LAUSR

The solubility of cefpiramide in five pure solvents (water, ethanol, 1-propanol, 2-propanol, and 1-butanol) and two binary solvent systems (water + ethanol or water + 2-propanol) was measured by a steady-state method, from 278.2 to 303.2 K, under atmospheric pressure. The initial mole fraction of alcohol (ethanol or 2-propanol) in the binary systems ranged from 0 to 1. It is found that the solubility increases with increasing temperature in the experimental range and shows a quasi-S-shaped curve with the increase of the initial mole fraction of alcohol. The modified Apelblat equation was used to simulate the solubility data, and gives a maximum mean relative deviation (MRD) of 0.47% for the single solvent systems, and a maximum MRD of 1.03 and 1.15% for the ethanol + water and 2-propanol + water systems, respectively. The combined model of the Jouyban–Acree and modified Apelblat equations, both temperature-dependent and solvent-composition-dependent, was simplified to correlate the solubility data of binary solvent mixtures in the initial mole fraction range of alcohol from 0 to 0.9, and gives a MRD of 9.83 and 6.49% for the ethanol +water and 2-propanol + water systems, respectively. The dissolution thermodynamic properties in the pure solvents and two binary mixtures were calculated based on the van’t Hoff equation. The calculation results indicate that the dissolution process of cefpiramide is endothermic in the pure solvents, and entropically driven in the four alcohols but not in water. The dissolution process is endothermic in the two binary mixtures.