Apparent molar isentropic compressions and expansions of solutions

Isentropic compressibilities of solutions kappa (S) are readily calculated using the Newton-Laplace equation together with measured speeds of sound and densities. The result is an apparent molar isentropic compression for a given solute-j, phi (K-Sj; def) and a limiting property, phi (K-Sj; def)(infinity). This review examines the definition and calculation of phi (K-Sj; def) and phi (K-Sj; def)(infinity), commenting on the related isentropic expansions, phi (E-Sj; def) and phi (E-Sj; def)(infinity). We describe the thermodynamics which underpins the use of isentropic properties in the study of solute-solvent and solute-solute interactions.