Standard heats and volume changes of solution of acetone, n-butanol, chloroform, and water in methanol, isopropanol, and mixtures of the two are reported. In every case, the value of a measured property in a mixture is more negative than the mole-fraction average of the values measured in the pure solvents. Equations relating the heat of solution in a binary mixture to the heats of solution in the pure solvents and the excess enthalpy of the binary mixture are developed from equations for the excess enthalpy of simple ternary systems. Heats of solution of n-butanol agree fairly well with predicted values. Combination of standard heats of solution with standard volume changes of solution allow estimation of standard energy changes of solution at constant volume. © 1974 Plenum Publishing Corporation.