422 Prof. A. cle la Rive's -Memoir of 



composition. He demonstrates, relying solely upon experiment, 

 that the quantity of chemical action exerted by an electrical cur- 

 rent is proportionate to the quantity of electricity constituting 

 this current ; and, further, that the same quantity of electricity, 

 or the same current, decomposes chemically equivalent quanti- 

 ties of all the compound bodies through which it is passed. Thus, 

 if we place one after the other, in the circuit of a voltaic pile, 

 several pieces of apparatus arranged for the decomposition of 

 water and for collecting the gaseous products of this decompo- 

 sition, we find that in all, even when the degree of acidity of the 

 water and the form and size of the electrodes are different in 

 each, the same current traversing them for a given time pro- 

 duces the same quantity of gas, and consequently decomposes 

 the same quantity of water. The quantity of water decomposed 

 in a given time, appreciated by the quantity of gas evolved, is 

 therefore the exact measure of the quantity of electricity which 

 lias produced this effect. Hence, like Faraday, we give the 

 name of voltameter to the very simple apparatus which holds 

 acidulated water destined to be decomposed by the current, and 

 by means of which the volume of gases set free by this current 

 in a given time may be exactly measured. 



The second principle, that the same quantity of electricity de- 

 composes chemically equivalent quantities of all compound bodies, 

 was demonstrated by Faraday by placing several different electro- 

 lytes one after the other in the same circuit, as, for example, 

 acidulated water in a voltameter, and protochloride of tin and 

 chloride of lead in a state of fusion ; and he obtains quantities of 

 tin, lead, chlorine, hydrogen, and oxygen which are chemically 

 equivalent. Then, rising from the effect to the cause, he comes 

 to the conclusion that there is a perfect equality between the 

 electricity which decomposes a body and that which is generated 

 by the chemical action which produces the direct decomposition 

 of an equal quantity of the same, or of a chemically equivalent 

 quantity of some other body. He is thus led to pay attention 

 to the theory of the pile, and to recognize that the power of this 

 apparatus originates in chemical action, and not in the contact 

 of two heterogeneous metals — a contact which is not necessary 

 either to produce a spark or to cause a chemical decomposition. 



He establishes, in the first place, that, either to effect a de- 

 composition or to produce a spark, a plate of zinc immersed in 

 acidulated water is sufficient without its being necessary to bring 

 the zinc into contact with any other metal. He shows that in 

 every pile the presence of an electrolyte (that is to say, a liquid 

 susceptible of being decomposed) is indispensable for the evolu- 

 tion of electricity. Then, distinguishing in the electricity gene- 

 rated the intensity (or the tension) and the quantity, he studies 



