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The heats of dilution of KCI, MgCI2, Na2S04, and MgS04 were measured over a concentration range of 0.005-2.Om at temperatures between 40-80°C. The data were extrapolated to infinite dilution by use of the Debye-Hückel limiting law to obtain relative apparent molal heat contents ( _). The heats of dilution of MgCI2 and MgS04 were measured at 25 °C and combined with the low concentration work of Lange and Streeck to yield values of L. The relative partial molal heat content of solvent and solute was calculated from the experimental values. The heat content data were then used to calculate activity and osmotic coefficients in the temperature range 40-80°C.

The heats of dilution of aqueous NaCI were measured over a concentration range of 0.1 -6.0m at 40°, 50°, 60°, 70°, and 80°C. The relative partial molal heat contents of solute and solvent were calculated from the experimental heats of dilution. These values were used to extend by calculation existing activity and osmotic coefficients to higher temperatures. These calculated values were found to be in excellent agreement with existing data. It is concluded that the use of heat of dilution data to correct existing values of thermodynamic quantities to higher temperatures is an efficient and very precise technique.

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