Using apparatus designed by ourselves, we obtained data on 11 binary azeotropic systems at normal pressure, and 20 binary and 7 ternary azeotropic systems at subatmospheric pressures. The data obtained for binary azeotropes, were used to predict the azeotropic data and vapor-liquid equilibria for ternary systems, and the heats of vaporization for azeotropic mixtures. In general, the results obtained gave linear plots of the logarithm of pressure versus the reciprocal of temperature and of the azeotrope composition versus temperature. A minimum boiling point azeotrope is usually formed by hydrocarbon-alcohol binary systems. The alcohol content of the azeotropic mixture increases as the pressure is raised, and decreases as the number of carbon atoms is increased (constant pressure).