Indigo carmine

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General
Indigo Carmine
Other names	5,5'-indigodisulfonic acid sodium salt
Molecular formula	C₁₆H₈N₂Na₂O₈S₂
Molar mass	466.36 g/mol
Appearance	purple solid
CAS number	[860-22-0]
Properties
Density and phase	? g/cm³, Solid
Solubility in water	10 g/L(25°C)
Melting point	>300°C
Boiling point	?°C
Hazards
EU classification	?
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Indigo Carmine, or 5,5'-indigodisulfonic acid sodium salt, is a ph indicator with the chemical formula C₁₆H₈N₂Na₂O₈S₂.

[edit] Uses

The primary use of Indigo carmine is as a pH indicator. It is blue at pH 11.4 and yellow at 13.0. A common aqueous solution is 0.2%.

Indigo Carmine (pH indicator)
below pH 11.4		above pH 13.0
11.4	↔	13.0

[edit] Health concerns

Indigo carmine is harmful to the respiratory tract if swallowed. It is also an irritant to the skin and eyes. Proper laboratory cautions (Lab coat, gloves, goggles) are advised.