The distillation of completely miscible mixtures is the most common practically and the most complex theoretically.
When distilling a mixture of partially miscible components a distillate of constant composition is obtained so long as two layers are present, i.e.
For simplicity we confine ourselves to mixtures of two components, in which experience shows that three cases are to be recognized according as the components are (I) completely immiscible, (2) partially miscible, (3) miscible in all proportions.
The investigation of the mutual relations of partially miscible liquids, due to P. Alexejew, D.
It is miscible in all proportions with alcohol, ether and water.
It may happen that the crystals do not form double salts, and are only miscible in certain proportions.
Of completely miscible mixtures.
As the distillation proceeded one layer would diminish more rapidly than the other until only the latter would remain; this would then distil as a completely miscible mixture.
It is miscible in all proportions with water, alcohol and ether.
In these two instances the component crystals are miscible in all proportions; but this is by no means always the case.