362 ox TWO >E"V\' CRYSTALLINE COMPOUNDS 



case of a solution of chloride of platinum. After the platinum had been deposited on the 

 granules, and the surfaces had been thus blackened, the alloys were thoroughly washed 

 with water, and the experiments conducted as in the other two cases. These experi- 

 ments were made with the same alloys as those from which the numbers of column 1 

 were obtained. As, however, in the experiments with bichloride of platinum, new and 

 obvious causes of irregularity were introduced, that did not exist in the other two sets 

 of experiments, no great uniformity can be expected on comparing the results. The 

 two main facts, however, noticed in the columns 1 and 3 of the table, are quite as 

 prominent in column 2, and also the additional fact that the presence of platinum very 

 greatly increases the rapidity of the evolution of hydrogen from the alloys. 



One set of results given in the table requires particular notice, — those obtained from 

 2mre zinc, to be found on the first line opposite per cent of antimony. It is stated AA-ith 

 great confidence, by all chemical authors* who have written on the subject, that zinc 

 does not decompose water at the boiling temperature. On this account the experi- 

 ments with pure zinc were made with peculiar care, and repeated several times, great 

 pains being taken to insure that both the zinc and water employed were perfectly pure. 

 There is no doubt in regard to the fact of the decomposition, which becomes, as is 

 shown in the table, quite rapid w^hen the afiinity of the zinc is strengthened by the 

 galvanic action of the platinum. 



It has already been shown, that, when the alloys of zinc and antimony are treated 

 with hydrochloric or sulphuric acid, they are, as a general rule, and under favorable 

 circumstances, completely decomposed, the zinc uniting wdth the acid, and the greater 

 part of the antimony separating as a black powder, only a very small amount ever, 

 even under the most favorable circumstances, escaping as antimoniuretted hydrogen. 

 When the alloys are in granules, it is almost invariably the case with those containing 

 more than 50 per cent of antimony, that after a short time the acid ceases to act, owing 

 to the formation of a coating of antimony on the surface. The action is, of course, re- 

 newed on reducing the alloy to powder, but here, as in other alloys, the less oxidizable 

 metal appears to be able to protect entirely a certain amount of the other from the ac- 

 tion of acids. 



These facts, in connection with those pre\dously stated in regard to the increased 

 action of the alloys on water in presence of platinum, sufficiently explain the remark- 



* Since this was written, and first published in the American Journal of Science for September, 1854, 1 

 find that Deville has noticed the fact of the decomposition of boiling water by zinc. Comptes Rendus, 

 14 Aout, 1854, p. 322, note. 



