AQUEOUS AND ALCOHOLIC SOLUTIONS. 155 



equally inconsistent with the experiments so often detailed, shewing the secondary 

 origin of the electro-negative constituents of the haloid salts, and with the sepa- 

 ration of oxide of zinc from a positive zinc pole, as above detailed. 



In the whole circumstances, there appears to be no reasonable doubt of the 

 general rule which has been above laid down. No binary combination of elements 

 gives way by direct action, in its aqueous solution ; in other words, of all simple 

 substances, oxygen and hydrogen are the most directly opposed in their electric 

 nature, and their combination yields the most readily to voltaic action. When 

 we rise to the next order of combinations, those of binary compounds themselves, 

 a different rule conies into operation ; for then the combination is decomposed 

 with the same facility as the solvent itself, acid and alkali going to then* respec- 

 tive poles at the same time as the elements of water, and, according to the expe- 

 riments of Mr DANIELL, in the same atomic proportion. 



II. Alcoholic Solutions. 



Since my former communication, I have made a similar experiment on an 

 alcoholic solution of hydriodic acid, as those formerly detailed on alcoholic solu- 

 tions of haloid salts, and obtained a similar result. 



Alcohol of 0.793 at 62 F. was charged in a little WOLFE'S apparatus with hy- 

 driodic acid gas, which had been passed over fused chloride of calcium, and was 

 then placed in a tube A* and connected by asbestos with two others B and C, 

 containing distilled water ; A being made negative and C positive by a power of 

 72 pairs of 4-inch plates. Gas soon arose from both poles, but during the first 

 twenty minutes no formation of iodine was any where observed, nor any acid re- 

 action except in A. Afterwards a brown discoloration was observed at the posi- 

 tive pole in C, and at the same time an acid reaction at the same place, and on 

 the asbestos between A and B, and a trace on that between B and C. In half 

 an hour the appearances were the same, but more decided. No iodine was any 

 where observed but in C. The battery was then reversed, when a brown stream 

 from liberated iodine instantly descended from the positive pole, without any 

 elastic fluid from that pole, and with effervescence from the negative pole. 



This experiment would of course have had more analogy to those with aque- 

 ous solutions, if the tubes B and C had contained alcohol instead of water ; but 

 the very feeble conducting power of the former liquid prevented its employment, 

 and the dissolving of any substance to favour the conduction would have interfered 

 with the delicacy of the reactions. The phenomena are, however, best explained 

 on the view that the water of the alcohol only suffers direct decomposition. 



The appearances, when a positive pole of zinc is used in alcoholic solutions 

 of the haloid salts, are instructive, because they tend to identify the circumstances 



* Fig. 2. Plate II., Ed. Trans, xiv. 

 VOL. XV. PART I. T t 



