110 ESSAYS BIOGRAPHICAL AND CHEMICAL 



1861, led to a long piece of work on chemical equilibrium, 

 and on 'affinity.' In 1869 he attempted to limit the 

 action of hydrochloric acid on zinc by pressure, but unsuc- 

 cessfully ; and in the same year he investigated the 

 equilibrium between carbon and hydrogen, in sparking 

 acetylene under pressure. And later in that year he 

 announced laws, describing the partition of bodies between 

 two solvents, and he investigated the state of equilibrium 

 in solution. In the same year appeared the first of the 

 long series of researches on thermal chemistry. In 18*75 

 he returned to the subject of chemical equilibrium, deal- 

 ing with the partition of acids between several bases in 

 solution. 



Among other syntheses was that of formic acid from 

 caustic soda and carbon monoxide ; oxalic acid was pro- 

 duced by the oxidation of acetylene ; and acetates, by the 

 slow oxidation of acetylene, in contact with air and 

 caustic potash, in diffuse daylight. 



In 1857 the combination of unsaturated hydrocarbons 

 with the halogen acids was studied, as well as the conver- 

 sion of chloro- and bromo-hydrocarbons into hydrocarbons 

 by reduction. In 1860 ethyl iodide was synthesised by 

 the union of ethylene with hydriodic acid; and in 1867 

 the use of a concentrated solution of hydriodic acid as a 

 universal reducing agent at high temperatures was dis- 

 covered. 



Berth elot's numerous and important researches on the 

 acetylides of silver and copper doubtless led him to pay 

 attention to explosives. Begun in 1862, they were con- 

 tinued until 1866 ; and in that year he enunciated the 

 theory that the production of mineral oils may conceivably 

 have been due to the action of water and carbonic acid on 

 acetylides of the alkaline metals, and to the subsequent 

 resolutions of acetylene at a high temperature into other 

 hydrocarbons. These researches on the acetylides were 



