9775. Tropaeolin O

Nomenclature

CAS number: 547-57-9
4-[(2,4-Dihydroxyphenyl)azo]benzenesulfonic acid monosodium salt; C.I. Acid Orange 6; sodium p-(2,4-dihydroxyphenylazo)benzenesulfonate; sodium azoresorcinolsulfanilate; C.I. Food Yellow 8; C.I. 14270; Resorcinol Yellow; Yellow T; Tropeolin O; Tropaeolin R; Chrysoine; Gold Yellow.
C12H9N2NaO5S; mol wt 316.27.
C 45.57%, H 2.87%, N 8.86%, Na 7.27%, O 25.29%, S 10.14%.

Description and references

Prepd from resorcinol and a p-sulfobenzenediazonium salt, followed by reaction with an inorganic sodium salt: Sisley, Bull. Soc. Chim. Fr. [3] 25, 869 (1901). See also: Colour Index vol. 4 (3rd ed., 1971) p 4064. Brief review: H. J. Conn's Biological Stains, R. D. Lillie, Ed. (Williams & Wilkins, Baltimore, 9th ed., 1977) p 106.

Chemical structure

Properties

Brown powder. Sol in water with reddish-yellow color; sol in alcohol.

Use

As indicator. pH: yellow 11, orange-brown 12.7. Occasionally used as plasma stain.