A Comprehensive Treatise on Inorganic and Theoretical Chemistry

PLATINUM 325
According to Li. N. Vauquelin, the hexahydrate loses all its water of hydration
when carefully heated, and leaves the anhydrous salt as an orange-yellow powder.
H. Precht said that the hexahydrate loses most of its water at about 100°.
J. C. G. de Marignac observed that the water is expelled at 100°, W. Peters at
150°, and J. Thomsen at 150° to 160°. M. A. Rakuzin studied the subject. The
anhydrous chloroplatinate was found by L. N. Vauquelin to swell up when more
strongly heated, but it requires a fairly high temp, for its complete decomposition
into platinum and sodium chloride. L. Wohler and P. BaIz observed no evidence
of the formation of complexes of univalent or tervalent platinum in the thermal
decomposition of the salt ; the chloroplatinate is stable below 600°, and above
800°, only the chloroplatinite is formed. G. Gire noted that the heat of formation
is 40-6 CaIs., and the vap. press., p, in mm. of mercury is :
503° 548° 601° 651° 094° 7520° 758"
V . . 6-O 23-2 64-4 252 60/> 848 145O
F. M. Raoult found that the lowering of the f.p. of aq. soln. indicates that in a soln.
of a mol of the salt in 4 litres of water, about a quarter of a mol. is dissociated.
L. Pigeon gave for the heat of formation (PtCl4, 2NaCl) = 13-9 CaIs. for the solid,
and 25-29 CaIs. for the aq. soln. J. Thomsen gave (Pt, 2Cl2, 2NaCl) =73-72 CaIs. ;
(Pt, 2Cl2, 2NaCl, 6H2O) =92-89 CaIs. ; (Pt, 2Cl2, 2NaCl, Aq.) =-84-62 CaIs. ; and
for the reaction between gaseous chlorine and an aq. soln. of sodium chloroplatinite,
43-03 CaIs. ; V. F. Miller and TI. Terry, 40-88 CaIs. ; J. Thomsen, for the heat of
crystallization, 19*17 CaIs., or an average of 3-195 CaIs. for each mol. of water, when
the observed values are 4-32 CaIs. each for the first and second mols, 2-54 CaIs.
each for the third and fourth mols, and 2-725 CaIs. each for the fifth and sixth
mols. The heat of solution of the anhydrous salt is 8-54 CaIs., and for the hexahydrate,
—10'634 CaIs., or for the hydrates :
TT2O 1 2 3 4 5
CaIs. . . +422O -O-1OO — 2-64O — 5-180 — 7-905
F. Doumer found the refractive index to be 0-267 when the value for water
is unity ; and N. S. KurnakofE gave for a 29-123 per cent, soln., and sp. gr. 1 -28259,
the refractive indices 1-38749 for Li-light, and 1-39085 for Na-light ; and the mol.
refraction for Na-light with the /z-formula is 106-5. This makes the at. refraction
of platinum to be 16-1 and 21-0. According to A. Ilantzsch and co-workers, eq.
soln. of hydrochloroplatinic acid, and of sodium chloroplatinate in the same
solvent arc optically identical, that is, show the same absorption spectrum, and
the molecular absorption is independent of the degree of ionization. The
light absorption of the acid and of the salt is also unaffected by changes of temperature.
The solvent does not appear to exercise any influence on the absorption
in the blue and violet parts of the spectrum, but does so to a very slight extent in
the green and ultra-violet. J. Fiedler observed that a soln. of sodium chloroplatinate
is reduced to platinum by exposure to sunlight. JJ. Pigeon found that
the electrical conductivity of a soln. of 0-01 mol of salt in a litre of water is 1-830.
A. von Mussin-Puschkin said that the hexahydrate is freely soluble in water,
and J. Thomsen made a similar observation with respect to the anhydrous salt.
H. Precht found that a soln. sat. at 15° contains 39-77 per cent, of Na2PtCl6, and
that in boiling water it dissolves in almost all proportions. T. A. Henke found
that the salt is hydrolyzed in aq. soln. G. Sailer observed that sodium thiosulphatoplatinite
is ultimately formed by the action of sodium hyposulphite.
W. Peters observed that the dehydrated salt takes up dry ammonia to form
sodium hexamminoctdoroplatinate, Na2PtCl6.6NH3, and that this ammine, in
vacuo, forms sodium pentamminochloroplatinate, Na2PtCl6.5NH3. Sodium
chloroplatinate also unites with methylamine to form sodium dodeciesmethylaminechloroplatinate,
Na2PtCl6.12CH3NH2 ; and with dimethylamine to form
sodium sexiesdimethylaminecnloroplatinate, Na2PtCl6.6 (CH3) 2N H. A. von