Intelligence and Miscellaneous Articles. 291 



throws down the whole of the mercury from solutions of the pernitrate 

 and persulphate, when the separation of basic salts has been prevented 

 by the addition of nitric or sulphuric acid. The zinc does not 

 combine with the mercury, but the latter separates in the form of 

 gray globules, which collect at the bottom of the vessel; the zinc 

 retains its appearance, becoming only somewhat more gray than 

 before the experiment. 



Zinc behaves in the same manner towards a solution of the per- 

 chloride of mercury ; its appearance is not changed, and the mer- 

 cury separates in gray globules ; but when hydrochloric acid has 

 been added to the solution of the perchloride, the immersed bar of 

 zinc soon becomes quite bright and shining. In this reaction no 

 evolution of gas occurs ; only a few bubbles adhere constantly to 

 the bright surface of the amalgamated metal ; the mercury is only 

 imperfectly precipitated, for even after several days its presence may 

 be detected in the solution. It is true that, when the zinc is left 

 for a longer time in contact with the liquid, the mercury is at last 

 entirely separated, but not however as a precipitate of gray globules ; 

 but the whole of it combines with the zinc and amalgamates it. At 

 all events, when free hydrochloric acid is present, the mercury is 

 separated far more slowly, and under totally different phsenomena, 

 than from the solution of the pure perchloride. 



When the experiment is somewhat modified, the result is still 

 more surprising. For instance, if a bar of zinc be immersed in hy- 

 drochloric acid, and when the evolution of liydrogen is very rapid, 

 a solution of perchloride of mercury be added, the disengagement 

 of gas ceases instantly ; the zinc becomes bright, resulting from its 

 amalgamation ; and after several days the mercury is only imper- 

 fectly separated from the solution. If a solution of perchloride of 

 platinum be now added, evolution of hydrogen immediately recom- 

 raences. 



When the mercury has been entirely separated from a solution of 

 the^perchloride by zinc in the form of gray globules, and hydro- 

 chloric acid added, the zinc soon becomes bright and amalgamated, 

 without however the mercury, which has been separated in the form 

 of globules, wholly combining with the zinc. 



The behaviour of amalgamated zinc is very remarkable. Dobe- 

 reiner observed that no evolution of gas resulted on the contact of 

 amalgamated zinc with acids; and recently Millon has drawn atten- 

 tion to the fact, tliat certain metullic solutions hasten the evolution 

 of hydrogen by means of zinc and dilute sulphuric acid (a pliaeno- 

 inenon which has been satisfactorily accounted for by 15arreswii), 

 while a solution of perchloride of mercury retards this disengage- 

 ment considerably. 



Zinc, as is well known, is most readily amalgamated by immersing 

 it in hydrociiloric acid, and tiien rubbing it over with mercury. 

 Zitic thus amalgamated remains perfectly bright when placed in 

 hydrociiloric acid, in which it scarcely dissolves at all, or so little, 

 that only a few bubbles of gas adhere to the shining surface. As is 

 well known, amalgamated zinc behaves, in an electrical point of 



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