A Comprehensive Treatise on Inorganic and Theoretical Chemistry

20°
Oil
O
PLATIlTOM 145
of oxygen, respectively, at 25° and 110°. A. F. Benton obtained as an average at
25° and 1 atm. press., an absorption of 20*4 vols. The rates of approach to
equilibrium at different temp., 0, and press., of two samples are indicated in Fig. 26.
P. Grandadam, and P. Laffitte and P. Grandadam studied the absorption of
oxygen by platinum sponge or platinum black when heated in oxygen under press.
A. Sieverts observed that 30-45 grms. of platinum wire heated in vacuo gave
O2
Time
200°
O-11
35
400°
014
65
600°
0-18
8O
800°
0-18
96
1000°
0-29 c.c.
1IO minutes
C. Paal and C. Amberger observed that colloidal platinum readily takes up oxygen
from the air, and the elementary hydrosol is not regenerated when the sol is treated
with hydrogen.
W. W. Randall found that oxygen does not diffuse through heated platinum ;
but. A. Li. Ferguson and G. Dubpernell discussed the transfer of electrolytic oxygen
770i
Fm. 26.- -THe Rate of Approach, to
Kquilibrium.
IUVl
1 90
°- 80
^ 70
•I 60
^ 50
£ 4O
S 30
1~
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100 200° 300" 400° 500° 600° 70(
FIG. 27. The Evolution of Oxygen from
Platinum 13lack at different Temperatures.
through the metal. J. Thomsen observed that the affinity of platinum for oxygen
is small. According to I. Langmuir, a platinum filament at temperatures above
1600° K. gradually causes the removal of oxygen at low pressures. The oxygen
combines with the platinum atoms as fast as they evaporate from the filament,
and forms the dioxide, which collects on the bulb as a brown deposit. G. B. Taylor
and co-workers gave approximately 65,000 cals. for the heat of adsorption ;
and E. B. Maxted and N. J. Hassid, 60,0OO cals. per gram mol. of oxygen.
H. St. C. Deville and H. Debray said that platinum is never found as a mineral
associated with oxygen ; T. WiIm noted that platinum obtained by the ignition
of the ammines or ammonium salts at a red-heat in air is not oxidized ; and no
sign of oxidation occurs when platinum sponge is heated to redness in air.
H. Ie Chatelier added that under suitable conditions of temp, or press., the metal
may be oxidized. Y. Okayama studied the subject. W. Skey noted that the
surface of the metal exposed to air liberates iodine from a dil. soln. of potassium
iodide in dil. sulphuric acid ; J. L. Smith also noted the condensation of air on the
surfaces of platinum crucibles. According to W. Skey, platinum whieh has been
" in contact for a short time with distilled water, ammoniated water, or with
aq. soln. of the alkalies, carbonates or chlorides," will not amalgamate. Acids,
on heating to about 200°, restore the amalgamable condition ; and G. Mcissner,
H. Humpelt, and B. Dessau showed that a film can be detected optically on
platinum heated in air or oxygen—vide supra, the volatilization of platinum.
H. Damianovich noted a change in the microstructure of platinum after exposure
to the electric discharge in oxygen. A. Fery studied the effect of adsorbed oxygen
on the electrical resistance.
VOL,, xvi. i*
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