A Comprehensive Treatise on Inorganic and Theoretical Chemistry

PLATINUM 215
by exposure to air ; and H. St. C. Deville found that the lead of alloys with only
a small proportion of platinum slowly passes into carbonate. F. Doerinckel
showed that the grey, freshly fractured surfaces of alloys with 5 to 30 per cent, of
platinum oxidize rapidly on exposure to air ; the alloy with 2*5 per cent, of platinum
oxidizes rapidly on exposure to air ; the alloy with 2-5 per cent, of platinum oxidizes
more rapidly than lead ; air acts very slowly on alloys with 40 to 5O per cent, of
platinum, and not at all on alloys with more platinum. A. F. Gehlen found that
when the alloys are heated to redness in air, only part of the lead separates from
the platinum ; and that the separation continues only so long as the alloy remains
fusible ; the subject was studied by H. St. C. Deville and H. Debray. A. Bauer
and P. von Mertens showed that sulphuric acid decomposes an alloy with
IO per cent, of platinum slowly and incompletely ; and an alloy with 2 per cent,
of platinum suddenly and completely at 260° to 280°. According to A. von der
Ropp, nitric acid attacks all alloys with up to 50 per cent, of lead rather rapidly,
and the attack with alloys containing more platinum was found by F. Doerinckel
to be slower. H. Senn discussed the residues, and H. Debray, the explosive residues
—vide zinc. Some platinum passes into soln. along with the lead. C. Winkler
found that with alloys containing [Pb] per cent, of lead, [Pt] per cent, of platinum
passes into soln. :
Sp. gr. HNO3
[l>b]
I Pt]
9O-2O
719
1-398 1-298 1-09
98-6O
21-33
90-46
9-09
98-64
17-80
88-75
8-33
98-88
22-50
L. Hackspill prepared a platinum-thallium-lead alloy by dissolving lead in the
platinum-thallium alloy.
According to J. J. Berzelius, 14 a platinum crucible in which preparations of
vanadium have been frequently ignited becomes covered with a thin film of a
platinum-vanadium alloy, without altering its colour or lustre. When heated in
air, a film of fused vanadic acid is formed which prevents the further oxidation of
the alloyed vanadium.
R. Karlen 1{ * prepared some platinum-tantalum alloys in an electric furnace
in vacuo. Alloys with 1 to 2 per cent, of tantalum can be rolled below redness.
The addition of 1 per cent, of tantalum increases the hardness of platinum 25 to
30 per cent. ; and 2 per cent, of tantalum augments the hardness nearly 40 per cent.
According to M. G. Korsunsky, solid soln. are formed. The alloys are not altered
by air at a high temp., or by sulphuric, hydrochloric, nitric, or hydrofluoric acid,
or by a cone. soln. of potash-lye. Fused potassium
hydrosulphate has no action ; and fused sodium or
potassium carbonate has only a very feeble action.
The alloys are also attacked by aqua regia.
C 1 . Barus 16 prepared platinum-chromium alloys
by melting a mixture of the two metals in an oxyhydrogen
furnace. W. Guertler made some observations
on these alloys. M. G. Korsunsky said that
solid soln. are formed. C. Barus measured the electrical
resistance of the alloys. L. Muller determined
the liquidus curve of some platinum-chromium
alloys, and the results are summarized in Fig. 55.
V. A. Nemiloff studied the hardness, conductivity,
etc., of the alloys, and observed evidence of the
formation of platinum hemichromide, Pt2Cr, and
of platinum chromide, PtCr, but not on the thermal
diagram, which shows only solid soln. E. Friederich and A. Kussmann detected
a compound platinum trichromide, PtCr3, in the alloy, and they studied the
ferromagnetism of the alloys. Measurements of the electrical resistance were also
made. E. Friederich found that the alloys with 2 to 15 per cent, of chromium
2400
2200
2000
y*
y235 1° I
IHOO
1/777*
1600
nils
r
^r 675°
0 20 40 60 80
Atomic per cent. Cr or W
Fia. 55. Tlie Liquidus Curves
of Alloys of Platinum with
Chromium and Tungsten.