880 Wisconsin Academy of Sciences , Arts , and Letters. 
II. A. 3.) Trihydroxy anthraquinone pigments. 
Of this group of dihydroanthracene derivatives two repre¬ 
sentatives are known in plants, trihydroxy -1, 2, 3- anthraquin- 
one or anthragallol, and trihydroxy -1, 2, 4- anthraquinone or 
purpurin. 
Anthragallol — Trihydroxy — 1 , 2, 3 — anthraquinone. 
O 
Anthragallol exists in the Chay root, Oldenlandia umbellata / 
in the form of three different dimethyl ethers, the dimethyl-1, 3- 
ether, known as the A ether, the dimethyl-1, 2-ether, known as 
the B ether, and the dimethyl-2, 3-ether, known as the C ether. 1 2 
Anthragallol itself forms orange red crystals and is an ex¬ 
cellent dye stuff, producing the anthracene brown of commerce. 
It’s monomethyl-3-ether no longer colors mordanted fabrics 
brown, but in shades of red similar to those produced by alizarin. 
The two dimethyl ethers have no dyeing properties. 
O 
Anthragallol dimethyl ether A, Dimethyl-1,-3-hydroxy-2- 
anthraquinone. 
1 Jr. Chem, Soc., 63, p. 1160; 91, p. 2066. 
a Jr. Chem. Soc., 67, p. 826. 
