A HUNDRED YEARS OF CHEMISTRY. 677 



other. These ideas were more than speculation, for they rested 

 upon experiment and led to further experimental research; but they 

 went too far, and therefore could not last. The theory, however, 

 contained much that was true, and the formulae developed by it 

 gave the first general suggestion of what is now known as chemical 

 structure or constitution. The later study of organic compounds 

 led up to the modern views. 



Although Berzelius and many other chemists did some work 

 upon organic compounds, their era was chiefly identified with inor- 

 ganic researches. Mineral chemistry received a great deal of atten- 

 tion, the relatively simple acids, bases, and salts were studied, but 

 the compounds of carbon were thought to be more complex and 

 received less consideration. To-day, at the close of the century, 

 nearly seventy thousand organic compounds are known, and of 

 these comparatively few were discovered before the year 1830. 

 Since then organic chemistry has been the dominant line of inves- 

 tigation. 



Among the earlier chemists of the nineteenth century it was 

 commonly supposed that organic and inorganic matter were radi- 

 cally different, and that the former could only be produced by the 

 operation of a peculiar vital force. To this view there were some 

 dissentients, Berzelius among them, but experimental proof for their 

 contention was lacking. In 1827, however, Wohler succeeded in 

 transforming the inorganic ammonium cyanate into the organic 

 urea, and the barrier was broken down. The era of synthetic chem- 

 istry had begun. Still earlier, in 1823, Liebig had found that sil- 

 ver cyanate and silver fulminate possessed the same percentage 

 composition; in 1825 Faraday discovered an isomer of ethylene; 

 and Wohler's research now gave a third example of the same kind. 

 Two different substances could contain the same elements in the 

 same proportions, and to explain this fact Berzelius inferred differ- 

 ent arrangements of atoms within the molecule, and suggested that 

 their mode of union might be determined. A working theory, 

 however, was still lacking, and without it progress was necessarily 

 slow. The dualistic hypothesis explained the phenomena only in 

 part, and as the known facts increased in number it had to be 

 abandoned. 



Two important investigations paved the way for an advance. 

 In 1832 Liebig and Wohler, studying benzoic acid, found that it 

 and its derivatives contained in common a group of atoms, not iso- 

 lable by itself, to which they gave the name of benzoyl. The con- 

 ception of such a group, a compound radicle, already existed, but 

 it lacked clearness, and now for t"he first time it became truly a 

 scientific idea. The search for, and the identification of, compound 



