1,2-dihydroxyanthraquinone, a once-important orange-red dye,
originally extracted from the root of the madder (Rubia tinctorum)
but after 1871 made synthetically from anthraquinone
by a process developed by William Perkin
(1869). An earlier German synthesis (1868) was the first laboratory preparation
of a natural dyestuff. Alizarin is now little used.