Evaporation from Binary Mixture under a High Vacuum

Abstract

Experiments on evaporation of simple systems of di (2-ethylhexyl) phthalate (EHP) and m-tricresyl phosphate (m-TCP) and on distillation of EHP-m-TCP binary system were made in a range of pressure from 1.0 × 10^-3 to 3.5 × 10^-1 mmHg by use of a pot still. The results obtained show the following facts; 1) In the domain of evaporation without molecular-burst-evaporation, the values of relative volatility are equal to the theoretical value. At the threshold of molecular-burst-evaporation, a deviation of relative volatility from the theoretical value occurs, and at the point of completion of molecular-burst-evaporation the value of relative volatility is a minimum. From the viewpoint of separation, it is advisable to avoid the occurrence of molecular-burst-evaporation as much as possible. 2) The threshold temperatures of molecular-burst-evaporation of a binary system are lower than those of simple systems. 3) In a range of mole fraction in liquid from 0.45 to 0.50, evaporation rate of lighter component (EHP) has a maximum and evaporation rate of heavier component (m-TCP) has a minimum. But the effect of liquid concentration on evaporation rate is smaller than that of liquid surface temperature.