A Comprehensive Treatise on Inorganic and Theoretical Chemistry

236 INORGANIC AND THEORETICAL, CHEMISTRY
acid, and that the rate of dissolution is catalytically increased in the presence of
a trace of platinous chloride, or of a soln. of platinous hydroxide in hydrochloric
acid. J. W. Dobereiner found that the monoxide dissolves in sulphurous acid,
but not in the other oxyacids ; and L. Wohler, that it is a little soluble in aqua
regia. L. F. Nilson obtained platinous nitrosyl oxides, (Pt.O.ON : ON.OH)20 ;
and also Pt3H4(N02)80.2H20 ; and J. Lang, H2Pt(N02)4. F. Mylius and F. Forster
obtained evidence indicating the formation of platinous carbonyl oxide, or platinous
oxycarbonyl, [Pt(CO)O], or CO.PtO. J. W. Dobereiner observed that formic
acid reduces the oxide to platinum black with a violent evolution of carbon dioxide ;
and that it takes up some oxalic acid from a boiling aq. soln. F. D. Aguirreche
hydrogenized salicylic acid using platinum oxide as catalyst.
As indicated above, L. Wohler showed that the oxygen associated with ordinary
platinum black is in part present as hydrated platinous oxide, Pt0.nH20.
J. J. Berzelius prepared it by gently warming platinous chloride with a soln. of
potassium hydroxide, and washing the precipitate. Part of the platinum monoxide
is dissolved by the alkali-lye which is in consequence coloured green, and it can be
recovered from the soln. by the addition of sulphuric acid. J. von Liebig added
that the hydrated oxide so obtained is contaminated with chloride, and if too much
potash-lye be present, the precipitate redissolves. E. von Meyer recommended
using a small excess of potash-lye, and drying the carefully-washed product at
105° to 110°. L. N. Vauquelin observed that if soda-lye be employed for the precipitation,
the precipitated hydrate is contaminated with soda which cannot be
removed by washing. J. Thomsen boiled a soln. of a mol of potassium chloroplatinate
in 30O mols of water with 2 mols of a dil. soln. of sodium hydroxide, and
washed the black precipitate first by decantation, and afterwards on a
filter— L. Mond and co-workers observed that the product is always contaminated
with chlorides, and L. Wohler, that it has a tendency to oxidize unless it is washed
in an atm. of an inert gas—say carbon dioxide—and dried in a desiccator first
filled with carbon dioxide, and afterwards evacuated. F. Martin, and L. Wohler
and F. Martin prepared the hydrated oxide by dropping a soln. of sodium carbonate
into one of potassium chloroplatinite—or of a soln. of hydrochloroplatinie acid
which has been treated with sulphur dioxide—and boiling the liquid in an atm. of
carbon dioxide until the black, hydrated oxide is precipitated ; the product is again
boiled with a soln. of sodium carbonate to remove the chlorides from the precipitate
which is then washed and dried as before.
The hydrated monoxide is a black powder which, according to L. Wohler, has
the composition of a tnouohydrate, or platinous hydroxide, Pt(OH)2, if it has been
dried for a sufficient length of time at 100°. L. Wohler and F. Martin considered
this hydrate to be platinous acid, H2PtO2, which forms salts, platinites. J. Thomsen
obtained the hydroxide by boiling a dil. aq. soln. of potassium chloroplatinite with
the proper proportion of soda-lye ; and L. Wohler and W. Frey, by boiling in an
atm. of carbon dioxide a soln. of potassium chloroplatinite mixed with the calculated
quantity of sodium hydroxide, boiling the precipitate several days in water,
and drying in an atm. of carbon dioxide for 48 hrs. at 120° to 150°. The precipitate
obtained at ordinary temp, approximates to the dihydrate, Pt0.2H2O.
J. J. Berzelius stated that when potassium hydroxide is fused in a platinum vessel,
out of contact with air, potassium platinite is formed, and it yields a dark soln.
in water. Likewise when platinous chloride is decomposed by potash-lye, a dark
green soln. of potassium platinite is formed. L. N. Vauquelin obtained what was
regarded as sodium platinite by decomposing a soln. of platinous chloride with an
excess of soda-lye.
Kalle and Co. prepared colloidal platinous hydroxide by mixing a dil. soln.
of sodium protalbinate and sodium carbonate with a dil. soln. of platinous chloride
and sodium acetate, and warming the mixture on a water-bath at 70° to 80°.
The dialyzed soln. on evaporation furnishes dark green plates which form a colloidal
soln. with water. A. Skita and W. A. Meyer used gum arabic as protective colloid.