See also:

• PLATINUM [symbol Pt, atomic weight 145.0 (0=16)]

See also:

• HAUSMANN, JOHANN FRIEDRICH LUDWIG (1782-1859)

re-melted in a reverberatory See also:

• FURNACE

175) obtains pure platinum from the commercial metal by fusing the latter with a large excess of lead. The lead alloy is then treated with a dilute nitric acid and the insoluble portion taken up in dilute aqua regia, From the See also:

• SOLUTION (from Lat. solvere, to loosen, dissolve)

In 1831 platinum ore was recognized in the gold-bearing deposits of See also:

• BORNEO

Native platinum seems to be a mineral of rather wide See also:

• DISTRIBUTION (Lat. distribuere, to deal out)

£ s. d. 1874-1898: 1 5 2 to 2 2 0 1899-1905: 3 13 6 „ 4 10 4 1906: 4 15 2 „ 7 19 8 1907: 7 0 0„ 6 18 8 908: 5 2 6 (average) price. Platinum may be extracted from its ore by both wet and dry processes. In the latter method, due to H. Sainte-Claire-Deville and H. J. Debray, the ore is smelted in a furnace constructed of two blocks of lime, and the metallic See also:

• BUTTON (Fr. bouton, O. Fr. boton, apparently from the same root as bouter, to push)

Journ. Sci., 1909, iv. 28, p. 334) gives the See also:

• GENERAL
• GENERAL (Lat. generalis, of or relating to a genus, kind or class)

401; also C. W. Waidner and G. H. See also:

• BURGESS (Med. Lat. burgensis, from burgus, a borough, a town)
• BURGESS, DANIEL (1645-1713)
• BURGESS, THOMAS (1756–1837)

Bredig, Zeit. phys. Chem., 1901, 37, pp. 1, 323). Platinum is practically unoxidizable; it combines directly with See also:

• PHOSPHORUS (Gr. 4ws, light, sPEpety, to bear)

The hydrated form, PtO.2H2O, is obtained impure by precipitating the dichloride with See also:

• CAUSTIC (Gr. rcavvraubs, burning)

It loses its water of hydration when heated, finally decomposing into platinum and oxygen. When freshly prepared it is soluble in dilute acids. Other hydrated forms of composition, PtO2.3H2O and PtO2.2H2O, have been described (E. Prost, See also:

• BULL
• BULL, GEORGE (1634–1710)
• BULL, JOHN (c. 1562–1628)
• BULL, OLE BORNEMANN (18ro-188o)

They give with sulphuretted hydrogen a dark brown precipitate, soluble in excess of ammonium sulphide. Potassium iodide gives a brown solution with See also:

• GRADUAL (Med. Lat. gradualis, of or belonging to steps or degrees; gradus, step)

(P. See also:

• SCHUTZENBERGER, PAUL (1829–1897)

Schutzenberger, Ann. chim. phys., 187o (4), 21, p. 350). Hydrogen platinochloride or chlorplatmous acid, H2PtCl4, is only known in solution, and as such is obtained when platinum bichloride is dissolved in hydrochloric acid, or by decomposing the See also:

• BARIUM (symbol Ba, atomic weight 137'37 [0=16])

The first forms See also:

• BRIGHT, JOHN (1811-188g)
• BRIGHT, SIR CHARLES TILSTON

394). It forms a reddish brown crystalline mass which is very hygroscopic. Numerous hydrates are known. The chloride is characterized by the readiness with which it forms double salts with the metallic chlorides and with the hydrochlorides of most organic bases. Chlorplatinic acid, H2PtCI6.6H20, is obtained by dissolving platinum in aqua regia containing an excess of hydrochloric acid, or by the See also:

• ACTION

It decomposes at a red heat into platinum, chlorine and potassium chloride. The corresponding See also:

• SODIUM [symbol Na, from Lat. natrium; atomic weight 23.00 (0=16)]

The precipitate must be rapidly washed and dried in vacuo, since it oxidizes rapidly on exposure to air. It is a black powder, which when heated strongly in air decomposes and leaves a residue of platinum, but if heated in See also:

• ABSENCE (Lat. absentia)

PtO2.4H20, in dilute sulphuric acid (I:I) at 0° C. On the addition of See also:

• COLD (in O. Eng. cald and ceald, a word coming ultimately from a root cognate with the Lat. gelu, gelidus, and common in the Teutonic languages, which usually have two distinct forms for the substantive and the adjective, cf. Ger. Kolte, kalt, Dutch koude

The corresponding platino-oxalates M2Pt(C204)2 were first obtained by J. W. See also:

• DOBEREINER, JOHANN WOLFGANG (178o--1849)

Vezes, Bull. soc. chim., 1898 (3), 19, p. 875). These salts are scarcely soluble in water and decompose explosively when suddenly heated. The free acid is obtained by decomposing the silver salt with hydrochloric acid, the See also:

• INDIGO (earlier indico, from Lat. indicum, the Indian sub-stance or dye; the Sans. name was niti, from nila, dark blue, and this through Arab. al-nil, annil, gives " aniline ")

See also:

• PETIT, SIR DINSHAW MANECKJI, BART

The dry salt is exceedingly hygroscopic and is very soluble In water. When boiled with aqua regia it forms the chlorine addition product, K2Pt(CN)4.C12.2H20. It combines directly with iodine. Barium platinocyanide, BaPt(CN)4.4H20, is prepared by the action of baryta water on the copper salt; by dissolving platinum in barium cyanide under the influence of an alternating current; by the addition of barium cyanide to platinum bichloride; or by the simultaneous action of hydrocyanic and sulphurous acids on a mixture of baryta and chlorplatinic acid (P. Bergsoe, Zeit. anorg. Chem., 1899, 19, p. 318). It crystallizes in yellow See also:

• MONOCLINIC

The general formulae of the groups in each series are shown below, the method of See also:

• CLASSIFICATION (Lat. classis, a class, probably from the root cal-, cla-, as in Gr. icaMce, clamor)

; C.W. Blomstrand, Ber. 1871 et seq. ; and A. Werner, Zeit. anorg. Chem. 1893 et seq. A very See also:

• COMPLETE

At 250° finely divided platinum and phosphorus pentachloride combine to form PtC12.PC13, as dark See also:

• CLARET (from the Fr. vin claret, mod. clairet, wine of a light clear colour, from Lat. clarus, clear)