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Abstract
The heat of precipitation of silver laurate was measured calorimetrically over the temperature range from 14 to 45°C, and the results compared with data derived from the dependence of silver laurate solubility on temperature. The standard enthalpy change was found to vary linearly with the thermodynamic temperature, whereas the standard entropy change was a linear function of the logarithm of the temperature. The slopes of both plots yielded the same value of the heat capacity change. Accordingly, the enthalpy of surfactant salts precipitation or dissolution cannot be obtained from the temperature dependency of solubility alone. The latter procedure is based on the assumption of negligible heat capacity change, which is not the case for precipitation reactions. The data on silver laurate also suggest that the heat capacity change does not vary much with temperature.
Notes
*Dedicated to Dr. Paul Becher on his 70th birthday.