Petroleum, which is brought into commerce in immense quantities, especially from Pennsylvania, for illuminating purposes, cannot be used in its crude state, but requires rectification. Petroleum as it issues from the earth consists of various hydrocarbons mixed together, some of which have very low boiling-points, so that their vapors readily take fire and would make the use of petroleum in lamps dangerous. Petroleum, therefore, is heated in large apparatuses to about 70 or 80° C. (158 to 176° F.), when the more volatile products pass over, and the petroleum for illuminating purposes remains in the stills. A certain fraction of the volatile distillate, the so-called petroleum ether, is largely used in the manufacture of varnishes. Owing to its great solvent power for aromatic vegetable substances and its low price, petroleum ether has become quite an important body for the extraction of perfumes, which will be further discussed hereafter. Good petroleum ether is colorless, has a peculiar, not unpleasant odor and a boiling-point between 50 and 55° C. (112° and 131° F.). BENZIN is a common name for another fraction of the volatile distillate from petroleum, viz., that which boils between 50° and 60°C. (122° to 140° F.) and has a spec. grav. of 0.670 to 0.675°. This liquid, which is also used as a volatile solvent for the extraction of odorous substances, must not be confounded with Benzene or Benzol, a distillate from coal tar, boiling at about 80° C. (176° F.) and having a spec. grav. of 0.878. The latter is not used for the extraction of perfumes. BISULPHIDE OF CARBON. This is made by conducting vapors of sulphur over glowing charcoal or coke. The vapors of bisulphide of carbon thus formed are led into vessels filled with ice or ice-cold water, where they condense. Bisulphide of carbon is a colorless liquid, heavier than water and very refractive. It is inflammable, and possesses a peculiar odor which is not disagreeable if the liquid has been thoroughly purified. Its boiling-point is about 45° C. (113° F.) and it has great solvent power. At the present time, the market affords bisulphide of carbon of a high degree of purity.