Vapour-liquid equilibrium. The effect of temperature on the equilibrium vapour phase composition and on the azeotropic point composition

On the basis of analysis of calorimetric data, it is shown that the tert-butyl alcohol(1)-water(2) system exhibits the non-monotonous dependence of the equilibrium vapour phase composition on temperature which is reflected in the non-monotonous dependence of azeotropic composition on temperature. This behaviour is conditioned primarily by the fact that the molar heats of vaporization of both the substances have the same value at the temperature of 57°C. From the values of heats of vaporization of C3 and C4 alcohols and water it is evident that the analogous behaviour occurs also in aqueous systems of these alcohols at common temperatures.