In a 1-l. round-bottomed flask is placed 100 g. (0.62 mole) of p-nitrobenzyl cyanide (p. 396). A solution of 300 cc. (5.4 moles) of concentrated sulfuric acid (sp. gr. 1.84) in 280 cc. of water is prepared, and two-thirds of this solution is poured onto the p-nitrobenzyl cyanide. The mixture is shaken well, until the solid is all moistened with the acid. Any solid material adhering to the walls of the vessel is now washed down into the liquid with the remainder of the acid; the flask is attached to a reflux condenser, then set, without shaking, over a 10-cm. hole in a large sheet of asbestos board which rests on a tripod, and heated until the mixture boils (Note 1). The boiling is continued for fifteen minutes (Note 2).

The reaction mixture, which becomes rather dark, is diluted with an equal volume of cold water and cooled to 0° or below. The solution is filtered; the precipitate is washed several times with ice water and then dissolved in 1600 cc. of boiling water (Note 3). This solution is filtered as rapidly as possible through a large folded filter, preferably with a steam funnel (Note 4). In spite of all precautions, however, some solid usually separates on the filter. This must be redissolved in a minimum quantity of boiling water, and this solution then filtered into the main solution. The p-nitrophenylacetic acid separates in long, pale yellow needles, which melt at 151–152°. The yield is 103–106 g. (92–95 per cent of the theoretical amount).