fmgular care, before the metallic fubftances themfelves can become articles of commerce j or even before their ex- iftence, as conftituent parts of the ores, can be made apparent. Many bodies, without any afliftance from art, fpontaneoufly refolve themfelves into diftin6t principles; thus blood, by ftanding, becomes feparated into a watery fluid, and a red flelhy fub- flance; milk refolvcs itfelf in like manner into cream, into curd, and into whey. The procefs by which the heterogeneous parts of a com- pound body are feparated from each
other.
( 99 )
Other, whether it be carried on by nature or art, may be called the analyftSy refolution, or decomfofition of the body.
It frequently happens, that the parts feparated by one analyfis, are thcmfelves connpounded bodies, and capable of being refolved, by a fur- ther procefs, into more fimple prin- ciples. Juft as in language, a fen- tence may be refolved into words, words into fyllables, and fyllables into letters; fo in the decompofition of natural bodies, we at laft arrive at principles which do not admit any -further refolution or change. Thefe fimple, unchangeable principles are called elements-, and it may, from what has been advanced, be readily apprehended, that the fame fub- ftance may be cfteemed anelement by G 2 one
( lOO )
one man, which is not fo efteemcd by another, according to the diffe- rence of their Ikill exerted in the ana- lyfis of bodies.
OF CHEMICAL ELEMENTS.
By chemical elements, which are the laftproduds of chemical analy- sis, we are to underfland, not very minute indivifible particles of mat- ter, but the fimple homogeneal parts of bodies which ar€ .not capable, as far as our experience teaches us, of any farther refolution or divifion, ex- cept in a mechanical fenfe, into fimi- lar parts lefs and lefs without end, as water into vapour more or lefs fub- tile and attenuated. Ariftotle and his followers tiictmtd earthy air, fire^ and-K^^/^r^tobeelements, fimple aad miiform.in their feveral kinds, effen-
tiallj
( loi )
trally diftindb, and utterly incapable of being converted into one another, yet eafily uniting together, and by their different arrangements, pro- portions, and mixtures, compofing every body in the univerfe. Many modern chemifts have adopted this idea J others have increafed the num- ber of elements^ by adding a faline principle i others have contended,, that fome of thefe elements, air and. fire for inftance, are themfelves com- pound bodies; and others, laftly, ar>e perfuaded, that there is only one elementary homogeneal matter, and that all the varieties of bodies, as well as of what are commonly efleem- ed elements, ought to be attributed to the different magnitudes and figures of the particles compofing them> and as the component parts G 3 of
( icr2 ) of water and air, or any other body> are by no means fuppofed to be ele- mentary particles of matter, but ta be made up of different numbers of elementary particles arranged in dif- ferent forms, it may be thought pro- bable, that mechanical caufes ma^ either diminifh or augment the num- ber, or change the difpofition of the particles, and thus eifed the feveral. varieties obfervable in nature.
It would be improper in this place to enlarge on a fubjedt, concerning: which both ancient and modern phi- lofophers have been fo much divided in opinion r Their great diverfity of fentiment may fuggeft a fufpicion^ that the full cdmprehenfion of it does not fall within the reach of the hu- man underflanding. The following obfervation may, perhaps, tend a lit- tle
( loj )
tie to illuftrate this matter. Let us fuppofe that this terraqueous globe was not furrounded with any- air or atmofphere, and that, by an approach, to the fun, or an increafe of the fubterraneoiis fires, by fome means or other it fhould become expofed to a heat four times greater than the medium heat of ourr fummer, which we may reckon to be about 60 degrees of Fahrenheit's thermometers then would an atmo- fphere be quickly formed around it : all the water upon its furface, molt of the juices of plants and animals,, and a great variety of mineral par- ticles^ would be raifed up in vapours and exhalations,^ and whilfi the heat continued would be kept fufpended in an elaftic ftate, and conilitute an atmofphere analogous, as it may rea-- G 4 fonably
( 104 ) fonably be imagined, to the chaotic ftateof ourprefent atmofphere, only differing from it in thisj that it would require a greater degree of heat, in order to keep the particles of matter from coalefcing into one heterogeneous mafs. Again, in the prefent ftate of the atmofphere, fup- pofe that a great degree of cold fhould continue unabated for any length of time; all the water upon the furface of the earth would be changed into a folid tranfparent flone, which might be dug out of its quarry, and employed in build- ing, as well as marble, or any other fpecies of ftone; all the particles of air would be brought clofer toge- ther s fome of them, which were the leaflelaflic, would be re-united; and imagining the cold to be indefinite-
1/
( I05 ) ly increafed, what reafon can there
be againft fuppofing that the whole atmofpherc would be reduced into a folid ftate,. forming an heterogene- ous cruft upon the furface of the- earth : the thicknefs of this cruft, fuppofing it to be as denfe as mar- bky would be about four yards ? It will eafily be underftood,. that wa- ter, and air, and earth, are, upon this hypothefis, but variations of the fame element introduced by heat.
That the atmofphere which fur- rounds the earth, was originally formed from the chaotic mafs, by having the more fubtile parts of which that mafs confifted,, elevated and put into an elaftic ftate by means of heat,, feems not altogether imprabable. We find the atmo- fphere or firmament immediately
fuc-
( io6 )
fucceeding the formation of light j, now, if the effedl of that light was heat, be the form or matter of it what you pleafe, then would fuch 'particles of the fhapelefs jumble,, as were capable of being evaporated with that degree of heat, be elevated in an elaftic ilate, and a divifion or Reparation would be made in the midfl of the great abyfs, between- the waters which were of a nature fubtile enough to be converted by that degree of heat into an elaftic fluid, conftituting the firmament or atmofphere,, and the waters which could not be evaporated in that de~ gree of heat, but ftill remained co- vering the furface of the globe, be- ing not colle6bed into one place,, that the dry land might appear, till the third day. This notion of the
atmo-
( 107 )
atmofphere and its formation, feems to be conformable enough to New- ton's opinion^ exprefled in his letter to Mr. Boyle. " I conceive the con- fufed mafs of vapours, air, and ex- halations, which we call the atmo- fphere, to be nothing elfe but the particles of all forts of bodies of which the earth conlifts, feparated from one another, and kept at a di- flance by the faid principle*," — ^ principle of repulfion.
* Boyle's Life prefixed to the foL edit, of his Works, p. 71.
ESSAY
ESSAY in.
OF SALINE SUBSTANCES.
IT may b€ expedled that this dif- quifition fhould be commenced by giving a rigid definition of the term fait, or faline fubftance. But the complex ideas of ;natural fub- ftances are not fiibje(5l to very de- finite defcriptions. Nature, in her feveral productions, proceeds by imperceptible gradations, feldom leaving any ;decifive marks, by which we can invariably difcrimi- nate them into forts. The two moft general ideas which appertain to the -^vord fait, 2,xq ^apdity ?^vi6. Joluhility
m
/
C "O )
in water, and fome add, want of in- flammability in fire. Every fub- llance foluble in water, and afFed- ing the organ of tafte with a fenfa- tion different from that excited by its weight, may be called a fait : I am fenfible that this defcription of a fait cannot in all cafes be clofely adhered to, without confounding things fufHciently diftind. Copper by long maftication excites a nau- feous tafte, and by lying long in water it is in part diffolved in it, and yet we arc not accuftomed to clafs copper among faline fub- itances.
If any one fhoiild wiih to extend the meaning of the term fait, by ap- plying it to all bodies which have regular figures, from fome obfcurc notion, that a faline principle is the
uni-
( III )
^iniverfal caufe of cryflallization, then a variety of fpars and precious flonesj glaflesj and metallic lub- ftances, which are neither fapid nor folublc in water, would be rightly denominated falts; and water itfelf, when concreted into ice, would come under the fame appellation. But leaving this more enlarged fignifi- cation of the word fait, to the con- templation of thofe who are ftudious in the formation of fublime fyitems of nature; and confining ourfclves to the more obvious properties of fapidity and folubility in water as charadcriftic of faline fubftances; we may proceed to obfervc, that all falts may be reduced to one or other of the three follovvring kinds ; they are either, — acid falts — alkaline Jalts MUtral Jalts.
OF
( ri2 )
OF ACIDS.
The term acid explains itfelf by its ordinary acceptation; for though there may be a great divcrfity in the taftes excited by different acid bo- dies, both with refped: to intenfenels and quality, yet no language has furnifhed diftindb names for this va- riety. Sorrel, vinegar, cream of tartar, lemons, tamarinds, and a great many other bodies, are all faid to be acid when tafted j and this capacity of exciting an acid tafte, is one charadcriftic of an acid fait.
All thofc bodies, with a very few exceptions, which have an acid tafte, have alfo, when fufficiently puri- ■fied, the property of changing the -blue colours of vegetables, as of iyrop of violets into a red ; and
hence
( "3 )
Jience this quality is reckoned ano- ther charadcriftic of an acid fait.
The great divifion of all terref- trial fubftances into minerals, vege- tables, and animals, called the three kingdoms of nature, has fuggefted to chemifts a divifion of acids into mineral^ vegetable^ and animal acidsy according to the nature of the fub- je6l from which they are produced. The mineral acids may be copiouf- ly feparated, by diilillation, from 'vitriol^ nitre i and Jea Jalt ^ and in reference to thefe fubftances, they are ufually called the vitriolic acidy xht nitrous acidy and the marine acid* — The vegetable acids are either nativey fuch as , exift in four fruits and plants 3 or fa^itiousy fuch as vinegar and tartar, which are pro- duced by fermentation. To the
VOL. I. H clafs
{ ^14 )
clafs alfo of faditious vegetable acids, may be referred all the acids feparable from vegetable matter by diftillation; thefe generally retain- ing a burnt fmell, are called em- ^yreumatic acids : they have not hi- therto been fo fully examined as to be ciafTed into different fpecies. Animal acids are fuch as may be feparated from various parts of ani- mals by diftillation; or they are fuch as bees, ants, and fome other infers, contain in proper veiTels ready pre- pared, and which they eje6l in fting-
OF ALKALIES,
The term alkali is compounded of the Arabic particle ^/(the) and kali the Arabic name of a maritime plant called by usglaffworty or marjhjam-- phire^ GlafTwort is diftinguiflied
by
by botanifts into the gfeater or lelTer jointed glaiTwort^ fnail-feeded glalTwort, prickly giafiwort, &c. all of which afe called kali ; and from the afhes of them all, when thb- i-oughly calcined, there may be wafhed out a fait, which is called an alkali^ or an alkaline JaVt , If any one Ihould think that the word kali is derived from an Hebrew root of nearly the fame found, fignifying to burn; then he will conclude, that alkali originally had reference not to the name of any particular fpe- cies of plants, but to the manner in which a fait might be procured from the afhes of burnt vegetables in general; and that in procefs of time a certain kind of plants came to be called kali, from its alhes abounding more, than thofe of any H 2 €>ther
( 1x6 )
Other plant, with fiilt ; juft 2i%/ods or Joude, from being the comnnon name for this very fait, which is fe- parated from kali, has become the French name for the plant itfelf *.
Kali is not the only maritime plant which yields an alkaline fait. On the coaft of Spain, about Ali- cant and Carthagena, and, indeed, in many other countries bordering on the Mediterranean, the farmers fow their lands with the feeds of dif- ferent forts of maritime plants, which they pluck up at the proper feafon, dry in the fun as we dry hay, and burn to afhes. About Cartha- gena
* Kali herbam in cineram verfam Sodafn appellat vulgus. Baptis. Porta Mag. Nat. L. vi. C. I. He defcribes the method of EXtrafting the fait out of the aflies, and iays that out of five pounds of the afhes they got cue of fait.
( "7 )
gena they principally cultivate four forts of plants, barilla, gazul or alga- zulyjozay 3,nd/aHcorma, Th^ barilla yields the pureft fixed alkali; each root of this plant fends out a grease many ftalks refembling famphire> and rifing to about the height of four inches. The ground is much, exhaufted by the crop, it lies fallow every other year, and each acre pro- duces about a ton of barilla*. Whe- ther any of our fait marfnes could be advantageouily employed in this kind af culture, may deferve the fe- rious confideration of thofe to v/honi they belong; certain it is, that plants which would yield this alkali, grow fpontaneouily uponfeveral of them. On the Orkney and Scilly ifies, and on moft parts of the Britifn. H 3 coad;,.
Swiobmne's Trav. through Spain, p. 130.,
( "8 )
coaft, great quantities of bladder fucusj or fea oak*, under the nam© of fea wrack, are annually bairnedir> order to obtain an alkaline fait. The plants are cut from the rocks on which they grow, or gathered from the beach on which they are thrown by the tide 3 and being fufficiently dried by the heat of the fun in the fummer feafon, they are fet on fire ; the fire-place is a hole in the ground; the afhes, to which the plants are re- duced, are melted by the violence of the fire 5 the melted mafs is kept in a ftate of fufion for three or four hours^ it is then fufFeredtocool, and when it is fet, they take it out of the hole in which the plants were buj-n- ed, and the operation is recom- menced. The folid mafs procured
from * Fucus vcficulofu?^ linnatir
( "9 )
from the melting of the afhes of fea
wrack, Is an article of great ufe in the making of glafs and foap, and is known in commerce under the name of kelfy or kelp ajhes. From kelp allies may be extraded a fait, the fame in every refpe6t with that v/hich may be procured from the alhes of kali or glalTwort. The following experiment was made in order to af- certain the quantity of faline mat- ter contained in British kelp.
Thirty ounces of kelp from the Orknies, which had been previoufly pounded into a Ene powder, and in that ftate well dried upon a hot iron, were boiled in various portions of water, till all the feline matter was extracted from the afhes ; the water containing all the faiine matter of the kelp was then evaporated with a H 4 gentle
( I20 )
gentle heat, and the fait which re- mained after the water was all eva- porated, was further dried, as the kelp had been,, upon a hoi iron. The faline matter in that dry ftate weigh- ed 19 ounces. The earth remaining, after the extradlion of the faline matter being carefully collected and thoroughly dried upon a hot. iron, it weighed exactly in that flata 1 1 ounces. This experiment was. repeated with the fame fuccefs.
There is a much greater quantity of faline matter contained in Spanilh, barilla than in Englifh kelp, as may be inferred from the following expe- riment. Spanifli barilla, as well as Englifh kelp, is mixed with feveral pieces of black matter; this matter confiUs of pieces of the plants which have been reduced to charcoal, but
not
( »2t )
not to afhes, during the combuflion of the plants. I pounded into a fine powder a quantity of barilla j the powder had a greyifh caft from the charcoal it contained; it was dried upon a hot iron, and it loft by that operation one fourteenth of its weight. I took 30 ounces of this dried barilla, and proceeding as in the analyfis of kelp afhes, I obtain- ed 22 ounces of faline matter. It appears from hence, that there is three hundred weight more of faline matter in a ton and an half of barilla, than of kelp aihes.
It is very probable, that kelp aihes prepared in different countries, con- tain the earthy and faline parts in proportions different fromthofe here afcertained y yet it is worthy remark- ing^ that the analyfiahere given coin- cides.
( in )
cides, as to the earthy part, with the experiments of one author> and as to the faline part^ with the experiments of another. From 28 drachms of kelp aihes, Dr. Home obtained 10 drachms of earth; now the propor-*- tion of 30*0 u, is nearly the fame with that of :^8 to 10*. — M. Cadet obuined 6 pounds 3 ounces and an half of faline matter from 10 pounds of kelp afhes -, if he had obtained one half ounce more, the proportion of faline m.atter pro- cured from the kelp he examined,^ would have been almoft exadly the fame with that procured from the Orkney kelp which I exa- ipainedl. I wa& not aware of '—'-"' the
■* See his very ingenious ElTay on Bleach- ing, p. 151.
f Hifi. de TAcad. des Science* a Par. Ann. 1767, p. 4B8.
( 1^3 )
the experiments here referred to^ when I undertook to afcertain tlie refpedtive quantities of earth and faline matter contained in kelp afhes, (ind for that reafoa the coincidence may be the better relied on.
The reader may wonder, why, in fpeaking of the fait contained in kelp, I have called it by the general name, faline matter, in the very place where I was confidering it as a parti- cular kind of fait, as an alkali : this ^:as not done without reafon; for not only kelp alhes, but the afhesof kali, barilla^ and moft maritime plants, befidesan alkalinefalt, contain apor- tion of common fait, and of fome other kinds of fait, which it is not . fieceilary here to enumerate. Thefe foreign falta injure very much the purity of the alkali, for the obtain- ing
( 124 )
ing of which the plants arc burned; and the Britifh kelp afhes abound with them fo much, that from fome trials I have made Ilhould conclude> that the 19 ounces of faline matter, which I had extracted from 30 ounces of kelp, did not contain above five ounces of pure mineral alkali free from water. The expreffion, free from water, requires an explanation. The 19 ounces then of faline mat- ter obtained from 30 ounces of kelp^ were diflblved in water, and from the folution, when evaporated and cry- ftaliized, I obtained 12 ounces of al- kaline fait in very fine tranfparent cryftals. Since all attraction is mu- tual, it may readily be underflood,, that as the particles of water attrad^ thofe of the alkaline fait, and retain, them in folution, fo the particles of
the
( m )
the alkaline fait will attract thofe of the water, and retain them in cry- ftallization. The water thus attrad- ed by the particles of a fait during its cryftallization, is ufually denomi- iiated the water of cryftallization.
This water of cryftallization is •contained in different quantities in different falts, and it adheres to them with different degrees of force ; though it is eafily feparated from mofl of them, the moderate heat of the atmofphere being fufHcient to evaporate it from many. When this water of cryftallization is evaporated from any fait, the figure of the cry- ftals is deftroyedi the fait from being afolid tranfparentfubftance becomes an opake powder. But though a fait, in lofing its water of cryftalliza- tion^, lofesits cryftaliineform^ it does
not
( .16 )
not thereby iofe v'ln of its faiine quality; for the water which is fepa- rated from it is pure water; and th^ fait, by beitig rediflblved in water and recryftallized, will not only re- gain its former figure^ but the wholt of its weight.
This obfervation refpeding tht water of cryftallization is not with- out its ufe, either in medicine or trade. The fait known in medicine under the name of Glauber's fait, is one of thofe which contains near half its weight of water, wholly un- clTential to it as a fait: hence an ounce of Glauber's fait, in tranfpa- rent cryftals, has not more ftrength as a medicine, than half an ounce of the fame fait when reduced to a powder, by having its water of cry- ftallization evaporated. The twelv-e
ounces
( 1^7 ) ounces of alkaline fait in queftiort were expofed to a very gentle heat (they would have been melted by a •ftrong one) till they were reduced to a fine powder: this powder wai dried on a hot iron, and in that ftate it weighted not quite five ounces; fo that twelve tons of alkaline fait iri cryilals, is not Worth more than five tons of the fame falt^ when freed from its water of cryftallization. Kelp afhes appear, from thefe experi- ments, not to contain above five tons of the alkaline fait here fpoken of iti thirty tons of the alhes.
1 took the 22 ounces of faline rnat- ter which I had procured from 30 ounces of dried barilla, and difTolving them in water obtained 36 otinces of fine cryftals- of alkali, and about 3 ounces of a fait which v/oxild not cry-^
ftailize,
( i;-8 )
ftailire, and which was in part Tea fait. It appears from this experi- ment, compared with the preceding, that the fait procurable from barilla, contains a far greater proportion of pure alkali, than that from kelp does; and hence barilla is preferable to kelp, not only from its containing mere faline matter in a definite weight, but from that faline matter being of purer quality. The cry- llalline fait thus obtained, being ex- pofed to the fire, was quickly melted, and when all the water which had en- tered into the compolitionof the cry- ftals had been evaporated, the fait weighed 2i| ounces, half an ounce having been loft by the operation. • The alkaline fait contained in the afhes of maritime plants, when ex- pofed to the heat x)f a glafs-houfe
furnace.
( 129 )
furnace, lofes confidcrably of its weight, but in moderate fires it lofcs nothing; hence this fait is called a fixed alkalu A pound of common fait contains about half a pound of this fixed alkali. Common fait is reckoned a mineral, there being large mines of it in moft parts of the world. This fixed alkali, which con- flitutes near half the weight of com- mon fait, and from the dccompofi- tion of which it is moft probably produced, is therefore often called the miner aly foffilcy or marine fixed al^ kali. It is entitled alfo to the name of the mineral fixed alkali, from its Jbeing met with in fome mineral wa- ters, and from its being found either ready formed upon the furfaceof the earth, or dug out of certain lakes, which are'^dried up in the fummer, in VOL, I. I Egypt,
C 130 )
Egyptj and other parts of the Eaft* It is there called natron, and is fup- pofed to be the nitre fpoken of by Solomon, when he compares the efFed which iinfeafonable mirth has upon a man in afflidion, to the aftion of vinegar upon nitre; * " as vine- gar upon nitre, fo is he that fingeth fongs to a heavy heart:" for vinegar has no effed upon what we call nitre; but upon the alkali in queftion it has a great effedl, making it rife up in bubbles with much efFervefcence. This alkali has been met with alfo on the Pic of TenerifFe and in Barbary, fo that it is upon many accounts pro- perly enough denominated the mine* ral fixed alkali.
The alhes of m.oft other vegeta- bles, as well as thofe of maritime plants, yield a fait which has many
pro- * Prov. XXV. 20.
( I3» )
Properties in common with the mi- neral fixed alkali -, but not having all the properties of that fait, it has for the fake of perfpicuity been called the vegetable fixed alkali. Both the 'mineral and the vegetable fixed al- kali are prepared by boiling the iafhes, to extradt the fait from the r earth i the water containing the fait In folution, is then evaporated fo as to leave the fait dry. From this manner of preparing them, thefe falts have been often called lixivial falts, iix and lixivium both fignifying a ley made with alhes. The operation of evaporating the water is performed in large iron or copper pots; and from this circumftance thefe alkaline falts, efpecially the vegetable fixed alkali, have come under the name x^ipt-ajh,
I 2 Greaf
( 13^ )
Great piles of wood are, in many
countries, burnt for the exprefs pur- pofe of obtaining pot-afh. From the following experiments, fome notion may be formed of the large quanti- ties of wood which muft be burned, in order to obtain even a fmall por- tion of pot-alh,
I defired a friend in EfTex, who had plenty of dry oak bilkts, to af- ccrtain the quantity of alhes which a certain weight of the wood would yield. He made the experiment with every poflible precaution, and from 1 06 pounds, avoirdupois weight, of dry peeled ©ak, he obtained 1 9 ounces of afhcs. I treated thefe alhes after the fame manner in which I had endeavoured to afcertain the propor- tion of earth and falinc matter in barilla^ and kelp alhes i and from the
19
( ^33 )
19 ounces obtained rather more than one ounce and a quarter of fa- line matter. From feveral repeti- tions of the experiment with afhes of the fame kind it may be con- cluded, that 15 ounces of thefe afhes contained 14 ounces of earth, not foluble in water, and i ounce of faline matter: from this proportion it may eafily be colledled, that above 1300 tons of dry oak, and probably above 1800 tons of green oak, mufl be burned in order to obtain one ton of pot-afh.
The makers of pot-afh generally buy the wood afhes by the bulhel, and fell the pot-afh by the ton; but as the afhes of different woods, and indeed of different parts of the fame wood, probably contain very diffe- rentportions of faline matter; itcan- I J not
( 134 )
not be expefted that we iliould have any very uniform accounts of the Dumber of bufhels of afhes requifite to make a ton ofpot-afh. Some dealers in this article are of opinion, that a ton of pot-afli may be pro- cured from 400 bulheis of afhes -, others, from 4505 others, from 560 of the beft afties 3 and others, laftly, from 700 bufhels, at a medium, of good and bad afhes*. I find that a bufhel. of the dry afhes which are fold by the country people who burn wood to our foap-makers in Cam- bridge, weighs at a micdium 58 pounds : hence, fuppoiing every 1 5, pounds of fuch afhes to contain i pound of faline matter, it will fol- low, that 580 buflicls of fuch aflies
would
* Lewis's Experiments on American Pot* alli, p. 6,
( '35 )
would give I ton of faline matter.
This correfpondence with the ac- counts given by the pot-afn makers, confirms the analyfis of the oak alhes before mentioned.
Under the dire6tion and patronage of the Society for the Encourage- ment of Arts, Manufactures, and Commerce, large quantities of pot- alh have been made in America fince the year 1763 j and it would be a great faving to the nation, if it could be made in fufficient quanti- ties in any part of the dominions of Great Britain, fince we are reck- oned to pay to Ruffia, and other fo- reign ftates, not lefs than one hun- dred and fifty thoufand pounds a- year for pot-aih *. We have inex-
hauftible
* Doflie'* Mem* of Agricul. Vol. I. p. 248- *4 .
( 136 )
haullible mines of rock fait in this country, which the proprietors can afford at lo Ihillings a ton. A ton of rock fait, as has been before obferv- ed of common fait, contains about half a ton of mineral alkali, which is for moft purpofes far preferable to pot-alh. If a method could be contrived of extradting this alkaline part from rock fait, it would be a moft ferviceable difcovery. To thofe who have leifure to attempt it, I would give the following hint^ — Whether the alkaline part of rock fait may not be obtained by cal- cining it in conjunction with char- coal in open fires ; My reafon for this conjecture is founded on the follow- ing experiment : Upon burning fea wrack to a black coal, and flopping the procefs at that point,
I have
C IJ7 ) I have obtained great plenty of common fait, but no mineral alkali from the black afhes; though wc are certain, that when the black afhes are thoroughly calcined, or reduced to white afhes, mineral al- kali may be obtained from them. This makes it probable, that the common fait contained in the black alhes of fea wrack, is decompofed^ and changed into a mineral alkali^ during the burning of the black afhes. There are reafons to fuppofc that the cinder of pit-coal would anfwer the purpofe better than char- coal. But to return.
Tartar is a vegetable produ6tion, which forms itfelf on the fides of calks in which new wine is put; it is of a folid confiflency, and is thence called by the Germans, wine-flonej^
(wync-
C 138 )
(wyne-llein) : this fubflance, when burned to alhes, yields a very pure vegetable fixed alkali, called, Jalt cf tartar.
The reader is defired to diflin- guiih between cream of tartar and Jalt of tartar -, they are both falts, but not of the fame clafs. Cream of tartar is an acid^ and is prepared from tartar by diflblving it in water, and cryftallizing the folution. Salt of tartar is an alkali^ and is prepared from tartar by burning it, the acid being probably changed into an al- kali by the fire.
Salt of tartar, as well as all othet vegetable fixed alkalies when pure (for when purified they are all the fame), attrads very ftrongly the hu- midity of the air, and thereby melts as it were into a liquor^ which from
( 139 )
its being procured in this fingular way, and from its having alfo an undtuons appearance, tho' it has no other property of an oil, has been called Oil of tartar fer deliquium. If you fpread a little fait of tartar, or even common pot-afh on a plate, and expofe it to the air in a cellar or other moifr place for a few days, you will fee the whole of it almoft melt- ed aw^y into a thick tranfparent li- quor, weighing near four times as much as the weight of the fait you expofed. The mineral fixed alkali, expofed in the fame way, will not be changed into a fluids and this is one mark by which the mineral and ve- getable fixed alkalies may be diflin- guifhed from each other. Both of thefe fixed alkalies change the blue colour of fyrop of violets in to a green^
and
( I40 )
and by this property they are diftin- guifhable from acids, which give a red colour, as well as by their tafte, which is cauftic and fiery, every way very different from a four tafte. They bubble up alfo or effervefce when mixed with acids, as may be {^tn by mixing lemon-juice and fait of tar- tar together. This effervefcence pro- ceeds from the difcharge of an elaf- tic fluid, czWtd fixed airy but it can- not be faid to be chara6leriftic of al- kalies; fince chalk, marble, lime- ftonc, and other earths and ftones not foluble in water, contain a large por- tion of fixed aify and, when mixed with acids, effervefce as much as fixed alkalies. From this property, thefe earthy and ftony fubftancejs have, in many fyftems of mineralo- gy, been called alkaline earths and ftoixes. . Befid«s
( '41 )
Befides the fixed alkaline falts feparablc from the alhes of mari- time plants, and other vegetable fubflances, there is another fpecies of fait feparable chiefly from ani- mal fubftances, as from urine, horns, bones, &c. by diftillation. This fait effervefces with acids, and gives a green colour to vegetable blues, and it is from hence called an alkali j but being eafily diffi- pated in a fmall degree of heat, it is called a volatile alkali. By this great volatiiity it is fufficiently di- ftinguifhed from the two fixed al- kalies, as well as by the pungency of its fmelli fixed alkalies, when pure^ having no fmell.
OF
( 142 )
OF NEUTRAL SALTS. Neutral falts are diftinguiihed both from acids and alkalies by their tafte, which is neither » four nor cauilic, by their not efferve- fcing with acids, by their not pro- ducing any change in the colour of .fyrop of violets. Of this kind arc connmon fait, Glauber's fait, fait- petre, and a great variety of others. Any acid, when united with any al- kali in fuch proportion that the compound does not polTefs any of the charaderiftic properties of ei- ther of its component parts, is a neutral fait. The term neutral, was firil applied to a fait formed by an \inion of an acid and an alkali; but it has now a more extenfive fignifi- cation, denoting the fait formed by
the
( 143 )
the union of an acid with any alkali, earth, or nnetallic fubflance. The fubftance with which the acid unites itfelf in the formation of a neutral fait, is often called the hafis of that fait.
The following tables of falts will help to fix in the reader's mind the general divifion of faline fubflances, efpecially if he will be at the trou- ble to familiarize himfelf to the iiames, by procuring from his drug- gift fpecimens of the feveral kinds.
A Table
( H4 )
A TABLE OF SALTS IN GENERAL.
( 145 )
A Table of neutral Salts, with Alkaline Bafcs.
ACID.
( 146 )
It may not be improper, in this place, to mention two proportions much infilled on by chemical writers of the greatefV eminence, but which appear to be founded rather on pro- bable conjecture than certain expe- riment. The firil is, that the vitri- olic acid is the only faline principle in nature, all other acids, and alkalies being nothing but combinations of this univerjal acid with earth, air, oil, and water, in different propor- tions. The fecond is, that the vi- triolic acid itfelf is a compound body, formed from an intimate union of ea>rth and water. The pofTibility of the truth of the firft propofition, which alTerts, that one fubftance may be fo combined wdth feveral others as to conilitute a great variety of different compounds, may be il-
luftrated
( H7 ) luflrated from what we knov/ of
waterj which is the chief conftitu- cnt part of bodies in appearance very different from each other, as of blood, urine, milk, wine, wood, coal, &c. yet the marine acid feems to be as abundantly difFufed over the earth as the vitriolic; and can- not, I think, be faid to. be derived from it. As to the fecond propor- tion, though we fhould grant that nothinsr but earth and water can be
o
procured from the analyfis of any fait, (which, confidering the lofs fuftained almoft in eveiy analyfis from the efcapc of fome elaftic fluid which cannot be condenfed, cannot .readily be admitted;) yet as no one could ever form a faline fubilance by uniting earth and water together, we may fairly doubt concerning its -K -2 truth :
( hS )
truth: this doubt, however, is not to be underflood as a denial. The fum of the matter is this : earth and wa- ter cannot be formed by us into fa- line fubftances : nature may have different modes of combining them, fo as to produce the effeft; or na- ture mayy in producing the effe£b, make ufe of a third or a fourth principle. It mu'ft be left to future experience to fimplify our know- ledge concerning faline fubftances, as well as concerning thofe fluids 'which produce magnetifm and elec- tricity, and all the various pheno- mena attending mineral exhala^ tions*
ESSAY
ESSAY IV.
•F FIRE, SULPHUR, AND PHLOGISTON.
FIRE is fo fubtile an agent in nature, that we can reafon lit- tle concerning it, except from ex- periment; and we are even at a lofs from thence to determine, in many cafes, either its abfolute quantity or real prefence. If, with the ge- nerality of philofophers, we aflume heat as its charaderiftic property,, and define fire p be that which warms or heats bodies, we cannot avoid feeing at once, the ambiguity^ of this criterion: it is as precarious as the perceptions of different men K 3 at
( 150 ) at the fame time^ or of the fame
man at different times, in fummer and in winter, in a fever and in health. The light of the moon, when colledted ifito the focus of a Targe burning- glafs, is found to be about one thoufand times lefs denfe than the dire6t rays of the fun : hence it is, that it excites no mo- tion in the mercury of the moli fenfible thermometer. But from thet brightnefs of the image in the focus^ as well as from the luminous ap- pearance of rotten wood, putrid fifh, and other phofphorefcent bodies^ fome philofophers have inferred,, that wherever there is light there i$ fire : but as the converfe of this pro^ pofition is not true, fince fire oftei> exifts in large quantities, as in boil* ing fluids, in metaU* moderately
heated^
( 151 )
heated, &c. without light; this can- not be a diflinguifliing mark of the prefence of fire. The dilatation which fire occafions in all bodies, whether folid or fluid, hard or foft, light or heavy, may be efteemed the mofh certain proof of its prefence and agency. This property ferves admi- rably to mark its degrees and mi- nute variations within certain li- mits, but not to afcertain either its prefence or its quantity in extreme cafes, unlefs we know the real mag- nitudes of bodies totally dellitute of it. However, admitting this phenomenon aa the moil certain indication of the exiftence of fire, it may be accounted for in the fol- lowing manner.
From the 14th feclion of Sir Ijaac
Newt on' % Priucipidy we learn, that
K 4 the
( »53 )
the motions of fmall bodies, v/hen attra(5ted perpendicularly towards any furface, according to any law, arc finnilar to the motions of the rays of light, with refpedt to the fundamental properties of Inflec- tion, Reflexion, and Refradtion : from hence chiefly, as well as from other arguments, we infer, that rays of light are fmall corpufcles, emit- ted from jQiining bodies, and moving with uniform velocities in uniform mediums j but with variable velo- cities in mediums of variable den- iities. This being admitted, it will follow, that in whatever quantity the rays of light are made to move' in a medium of an uniform denfity^ they will not agitate the particles^ or produce any augmentation of bulk in that medium, ^If the atmo-
fpherc
( '53 >
fphere was reduced to a medium of
an uniform denfity, furrounding the earth every where to the height of five miles, it would be expanded in bulk, or warmed only at its out- ward and inward furface. The fun's rays, by coming out of a vncuum- into a denfer medium,, would be attraded by the particles compofing that medium; and, fmce all attrac- tion is mutual, they would excite a motion, an expanfion, an heat, at the outward furface where they en- tered : from thence they would pro- ceed uniformly, without producing any efFed, till they came to the in- ward furface of the atmofphere con- tiguous to the furface of the earth, where they would undergo another acceleration of velocity, and would excite another degree of motion,
another
I
( 154 )
another degree of expanfion or heat. Such an atmofphere would be the coldeft in the middle, the heat de- creafing from each furface. Wc may, perhaps, from what has been faid, conceive, in fome meafure, how bodies are expanded, heated, and volatilized, by the agency of the particles of light. Thefe particles ad upon the minute conftituent parts of bodies, not by impad, but at fome indefinitely fmall diftance ; they attrad, and are attraded; and in being refleded, or refradted, they excite a vibratory motion in the component particles. This motion increafes the diftance between the particles 3 an increafe of the diftance between the conftituent parts of any body, is an augmentation of bulk, an expanfion in every dimen-
fion.
( 155 )
fion, — the moft certain charadlerlftic of fire. This expanfion, which is the beginning of a difunion of the parts being increafed by the in- creafing magnitude of the vibra- tions proceeding from the con^ tinned agency of the light, it may cafily be apprehended^ that the par- ticles will at length vibrate beyond their fphere of mutual attraftion,. and thus the texture of the body will be altered or deftroyed: frotti folid it may become fluid, as in melted goldi or from being fluid, it may be difperfed in vapour, as in boiling water.
According to this theory, we muft infer, that the conftituent parts of all bodies are in perpetual motion. The temperature of the atmofpherc is different in different latitudes^ and
k
( 156 )
It changes, almoft every inftant, m the fame. The temperature of bodies is ever proportionable to that of the furrounding atmofphere, and from thence it muft be perpetually vary- ing. The bulk of every body is pro- portionable to its temperature, and muft therefore be fubjed to a per- petual vicilTitude. Now the body will be in an expanded, in the next inftant, its heat happening to be diminifhed, it will be in a contra6l:- ed ftatej which variation of dimen- lions cannot be effedled without a perpetual vibratory motion of its conftituent parts.
It being eftablilhed then, that the rays of the fun, even in their moft condenfed ftate, as in the focus of a burning fpeculum, do not otherv/ife produce heat than as they excite 4
motion
( ^57 ) motion more or lefs violent amongft the conftituent parts of bodies s and the efFeds of culinary fire, of that produced by fridlion, or by the im- pad of hard bodies, being fimilar to thofe produced by the agency of the fun's lights it may be conjec- tured, that they are produced after a fimilar manner; and that fire is nothing diftin6t from the parts of bodies put into motioia by various caufes, as the impulie of light, fridlion, percuffion, putrefadlion, attradion of cohefion^&c. and con- sequently that it may be mechani- cally produced, altered, or deftroy- cd in all bodies, with greater or lefs facility, according ^as the parts of the body are more or lefs difpofed for motion.
This conclufioa fcems to be con-
fonant
\ _ ( 158 )
fonantl with the principles of the re- ceived |)hilofophy. Newton in his 5 th qu^re annexed to his Optics, alks, D9 not bodies and light ad
-mutually^ upon one another? that is to fayy\bodies upon light in emit- ting, refic6ting, refrading, and in- flecting it^ light upon bodies for heating them, and putting their parts into \ a vibratory motion, wherein heat; confifts ?
There areWarious other opinions concerning the nature of fire and its method of ailion, which, though different from> what has been of- fered, are not |efs probable : I will content myfeli' with mentioning two more. \
Boerhaave thinks that fire is a, fluid of a nature! peculiar to itfelf; that it was createql fuch as it is, and
cannot
y ( ^s^ )
cannot be altered in its nature or properties, deftroyed or produced; that it naturally exifts in equal quan- tities in all places; that it is wholly imperceptible to ourfenfes, and only difcoverable by liich effects as it produces^ when by various caufes, it is for a time colledled into a lefs fpace than what, from its tendency to an univerfal and equable difFufion^ it would otherwife occupy. All the bodies which are fituated in the im- menfity of fpace., may according to this opinion, be divided into fire ex- panding all other bodies, and into all the other bodies which are not fire^ but refill its adion. The matter of this fire is not fuppofed to be derived from the fun in any wife; the folar rays, whether direct or refledted, are ^f ufe only as they impel the particles
( i6o )
of fire in parallel dire6tions : that pa- rallelifm being deftroyed, by inter- cepting the folar rays, the fire in- ftantly refijmes its natural ftate of uniform difirifion*. Confiflent with this explication, which attributes heat to the matter of fire, when dri- ven in parallel directions, a much
greater * Poflent omnia corpora locata in fpatio immenfo dividi, in ignem expandentem om- nia reliqua corpora, et in cetera univerfa corpora quae non funt ignis — Ignem il- ium femper elTe ubique praefentem, tam in pleno corporeo pleniffimo quam in vacuo inaniffimo ■ ■ Ignem hunc sequabiliffimc diftribui tamdiu, quamdiu non n^fcitur cau- fa fingularis in loco certo ignem hunc dif-
perfum coliigens Ignem hunc non efle
a fole, quoad materiam uUo modo — Vim ignis a fole determinatam in rectas parallelas remanere in omni tempore, quo emanatio
vel reHexio durat intercepta redlitudine
radiorum a fole, ignem in parallelifmum agentium, illico cefTat ille parallelifmus, at- que ftatim illo ipfo momento ignis partes expanduntur sequabiliter quaquaverfum.— £oerh. Chem, Vol. i.
( lei )
'greater muft be given it, when th« ■quantity fo colleded, is amafled into a focus 5 and yet the focus of the largefl fpeculum does not heat th-e air, or medium in which it is formed, but only bodies of denfities diffe- rent from that medium.
The author of the Lettres Thy- ftques is of opinion, that the folar rays are the principal caufe of heat; but that they only heat fuch bodies as do not allow them a free paf- fage *. In this remark he is agreed With Newton f; but then he differs totally from him, as well as from Boerhaave, concerning the nature of
the
* Les rayons du foleil n' echauffent les corps qu* entant que les corps ne leur accor- dent iin libre paflage a travers. Lett. Fhyf.
t Radii folis non agitant media qus permanant, nifi in reflexione et refra^tione.
Newt. VOL. I, L
I
{ x6i ) tlie rays of the fun. He does not admit the emanation of any lumi- nous corpufcles from the fun, or other felf fhiningfubftances,butfup^ pofes all fpace to be filled with an aether of great elafticity and fmall denfity, and that light confifts in the vibrations of this sther, as found confifts in thie vibrations of the air; the particles of th« one medium ex- citing, by impulfe upon the organ of vifion, the idea we call light; the particles of the other medium ex^ citing, by impulfe on the organ of hearing, the idea we call found *» But as a bell will not of itfelf begin
thofe
* La lumiere n^eft autre chofe qu' une agi- tation ou ebranlement cause dans les parti-
cules de 1' ether qui fe trouve partout.
il n'y a done rien qui vienne adtuellement du foleil jufque a nous. Let, Phy>
t 163 )
thofe vibrations by which the air iSi put in motion, nor continue with equal intenfity the vibrations, when once excited, without the concur- rence of fome mechanical caufe -, fo neither will the fun either begin or continue his vibrations, by which the fuppofed ^ther is put in motion, without a fimilar mechanical agency. In afcending from efFeds to caufes we muft ever arrive, upon whatever hypothefis we proceed, at fome firil caufe, which does not admit an ex- planation from mechanical princi- ples; this is evidently the cafe in the prefent enquiry. Upon Newton's fuppofition, the caufe by which the particles of light, and the corpufcles conftituting other bodies, are mutu- ally attraded and repelled, is uncer- tain. The reafon of the uniform L 1 difFufion
( i64 )
difFufion of fire, of its vibration, and repercuflion, as fbated in Boer- haave's opinion, is equally inexplica- ble; and in the lafl mentioned hypo- thefis, we may add to the other diffi- Gillties attending thefuppofition of an univerfal ^ther, the v/ant of a firft mover to make the fun vibrate. Thefe are the opinions moll worthy of notice, concerning elementary fire; and of thefe it may be faid, as Cicero remarked of the opinions of philofophers concerning the nature of the foul, — harum Jententiarum qua V era fit y Deus aliquis viderit^ qua ^erifimillimay magna qiiejiio eji^.
But
* The reader who is defirous of making a deeper inquiry into this raatter, may confuk a very ingenious tra£t, entitled, Experiments and Obfervations on anim.al Heat, and the Inflammation .of combuilible Bodies, by Dr
Crawford;
I
( i65 )
But befides this elementary Jirey. which chemifts conceive to be every where uniformly diffufed, they are of opinion that fire enters, in dif- ferent proportions^, into the compo- fition of all vegetables and animals, and moft minerals; and in that con-^ denfed, compa6led, fixed date, it has
been
Crawford; and Mr. Scheele's Experiments on Air and Fire, tranflated from the Ger- man by Dr. Forfter, and iliuftrated with judi- cious notes by Mr. Kirwan ; and a late work, of Wallerius', entitled Meditationes de Orig-. Mund.
May not the common degree of heat which: arifes from the mixture of different quantities of the fame fluid heated to different degree?^. be inveftigated by the fame rule^ by which the common 'velocity of hard or non-elailic bodies after their impacl in the fame direction is calculated, putting the momentum of heat to be equal to its degree multiplied into tila. quantity of heated matter ? L3
( i66 )
been denominated the phlogtfioft. Of itfelf, in its natural Hate of unr combined expanfion^ fire is not efteemed capable of fhining, or burn- ing; when chemically conjoined with the other principles of bodies, it is that alone which conceives and con-' tinues thofe motions by which bodieS' are made to ihine, to burn, to con- fume away. All bodies are more or lefs fufceptible of combuftion, ac- cording to the qu antity of this princi- ple which enters into their compo- fition, or the degree of force with which it adheres to them. Intheadt of burning, and it may very probably be during the fermentation, andpu- trefadlion, and chemical folutions of various bodies, it recovers its fluidi- ty, is expanded and difperfed into the air, or combined anew with fuch
fubftanees
C i67 )
fubftances as it has an attra6lion to. Notwithftanding all that perhaps can be faid upon the fubjedt, I am fenfi- ble the reader will be Hill ready to aflc — what is phlogijlon ? You do not furely exped that chemiftry Ihould be able to prefent you with a hand- ful of phlogiflon, feparated from an inflammable body; you may juft as reafonably demand a handful of mag- netifm;, gravity, or eie(5lricity to be extradled from a magnetic, v/eighty, or eledtric body. There are powers in nature which cannot otherwife become the objeds of fenfe, than by the efFeds they produce; and of this kind is phlogifton. But the follow- ing experiments will tend to render this perplexed fubjed fomewhat more clear.
If you take a piece oijulfhur^ L 4 and
( i68 ) and fet it on fire, it will burn-intire^ ly away, without leaving any afhes,. or yielding any foot. During the burning of the fulphur, a copious vapour, powerfully aftedling the or- gans of fight and fmell, and the ac- tion of the lungs, is difperfed. Means have been invented for collecting this vapour, and it is found to be a very flrong acid. The acid thus procured from the burning of ful- phur, is incapable of being either burned by itfelf, or of contributing towards the fupport of fire in other bodies : the fulphur frona which it was procured was capable of both : there is a remarkable difference then,, between the acid procured from the fulphur, and the fulphur itfelf. The acid cannot be the only conflituent part of fulphur 3 it is evident that
Jomething
( i69 )
fomething elfe muft have entered inta its compofition, by which it was ren- dered capable of combuftion. This Jomething is, from its moft remark-- able property, that of rendering a body combuflible, properly enough denominated the food of fire, the inflammable principley the phlogiflon.
From this analyfis we may con- clude, that the conftituent parts of Julphiir are two ; — an inflammable principle, which is difperfed in the a6t of combuftion, and an acid. The proportion of thefe parts has beea afcertained; and it is found, that in any mafs of fulphur, the weight of the inflammable principle is to that of the acid in the proportion of 3 to -50 *.
If * The experiment from which this pro- portion is derived, is faid to have been made
by
( I70 )
If you burn charcoal in the opeit air, and hold a glafs over its flame, you will perceive that it burns with- out emitting either any watery va- pour or footy impurity; and nothing will remain, from a large portion of charcoal, but a fmall portion of white afhes, which are incapable of any further combuftion. The principle effeding the combuftion of the char- coal, and difperfed by the ad of com- buftion, is the phlogifton.
If you fet Jprits of wine on fire, they will, if pure, burn intirely away : they differ from charcoal in
this,
by W, Brandt with great accuracy about the year 1756, Spielm Chem. p. 1 1 1! and Chan", Di6t. — ^Newman from a limilar experiment infers, that in 16 ounces of fulphiir, there arc upwards of 1 5 | ounces of pure acid, and not quite \ of an ounce of the inflammable prin? ciple. Newm. Chem. p. 1.68.
( i7r )
this, that they emit a vapour: but
they leave no reiiduum. You may by proper vefTels colle6b the vapour of burning fpirits^ and you will find it to be an infipid water, incapable of eombuftion. The principle effed- ing the combuflion of the fpirits of wine, and difperfed by the a6t o£^ combuflion, is the phlogiflon.-
Somtmetallkfuhftanees burn, wheri' fufHcientiy heated, with a flame more bright than that of fpirits of wine, or charcoal ; others burn or fiBother away like rotten wood; and mofl of them, when they have been kept in the open air in a proper de- gree of heat, lofe their metallic ap- pearance, and are converted into earth. Thus red lead is the earth pro- cured from the burning of lead; and ^«//j,fuchasthepolifhersofglafsand
marble
C 172 )
marble ufe, is the earth procured from tin. The principle efFe6ling the combuflion of metallic fubflancesy and difperfed in the a6l of combuf- tion, is the phlogifton.
The acid of the fulphur ', the ajhes ef the charcoal', the water ef the Jphits of wine; the earths of metallic Juhftances, are utterly incapable of Combuftion : their refpedlive dif- ferences from fulphur, charcoal, fpi- rits of wine, and metallic fubftances, with refpe6l not only to inflamma- bility, but to fmell, colour, confiil- ency, and other properties, are at- tributed to the phiogifton which is difperfed during the combuftion of each of them.
This inflammable principle, or phiogifton, is not one thing in ani- mals^ another in vegetables, another
in
( 173 )
In minerals, it is abfolutely the fam«J in them all; juft as water which en- ters into the compofition of fleih, wood, coal, is ftiil water, though its , exiilence and homogeneity be ren- dered more doubtful in fome fub- Hances than in others. This iden- tity of phlogifton may be proved from a variety of decifive experi- ments; I will feledl a fev/, which may at the fame time confirm what has been advanced concerning the con- ftituent parts of fulphur.
From the analy fis ordecompofition of fulphur efiedbed by burning, wc have concluded, that the conilituent parts of fulphur are two, — an acid v/hich may be colleded, and an in- fiammahle principle which is difper- fed. If the reader has yet acquired any real tafte for chemical truths^
he
( 174 )
he will wifh to fee this analyfis con* firmed by fynthefis ; that is, in com- mon language, !ie will wifli to fee fulphuraftu ally made, by combining its acid with an inflammable princi- ple. It feldom happens that che- mifts can reproduce the original bo- dies, though they combine together all the principles into which they have analyfed them ; becaufe not only the number and proportions of the principles, but the order alfo of their arrangement muft be obferved, before that can be effeded : in the inftance, however, before us, the re- produ6i:ion of the original fubflance will be found complete.
As the inflammable principle can- not be obtained in a palpable form feparate from all other bodies, the only method by which we can at- tempt
( 175 ) tempt to unite it with the acid of fulphur, muft be by prefenting to that acid fome fubftance in which it is contained. Charcoal is fuch a fnbllance, and by diftilling powder- ed charcoal and the acid of fulphur together, we can procure a true yel- low fulphur^ in no wife to be diftin- guilhed from common fulphur. This fulphur is formed from the union of the acid with the phlogifton of the ^charcoal ; and the charcoal may by this means be fo entirely robbed of its phlogifton, that it will be reduced to afhesj as if it had been burned. Animal fubftances reduced to the ftate of a black coal, will, by being treated in the fame way, yield ful- phur.
Spirits of wine, we have faid, con- ^ift of phlogifton united with water;
and
( 176 )
and if we diftil a mixture of Ipirits of wine and the acid of fulphur, we •fhall towards the end of the opera- tion obtain a pure fulphur.
Oil of turpentine is very inflam- mable, and confequently abounds with the principle which has been denominated phlogifton ; and from a <iiflillation of acid of fulphur with oil of turpentine, a fulphur- may be procured.
But one of the fhorteft and moft obvious ways of illuilrating both the compofition of fulphur and thephlo- giflon of metallic fubfiiances, is the following. — Upon miClted lead pour the acid of fulphur j colle<5t the va- ;pour which will arife, by holding a very large glafs or other velTel over the melted lead, and you will, asfoon .as the vapour is condenfed, obferve
feveral
( 177 ) fereral filaments of fulphur flicking
to the fides of the glafs. — When lead is in a jRiate of ftrong fufion, its phlogifton is in a ftate of dif- perfion; the acid of fulphur inftan- taneoufly unites itfelf with this phlogifton;, and forms fulphur. It is probable, that fulphur might be procured by the fame means from a variety of other bodies, when in a ftate of adual combuftion.
I will in this place, by way of further iliuftration of the term phlogifton, add a word or two con- cerning the necefTity of its union with a metallic earth, in order to conftitute a metal.
Lead, it has been obferved, when melted in a ftrong fire, burns away like rotten wood -, all its properties .as a metal are deftroyed, and it is
wou !• M reduced
( ^8 ) reduced to alhes. If you expofe tKc afhes of lead to a ftrong fire, they will melti but the melted fubftancc will not be a metal -^ it will be a yellow or orange- coloured ^/^yj. If you pound this glafs and mix it with charcoal dufl, or if you mix the afhes of the lead with charcoal dufl, and €xpofe either mixture to a melting heat, you will obtain, not a glajsy but a metaly in weight, colour, con- fiflency, and every other property the fame as lead. This operation by which a metallic earth is reflored to its metallic form, is called Reduc* tion. The afhes of lead melted with-^ cut charcoal become glafs ; the afhes of lead melted with charcoal become a metaly the charcoal then mufl have communicated/c;;^^/^/;;^ to the afhes ©f lead, by which they are changed
from
t 179 )
from a glafs to a metal. Charcoal confifls but of two things, of afhes, and of phlogifton ; the ajhes of char- coal, though uaited with the afhes of lead, would only produce glafs ; it mull therefore be the other conili- tuent part of charcoal, or phlogifton, which is communicated to the allies of lead, and by an union with which thealhes are reftored to their metallic form. The afhes of lead can never be reduced to their metallic form, without their being united with fom.e matter containing phlogifton; and they may be reduced to their me- tallic form, by being united with ■any fubftance containing phlogillon in a proper ftate, whether that fub- ftance be derived from the animal, vegetable, or mineral kingdom; {for tallow or iron filings may be M 2 fub-
( i8o ) fubftituted with fuccefs in the room of charcoal, in the experiment of re- ducing the aihes of lead) and thence we conclude, not only that phlogif- ton is a neceflary part of a metal, but that phlogifton has an identity belonging to it, from whatever fub- stance in nature it be extradled. And this afTertion ftill becomes more general, if we may believe that me- tallic afhes have been reduced to their metallic form, both by the fo- iar rays and the eledbical fire*
ESSAY
ESSAY V.
OF THE ORIGIN OF SUBTERRANEOUS FIRES.
THE moft remarkable^changes which have taken place in the form and conftitution of the earth, fince the deluge, have probably- been produced by fubterraneous fires J for it is to their agency that philofophers afcribe volcanos and earthquakes; thofe tremendous in- llruments of nature, by which fhe converts plains into mountains, the ocean into iflands, and dry land into ftagnant pools.
M 3 Dr.
I
( IS2 >
Dr. Hooke formerly had main- tained that all land had been raifed out of the fea by earthquakes j and modern philofophers feem to admit his hypothefis, though not, perhaps, in its utmoft latitude. Thus one of them is of opinion, that Iceland, which is bigger than Ireland^ has been produced by volcanos in the courfe of feveral centuries*. Ano^ ther, after giving an ingenious con- je6ture concerning the origin of alt the tropical tow ijles in the South Sea^ afiures us, that of the higher ijles^ there is hardly one of them which has not ilrong veftiges of its having undersione fome violent aiteratioiJ by a volcano. Some of them have volcanos ftill fubfifling; others,
amongft
"i
* See Letters on Iceland by Dr. Uno Von-
Tcoil, p. 22 2*
C I8J )
• amongtt which are 0-Taheitee and Huaheiney feem to have been ele- vated, in remote ages, from the bot- tom of the fea by fubterraneous fires *.
When thefe fires were firft kind- led ; by what fort of fuel they are ftill maintained; at what depths be- low the furface of the earth they are placed ; whether they have a mutual communication i of what dimenfions they confift; and how long they may continue, are queftions which do not admit an eafy dccifion. The fur- face of the earth is admirably fitted for the fupport of the exiftence and well-being of all the. animals which M 4 inhabit
* Obfervations made during a Voyage round the World by Dr. Forller, p. 151 ; where the reader will find in a note, a learn- ed reference to the works of a great many authors, on the fubje^l of ifles raifed out of theiea by the adion of a fubterraneous fijre.
( ^H )
inhabit it. God has given us the abi- lity alfo to penetrate a very little be- low this furface^ and as the reward of our induftry, he has placed with- in our reach a great variety of ufe- ful minerals ; but as to the central recefTes of the globe, we can never penetrate into thenn. A gnat efTay- ing the feeble efforts of its {lender probofcis againft the hide of an ele- phant, and attempting thereby ta inyeftigate the internal formation of the body of that huge animal, is no< wnapt reprefentation of man at- tempting to explore the internal ilrufture of the earth, by digging; little holes upon its furface.
But though it will ever be im- poffible for us to fearch far into thcr bowels of the earth, or to imitate, in an extenfive degree, the great ope-
rations^
C 185 >
Nations which are conflantly carry- ing on beneath its furface, yet it affords a curious mind no mearv degree of fatisfa6tion to be able, by obvious experiments, to form fome reafonable canje6tures concerning; them.
Mr. Lemery*, as far as I have been able to learn, was the firft per- fon who illuftrated,. by adual expe- riment, the origin of fubterraneous fires. He mixed twenty-five pounds. oi fowdered Jul;phur with an equal weight of iron filings y and having kneaded the mixture together, by means of a little watery into the con- fiftence of a pafie, he put it into an iron pot, covered it with a cloth,, and buried the whole a foot under
ground..
* Cours de Chemie, p. 176. & Mem. de. TAcad. des Scien. a Paris, Ann. 1 700..
( i86 )
ground. In about eight or nine hours tinrie the earth fwelledj grew warm, and cracked ; hot fulphure- ous vapours were perceived ; aflame which dilated the cracks was ob- ierved ; the fuperincumbent earth was covered with a yellow and black powder : in fhort, a fubterraneous fire, producing a volcano in minia- ture, was fpontaneoufly lighted up from the reciprocal a6i:ions of ful- phur, iron> and water.
That part of this experiment which relates to the produdllon of fire, by the fermentation of Iron filings and fulphur when made into a pafte *, has been frequently re- peated
* The words ferment and fermentation may perhaps be improperly applied to the fponta- neous tranfpofition of parts, which takes place in mineral fuhftancci ; but the reader cannot fail to iinderftand what is meant by them wheft thus applied.
1
( i87 ) peated fince the time of Mr. Le*-
mery. 1 myfelf have made it more than once, but I have nothing ma- terial to add to his aecountj except: that the flame, when the experiment is made in the open air, is of very fhort duration ; and that the whole mafs, after the extindbion of the flame, continues at intervals, for a longer or Ihorter time, according to its quantity, tothrowout fparks j and that a ladle full of the ignited mafs,. being dropped down from a confi- derable height, defcends like a fhow-^ er of red-hot alhes, much refembling the paintings of the eruptions of Mount Vefuvius which may be feen at the Britiih Mufeum. It has been obferved, that large quantities of the materials are not requifite to make the experiment fucceed, pro- vided
( i8S )
vided there be a due proportion of water : half a pound of fteel filings, half a pound of flowers of brim- flone, and fourteen ounces of wa- ter, will, when well mixed, acquire heat enough to make the mafs take fire*.
That heat and fire fhould be ge- nerated from the fpontaneous aftions of minerals upon each other, is a phenomenon by no means fingular in nature, how difficult foever it may be to account for it. The heat of putrefcent dunghills, of the fer- menting juices of vegetables, and, above all, the fpontaneous firing of hay not properly dried, are obvious proofs that vegetables pofTefs this property as well as minerals. In both vegetables and minerals, a de- finite * Sage Miner. Vol. I. p. 42.
C 189 )
finite quantity of moifture is requi- fite to enable them to commence that inteftine motion of their parts, which is neceffary for the produc- tion of fire. Iron and fulphur would remain mixed together for age* without taking fire, if they were either kept perfctSlly free from moifture, or drenched with too much water j and vegetables in like manner, which are quite dry, or exceedingly wet, are incapable of taking fire whilft th^y continue in
that ftate *.
But
* Animal fubHances, when lakl on heaps, have been obferved to take fire. ^' M. Mon- tet rapporte dans I'hiftoire de T Academic Royale des Sciences, annee 1776, que des pe- tites etofFes appelles imperiaks^ gardees en tas, prirent feu d* elles-memes." Inflruc. fur 1' ufage de la Houille par M. Venel. It as not improbable that filings^of copper and
other
( 190 )
But though it is certain from the «xperiment, that mixtures of iron and fulphur^ when moiftened with a proper quantity of water, will fpon- taneoully take fire ; yet the origin of fubterraneous fires cannot, with ^ny great degree of probability, be referred to the fame principle, un* lefs it can be fhewn that nature has combined together in large quanti- " ties iron and fulphur, and diflri- buted the compofition through va* rious internal parts of the earth.
Now that this is really the cafe wc ^an have no doubt. There is, per- haps, no mineral more commonly
met
other metals, when mixed in a due propor» tion with fulphur and water, would acquire a heat, and perhaps take fire, efpecially if the quantities were large ; but experiments -of this kind have not hitherto been made*
( 191 )
met with than that which is com- pofed of iron and fulphur. It is found not only upon the furface of the earth, but at the greateft depths below it, to which mines have been hitherto driven ; not only in En- gland or Italy, Europe or Afia, but in all parts of the world. This mi- neral is called in fome parts of England, copper as-Jione ; in others, ■brazil ; in others, ha/s-lumps ; m others, rufl-balls ; in others, horje- gold \ in others, marcaftte \ though naturalifts are now, I think, agreed to give that name to fuch mineral bodies as are angular and cryftal- lized, efpecially into a cubical form. The fcientific name is Pyrites ^ — Jiery ; a denomination expreffive 'enough of the property which this
mineral
( 192 )
Tnlneral has of ftriking fire with Heel, and of fpontaneoufly taking "fire, when laid in heaps, and moiften- ^d with water.
Sulphur and iron are the chief conftituent parts of the pyrites ; arfe- nic, however, is fometimes united with the iron inflead of fulphur, and fometimes fulphur and arfenic are both of them combined with iron. The pyrites alfo, accidentally, con- tains copper, filver, and perhaps, gold : hence the pyrites has been diftinguiflied by mineralogifts into various forts, by attending, either to its internal conftitution, as the iron, the copper, the fulphureous, the arfenical pyrites ; or to its external figure, as the pyramidal, the cubical, the ipherical, the prifmatic pyrites j
or
( ^93 )
or to its colour, as the grey, white, yellowifh, yellow, orange pyrites *.
Though the reader may have never contemplated the various fpecies of the pyrites in any cabinet of natural hiftory, or taken notice of fuch kinds as are commonly to be met with in chalk-pits, in beds of clay, or upon the fea ihore in many places of En- gland, yet the yeliowifh matter, often adhering to, or mixed with the fub- llance of pit-coal, cannot, furely, have efcaped his obfervation : that matter confifts of Julfhur and iron^ and is a fpecies of the pyrites. So
much
* Whoever wifties to become fully ac- quainted with the natural hiftory of the py- rites, may confult the Pyritologla of Heuckei, where he will find the origin, nature, and ufes of this mineral inveftigated with the greateft learning and ingenuity. VOL. 1. N
( 194 ) much of this fort of the pyrites is dug up together with the coal, at Whitehaven, Newcaftle, and other places, that people are employed to pick it out from amongft the coal, left it fhould vitiate its quality, and render it lefs faleable. The pieces of the pyrites which are feparated from the coal, are not thrown afide as ufelefs, but laid in heaps, for a purpofe to be mentioned hereafter ; and th^fe heaps, not many years fince, took fire both at Whitehaven and in the neighbourhood of Halifax. The fame accident was obferved above a hundred years ago at Puddle Wharf in London, where heaps of coal which contained much of this pyrites took fire*.
Though Lemery was the firft
perfon * Jorden of Miner. Wat, C, xiv.
( m )
pcrfon who, by artificial mixtures of fulphur and iron, produced fire, yet that natural mixtures of thefe fubftanccs would Jpoyitaneoujly tale JirCi was known before he made his experiment. Thus, to omit what is faid by Pliny and the ancients, we are told by good authority, that one Wilfon at Ealand'm Txirkjhire^ about the year 1664 or before, had piled up in a barn many cart-loads of the pyrites, or brafs-lumps, as they were called by the colliers, for fomc fecret purpofes of his own : the roof of the barn happening to be bad, the pyrites were wetted by the rain j in this ftate they began to fmoke, g,nd prefently took fire^ and burned like red-hot coals*.
We have an account, in the Phi- N 2 lofophical
* Power's Micrcf. Obfer, p. 62*
( 196 )
lofophical Tranfadions for i693f, of a covetous mafter of a copperas work at Whiteftahle in Kent^ who, in order to break his neighbour's work, had engrofled all the pyrites or copperas-flone in the country : he built a Ihed over two or three hun- dred tons of thefe ftones, to keep off the rain. In the fpace, however, of fix or feven months, themafs (being probably wetted by the moiflure of the atmofphere, or by the rain, which, notwithftanding the fhed, might have fallen upon it) took jire and burned for a week ; it quite deftroyed his fhed, and difappointed all his hopes of profit i for the pyrites was in part converted into a fubftance like melt- ed metal, and in part it looked like red-hot fl:one5 : all the fulphur was
con- f No. 213,
( 197 )
confumed, and the neighbourhood was miferably afflidled by the noxious exhalation which it fent forth.
In the month of Augufl 175 1 3 the Cliffs near Charmouth in Dorjetfmre took fire ^ in confequence of a heavy fall of rain after a hot and dry fea- fon, and they continued at intervals to emit flame for fever al years. — Thefe Cliffs confift of a dark-colour- ed bituminous loam, in which are im- bedded large quantities of different kinds of the pyrites. The fame kind offlame has been frequently obferved in the CorniJJj mines, and this mine- ral fire fometimes leads to the dif- covery of a mine j but wherever it is found to exili, the iron pyrites is generally difcovered near it*.
There * Philof. Tranf. Vol. LII. p. 119. N 3
( 198 )
There are fome forts of eartfe
frorri which alum is made, which abound fo much with the pyrites, that the proprietors of the works arc forced to keep them conftantly well watered, in order to prevent their taking fire*,'— But it would be ufc- lefs to purfue this fubjedl further j we have adduced proof fufficient, that nature furnifhes materials, which^ under certain circumftances, majr become theoccafion of fub terraneous- tires. The requifite circumftancei are a proper quantity of the mate- rials, a proper portion of water to moiften them, and, perhaps, a com- munication with the air may be nc- cefTary. A fmall quantity of the py- rites
* Waller. Min. Vol. T.. p. 25..— Henckci ^Pyritoi. p. 312. — Minera. par M» Yal.- dc Bomare, Vol. I, p. 296*
( 199 )
rites is fufficient to kindle a fire;
water is almoft every where found in fuch great plenty below the fur- face of the earth, that it conftitutes one of the greateft impediments to our finking pits to any great depth; and air, if it fhould be thought ab- folutely necelTary to the fpontaneous firing of the pyrites, may be con- ceived either to accompany the wa- ter in its dripping, or to defcend into the innermoft parts of the earth through the fifTures which are found upon its furface. When a fubterra- neous fire is once kindled, it may be fupported for ages by other fub- Ilances, as well as by thofe which firfl gave rife to it : thus, if a quan- tity of the pyrites fhould take fire in a flratum of coal, or of fiale^ or of any other fubftance flrongly im- N 4 pregnated
( ^o^ ) pregnated with bitumen, the fire might continue till the ftratum was confumed*.
There are fuch a great number of volcanos now fubfifting in every quarter of the globe, and fo many unequivocal veftiges of others, which in length of time have be- come cxtin6l> that fome philofo- phers think they have reafon on their fide in fuppofing either, that the earth, at fome confiderable di- ilance below its furface, is furround- ed with a flratum of ignited matter
of
* There arc fome coaleries on fire now in Scotland, which were on fire in the time of Agricola. — Pennant's Tour in Scot. Part IL p. 20 1. See an account of the coaleries on fire in Staifordlhire, in Dr. PLott's Nat- Kill, of that County ; and of the fub^ances fublimed from the burning coal-pits at New- calHe in Phiiof. Tranf. for 1676.
( 201 )
of a definite thicknefs ; or that the whole central part of it is nothing but a mafs of melted mineralsj which every where ftruggling for vent, burfts forth where there is the leaft refiftance, Ihivering into rude fragments the fuperincumbent crufl of earth, and deluging with moun- tainous torrents of liquid fire the adjoining countries.
We do not knov/ of what kind of materials the inward part of the earth is compofed; the water, coal, earths, flones, metals met with upon its furface, have, bulk for bulk, very different weights 3 ^nd a fimi- lar inequality of fimilar materials may take place at all depths below the furface. It has been gathered, however, from very ingenious ob- fervations and calculations, upon the
at-
( 202 )
attraftion of the hill Schehalktn m Scotland, that the mean denfity of the whole earth is about four times and a half the denfity of water, the mean denfity of ftones, flip- pofe Portland ftone> being two times and a half the denfity of water*. Hence if this globe of earth could be weighed in a fcale, it would re- quire two equal globes and a half of Portland flone, or four equal globes and a half of water to balance it. The whole earth being fo m_uch heavier, bulk for bulk, than the general matter near its furface, it has been conjectured, that there mud be fomewhere within the earth, towards the more central parts, great quantities of metals, or fiich like denfe matter, to counterbalanoc
the * Philof. Tranf. 1778. p. 784.
( 203 )
the lightnefs of the fuperficial ma- terials, fo as to make up the whole weight of the earth. Suppofmg the diameter of the earth to be 7920 miles, and that it was compofed of an inward globe 51 10 miles in dia- meter, and of an outward fpherical Ihell 1405 miles in thicknefs, the matter of the inward globe being as heavy nearly as melted filver, and the matter of the outward cruft be- ing as heavy, at a medium, as Port- land ftonei then would the weight of fuch an inward globe, and fuch an outward fhell or cruft, be toge- ther equal to the prefent weight of the whole earth. But confidering the great comprefTibility of water, and of the ftones and earth met with upon the furface of the globe, it is probable, that in defcending to- wards
( 204 ) wards its centre, the parts may be fo condenfed as to make the weight of the earth what it is, without fup- pofing its central parts to be com- pofed of materials different from its fuperficial parts*.
But to return to our experiment. I need ufe no arguments to prove that either the fulphur, or the iron, or both, have undergone a great change during their fermentation : we can have no difficulty in think- ing that the fulphureous fleams, heat, flame, and fire, which attend- ed the mutual aftion of fulphur and iron upon each other, could not have been produced without the bodies themfelves having fuffered fome change : this change is vifible from
infped-
* See Mr. Michell's very ingenious ElTay on Earthquakes.
( 205 ) mfpefting the mixture before and after its fermentation; from a grey- ifli colour it will be turned wholly- black, or of a deep red; it will be rendered more manifeft by tailing it: neither fulphur nor iron have any tafte, nor has the mixture of the two any tafte before its fermenta- tion; but after that is finifhed, it has a very faline tafte. The nature of the fait contained in it will be ^examined in the next EiTay,
ESSAY
E S S A Y VL
t)F VITRIOLS, AND THE REPUTED
TRANSMUTATION OF IRON
INTO COPPER.
THE nature of the refidue re- fulting from the fermentation of iron filings and fulphur, may be •eafily afcertained. Its tafte indicates that it contains fome faline fub- ftancci in order to fee what that fubftance is, it muft he boiled in water; by this means all the fait contained in it, of whatever quality it may be, will be extracted. The water containing the fait in folu- tion being filtrat-ed, evaporated, and
ory-
( 208 )
cryflallized, according to the ufual mode, we lliall obtain large faline cryftals, of the colour of an eme- rald, and of the figure of a lozenge. This fait is called green virfriol -, green from its colour, and vitriol from its refembling vitruniy or glafs, by its tranfparency.
This fait certainly did not exift, either in the fulphur, or in the iron, it muft therefore arife from their mixture; but from a mere mixture of fulphur and iron, no fait can be extradted, unlefs the fubftances of which it confifls have been, by fome means or other, decompofed. The reader may probably recoiled, that ful- phur is compofed of two things, — of an acid, and of fhlogijlon. — Iron alfo is compofed of two things, — of
an
( 209 )
an earthy and o^ phlogijlon. During the fermentation of the mafs of ful- phur and iron, the phlogifton, or in- flammable part of them both, is djf- perfed; and, indeed, in being dif- perfed, it becomes the caufe of the heat, fire, and flame, obfervable in that mafs* The inflammable part, both of the fulphur and of iron, be- ing difperfed, there remains the add of the fulphur, and the earth of the iron. The acid of fulphur is a very ilrong acid, it diflblves many bodies with great facility, and when it is •diluted with water, it, in particular, diflblves iron; and, by its union with the earth of iron, it compofes the fait in quefl;ion.
That this is a true explanation of the origin of this fait, will appear evident from the following conflde-
VOL. !• O ration.
( aio )
ration. If into a quantity of the acid procured from the burning of ful- phur, you put a pi^ce of iron, the iron will be wholly diflblved in the acid, as fait is difiblved in water ; and if you faturate the acid with iron, and then evaporate and cryftal- fee the folution, you will obtain a green vitriol, fimilar, in every rc- fpe6t, to that obtained from the re* fidue of which we are fpeaking.
The compofition of green vitriol has been fully explained, and its de- compofition or analyfis v/ill ftill fur- ther illuftrate its nature, a^d leave no doubt of the truth of the propo-- fition which aiTerts, that — green vi^ triol confifls of the acid of /ulphur united to irony or more properly to the earth of iron.
If you put 1 6 ounces of frcih
green
i
C 2" )
green vitriol into a retort, and diftil them till nothing more can be forced into the receiver, by the utmofi: violence of a long continued fire, you will fiiid in the receiver about i I ounces of an acid liquor, fmelling, in all the trials that I have ever piade, very flronglyof fulphuri and [in the retort you will find about 5 [^ounces of an earth, of a deep red or lurplilh colour. The acid liquor, [iby combining it again with iron, lay be made into vitriol; and the larth, by being properly melted in conjundion with any matter which will reftore to it its inflammable prin- ciple, may be made into iron. The proportionable quantities of acid and earth procurable from green vitriol by diilillation, are purpofely exprelT- >td in terms rather indefinite, becaufe o 2 that
( 212 )
that proportion is fomewhat variable in different vitriols.
The earth remaining from the diftillation of vitriol is called Colco- thar, I would not have troubled the reader with fo barbarous a name, but for an obfervation relative to its ufe, which may be worth men- tioning.
Colcothar is fold for ten pence a pound in Paris \ it is ufed for giv- ing the laft polifh to plate-glafs, at the great manufa6tory in the ftreet St, Antoine, The largeft plate of glafs which had ever been polifh- €d in that manufactory, they in- formed me ten or twelve years ago, was ttn feet in length, and fix in breadth. The glafs is brought from Picardyi it is there melted in large crucibles, andfpread, whilft liquid,
upon
( 213 )
upon a , table covered with a flieet of copper J. much after the fame manner in which plumbers caft a fheet of lead. The plate of glafs, when firft caft, is an inch in thick- nefs ; its afperities are ground away, with a coarfe kind of grit-ftone, with fand, and emery, of different degrees of finenefs, and it is at laft polifhed by colcothar.
I do not know whether the ufe of colcothar is adopted in our Englifh plate-glafs manufadory nt2ivPrefcGt in Lancajhirey having not been fortu- nate enough to obtain permiiTion to fee it. But, both to the proprietors of that manufadlory, and to the pa- tentees for polilhing marble at JJh- ford in Derhy/hirey I take the liberty to fuggeft, that colcothar, which is very cheap, might perhaps render o 3 the
( 214 )
the ufe o(puttyy or calcined tin> lefs necefTary. — ^Would it not be polTible to apply the fanne kind of niachines by which marble is poliihed to the polilhing of plate-glafs I — But ta return from this digrefiion^
The acid feparated from vitriol^ by diflillation> is called the vitriolic acid. From what has been faid, rela- tive to the formation of vitriol^ it manifeilly appears to be the fame with that which enters into the com- pofition of fulphur; and indeed the main part of what is fold as vitriolic acid;, is now obtained by coUedling the vapour of burning fulphur, and not, as it ufed formerly to be, from the diftillation of vitriol.
It mud not be imagined, that the acid liquor procured from the diftil- lation of the i6 ounces of vitriol>.
confifts-
( 2IS )
confifls intirely of the vitriolic acid; it confifts of that acid diluted with a large portion of pure water. If care had been taken to feparatc the 'different produds as they arofe, during the dillillation, we might have procured, by a very gentle fire, fix or feven ounces of water wholly infipid : this is the water of cryftallization before fpokenof*^ it is called xht phlegm of vitrioL After the feparation of this water, by a ftronger degree of heat we Ihould have obtained an ounce or two of water {lightly impregnated with an acid: this is called, fpirit of vitrioL Laftly, with a very violent fire, we ihould have gotten a very ponderous and ftrong acid, having an un6tuous appearance, and from that appear- 04 ance
' ( 2l6 )
ance generally, but improperly, called, oil of vitriol. This oil of vi- triol is not always fluid 3 fometimes, when it is exceedingly flrong, it has been obferved to become folid : in. that ftate it is denominated, glacial or icy oil of vitriol.
It was ihewn in the laft Eflay, that natural combinations of iron and fulphur were fubjed to the fame fpontaneous changes obfervable in the artificial mixtures of thefe fub- fiances i and hence we may clearly apprehend the manner in which. what are called native vitriols are formed in mines and other fubterra- neous cavities. The pyrites exiiling in thefe places being naturally de- compofed by the fulphur's parting with its phlogiflon, the water which is always dripping in mines, dilTolves-
the
(217 )
the vitriol generated in the decom- pofed pyrites; and being afterwards evaporated, either by the heat, or the current of air fubfifling in the mine, the vitriol is found in its cryftalline form, either projecting like icicles from the top and fides of the mine, or lying in cavities at its bottom. The cryftals of native vitriol are more or lefs regular, according to the circumftances attending the evapo- ration of the water, and they are of different colours according to the quality of the pyrites; for together with the fulphur and iron, the chief conftituent parts of the pyrites, there is fometimes combined copper, and other metallic matters, which being dilfolved by the acid of the fulphur at the fame time that the iron is dif- folved, a mixed vitriol is produced,
the
( 2l8 ) the colour of v/hich is fometlmes whitifli, more generally it confifts of different Ihades of green and blue.
Native vitriol is often met with in our coal mines. From an old Cannel- coal pit near TV'tgan in Lancafhire, I procured a confiderable quantity^ of it very well cryftallizedj and Dr. Rutty has obferved, that the vitrio- lic water at Haigh in Lancashire is the ftrongeft in Britain, yielding 1920 grains of vitriol from a gallon of water *.
When I was at Whitehav^en^ fome years ago, I was informed by the very intelligent fuperintendent of the coal works in that place, that the bottom
of
*Philof. Tranf. 1756. p. 650. See alfo for an Examination of this Haigh watey, which fprings from a ftratum of the cannel- cx)al, Leigh's Tentamen Philo. de Fbnte Med. in Agro Lancaf. C. I.
( 219 )
of a pump of caft iron, which had ftood a long time in a well of vitriolic watery was fo much foftened, that, after removing a thin coat of ruft, he was able to cut it with a knife, as eafily as he could cut black leadj it had preferved its grain, and was not in any wife altered, except in being foftened.
At that time, I attributed this foftening of the iron to the a6lion of the vitriolic mater ^ and thought it a very fingular phenomenon: in this, however, I was miftaken ; fea v/^ater has the fame effed. Some iron can- non, which had lain in the fea up- wards of fixty years, were weighed up, and the iron was found to be as foft as tin ; though in 24 hours, by being expofed to the air, it recovered
its
( 220 )
its original hardnefs*. This foften- ing of iron is not an efFe6t peculiar to the adlion of either vitriolic or fea water : I have fomewhere read of an experiment of foftening iron by fmearing its furface with the acid of vitriol i and I have heard of a gen- tleman, who having frequently ftir- red faline draughts with his pen- knife, found its temperature much foftcned thereby. Didorus Siculus mentions a cuftom of the CeltiberianSy by which they made their arms of incomparable hardnefs; they buried plates of iron under the earth, till the weaker part of the iron was confumed by the ruft, and they fabricated their arms from the remainder J. The
inhabitants
* Hift. de PAcad. des Scien, a Paris, an, 1756. X Diod, Sic. L, V. p. 356.
( 221 )
inhabitants o£ Japan are fald to make ufe of the fame artifice -j-. — The time, however, in which the iron is fuffered to lie in the ground, muft not be too long; for the iron, inftead of being foftened and melio- rated, will in length of time be wholly changed, as is faid to have happened to fome Spaniih cannon made of hammered iron, which had lain many years under the old fort
at
f In itinerariis referunt aliqui de Japa- nenfibus quod ferrura fuum in contos exciifum Ipcis palaftribus incimergant, et ibi tamdiu relinquantj diini ad multam partem fer- rugine fit confumtum; exemtum dein e no\T) excudant, et iterum in paludi per fpatiuto 8 vel loannonim recondant, iifque diim iterum in aqua palu dinofa falia admo- dum exefum lit : pars ferri quae reftat fpeciem chalybis referre pf.rtiibetur, exinde dein vomeres fabricaiit, exque ferro {ic mbigi- nolb inftrumenta fua et uteniiiia conficiunt, Sweden de Ferro, Vol. I, p. 194,
( 0.22 )
at Hull in Torkjhire-, the iron being changed into a brittle kind of ilone refembling an iron ore, and refufing to obey the a6lion of the magnet"*.
Modern chemifts apply the name vitrioly to every combination of the acid of fulphur with any metallic fubftance ; three, however, of thefe combinations are more particularly diftinguifhed, being of great ufe in various manufa6tures. — green vitriol -"^hlue vitriol — white vitriol. The acid in all thefe vitriols is the fame: the metallic balls of the green vitriol we have already feen is iron, that of the blue vitriol is copper, and that of the white vitriol is zinc. Vitriol is very commouly called by the manu- fa6turers copperas: thus we con-
llantly * Lifter's Journey to Paris, p. 84. Ed. 1699.
( 223 ) ftantly ' hear of green, blue, and white copperas. The conflituent parts of the different kinds of vi- triols were not underftood by the an- cients fo well as they are at prefent; they feem to have had an idea, that ropper was the bails of them all: hence the Greek term for vitriol, chalcanthoSy the efflorefcence of cop- per j and the Latin one, cuperofa^ or ^upri rofa^ the flower or efHorefcencc of copper J from which the French xouperojey and our copper as ^ are evi- dently derived.
The vitriols which nature pre- pares, are never to be met with in commerce ; they ferve to adorn the cabinets of the curious, but they are neither fufiiciently pure for the pur- pofes to which com.mcn vitriols are applied, nor arc they found in fufH-
cient
( 224 )
cicnt quantities to anfwer the de- mand which is made for them. Green vitriol is made at Beptfordy and other places, from a fpecies of the pyrites found on Shepey Ifle, the Ifle of Wighty and various parts of the EJfeXy Kentljhy SuJfeXy and Bor- Jetjhire coafts. Large quantities of the pyrites are laid in heaps in the open air, on beds properly pre- pared; in half a year, a year, two years, fooner or later, according to/ its quality, the pyrites acquires a fpontaneous heat; that heat, without being increafedtofuch a degree as to ■fire the pyrites, infenfibly difperles the inflammable principle of the ful- phur, one of the conilituent parts of the pyrites 3 the acid of the fulphur being thus difengaged from the in- flammable principle, unites itfelf to the other principal conftituent part
of
^
( 225 )
of the pyrites, the iron, and forms green vitriol. The vitriol thus formed is wajQied from the pyrites' bed by the rain : the rain-water which has difiblved the vitriol of the pyrites., cannot fink into the earth, the bed on which, the pyrites is fpread being formed of clay; and being made, moreover, in a Hoping pofrtion, the dilTolved vitriol runs into receptacles properly placed to receive it, and being boiled with old iron till it is of a proper con- fiftency, it is run off Into coolers, and left to cryftallize. Vitriol may be made without the ufe of old iron, but the liquor which drains from the pyrites being often not faturated wdth iron, the iron is added to fatu- rate the acid, and at the fame time o purify it from any particles of VOL. I. P copper
( aa6 ) topper it may chance to contain; by this naeans a pure iron vitriol is obtained, which is known in com- merce under the name of Englifh vitriol. The quantity of old iron, in fome works, amounts to two hundred weight in making a ton of vitrioL
Much after the fame manner, vi- triol is made from the pyrites found amongft coalj there are manufa6lu- ries of it near Wigan^ at Whitehaven^ at Newcajlle u^on Tyne^ and in feve- ral other parts of the kingdom. But all the vitriol works have funk in value of late years ^ the home confumption of vitriol being much diminiihed fince the acid, which iifed to be procured from the di- ftillation of vitriol, has been ob- tained from the burning of ful- phur.
It
It is not eafy to determine whei\ this method of making vitriol was introduced into England. In the very beginning of Q^ieen Eliza- beth's reign, a patent was granted to Cornelius DevoZj for making alum and copperas* 3 but it was not till towards the end of the laft century, that this art of making vitriol was brought to fo great per- fedtion as to enable us to export any of it f i and> indeed if, a very deep and judicious inquirer into things of this kind afTures us, that " at the latter end of the laft century, we im- ported annually about 500 tons of vitriol, and that we now export up- wards of 2000 tons." It appears, that there was exported, from the p 2 port
* Oper. Min. explicat. p. 26.
f Boyle's Works. " % Campb. Sun-ey of Brit. Vol. II. p. 21.
( 228 )
port of London alone, near 400 tons of copperas in three months, Janu- ary, February, and March, 1776** A fmall quantity of vitriol, perhaps to the annual amount of 50 or 60 tons, is ftili imported into England] fome particular dyers and other artifl$ being of opinion, that the foreign vitriol, as containing a little copper, is more ufeful to them than the Englifh vitrioL
It may eafily be known whether green vitriol contains any copper ; we need only rub the vitriol to be examined upon a moiftened piece of polifhed iron, for if there is any cop- per in its compofition, the iron will be changed into a copper colour* This experiment renders it necefTary
to
* See Sir Charles Whitworth's Reg. of Trade, No. I.
( 2^9 ) to explain to the reader two terms
frequently met with in chemical books — affinity and precipitatkn.
When two heterogeneous bodies, as an acid and iron, coalefce toge- ther, and conilitute by their union a third body different from either of them^ their union is faid to proceed from their mutual attractions or, in. the language of German philofo- phy, from their mutual affinity. It may reafonably be conjedtured, that the affinity of the fame body, of the fame acid for inftance, may be dif- ferent with different bodies; its ac- tion upon iron may be different from, its a6cion upon copper j and its ac- tion upon any metallic fubftance may be different from its aftioa upon any alkaline or earthy fub- ftance 3 becaufe, from whatever at- p 3 tradive
( 2J0 }
tf adive powers we fuppofe its aftloir- upon any body to proceed, it feems probable enough, that their efFeds v/ill be modified, according to the- nature of the fubje6l upon which they are exerted. A few inftances will make this matter clear.
Spirits of wine very readily dif- folve a portion of camphor; that is,, the particles of the fpirits of wine fo powerfully attraSi the particles of camphor, that they unite them- felves v/ith the camphor in fuch a- way as to compofe with it a pellu- cid fluid. Spirits of wine,, however, more powerfully attrad water than they atrrad cam^phor^ for if you mix water with camphorated fpirits of wine, you will fee that the fpirits quirting their connexion with the camphor, will unite themfelves with
the
( 2J1 )
the water, and the camphor being lighter than water, will rife up to the furface. I^avender water cod- fills of the oil of lavender difTolved in fpirits of wine. Into a glafs pf water, drop a few drops of lavender water ; the fpirits of wine will quit the oil, in order to unite themfelves v/ith the water, and the oil being lighter than v/ater will float upon its furface. In both thefe cafes, the fpirits of wine are laid to have a greater affinity with water, than with camphor or oil of lavender.
Into a folution of green vitriol, drop a folution of pot-afh, fait of tartar, or any alkaline fait; the vi- triolic folution will let fall a fedi- ment : continue to mix the alkali with the folution of vitriol, till no more matter falls to the bottom ; the p 4 matter
C ^32 )
matter which fails to the bottom, is. faid to be precipitated^ and it is often called 2l precipitate. This effed may be thus explained v. — green vitriol confifts of two thingSj — of an acid,, and of an iron earth ; but the acid lias a greater difpofition to unite it- felf with any alkali, than it has to- continue united with the earth of iron ; when therefore an alkali is prefented to it, it quits the iron earth, which, thus wanting its fup- port, falls to the bottom, and unites itfelf with the alkali. The acid of vitriol is therefore, on this account, faid to have a greater aftinity wkh any alkaline fait, than with iron, becaufe any alkaline fait will feparate the iron from the acid. What is precipi- tated may be made into iron i and if the liquid which floats upon the pre- cipitated
( '^33 ) cipitated earth, be evaporated and
cryftallized, it will give the very- kind of fait which would arife from a dire6t combination of the acid of vitriol with the alkali which occa- fioned the precipitation. I will mention one other inftance.
Blue vitriol confifts of copper united with the acid of vitriol : if to a folution of blue vitriol you add a piece of bright iron, it will prefent- ly become covered with a coppery coat, the copper will all be presipi- tatedy and the iron will be dijfolved in its ftead. The proof of this rea- foning is eafy : the maatter which is precipitated may be melted into copper, and the liquid part may, by evaporation and cryftallization, be made, not into hlue^ but into green vitriol -J that is, into a combination of
the
( 234 ) the vitriolic acid and iron. Hence it is faidj that the acid of vitriol has a greater affinity with iron, than it has with copper, becaufe it quits cop- per to unite itfelf with iron. In order to be convinced of the truth of what is advanced, we need only dip a bright key into a folution of blue vitriol, and we ihall fee the key pre- fently becoming covered with a copper- coloured pellicle.
This experiment explains to us, in a very fatisfadiory manner, the nature of that tr an/mutation of iron into coppery which travellers have been fo much furprifed at. Agricola fpcaks of waters in the neighbour- hood of Newfol in Hungary which had the property of tranfmuting the iron which was put into them into copper*. In the year 1673, our
coun- * Agric. Fof. L. IX. p. 347.
( ^3S ) countryman Dr. Brown vifited a fa*
mous copper mine at Herrn-Grundty about feven Engli^ miles from^ NewJol\ he informs us that he there faw two fprings, called the old and new ximenty which turned iron inta copper. The workmen ihewed him a curious cup made of this tranf- muted ironi it was gilt with gold, had a rich piece of filver ore fallen- ed in the middle, and the following infcription engraved on the out-fide :
Eifen ware ich, kupjer bin icb. Silver trag ichy gold hedeckt mich.
Copper I am, but iron was of old. Silver I carry, covered am with gold*.
It was even at that time, he fays, contended by fome, that there was no- real tranfmutation of iron into
copper^
* Brown's Travels, Ed. 2687; p. 69^
C n^ )
copper, but that the ziment water^ containing vitriol of copper, and meeting with the iron, depofited its copper ; and it feerns as if he would have acceded to this opinion, could he have told what became of the iron. It is now very well underftood what becomes of the iron -, it is taken up by the water, and remains fufpended in it, in the place of the copper y fo that this tranfmutation is nothing but a change of place ; and as the copper is precipitated by the iron,, fo the iron might be precipitated by pot-aih, or any other fubftance which. has a greater affinity with die acid of vitriol than iron has.
The caufe of the im.pregnation of thefe copper waters in Germany is not difficult to be explained. Moft copper ores contain fulphur, and
when
( 237 ) ^vhen the fulphur is in any degree de- compofed, its acid unites itfelf to the copper, and forms blue vitriol, which is the fubftance with which the wa- ters iffuing from the copper-mines are impregnated. It has been the cuftom in Germany, for fome centu- ries, to collecl the copper contain- ed in thefe waters ; the method is fimple : into pits filled with the cop- pery water they put old iron ; the iron is diiTolved, and the copper is pre- cipitated, and being raked out in ■the form of mud, it is afterwards melted into very fine copper. The quantity of copper procured by an hundred tons of iron, is not always the fame; 'it fometim.es amounts to ^o tons, and feldom to lefs than 84*.
The
* Mifcel. Curi, Germ. Ann. 6 & 7, p. 158,
where
( 238 )
The progrefs of arts is in many 3nftances wonderfully flow. Though this method of obtaining copper has 'been long pra6tifed in Germany, yet it is but of late years that any fuc- cefsful attempts of this kind have been made in either England f or Ireland; and that they have been made at all has, in Ireland at leaft, been owing not to the example which had been fet in Germany, but to an accident.
There are very celebrated cop- per-mines at Arklow in the county of Wicklow in Ireland; and from thefe
mines
where there is mention made of an oak leaf being changed into copper — the iron con- tained in the leaf, probably precipitating the copper.
f An attempt was made in 157 1, to tranf- mute iron into copper, near Pool in Dorfet- iliire. Hutch. HiH. of Dorf. Vol, II. p. no.
( n9 )
mines there iflues a great quantity of water, ftrongly impregnated with the vitriol of copper. One of the workmen having accidentally left an iron fhovel in this water, he found it, fome weeks after, fo incrufted with a coat of copper, that it was thought to be changed into copper. The proprietors of the mines, in purfuance of this hint, made proper pits and receptacles for the water, and have obtained, by means of foft iron bars put into the coppery water, fuch quantities of copper, as render the ftreams of as much confequencc as the mines. OM ton of iron pro- duces near two tons of copper mud; and each ton of mud produces, whea jneited, i6 huhdred weight of cop^ j)er, which fells for lo pounds a ton,
more
( 240 )
■niDre than the copper which is fluxed from the ore*.
There is a mountain in the ifle of Anglejey^ called Faris moun^ tain, which abounds in copper ore ; the bed of ore being above forty- feet in thicknefs. The lelTees of this mine annually raife between fix and feven thoufand tons of mer- chantable ore, and daily employ above forty furnaces in fmelting it. The ore is not rich in copper, but it contains a great quantity of fulphur, which mult be feparated from it, before it can be fluxed
into
"^ Philof. Tranf. for 1751 and 1752, p. 502, and for 1756. — Iron often contains gold; the vitriolic acid has no aftion upon gold ; is not the gold contained in the iron mixed with the precipitated copper, and may it not be worth while on this account to aflay this copper ?
( 241 ) into copper. The ore is accord- ingly roafted^ the phlogifton, to- gether with part of the acid of the fulphur, is, by the violence of the fire to which it is expofed in roafl- ing, difperfed into the air: another part of the acid attacks and diflblves the copper. The water in which the roafted ore is walhed is fo ftrong- ]y impregnated with copper, that they have found it ufeful to adopt the German method of precipita- ting it by means of old iron, and they have obtained in one year near one hundred tons of copper preci- pitated from this water*
The water, after the copper has been precipitated by means of iron, is at prefent thrown awayj it would, by evaporation, yield green vitriol i and as above one hundred tons of
VOL. I, Q^ iron
( ^4^ )
iron muft be employed in obtaining
the forementioned quantity of cop- per, it may deferve to be confidered, whether a manufaEiory of green vi- triol might not be eftablifhed at this and at all other places where copper is obtained hj precipitation. One hundred tons of iron would yield, at the leaft, two hundred tons of vitriol; which, at the low price of three pounds per ton, would be more than fufficient, I fuppofe, to pay the expence of extrading it; efpecially, as means might be con- trived of evaporating the watery fo- lution, by a proper application of part of that heat, which is at pre- fent loll in all the great fmelting- houfes. There are other purpofes to which this v/ater might be ufefully applied, which I cannot infifi: upon in this place. The
C H3 )
The principal ufe of green vitriol iS, in dying, and in making of ink* When the vitriol is diffolved in wa- ter, the iron contained in it becomes black by the addition of an infufiofi of gall-nuts. Galls are excrefcences from the oak ; they are formed from the exudation of the juices of the oak : this exudation is not fponta- neous ; it proceeds from the punc- ture made in the bark by an infe6t : in the hole which it has made, it de- f ofits its egg, and the exuding juice hardening, forms a proper nidus for it. Moft of the galls have holes in them, the young infe6t having eaten its way through the fubftance in which it was hatched^, in many of thofe which have no holes, the in- fe6l may be difcovered in the infide, by breaking the gall. The property Q^z which
( 244 )
which an infufion of galls has, of tinging a folution of vitriol black or purplifh, renders it ferviceable in difcovering the minuted portion of iron in chalybeate waters. I took one grain of vitriol (a grain of vi- triol does not contain quite half a grain of iron) and diflblved it in 15 gallons of water i the water, upon the addition of an infufion of galls, became fenfibly purple. Other afirin^ gent vegetables have a fimilar effedt on vitriol, but not in the fame degree.
I will conclude this fubjed with mentioning an experiment, which, when profecuted by a Ikilful manu- fadturer, may, I fhould hope, fome time or other, become of general fervice.
I took a piece of dry oak, which iiad been felled about a year 3 I
xafped
( ^5 ) rafped off from the bark^ from the lap, and from the heart of the wood, equal weights, and put them into equal portions of hot water. After they had Hood fome tirne, it was apparent that the bark had given an higher colour to the water than the. heart had donej and that the v/ater in which the fap was put, had extra6ted the leaft colour. Into equal portions of a folution of green vitriol, I put, equal parts of thefe feveral infufions, expe6ling to have feen the vitriol turned black by them all; but the event was, that tht fap infufion produced very little change of colour -, the l^^^rk infufion gave a dark brown; and the heari infufion inftantly gave one of the moft vivid blues I ever faw. If the rafpings of heart of oak be boiled
0.3 f^^
( 246 )
for an hour in water,, they lofe this- property of forming blue with vi- triol ; but the cold infufion forms a fine blue 5 and if a folution of vitriol be poured upon the rafp- ings, the whole is changed into ^ blue mafe.
ESSAY
ESSAY VIL