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The protonation constant pKa2of l-norvaline has been determined in aqueous solution at different ionic strengths and different temperatures, using the pH-metric technique. The thermodynamic quantities (ΔG°, ΔH°, and ΔS°) have been studied and discussed. Evaluation of the effect of organic solvent of the medium on the protonation processes was also reported and discussed. The organic solvents used were methanol, dimethylformamide (DMF), dimethylsulfoxide (DMSO), acetone, and dioxane. The pKa2values for the ionization in a water (1) + dioxane (2) mixture [100 w2= 10 %, 20 %, 30 %, 40 %, and 50 %] have been determined at five different temperatures from T= (288.15 to 308.15) K. The thermodynamic quantities were calculated. [ABSTRACT FROM AUTHOR]

The solubilities of sebacic acid in mixed solvents n-propanol + water have been measured by a dynamic method using a laser monitoring observation technique over a temperature range (288 to 351) K. A synergistic effect on solubility was found to occur in sebacic acid + n-propanol + water mixed systems. To detect the synergistic effect, solubilities of sebacic acid in 14.35 %, 36.97 %, 79.81 %, and 90.00 % mole fraction ethanol aqueous solution were determined to supplement our previous report. A weak synergistic effect was found for sebacic acid + ethanol + water mixed systems. The solid−liquid equilibrium (SLE) data have been fitted using the λhequation, the Wilson equation, and the NRTL equation. The comparison between the experimental and the calculated solubilities for the three models is reasonable, and the root-mean-square deviations for each system range from (0.30 to 1.95) K. [ABSTRACT FROM AUTHOR]

The solubilities of cloxacillin sodium in binary butyl acetate + methanol and ethyl acetate + methanol solvent mixtures were measured at temperatures ranging from (283.15 to 298.15) K. The experimental data can be well correlated by the CNIBS/Redlich−Kister model. The results show that the solubility of cloxacillin sodium increases with increasing temperature and mole fraction of methanol in these two binary mixed solvents. [ABSTRACT FROM AUTHOR]