Indigo carmine

Indigo carmine, also called indigotine, is a water-soluble synthetic blue dye used as a food colorant, pH indicator, and medical diagnostic dye.

Food coloring: Substances added to foods to impart or restore color. Indigo carmine is used as a blue food colorant, designated E132 in the European Union.
Indigo dye: A family of blue dyes based on the indigo molecular framework. Indigo carmine is a sulfonated, water-soluble derivative of the indigo chromophore.
Indigotine: A common name for indigo carmine, the disodium salt of a sulfonated indigo compound. It is the alternative name used for the same dye, not a separate colorant.
Tartrazine: A synthetic yellow azo dye used as a food colorant and laboratory reagent. Unlike indigo carmine’s blue hue, tartrazine produces yellow coloration and belongs to a different dye class.
Synthetic dye: A colorant manufactured through chemical synthesis rather than obtained directly from natural sources. Indigo carmine is produced synthetically rather than extracted as a natural blue pigment.
pH indicator: A substance that changes color over a range of acidity or alkalinity. Indigo carmine changes from blue to yellow across strongly alkaline pH conditions.
Chromophore: The part of a molecule responsible for absorbing particular wavelengths of light and producing color. Its conjugated molecular system absorbs visible light, giving indigo carmine its blue appearance.
Indigo: A deep blue dye and pigment whose principal coloring molecule is poorly soluble in water. Indigo carmine is derived from the indigo structure but dissolves readily in water.
Brilliant blue FCF: A synthetic bright-blue food dye also known as FD&C Blue No. 1. It is another water-soluble blue food colorant, but has a different chemical structure and regulatory identity.
Indigo synthesis: Industrial and laboratory methods for producing indigo through chemical reactions. The history of synthetic indigo provides the chemical and industrial context for indigo-derived dyes.

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