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.

The solubility of cefpiramide sodium in binary solvent mixtures of ethanol + water and 2-propanol + water was determined by a steady-state method from (278.2 to 303.2) K and in the initial mole fraction range of alcohol (ethanol or 2-propanol) in the solvent mixture at about 0.4 to 0.8. Cefpiramide sodium exhibits the same order of magnitude of solubility in both binary systems. The solubility decreases with the increase of the initial mole fraction of alcohol and increases with increasing temperature. Dilution crystallization or dilution crystallization incorporated with cooling crystallization will be more suitable than pure cooling crystallization for the purification of cefpiramide sodium. The Jouyban–Acree model, combined with the van’t Hoff equation, was used to correlate the solubility data. The combined model was further simplified so that each item in the model is statistically significant at the 5 % level. The simplified combined model gives a mean relative deviation of 5.3 % for the ethanol + water system, and 3.0 % for the 2-propanol + water system. This model demonstrates good fitting with the experimental solubility data, and could be used for related process design in the pharmaceutical industry.