Salt effect on the enthalpy of mixing of 2-propanol + acetic acid at 303.15 K

Salt effect on the enthalpy of mixing of 2-propanol + acetic acid at 303.15 K This paper presents the effect of two dissolved inorganic salts (zinc chloride, ZnCl2 and ammonium chloride, NH4Cl) on the enthalpy of mixing (HE) of 2-propanol + acetic acid binary system measured at 303.15 K using an isothermal displacement calorimeter with vapour space. A decreasing trend in the excess enthalpy of mixing values in the presence of ZnCl2 and NH4Cl indicate the endothermic behavior of this system. The Redlich-Kister equation has been used to fit the experimental HE data. The deviations from the ideal value and binary parameters were calculated and reported.

Infrared powder-absorption spectroscopy of Ca-free P21/c clinopyroxenes

Infrared powder-absorption spectra of ten synthetic P21/c pyroxenes with compositions in the clinoenstatite–clinoferrosilite system have been collected at room temperature in the range 50–1500 cm−1. Variations of peak positions as a function of Fe content have been obtained for those vibrational bands whose trend could be followed across the solid solution. Local elastic strains arising from cation substitution have been quantified by means of the autocorrelation function, which gives a measure (Δcorr) proportional to the line width of the IR bands. The structure of clinoenstatite appears to be very homogeneous, whereas Fe-rich pyroxenes have high degrees of local structural hetereogeneities. A positive deviation from linearity of the Δcorr values is observed in the spectral region between 100 and 250 cm−1 and may be indicative of a positive excess enthalpy of mixing of this solid solution. At higher energies the large changes in the phonon spectra as Fe content increases are associated with rotation and deformation of the tetrahedral chains for accommodating the larger cation. The results are compared with similar studies on other chain silicates.