A Comprehensive Treatise on Inorganic and Theoretical Chemistry

168 INORGANIC AND THEORETICAL, CHEMISTRY
to assume the colloidal state. A. Trillat found that a trace of platinum favours
the catalytic activity of copper. R. Engel noted the favourable action of platinum
on the dissolution of copper in hydrochloric acid ; and W. Nernst, on the dissolution
of copper in a soln. of potassium cyanide. A platinum plate is "without
action on the hydrosol of silver. F. Vies and M. Get studied the effect of platinum
on silver sols. F. C. Carter observed that platinum absorbs calcium when heated
electrically in lime ; M. Ballo, a trace of platinum favours the reducing action of
magnesium ; N. A. E. Millon, the dissolution of zinc in acids ; Ti. Schonn, the
dissolution of cadmium in nitric acid ; and C. Barreswil, and N. A. E. Millon,
that the presence of traces of platinum favours the evaporation of mercury ; but
F. C. Carter observed no tendency to amalgamation below 200°. M. Volmer and
A. Weber studied the wetting of platinum by mercury ; Y. Okayama, and
A. I. Leipunsky, the oxidation of mercury by oxygen in the presence of a heated
platinum filament. W. R. E. Hodgkinson and F. K. S. Lowndes observed no
attack by mercury vapour on the red-hot wire ; but T. Ihmori found that an
adsorption of mercury vapour by platinum black occurs such that at 17°, a specimen
of platinum black, 0-3 grm., increased in weight 0*0021 grm. in 5 hrs. Platinum
foil showed no increase in weight. O. Loew found that with hydrogen amalgam,
in water, heat is developed ; and L. Cailletet, that with ammonium amalgam, or
sodium amalgam, under water, platinum is amalgamated. E. B. Maxted noted
the adsorption of lead or mercury which acts as a catalytic poison on platinum.
L. Schonn noted that platinum favours the dissolution of tin in nitric acid ;
N. A. E. Millon, the dissolution of iron in acids; and Tt. Varenne, the depassivation
of iron in cone, nitric acid. W. G. Imhoff studied the deleterious action of zinc
on platinum. J. L. Gay Liussac and TJ. J. Thenard found that platinum is oxidized
when heated with potassium peroxide ; and W. L. Dudley, T. Poleck, Li. Quennessen,
and E. Leidie and Li. Quennessen found that the metal is also attacked
when heated with sodium dioxide. W. Dittmar, and L. Troost said that platinum
is not attacked by lithium oxide in the absence of air at a white-heat ; but R. Rieke
and K. Endell observed that the metal is attacked in the preparation of molten
lithium silicates in platinum crucibles. G. Brugelmann observed that the Sp. gr.
and crystal form of barium oxide made in platinum and in clay crucibles are
different. According to P. Nicolardot and C. Chatelot, at 825°, barium oxide is
much less corrosive than the alkali hydroxides. O. Sackur found that the metal
is perceptibly attacked by barium oxide and strontium oxide at an elevated
temp., and H. Rose noted that it is attacked likewise by manganese dioxide ;
and J. J. Berzelius, and G. Bischof, by molten potassium hydroxide. W. Dittmar
observed that there is no attack by alkali hydroxides at a red-heat, when air is
excluded, but if air has access, peroxides are formed and the metal is attacked.
F. C. Carter, and M. Ie Blanc and L. Bergmann observed no attack by sodium
hydroxide at 400°, but the metal is corroded at temp, exceeding 700°. T. Gross
observed that in the electrolysis of fused potassium hydroxide, or of potassium
carbonate mixed with a little nitrate, in a platinum crucible, at a yellow heat,
with an alternating current of 50 cycles per second, 120 volts, and 35 amps., the
metal is attacked, and needles resembling graphite are formed on and in the fused
mass. J. J. Berzelius found that platinum is attacked by molten lithium hydroxide,
and the subject was studied by W. Dittmar, L. Troost, Tt. N. Vauquelin,
P. Nicolardot and C. Chatelot, H. A. von Vogel, and L. Kralovanszky. According
to W. Skey, platinum is so affected by soln. of the fixed alkalies that it can no
longer be amalgamated until the metal has been treated with acids. It was supposed
that a film of oxide is formed on the metal. C. Marie observed that the
metal is oxidized by an aq. soln. of potassium permanganate and sodium hydroxide.
According to P. Nicolardot and C. Chatelot, platinum crucibles undergo marked
corrosion when sodium hydroxide or potassium hydroxide is fused in them, and
the crucibles are subsequently washed, first with water and then with dilute acid.
New crucibles resist better than old crucibles, and the presence of iridium rather