Strontium Pyrosulfate

Description

Strontium pyrosulfate has the molecular formula of SrS₂O₇ and the molecular weight of 263.7478 g/mol. It is expected to be more stable to decomposition in water than the Be, Mg and Ca homologues but no specific data on this aspect has appeared in the literature. There are no references in the scientific literature concerning this salt. Whether this salt is stable in aqueous solution remains unknown. This may explain why the data on strontium pyrosulfate (disulfate) is sparse to nonexistent. It can be prepared via a solid-state reaction with ammonium pyrosulfate:
SrCl2+(NH4)2S2O7+heat
? SrS2O7+2NH3(gas)+H2O(gas)
The solubility of this salt has not been reported. The existence of hydrates is unknown. However, if one heats the persulfate, a pyrosulfate salt can be obtained:
2SrS2O8 ? 2SrS2O7+O2
Further heating then forms the sulfate plus oxygen. These reactions have not been studied critically and no decomposition temperatures can be quoted. Another method of preparation involves the sulfate. If strontium sulfate is mixed with fuming sulfuric acid (to minimize the water present), it dissolves forming a syrup which upon heating to 150°C deposits the pyrosulfate crystals which are stable. Further heating removes water and the excess acid. These crystals are stable to about 720°C where they decompose to form the sulfate plus sulfur trioxide.