Лако-красочные материалы — производство

14.3 grams (0.1 mole) of a-naphthylamine is dissolved by boiling in a mixture of 280 cc. water and 10 cc. concentrated hydrochloric acid, and the solution is cooled under the tap with shaking so that the naph — thylamine hydrochloride crystallizes out in as finely divided a state as possible. An additional 75 cc. concentrated hydrochloric acid is added, the solution is cooled further, and then 250 grams of crushed ice is added. With vigorous shaking, 7.1 grams of dry, powdered sodium nitrite is now added in me portion, and shaking is continued for the short time required for all of the naphthylamine hydrochloride to go into solution. After 15 minutes, the clear, nonfoaming, light brownish — yellow solution, which should still give a very weak nitrite test, is fil­tered to remove the slight residue. The filtrate is run directly into a stirred, ice-cooled solution of 27 grams of sodium l-naphthol-5-sulfonate (96 per cent pure) in 200 cc. water. The mixture is cooled in ice and

stirred for 30 minutes. The yellow-brown, crystalline precipitate is then filtered off with suction, washed with ice water, and mixed with 500 cc. ice water. The resulting suspension is cooled in ice, and to it is added, with vigorous stirring, 80 cc. 2 N soda solution, the addition being made in such a way that each drop of the soda solution is immediately dis­persed throughout the mixture. The coupling reaction is completed when all of the soda solution has been added. The reaction mixture at this point should give a distinct blue test with litmus paper, but should not turn phenolphthalein paper red. The cooling bath is now removed, and the mixture is warmed slowly to 80-90°C. with stirring, whereupon the originally dark brown, gelatinous dye rapidly becomes crystalline. Saturated, calcium-free salt solution, in an amount equal to one tenth of the volume of the reaction mixture, is now added, and the mixture is filtered hot with suction. The precipitate is first washed thoroughly with hot, calcium-free salt solution (about 5 per cent), and then the salt is washed out with cold water. The product is dried in a steam heated oven. The yield is about 37 grams or 92 per cent of the theoretical amount.