Wakeman—Pigments of Flowering Plants. 
887 
It will be seen from the above that ernodin not only resembles 
chrysophanic acid in constitution but closely accompanies it in 
the plant as well. Ernodin occurs both free and as a gluco- 
side. It crystallizes in silky needles of an orange red color 
which melts at 250°. It is soluble in alcohol, amyl alcohol, 
and acetic acid, slightly soluble in benzene, and soluble in 
alkalies and ammonia with a red color. With sulphuric acid 
it gives an intense red solution which turns yellow, separates 
a flocculent precipitate, and becomes colorless upon standing. 
A considerable number of derivatives of ernodin have been 
prepared. 
The principal investigators of ernodin are listed below. 
Combes, — Bull, de Soc. Chem., (4) 1, p. 800. 
Hesse, — Ann., 284, p. 194; 309, p. 41. 
Krassowski, — Jr. d. russ. phys. chem., Ges., 40, p. 510; Chem. 
Centrlbl. 1919, I. p. 773. 
Le Prince, — C. r., 129, p. 60. 
Liebermann, — B., 9, p. 1775; 21, p. 436. 
Oesterle, — Arch. d. Pharm., 237, p. 699. 
Oesterle and Tisza, — Arch. d. Pharm., 246, p. 112, 432; Chem. 
Centrlbl. 1908, I. p. 1548; II. p. 1441. 
Tschirch and Pool, — Arch. d. Pharm., 246, p. 315. 
Warren — Jr., Chem. Soc., 10, p. 100. 
Rochleder, — B., 2, p. 373. 
Frangulin. 1 —A glucoside of ernodin, known as frangulin, oc¬ 
curs in the bark of RJiamnus frangula. 2 It crystallizes in lemon 
yellow crystals which melt at 226°. It is insoluble in water 
and in ether, soluble in alcohol and in benzene. Upon hydroly¬ 
sis it yields ernodin and rhamnose. 3 
Polygonin .—A second glucoside of ernodin, known as poly- 
gonin, occurs in the root of Polygonum cuspidatum . 4 It 
crystallizes in fine orange yellow needles which melt at 202°- 
203°. It is insoluble in water, difficultly soluble in alcohol, 
also in hot water. When hydrolized it yields ernodin and a 
sugar. 
»C. r., 134. 
a Rep. f. Pharm., 104, p. 151; Ann., 104, p. 77. 
3 Ann., 165, p. 230. 
4 Jr. Chem. Soc., 67, p. 1084. 
