Wakeman—Pigments of Flowering Plants. 
813 
0 ch 3 
0 ch 3 
Protocotoin. 
Methyl protocotoin. 
It will be seen from the above formulae that hydrocotoin is 
not, as the name implies, a reduced cotoin; but, rather a methyl 
cotoin, or monohydroxy-dimethoxy-diphenylmethanone. Methyl 
hydrocotoin is dimethyl cotoin, or trimethoxy-diphenylmeth- 
anone. Protocotoin is the methylene ether of a dihydroxy- 
methylcotoin and methyl protocotoin is a methylene ether of a 
dihydroxy-dimethylcotoin. 
The three compounds possessing free hydroxy groups form 
colored metallic derivatives. Further studies of cotoin, hydro¬ 
cotoin and their derivatives have been made by Henrich, * 7 Per¬ 
kin, 8 and others. 9 
II. A. 1. b.) Tetrahydroxy derivatives! of diphenyl methanone. 
Euxanthone, — Dihydroxy-4, 5-diphenylene methanone oxide, or 
Dihydroxy—4, 5-xanthone. 
CH 
CH 
Euxanthone exists partly in the free state and partly in com¬ 
bination with glucoronic acid in “purree,” or Indian yellow. 
Indian yellow is prepared from the urine of cattle fed upon 
T B., 32, p. 3423. 
8 Jr. Chem. Soc., 71, p. 1194. 
8 Moants., 18, p. 142; Ann., 282, p. 191; B., 28, p. 1549 ; Pharin. Post., 
