In a 1-l. flask are placed 50 g. (0.38 mole) of benzoyl cyanide (p. 112) and 500 ml. of concentrated hydrochloric acid (sp. gr. 1.18). The mixture is shaken occasionally until the solid is dissolved completely and is then allowed to stand at room temperature for 5 days (Note 1). At the end of this time the clear yellow solution is poured into 2 l. of water and extracted with one 400-ml. portion and three 250-ml. portions of ether. The ether is removed by distillation from a steam bath, and the residual oil is placed in a vacuum desiccator containing phosphorus pentoxide and solid sodium hydroxide and allowed to remain there until dry (Note 2). The yield of crude solid acid melting from 57° to 64° is about 55–56 g. (96–98%). The crude acid is dissolved in 750 ml. of hot carbon tetrachloride, and 2 g. of Norit is added (Note 3). The solution is filtered and allowed to cool to room temperature and then cooled in an ice-water mixture until crystallization is complete. The solid acid is filtered with suction, and the solvent remaining on the crystals is removed by placing the product in a vacuum desiccator for about 2 days. The yield of slightly yellow benzoylformic acid melting at 64–66° is 42–44 g. (73–77%) (Note 4).