Alizarin

Alizarin, the colouring matter used in the dyeing of Turkey red, exists in the madder root as a glucoside, which, when boiled with acids or alkalis, gives glucose and alizarin. But in 1869 Graebe and Liebermann discovered a method of manufacturing it from the coal-tar product anthracene; this synthesis being the first instance of the artificial production of a natural colouring matter. The manufacture of alizarin is now one of the most important branches of the coal-tar colouring industry, and threatens to put an end to the growing of madder root. For the ten years preceding this discovery, the annual imports of madder into Britain averaged over £1,000,000; ten years later, they had sunk to £24,000. The 14,000 tons of alizarin produced in 1880 were reckoned equal in colouring power to 126,000 tons of madder. The value of the former was £1,568,000; that of the madder would have been £5,670,000; that is, the artificial dye costs less than a third of the price of the natural. But the artificial dye is inferior to the natural in permanence. Alizarin is represented by the formula, $C\_\{14\}H\_6O\_2(OH)\_2$. See ANTHRACENE.