INTENSITY OF CHEMICAL AFFINITY. 5 I 



At this time he has no idea where it is likely to lead 

 him. His philosophy has been directed to the relation 

 between electricity and heat, just, as in his previous work, 

 it was to the relation between electricity and work. But 

 the fundamental character of heat has engaged his atten- 

 tion no more than has that of 'work'; the skin over his 

 curiosity, arising from commonplace familiarity with these, 

 not having yet been pricked. 



For the time his attention is entirely taken up with 

 verifying the remarkable relations he has discovered be- 

 tween the heat of combustion and that resulting from 

 electrolysis. In order to establish the equality of the heats 

 resulting from combustion and electrolysis, he first investi- 

 gates, in a remarkable research, the intensity of the affinities 

 of the various combustibles for oxygen, according to Davy's 

 method, by using the measure of these affinities which is 

 afforded by the electric current. To do this he has to 

 distinguish between the permanent intensities of the electro- 

 lytic cells and those which are transitory. He first grapples 

 with these transitory intensities, and investigates their 

 sources ; discovering that they are to a great, extent owing 

 to the condensation of oxygen on the plates during exposure 

 to the air. He is thus led to realize that the intensity at 

 the instant of immersion, w r hen the negative plate is covered 

 with a film of oxygen, represents the intensity of the affinity 

 of the positive plate for oxygen in the non-gaseous state ; 

 while the permanent intensity represents the excess of the 

 intensity of the affinity of oxygen for the positive plate over 

 its affinity for gaseous hydrogen. He is also led to recognise 

 that the affinity of one substance for another depends on 

 the state (gaseous or liquid) of these substances. 



Taking these things into account, he determines by the 



