Page:Proceedings of the Royal Society of London Vol 1.djvu/197

Rh has published, a method of obtaining the above-mentioned liquid, which never fails.

"By taking the reasoning on this subject in its widest extent, Mr. Chenevix thinks We shall be led to conclude, that metals may exercise an action upon each other, even in their metallic state, ca- pable of so altering some of their principal properties, as to render the presence of one or more of them not to be detected by the usual methods. In this is contained the possibility of a compound metal appearing to be simple. But to prove this proposition must be a Work of great time and perseverance, and can only be done by con- sidering, singly and successively, the different cases which it con- tains, and by instituting experiments upon each.”

As an example of the foregoing position, and to prove that mercury and plaﬁna act upon each other so as to disguise the properties of both, Mr. Chenevix states, that when a solution of green sulphate of iron is poured into a solution of platina, no precipitate, nor any other sensible change, ensues; but if a solution of silver, or of mercury, be added, a copious precipitate, in part metallic, takes place. He has tried to produce the same effect with other metals and platina, but has not observed anything similar. From this he thinks it fair to conclude, that “ whenever a solution of platina is precipitated, in a metallic state, by a solutioxfof green sulphate of iron, either silver or mercury is present. He adds, that the precipitation of a mixed so- lution of platina and silver, requires no further caution than to free the salt of platina, as much as possible, from muriatic acid.”

Mr. Chenevix then makes some observations, which cannot well be abridged, on the precipitation of platina by mercury; but which show that " the state of oxidizement of the latter metal, as well as the acid in which it is dissolved, produce a considerable modiﬁcation in the result.” It then occurred to him, that " a method of uniting platina and mercury, Without the intervention of any other metal, or of any substance except the solvents of these metals, might be ac— complished, as in the case of silver and platina:” and he describes an experiment, which shows that when the mercury is at its minimum of oxidizement in nitric acid, the addition of green sulphate of iron is superﬂuous. But, on the contrary, if " mercury be raised to its maximum of oxidizement in nitric acid, no precipitation occurs till the green sulphate of iron is added."

Mr. Chenevix also makes a variety of observations respecting the complicated affinities which take place when the muriates of the above metals are employed. These we shall pass over, and proceed to notice those experiments which form the principal object of this paper. From the ﬁrst experiment it appears, that if a solution of highly oxidized nitrate of mercury is poured into a mixed solution of platina and green sulphate of iron, a muriate of mercury is formed, and also a metallic precipitate; the former is retained in solution; the latter weighs more than the original quantity of platina, even after nitric acid has been boiled repeatedly, and in large quantities, upon it. By exposurc to heat, he acknowledges that little more,