Madder, the root of several species of genus Rubia. European madder largely descents from dyer’s madder (Rubia tinctorum) native to southern Europe, which is also cultivated in North America and Australia; Rubia peregrina supplies the Levantine madder and the madder of Provence, Rubia munjista the East Indian one; other species are cultivated in the West Indies, South America, etc. In addition to the usual plant components (Alsatian madder up to 16 percent sugar), madder contains glycosides which, under the influence of peculiar ferments, slowly decompose into sugar and pigment. This is why madder improves in storage. As it absorbs the elements of water, ruberythric acid C26H28O14 splits into alizarin C14H8O4 and sugar, another glycoside supplies the purple in C14H8O5; madder also contains orange-red pseudo purpurine, yellow purpuroxanthin and isalizarine.
When raw madder is used, the substances present alongside the pigment have a disruptive effect, and half of the pigment remains in the root, bound to lime and magnesia. Therefore, preparations are used that contain the pigment in a purer and more concentrated form. The madder is macerated with water and a little sulfuric acid for 12-15 hours, then pressed, dried and ground (madder flowers). The washing water is rich in sugar, can be fermented and then produces spirit (madder spirit) during the distillation. The madder flowers give a nicer, more solid violet, a lustrous pink, and the white base remains purer, but the pigment is only half used. To prepare garancine, ground madder is extracted in cold water, pressed, mixed with slightly diluted sulfuric acid, then washed, dried and ground. To prepare garancin, ground madder is extracted with cold water, pressed, mixed with slightly diluted sulfuric acid, then washed, dried and ground. 100 parts of this preparation correspond to 500 to 600 parts of madder. It produces quite vivid and shiny colours and in addition to a pure white base. Similar preparations are: Garanceux, Pinkoffin (Alizarine commerciale), Madder Coal, Kolorin. The madder extracts from madder root, garancin and madder charcoal have 20-70 times the saturation of madder, generally produce very true colours with a very nice white and are used in particular in the printing of fabric. This includes Azale, Rochlederin, etc., which consist of almost pure alizarin.
Madder cultivation was once of great importance, but since Graebe and Liebermann succeeded in producing alizarin from coal tar in 1868, artificial alizarin has almost exclusively been used.
Source: Meyers Großes Konversations-Lexikon, 6. Auflage 1905–1909