Solid-liquid equilibria of dicarboxylic acids for binary mixtures-nonanedioic acid (1) + 3-methylheptanedioic acid (2) (eutectic temperature T-E = 342.25 K, eutectic composition x(1E) = 0.364); nonanedioic acid (1) + 2,2-dimethylbutanedioic acid (2) (T-E = 367.51 K, x(1E) = 0.653); nonanedioic acid (1) + 2,3-dimethylbutanedioic acid (2) (T-E = 354.27 K, x(1E) = 0.463); decanedioic acid (1) + 3-methylheptanedioic acid (2) (T-E = 352.47 K, x(1E) = 0.134); decanedioic acid (1) + 2,2-dimethylbutanedioic acid (2) (T-E = 384.38 K, x(1E) = 0.483); and decanedioic acid (1) + 2,3-dimethylbutanedioic acid (2) (T-E = 365.38 K, x(1E) = 0.192)-are measured using differential scanning calorimetry (DSC) and correlated using the ClarkeGlew equation in this study. Simple eutectic phase diagrams for these systems are observed. The experimental results are correlated using the Wilson and nonrandom two-liquid (NRTL) activity coefficient models, and satisfactory results are presented.