Wdkeman—Pigments of Flowering Plcmts. 
903 
IV. Pig men ts referable to hydrocarbons of the configura¬ 
tion SIX DOUBLE BONDS AND FOUR CYCLES. 
Pigments referable to methyl-anthracene. 
CH, 
i 
CH® 
QH CH OOH 
Chryiarobin 
CH CH * CH 
Methyl Anthracene 
Chrysarobin 1 —a trihydroxy derivative of methyl-anthracene 
occurs along with dichrysarobin, dichrysarobin methyl ether and 
another similar substance C 17 H 18 0 4 in Goa powder, obtained 
from Andira araroba, * 2 also along with chrysophanic acid and 
emodin in Rhamnus purshiana . 3 * 
Chrysarobin and chrysophanic acid were formerly thought to 
be identical but the work of Hesse 4 and later that of Jowett and 
Potter 5 have shown the latter to be a derivative of methyl 
anthraquinone, while the former is a derivative of methyl anth¬ 
racene. Chrysorobin is however readily oxidized to chryso¬ 
phanic acid. 
Chrysorobin crystallizes in small yellow tabular crystals and 
needles. It melts at 177°. It is easily soluble in chloroform, 
acetic acid and benzene, more difficultly soluble in alcohol and 
ether. It is insoluble in water and ammonia but soluble in 
sulphuric acid with a yellow color, insoluble in very dilute po¬ 
tassium hydroxide but soluble in a stronger solution with a yel¬ 
low color. Upon exposure to the air in alkaline solution it goes 
to chrysophanic acid. 
•Jr. Chem. Soe., 81, p, 1575. 
2 Ber., 11, p. 1603; Ann., 309, p. 32, Pharm. Jr., 5, p. 721. 
•Am. Pharm. Assoc., 52, p. 288 (1904). 
•Ann., 309, p. 32. 
•Jr. Chem. Soc., 81, p. 1573; 83, p. 1327. 
