Karamu is rich in dying properties including alizarin and purpurin. "Rubia tinctorum", together with alizarin, purpurin and other anthraquinone derivatives. Madder lake contains two organic red dyes&colon; alizarin and purpurin. Purlytin is a purpurin; a degradation product of chlorophyll. Alizarin was discovered before purpurin, by heating the ground madder with acid and potash. Purpurin is normally not coloured, but is red when dissolved in alkaline solutions. Purpurin is somewhat harder than normal glass but can be easily cut and polished. Purpurin fluoresces yellow to red under ultraviolet light, while synthetic alizarin slightly shows violet. Purpurin is a fast dye for cotton printing and forms complexes with various metal ions. Purpurin is also called verantin, smoke Brown G, hydroxylizaric acid, and C.I. 58205.