162 MR CONNELL ON THE VOLTAIC DECOMPOSITION OF 



C, containing distilled water, A being made negative, and C positive, by 72 pairs 

 of 4-inch plates. The whole tubes were covered with a close glass covering, a 

 piece of turmeric paper having been introduced into the liquids A and C, between 

 the asbestos and the poles. In a few minutes alkali was indicated at the negative 

 pole, and went on increasing during half an hour, whilst the test-paper in C was 

 not discoloured, shewing that the effect in A was not due to capillary action. 

 The experiment was then stopped, when the water in A, although not alkaline to 

 test-paper throughout, became decidedly so by concentration, whilst that in C 

 shewed no alkali even after concentration. 



In the experiments also, already detailed, in which acid and alkali were 

 separately drawn to the poles in distilled water, from saline solutions, the alkali 

 usually reached the pole as soon as the acid. 



There can thus be no doubt that by voltaic action the alkali in an aqueous 

 solution is transferred to the negative pole. 



Water coloured by bromine gives sensibly more effervescence under galvanic 

 action than distilled water, shewing a superior conducting power of the solution. 



The manner in which such simple substances increase the conducting power 

 of water requires a little investigation. Chlorine, bromine, and iodine, are gene- 

 rally admitted not to be conductors themselves ; and, even if a little doubt may 

 exist as to iodine in a state of fusion, it is scarce possible that the minute quantity 

 of it in an aqueous solution can operate in that way. 



To ascertain whether such substances are capable of transference in solu- 

 tion, an aqueous solution of bromine, with a little undissolved bromine at the 

 bottom to maintain a state of saturation, was placed in the tube B, the arrange- 

 ment being in all other respects the same as in the last described experiment, with 

 a solution of potash; and after nearly an hour's action of 72 pairs of 4-inch 

 plates, no discoloration from transference of bromine could be observed in the 

 water either of A or of C, and the latter had only a scarce perceptible smell of 

 bromine, which I believe was due to the secondary decomposition of a trace of 

 hydro-bromic acid, drawn into C, as both the liquids B and C shewed some 

 degree of acid reaction. 



An aqueous solution of iodine was then substituted in B for that of bromine, 

 a little iodine being also left at the bottom, and all other circumstances the same, 

 and the battery recharged. After an hour's action there was no appearance of 

 iodine either in A or C. 



From these experiments it is obvious that neither of these substances are 

 transferred in solution under voltaic agency. We must, therefore, look for some 

 other explanation of the increased conducting power ; and that which readily 

 occurs is a secondary action at the negative pole, by the union of hydrogen with 

 the dissolved substance. To determine the accuracy of this view, the current 

 from 50 pairs of 2-inch plates was passed at the same time through a solution 



