alizarin

Derivative from anthraquinone. It is now prepared synthetically from anthracene. Alizarin crystallizes in dark red prisms and sublimes in orange-coloured needles, melting at 290°C/554°F. It is almost insoluble in water, but dissolves in alcohol.

It yields with metallic oxides magnificently coloured insoluble compounds called ‘lakes’, to which it owes its great value for dyeing purposes. Ferric oxide with alizarin gives a violet-black compound, chromium oxide a claret, calcium oxide a blue, and aluminium and tin give different shades of red.