New thermodynamic relations concerning apparent molar isentropic compression and apparent and partial isentropic compressibilities

Abstract

Some formal advances in the thermodynamics of solutions are presented and illustrated using isentropic quantities. A convenient method for dealing with expressions relating different apparent properties is introduced. This procedure is applied to ameliorate the Desnoyers–Philip equation for the difference between apparent molar isothermal and isentropic compressions, and in the analysis of Blandamer's molar isentropic compression. Apparent as well as partial quantities for intensive properties of a solution are defined. Their interrelationship is shown to be formally identical with that for conventional apparent and partial molar quantities. Also addressed are the links between the new apparent and partial quantities and their conventional molar counterparts, and between second-order partial quantities and Koga's composition derivative of partial molar quantities. Finally, the terminology of apparent and partial quantities is discussed, and the name ‘heat capacitance’ is suggested for the volume-specific isobaric heat capacity.