Apparent and partial ideal molar isentropic compressibilities of binary liquid mixtures

The excess apparent molar isentropic compressibilities of binary liquid mix tures, which are derived from ultrasonic speed measurements, are frequently used to probe the macroscopic effects of intermolecular forces. The compos ition dependence of the apparent and partial molar isentropic compressibili ties of components of ideal mixtures is explored, with special interest bei ng shown in the infinite aqueous dilution limit. Attention is also paid to convenient methods for estimating the effects of solvation and of cosphere overlap in water-rich mixtures. In particular, it is shown that the differe nce between excess partial molar and excess apparent molar isentropic compr essibilities gives a strong indication of the magnitudes of the effects of solute-solute interactions.