Magnesium Platinocyanide, MgPt(CN)₄

Magnesium Platinocyanide, MgPt(CN)₄.7H₂O, is conveniently prepared by decomposing the barium salt with magnesium sulphate solution. On filtering off the insoluble barium sulphate and allowing to evaporate, the salt crystallises out in blood- or carmine-red tetragonal crystals, possessing a metallic-green surface sheen. The parameters of the crystals are:

a: с = 1: 1.06143.

There is no evidence that the salt can exist in two isomeric forms.

When maintained at 30° to 40°C., the pentahydrate, MgPt(CN)₄.5H₂O, is produced, which is yellowish green in colour. The same hydrate may be prepared by maintaining a hot saturated aqueous solution for some time at 45° to 50° C. until the salt separates out; as also by recrystallising the heptahydrated salt from alcoholic solution. The dihydrate, obtained at 100° C., is white, and the anhydrous salt, obtained by heating to 150° or 200° C., is yellow. The following table indicates the colour and fluorescent properties of anhydrous and hydrated salts:

	Colour	Fluorescence
MgPt(CN)4.7H2O	Red with green reflection	None
MgPt(CN)4.5H2O	Yellowish green
MgPt(CN)4.2H2O	White	None
MgPt(CN)4	Yellow	None