A Comprehensive Treatise on Inorganic and Theoretical Chemistry

PLATINUM 379
H. Topsoe prepared copper bromoplatinate, CuPtBr0.8H2O, by spontaneously
evaporating mixed soln. of cupric bromide and hydrobromoplatinic acid. The
brown plates are probably rhombic with the axial ratios a : b : c=0-744 : 1 : 1-009.
The crystals of the octohydrate deliquesce in air, and at 100° form a brown powder
of the anhydrous salt. L. Pigeon, and A. Miolati and I. Bellucci obtained silver
bromoplatinate, Ag2PtBr6, from soln. of silver nitrate and hydrobromoplatinic
acid. L. Pigeon gave for the heat of formation (PtBr4, 2AgBr) = 10-37 CaIs.
A. Miolati and I. Bellucci found that the salt is not decomposed in a sealed tube at
150°, and it is stable when boiled with a large excess of -water.
P. A. von BonsdorfE, and H. Topsoe prepared calcium bromoplatinate,
CaPtBr6.12H2O, DV neutralizing hydrobromoplatinic acid with calcium carbonate,
and evaporating the soln. over sulphuric acid. The scarlet-red crystals are monoclinic
; they are stable in air and soluble in water. H. Topsoe prepared strontium
bromoplatinate, SrPtBr6.10H2O, in a similar manner ; the tabular crystals have a
sp. gr. of 2*923, and mol. vol. 323-2. They are a little deliquescent. H. Topsoe,
and P. A. von BonsdorfE prepared barium bromoplatinate, BaPtBr6.10H2O.
The reddish-brown crystals are probably monoclinic ; the sp. gr. is 3-713, and the
mol. vol., 267-8. The crystals are stable in dry air, but deliquesce in moist air.
They are dehydrated at 120°.
H. Topsoe, and P. A. von Bonsdorff prepared magnesium bromoplatinate,
MgPtBr6.12H2O, by cooling a hot soln., or by spontaneously evaporating a soln.
of magnesium bromide and hydrobromoplatinic acid. The dark scarlet-red crystals
are, according to H. Topsoe, and H. Topsoe and C. Christiansen, trigonal with the
axial ratio a : c=l : 0-6974, and