Crude Benzol: Light-Oil Naphtha Washed and Steam-Rectified to 50-per-cent Benzol (Lunge, 1887)

Crude benzol, the '50-per-cent benzol' of the tar works, is coal-tar naphtha cleaned with acid and alkali and distilled by steam: roughly half benzene, the rest toluene and xylenes, boiling from about 62 to 150 °C. It is the feed from which benzene and toluene are separated. G. Lunge's Coal-Tar and Ammonia (1887) gives the work: a little over 1 lb of oil of vitriol per gallon of naphtha, mixed and settled; four or five water washes; dilute caustic soda until the colour turns; two more water washes; then steam distillation through a dephlegmator kept at 70-80 °C. He gives no batch or still size, and says the dephlegmator heat must be found by experience for each apparatus. Source: G. Lunge, Coal-Tar and Ammonia (1887), pp. 437-439, 455. Picture: his p. 455.