Strontium Thiosulphate, SrS2O3, may be formed by boiling sulphur with strontium hydroxide and precipitating with alcohol, by the action of sulphur dioxide on a hot solution of strontium sulphide, or, finally, by precipitating a hot solution of strontium nitrate with sodium thiosulphate. The thiosulphate crystallises out on cooling or on adding alcohol. It forms large hexagonal crystals of composition SrS2O3.5H2O, more stable than the corresponding calcium salt. It is soluble in 4 parts of water at 13° C., and in 1.75 parts at 100° C. It loses 4 molecules of water at 100° C. Dried at 200° C., it has the composition 2SrS2O3.H2O. Further dehydration is accompanied by decomposition, and, on strongly heating, the salt forms a phosphorescent mixture of sulphide, sulphate, and sulphur according to the equation -
4SrS2O3 = SrS + 3SrSO4 + 4S.
Clarke gives the density of a hexahydrate as 2.1566 and 2.1991 at 17° C. |