Relationship between effective and ideal separation factors for distillation and sublimation

Abstract

General aspects of the relationship between the effective (β) and ideal (β_i) separation factors for the distillation and sublimation of elemental substances containing low-volatile impurities have been established. It has been shown that the difference between β and β_i may be both insignificant and extremely large: 4 to 16 orders of magnitude or even more. In host–impurity systems having the same host, the difference between β and β_i decreases as β_i approaches unity, all other factors being the same. The difference between β and β_i is moderate, within one order of magnitude, when βi differs from unity by no more than three orders of magnitude. In a given host–impurity system, the difference between β and β_i increases with decreasing impurity concentration. In individual systems, the difference between β and β_i increases with increasing yield at a given initial impurity concentration.