From the tar distillate, the chrysene can be fractionally precipitated, and the fluoranthene can be separated from most of the pyrene by fractional distillation in a partial vacuum.
For this purpose the crude distillate is redistilled over sulphuric acid and then fractionated.
In 1867 Rees Reece, taking advantage of the fact that two vapours of different boiling-points, when mixed, can be separated by means of fractional condensation, brought out an absorption machine in which the distillate was very nearly anhydrous.
The alkaloid is obtained from an aqueous extract of tobacco by distillation with slaked lime, the distillate being acidified with oxalic acid, concentrated to a syrup and decomposed by potash.
The distillate is freed from vanadium by digestion with sodium amalgam.