Page:Proceedings of the Royal Society of London Vol 1.djvu/142

Rh excite the curiosity of several mineralogists’; and among these, Mr. Chenevix, to whom the manner in which this object was presented to the public appeared suspicious, was among the foremost in pro- curing a sufﬁcient quantity of the substance to enable him to insti- tute a proper analysis by which the fallacy, if there were any, might be detected. The substance, as exposed to sale, had been worked by art: it had been rolled out in ﬂatting-mills, the largest of the lamina being about three inches in length and half an inch broad, and weighing on an average twenty-ﬁve grains each. It had much the appearance of platina; but its speciﬁc gravity was so low as from 10972 to 11'482; that of pure platina in the same state being at least 22. The laminae were ﬂexible, but not very elastic.

After describing these its physical properties, the author proceeds to a circumstantial account of his chemical analysis, and gives an ample detail of the action, on this metal, of caloric; of simple com- bustible bodies, such as sulphur and charcoal; of other metals, form- ing various alloys; of alkalies and acids, in the latter of which he found that the true solvent of palladium was nitro-muriatic acid, ~which attacked it with great violence, and formed a beautiful solu- tion; and lastly, he mentions the appearance and principal proper- ties of the precipitates from its various solutions. From the results of this investigation we learn, that the vender of this substance was not guilty of misrepresentation when he ascribed to it the following properties :—

1. It dissolves in pure spirit of nitre, and makes u. dark red solution.

2. Green vitriol throws it down in the state of a regulus from this solution, as it always does gold from aqua regia.

3.. This solution, when evaporated, yields a red calx, that dissolvcs in spirit of salt or other acids.

4. It is thrown down by mercury and by all the metals except gold. platina, and silver.

5. In a common ﬁre the face of it tamishes a little, and turns blue; but comes bright again, like other noble metals, on being heated to a greater degree.

6. The greatest heat of a blacksmith’s ﬁre will hardly melt it.

7. But if touched while hot with a small bit of sulphur, it runs as easily as zinc.

After maturely considering the results of his experiments, and comparing them with the analogous ones made on the various known metals and combinations of metals, our author acknowledges that he does not ﬁnd to which of them it may be assimilated. The striking resemblance, however, of several of the precipitates of palladium with that of platina, ﬁrst led to the suspicion, that if the former be a combination, the latter is no doubt one of its principal ingredients.

The stubborn circumstance of the very low speciﬁc gravity appeared one of the most difﬁcult to be surmounted; since an alloy of platina, even with tellurium, the lightest of all metals, would not by calculation give so low a standard.