MR. HEKRY HOW ON IV.-Note on Platinum accovxpanying Silver in s0lutio.n in Nitric Acid. BY HENRYHow (ASSZSTANT TO PROFESSOR ANDERSON.) Having occasion recently to reduce some silver for use in the laboratory of Professor Anderson in Glasgow from the collection of precipitates and filters preserved for the purpose I observed a phenomenon which so far as I am aware has not been noticed and which I make known to the Society in the hope of some of its members being able to afford further information on the subject. It is a well-known fact that platinum in alloy with silver does dissolve in nitric acid but I have not been able to meet with an account in any analytical work of what I observed as to its behaviour when so dissolved. Among the precipitates and filters alluded to although it was intended that none but salts of silver should be present it appears from the facts I am about to state some containing platinum mixed with silver the results of certain investigatioris of Professor An der- son had been introduced.I set about obtaining the silver in the usual way by drying up and burning the mass of residnes and paper in an iron dish and subsequently fusing the charred mass with PLATINUJI ACCOYPANYING SILVER IN SOLUTION. carbonate of soda and some borax to dissolve any iron which might have scaled off from the said dish. A button of silver was obtained which I proceeded to treat with nitric acid. I was surprised to find a blackish-brown powder remain undissolved while the whole of the silver and it alone as I thought went up in the acid.On examining the powder I found it to contain silver but in what state of corn-bination I could not determine; at the time € imagined it to be a boride but I am now inclined to think it must have contained plati- num. I regret from what I observed afterwards I did not submit it to a more rigorous analysis. The acid solut,ion of the supposed pure silver was evaporated to complete dryness and gently heated to expel the excess of nitric acid ; the residue was them. dissolved in a comparatively small quail- tity of water as a strong solution was desired; a little yellowish-broBrn powder remaining undissolved the fluid was filtered. Qn diluting a small portion of this liquid with distilled water I was surprised at seeing a white precipitate falf and was disposed to imagine that by some inadvertence some salts of bismuth or antimony bad heen thrown among the silver residues; however neither of these nietals could be detected.The whole fluid was then diluted and allowed stand a day; a precipitate formed from which the solution was poured off and again allowed to stand. It had rather a turbid appearance and I observed a sediment gradually form in the shape of paie yellow amorphous flocks which went on increasing; after about a week this was collected on a filter washed with water and examined. The sediment was found to dissolve completely in ammonia and for the most part in acetic and in nitric acid. In these acid solutions hydrochloric acid gave a large precipitate which proved to be chloride of silver ; and in the fluid aeparated from this platinum was found to be present in abundance Although 1 did not certainly detect nitric acid I am disposed to imagine from the natuix of the process by which it was obtained that this sediment must have been some basic double-salt of silver and platinum with nitric acid the liquid from which it deposited having an acid reaction.f may mention that it being found that platinum was present I precipitated the whole of the silver in the remaining fluid by hydrochloric acid and reduced it after washing by iron and SO succeeded in obtaining a pure salt of silver. I have ventured to offer this note to the Society as containing a fact I believe new and worthy of consideration in cases of analysis where silver and platinum may OCCUF together in an alloy; as without any intimation of the existence of such a compound as VOL. VII.-hTO. XXV. E UH. PENNY ON that which spontaneously deposits from an aqueous solution of nitrate of silver containing platinum the analyst may be as much surprised as I was to observe its formation and unable to account for it at once. I also think the brown powder which I have described as remaining after the solution of the alloy by digestion in ordinary nitric acid is worthy of attention and further notice.