216 Mr. Napier on the Electro-decomposition of Salts. 



negative electrode. If, for example, the positive is made to 

 surround the negative, exposing about three times more sur- 

 face, there will be an average of one-third more dissolved than 

 is deposited ; and if, on the contrary, we deposit on the in- 

 side of the vessel, the positive pole being suspended within, 

 there will be about one-fourth more deposited upon the ar- 

 ticle than what is dissolved from the pole; but of course this 

 always varies with the condition of the solution. 



From these, and some of the experiments with cyanide of 

 potassium, hydrochloric acid and the chlorides, it is evident 

 with such electrolytes, that when electrodes are used which 

 combine with the elements set free, the amount liberated or 

 combined with one electrode is not a measure of that liberated 

 at or combined with the opposite electrode; but vv-e must ob- 

 serve, as the result of experience, that the element liberated 

 at the negative electrode is a proper measure of the amount 

 of electricity passing through the electrolyte, if that electrolyte 

 be composed of 1 equivalent of base and 1 of acid, or of sin- 

 gle equivalents of elements; but if asubsaltbe the electrolyte, 

 there will be two proportions liberated at the negative for one 

 proportion of zinc destroyed in the battery; and if a trisubsalt 

 be used, 3 equivalents will be deposited, &c. ; all electrolytes 

 being decomposed as if they were constituted of two elements. 



It uiay be remarked in the second place, from these results, 

 that the stronger the solution of cyanide of potassium is, there 

 is comparatively more dissolved from the positive electrode ; 

 that this may arise from the metals used as electrodes being 

 very soluble in that menstruum, and that the difference be- 

 tween the electrodes is simply the result of this solubility; that 

 it is the result of solubility rather than direct electrolysis, the 

 experiments detailed fully show; but that the electricity in- 

 fluences this solubility I think evident. Pieces of gold, silver 

 and copper, of the same dimensions with the positive electrode, 

 were immersed in solutions of cyanide of potassium, of the 

 same strength with that used in the experimental cell, and 

 kept in the same length of time. When the gold positive 

 electrode had lost 59 grs. above the equivalent of what was 

 deposited upon the negative, the gold plate in solution of cya- 

 nide of potassium had only lost one half-grain, and required 

 eight weeks to lose 59 grs. 



When the silver positive electrode had lost 96 grs. over an 

 equivalent of that deposited on the negative, the plate im- 

 mersed in solution of cyanide of potassium had lost 3 grs., 

 and required twenty-nine days to lose 96 grs. 



When the copper positive electrode had lost 32 grs. more 

 than the amount deposited upon the negative, the copper plate 



