112 HISTORY OF CHEMISTRY. [LECTURE VII. 



plant or animal organism, but from these there were prepared 

 a large number of other compounds, whose position in the 

 system had also to be determined ; and a decision as to which 

 class they were to be enumerated in was often an arbitrary 

 matter. Simplicity of composition was frequently a reason for 

 placing substances in the inorganic class. With regard to 

 many substances, the views as to their nature had changed in 

 course of time ; for example, in the case of the cyanogen 

 compounds, which were first classed as organic and afterwards 

 as inorganic substances. Wherever it was possible, Lavoisier's 

 idea was upheld that, in organic substances, the basis com- 

 bined with oxygen, or the radical, consists of several elements. 

 This gave rise, at a later date, to Liebig's definition of organic 

 chemistry as the chemistry of the compound radicals. 



The study of the compounds belonging to this class lagged 

 considerably behind that of the others. The reason lay partly 

 in the easy alterability of these substances, and, thus, in the 

 greater difficulty which their isolation presented ; partly also in 

 the scarcity of methods for th^ir analysis. At the beginning 

 of this century, when qualitative analysis had already attained 

 a high degree of accuracy, and even the quantitative method 

 had found excellent exponents in Proust, Klaproth, and 

 Vauquelin, Lavoisier's experiments with alcohol, oil, and wax, 

 were the only ones in existence, designed to ascertain the 

 composition of organic compounds ; and these, as may easily 

 be understood, were not very accurate. 



It is thus explicable that Berzelius should still doubt, in 

 1819, whether the law of multiple proportions held in organic 

 chemistry also. 5 He was well aware that when organic com- 

 pounds unite with inorganic ones organic acids with metallic 

 oxides, for example -the same regularities are observed as in 

 inorganic chemistry ; but he believed the proportions in which 

 carbon, hydrogen, oxygen, and nitrogen unite, to be so varied 

 that Dalton's law lost its significance, simply because i, 2, . . n 

 atoms of one element could unite with i, 2, . . m atoms of 



5 Essai etc., 96; compare also Lehrbuch. 3, part I, 151. 



