Rubia. Rubia tinctorum. Dyer's madder.
Rubia. Garance, Fr. Krappwurzel, Färberröthe, G. Robbia, It. Rubia de tintoreros, Granza, Sp.—Under this name the U. S. P. formerly recognized madder, Rubia tinctorum L. (Fam. Rubiaceae.) The root of dyer's madder is perennial, and consists of numerous long, succulent fibers, varying in thickness from the size of a quill to that of the little finger, and uniting at the top in a common head, from which also proceed side-roots that run near the surface of the ground, and send up many annual stems. The quadrangular stems are furnished with short prickles by which they adhere to neighboring plants, upon which they climb. The leaves are arranged in whorls at the joints of the stem. The flowers are small, yellow and terminal. The plant is a native of Southern Europe. The root, which is dug up the third summer, enters commerce either in the form of the whole root deprived of its cuticle, or in the form of a reddish-brown powder. Madder has a weak, peculiar odor, and a bitterish, astringent taste, and imparts these properties, as well as a red color, to water and alcohol. It contains as its most important constituent alizarin, C14H6(OH)2O2, and with it as coloring matter of secondary importance purpurin, C14H5(OH)3O2. Besides these two technically important constituents there have been recognized pseudopurpurin, an orange dye color, and a yellow one (xanthopurpurin). These coloring matters, however, are probably decomposition products from glucosides existing in the fresh plant. Thus, alizarin is known to result along with glucose from the treatment with dilute acids of rubianic or ruberythric acid, C26H28O14, according to the reaction:
- C26H28O14 + 2H2O = C14H8O4 + 2C6H12O6
The most interesting of the coloring substances is the alizarin, and this is now termed dihydroxy-anthraquinone, C14H8O14. This occurs as orange-red crystals, almost insoluble in cold water, but readily soluble in alcohol, ether, the fixed oils, and alkaline solutions. The alcoholic and aqueous solutions are rose-colored; the ethereal, golden yellow; the alkaline, violet and blue when concentrated, but violet-red when sufficiently diluted. A beautiful rose-colored lake is produced by precipitating a mixture of the solutions of alizarin and alum. Alizarin was recognized by Graebe and Liebermann in 1868 as a derivative of anthracene, C14H10—a hydrocarbon contained in coal tar—and in the same year they elaborated a method for preparing it commercially from anthracene. Upon this arose rapidly a great chemical industry, and the cultivation of madder, has, of course, decreased correspondingly.
Madder is used in amenorrhea and dropsy, and when taken into the stomach imparts a red color to the milk and urine, and to the bones of animals, without sensibly affecting any other tissue. The effect is observable most quickly in the bones of young animals, and in those nearest the heart. Under the impression that it might effect some change in the osseous system, it has been prescribed in rachitis, but without favorable result. Dose, about half a drachm (2.0 Gm.), repeated three or four times a day.