A Comprehensive Treatise on Inorganic and Theoretical Chemistry

PLATINUM
presence of a large excess of water. The formation of the green salt is favoured
by the use of concentrated solutions or of solutions acidified with hydrochloric
acid. E. G. Cox and co-workers prepared the pink salt by treating an aq. soln.
of [Pt(NH3)4"jCl2 with a quarter of its vol. of aq. ammonia of sp. gr. 0*88, and then
with a neutral soln. of potassium chloroplatinite free from chloroplatinate. A good
yield of the pink salt is deposited, and it is contaminated with a little green salt.
According to S. M. Jorgensen and S. P. L. Sorensen, the precipitate should be
washed with aq. alcohol, and finally with absolute alcohol ; it furnishes small,
ill-defined needles, rose-red in colour. The same salt is obtained in -well-defined,
small, tetragonal prisms by interaction of the yellow platinous dimethylamineamminochloroplatinite
with platinous dichlorodiammine. JE. Hertel and
K. Schneider found that the space-lattice of the red, tetragonal crystals has
a=6-293 A., c=5-25 A., and a : c==l : 0-8340. E. G. Cox and co-workers said that
these results are wrong. The crystals are rhombic and have a space-lattice with
a—7*9 A., 6=8-2 A., and c—7-9 A. ; the calculated sp. gr. is 3-9, when there are
two mols. of [Pt(NH3)4]PtCl4 per unit cell. The red and green salts are anhydrous,
and in the dry condition they are very stable, but on boiling the red salt with water
it is changed quantitatively into the green salt ; the converse change has not been
observed. E. G. Cox and co-workers found that when examined by X-radiograms
or by the microscope the pink salt of Magnus is indistinguishable from the
empirically isomeric Cleve's salt, [Pt(NHg)3ClJ2PtCl4. According to H. D. K. Drew
and H. J. Tress, the triammine is (i) more soluble in water than the pink salt of
Magnus ; (ii) a cold aq. soln. of sodium nitrate rapidly changes the red to the
green salt, but it does not affect the colour of the triammine ; (iii) a lukewarm
aq. soln. of [Pt(NHg)4]Cl2 liberates the triammine from its platinous salt with the
precipitation of the green salt of Magnus, "whereas with the red tetrammine, there
is no action for some time, and if, on heating, the red salt becomes green, only the
tetrammine, and no triammine is found in the filtrate ; and (iv) when the two salts
are treated with a cold aq. soln. of silver nitrate, silver chloroplatinite is precipitated.
On removing the excess of silver with a soluble chloride, and treating the liquids
with an aqueous soln. of potassium chloroplatinite, in the one case, the initial
triammine is regenerated in red plates, and in the other case, acicular crystals of
the green salt are formed. With potassium chloropalladite so used instead of the
chloroplatinite, the triammine furnishes platinous chlorotriamminochloropalladite,
[Pt(NHg)3Cl)2PdCl4, whereas, the red salt of Magnus gave greyish-pink needles
of platinous tetramminochloropalladite, [Pt(NH4J4JPdCl4. The evidence shows
that there is no connection between the red platinous triammine and the red
form of Magnus' salt.
The red and green salts of Magnus appear to be similar in crystalline form when
viewed under the microscope ; their solubilities are similar ; no difference has been
detected in the chemical reactions ; they have the same molecular weights ;
dichroism does not explain their occurrence ; and nothing has yet been observed
to show any difference in chemical structure. No other pair of red and green
isomeric platinous salts is known, but the substitution of the four ammonia residues
in [Pt(NHg)4JPtCl4 by methyl-, n-butyl-, iso-butyi-, or amyl- amine forms a green
salt, whereas a similar substitution of ethyl- or of w-propyl-amine gives a red
salt, but platinous tetraetnylaminochloroplatinite, [Pt(C2H5NHo)4]PtCl4, is
green.
H. D. K. Drew and co-workers prepared platinous tetramminochloropalladite,
[ Pt(NH3)4 JPdCl4, in lilac-grey needles. J. Reiset prepared platinous tetramminochloroplatinate,
[Pt(NH3)4]PtCl6, as a red, crystalline mass by the action of an
excess of platinic chloride on platinous tetramminochloride, but P. T. Cleve said
that [Pt(NHg)4Cl2]PtCl4 is produced by this process. A. Cossa, however, obtained
it by adding, at ordinary temp., a neutral soln. of platinic chloride, or of sodium
chloroplatinate, to a soln. of platinous tetramminochloride. The yellow, amorphous
product slowly passes into [Pt(NHg)4Cl2]PtCl4, and the change is rapid with boiling
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