6857. Orange I

Nomenclature

CAS number: 523-44-4
4-[(4-Hydroxy-1-naphthalenyl)azo]benzenesulfonic acid monosodium salt; Tropaeolin OOO no. 1; C.I. Acid Orange 20; FD & C Orange I; Ext. D & C Orange 3; C.I. 14600; α-naphthol orange; sodium azo-α-naphtholsulfanilate.
C16H11N2NaO4S; mol wt 350.32.
C 54.86%, H 3.16%, N 8.00%, Na 6.56%, O 18.27%, S 9.15%.

Description and references

Prepared by coupling diazotized sulfanilic acid with α-naphthol: Colour Index vol. 4 (3rd ed., 1971) p 4065.

Chemical structure

Properties

Reddish-brown powder. Sol in water to orange-red soln, in alcohol to orange soln. Acids ppt the aq soln. Sodium hydroxide intensifies the red color of the aq soln. pH: 7.6 brownish-yellow; 8.9 purple.