120 MR CONNELL ON THE ACTION OF VOLTAIC ELECTRICITY 



pairs of 2-iiich plates, and a solution of starch in another similar tube was con- 

 nected with the negative side, asbestus intervening as usual. Effervescence 

 speedily ensued from both poles, but after forty minutes' action not a trace of any 

 blue colour was observed in either tube. The battery was then reversed. Within 

 two minutes, the blue combination appeared round the negative foil now in the 

 mixed solution, the effervescence ceasing at that pole, but continuing at the posi- 

 tive pole. Had the bromide been directly decomposed, iodine ought to have been 

 liberated, and the blue colour produced in one or other of the tubes before reversal ; 

 but as this change did not occur till after reversal, the effect was due to nascent 

 hydrogen at the negative pole. This hydrogen must have combined with bromine 

 if the bromide is dissolved as such, as is usually held, or with oxygen if the whole 

 or a part of it decomposes water, forming hydrobromic and iodic acids.* It is 

 plain, however, that the experiment is equally effectual on this view as on any 

 other for the purpose to which M. de la Rive applied it, that of detecting iodine 

 in bromine. It does not, however, prove that bromine when in combination with 

 iodine is carried to the positive pole ; but on passing the current from thu*ty-six 

 pairs of 4-inch plates through liquid bromide of iodine, neither water nor starch 

 being present, I found the galvanometer to be decidedly, although not powerfidly, 

 affected ; and although in the course of a few minutes' action I could not notice the 

 appearance of either bromine or iodine at the respective poles, yet the quantities 

 carried to the poles may have been too minute for observation, or they may have 

 been redissolved by the bromide as soon as carried to the extremities. 



III. — Voltaic Action on Alcoholic Solutions. 



In my former voltaic experiments on alcohol, the object was merely to pro- 

 mote the action by dissolving such minute quantities of different substances as 

 served to increase the conducting power of the liquid. At present, it is intended 

 to examine the nature of the changes produced by electric agency on alcohohc so- 

 lutions of greater strength. 



The appearances presented by solutions of acid, alkaline, and saline substan- 

 ces in alcohol under voltaic action have, generally speaking, a great resemblance 

 to those offered by the corresponding aqueous solutions ; and when we consider 

 that water as such enters into the constitution of alcohol, and suffers its ordinary 

 electric decomposition, it is not surprising that this resemblance in the phenomena 

 should take place ; the principal difference being, that oxygen is hardly ever 



* I am quite aware that when both the poles are introduced directly into the mixed solution, the 

 voltaic power being in fresh action, there is effervescence at both poles, along with the appearance of io- 

 dine at the negative ; but in this case I apprehend that a part, although not the whole, of the hydrogen 

 enters into the new combination. 



