Purification and Fractionation of 90 Benzol

Purification and Fractionation of 90% BenzoL—Commercial benzene is far from pure and contains homologues (chiefly toluene) and thiophen as well as basic substances. On removal of the bases with dilute acid and the thiophen with cone, sulphuric acid, fairly pure benzene may be obtained by fractional distillation of the residue. 90% benzol contains about 80—82% benzene, 14—15% toluene, and about 3% xylenes. The term means that 90% by volume of the benzol can be distilled off up to 100°. 

The residue in the distilling flask after removing the fraction 79°—82° may be distilled up to 100°, and the earlier fraction boiling at 100°—115° then added. Fractions may be collected as before and the final fraction redistilled, the portion distilling at 109-5°—110-5° being collected. This consists of toluene. 

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