The impure glycerin obtained as above is purified by redistillation in steam and evaporation in vacuum pans.
A redistilled zinc, from an ordinarily pure commercial zinc, is often called chemically pure, but redistillation is seldom practised except for the recovery of zinc from galvanizer's dross and from the skimmings and bottoms of the melting furnaces of zinc rolling mills.
Sainte Claire Deville's process, which used to be employed commercially, was essentially the same, except that sodium was substituted for potassium (Comptes rendus, 18 57, 44, p. 394), the product being further purified by redistillation.
It may be purified by redistillation over barium and silver nitrates, followed by treatment of the distillate with a stream of ozonized air.
The crude bromine is purified by repeated shaking with potassium, sodium or ferrous bromide and subsequent redistillation.