Molecular tkcomposition and Recomposition. 349^ 



Grotthus, on the supposition of a series of molecular decom- 

 positions and recompositions. This theory has become almost 

 universally adopted by electro-chemists; I have frequently 

 availed myself of it in my lectures, and, though with some 

 doubt and hesitation, have applied it to explain the action of 

 the gas battery. I have ever been anxious, if possible, to ac- 

 count for new phaenomena by generally received theories, one 

 main object of a theory being to collate facts in a manner 

 which may render them conventionally intelligible, while plu- 

 rality of theories introduces anarchy into science. ^ ,,< 



It has lately, however, struck me very forcibly that the gas 

 battery presents a strong objection to the theory of Grotthus, 

 or in other words, that it places us in a dilemma in which we 

 must either abandon this theory or the generally received 

 views (I think I may say established laws) of chemical affinity. 

 My difficulty is this. In a single pair- of the gas battery, we 

 must, according to the theory of Grotthus, suppose that oxy- 

 gen and hydrogen tear asunder oxygen and hydrogen already 

 united ; for whether we suppose the action to begin at the hy- 

 drogen extremity of the electrolyte, or at the oxygen, or at 

 both simultaneously, the force which produces the composition 

 of water is regarded by the theory sufficiently strong to over- 

 come the force by which its constituents are already ,^^i,l;e,dj 

 i,e. a force is equal and unequal at the same time. ,iiihr(i u 



The gas battery also presents cases where, according to this 

 theory, a more feeble affinity overcomes a more powerful one, 

 as when water is the electrolyte and deutoxide of nitrogen and 

 oxygen the gases : we have indeed some instances in chemistry 

 where the oi'der of affinities is reversed, as in the decomposi- 

 tion of water by iron, and of oxide of iron by hydrogen, sup- 

 posing the oxide to be the same in each case, which is much 

 doubted ; but we have no instance, as far as I am aware, of 

 the divellent and quiescent affinities being identical, as for in- 

 stance, the affinity of oxygen for hydrogen decomposing water, 

 that of oxygen for iron decomposing oxide of iron. Where 

 water is decomposed at the electrodes by a series of the gas 

 battery, the same difficulty does not arise ; as, abandoning all 

 theory as to the transfer in the cells of the battery, there is 

 nothing inconsistent in the fact, that the reduplicated force of 

 a series of affinities should overcome an equal or stronger af- 

 finity taken singly, just as we decompose potash by a series of 

 affinities of zinc for oxygen ; but in the single cell there is no 

 such exaltation of intensity. 



It may be said that the pulverulent platinum exalts the che- 

 mical energies of the gases, but this I think is inconsistent 

 with all we know of the catalytic action of platinum ; all the 



