The unusual behavior of extractive distillation—Reversing the volatility of the acetone–isopropyl ether system

Extractive distillation can not only negate azeotropes to produce pure compounds by rectification but in some cases will reverse the volatility and bring out the less volatile component before the more volatile component. As an example, isopropyl ether, b.p. = 68.5°C, was distilled off as the overhead from mixtures with acetone, b.p. = 56.2°C, leaving the acetone in the stillpot and column until all the isopropyl ether was removed. This reversal phenomenon does not occur in the isopropyl ether‐methyl ethyl ketone system, although the azeotrope is negated.