noun.
A peculiar red coloring matter (C14H8O4) formerly obtained from madder, and extensively used as a dyestuff.
noun.
Commercial alizarin is sold in the form of a yellow paste containing 20 per cent. of dry substance, and, less frequently, as a dry powder. The dry substance in the paste is seldom pure alizarin, but contains varying amounts of flavopurpurin and anthrapurpurin, both of which have properties similar to alizarin. Natural alizarin derived from madder contains purpurin in addition to the above. The nature of the various commercial alizarins is often designated by suffixed letters or numbers. Thus alizarin I, alizarin P, and alizarin V are nearly pure alizarin and give blnish reds, while alizarin CA, alizarin G, etc., contain anthrapurpurin or flavopurpurin, or both, and give yellowish reds.