Rubia tinctorum
Rubia tinctorum, the rose madder or common madder or dyer's madder, is a herbaceous perennial plant species belonging to the bedstraw and coffee family Rubiaceae. Description The common madder can grow up to 1.5 m in height. The evergreen leaves are approximately 5–10 cm long and 2–3 cm broad, produced in whorls of 4–7 starlike around the central stem. It climbs with tiny hooks at the leaves and stems. The flowers are small (3–5 mm across), with five pale yellow petals, in dense racemes, and appear from June to August, followed by small (4–6 mm diameter) red to black berries. The roots can be over a metre long, up to 12 mm thick and the source of red dyes known as rose madder and Turkey red. It prefers loamy soils (sand and clay soil) with a constant level of moisture. Madder is used as a food plant by the larvae of some Lepidoptera species including the hummingbird hawk moth. Uses It has been used since ancient times as a vegetable red dye for leather, wool, cotton and silk. For dye production, the roots are harvested after two years. The outer red layer gives the common variety of the dye, the inner yellow layer the refined variety. The dye is fixed to the cloth with help of a mordant, most commonly alum. Madder can be fermented for dyeing as well (Fleurs de garance). In France, the remains were used to produce a spirit. The roots contain the acid ruberthyrin. By drying, fermenting, or a treatment with acids, this is changed to sugar, alizarin and purpurin, which were first isolated by the French chemist Pierre Jean Robiquet in 1826. Purpurin is normally not coloured, but is red when dissolved in alkaline solutions. Mixed with clay and treated with alum and ammonia, it gives a brilliant red colourant (madder lake). The pulverised roots can be dissolved in sulfuric acid, which leaves a dye called garance (the French name for madder) after drying. Another method of increasing the yield consisted of dissolving the roots in sulfuric acid after they had been used for dyeing. This produces a dye called garanceux. By treating the pulverized roots with alcohol, colorine was produced. It contained 40–50 times the amount of alizarin of the roots. The chemical name for the pigment is alizarin, of the anthraquinone-group, and was used to make the alizarine ink in 1855 by Professor Leonhardi of Dresden, Germany. In 1869, the German chemists Graebe and Liebermann synthesised artificial alizarin, which was produced industrially from 1871 onwards, effectively ending the cultivation of madder. In the 20th century, madder was only grown in some areas of France. The plant's roots contain several polyphenolic compounds, such as 1,3-Dihydroxyanthraquinone (purpuroxanthin), 1,4-Dihydroxyanthraquinone (quinizarin), 1,2,4-Trihydroxyanthraquinone (purpurin) and 1,2-dihydroxyanthraquinone (alizarin). This last compound gives it its red colour to a textile dye known as Rose madder. It was also used as a colourant, especially for paint, that is referred to as madder lake. The substance was also derived from another species,