A Comprehensive Treatise on Inorganic and Theoretical Chemistry

PLATINUM 395
absence of air, the soln. contains potassium sulphoplatinite and potassium hydroxide,
whilst the undissolved residue is a mixture of platinum, tin, and potassium hydro-
SUlphoplatinite, K2PtS2-2H2PtS2. When the soln. is exposed to the air, the
potassium sulphoplatinite is partially oxidized according to the equation
3K2PtS2 4-3O=K2PtO3+2K2PtS3, and when this oxidized solution is treated with
hydrochloric acid, platinic sulphide is precipitated. When potassium sulphoplatinite
is treated with dil. hydrochloric acid in absence of air, sulphoplatinous
acid, H2PtS2, is formed "which, in the presence of air, is oxidized to water and
platinic sulphide. By fusing a mixture of platinous oxystannate, Pt2Sn6O10,
with twice its weight of sulphur, and washing the product, there remains a
black powder consisting of acicular crystals of platinous sulphostannate,
4PtS.SnS2, which is not attacked by boiling nitric or hydrochloric acid, but is
decomposed by boiling aqua regia. The salt is stable in air, but when heated, it is
completely decomposed into platinum and platinous stannate. K. Schneider
observed that when 2Na2S.2PtS.PtS2 is decomposed by boiling water, sodium
sulphoplatinite, Na2S.PtS, is formed; and he obtained sodium hydrosulphoplatinite,
2H2S.Na2S.3PtS, or Na2PtS2.2H2PtS, from the red liquid obtained
in the preparation of Na2S.PtS.2PtS2 with absolute alcohol, and washing the
precipitate with dil. alcohol (2 : 1), and finally with alcohol. The brown product
is converted into platinic sulphide and sodium carbonate on exposure to air. Itforms
a brown soln. with water from which alcohol precipitates the original salt ;
and when treated with hydrochloric acid, the sodium is extracted : 2H2PtS2.-
Na2PtS2-t-2HCl=2NaClH-3H2PtS2.
The analyses of the products obtained by L. N. Vauquelin—vide supra—
approximate to Pt5S6, and R. Schneider considers that this salt is actually produced.
He considers it to be platinous tetritasulphoplatinate, (PtS)4PtS2, or
Pt4(PtS6), platinous hexasulphoplatinate, and said that it is best prepared by fusing
together for 8 to 10 minutes, at a bright red heat, a mixture of 2 parts of ammonium
chloroplatinate, and 3 parts each of sulphur, and dry sodium carbonate. It forms
steel-grey needles, having a metallic aspect and belonging to the rhombic system.
It is unchanged in the air when dry, but if the moist substance be heated on the
water-bath it absorbs oxygen, and then contains sulphuric acid. Heated in carbon
dioxide it loses one-sixth of its sulphur, platinous sulphide remaining ; heated in
the air, the sulphur is entirely burned away. When strongly heated in a stream of
hydrogen it is entirely reduced. It is unacted upon by boiling hydrochloric or
nitric acid, but is slowly attacked by boiling aqua regia. Fused with nitre, it is
easily and completely decomposed. R. Schneider prepared platinous dihydrohexasulphoplatinate,
Pt3H2(PtS6), by the action of warm hydrochloric acid on
K2S.3PtS.PtS2 ; it readily oxidizes in air to form water and platinum sesquisulphide
; if the sodium salt 2Na2S.2PtS.PtS2 be similarly treated in the cold,
reddish-brown platinous tetrahydrohexasulphide, Pt2H4(PtS6), is formed.
R. Schneider prepared potassium triplatinous hexasulphoplatinate, K2Pt3(PtS6),
by melting at a high temp, an intimate mixture of 1 to 2 parts of spongy platinum
with 6 parts each of sulphur and potassium carbonate. The bluish-grey plates of
the salt can be separated by levigation, washed, and dried at 120°. The sp. gr.
is 6-4:4 at 15°. The salt is stable in air at ordinary temp., but when heated, it glows
like tinder giving off sulphurous oxides, and forming potassium sulphate and
platinum. It is attacked when heated in hydrogen chloride forming hydrogen
sulphide ; dil. hydrochloric acid forms platinous dihydrohexasulphoplatinate ;
when heated in hydrogen, hydrogen sulphide is formed. R. Schneider prepared
sodium diplatinous hexasulphoplatinate, Pt2Na4(PtS6), by melting together a
mixture of 1 part of platinum sponge with 6 to 9 parts each of dry sodium carbonate
and sulphur, and washing the product with water. The pale copper-red,
rhombic needles are coloured brown and black by exposure to air, or aerated
water ; they are decomposed by boiling water ; and sodium sulphide reacts :
Na2S-I-PtS+2H2O =H2PtS2+2NaOH. Dil. hydrochloric acid reacts as indicated