P vii. On the definite nature and extent of Electro-chemical Decomposition.

783.  In the third series of these Researches, after proving the identity of electricities derived from different sources, and showing, by actual measurement, the extraordinary quantity of electricity evolved by a very feeble voltaic arrangement (371. 376.), I announced a law, derived from experiment, which seemed to me of the utmost importance to the science of electricity in general, and that branch of it denominated electro-chemistry in particular.  The law was expressed thus:  The chemical power of a current of electricity is in direct proportion to the absolute quantity of electricity which passes (377.).

  [A] Annales de Chimie, tom, xxxv. p. 113.

784.  In the further progress of the successive investigations, I have had frequent occasion to refer to the same law, sometimes in circumstances offering powerful corroboration of its truth (456. 504. 505.); and the present series already supplies numerous new cases in which it holds good (704. 722. 726. 732.).  It is now my object to consider this great principle more closely, and to develope some of the consequences to which it leads.  That the evidence for it may be the more distinct and applicable, I shall quote cases of decomposition subject to as few interferences from secondary results as possible, effected upon bodies very simple, yet very definite in their nature.

785.  In the first place, I consider the law as so fully established with respect to the decomposition of water, and under so many circumstances which might be supposed, if anything could, to exert an influence over it, that I may be excused entering into further detail respecting that substance, or even summing up the results here (732.).  I refer, therefore, to the whole of the subdivision of this series of Researches which contains the account of the volta-electrometer (704. &c.).

786.  In the next place, I also consider the law as established with respect to muriatic acid by the experiments and reasoning already advanced, when speaking of that substance, in the subdivision respecting primary and secondary results (758. &c.).

787.  I consider the law as established also with regard to hydriodic acid by the experiments and considerations already advanced in the preceding division of this series of Researches (767. 768.).

788.  Without speaking with the same confidence, yet from the experiments described, and many others not described, relating to hydro-fluoric, hydro-cyanic, ferro-cyanic, and sulpho-cyanic acids (770. 771. 772.), and from the close analogy which holds between these bodies and the hydracids of chlorine, iodine, bromine, &c., I consider these also as coming under subjection to the law, and assisting to prove its truth.