Toluene: Crude Benzol Rectified in Coupier's Steam Still (Lunge, 1887)

Toluene, methylbenzene, is the coal-tar hydrocarbon that boils at 111 °C, next above benzene. G. Lunge's Coal-Tar and Ammonia (1887) shows how Coupier separated it in 1863: crude benzol is boiled by a steam coil under a column, and the vapours pass through condensers in a water trough whose temperature decides what gets through. At 60-70 °C only benzene passes; raised to 100 °C, toluene follows. From 100 litres of ordinary 50-per-cent benzol Coupier got 44 litres of pure benzene and 17 litres of pure toluene. The plant size and times are not given. Source: G. Lunge, Coal-Tar and Ammonia (1887), pp. 461-464, Figs. 118-119. Picture: his Fig. 118, Coupier's still.