878 Wisconsin Academy of Sciences, Arts, and Letters. 
Alizarin, the first known pigment of this group was discovered 
by Colin and Robiquet 1 in 1826 in the rhizorn of Ruhia tine- 
torium where it exists principally as the glucoside ruberythric 
acid. This glucoside was isolated by Rochleder 2 and Schunk 3 
almost simultaneously in 1851. The relationship of alizirin 
to anthracene was recognized by Graebe and Liebermann 4 when 
they obtained anthracene by the reduction of alizarin. After 
a further study of the properties of alizarin they were able to 
pronounce it a derivative of anthraquinone. In 1869 they ef¬ 
fected a synthesis of the compound. 
Alizarin occurs in the rhizorn of Oldenlandia umbellata , 5 and 
Rubia tinctorium. 1 
Alizarin crystallizes in red needles which melt at 289°-290°. 
It sublimes in orange red needles. It is easily soluble in alco¬ 
hol and carbon disulphide but difficultly soluble in water. It 
dissolves in alkaline solutions with a violet blue color. Sul¬ 
phuric acid dissolves it unchanged: Alizarin combines with 
most mordants. To cotton mordanted with aluminum it gives 
a garnet red color; with tin, a light red; with iron, violet; with 
chromium, a brownish purple color. 
o- Methyl alizarin -—The methyl ether of alizarin occurs with 
alizarin in the root of Oldenlandia-umbellata and in Morinda 
longiflora . 7 It crystallizes in orange colored crystals which melt 
at 178°. It does not dye mordanted fabrics, but it dissolves 
in solutions of the alkalies, also barium and calcium hydroxide 
with a red color. 
Hystazarin, 2, 3 - Dihydroxy anthraquinone. 
O 
O 
'Ann. chim. phys., (2) 34, p. 225. 
2 Ann., 80, p. 321. 
2 Ann.. 81, p. 336. 
* Ber., 2, p. 332. 
* Proc. Chem. Soc., 23, p. 288. 
•Jr. Chem. Soc.. 64, p. 1160. 
* Jr. Chem. Soc.. 91. p. 1913 ; Proc. Chem. Soc., 23, p. 248. 
