392 Foreign and Miscellaneous Intelligence. 



known, and, indeed, all circumstances accord in pointing out this as 

 the principal source of the heat evolved. 



A striking confirmation of the explanation now given of these 

 exalted effects of common and alloyed zinc, is derived from an in- 

 vestigation of their power of forming voltaic combinations of more 

 or less intensity. Being combined two and two, and examined by 

 the galvanometer, it was found that the order was as follows : dis- 

 tilled zinc, lead zinc, tin zinc, iron zinc, zinc of commerce, and copper 

 zinc: thus arranged, the most positive are first, or each is positive 

 with those following it, negative with those preceding it. When 

 combined into voltaic pairs with copper, distilled zinc, lead zinc, and 

 tin zinc, were most powerful, then zinc of commerce, and iron zinc ; 

 copper zinc was last, and very inferior to the rest. It appears, 

 therefore, that the kinds of zinc which exhibit least action in diluted 

 sulphuric acid are those which form the most powerful voltaic com- 

 binations with such metals as copper, silver, platina, &c., and this 

 might be expected : for the disengagement of hydrogen on the sur- 

 faces of the zincs does not arise from a direct chemical action, but 

 from the action of the minute electric currents established between 

 the molecules of the zinc and the heterogeneous metal present in it ; 

 whereas the current, sensible to the galvanometer, is produced by 

 the direct action of the acid on the positive element of the pair of 

 plates used. This direct action is stronger on the pure zinc than on 

 the zinc mixed with less oxidable substances ; and the less these 

 heterogeneous substances are oxidable, the less positive should the 

 zinc be*, This distinction will probably explain many apparent 



* Is not the diminished power of the alloys in forming voltaic combination 

 with more negative metals due rather to the circumstance of their finding the 

 negative element ready for them, under more favourable circumstances, than that 

 which, in the form of a copper plate or platina wire, is purposely added by the ex- 

 perimenter ; than to any material diminution of the direct chemical action ? The 

 heterogeneous metal originally in the zinc forms a voltaic combination with it, 

 having great extent of surface, because of itsjninute division, in excellent contact, 

 and at the smallest possible distance ; and therefore must divert the course of 

 much of the electricity which in pure zinc finds its exit into the fluid only by the 

 negative element purposely added. 



We refer our readers to a similar effect to the above remarked by Messrs. Stodart 

 and Faraday, in their paper on alloys of steel, and which they also referred to voltaic 

 action. ' If two pieces, one of steel, and one steel alloyed with platina, be im- 

 mersed in weak sulphuric acid, the alloy will be immediately acted upon with 

 great rapidity, and the evolution of much gas, and will shortly be dissolved, whilst 

 the steel will be scarcely at all affected. In this case it is hardly possible to com- 

 pare the strength of the two actions. If the gas be collected from the alloy, and 

 from the steel, for equal intervals of time, the first portion will surpass the second 

 some hundreds of times. A very small quantity of platina alloyed with steel con- 

 fers this property upon it; ? i 5 increased the action considerably; with 5 i^ and 

 j 5 it was powerful; with 10 per cent, it acted, but not with much power; with 

 50 per cent, it was about equal to steel alone.' These alloys were very perfect ; 

 that which was most active in acids did not render a platina wire more negative 

 than ordinary steel, and the cause, as was suggested at the time by Sir H. Davy, 

 is referred to electrical action, the view taken being described at length in the 

 paper in the Phil. Trans, for 1822, p. 262. 



