CHEMISTRY. 



CHEMISTRY. 



properties of alumina, demonstrated tho nature of soda, anil gave an 

 eaT process for preparing pure ailrer from it- Mia chemical 



paper*, down to the year 1762, were published at Paris, 1782, in two 

 mull volume* ; but they do not contain all hU memotn. 



In 1880 John Kunckel wat born in the duchy of Schleswig ; he died 

 In 1703. In 1678 he published a treatise on phosphorus, which h.t<l 

 been originally discovered in 1649 by Brandt, an alchemist of Ham- 

 burg ; all that Kunckel knew of it* properties was that it was pro- 

 cured from urine, ftc., and from this, after some years' application, he 

 succeeded in obtaining it The remainder of his works, excepting a 

 treatise en glass miking, are not of great importance. 



Nicholas Lemery was born at Rouen in 1645, ami died in 171.'. Ho 

 was not the author of any very prominent discovery ; but his ' System 

 of Chemistry' contained nearly all that was known respecting the 

 science, and the language in which it was written was more simple 

 than that of those who preceded him. He attempted to explain the 

 cause of earthquakes by an experiment which showed the vivid action 

 that occurs when large quantities of iron filings and sulphur are mixed 

 and allowed to act upon each other. 



Homberg was born in 1652, in the island of Java. His papers on 

 chemical subjecU were numerous ; there are, however, Imt few of 

 them which are likely to excite much attention in the present state 

 of the science, nor did they greatly contribute to enlarge it* boun- 

 daries. The pyrophorus known by his name was prepared by mixing 

 human fasces and alum, and heating the mixture to redness till it 

 became a carbonaceous powder. It has been since found that carbo- 

 naceous matter in preferable forms may be used with the alum, as 

 honey, flour, or gum. The nature of the combustion of this pyro- 

 pliorus was first explained by Davy. 



Henry Louis Duhamel was b rn at Paris in 1700, and died in 1781. 

 He published many papers on chemical subjects. His chief contri- 

 bution to the science was that of pointing out the difference between 

 potash and soda, which had been formerly confounded. 



Peter Joseph Macquer was born at Paris in 1718, and died in 178-1. 

 He first pointed out the existence of arsenic acid, and the nature of 

 several of the salts which it forma with bases ; he afterwards pub- 

 lished some important experiments on Prussian blue, and such as 

 tended to the discovery of the nature of its colouring ingredient. He 

 made some experiments on platinum, though without any very 

 beneficial results to chemistry. He was the author of a Chemical 

 Dictionary, which has been translated into many languages. 



We have mentioned most of the chemists who contributed valuable 

 additions to the science before the introduction of pneumatic chemis- 

 try. To speak of them all would require a volume. We now, there- 

 fore, approach, or rather commence, a most important era in the 

 history of chemical research and discovery. Hitherto, except what 

 had been done by Key, Mayow and Boyle, the effects produced by 

 aeriform bodies, and then* relation to the phenomena of chemistry, hod 

 almost entirely escaped observation ; or at any rate they had been but 

 very slightly and imperfectly considered, as shown with respect to the 

 increase of weight which occurs during the calcination of metals, and 

 which was rather attributed to a principle of levity iu the phlogiston 

 lost by them, than the acquisition of weight from tho air. 



Dr. Hales was born 1877, and <li,-d in 1781. About 1724 he recom- 

 menced the examination of ac'rii ! previously 

 engaged the above-named philosophers ; he attempted to ascertain the 

 chemical relations subsisting between air and other bodies, and to 

 determine the circumstances und. r which air it abaorbed or extricated 

 by natural proesscs. The results which he obtained were curious and 

 important ; but, owing to a fundamental error in his ideas, he drew 

 but few inferences which contributed to elucidate the intricate and 

 hitherto imperfectly explored paths of the science. The idea which he 

 entertained of one elementary principle as constituting elastic matter 

 modified by the effluvia of fluid or solid bodies, greatly aided the 

 :on of those more just views which later and more refined expe- 

 riment* hare since contributed to unfold. He subjected a vast number 

 > f bodies to the action of heat, and obtained gaseous products from 

 them ; thus he found that the air which he obtained from wood was 

 fatal to animal* ; from nitre he procured nearly 200 times its volume 

 of air, and from coal one-third of its weight. He found that oil of 

 ritrol when poured on tho iron filings, produced very little air, but that 

 the addition of water occasioned iu evolution in large quantity. In no 

 caee, however, were the gaseous products thus procured examined with 

 the attention which might hare been expected from the novelty of the 

 naulU. He al*> found that when phosphorus was burnt in air, tho 

 qiiantitT of air was diminish.. I, and white fumes were pi" lui .1 ; but. 

 he neither examined the p-idn.il air, nor did he inquire i 

 nature of the white fumes resulting from the combustion of tho 

 phosphorus. 



The experiment* contained in his Statical Essays, published in 1727, 

 Were made to prove the transpiration of trees, and also the force with 

 which thr'j- inil-ilie momture. Thew experiments are not, however, 

 li.il'ly connected with our present subject. 



In 171 8 Oeoffroy published tables of affinity; and although the affinity 

 ha* since been discovered to be modified by a variety of circumstances 

 yet theee table, have certainly been of use. 



Dr. Black, Professor of Chemistry in Edinburgh, published, in 1756, 

 bis reteafcbei on calcareous, magnesian, and alkaline substances. He 



showed that there existed in theee substances an aeriform body, pos- 

 sessing chemical and physical properties, perfectly distinct from the 

 ah- of the atmosphere ; he proved that marble and chalk contained this 

 body capable of an aeriform existence, and that its presence consti- 

 tuted the difference between them and quicklime ; ho showed also that 

 it was capable of being expelled from earthy and alkaline substance* 

 by the action of an acid, and when the air thus set free was col- 

 lected and examined, he found it to possess the properties of a weak 

 add, 



Great opposition was offered to the new and important conclusions 

 which were promulgated by Dr. Black : thus, among others, Meyer, a 

 German chemist, attempted to prove that limestone became caustic 4 by 

 combining in the fire with a peculiar substance, and not, as Dr. Black 

 had proved, by losing aeriform matter. The loss of weight which the 

 limestone suffered was, however, almost a sufficient proof of th 

 racy of Dr. Black's views; and, in a few years from the date of their 

 promulgation, the opinions of Black were universally admitted to be 

 correct. 



The existence of an elastic fluid different from that of the atmos- 

 phere greatly excited the attention of experimcntalisto, and they were 

 soon led to inquire whether others might not also exist. The various 

 gases obtained by Hales were now regarded with different view- : 

 before many more years had elapsed, numerous and peculiar aeriform 

 bodies were discovered by various processes. Dr. Black's exi>criincnts 

 on what he termed latent heat are remarkable for their (implicit;- 

 the precision of the inferences drawn from them. 



Watt derived great advantage from these experiments in his cele- 

 brated improvement* on the steam-engine. 



About the year 1765, Mr. Cavendish (who was bora in 17:li 

 died in 1810,) discovered and described the properties of inflammable 

 air, since called hydrogen gas; and ho invented an apparot 

 collecting and examining elastic fluids, which, although extremely 

 simple, lias been completely set aside by the more convenient u 

 proposed by Dr. Priestley. He a.-<-ei t.iined the relative densities of 

 fixed air, inflammable air, and common air. 



Having stated the general properties of hydrogen gas, ho shows that 

 different metals, when dissolved in similar portions of the same acid, 

 afford different quantities of this gas : that zinc yielded more than 

 : 1 iron more than tin facts which are perfectly consistent with 

 ind explained by the doctrine of equivalents; he ascertained the exact 

 proportions of the constituent gases of the atmosphere. His most 

 celebrated discoveries were, however, those of the composition of 

 water and nitric acid ; and he first determined the freezing point of 

 mercury. 



His character, as a philosopher, is thus sketched by Sir II. Davy: 

 "Cavendish was possessed of a minute knowledge of most of the 

 department* of natural philosophy : he carried into his ch< 

 researches a delicacy and precision which have never been exceeded : 

 possessing depth and extent of mathematical knowledge, he reasoned 

 with the caution of a geometer upon the results of his experiment* ; 

 and it may bo said of him, what perhaps can scarcely be said ol 

 other person, that whatever he accomplished was perfect at tin- M 

 of its production. His processes were all of a finished n 

 executed by the hand of a master, they required n <D ; the 



accuracy and beauty of his early labours, even, have remained unim- 

 paired amidst the progress of discovery, and their merits have been 

 illustrated by discussion, and exalted by ' 



The important discoveries of Dr. Joseph Priestley next claim atten- 

 tion. He was born in 1733, and died in 1804. No person ever com- 

 menced a career of discovery under circumstance* less likely to ensure 

 success than Dr. Priestley. He was but imperfectly acquainted wit li 

 chemical science, ho had but little leisure, his api -ar.it u* was very 

 deficient, he hod frequently to invent new modes of operating, and 

 with means which were extremely scanty. All these difficulties ho 

 surmounted with indefatigable industry and ingenuity, and to him we 

 owe some of the most important discoveries which have ever been 

 made. 



Pneumatic chemistry had, t<- ri certain extent, be. n ,-tudied, as 

 already shown, by Boyle, Mayow, Hales, and especially by Black and 

 Cavendish, when Dr. Priestley began his experiments. His first 

 memoir \-..i- published in 1772, and was on the method of impreg- 

 nating water with carbonic acid gas. This paper was the result of his 



.'ally living near a brewhouse, in which If l"d m.id.- . 

 menU on the carbonic acid evolved during fermentation. Among the 

 gaseous products which Dr. Hales obtained was that now called 

 oxide, but he did not inquire inl ities. It was ag,- 



covered and minutely examined by l>r. I'ricstley, who applied it to the 

 purposes of cudiometry, a branch of the science which may almost 

 be said to have originated with him, and in consequence of this 

 discovery. 



Nitrogen gas hod undoubtedly been obtained, but was not examined 

 by Hauksbee, when he passed atmospheric air over ignited metals ; 

 Dr. Rutherford also noticed it about 17"-. and to him the prim 

 the discovery is generally assigned. It appears, however, that Dr. 

 Priestley had obtained it, and noticed its pro-- i.-t as early, 



and perhaps sooner, for he gives an account of it in the ' Philosophical 

 Transactions' for that year. 



His greatest discovery wai that of what he called dephlogisticated 



