390 Foreign and Miscellaneous Intelligence. 



specific gravity, namely 7.2, and the differences were the same also, 

 when each "were reduced to filings. 



Concluding, therefore, that it was more probably due to the pre- 

 sence of heterogeneous substances in the ordinary zinc, certain 

 mixtures were made of pure zinc and other metals, and four alloys 

 prepared ; the first, contained a tenth of iron filings, added when 

 the distilled zinc was in fusion ; the second, a tenth of tin ; the third, 

 a tenth of lead ; and the fourth, a tenth of copper. These zincs were 

 then tried as the former were, the same quantities of surface being 

 exposed and of gas collected. The following are the results : 



Acid . No. 1, 10 C. No. 2, 10 C. No. 3, 15 C. 



Distilled zinc 3'.27" 1'.50" 0.30" 



Tin zinc . 0'.24" 0'.12'' 0.12" 



Lead zinc . 0'.12" 0'.9" 0.10" 



Copper zinc 0'.4" to 6 0'.6" , 0.3" to 4 



Iron zinc . 0'.4" 0/3" 0.2'' to 1 



Common zinc 0'.4" 0'.3" 0.2" to 1. 



Generally in these experiments the action was at first slow, and 

 then increased more or less rapidly, according to the nature of the 

 alloy, until it had obtained its maximum, which is the rate expressed 

 usually by the time in the table ; the copper zinc formed an exception 

 its action was most rapid at first, and gradually became slower, 

 from the formation of a black crust of oxide, &c. upon it ; this being 

 removed, the rapidity of action was restored. The iron zinc, it may 

 be observed, was acted upon as rapidly as the ordinary zinc of com- 

 merce. 



The circumstances accompanying the phenomena in question are 

 such as to induce a persuasion on the mind that the whole is due to 

 electro-chemical action. The first circumstance is the powerful influ- 

 ence of a heterogeneous metal, mixed with pure zinc, to facilitate 

 the decomposition of water and disengage hydrogen. The second 

 is, that the diluted acid which is most powerful in exciting this action 

 is that which is the best conductor of electricity. By a very careful 

 set of experiments, made with the galvanometer, it was found that the 

 acids 3 and 4, and especially 3, were much better conductors than any 

 other of the mixtures. Former experiments had shown that concen- 

 trated sulphuric acid was a worse conductor than diluted ; but now it 

 was proved that acid, containing between 30 and 50 per cent, of oil 

 of vitriol, was a better conductor than if either stronger or weaker ; 

 and it is precisely such acid which evolves hydrogen most rapidly 

 from ordinary zinc. 



As a further illustration of the influence of voltaic action on zinc 

 dissolving in acid, if a piece of distilled zinc be dissolved in the 

 diluted acid, it requires a certain time to produce a certain quan- 

 tity of gas ; if a platina wire, immersed in the acid, be made to 

 touch the zinc, it, of course, immediately gives out hydrogen ; and the 

 whole quantity of gas from the two metals, under these circum- 

 stances, is twice or thrice what it was before. If the platina wire 



