In a 16-l. earthenware jar are placed 250 g. (4.7 moles) of technical ammonium chloride, 8 l. of water, and 500 g. (416 cc., 4.1 moles) of nitrobenzene. The mixture is stirred vigorously by means of a mechanical stirrer, and 620 g. (8.1 atoms) of zinc dust of 85 per cent purity is added (Note 1) during the course of fifteen to twenty minutes (Note 2). As the reduction proceeds, the temperature rises to 60–65°. Stirring is continued for fifteen minutes after all the zinc dust has been added, at the end of which time the reaction is complete, as indicated by the fact that the temperature of the mixture ceases to rise.

While still hot, the solution is filtered with suction in order to remove the zinc oxide, which is washed with 1 l. of hot water. The filtrate is placed in an enameled pan, saturated with salt, about 3 kg. being required, and cooled to 0° by being placed in an ice-salt mixture. The phenylhydroxylamine, which crystallizes out in long, light yellow needles (Note 3), is filtered by suction. The yield of crude product varies considerably, depending upon the amount of salt solution present, but averages 350–400 g. This corresponds to 275–300 g. (62–68 per cent of the theoretical amount) of actual phenylhydroxylamine, as determined by its separation from inorganic materials by solution in ether (Note 4).

Since phenylhydroxylamine deteriorates upon storage, it is generally used promptly, as illustrated in the preparation of cupferron (p. 177). The oxalate is somewhat more stable.