Sulfuric Acid → Anthrarufin

Participants

Reaction Steps

140 Parts of 1,5-dihydroxy-4,8-dinitro-anthraquinone-2,6-disulphonic acid in the form of 270 parts of an aqueous paste, containing sulphuric acid and sodium bisulphate and obtained by sulphonation and nitration of 81 parts of 1,5-dihydroxy-anthraquinone, are entered with stirring at 40° into 700 parts of water. 60 Parts of hydrazine hydrate are then added dropwise over the course of 90 minutes. The pH of the reaction mass immediately rises from 1,7 to 4 and then to 6.5. This value is kept by the dropwise addition of 45 parts of 30% aqueous hydrochloric acid. The temperature of the reaction mass is then raised to 80°. 10 Parts of hydrazine hydrate are then added dropwise over the course of 10 minutes. The pH is kept at 5.8 to 6 by the addition of 20 parts of 30% aqueous hydrochloric acid. The mass is stirred at 80° for 10 minutes. 58 Parts of 30% aqueous sodium hydroxide solution are subsequently added dropwise over the course of 5 minutes, whereby the pH is adjusted to 8. The precipitate is suction filtered, washed with 2000 parts of aqueous 10% sodium sulphate solution and 5000 parts of aqueous 5% sodium sulphate solution, and dried at 120°. 129 Parts of 1,5-dihydroxy-4,8-diamino-anthraquinone-2,6-disulphonic acid, containing 80% of free disulphonic acid, are obtained.

Provenance & Evidence