A Comprehensive Treatise on Inorganic and Theoretical Chemistry

PLATINUM 205
susceptibility, in Fig. 50. Y. Shimizu studied the effect of stress on the magnetic
susceptibility.
P. Johnson found that nitric acid dissolves not only gold but some platinum
from the alloys. K. W. Frohlich discussed the error involved in the determination
of platinum -when alloys with gold and silver are treated with hot sulphuric acid.
Some platinum passes into soln. J. Weineck observed that cone, sulphuric acid,
and molten potassium hydroxide with or without potassium nitrate, and molten
potassium hydrosulphate have no marked action on the alloy. F. Doerinckel found
that the alloys resist cold aqua regia very 1 WeIl ; soln. of potassium cyanide rapidly
attack alloys with a low proportion of platinum ; the action is slower with increasing
proportions of platinum ; and "when 6O per cent, of platinum is present, the attack
is slow with boiling soln. A.G. Norddeutsche Amnerie found that the alloys
dissolve anodically in hydrochloroauric acid ; and F. Haber found that 11 per
cent, hydrochloric acid, at the b.p., attacks platinum anodes as vigorously as a
36 per cent. soln. at ordinary temp. ; but an 8 per cent, soln., at the b.p., leaves
the platinum intact, and a soln. below 3O per cent, hydrochloric acid does not
attack the metal at ordinary temp. Li. Quennessen studied the attack by caustic
alkalies. P. Nicolardot and J. Boudet found that crucibles made with gold alloyed
with 12-5 to 25 per cent, of platinum are badly attacked during the electrolysis of
alkaline soln., and in the presence of sulphides, and sodium cyanide.
E. Janecke represented the ternary platinum-gold-copper alloys as a continuous
series of solid soln. ; and the platinum-gold-silver alloys as a series
of solid soln. with a gap, Fig. 51. E. Matthey noted the segregation of
2O 40 60 80 100
Atomic per cent, of platinum
Fio. 50. The Magnetic Susceptibility
of the .Platinum-Gold Alloys.
Ag Pt
Kio. 51. THe Ternary
System : Pt-Au-Ag.
both series of alloys. E. B. Craft and J. W. Harris said that the alloy with 67*5 to
7O per cent, of gold, 25 per cent, of silver, and 5 to 7-5 per cent, of platinum, is
harder than platinum ; and F. A. Bolley used the alloy 8 parts of platinum, 1 part
of silver, and 3 parts of gold for dental work. L. N. Vauquelin, and H. Debray
noted that nitric acid completely dissolves the alloy with 1 part of platinum,
IO parts of gold, and 30 parts or more of silver. A. von der Ropp noted that nitric
acid dissolves most of the silver and gold, but leaves some platinum alloy undissolved
; press, increased the solubility of the platinum. E. Matthey noted that
castings of the quaternary platinum-gold-silver-copper alloys are not homogeneous.
R. B. Graf used the 45 : 15 : 25 : 15-alloy for electric contacts. Ii. Nowack
studied the platillium-gold-zinc alloys. N. H. Furman studied an application of
the amalgam—gold-platinum-mercury alloy—in electrometric titrations.
According to M. Tarugi, 5 when platinum salts are heated with calcium carbide,
a platinum-calcium alloy is formed, and it is easily decomposed by water.
F. E. Carter said that when the platinum is melted under reducing conditions in a
lime-crucible, it takes up calcium to form an alloy. E. D. Clarke observed that a
platinum-barium alloy is formed by melting a mixture of the two elements in
the oxyhydrogen flame. The bronze-coloured alloy disintegrates to a reddish
powder in 24 hrs. A. Matthiessen found that in the electrolysis of molten barium
chloride with a platinum cathode, a yellow, brittle alloy is formed, and it is slowly