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The thermal decomposition of mercury(1) and (II) sulfates has been investigated by thermogravimetry. The solid-state decomposition products have been characterized by infrared and Raman spectroscopy, mass spectrometry and an X-ray diffraction method. It is concluded that mercury(I) sulfate decomposes in two steps, initially forming a mixture of metallic mercury and mercury(I1) sulfate --the latter subsequently decomposes without forming a stable intermediate. The stoichiometry of disproportionation of mercury(1) sulfate and the thermal stability range of mercury(I) and mercury(I1) sulfates have been established.

Lithium, sodium, potassium and ammonium bisulphate have been shown by detailed TG/DTA studies to have limited application as molten solvents. By contrast, the eutectic bisulphate systems, ammonium-potassium bisulphate and sodium-potassium bisulphate, appear to be excellent molten solvents in view of their low melting points, long liquid ranges and prolonged thermal stability at 200 ~ . In contrast to previous studies, potassium pyrosulphate has been found to be an excellent molten solvent, provided rigorous preliminary drying procedures have been applied.A thorough knowledge of the thermal stability of a salt melt is an essential prerequisite if the melt is to be used as a reactive solvent for inorganic solutes. The relatively low melting points of alkali metal and ammonium bisulphates, and also alkali metal pyrosulphates suggest that these compounds may be useful reactive molten solvents. The present work involves various one-and two-component salt systems with a view to investigating the usefulness of these salts as molten solvents. The thermal properties of several of these systems have been reported previously [1-9], however, the wide variation in results due to differences in preliminary sample preparation, operating conditions, and precision of thermoanalytic~al-equipment, made a thorough re-examination of these systems necessary. Isothermal thermogravimetric studies on most of the systems have not been previously reported. The salts investigated in the present programs are sodium bisulphate, potassium bisulphate, lithium bisulphate, ammonium bisulphate, eutectic sodiumpotassium bisulphate, eutectic potassium-ammonium bisulphate, and potassium pyrosulphate.

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