Лако-красочные материалы — производство

A solution is made of 141.5 grams (1.0 mole) of 2,6-ehlorotoluidine in 1 liter of water and 450 grams of 30 per cent hydrochloric acid by heating to 80°C. and then cooling to 30° with stirring. Enough ice is then added to lower the temperature to 5°. Some of the hydrochloride crystallizes out. Diazotization is carried out using the equivalent of 70 grams of 100 per cent sodium nitrite dissolved in 200 cc. water (diazo­tization in general, see page 241 ff.). The temperature should not exceed 16°, and the volume should be about 1.4 liters. The diazo­tization is considered complete when a reaction with starch-iodide paper persists after 10 minutes. The diazonium solution is added, dur­ing the course of 30 minutes, to a cuprous chloride solution prepared by adding sulfurous acid to a solution of 200 grams of copper sulfate and 200 grams of salt in 800 cc. water and removing the excess S02 by boiling.

Cuprous chloride solution can also be prepared in the following way: 100 grains of copper sulfate is dissolved in 500 cc. water, and 50 grams of zinc dust is added to precipitate all the copper. The supernatant liquid is poured off and the cop­per treated with dilute hydrochloric acid to dissolve out all the zinc. 100 grams of salt is added, then a solution of 100 grams of copper sulfate, and the mixture is heated at 80° for 15 minutes.

Alternatively, a hydrochloric acid solution of cupric chloride is boiled under reflux with -waste copper (e. g., turnings) until it is decolorized, and the resulting solution is poured off from the excess copper.

The cuprous chloride solution is best heated in a glazed crock by running in steam, and the diazonium solution is run in with mechanical stirring. In order to prevent loss of dichlorotoluene, the crock must be well covered and the temperature should not exceed 95°. The mixture is transferred to a 4-liter flask and the dichlorotoluene steam distilled out. The material coming over weighs about 141 grams, or 88 per cent of the theoretical amount. This product is not sufficiently pure. It is washed in a separatory funnel with 5 per cent of its weight of eulfuric acid (66° B6), then with water, and finally twice with 40 per cent sodium hydroxide solution. The material is then distilled. It boils at 185-192°.