130-23-4

1-Amino-8-hydroxynaphthalene-4,6-disulfonic acid [130-23-4]. (4-amino-5-hydroxynaphthalene-1,7-disulfonic acid), K acid, C10H9NO7S2, Mr 319.3: the acid sodium salt of 1-Amino-8-hydroxynaphthalene-4,6-disulfonic acid is very soluble in water, but the acid potassium salt is less soluble and is more easily salted out. K acid couples under acid and alkaline conditions in a similar manner to H acid.

1-Aminonaphthalene-4,6,8-trisulfonic acid paste is heated with sodium hydroxide liquor in an autoclave at 170℃ for 12 h, after which the mixture is added to excess dilute hydrochloric acid. After heating to remove sulfur dioxide, the product (including ca. 8 % of the isomeric 5-amino-2-hydroxynaphthalene-4,8-disulfonic acid) is completely precipitated by cooling and is isolated in 86 % yield. Purification of crude K acid may be effected by dissolving it in aqueous alkali and filtering off the less soluble 5,2,4,8-isomer before reprecipitating.

Notclassified