Mr. Grove on Voltaic Reaction. 443 



chemical force causing the atoms to combine. I now venture 

 to state more explicitly, that it is not precisely the attraction of 

 affinity, but rather the mechanical force expended by the atoms 

 in falling towards one another, which determines the intensity 

 of the current, and consequently the quantity of heat evolved ; 

 so that we have a simple hypothesis by which we may explain 

 why heat is evolved so freely in the combination of gases, and 

 by which indeed we may account "latent heat" as a mecha- 

 nical power prepared for action as a watch spring is when 

 wound up. Suppose, for the sake of illustration, that 8 lbs. 

 of oxygen and 1 lb. of hydrogen were presented to one another 

 in the gaseous state, and then exploded, the heat evolved would 

 be about one degree Fahr. in 60,000 lbs. of water, indicating 

 a mechanical force expended in the combination equal to a 

 weight of about 50,000,000 of lbs. raised to the height of one 

 foot. Now if the oxygen and hydrogen could be presented 

 to each other in a liquid state, the heat of combination would 

 be less than before, because the atoms, in combining, would 

 fall through less space. The hypothesis is, I confess, suffici- 

 ently crude at present, but I conceive that ultimately we shall 

 be able to represent the whole phaenomena of chemistry by 

 exact numerical expressions, so as to be enabled to predict 

 the existence and properties of new compounds. 

 August, 1843. J. P. J. 



LIU. Experiments on Voltaic Reaction. By W. R. Grove, 

 Esq., M.A., F.R.S., Prof essor of Experimental Philosophy in 

 the London Institution*. 



f~\ N the weekly evening meeting of the Royal Institution for 

 ^-** March 13, 1840t 5 1 communicated some experiments and 

 observations on certain phaenomena which I collated under 

 the general term Voltaic Reaction. I then stated, that in cer- 

 tain (probably in all) cases of the development of a voltaic cur- 

 rent a reaction was induced by the voltaic force itself, and that 

 upon the cessation of the initial force the reacting force was 

 apparent in an opposed direction. I showed, moreover, that 

 the diminution or removal of this reaction was one means of 

 increasing the power of the initial current. This reaction in 

 electrolytes (though it is by no means confined to electrolytes) 

 is what has been generally called polarization, and would be 

 one of the resistances to be taken into account in calculating 

 the resulting power of a voltaic current upon Ohm's theory. 



It recently occurred to me, that as one method of increasing 

 the power of the initial current was to diminish (or, as it were, 



* Communicated by the Author. 



f A report is published in the Phil. Mag., S. 3., vol. xvi. p. 338. 



