A Comprehensive Treatise on Inorganic and Theoretical Chemistry

PLATINUM 387
4©. 2585, 1907 ; .Ze**. anorg. Chem.., 83. 36, 1913 ; H. Keihlen, JAebig's Ann., 448. 312, 1926 ;
J. Reiset, ^4?»n. CMm. Fhys., (3), 11. 417, 1844 ; Compt. Rend., 11. 711, 1840 ; 18. HOO, 1844 ;
C. Rudelius, Lmnds Arsskr., (2), 22. 19, 1887 ; A. Schleicher, H. Henkel and L. Spies, Journ.
jprakt. Chem., (2), 105. 31, 1922 ; A. Schleicher and W. Schmidt, Zeit. anorg. Chem., 142. 367,
1925 ; H. Topsoe, Danske SeUk. Forh., 74, 1869 ; L. A. Tschugaeff, Bull. Soc. Chim., (4), 25. 234,
1919 ; L. A. Tschugaeff and M. S. Grigorieff, Ber., 47. 2451, 1914 ; Journ. Buss. Bhys. Chem..
Soc., 51. 193, 192O ; L.. A. Tschugaeff, M. S. Grigorieff and A. Posnjak, Zeit. anorg. Chem., 148.
37, 1925 ; Lt. A. Tschugaeff, M. S. Skanavi-Grigorieva and A. Posnjak, Ann. Inst. PUitine, 4. 299,
1926 ; S. Tyden, Di-tiodiglykolatoplatosyra jamte ndgra saltcr och Additions-Derivat, Lund,
1911 ; G. Wallin, Oefvers. Akad. Forh., 49. 21, 32, 1892; M. Weibull, ZcAt. Kryst., 14. 116,
1888 ; A. Werner, Zeit. anorg. Chem., 21. 235, 1899 ; L. Wohler and F. Muller, ib., 149. 377, 1925.
§ 26. Platinic Iodide
L. Wohler and F. Muller 1 obtained platinous iodide, or platinum diiodide, PtI2,
by heating the triiodide above 400° in a sealed tube. H. D. K. Drew and co-workers
prepared platinous diamminodiiodide, LPt(NH3)2I21, by the action of an excess of an
aq. soln. of an alkali halide on a soln. of the
corresponding chloride ; or by the action of \"\ Pt ' 3
hydriodic acid on the base. The a-salt is a I PtI4 \\ PtI9 \ Pt
pale yellow crystalline powder ; and the 200 0 300" 40o° sod
jS-salt forms orange-yellow, prismatic needles, FIG. 91.—Range of Stability of tho
and gives a reddish-brown colouration with Platinum Iodides,
phenoxtellurine disulphate. L. Wohler and
F. Muller obtained platinum triiodide, PtI3, by heating the tetraiodide at 350° to
400° in a sealed tube. Their observations on the range of stability of the iodides are
summarized in Fig. 91.
J. L. Lassaigne found that when spongy platinum is heated with iodine at
ordinary press., union is incomplete. No platinic iodide, or platinum tetraiodide,
PtI4, is formed when spongy platinum is heated with iodine and water, and with a
mixture of hydriodic and nitric acids, but G. Clementi obtained platinic iodide by
heating finely-divided platinum with iodine in a sealed glass tube below the temp,
of dissociation of the tetraiodide. L. Wohler and F. Muller obtained the anhydrous
tetraiodide by heating platinum with iodine in a sealed tube at 240° to 300° ; the
triiodide is formed at 350° to 400° ; and the diiodide at a higher temp. W. Pullinger
prepared platinic iodide by dissolving platinum in a soln. of iodine in hydriodic
acid, evaporating the liquid to dryness, heating the residue in an air-bath at 180°,
and washing the product with water. G. Clementi obtained the iodide by the
action of hydriodic acid on hydrated platinic oxide ; J. L. Lassaigne, by boiling
a mixture of dil. soln. of platinic chloride, free from acid, and of potassium iodide,
and washing and drying the precipitate. L. Pigeon employed 4 mols. of potassium
iodide to 1 mol. of platinic chloride, or adding the theoretical proportion of potassium
iodide soln. to hydrochloroplatinic acid. II. Topsoe recommended this process.
I. Bellucci warmed on the water-bath a mixture of a soln. of hydrochloroplatinic
acid or magnesium chloroplatinate and a small excess of hydriodic acid.
The precipitate was washed by decantation with boiling water, collected on a filterpaper,
and dried at 100°.
J. "Lt. Lassaigne said that the black precipitate is flocculent and amorphous, or
crystalline ; it has no smell or taste. R. Klement gave 6-064 for the sp. gr. at
25°/4°, and 115*9 for the mol. vol. Ii. Pigeon observed that platinic iodide gives
off iodine at ordinary temp.—1*4 per cent, loss was observed in 24 hrs. ; H. Topsoe
said that very little iodine is lost at 100° ; and J. L. Lassaigne found that iodine
vapour is developed at 130°, and platinum finally remains. W. Pullinger found that
the iodine is not completely removed from platinic iodide by molten sodium
carbonate. L. Pigeon gave for the heat of formation with gaseous iodine, (Pt, 2I2)
—39-0 CaIs., and with solid iodine 17-4 CaIs. F. Jez found the thermionic emission