To a solution of 1200 g. (4.8 moles) of crystallized copper sulfate and 400 g. (6.9 moles) of sodium chloride in 4 l. of water at 60–70° is added a concentrated solution of 200 g. (1.7–1.8 moles) of (90–95 per cent) sodium bisulfite (prepared if desired by saturating a solution of 100 g. of sodium carbonate with sulfur dioxide). The white precipitate of cuprous chloride is filtered off, sucked dry as rapidly as possible, and suspended in a mixture of 2 l. of water and 1.5 l. of concentrated hydrochloric acid (sp. gr. 1.19) (Note 1).

In the meantime, 552 g. (4 moles) of good commercial m-nitroaniline, melting at 110° or above (Note 2), is dissolved in a mixture of 500 cc. of hydrochloric acid (sp. gr. 1.19) and 1 l. of hot water; 1100 cc. of hydrochloric acid (sp. gr. 1.19) is then added, and the solution is cooled rapidly, with stirring. It is then surrounded with a freezing mixture, and diazotized at a temperature below 1° by adding, with constant stirring, a solution of 288 g. (4 moles) of technical (95 per cent) sodium nitrite in 700 cc. of water, care being taken to avoid adding an excess over that necessary to produce a distinct reaction with starch-iodide paper (p. 49). This point is reached when all but about 25 cc. of the nitrite solution has been added; the addition requires about one and one-half hours. The cold solution is now filtered in order to remove some amorphous insoluble matter; this solid, when dry, weighs 50–55 g.

The clear filtrate, which has only a pale yellow color, is now run, with stirring, into the cuprous chloride solution in a 12-l. flask, while the temperature is kept at 25–30° (Note 3). A somewhat sticky precipitate first forms, which later becomes crystalline; nitrogen is evolved in a continuous stream. The addition requires about thirty minutes. The mixture is then warmed on a steam bath under an efficient reflux condenser until the evolution of nitrogen ceases. It is then distilled in a current of steam (using the apparatus described on p. 479) until no more chloronitrobenzene passed over; 9–10 l. of distillate collects during this process (Note 4). When quite cold, the water is decanted off, and the solid shaken with 1–2 l. of 1 per cent sodium hydroxide solution at 50°. The mixture is again allowed to cool, and the light yellow alkaline solution is decanted from the solid product, which is then collected on a filter, washed with a little cold water, dried, and distilled under reduced pressure. It boils completely at 116–117°/12 mm. or 124–125°/18 mm., and the distillate solidifies to a pale yellow solid which melts at 44–45° and weighs 430–450 g. (68–71 per cent of the theoretical amount).