Salol: Salicylic Acid and Phenol Melted with Phosphorus Oxychloride (Nencki and Seifert, 1886)

Salol, phenyl salicylate, is the ester of salicylic acid and phenol: colourless crystals that melt at 43 C, insoluble in water. M. von Nencki and R. Seifert patented its making in 1886: melt two parts salicylic acid with two parts phenol (by molecules), heat to 120 C and add one part phosphorus oxychloride little by little. Hydrogen chloride escapes and salol forms; water separates it from the melt, soda washes it and alcohol recrystallises it. The scale and the glassware are ours. Their second route, from sodium salicylate, is a separate blueprint. Source: US 350,012 (1886). Picture: their specification, p. 1.