AQUEOUS AND ALCOHOLIC SOLUTIONS. 



of bromine and diluted sulphuric acid, and the hydrogen evolved from the two 

 negative poles collected ; when, after half an hour's action, 0.13 C I were collected 

 from the sulphuric solution, and only a bubble the size of a pea from the brome 

 solution. The difference had evidently combined with bromine. 



When an aqueous solution of iodine, which had been previously purified by 

 sublimation, solution in alcohol, and precipitation by water, was substituted for 

 that of bromine, the action was much more feeble. In a quarter of an hour, only 

 a small bubble of gas was collected from each negative pole ; and in two and a 

 quarter hours 0.1 C I from the sulphuric solution, and 0.077 C I from the iodine. 



It is thus evident that, both in the case of bromine and iodine, the action is 

 increased by the combination of the dissolved substance with hydrogen of the 

 decomposed water, but that, as was to be expected, this circumstance occurs to a 

 much larger extent in the case of bromine than of iodine.* 



On connecting the rules regulating the voltaic decomposition of solutions 

 and the transference of substances held dissolved, we observe that no sub- 

 stance, whilst in a state of transference, suffers direct voltaic decomposition. 

 Acids and alkalies suffer transference, but not direct decomposition. On the other 

 hand, salts, whether oxyacid or hydracid, are not transferred, but are resolved into 

 their constituent acid and alkali. 



We cannot, however, say, that every substance which is not transferred is 

 directly decomposed. Thus we can hardly doubt that such combinations as bro- 

 mide of iodine do not suffer voltaic transference, seeing that their constituent 

 elements, when separate, are not transferred ; and we have farther seen that this 

 combination is not directly decomposed in solution. Probably, also, some cases 

 of chlorides exist, in which, from peculiarity of atomic constitution, or other 

 circumstances, there is neither transference nor direct decomposition. 



* Long after these experiments were made, and conclusions drawn, I observed that M. BECQUEREL 

 had also found that bromine and iodine, in solution, unite with hydrogen under Galvanic Agency. 

 L'Jnstitut. .Tuin, 1840. 



EERATUM in former Memoir, vol. xiv. p. 133, line 2, for latter read former. 



VOL. XV. PART I. XX 



