A Comprehensive Treatise on Inorganic and Theoretical Chemistry

PLATINUM 209
of a portion of the surface of the amalgam by air outside the drop, and deoxidation
by electrolysis in the interior of the drop. G. A. Hulett calculated that mercury
which distils from an amalgam saturated with platinum at 200° contains 1 part
of platinum in a hundred million parts of mercury. By distilling 6-70 grms. of
mercury at 200° and 25 mm. press., the mercury would occupy 39,54O litres, and the
0*067 mgrm. of platinum in this vol. would show a partial press, of 0-0626 mm., if
platinum be monatomic in the state of vapour. This datum represents the vap.
press, of platinum at 200° ; and it follows that each c.c. of space or gas in equilibrium
with platinum at 200°, contains 5-3 XlO 9 atoms of platinum. C. Hockin and
H. A. Taylor found that the e.m.f. of platinum amalgam against amalgamated
zinc in dil. sulphuric acid, is 1*363 to 1*169 volt for liquid amalgam, 1-168 volt for
solid amalgam, and 1-086 for amalgam with only a trace of platinum. Hydrogen
is absorbed by even dilute amalgams, and G. Meyer studied the cathodic polarization
of the amalgam.
According to H. Moissan, when platinum amalgam is shaken with water for
15 seconds or less, it forms an emulsion of a buttery consistency and having five
times the vol. of the original amalgam. The product is stable and not affected
by being heated to 100° or cooled to —80°. A section made at the latter temp,
reveals small drops of water disseminated throughout the amalgam, giving the
latter a cellular appearance. When exposed in a vacuum, it diminishes in vol., a
little water and a small quantity of gas separating. The emulsion is also produced
by shaking 2 c.c. of pure mercury with 12 c.c. of water to which some drops of a
IO per cent, platinic chloride soln. have been added, and when platinum amalgam
is shaken with water, similarly treated, the increase in vol. is greater than with
pure water. Platinum amalgam emulsifies similarly when shaken with sulphuric
acid, aqueous ammonia, aq. or ammoniacal ammonium chloride soln., sodium
chloride soln., glycerol, acetone, anhydrous alcohol, ether, oil of turpentine, carbon
tetrachloride, or chloroform, and forms stable emulsions. Benzene is inactive.
Platinum amalgam, to which sodium has been added, also increases in volume
and emulsifies when shaken with water. P. Lebeau added that the property of
forming emulsions is not exhibited by the other metals of the platinum group,
and with platinum amalgam, the property is shown when only 0-038 per cent,
of platinum is present. The platinum amalgam loses its property by admixture
with amalgams of zinc, calcium, lead, or tin. The volume of the mass formed is
dependent not only on the nature of the liquid, but also on the state of the platinum
from which the amalgam was made, being much greater when the latter is finelydivided,
although even in this case the effect is diminished if the metal be strongly
heated before the amalgam is made. Microscopic examination of sections cut from
the mass, obtained by shaking platinum amalgam with a soln. of gelatin and then
cooling to the f.p. of mercury, show that it had a structure similar to that of soap
lather, so that it is probably due entirely to surface tension. G. Michaud observed
that a trace of platinum in mercury prevents the formation of ammonium amalgam
from sodium amalgam and a soln. of ammonium chloride. N. Tarugi found that
cone, nitric acid dissolves so much the more platinum the greater the proportion
of mercury. Thus, from a mixture containing 4-64 per cent, of platinum and
95*35 of mercury, nitric acid dissolves the whole of the platinum ; as the percentage
of platinum present increases, the proportion of the total amount dissolved by the
acid diminishes, whilst the proportion of mercury dissolved decreases from 99 per
cent, in a mixture of 91*11 parts of mercury and 8*88 of platinum to zero for a mixture
of 17-02 per cent, of mercury with 82*97 of platinum. J. W. Smith studied
the adsorption of water vapour and benzene vapour by amalgamated platinum.
F. Glaser discussed the solubility of platinum amalgam in a soln. of potassium
cyanide—vide supra. J. W. Mallet prepared platinum-silver-mercury alloys by
the action of silver amalgam on platinum.
C. and A. Tissier® prepared platinum-aluminium alloys. O. Brunck observed
that aluminium dissolves platinum very slowly ; 1 part of platinum required 2 hrs.
VOL. xvi.
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