A Comprehensive Treatise on Inorganic and Theoretical Chemistry

224 INOKGANIC AND THEORETICAL CHEMISTRY
platinum. G. Tammann and H. J. Rocha observed that alloys -with less than
30 per cent, of palladium have a granular structure and those with more than
40 percent, of palladium have a dendritic structure. E. R. Thews discussed some
uses of the alloys. There appears to be a continuous series of solid soln. T. Barth
and G. Liunde studied the lattice constant of the alloys. G. Tammann and
H. J. Rocha observed that the maximum hardness of the alloys occurs at 10 to
20 per cent, of palladium when the alloys are quenched from 1400°, at 30 per cent.
when they are quenched from 1200°, and at 4O per cent., when they are
annealed at 600° for 12 hrs.—vide Table IV. Quenched alloys, except that
containing 38 per cent, of palladium, are all harder than annealed alloys.
F. Goldberger and O. Kienberger, and N. S. Kurnakoff studied the streak as an
indication of the composition of the alloy. W. Geibel obtained the results indicated
in Fig. 69 for the tensile strength in kilograms for a wire of diameter 1 mm. The
0 20 40 60 80 100
Atom per cent. Platinum
FiG. 09. The Tensile Strength
of the Palladium-Platinum
Alloys.
SOO Wi
20 40 60 80 100
Atom per cent. Platinum
Fio. 70.—The Kleetrical Properties of the
Platinum-Palladium Alloys.
subject was studied by E. M. Wise and J. T. Eash. According to F. E. Carter,
palladium does not harden platinum in the same way as do the other metals of the
group, and a whole series of homogeneous alloys can be formed which are easily
workable. The alloy of maximum hardness has about 25 per cent, of palladium.
The Brinell hardness, Z/, Ericson\s ductility test, and the electrical resistance,
R ohms per million ft., are as follows :
Palladium
„ i Hard
t Annealed
Ductility
R
IO
16O
85
111
13O
2O
17O
95
11-5
160
25
175
1OO
81
170
75 per cent.
15«
8O
9-5
145
The values for the electrical conductivity XlO -4 at 0° and its temp, coeff. between
0° and 160° are indicated in Fig. 70; and the thermoelectric force of the alloys
against platinum, expressed in millivolts, are summarized in Fig. 71. C. Barus
made observations on the electrical resistance of the alloys. L. Holborn and
A. IJ. Day found the thermoelectric force, E millivolts, of the couples :
Pt : PtI
9O : IO
IO : 9O
. —185°
. —Oil
0°
O
O
200°
0-62
— 0-31
400°
1-48
— 0-35
600°
2-42
012
5O
165
9O
7-9
180
800°
3-35
1-2
1000°
4-78
4-2
1200
5-25
Observations were made by A. W. Smith, R. von D. Wegner, and J. Monheim.
E. Vogt studied the magnetic properties of the platinum-palladium alloys ; and
Y. Shimizu gave for the magnetic susceptibilities, ^, in mass units :
Platinum
X X 10«
lOO-OO 95-96
108 112
82-24
1-32
75-24
1-41
67-38
1-60
5009
219
G. Borelius studied the diffusion of hydrogen in the alloy.
41-39
2-55
11-90
4-25
0 per cent.
5-20