It also obviously bears a remarkable relation to the constitution of the fawn-coloured substance, four equivalents of muriatic acid being removed from the latter, and being replaced by one equivalent of ammonia and one of water. D. When the action of the water of ammonia is still longer continued, this brown matter dissolves and a perfectly colourless liquor is obtained, from which nothing separates by cooling. If, however, a quantity of spirit of wine be added, a copious white, or paleyellowish white precipitate is produced. This, on drying, aggregates into a mass like coarse meal, which when powdered is nearly quite white. This substance is not insoluble in water, and dissolves readily in water of ammonia: its solution gives with the oxalic and muriatic acids copious white precipitates, and it dissolves in sulphuric and nitric acids, giving crystalline compounds; when heated it evolves water, ammonia, nitrogen and sal-ammoniac, and leaves metallic platinum. Its analysis was conducted in the usual manner. I. 25 357 grains gave 13:043 of platinum, or 50.94 per cent., and yielded by subsequent treatment 18 552 of chloride of silver, corresponding to 18'03 of chlorine in 100. 24 838 grains gave 9'089 of water, equivalent to 3'91 of hydrogen in 100. 22.102 grains gave 10'1259 cubic inches of pure nitrogen at 30 inches barometer and 32° Fahr., equivalent to 14.69 per cent. II. Another quantity prepared at a different time and of a rather more decidedly yellowish shade than the former was also analysed. 11.406 grains ignited gave 5.741 of platinum, or 50.34 per cent. An accident prevented the determination of the chlorine on that quantity. 17.256 grains, ignited with oxide of copper, gave 6'002 of water, indicating 4.05 per cent. of hydrogen. The residue was treated with nitric acid and nitrate of silver, and gave 12.889 of chloride of silver, equivalent to 18-26 of chlorine in 100. 8 The formula deducible from these analyses is Pt Cl N2 H, O3. One equivalent of platinum.. = 98.8 : 50.83 18.21 14.51 = 8.0 4.11 12.34 From By the application of a gentle heat, some water, apparently of hydration, may be separated from the substance, it however does not exceed one equivalent; when dry, therefore, it probably consists of Pt Cl N2 H, O2. The relation between the formula and that of the brown substance last described, is exceedingly remarkable, for the above may be considered as consisting of (Pt O2 + N H3) + Cl N H1, when dry differing from the brown substance in containing twice as much salammoniac; and this relation is supported by the circumstance that by prolonged digestion in a solution of sal-ammoniac, the brown substance may be converted into this white substance. This body becomes remarkably of interest, inasmuch as the compounds which it forms with acids are found to be identical with the interesting classs of salts recently described by Gros, and that this substance is indeed the compound base which Gros considers to be united with the acids in the bodies which he described. The formula which he assigns to the base he hypothetically assumed was Pt Cl No H, O, identical with that of the substance just described, with the exception of 2 aq, the separation of which is rendered difficult by the facility with which the body is decomposed. I shall hereafter have occasion to notice the influence which our thus finding Gros's base in the present series must exercise on the views which he put forward, but for the present I shall pass to the additional experimental matter. E. If, in the place of precipitating the ammoniacal solution in the cold by alcohol, it be boiled violently so as to expel all the excess of ammonia, a quantity of the body last described falls down mixed with another of a pale brick-red colour. To obtain this last pure, the solution must be evaporated rapidly with ebullition of perfect dryIf then any particles of white or yellow still remain, the mass must be mixed up with more water and again boiled until ultimately a pale brick-red, or a lively flesh-red powder remains behind. ness. The liquor obtained by washing contains much sal-ammoniac. This powder when heated gives off water, sal-ammoniac and am. monia, and leaves metallic platinum. Boiled in water of ammonia it regenerates Gros's base. When boiled in muriatic acid it produces a yellow solution and a white powder, and by boiling in a solution of sal-ammoniac the muriatic salt of Gros's base. It was analysed as follows: 19.077 grains ignited with carbonate of soda, gave 9'659 of metallic platinum, or 50'11 per cent., and then 22.627 of chloride of silver, equivalent to 29.35 of chlorine in 100. 21.963 grains gave, by ignition with oxide of copper, 6.745 of water, indicating 3.41 of hydrogen per cent. Another portion dried at a higher temperature and similarly treated, gave 3.34 of hydrogen in 100. 33.478 grains gave 14.8295 cubic inches of pure nitrogen at 30 barometer and 32° Fahr., amounting to 14.21 per cent. The fornula to which this analysis points is Pt2 Cl3 N, H13 O2, from which the numbers follow: The relation of this substance to that last described is easily to be seen; it consists in the union of one equivalent of muriatic acid to two equivalents of Gros's base. It would, indeed, upon the principles of that chemist, stand in the singular position of an oxychloride of his compound radical, for it is evident that (Pt Cl N2 H6) O + (Pt C1 N2 H) Cl = Pt2 Cl3 N4 H12 O 2 aq. Evidently the manner of formation of this substance is the expulsion of ammonia from Gros's base by the temperature of ebullition and the subsequent combination of the sal-ammoniac of the liquor with the body so evolved. Thus Pt2 Cl2 N4 H:2 O2 losing N II3 becomes Pt2 Cl2 Nз H, O2, and by the addition of N H4, Cl forms the body in question, Pt2 Clз N4 H13 02. I have not hitherto stopped to consider the precise manner in which these several bodies are derived from each other, or from the chloride of platinum, and in order to see more clearly their natural relations, it is necessary to make the change already noticed in the commencement of this paper. Ammonia being amidide of hydrogen, and nothing occuring in the chain of reactions now studied to disturb its constitution, I shall for the future look upon the nitrogen as existing in the state of amidogene, and the formula already described become then as follows:: If we were disposed to consider that the principle which was found so remarkably displayed in the instance of the mercurial compounds held with platinum, and that in those instances where oxygen was present it should be looked upon as existing in the state of water, we might find here numerous additions to the class of metallic amidides; thus the body C. should become, doubling the formula above written, Pt Cl2 + 3 Pt Ad2 + 8 H O, and similarly with the others. But it is exceedingly difficult to say when Pt O2 and 2 Ad H act on one another, whether they unite directly, or whether they mutually decompose, forming Pt Ad, and 2 HO, which then unite; this difficulty exists in all cases where the water cannot be separated without the substance being completely decomposed. I would postpone for the moment the consideration of this point, and for the time at least look upon the hydrogen as being equally essen tial with the platinum as a constituent of these bodies. The formation of the first substance described requires no remark. I find that the same body may be produced by the action of dry ammoniacal gas upon chloride of platinum. There is absorbed about 11 or 12 per cent., indicating one equivalent, Pt Cl2 + Ad H; but if the current of gas be continued a white powder is obtained, formed by the union of two equivalents of ammonia to one of platinum, and which is identical with the muriatic salt of Gros, of which the formula may be simply written Pt Cl2 + 2 Ad H. It is evident that the body B. cannot be produced directly from the perchloride of platinum, as that does not contain the quantity of chlorine necessary for its constitution, and indeed, if we examine the ammoniacal liquor from the first commencement of the formation of the fawn-coloured substance, it will yield the body D. on the addition of alcohol. I consider therefore these two bodies as being of simultaneous origin, there being formed from 3 Pt Cl2 with 4 Ad H and 7 HO Pt2 Cls Ada H, O4 and Pt Cl Ad2 H1 O3. From the fawn-coloured substance B., the brown body C. may be simply formed, four equivalents of muriatic acid being removed, and one of ammonia given in their place. This is not equivalent substitution, but it still shows the origin of the body. If, however, the fawn-coloured substance all passed through the brown condition, the quantity of this last generated should, I consider, be much greater than it actually is found to be, and hence I am inclined to consider that From two atoms of B, Pt, Cho Ada H14 08 And ten atoms of ammonia.... There are formed One atom of C...... Two of Gros's base dry Seven of sal-ammoniac Adio H10 Pt Cl Ada H, O4 Pt. Cho Ad, Ha4 Os Pt4 Clio Adi4 H21 08. One source of the origin of the body D. (Gros's base) is thus explained, but it may be produced directly from the fawn-coloured substance as follows: One atom of B........ Ptg Clá Ad2 H7 04 Produce Ads H5 } Pt2 Cl 5Ad7 H12 04 Pt2 Cl 5Ad7 H12 04. In this case no brown substance (c.) should be formed. The origin of the body (E) from Gros's base has been already noticed. Letter from MR. H. DAVY, introductory to the Experiments contained in the subsequent Article, and on other Subjects relative to the Progress of Science. SIR, 1 SEND you for your "Physical Journal," experiments and observations on the flint contained in the epidermis and other parts of certain vegetables: these experiments have been made within the last fortnight. I am induced to make them public so speedily, from the hopes that others, who have greater opportunities and more leisure, may be stimulated to further researches on this interesting subject. I doubt not that other plants will be found to contain silex, as well as the reeds, the canes, and the grasses. In the Pneumatic Institution we have lately made some experiments on the nitrous phosoxyd (gaseous oxyd of azote), the principle of contagion of Mitchell. When it is mingled with one third of phosoxygen (oxygen gas), animals live in it without suffering any injury. I have made two inspirations of it pure, without any disagreeable effects I have breathed it mingled with an equal quantity of phosoxygen (oxygen gas), for some minutes; the effects produced by it were very peculiar: should they be confirmed by future experiments, it will probably prove a very valuable medicine. In my essay on heat, light, &c., in the "West-country Contributions," p. 101, ob. 4, an inaccuracy occurs with respect to the production of this gas. It is said "no light is produced during the decomposition of phosnitrate of ammoniac by heat." In the experiments from which that observation was deduced, no luminous appearance was visible, as the plosnitrate was mingled with a large quantity of siliceous sand, and slowly decomposed by the heat of an Argand lamp. Lately I have made the experiment in the large way when the heat is quickly applied and the phosnitrate mingled with but a small quantity of sand, a vivid luminous appearance is uniformly perceived. A paper on the nitrous phosoxyd will appear in the next volume of Dr. Beddoes' contributions. With the hopes of discovering a cheap substitute for nitre, I have Y |