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Chromotropic acid, scientific name "1,8-dihydroxynaphthalene-3,6-disulfonic acid". Molecular formula C10H8O8S2, molecular weight 320.30. The appearance of chromotropic acid is white needle-like crystal (containing two-molecule crystal water), soluble in water, green in case of ferric chloride solution. The monosodium salt and disodium salt of chromotropic acid are white or crystalline powders, very soluble in water, insoluble in salt water. The aqueous solution of trisodium salt is neutral. The aqueous solution of tetrasodium salt is alkaline. It is prepared by sulfonation, nitrification, reduction, alkali fusion and acidification of β-naphthalenesulfonic acid. It is used to manufacture azo dyes and anthraquinone dyes, and is used as a reagent.

Chinese name: Chromotropic acid

Chinese aliases: chromic acid, 1,8-dihydroxy naphthalene-3,6-disulfonic acid, 4,5-dihydroxy-2,7-naphthalene disulfonic acid, coloric acid

English name: Chromotropic acid

English aliases: 4,5-Dihydroxy-2,7-naphthalene disulfonic acid; 1,8-Dihydroxynaphthalene-3,6-disulfonic acid

CAS Number: 148-25-4

Molecular formula: C10H8O8S2

Molecular weight: 320.30

Uses of Chromotropic Acid:

1. Used in the manufacture of azo dyes and anthraquinone dyes. Chromotropic acid is an intermediate of the dye's acidic medium dark blue. This dye can be used for wool fabric dyeing and is obtained by coupling 4-chloro-o-aminophenol with chromotropic acid after diazotization.

2. Used as a reagent to determine chromium, titanium and formaldehyde, and to detect chromium, mercury, silver, titanium, chlorate, formaldehyde, nitrate and nitrite.