[1]) is a water-soluble sodium salt of Alizarin sulfonic acid with a chemical formula of C14H7NaO7S.

[3] Alizarin Red S is used in histology and histopathology to stain, or locate calcium deposits in tissues.

[4] Whole specimens can be stained with Alizarin Red S to show the distribution of bone, especially in developing embryos.

[4] In living corals alizarin Red S has been used to mark daily growth layers.

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