In a 5-l. round-bottomed flask equipped with a mechanical stirrer are mixed 385 g. (335 cc., 3.8 moles) of 95 per cent furfural (p. 280) (Note 1) and 3 l. of water. Then 500 g. (630 cc., 8.6 moles) of acetone (Note 1) is added. The mixture is stirred and cooled to 10° and to it is added 75 cc. of 33 per cent sodium hydroxide solution, whereupon some heat is generated. Without cooling, the stirring is continued for four hours. At the end of this time 10 per cent sulfuric acid is added until the mixture is acid to litmus (about 350 cc.) (Note 2). The two layers which have formed are separated and the upper aqueous layer is distilled (Note 3) under ordinary pressure until the distillate no longer forms two layers.

The bottom layer of this distillate is added to the original lower layer and distilled under reduced pressure from a 1-l. modified Claisen flask (p. 130) provided with an air condenser and heated in an oil bath. The receiving flask is placed in a large funnel connected with the drain. A stream of cold water is run over the receiver. When a solid appears in the receiver, distillation is interrupted, the liquid distillate is discarded, and the distillation is continued. The product which distils at 114–118°/10 mm. (135–145°/50 mm.) (Note 4) weighs 310–340 g. (60–66 per cent of the theoretical amount, based on the furfural used). The yellow crystals melt at 37–39° and when melted show a sharp freezing point of 37° (Note 5).