2241. Chromotropic Acid

Nomenclature

CAS number: 148-25-4
4,5-Dihydroxy-2,7-naphthalenedisulfonic acid; 1,8-dihydroxynaphthalene-3,6-disulfonic acid.
C10H8O8S2; mol wt 320.30.
C 37.50%, H 2.52%, O 39.96%, S 20.02%.

Description and references

Prepn from 4-chloro-5-hydroxy-2,7-naphthalenedisulfonic acid: DE 147852 (1904 to BASF); alternate methods: Frdl. 3, 460-466.

Chemical structure

Derivative

Dihydrate.

Nomenclature

CAS number: 5808-44-6
C10H8O8S2.2H2O; mol wt 356.33.
C 33.71%, H 3.39%, O 44.90%, S 18.00%.

Properties

White needles, soluble in water.

Derivative

Disodium salt dihydrate.

Nomenclature

CAS number: 5808-22-0
C10H6Na2O8S2.2H2O; mol wt 400.29.
C 30.00%, H 2.52%, Na 11.49%, O 39.97%, S 16.02%.

Properties

White needles or leaflets. Very sol in water.

Use

Analytical reagent for the determn of nitrate and formaldehyde. Intermediate for azo dyes.