Using a laser monitoring observation technique, the solubilities of cefazolin sodium pentahydrate in binary 2-propanol + water solvent mixtures were determined by the synthetic method from 273.15 K to 308.15 K. The results of these measurements were correlated by the combined nearly ideal binary solvent (CNIBS)/Redlich-Kister equation. For the eight group data studied, the combined ideal binary solvent (CNIBS)/Redlich-Mster equation was found to provide an accurate mathematical representation of the experimental data.