A Comprehensive Treatise on Inorganic and Theoretical Chemistry

PLATINUM 397
product is then washed with 80 per cent, alcohol to remove the carbon disulphide,
rubbed to a pasty mass, and boiled with a large proportion of water. The product
is then washed with water until free from chlorides ; pressed between bibulous
paper ; and dried in vacuo over sulphuric acid at a temp, below 125°. J. J. Berzelius
treated a platinic salt with hydrogen sulphide, or an alkali sulphide, washed the
precipitate with boiling water, and dried ix, in vacuo ; U. Antony and A. Liueehesi,
passed hydrogen sulphide through a 3 per cent. soln. of hydrochloroplatinic acid
at 90°—if the temp, is below 90°, sulphoplatinates are formed—washed the produet
in an atm. of hydrogen sulphide and dried it at 70° to 80° until the weight was
constant. R. Schneider obtained platinic sulphide by exposing moist sodium
diplatinous hexasulphoplatinatc or platinous tetrahydrohexasulphoplatinate to
atm. air as indicated above.
Platinic sulphide is a dark brown, steel-grey, or black powder. L. Thomassen
found that the X-radiogram corresponds with a trigonal lattice having a ==3-537 A.,
c, =5019 A., and a : c=l : 1-419. F. A. Bannister gave a=3-54 A., and c=5-02 A.
The sp. gr., according to K. Davy, is 3-5. R. Schneider found this datum is too low,
and gave 5*27 for the sp. gr. This is still too low for F. A. Bannister gave 7-80 ;
and W. Biltz and R. Juza gave 7-66, and 33*9 for the mol. vol. E. Davy said that
the sulphide does not fuse when heated. R. Bottger found that the thermal decom­
position begins between 225° and 250°, and, according
to J. .T. Berzelius, an atom of sulphur is first
given off and platinous sulphide is formed. W. Biltz
and R. Juza measured the vap. press, of the sulphur
and obtained the isothermal curves indicated in
Fig. 94. The heat of formation of the disulphide
from the solid monosulphide and solid rhombic
sulphur is 5 CaIs. Only the di- and monosulphides
were observed. According to R. Schneider, when
the disulphide is heated in air, it glows like tinder,
leaving behind spongy platinum. E. Davy said
that the disulphide is a non-conductor of electricity.
W. Skey discussed the behaviour of the disulphide
as a cathode in electrolyses. R. Bottger said that
the sulphide is not decomposed by hydrogen at
ordinary temp. E. Pollacci said that platinic sulphide
readily oxidizes in air ; E. Davy also observed
that some preparations are not decomposed by air
or water at ordinary temp., and P. de Clermont and
J. Frommel added that boiling water has no action ;
but J. J. Berzelius' preparation when moist was
400
350
a" 300
observed to produce sulphuric-acid on exposure to air, and to char paper on which
it rested. J. J. Berzelius' preparation is much more sensitive to chemical reagents
than is the case with the other preparations. L. R. von Fellenberg showed that
at a dull red-heat, chlorine decomposes platinic sulphide producing platinum and
sulphur chloride. R. Bottger observed that boiling cone, sulphuric, hydrochloric
or nitric acid of sp. gr. 1-2 has no action on the sulphide ; and E. Davy, and
R. Schneider added that of all the acids tried, hot aqua regia alone exerts a slight
action on this compound. J. J. Berzelius' preparation was observed to be rapidly
decomposed by aqua regia, and to be slowly and completely dissolved by fuming
nitric acid. A. Guerout found that sulphurous acid has no perceptible action on
the compound.
According to J. J. Berzelius, when hydrogen sulphide is passed over
precipitated, black platinic sulphide, the compound acquires a reddish-brown
colour by absorption of gas, but on exposure to air, the gas is given off and the
black colour is restored. E. von Meyer also indicated that the pale brown precipitate
obtained by hydrogen sulphide with hot soln. of potassium chloroplatinate is eine
1
8
250
,20O
750
50
'.
697°
657°
676°
- —
^^-J
0 100
20 40 60 80
Concentration PtS
Via. 94.—Tho Isothermal IMssociation
of 1'la.tmum 1 ^sulphide.