The solubility of betaine in water, methanol, ethanol, n-propanol, 2-propanol, and n-butanol and also in methanol + ethanol and ethanol + water binary mixtures has been experimentally measured using a laser monitoring observation technique. The modified Apelblat equation was used to correlate the solubility of betaine in the studied pure solvents. The solubility of betaine in the binary solvent mixtures was correlated by a hybrid model based on the Jouyban−Acree model and modified Apelblat equation. The associated P-values of terms for model were used to simplify the hybrid model, which reduced the number of the model parameters without affecting the values of mean percentage deviation (MPD) and R 2 . With these models the maximum MPD for studied solvents is 1.94. Thermodynamic functions including ΔH soln 0 , ΔG soln 0 , and ΔS soln 0 of solution of betaine were obtained from the modified van't Hoff equation. A comparison of the relative contributions by enthalpy (ζ H ) and entropy (ζ TS ) was made (with ζ H > 0.6 and even up to 0.99 in methanol), which indicated that the main contributor to the positive standard molar Gibbs energy of solution of betaine was enthalpy in both pure solvents and mixtures.

The solubility of thiotriazinone in water, methanol, ethanol, water + methanol, and water + ethanol has been measured under temperatures ranging from (283 to 330) K with a laser technique. The results of these measurements were correlated with semiempirical equations. The calculated results have showed fine representativity of experimental data. The stepwise regression method was used to simplify the modified Jouyban–Acree equation.

The solubilities of (Z)-2-(2-aminothiazol-4-yl)-2-methoxyiminoacetic acid in water and alcoholic solvents (methanol, ethanol, 1-propanol, glycol) and the combination of water þ alcohols (methanol, ethanol, glycol) of binary mixtures have been experimentally measured in the temperature range from (282 to 330) K using a laser monitoring observation technique. The experimental solubilities in the pure solvents were correlated by modified Apelblat equation. A hybrid model proposed based on Apelblat equation and Jouyban-Acree model was used to correlate the solubility of solute with the variation of both temperature and initial composition of the binary solvent mixtures. With these models the maximum mean percentage deviation is 5.21.

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