A 1500-cc. flask is fitted with a two-holed rubber stopper carrying a glass tube which ends below the middle of the flask. The second hole is fitted with a common glass stopcock (Note 1). To the flask is added 500 cc. of 6 N aqueous ammonia (sp. gr. about 0.95), and 100 g. (0.55 mole) of p-nitrophenylacetic acid (p. 406) is now slowly introduced, with shaking. The flask is then placed in an ice bath, and the mixture saturated with hydrogen sulfide, the temperature being held below 50°.

The stopper is removed from the reaction flask, and the solution of ammonium p-aminophenylacetate gently boiled under the hood until nearly all the excess hydrogen sulfide and ammonia have escaped. The solution changes from a dark orange-red to a pale yellow. The deposited sulfur is filtered off by suction, and 40 cc. of glacial acetic acid rapidly stirred into the hot filtrate. The p-aminophenylacetic acid which crystallizes out weighs 69–70 g., but it is contaminated with a small amount of free sulfur. On evaporating the mother liquor to a small volume, about 5 g. more can be obtained. The crude material is recrystallized from 4 l. of distilled water, 69–70 g. (83–84 per cent of the theoretical amount) of a product which melts at 199–200° being thus obtained (Note 2).