Page:Proceedings of the Royal Society of London Vol 1.djvu/199

Rh mercury be present, the excess is acted upon as in the case of mer- cury, the liquor assuming a darker colour than with platina alone.

From the above experiments, Mr. Cheuevix infers that mercury can act upon platina, and confer upon it the property of being pre- cipitated, in a metallic state, by green sulphate of iron. The ﬁrst and second experiments prove, he says, that platina can protect mer- cury from the action of nitric acid; and also that mercury increases the action of nitro-muriatic acid upon platiua. The third, fourth, ﬁfth, sixth, seventh, and eighth experiments show that mercury can combine with platina, in such a manner as not to be separated from it by the degree of heat necessary to fuse the compound. The eighth experiment proves that the action of mercury upon platina is not conﬁned to the metallic state, but that these metals can combine and form an insoluble triple salt, with an acid that produces a very so- luble compound with platiua alone. The ninth experiment shows that platina can retain in solution a certain quantity of mercury, and prevent its detection by a substance which acts powerfully when pla- tiua is not: present.

Mr. Chenevix admits that one or two of the above-mentioned ex- periments appear to contradict some of those he described in his former paper on Palladium; for in the present experiments, " platina protects mercury against the action of nitric 'acid, whereas in pal- ladium the mercury is not only acted upon itself, but contributes to the solution of platina in the same acid.” The discussion of these objections, Mr. Chenevix says, he shall defer to another opportunity. He also acknowledges that there is some incorrectness in his former paper, with respect to the proportional quantities of the ingredients that enter into the composition of the metallic precipitate formed by means of green sulphate of iron; and after making various remarks on that head, states the mean result to be about 17 parts of mercury, and 83 of platina, when the speciﬁc gravity of the compound was about 16.

Mr. Chenevix concludes by observing, “ that he has as yet seen no arguments of suﬁicient weight to convince him, in opposition to experiment, that palladium is a simple substance. Nothing is more probable, he says, than that nature may form the alloy called palla- dium, and even form it better than we can do; and he thinks that the amalgamation to which platina is submitted before it reaches Europe, is sufﬁcient to account for its containing a small portion of palladium.” With respect to the failure that has happened in the attempts of others to make palladium, he says he is himself too well “ accustomed to such failure not to believe that it will happen, even in well conducted trials ;” but he considers four successful experi- ments, which were not performed in secret, as a suﬁicient answer to that objection.

The experiments above related tend, in his opinion, to conﬁrm his former results; but: he allows that he can prescribe no other means for success than perseverance; and as Messrs. Fourcroy, Vauquelin,