Measurement and correlation solubility and mixing properties of l-malic acid in pure and mixed organic solvents

• The solubility of l-malic acid in pure and mixed solvents.
• The Apelblat equation and λh equation were used to correlate with the solubility.
• The dissolution of l-malic acid is an endothermic and entropy-driving process.
• Apelblat equation provides a more reasonable predication in mixture solvent.

The solubilities of l-malic acid in pure and mixture organic solvents were measured from 278.15 to 323.15 K using the laser monitoring observation system. The modified Apelblat equation, the semi-empirical Buchowski–Ksiazczak λh equation and the Combined Nearly Ideal Binary Solvent/Redlich (CNIBS/R-K) equation were proposed to correlate the experimental data. In pure and mixed solvents, the 100RD (relative deviation) <3.61 and 7.58, respectively, the 104RMSD (root-mean-square deviations) <3.07 and 2.28, respectively, so the equations selected in this work fit the data very well. Van’t Hoff equation was used to predict the dissolution enthalpy and entropy of l-malic acid in the corresponding solvents.