832 BASES DERIVED FROM THE CHLORIDES OF PLATINUM. 2 H2O) to 230°, so long as it gives off water and ammonia. It combines with acids, and forms salts, most of which are insoluble, and are decomposed on the application of heat. Hydrochlorate of platosamine (Pt”H ̧N,, 2 HCl) may be obtained by heating the chloride of the following base, so long as it gives off water and ammonia. 4 12 Diplatosamine; Reiset's first base (Pt′′H10N4, 2 H2O).—This substance may be procured as a hydrate in deliquescent needles, which are powerfully alkaline, caustic, and absorb carbonic anhydride from the air. It is usually isolated by decomposing its sulphate by its exact equivalent of hydrate of baryta. In order to prepare its salts, the green compound of Magnus (Pt,Cl ̧H12N) is brought into solution by boiling it for some hours with a solution of caustic ammonia, when the hydrochlorate of diplatosamine (Pt"H10N4 2 HCl) is formed in the liquid and crystallizes easily. If a solution of this salt be decomposed with an equivalent of sulphate of silver, the sulphate of diplatosamine is obtained, and may readily be procured in crystals; the nitrate may be obtained by similar means. 10 Platinamine; Gerhardt's base (PtH,N2, 4 H2O).—This compound may be obtained in the form of striated very brilliant rhomboidal prisms of a yellowish colour. It is nearly insoluble in boiling water, is not decomposed by a boiling solution of potash, but is readily dissolved by diluted acids, and forms a large number of crystallizable, sparingly soluble salts, which are of a yellowish colour. Some of these salts are neutral, and some are acid. Platinamine is usually obtained by adding ammonia to a boiling solution of the neutral nitrate. If chloride of platosamine be suspended in boiling water, and submitted to a current of chlorine, it combines with chlorine, and is slowly transformed into hydrochlorate of platinamine (Ptv H2N,, 4 HCl), and this by long boiling with nitrate of silver is converted into basic nitrate of platinamine (Ptiv H2N2, 2 HNO3, 4 H2O). 2 Diplatinamine is supposed by Gerhardt to be the base of the salts of Gros and of Raewsky; but it has not as yet been isolated. The following table contains the formulæ of the principal series of these compounds which have been ascertained to exist :*— *The following papers may be consulted upon this subject: Gros, Ann. de Chimie, II. lxix. 204; Reiset, Ib. III. xi. 417; Raewsky, Ib. III. xxii. 278; Peyrone, Liebig's Annal. li. 1, and lv. 205; Gerhardt, Comptes Rendus des Travaux de Chimie, par Laurent et Gerhardt, 1849, p. 113, and 1850 p. 273; Buckton, Q. J. Chem. Soc. v. 213, and vii. 22. These different bases may obviously be regarded as ammonias in which 2. Salts of Diplatosamine (Reiset's first base). Diplatosamine (hydrate of) mine Magnus's green salt mine PtH,NO,NO, Pt"H,N,, 2 HNO,. PtH N,,O,HO Pt"H1N4, 2 H, 10 Pt"H1N, 2 HCI 10 Acid-carbonate of dipla-HO,PtH,N,O,2 CO, Pt"H ̧Ñ 2 H ̧¤Ð ̧ tosamine Platinamine 101 49 3. Salts of Platinamine (Gerhardt's base). PtH,NO22 HO PtH,N2, 4 H20 PtH2N,, 4 HCI Normal hydrochlorate of pla-PtH,NCl2 tinamine 2 Basic nitrate of platinamine (PtHNO, NO, PtH ̧N, 2 HNе ̧, 4 H20 Normal nitrate. 3 HO 2 PtH,NO,,2NO, Ptivн2N, 4 HNе.. 4. Salts of Diplatinamine. 8 Diplatinamine (not isolated) PtH.N2O, PtH,N, 2 H2O? 6. Salts obtained by Raewsky (formulæ doubtful). (974) The Perbromide of platinum is a brown insoluble powder. Periodide of platinum (PtI).—On adding iodide of potassium to a dilute solution of tetrachloride of platinum the liquid assumes a deep wine-red colour; the mixture remains clear at ordinary part of the hydrogen in one or in two atoms of ammonia has been displaced by platinosum, Pt", or by platinicum, Pt; platosamine and platinamine being formed upon the type of two atoms of hydrated ammonia (H.N2H2O) and diplatosamine and diplatinamine upon that of 4 atoms (H,,N, 2 H), as will be rendered manifest by examining the formulæ given in the table. *Viewed by Gerhardt as perhydrochlorate and bichloronitrate of diplatinamine. II. 12 4 3 н 834 OTHER SALTS OF PLATINUM. temperatures, but becomes turbid and deposits a brown sparingly soluble powder when heated. Fulminating platinum (PtivH,N,, 4 H2O) is procured as an insoluble black powder by dissolving the chloride of platinum and ammonium in a solution of caustic soda and adding an excess of acetic acid, or by precipitating the sulphate with an excess of ammonia. It may be regarded as a hydrated oxide of diammonium in which 4 atoms of hydrogen have been displaced by one atom of platinum. Hydrochloric acid dissolves this compound, forming with it a very soluble, uncrystallizable salt: other acids. decompose it with formation of ammoniacal salts. If suddenly heated to about 400° it explodes. The persulphate of platinum may be formed by dissolving the oxide of platinum in dilute sulphuric acid, or by treating the bisulphide with fuming nitric acid, and heating, to expel the excess of nitric acid. The pernitrate may be formed by decomposing a solution of the persulphate by an equivalent quantity of the nitrate of barium; both these salts yield insoluble double basic salts on the addition of an alkali. (975) CHARACTERS OF THE SALTS OF PLATINUM. platinous salts are unimportant. -1. The 2. Of the platinic salts the tetrachloride is the only soluble compound of frequent occurrence. These salts are distinguished by the following characters. When heated they are all decomposed, and leave a residue of metallic platinum. They have a brownish-yellow colour in solution: with hydrate of potash, or with any of its salts, they give a yellow precipitate of the chloride of platinum and potassium, which is soluble in a large excess of caustic potash; hydrate of soda precipitates a brown hydrated oxide which is soluble in excess of the alkali: with ammonia, or a soluble salt of ammonium, a yellow chloride of platinum and ammonium is precipitated, which is decomposed by heat, leaving metallic platinum. Sulphuretted hydrogen and sulphide of ammonium give a black sulphide, which is soluble in a large excess of the sulphides of ammonium and of the alkaline metals. Solutions of the salts of platinum are reduced by the mercu rous nitrate, but not by ferrous sulphate. Stannous chloride in acid solutions produces a very deep brown solution, but yields no precipitate; iodide of potassium slowly gives a brown precipitate of iodide of platinum which becomes more abundant when heated. The solutions of the salts of platinum are readily reduced to the metallic state by means of zinc or iron. Oxalic acid exerts no TESTS FOR PLATINUM-PALLADIUM. 835 reducing action upon the salts of platinum, which may thus be separated from those of gold; and after the gold has been precipitated in this manner, the platinum may be thrown down in the metallic form by boiling the liquid with a soluble formiate, taking care first to neutralize the liquid by the addition of carbonate of sodium. (976) Estimation of Platinum.-Platinum may be estimated either in the metallic state, or in the form of a double chloride of platinum with potassium or ammonium. The solutions from which these double salts are precipitated should be concentrated; the complete separation of the salt is favoured by the addition of alcohol; and the washing of the precipitate should be performed with dilute alcohol. Platinum may thus be separated from all the metals hitherto described: 100 parts of the double chloride of platinum and potassium contain 40:43 of the metal; and 100 parts of the ammoniacal salt contain 44 28 of platinum. § V. PALLADIUM: Pd"=106'5, or Pd=53'24. Sp. Gr. 114 to 11.8. (977) PALLADIUM is one of the rare metals which occur chiefly in the ore of platinum, in which it was discovered by Wollaston in the year 1803. It usually forms from a half per cent. to one per cent. of these ores. According to G. Rose, palladium is dimorphous, since it is found native in cubes, and in six-sided plates. In order to extract the metal from the ore of platinum, the solution of this ore in aqua regia is treated with chloride of ammonium with a view to separate the platinum, as already described (966), and to the filtered liquid, cyanide of mercury in solution is added; a yellowish-white, flocculent cyanide of palladium subsides; this is converted into a sulphide by heating it in contact with sulphur, and the sulphur is subsequently expelled by repeated roastings. Another source of palladium is the native alloy which it forms with gold, and which is found in the Brazilian mines. In order to extract the palladium from it, Mr. Cock directs the alloy to be fused with silver, and then boiled in nitric acid, by which all the metals except the gold are brought into solution. The decanted liquid is next mixed with a solution of common salt, by which the whole of the silver is thrown down in the form of chloride, whilst the palladium with the other metals (which consist principally of copper with some lead and iron,) still remains dissolved. Bars of metallic zinc are then introduced into the liquid, and these metals are precipitated upon the zinc in the form of a black powder, consisting of reduced metal. This precipitate is washed and redissolved in nitric acid, supersaturated with ammonia, which dissolves the oxides of palladium and copper, while those of iron and lead are precipitated: the clear liquid is now supersaturated by hydrochloric acid. Palladium is thus thrown down in the form of a yellow, sparingly soluble hydrochlorate of palladamine; by ignition it is reduced, and agglutinates, but does not fuse. A small quantity of palladium still remains in solution, and may be recovered by the introduction of bars of iron. Palladium is a white hard metal possessed of considerable ductility and tenacity. It is not fusible in an ordinary wind furnace, but melts at a lower temperature than platinum. Deville and Debray state that, like silver, it absorbs oxygen when melted, and as the metal cools the globule spits. Before the oxyhydrogen blowpipe it burns with scintillation, and if heated on lime it is slowly dispersed in green vapours. It undergoes no change in the open air at ordinary temperatures; but at a low red heat it becomes covered with an iridescent film, owing to a superficial oxidation; on increasing the heat, the oxygen is expelled, and the metal resumes its brilliant surface. Palladium is dissolved when heated in nitric acid, or in aqua regia, but it is acted upon by the other acids with difficulty. When fused either with acid sulphate of potassium, with nitre, or with the hydrated alkalies, it is oxidized. If a solution of iodine in alcohol be evaporated on a slip of palladium, a stain is left, by which this metal is at once distinguished from platinum. Palladium combines readily with gold, which is rendered brittle by its presence even in small proportion. It has a remarkable power of whitening the colour of gold, even though present in the mixture only in small quantity; and when it forms 20 per cent. of the mass, the alloy is quite white. If alloyed with twice its weight of silver it forms a ductile compound which is not liable to tarnish, and is well adapted for the construction of small weights. When melted with 8 times its weight of tin, at a red heat, an alloy is formed (Pd,Sn), which is obtained in beautiful brilliant lamella on digesting the mass when cold in hydrochloric acid. Palladium has been applied in a few cases to the construction of graduated scales for astronomical instruments, for which, by its whiteness, hardness, and inalterability in air, it is well adapted. (978) OXIDES OF PALLADIUM.-This metal appears to form three oxides a suboxide, Pd,, which furnishes a series of salts |