9072. Tartrazine

Nomenclature

CAS number: 1934-21-0
4,5-Dihydro-5-oxo-1-(4-sulfophenyl)-4-[(4-sulfophenyl)azo]-1H-pyrazole-3-carboxylic acid trisodium salt; C.I. Acid Yellow 23; 3-carboxy-5-hydroxy-1-p-sulfophenyl-4-p-sulfophenylazopyrazole trisodium salt; 5-hydroxy-1-(p-sulfophenyl)-4-[(p-sulfophenyl)azo]pyrazole-3-carboxylic acid trisodium salt; hydrazine yellow; C.I. 19140; FD & C Yellow No. 5; C.I. Food Yellow 4.
C16H9N4Na3O9S2; mol wt 534.36.
C 35.96%, H 1.70%, N 10.48%, Na 12.91%, O 26.95%, S 12.00%.

Description and references

Prepn: US 2457823 (1949 to Ilford); Freeman et al., J. Assoc. Off. Agric. Chem. 33, 937 (1950). See also: Colour Index vol. 4 (3rd ed., 1971) p 4132.

Chemical structure

Properties

Bright orange-yellow powder. Freely sol in water. The aq soln is not changed by HCl but becomes redder with sodium hydroxide.

Use

As a dye for wool and silks; as colorant in food, drugs and cosmetics. In biochemistry as an adsorption-elution indicator for chloride estimations.