Resorcinol: Benzene Sulphonated Twice, Then Fused with Caustic Soda (Bindschedler and Busch, Thorpe 1913)

The works route to resorcinol: benzene is sulphonated twice with fuming sulphuric acid, the disulphonic acid turned into its sodium salt, and the dry salt fused with caustic soda; acid then frees the resorcinol, which is taken up in ether. Resorcinol forms colourless needles melting at 119 °C. The crude product holds 92-94 % resorcinol, with some phenol and about 5 % tar, and is cleaned by distilling. Not given: the strength of the fuming acid, how the lime salt is turned into the sodium salt, the amounts of lime, acid and ether, and the yield. Source: E. Thorpe, Dictionary of Applied Chemistry vol. IV (1913), Phenol and its homologues, pp. 180-181, after Bindschedler and Busch (1878). Picture: Rillke, Wikimedia Commons, CC BY-SA 3.0.