BEKTHELOT 151 



many of its derivations were formed by Berthelot. He 

 also formed methane by passing the vapour of carbon 

 disulphide and sulphuretted hydrogen over hot copper ; 

 and by the action of carbon monoxide on a hot solution 

 of caustic potash, potassium formate was produced, the 

 formate yielding formic acid on distillation with hydro- 

 chloric acid. He formed hydrocyanic acid by the action 

 of the electric spark on a mixture of nitrogen and 

 acetylene. 



Such were a few of the numerous syntheses of 

 Berthelot, or the building up of chemical compounds, 

 many of which were only obtained through the instru- 

 mentality of life, either animal or vegetable. 



His contributions to chemical literature range over 

 practically every department of the science : philosophical, 

 historical, physical, pure, and applied. 



In 1864 Berthelot began his great work on thermo- 

 chemistry, and in 1879 he published his Essai de 

 Mecanique Chimique fondee sur la Thermo-chimie. 

 Although Favre, Silbermann, Andrews, Hess, and Thomsen 

 had previously worked on problems bearing on heat and 

 chemical changes, Berthelot is generally looked upon as 

 the founder of thermo-chemistry. 



His laws are the following : (1) The heat disengaged 

 in any reaction is a measure of the chemical and physical 

 work accomplished in the reaction. (2) The total thermal 

 value of a reaction is dependent only on the initial and 



