state of a spongy platinum. 193·25 gr. of the platinic and ammonium chlorides are equivalent to 98·75 gr. of metallic platinum.
Uses. Platinum is valuable for the formation of crucibles, capsules, and other utensils or instruments intended to be exposed to a strong heat, or to the action of acids. Platinic chloride and the platinic and sodium chloride are much used in chemical analysis. Both of these are also used in medicines with the same intentions, and in the same doses, as the corresponding salts of gold. These compounds are poisonous. The antidotes and treatment are similar to those described under Gold.
Concluding Remarks.—Daville and Debray have introduced a method of refining platinum, which has already done much to extend the useful applications of the metal. The process consists in submitting the crude metal to the action of an intensely high temperature, obtained by the combustion of hydrogen (or coal-gas) with oxygen, in a crucible of lime. By this means large quantities of platinum (50 lbs. or more) can be kept fused until the sulphur, phosphorus, arsenic, and osmium, generally occurring in crude platinum, are oxidised and volatilised, and the iron and copper are oxidised and absorbed by the lime forming the crucible. At the International Exhibition of 1862 an ingot of pure platinum, weighing over 2 cwt., was exhibited by Messrs Johnson & Mathey, as an illustration of the practical results of this process.
Platinic Chloride. PtCl4. Syn. Bichloride of platinum, Chloride of platinum, Perchloride of p.; Platini bichloridum (Ph. L.), L. Platini Tetrachloridum. Prep. By dissolving platinum in nitro-hydrochloric acid, and evaporating the solution to dryness at a gentle heat. Prop., &c. Reddish-brown, deliquescent, and very soluble in both water and alcohol, yielding orange-coloured solutions. It combines with a variety of metallic chlorides to form ‘double salts.’ Used as a test in chemical analysis, and as an alterative in secondary syphilis, &c.—Dose, 1⁄16 to 1⁄4 gr., dissolved in distilled water, or made into a pill with syrup and liquorice powder. Some persons prescribe much larger doses, but unsafely. Hoefer recommends an ointment made with it as an application to indolent ulcers. In doses of 5 gr. and upwards it acts as a violent caustic poison. This last salt is the ‘chloride of platinum’ of the shops, and the one used in the arts and medicine. It forms one of the tests included in the Appendix to the Ph. L.
Platinic-Ammonium Chloride. Pt(NH4)2Cl6, or PtCl4 2NH4Cl. Syn. Ammonio-chloride of platinum, Platino-chloride of ammonium. Prep. A solution of chloride of ammonium is added to a strong solution of platinic chloride, and the precipitate washed with dilute alcohol.
Prop. Minute, transparent, yellow octahedral crystals very feebly soluble in water,
less so in dilute alcohol, and insoluble in acids; heat converts it into spongy platinum.
Platinic-Potassium Chloride. PtK2Cl6, or PtCl42KCl. Syn. Platino-chloride of potassium, Potassio-Chloride of platinum. Prep. A bright yellow, crystalline precipitate, formed whenever solutions of the chlorides of platinum and of potassium are mixed; or a salt of potassium, acidulated with a little hydrochloric acid, is added to platinic chloride. In appearance, solubility, &c., it closely resembles ammonio-chloride of platinum.
Platinic-Sodium Chloride. PtNa2Cl6, or PtCl42NaCl. Syn. Chloride of platinum and sodium, Sodio-chloride of platinum, Platino-bichloride of sodium; Platini et sodii chloridum, Platini sodio-chloridium, &c., L. Prep. (Redwood.) Platinic chloride, 17 parts; chloride of sodium, 6 parts; dissolve the two salts separately in water, q. s., mix the solutions, and evaporate, that crystals may form. The crystals are large, transparent, and of a yellow-red colour.—Dose, 1⁄12 to 1⁄2 gr.; in the same cases as the bichloride.
Platinic Oxide. PtO2. Syn. Binoxide of platinum. Prep. 1. By exactly decomposing the platinic sulphate with nitrate of barium, and adding pure hydrate of sodium to the filtered solution, so as to precipitate only half the oxide. (Berzelius.)—2. By boiling platinic chloride with hydrate of sodium, in considerable excess, and then adding acetic acid.