PIERRE EUGJBNE MARCELLIN BERTHELOT 109 



by hydrolysing ethyl- sulphuric acid, obtained by absorbing 

 ethylene in sulphuric acid, taken in conjunction with his 

 synthesis of hydrocyanic acid in 1868, pointed the way to 

 the formation from the elements of innumerable com- 

 plicated compounds of carbon. 



Much light has also been thrown by Berthelot on the 

 alcohols. In 1857 he produced methyl alcohol from 

 marsh-gas by chlorination and hydrolysis; in 1858 he 

 recognised eholesterine, trehalose, meconine, and camphol 

 as alcohols ; in 1863 he added thymol, phenol, and cresol 

 to the same class ; and he showed how to diagnose alcohols 

 by acetylation. 



Turning to the esters, the nature of glycerine occupied 

 his attention in 1853 ; in that year he succeeded in syn- 

 thesising some animal fats, and showing their analogy 

 with esters, as has already been mentioned ; and he pre- 

 pared other salts of glyceryl by submitting it to the action 

 of acids. The action of hydriodic acid was, however, 

 found to yield two substances of a different nature, namely 

 isopropyl iodide, and allyl iodide ; and from the latter he 

 prepared, for the first time, artificial oil of mustard. The 

 analogy of sugars with glycerine led him to investigate 

 the action of acids on sugars, and this resulted in the 

 synthesis of many of their esters. The fermentation of 

 mannite and other polyhydric alcohols was also studied 

 in 1856 and 1857, also the conversion of mannite and 

 glycerine into sugars, properly so called. The esters of 

 pinite, etc., with tartaric acid, were also studied, and in 

 1858, trehalose and melezitose were discovered. In 1859, 

 Berthelot maintained that the action of yeast is not a vital, 

 but a chemical phenomenon ; and he returned again and 

 again to the study of fermentation. 



These and other similar investigations on esters led him, 

 in conjunction with Pean de Saint- Gilles, to investigate 

 the rate of esterification ; and the experiments, begun in 



