SYNONYMS	INDIGO CARMINE* C. I. FOOD BLUE 1 * FD & C BLUE 2 * INDIGOTINE * ACID BLUE 74
DEFINITION	Indigo Carmine consists essentially of a mixture of disodium 3,3' dioxo - 2,2' -bi-indolylidene-5,5' - disulfonate, and disodium 3,3' - dioxo-2,2' - bi-indolyldene-5,7' -disulfonate and subsidary colouring matters together with sodium chloride and/or sodium sulfate as the principal uncoloured components.
	Indigo Carmine is described as the sodium salt. The calcium and the potassium salt are also permitted.
CLASS	Indigoid
COLOUR INDEX NO.	73015
EEC NUMBER	E-132
EINECS	212-728-8
CHEMICAL NAMES	Disodium 3,3' -dioxo-2,2'-bi-indolylidene-5,5'-disulfonate
CHEMICAL FORMULA	C16H8N2Na2O8S2
MOLECULAR WEIGHT	466.36
ASSAY	Content not less than 85% total colouring matters, calculated as the sodium salt;
	disodium 3,3' -dioxo-2,2' -bi-indolylidene-5,7' -disulfonate : not more than 18%
DESCRIPTION	Dark - blue powder
IDENTIFICATION
a. Spectrometry	Maximum in water at ca 610 nm .
b. Blue solution in water
PURITY	Not more than 0.2%
Water Insoluble matter
Subsidiary colouring matters	Excluding disodium  3,3' -dioxo-2,2' -bi-indolylidene-5,7' -disulfonate :not more than  1.0%
Organic compounds other than colouring matters	[Isatin-5-sulfonic acid / 5-sulfoanthranilic acid / Anthranilic acid ] - Total not more than 0.5%
Unsulfonated primary aromatic amines	Not more than 0.01% (Calculated as aniline)
Ether extractable matter	Not more than 0.2% under neutral conditions
Arsenic	Not more than 3 mg/kg.
Lead	Not more than 10 mg/kg.
Mercury	Not more than 1 mg/kg.
Cadmium	Not more than 1 mg/kg.
Heavy metals (as Pb)	Not more than 40 mg/kg.