110 On the Action of 



object of this paper is proved, if these experiments, upon 

 being repeated by other chemists, shall be fomid to be ac- 

 curate. 



One or two of the above experiments seem to be in con- 

 tradiction to some that I have stated in my paper upon pal- 

 ladium ; for in the present examples plalina protects mer- 

 cury ao-ainst the action of nitric acid ; whereas in palladium 

 the'mcrcary is not only acted upon itself, but it conduces 

 lo the solution of platina in the same acid. I am well aware 

 of this objection; but, confining myself to my present ob- 

 ject, I shall waive all further discussion of it till another 

 opportunity. In the mean time, however, it may be laid 

 down as an axiom in chemistry, that the strongest affinities 

 are those which produce in any substance the greatest de- 

 viation from its usual properties. 



When a button of the alloy of platina and mercury, as 

 prepared by anv of the above methods, is diisolved in nitro- 

 muriatic acid, and afterwards precipitated by green sulphate 

 of iron, the entire quantity of the alloy used is seldom ob- 

 tained. A considerable portion of platina resists the action 

 of ""reen sulphate of iron, and remains in solution. This 

 may be looked upon as the excels of platina, and can be 

 recovered by a i)late of iron. Hence it appears that less 

 mercury is fixed than can determine the precipitation of 

 the entire quantity of plalina; yet in this state it can draw 

 down a orealer quantity of the latter than when it is merely 

 poured into a mixed solution of platina, not before so treated. 

 Indeed the whole of these experiments tend, not only to 

 show that these two metals exercise a very powerful action 

 upon each other, but that thev are capable of great varia- 

 tion in the state of their combination; and also, that sub- 

 stances possessing different properties have resulted from 

 my attempts to combine platina with mercury. 



This observation furnished me with a method of ascer- 

 taining, or at least of approaching to the knowledge of, the 

 quanttty of mercury thus tixed by platina, and in combina- 

 tion with it. The experiment, however, having been seldom 

 attended with full success, I mention the result with the 

 entire consciousness of the uncertainty to which it is sub- 

 ject. I observed the increase of weight, which the original 

 quantity of platina had acquired in some eases after if had 

 been treated wUh mercury, and fused into a button. I 

 counted that augmentation as the quantity of mercury fixed. 

 I then determined how much was precipitated by green sul- 

 phate of iron from a solution of this alloy, and supposed it 

 to contain the whole quantity of nicrcury found as above. 



But, 



I 



