A CENTURS" OF CHEMISTRY. 99 



vestigated these substances and proved their identity 

 with an oil obtained long before by Zinin from 

 indigo, and applied to them all Zinin's term, Anilin. 

 The substance was curiously interesting, and Hof- 

 mann worked out its reactions, discovering that with 

 many materials it gives brilliant colours. The prac- 

 tical application of these discoveries was not long de- 

 layed, for Perkin made it in 1856. The usefulness 

 of the dyes led to deeper studies of coal-tar products 

 to which is due the discovery of such substances as 

 antipyrin, phenacetin, ichthyol, and saccharin, which 

 have proved so important in medicine.'' * 



Wohler's Synthesis of Urea. — As analyses of or- 

 ganic substances accumulated, it became perfectly 

 clear that the stuffs composing and formed by living 

 creatures did not contain any peculiar elements. It 

 was seen that they consisted of compounds of carbon 

 with hydrogen, oxygen, nitrogen, and other elements 

 familiar in the organic world. 



Those who thought it important to emphasise the 

 distinctions between the living and the not-living 

 then fell back upon the assertion that it was in the 

 arrangement of the elements that the uniqueness of 

 organic substance lay. It was an architectural not a 

 material distinction, and the architect was Vital 

 Force. 



It was in the midst of these opinions that Wohler 

 in 1828 effected the synthesis of urea — the character- 

 istic waste product of higher animals. Starting 

 with cyanic acid, which he had discovered in 1822, 

 he found that urea was formed upon the evaporation 

 of a solution of its ammonium salt. Without the 

 aid of vital force he had formed from a simpler sub- 

 stance a characteristic organic product. It should 



* J. J. Stevenson, Rep. Smithsonian Inst, for 1897, p. 330. 



