Compressibilities of aqueous tert-butanol in the water-rich region at 25deg C: Partial molar fluctuations and mixing schemes

摘要

We measured the speeds of sound, u, and the densities, d, and, hence, determined the adiabatic compressibilities, k_S, of aqueous tert-butanol (TBA) at small increments in mole fraction of TBA, X_(TBA). Existing data for heat capacity, C_p, and thermal expansivity, #alpha#_p, were used to convert k_S to the isothermal compressibilities, k_T. Using these k_T data, the normalized volume fluctuations, ~v #DELTA#, and their composition derivative, the partial molar volume fluctuations of TBA, ~V #DELTA#_(TBA), (Y. Koga and P. Westh, Bull. Chem. Soc. Jpn., 1996, 69, 1505) were calculated. By using C_p data available in the literature we also calculated the normalized entroupy fluctuations, ~S #DELTA#, and the partial molar entropy fluctuations of TBA, ~S #DELTA#_(TBA). Furthermore, the density data at 15, 25 and 35deg C in the literature were used to evaluate the thermal expansivities, #alpha#_p, from which the normalized cross (entropy-volume) fluctuations, ~(SV) #DELTA#, and the partial molar cross-fluctuations of TBA, ~(SV) #DELTA#_(TBA), were calculated. The composition dependence of these fluctuation functions were interpreted in the light of the mixing schemes in aqueous solutions of TBA and other non-electrolytes and the transition between them (Y. Koga, J. Phys. Chem., 1996, 100, 5172).