CHEMISTRY 



147 



knowledge, and a number of very eminent chemist* 

 preceded and were contemporaries of Lavoisier. 



In Germany, Murggraf (1709-82) stuli-<l the 

 properties of the almost unknown alumina and 

 magnesia, and made considerable advances in the 

 Qualitative analysis uf snl>stances in solution. 



Amongst British chemists of note may IHJ nien- 

 liiUH'd Hales (1077-1761), who was amongst the 

 (list to experiment on gases ; Black ( 1728-99), who 

 in 1756 published his research on Magnesia Alba, 

 showing the nature of fixed air or carlxmic acid 

 gas, and of the difference between caustic and mild 

 (or rarlionat.'d) alkalies; Priestley (1733-1804), 

 who, in addition to his discovery of oxygen in 1774, 

 investigated nitric oxide, nitrous oxide, sulphurous 

 acid, carbonic oxide, hydrochloric acid, and 

 ammonia gases, being specially attracted to the 

 stiiily of gaseous substances and their properties; 

 ami Cavendish (1731-1810), who investigated the 

 nature and properties of hydrogen, analysed atmo- 

 spheric air, and discovered the compound nature 

 and composition of water and of nitric acid. 



Lavoisier ( 1 743-94 ) was one of the ablest chemists 

 of his time, and his labours include a vast variety 

 of subjects. His attack upon, and eventual demoli- 

 tion of the phlogiston theory, and his experiments 

 in connection with his new theory of combustion, 

 occupied him for a considerable number of years. 

 He taught that combustion was the union of the 

 combustible substance with atmospheric oxygen ; 

 he was the first to introduce system into chemistry 

 and chemical research ; he determined the con- 

 stituents of a large number of substances, including 

 sulphuric, phosphoric, and carbonic acids, numerous 

 metallic oxides, and many animal and vegetable 

 substances ; and he, along with Berthollet, Four- 

 croy, and Morveau (1737-1816), introduced a new 

 and consistent system of chemical nomenclature. 

 Two contemporary Swedish chemists, Bergman 

 (1735-84) and Scheele (1742-86), must be men- 

 tioned before leaving the phlogiston age. Berg- 

 man investigated, amongst other things, carbonic 

 acid gas, studied the phenomena of affinity, and 

 made advances in the processes and reagents used 

 in qualitative analysis. Scheele was one of the 

 most laborious chemists of his time. He discovered 

 citric, malic, tartaric, oxalic, lactic, hydrocyanic, 

 arsenic and other acids, and chlorine, besides in- 

 vestigating the nature of a large number of other 

 bodies andindependently discovering oxygen. 



It was towards the end of the 18th century that 

 the value of quantitative analysis of substances 

 began to be generally recognised. The question as 

 to whether the quantitative composition of a given 

 substance was always the same gave rise to a dis- 

 cussion which lasted for several years, and was at 

 length decided in favour of constant composition. 



The researches of Richter (1762-1807) on the 

 quantities of various acids neutralised by a given 

 quantity of a base, and of various bases neutralised 

 by a given quantity of an acid, led him to the 

 general conclusion that the quantities of two acids, 

 a and a', which form neutral salts, a b, and a' b', 

 with the quantities of two bases, b and b', are just 

 the quantities required to form two other neutral 

 salts, a b' and a b. This fundamental discovery 

 was erroneously attributed to Wenzel by Berzelius 

 -in 1819, and the error has been carefully per- 

 petuated in a considerable number of text-books 

 since that time ( Kopp, Entwickelung der Chemie 

 in der neueren Zeit, p. 251). 



Berthollet ( 1748-1822), who was one of the most 

 active opponents of the theory of the constant com- 

 position of chemical substances, contributed valu- 

 able researches into the laws of chemical affinity, 

 and applied chlorine to processes of bleaching. The 

 processes of chemical analysis were improved, and 

 large numbers of analyses, especially of minerals, 



were carried out 1>V Klaprotli ( 1743-1817), Vauque- 

 lin ( 1763-1829), Fourcroy ( 1755-1809), and others ; 

 and in.-iiiy quantitative 'olmervations of all kinds 

 were made al>out the end of the 18th century, all 

 preparing the way for Dal ton's statement of the 

 Atomic Theory (q.v.) in 1803-4. 



The progress of chemistry during the present 

 century has been immense, and it in not possible to 

 do much more than mention the names of some of 

 the most prominent workers. A stimulus was given 

 to research by the publication of Dalton's atomic 

 theory ; and the labours of Gay-Lussac ( 1778-1850), 

 who experimented with gases, of Dulong (1785- 

 1838), and Petit ( 1791-1820), who pointed out the 

 relation between specific heats and atomic weights 

 of elements, and of others, supported and amplified 

 Dalton's views. 



Wollaston (1767-1829) discovered palladium in 

 1803, and rhodium in 1804. The first alkaloid 

 (morphine) was obtained pure by Sertiirner in 1816, 

 and this led to the discovery of a number of others 

 in a short time. 



The decomposition by electricity of the bases 

 potash and soda by Davy (1778-1829) in 1807, and 

 the separation from these of the metals potassium 

 and sodium, threw an entirely new light on the 

 nature of these substances. The metals were more 

 fully investigated by Gay-Lussac and Thenard 

 ( 1777-1857 ). Davy is noted also as the inventor of 

 the miners' safety-lamp, and for experiments on the 

 respiration of nitrous oxide and other gases. 



Amongst the foremost chemists of the earlier part 

 of the 19th century was the Swede Berzelius ( 1779- 

 1848), whose careful and exact analyses of mineral 

 substances contributed a good deal to the confirma- 

 tion of the law of constant proportions and to the 

 fixing of the atomic weights (see ATOMIC THEORY) 

 of the elements. Berzelius was very conservative 

 with regard to new theories, which he declined to 

 accept without putting them to the strictest experi- 

 mental tests. He formulated the electro-chemical 

 theory of the constitution of salts, introduced great 

 improvements into the methods of quantitative 

 analysis, increased the value of the blowpipe as an 

 aid in mineral analysis, discovered many new sub- 

 stances, and further examined and elucidated points 

 concerning* many already known, both inorganic 

 and organic. 



The artificial production of urea in 1828 by 

 Wb'hler (1800-82) marks the beginning of a new 

 era in the branch of organic chemistry, and enor- 

 mous strides have been made in this department 

 since that time by Dumas ( 1800 84), Liebig ( 1803- 

 73), Laurent (1807-53), Gerhardt (1816-56), Wurtz 

 (1817-84), Kolbe (1818-84), Baeyer, Cannizzaro, 

 Frankland, Hofmann, Kekule, Williamson, and 

 many others. Advances in general inorganic 

 chemistry and analysis have been made by Leopold 

 Gmelin (1788-1853), H. Rose (1795-1864), Sainte- 

 Claire Deville (1818-81), and Bunsen ; whilst in 

 connection with advances in chemical physics may 

 be mentioned Faraday (1791-1867), Mitecherlich 

 ( 1794-1863), Graham ( 1805-69 ),Regnault( 1810-78), 

 Andrews (1813-85), and Berthelot. These lists do 

 not include all of even the most prominent names 

 that might be mentioned in connection with each 

 department. 



The most striking feature of modern chemistry is 

 the extraordinary development of organic chemistry, 

 the account of one branch of it tiie chemistry of 

 the coal-tar products constituting of itself quite a 

 literature which receives additions every dav. 



Amongst the most recent triumphs of chemical 

 research may be mentioned the artificial production 

 of indigo and grape-sugar, and the isolation, in 

 sufficient quantities to study its properties, of the 

 hitherto all but unknown element fluorine. 



Of the greatest possible interest from a theoretical 



