This is mixed with small coal, and when redistilled gives an enriched dust, and by repeating the process and distilling from cast iron retorts the metal is obtained.
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.
This is neutralized with lime and redistilled in order to remove the acetic acid.
The fluorene is separated from this by placing it in a freezing mixture, and is then redistilled or crystallized from glacial acetic acid, or purified by means of its picrate.
It is then dehydrated and redistilled.