CHEMICAL AFFINITY. 143 



of oxygen which united with the zinc in each cell of the 

 battery was exactly equal to the amount evolved at the one 

 platinum terminal, while the hydrogen evolved from each 

 platinum plate of the battery was equal to the hydrogen 

 evolved from the other platinum terminal. 



Supposing the battery to be charged with hydrochloric 

 acid, instead of water, while the terminals are separated by 

 water, then for every 36 parts by weight of chlorine which 

 united with each plate of zinc, eight parts of oxygen would be 

 evolved from one of the platinum terminals : that is, the 

 weights would be precisely in the same relation which Dalton 

 proved to exist in their chemical combining weights. This 

 relation applies to all liquids capable of being decomposed by 

 the voltaic electrical force, thence called Electrolytes ; and as 

 no voltaic effect is produced by liquids incapable of being 

 thus decomposed, it follows that voltaic action is chemi- 

 cal action taking place at a distance, or transferred through 

 a chain of media, and that the chemical equivalent numbers 

 are the exponents of the amount of voltaic action for corre- 

 sponding chemical substances. 



As heat, light, magnetism, or motion, can be produced by 

 the requisite application of the electric current, and as this is 

 definitely produced by chemical action, we get these forces 

 very definitely, though not immediately, produced by chemi- 

 cal action. Let us, however, here enquire, as we have already 

 done with respect to the other forces, how far other forces 

 may directly emanate from chemical affinity. 



Heat is an immediate product of chemical affinity. I 

 know of no exception to the general proposition that all bodies 

 in chemically combining produce heat ; i.e. if solution be not 

 considered as chemical action, and even in that case, when 

 cold results, it is from a change of consistence, as from the 

 solid to the liquid state, and not from chemical action. 



We shall find that the same view of the expenditure of 

 force which we have considered in treating of latent heat 

 holds good as to the expenditure of chemical force when re- 

 garded with reference to the amount of heat or repulsive force 

 which it engenders, the chemical force being here exhausted 

 by mechanical expansion that is, by heat. Thus, in the 



