A Comprehensive Treatise on Inorganic and Theoretical Chemistry

396 INORGANIC AND THEORETICAL, CHEMISTRY
above forming platinous tetrahydrohexasulphoplatinate. The fresh precipitate,
in contact with neutral silver, zinc, cadmium, thallous, ferrous, and manganese
salts, exchanges sodium for the corresponding metal, but not so with salts of the
'alkaline earths.
R. Schneider observed that if freshly-prepared sodium diplatinous hexasulphoplatinate
is treated with a dil. soln. of copper sulphate, with exclusion of air, there
is formed copper diplatinous hexasulphoplatinate, Pt2Cu2(PtS6), in bluish-grey
pseudomorphs of the sodium salt. The copper salt is stable in air ; it glows like
tinder when heated leaving a residue of platinum and of copper oxide. Boiling
nitric or hydrochloric acid extracts the copper ; and the salt is partially decomposed
by boiling aqua regia. R. Schneider obtained silver diplatinous hexasulphoplatinate,
Pt2Ag4(PtS6), by the action of a soln. of silver nitrate on the corresponding
sodium salt. If heated in air or in hydrogen, a mixture of silver and
platinum is formed. Hydrochloric acid has no perceptible action ; warm nitric
acid extracts the silver ; and hot aqua regia dissolves some platinum and leaves a
residue of silver chloride and platinic sulphide. R. Schneider prepared zinc
diplatinous hexasulphoplatinate, Pt2Zn2(PtS6), cadmium diplatinous hexasulphoplatinate,
Pt2Cd2(PtS6) ; thallous platinic hexasulphoplatinate* PtTI4(PtS6) ;
stannic diplatinous hexasulphoplatinate, Pt2Sn(PtS6) ; lead diplatinous hexasulphoplatinate;
Pt2Pb2(PtS6) ; manganese diplatinous hexasulphoplatinate,
Pt2Mn2(PtS6) ; and ferrous diplatinous hexasulphoplatinate, Pt2Fe2(PtS6).
R. Schneider 2 prepared platinum hemitrisulphide, or platinum sesquisulphide,
Pt2S3, which he considered to be platinous sulphoplatinate, PtS.PtS2, or Pt(PtS3),
platinous trisulphoplatinatc, by the spontaneous oxidation of H2S.3PtS.PtS2 ;
or by the action of a dil. soln. of sodium chloroplatinate on sodium platinosic
sulphide, 2Na2S.2PtS.PtS2. The steel-grey powder has a sp. gr. of 5-52. When
moist, the powder absorbs oxygen from the air. It loses about 5 per cent, of water
at 120° ; and at a higher temp, it suddenly swells up and gives off more water ;
at a still higher temp., sulphur is sublimed. When roasted in air, it begins to glow
like tinder giving off sulphurous oxides, and finally leaving a residue of platinum
sponge. It is easily reduced in hydrogen ; it is not attacked by boiling nitric
or hydrochloric acid ; but it is slowly attacked by boiling aqua regia. If
Na2S.PtS.2PtS2 be suspended in water and treated with dil. hydrochloric acid,
there is formed unstable platinous hydrotrisulphoplatinate, PtH2(PtS3J2, or
PtS-H2S.2PtS2, which is readily decomposed on exposure to air, forming platinic
sulphide. R. Schneider observed that sodium platinous trisulphoplatinate,
PtNa2(PtS^)2, or PtS-Na2S.2PtS2, is formed when sodium diplatinous hexasulphoplatinate
is boiled with water. The brown, crystalline powder rapidly darkens
on exposure to air, and water, sodium carbonate, and platinic sulphide are formed ;
with dil. hydrochloric acid, platinous hydrotrisulphoplatinate is formed.
The mineral cooperite wag at first represented by Pt(As, S)2, then by PtS2,
and later by PtS {q.v.). E. Davy prepared platinic sulphide, or platinum disulphide,
PtS2, by heating to low redness a mixture of 2 parts of sulphur with 3 parts of
ammonium chloroplatinate in a glass tube closed with mercury, and stopping the
heating when the evolution of gas has ceased. R. Bottger said that the product
is contaminated with sulphur because the mixture has not been heated long enough.
W. Biltz and R. Juza, and H. G. Krall also prepared the disulphide from its components,
and by heating sulphur with platinic chloride. E. A. Geitner heated
hydrochloroplatinic acid decolourized by sulphur dioxide, to 200° in sealed tubes.
J. Persoz heated to whiteness a mixture of platinum with 2 parts of sodium carbonate
and 3 parts of sulphur, and washed the product with water ; the platinic
sulphide remains in long, aurora-red needles. L. Wohler and co-workers obtained it
by the action of hydrogen sulphide on platinic chloride, and by heating the product
with sulphur at 600°. R. Bottger prepared the sulphide by allowing a mixture of
1 part of dry platinic chloride, 4 parts of absolute alcohol, and 5 parts of carbon
disulphide to stand in a stoppered bottle for a week with occasional shaking. The