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Indigo carmine

Indigo carmine


Other names	5,5'-indigodisulfonic acid sodium salt
Identifiers
CAS number	860-22-0
Properties
Molecular formula	C₁₆H₈N₂Na₂O₈S₂
Molar mass	466.36
Appearance	purple solid
Melting point	>300 °C
Solubility in water	10 g/L (25 °C)
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.

Additional recommended knowledge

Correct Test Weight Handling Guide: 12 Practical Tips

Don't let static charges disrupt your weighing accuracy

Uses

The primary use of Indigo carmine is as a pH indicator. It is blue at pH 11.4 and yellow at 13.0. . It is also used in the manufacturing of capusles as a soluble pigment.

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

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.