292 Intelligence mid Miscellaneous Articles, 



view, almost like a distinct metal ; and, notwithstanding it is but 

 little acted upon by acids, is more positive than zinc alone. If, 

 therefore, another metal be placed by the side of amalgamated zinc, 

 •which is in contact with a dilute acid, a powerful evolution of gas 

 immediately results on the former when it touches the amalgamated 

 zinc. It is requisite, however, that, in order to retain its remarkable 

 behaviour, especially towards perchloride of mercury, there must 

 always be some free acid present, Avithout which it acts like ordinary 

 zinc. When an amalgamated bar of zinc is immersed in a solution 

 of perchloride of mercury, the mercury is separated exactly as with 

 pure zinc in the form of gray globules, and the amalgamated zinc 

 loses its bright coating. In the same way amalgamated zinc reduces 

 solutions of the sulpiiate of copper, nitrate of silver and acetate of 

 lead, like ordinary zinc, with this diflerence, that an addition of hy- 

 drochloric or nitric acid does not prevent or retard the reduction of 

 the metals by the amalgamated zinc, as is the case with the solution 

 of perchloride of mercury. 



When only a few drops of hydrochloric acid are added to a solu- 

 tion of the perchloride of mercury, the zinc is amalgamated ; but 

 after some time mercury separates in the form of gray globules, 

 which does not occur wlien a larger quantity of hydrochloric acid 

 has been employed. 



Dilute sulphuric acid acts like hydrociiloric acid in preventing or 

 retarding the precipitation of the mercury from the solution of the 

 perchloride ; frequently, in this case, a fine crystalline salt separates, 

 which however is only perchloride of mercury, which is far less 

 soluble in dilute sulphuric acid than in Avater ; subsequently a cry- 

 stalline powder separates in minute scales, coating the zinc, and fre- 

 quently floating upon the surface of the liquid ; this is the proto- 

 chloride of mercury, which is not furtiier altered by the zinc. It is 

 remarkable that the protochloride is only sepaiated by zinc from the 

 solution of the perchloride when sulphuric acid has been added, and 

 not from a solution of the pure chloride, nor on the addition ofhy- 

 drochloric acid. Moreover, when a solution of the perchloride of 

 mercury is poured upon zinc immersed in dilute sulphuric acid, the 

 evolution of gas suddenly ceases, just as with the addition of hydro- 

 chloric acid. The zinc likewise becomes amalgamated, and a few 

 bubbles of gas adhere for a long time to its surface. Nitric acid 

 also prevents the precipitation of the mercury from the solution of 

 the perchloride by zinc, in the same manner as hydrochloric and 

 sulphuric acids ; in this case the protochloride is also formed. When 

 a violent disengagement of nitric oxide has resulted from immersing 

 zinc in nitric acid, it is instantly stopped by the addition of a solu- 

 tion of the perchloride of mercury. It is well known that neither 

 sulphuric nor nitric acids in the dilute, and also in the concentrated 

 state, are capable of decomposing the perchloride of mercury. 



Iron completely precipitates the oxysalts of mercury in the same 

 manner as zinc ; the metal is likewise wholly separated by iron from 

 a solution of the perchloride, and an addition of hydrochloric acid 

 neither prevent'S the evolution of gas nor the elimination of the nier- 



