Study on the vacuum distillation of pure metals. (2) Basic law and applications

The evaporation rate of pure, Pb, Cd, Zn under different pressure and temperature was investigated both theoretically and experimentally. The comparison between the calculated results and the experimental results shows good agreement with each other: (1) the evaporation rate increases with the temperature-increase and pressure-decrease; (2) when the pressure decreases below a critical value, the further decrease in pressure has little influence on the evaporation rate, and in this case, the surface temperature of liquid metal is lower than its inner temperature, therefore, it is the inner heat transfer process that dominates the evaporating process. The evaporation temperature and vacuum degree needed for industrial application can thus be determined.