Alizarin Red S

Alizarin Red S (also known as C.I. Mordant Red 3, Alizarin Carmine, and C.I 58005. ) is a water-soluble sodium salt of Alizarin sulfonic acid with a chemical formula of. Alizarin Red S was discovered by Graebe and Libermann in 1871. In the field of histology alizarin Red S is used to stain calcium deposits in tissues, and in geology to stain and differentiate carbonate minerals.

Uses
Alizarin Red S is used in histology and histopathology to stain, or locate calcium deposits in tissues. In the presence of calcium, Alizarin Red S, binds to the calcium to form a Lake pigment that is orange to red in color. Whole specimens can be stained with Alizarin Red S to show the distribution of bone, especially in developing embryos. In living corals alizarin Red S has been used to mark daily growth layers.

In geology, Alizarin Red S is used on thin sections, and polished surfaces to help identify carbonate minerals which stain at different rates.