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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The reaction of barium chromate(v) with molten lithium-potassium nitrate eutectic was investigated and the stoichiometry of the reaction established. The results of this study indicate that nitryl ion, NO2+, is possibly an acidic/oxidizing species produced by the autoionization of nitrate ion when a nitrate melt functions as a reactive solvent.

The reactions of 11 inorganic anions added as their sodium or potassium salts to molten sodium-potassium hydrogen sulfate eutectic were studied and their stoichiometries elucidated. It was found that Na2CO3, NaNO2, KNO3, Na2SO3 and Na2S2O3 reacted with the melt to form water and CO2, NO+NO2, NO2+O2, SO2, S6+SO2 respectively. NaCl, KBr produced HCl and HBr while KI reaction products consisted of I2, SO2 and H2O; K2CrO4 and K2Cr2O7 were converted into H2CrO4 and H2Cr2O7 respectively. These acids decomposed to H2O, O2 and Cr2O3 which reacted further with the melt to produce H2O and Cr2(SO4)2,H2O. K2S2O8 was found to decompose thermally to O2 and K2S2O7 without reacting with the melt.