2240. Chromotrope 2B

Nomenclature

CAS number: 548-80-1
4,5-Dihydroxy-3-[(4-nitrophenyl)azo]-2,7-naphthalenedisulfonic acid disodium salt; C.I. Acid Red 176; p-nitrobenzeneazochromotropic acid sodium salt; C.I. 16575.
C16H9N3Na2O10S2; mol wt 513.37.
C 37.43%, H 1.77%, N 8.19%, Na 8.96%, O 31.17%, S 12.49%.

Description and references

Prepn from diazotized p-nitroaniline and chromotropic acid, see: Colour Index vol. 4 (3rd ed., 1971) p 4097.

Chemical structure

Properties

Reddish-brown powder. Sol in water with a yellowish-red color. Insol in alcohol.

Use

As a dye; as a reagent for boric acid or borates.