OXIDATION OF THE ZINC THE SOURCE OF ELECTRICITY. 437 



the platina towards the zinc ; so that the current can pass in that one line, and, whilst 

 it passes, can consist with and favour the renewal of the conditions upon the surface 

 of the zinc, which at first determined both the combination and circulation. Hence 

 the continuance of the action there, and the continuation of the current. It therefore 

 appears quite as essential that there should be an electrolyte in the circuit, in order 

 that the action may be transferred forward, in a certain constant direction, as that 

 there should be an oxidizing or other body capable of acting directly on the metal ; 

 and it also appears to be essential that these two should merge into one, or that the 

 principle directly active on the metal by chemical action should be one of the ions of 

 the electrolyte used. Whether the voltaic arrangement be excited by solution of 

 acids, or alkalies, or sulphurets, or by fused substances (476.), this principle has 

 always hitherto, as far as I am aware, been an anion (943.) ; and I anticipate, from a 

 consideration of the principles of electric action, that it must of necessity be one of 

 that class of bodies. 



925. If the action of the sulphuric acid used in the voltaic circuit be considered, 

 it will be found incompetent to produce any sensible portion of the electricity of the 

 current by its combination with the oxide formed, for this simple reason, it is deficient 

 in a roost essential condition : it forms no part of an electrolyte, nor is it in relation 

 with any other body present in the solution which will permit of the mutual transfer 

 of the particles and the consequent transfer of the electricity. It is true, that as the 

 plane at which the acid is dissolving the oxide of zinc formed by the action of the 

 water, is in contact with the metal zinc, there seems no difficulty in considering how 

 the oxide there could communicate an electrical state, proportionate to its own che- 

 mical action on the acid, to the metal, which is a conductor without decomposition. 

 But on the side of the acid there is no substance to complete the circuit : the water, 

 as water, cannot conduct it, or at least only so small a proportion that it is merely an 

 incidental and almost inappreciable effect (970.) ; and it cannot conduct it as an 

 electrolyte, because an electrolyte conducts in consequence of the mutual relation and 

 action of its particles ; and neither of the elements of the water, nor even the water 

 itself, as far as we can perceive, are ions with respect to the sulphuric acid (848.)*. 



926. This view of the secondary character of the sulphuric acid as an agent in the 

 production of the voltaic current, is further confirmed by the fact, that the current 

 generated and transmitted is directly and exactly proportional to the quantity of water 

 decomposed and the quantity of zinc oxidized (868. 991.) : and is the same as that 

 required to decompose the same quantity of water. As, therefore, the decomposition 

 of the water shows that the electricity has passed by its means, there remains no other 

 electricity to be accounted for or to be referred to any action other than that of the 

 zinc and the water on each other. 



* It -will be seen that I here agree with Sir Humphry Davy, who has experimentally supported the opinion 

 that acids and alkalies in combining do not produce any current of electricity. Philosophical Transactions, 

 1826, p. 398. 



MDCCCXXXIV. 3 L 



