Solubility of Phthalic Acid and o-Toluic Acid in Seven Organic Solvents: Experimental Measurement and Thermodynamic Modeling

In this study, the solubility of phthalic acid and o-toluic acid in propionic acid, N-methylformamide, N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), and acetonitrile are measured under atmospheric pressure (101.3 kPa) by the method of laser dynamics. The experimental temperature range is 286.35 to 338.75 K. The measured data shows that the solubility of phthalic acid and o-toluic acid increases with increasing temperature in the temperature range studied. The experimental data are correlated by the Apelblat model, the λh model, and the modified nonrandom two liquid activity coefficient model, and the calculated solubility is in agreement satisfactorily with the measured results. Akaike information criterion analysis results show that the Apelblat model was the most suitable model to correlate the solubility of phthalic acid in propionic acid, N-methylformamide, and DMSO and the solubility of o-toluic acid in propionic acid, DMSO, and NMP; the λh model was the most suitable model to correlate the solubility of phthalic acid in DMF and DMAC and the solubility of o-toluic acid in N-methylformamide and DMF; and the modified NRTL model was the most suitable model to correlate the solubility of phthalic acid in NMP and acetonitrile and the solubility of o-toluic acid in DMAC and acetonitrile.