frequent investigation from then till now; and different views of its constitution, from time to time, have been put forward. But no one of these views has received a sufficiently general acceptance to warrant the designation of the compound in accordance therewith; so that, from the period of its discovery down to the present day, it has ever borne the honoured name of its discoverer, and been known as the green salt of Magnus. Some time after, Gros, in 1838, by treating the salt of Magnus with nitric acid, obtained a peculiar series of pale yellow, or colourless, platin-ammonia compounds. Next, in 1840-44 et seq., Reiset and Peyrone, by acting on the salt of Magnus, or on platinous chloride itself, with ammonia, obtained, independently of each other, two additional series of compounds, having relations of metamorphosis both with one another and with the foregoing series of Gros. Then, in 1846, Raewsky, by acting on the salt of Magnus with nitric acid, obtained yet another series of compounds, differing from those furnished to Gros by the same reagent. But the formula, attributed by Raewsky to the salts which he had just discovered, were inconsistent both with Laurent's view of ammonia as a type, and with other views of chemical constitution which those illustrious fellow-workers Laurent and Gerhardt shared in common. Accordingly, Gerhardt, in 1848, subjected Raewsky's formulæ,-notwithstanding their corroboration by a Committee of the Academy,-to a most trenchant criticism; and after supplementing his criticism by laboratory research, published in 1850, his celebrated memoir "On the Ammoniacal Compounds of Platinum." In this memoir he established the existence of another, entirely new, series of platin-ammonia compounds; he showed, by experiment, the simple relationship in which the salts of Raewsky stand to the salts of Gros; and he set forth a complete, self-consistent scheme of viewing the several series of platin-ammonia compounds in their relations to ammonia and to one another. Since the publication of Gerhardt's memoir, further important contributions to the knowledge of platin-ammonia compounds have been made by different chemists, especially by Buckton, Hadow, and Thomsen. But neither before or since has any complete general scheme of the constitution of this class of bodies been put forward. Nevertheless the scheme of Gerhardt, though always treated with respect, has never met with general acceptation, and nowadays, at any rate, is open to very serious objections.* The attention of the writer having of late been directed to the study of these compounds, he has succeeded in differentiating the simplest of the platinum sal-ammoniacs from several allied and isomeric bodies with which it had before been confounded; and in obtain *Gerhardt's own base platinamine, for instance, is represented by the certainly improbable formula pt, HN or Pt"HN, and its hydrochloride by the yet more improbable formula pt, HN. 2HC1; in which the unit of a mon-ammonia is represented as combined with two units of hydrochloric acid, and by which the entire chlorine of the salt is represented as fulfilling one and the same function. N ing from it the corresponding hydrated base of the series. He has also obtained some reactions of interest with bodies belonging to the more complex series; and, as a general result of his inquiries, has ventured to put forward a new scheme of regarding the entire group of bodies. This scheme is based on the recognition of two principal facts or propositions: 1°. The different platin-ammonia compounds are produced in the first instance from platinous chloride PtCl"; and just as the platinum of this compound possesses the property of taking up two additional proportions of chlorine so as to furnish the platinic compound Cl,PtCl, or Pt'""'Cl, so also does the platinum of the different ammoniated bodies obtained from platinous chloride possess the property of taking up two proportions of chlorine, or its equivalent of other negative radical, so as to furnish platinic compounds corresponding to the original platinous compounds respectively. Hence the division of platin-ammonia compounds into the two classes of platinous and platinic; the compounds of the former, differing in constitution from those of the latter class, just as platinic differs from platinous chloride, by a direct fixation of chlorine. 2o. The monad residue or radical amidogen H,N, is capable of becoming the monad radical ammon-amidogen H.N.H.N or H,N, just as the monad radical methyl HC, is capable of becoming the monad radical methylen-methyl or ethyl H.C.H,C or H,C,.* Viewing sal-ammoniac H.N.HCl as the analogue of methylic chloride HC HCl, the difference is noticeable, that while the ammonia both of sal-ammoniac and ammon-amidogen is easily separable, the methylen both of methylic chloride and methylen-methyl is inseparable from the remaining constituents of the respective compounds. Hence the distinction between the two classes of amic and ammon-amic platinum compounds, the latter differing from the former by an actual addition of diad ammonia, much as ethylic differ from methylic compounds by a virtual addition of diad methylen. The parallelism is indicated in the under-written formulæ for methylic chloride and ethylic chloride, sal-ammoniac and ammonio-chloride of silver, respectively: H2CHCI H2CH H2N. HCI H1N Ag H2NCI The group of platin-ammonia compounds is thus divisible into the two classes of platinous and platinic; and each of these again into the two classes of amic and ammon-amic compounds. To these four classes must yet be added a fifth sub-class of di-platinic compounds, including the nitrate-chloride of Raewsky and the subsequently-discovered nitrate of Gerhardt and chloride of Hadow. The scheme of the constitution of the entire group, in accordance with the writer's views, is exhibited in the accompanying table of the principal chloride, hydrate, nitrate and nitrite compounds. *Phil. Mag.,' 1869, p. 459. PLATINUM BASES AND SALTS. Platosamine. Pt" (H,N). 2HC1 Pt" (H2N), . 2H(HO) Pt" (H,N). 2H(NO,) Cl, Pt"'" (H2N), . 2HC1 Cl2 Pt""" (H2N), . 2H(HO)? (HO), Pt"'" (H,N), . 2H(HO) PROPOSED SCHEME. Amo-platosamine (Reiset's). OPt""" (HN). 2H(NO). 3Aq.? (NO3)2 Pť”” (H,N), . 2H(NO3) Amo-diplatinamine (Raewsky's, &c.). Pt" (H,N2)2. 2HCl. Aq. Cl2 Pt"'" (H ̧N2)2 . 2H(NO3) Cl2O Pt.""" (H,N), . 4HCI Cl2O Pt2""" (H3N2), . 4HNO ̧ . Aq. (NO3)2OPt,””(H‚N2), . 4HNO ̧ . Aq. Platosamine. The hydrochloride is obtainable by direct action of platinous chloride Pt"Cl, on ammonia, just as ethylenamine hydrochloride is obtainable by direct action of ethylenic chloride (C,H,)"Cl,, on ammonia; and, in both reactions, the two compounds are each accompanied by various other products. The parallelism, in constitution and properties, of the two compounds and of their corresponding hydrates is complete : Hydrochloride of platosamine, in its pure state, has a dull, very pale, primrose colour, approaching almost to white. It is very insoluble in cold, considerably more soluble in hot water. From its concentrated hot solution it is usually deposited as a flocculent-looking, though really crystalline, or partly crystalline, precipitate; and by slow cooling of the solution, it may be obtained wholly in the form of distinct needles. The base is obtained from the hydrochloride, through the intervention of the sulphate, by decomposing the latter with baryta water. It is extremely soluble in water, and readily crystallizable. It furnishes a solution manifesting a strongly alkaline reaction, liberating ammonia from its salts, neutralizing acids, absorbing carbonic acid from the air, and decomposing metallic salts the precipitates thrown down being, however, for the most part double compounds. The orange-yellow, scaly, far more soluble hydrochloride, obtained by dissolving salt of Magnus in sulphate of ammonia solution, is a distinct compound. The base and other soluble platosamine compounds are characterized by giving with hydrochloric acid a precipitate of the hydrochloride, which, when formed in this way, is almost always yellow and crystalline. All platosamine compounds, including the hydrochloride, exhibit the platinous property of absorbing chlorine, and hence of decolourizing a mixture of hydrochloric acid and permanganate, to yield platinamine compounds; and they all, including the hydrochloride, dissolve in gently-heated ammonia, to yield their corresponding amo-platosamine compounds. Amo-platosamine. The hydrochloride of this series, unlike that of the preceding, is freely soluble in water. It is a beautiful salt, crystallizing usually in a mass of interlaced lengthy needles. It is made by dissolving platinous chloride, salt of Magnus, or the above platosamine hydrochloride, in aqueous ammonia at a gentle heat. The hydrated base is obtained from it, as is the preceding hydrated base from the preceding hydrochloride. The so-produced hydrate corresponds in its general properties with the above hydrate of platosamine, than which, however, it is far more powerfully alkaline. From different metallic salts it throws down the respective metallic hydrates. Amo-platosamine salts, like those of platosamine, exhibit the platinous property of decolourizing a mixture of hydrochloric acid and permanganate, of directly absorbing chlorine or bromine, and also of directly absorbing nitric peroxide, to furnish amo-platinic compounds.* The resulting amo-platinic chloro-chloride occurs as a pale yellow, the nitro-chloride as a pale green, and the nitro-nitrate as a pale blue precipitate. Amo-platosamine is further distinguished from platosamine by the free solubility of its hydrochloride, and by the reaction of this salt with platinous chloride solution to throw down the green salt of Magnus. Platinic Compounds. The most characteristic of the salts of platinamine is the chloride Cl,Pt''''(HN), . 2HCl. It is best made by addition of permanganate, in very slight excess, to a hot solution of platosamine hydrochloride, acidified with hydrochloric acid. It is a beautiful bright yellow salt, dissolving sparingly in cold, moderately, though, on account of its density, somewhat slowly, in boiling water; and crystallizing readily on cooling in isolated octahedrons or square plates. It reacts with excess of ammonia, at a gentle heat, to form the insoluble chloride of amo-platinamine. Its chlorine, like that of the amo-platinic chloride, is evidently in two different conditions of attackability by reagents, such as alkalies and silver salts. The hydrate of platinamine is ob *The reaction of amo-platosamine compounds with nitric peroxide was discovered by Hadow, but received from him a different interpretation. tained from the hydrate-nitrate, by means of ammonia, as a neutral, almost insoluble, bright yellow, crystalline precipitate. The best known salt of amo-platinamine is the chloro-nitrate Cl,Pt"""(NH),. 2HNO, obtained by treating the salt of Magnus, or preferably the hydrochloride of amo-platosamine, with nitric acid. It is moderately soluble in water, and crystallizes therefrom in brilliant white flat prisms. Its chlorine is not immediately recognizable by nitrate of silver; and is only partially precipitable thereby, even after long boiling. Its solution yields, with ammonium chloride and sodium. sulphate, crystalline white precipitates of the chloro-chloride and chloro-sulphate respectively. The most familiar salt of amo-diplatinamine is the chloroxy-nitrate Cl2OPt."""'(H,N).. 4HNO,. Aq. It is best made by boiling the chloro-nitrate or chloro-chloride of amo-platinamine with nitric acid and nitrate of silver. It presents considerable resemblance to the chloro-nitrate of amo-platinamine, but its solution is not disturbed either by sulphate of sodium or chloride of ammonium. It yields moreover, with platinous chloride solution, a moss-like coppery precipitate which is highly characteristic (Hadow). [W. O.] GENERAL MONTHLY MEETING, Monday, July 4, 1870. SIR RODERICK I. MURCHISON, Bart. K.C.B. D.C.L. F.R.S. Arthur Balfour, Esq. James Davenport, M.D. James Baumgardt Elmslic, Esq. Captain Herbert P. De Kantzow, R.N. were elected Members of the Royal Institution. The Secretary announced the receipt of a Legacy of £2000 from the late ALFRED DAVIS, Esq. M.R.I. for the Promotion of Philosophical Researches. RESOLVED, That the Members of the Royal Institution cannot hear of the munificence of their late fellow-member, Mr. ALFRED DAVIS, without expressing their admiration of the liberality of one, who not only in his life gave large gifts to help the good works of Jews and Christians, but by his will has continued his unrestricted benefactions by many noble legacies. |