246 Prof. Connel on the Voltaic Decomposition 



before was observed at the poles, but still in ten minutes no 

 trace of chlorine was observed in either tube by the smell or 

 by test paper. The battery was then reversed, when in less 

 than two minutes a decided smell of chlorine was observed 

 in B, and in ten minutes test paper was bleached when plunged 

 into it. It was also ascertained that no gas but chlorine was 

 liberated from the positive pole subsequent to reversal. When 

 the power was seventy pairs of four-inch plates and the li- 

 quid in B distilled water, acid was detected at the positive pole 

 in three or four minutes; but after half an hour's action no 

 bleaching could be observed in either tube, although a feeble 

 odour of chlorine was latterly observed. The battery was 

 then reversed, when instantly a pungent odour of chlorine 

 arose and test paper was bleached. 



When a moderately strong solution of hydriodic acid was 

 placed in A and distilled water in B, A being negative and 

 B positive, and the power fifty pairs of two-inch plates, a 

 slight effervescence ensued from both poles, and during the 

 first ten minutes there was no discoloration of the liquid in 

 either tube. A slight yellow tint then appeared in the posi- 

 tive liquid and no change in the negative, and shortly after a 

 just perceptible acid reaction was observed in the positive 

 liquid. In a quarter of an hour the battery was reversed. 

 Instantly, notwithstanding the diminished action of the bat- 

 tery, the liquid around the positive foil became brown from 

 liberated iodine, without the least effervescence from that pole. 

 When the level of the hydriodic solution was about a line 

 lower than that of the water, no discoloration took place in 

 either tube in a quarter of an hour, but it was instantly ob- 

 served on reversal. When the power was seventy pairs of 

 four-inch plates, the discoloration began in B in about five 

 minutes, with acid reaction. On revei'sal there was instant 

 discoloration in A, and no gas. 



In these experiments, it seems obvious that the non-appear- 

 ance of chlorine for so long a period, and its speedy appear- 

 ance after reversal with cessation of oxygen, show its secondary 

 origin from the reducing action of oxygen on muriatic acid. 

 If before reversal a trace of it ultimately appeared, its origin 

 was plainly due to the acid which had been some time before 

 drawn over to the positive side. In the case of hydriodic 

 acid the iodine was in like manner due to the reducing action 

 of oxygen ; and if it appeared sooner before leversal than 

 chlorine, that circumstance was due to the circumstance of 

 hydriodic acid being a much weaker combination, and more 

 readily reducible than muriatic acid. Even if we suppose 

 that chlorine or iodine in passing by direct voltaic agency 



