A Comprehensive Treatise on Inorganic and Theoretical Chemistry

198 INORGANIC AND THEORETICAL CHEMISTRY
solid soln. of silver in platinum ; and A +-B, a mixture of the two solid soln. Observations
on the subject were made by W. Guertler, G. Natta, K. Bornemann, and
E. Janecke. CH. Johansson and J. O. Linde's results are summarized in Fig. 34,
where the Greek letters refer to solid soln.
According to J. F. Thompson and E. H. Miller, under the microscope, the
alloy with 10-39 per cent, of platinum consists of crystals set in a non-composite
ground mass. On cooling from 1200°, a development of heat was observed at
1045° to 1050°, and a much larger development at 1000°. The alloy containing
20*59 per cent, platinum, when cooled from 1100°, developed heat at 1085° and
possibly also at 995°. The microstructure showed large, white dendrites in a
non-composite ground mass. The alloy containing 31*46 per cent, platinum, on
cooling from 1300°, gave marked but irregular developments of heat between
1170° and 1100°. The structure consisted of grey crystals in a dark ground mass.
The alloy containing 37-89 per cent, platinum resembled the 31-46 per cent, alloy
in structure, but gave sharp developments of heat at 1240° and 1170°. The alloy
containing 57-05 per cent, platinum also resembled the 31*46 per cent, alloy in
structure ; on cooling from 1400°, it gave developments of heat at 1240°, 1180°,
and 1090°. K. Gebhard and H. J. Wiester studied the recrystallization of the
platinum-silver alloys. CH. Johansson and J. O. Linde's results for the lattice
constant of the alloys are summarized in Fig. 35. The results for the dotted lines
20 40 80 80 100
Atomic per cent, of platinum
KiO. 35.—The Lattice Constants
of the Platinum-Silver Alloys.
i
-S^- 03
280\
240
200
160
720
80
40
^ \
nQ
44,
Sf
oS95F
•Tenacity
> NA
\
SZ d
0
0 20 40 60 80 100
Atomic per cent.. Platinum
FIG. 36. The Hardness and Tenacity of Platinum-
Silver Alloys.
refer to solid soln. The alloys for up to about 30 per cent, platinum were quenched
from 75()° to 850°, and those above 50 at. per cent, platinum were quenched from
1150°. The X-radiograms were studied by J. Weerts. The sp. gr. referred to
water at 4° is :
Platinum
Sp. gr.
0
10-61
10-39
11-17
20-59
11-8O
W. Lie wis gave for the sp. gr. of alloys with
Silver
Sp. gr.
5O
13-535
6G-7
12-452
75
11-790
31-46
12-57
37-89
13*19
87-5
10-867
57-05 per cent.
14-25
100 per cent.
10-980
W. Biltz and F. Weibka studied the at. vol. J. P. J. d'Arcet observed that the
alloys of platinum with silver are less white, less malleable, and less hard than
silver, and when quietly fused, an alloy richer in platinum collects at the bottom.
C. Winkler obtained analogous results. J. F. Thompson and E. H. Miller observed
that alloys with over 3O per cent, of platinum are much harder than those with a
lower proportion of platinum, and the hardness increases as the proportion of
platinum increases ; and F. Doerinckel added that alloys with up to 30 per cent,
of platinum are scarcely harder than their components, but beyond that point
the hardness increases, and an alloy with 70 per cent, of platinum is rather harder