A Comprehensive Treatise on Inorganic and Theoretical Chemistry

PLATINUM 245
and, better still, potassium hydroxide dissolve the hydrate at ordinary temp.
IJ. Wohler found that the hydra ted dioxide accelerates the decomposition of hot
soln. of potassium permanganate, and when boiled with a cone. soln. of platinic
chloride in the presence of acetic acid, the hydrated dioxide is reduced to metal.
H. Kautsky and W. Baumeister studied the adsorption of the [Pt(OH)6]"-ions
by thorium hydroxide gel ; and A. Rosenheim, the action of platinic hydroxide
on tungstates.
B. Gerdes prepared platinic hexamminohydroxide, [Pt(NHg)6 (OH)4], by
boiling the chloride with an eq. quantity of silver oxide, and cooling the filtered
liquid. The white hexagonal plates are sparingly soluble in water ; the soln. has
an alkaline reaction ; it decomposes ammonium salts ; absorbs carbon dioxide
from the air to form a carbonate ; and forms salts with acids.
C. Gerhardt prepared platinic tetrahydroxydiammine, [Pt(NH3)2(OH)4], by
the action of ammonia on a boiling soln. of the corresponding nitrate, cooling
the liquid, washing the precipitate, and drying at 130°. The yellow, macrocrystalline
powder is not changed at 130° ; it decrepitates at a higher temp, losing water and
ammonia, and leaving platinum behind. It is scarcely soluble in water, but
soluble in hot, dil. acids ; boiling potash-lye does not dissolve or decompose the
compound. It was studied by W. Odling, O. Weltzien, H. Kolbe, C. Grimm, and
P. T. CIeve. B. E. Dixon prepared silver platinic hydroxytriamidodiamminohydroxide,
[Ag3{Pt(NH3)2(NH2)3(OH)}2](OH)3.
J. Jacobsen prepared platinic decahydroxyammine, [NH3Pt(OH)5J2, by
pouring an excess of ammonia into a soln. of dichloroplatinic acid. The liquid
turns a dark colour, and finally precipitates a brown, flocculent mass containing no
chlorine and resembling ferric hydroxide. Washed with boiling water until free
from ammonia and dried, this precipitate presents a conchoidal structure. If
dried at 100° and then over sulphuric acid, it rehydrates with such avidity that the
particles jump about. When it is heated gently above 250°, the compound blackens,
and finally explodes with some violence, giving spongy platinum, nitrogen, oxygen,
and water vapour. If pyridine is employed in place of ammonia, a similar detonating
compound is formed, namely, platinic decahydroxypyridine, C5H5N[Pt(OH)5]2.
The fulminating compound is easily soluble in hydrochloric acid, and its composition
corresponds with (Pt(OH)5J2(NH3), it loses water when heated at 220°,
0 mols. being removed.
The dihydrate PtO2.2H2O can be formulated as the tetrahydroxide, Pt(OH)4,
and M. Blondel added that since two of the hydroxyl groups are basic, and two
acidic, the dihydrate can be regarded as a dihydroxyplatinic acid, H2PtO2(OH)2,
forming in the one case potassium platinate, K2PtO2(OH)2.2H2O, and in the other
case H2PtO2(SO4).3H2O. This subject was discussed by I. Bellucci, and H. Topsoe.
I. Bellucci regarded the tetrahydrate as a hexahydroxyplatinic acid, H2Pt(OH)6,
in -which the six chlorine atoms of hydrochloroplatinic acid, H2PtCl6, have been
replaced by six hydroxy 1-groups. M. Blondel said that before drying, the tetrahydrate
contains the group Pt(OH)4, and after drying it is not to be regarded as
Pt(OH)4.2H20, but rather as H2Pt(OH)6. S. W. Pennycuik observed the acid
in soln. of colloidal platinum.
W. J. Pope and S. J. Peachey prepared trimethyl platinic hydroxide,
(CH3)3Pt(OH), by boiling an acetone soln. of the iodide with silver hydroxide.
Several observers have noted the formation of potassium platinates, thus,
H. Davy, 2 and K. A. Hofmann and H. Hiendlmaier found that the yellow powder
obtained by the combustion of a platinum-potassium alloy behaved like a platinate ;
and S. Tennant obtained by the action of fused potassium nitrate—(i) a brown
insoluble product containing a small proportion of potassium oxide, and (ii) a brown
soluble product. J. J. Berzelius added that when potassium nitrate and hydroxide
are fused with platinum, and the product washed with water, there remains a
partly purple, and partly yellow oxide which dissolves with difficulty in hydrochloric
acid leaving a residue of platinum. When potassium chloroplatinate is boiled with