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).