Platina and Mercury upon each other. log 



poured into a solution of muriate of platina, a mercurial 

 muriate of platina is precipitated. The supernatant liquor 

 may be decanted and the residuum washed ; if this be re- 

 duced and afterwards dissolved in nitro-muriatic acid, it 

 will yield a precipitate with green sulphate of iron. This 

 method appears to me to be the neatest for coml)inini2; pla- 

 tina and mercury, as the action which takes place is inde- 

 pendent of every substance except the metals themselves. 



Exp. 9. One of the most delicate tests that I have ob- 

 served in chemistry is recent muriate of tin, which detects 

 the presence of the smallest portion of mercury. When 

 a. single drop of a saturate solution of neutralized nitrate or 

 muriate of mercury is put into 500 grains of water, and a 

 few drops of a saturate solution of recent muriate of tin are 

 added, the liquor becomes a little turbid, and of a smoke- 

 gray colour. If these 300 grains of liquid be diluted with 

 ten times their weight of water, the effect is of course di- 

 minished, but still it is perceptible. I had on a former oc- 

 casion observed the action of recent muriate of tin upon a 

 solution of platina. If a solution of recent muriate of tin 

 be poured into a mixed solution of platina and mercury, 

 not too concentrated, it can hardiv be dijtinguished from a 

 simple solution of platina. But if too much mercury be 

 present, the excess is acted upon as mercury ; and the liquor 

 assumes a darker colour than with platina alone. 



From all these experiments it is evident that mercurv can 

 act upon platina, and confer upon it the property of being 

 precipitated in a metallic state by green sulphate of iron. 

 By Experiments 1 and 2, it is proved, 1st, That platina can 

 protect a considerable quantity of mercurv from the action 

 of nitric acid : and, 2dly, That mercurv can incretlse the 

 action of nitro-muriatic acid upon platina. From Experi- 

 ments 3, 4, 5, 6, 7j 8, it appears that mercury can com- 

 bine with platina in such a manner as not to be separated 

 by the degree of heat necessary to fuse the compound, since 

 after the fusion it retains that propertv, which is essentially 

 characteristic of the presence of mercury in a solution of 

 platina. The eighth Experiment proves that the action of 

 mercury upon platina is not confineti to the metallic state; 

 but that these metals can combine and form an insoluble 

 triple salt with an acid which produces a very soluble com- 

 pound with platina alone. The ninth Experiment shows 

 that platina can retain in solution a certain tjuantitv of mer- 

 cury, and prevent its reduction by a substance which acts 

 most powerfully to that effect, when platina is not present. 

 That p^rt ojf the general position, tlicrcfore, which is the 

 3 object 



