38 DRS. E. SCHUNCK AND H. ROEMER ON SOME 



isomerides are interesting from a theoretical point of view, 

 since their internal constitution is still almost unknown, and 

 technically some of them are important from their occurring 

 along with artificial alizarine, to the tinctorial properties of 

 which, however, they do not contribute. The isomerides 

 of alizarine hitherto observed are the following : — 



1. Purpuroxanthine or Xanthopurpurine , a body first 

 obtained by Schiitzenberger from commercial purpuriaeand 

 afterwards prepared artificially by the action of reducing 

 agents on purpurine. It crystallizes in yellow needles, 

 soluble in alkalies with a blood-red colour. 



2. Isoalizarine, a constituent of extract of madder, de- 

 scribed by Rochleder, having properties very similar to 

 those of purpuroxanthine and perhaps identical with the 

 latter. 



3. Frangulic acid, a substance also resembling purpu- 

 roxanthine, obtained by Faust from franguline, a constituent 

 of the bark of Rhamnus frangula. 



4. Anthraflavic acid or Anthraflavine , a body accom- 

 panying the artificial alizarine of commerce, first described 

 by one of us in a paper read before this Society ^, and sub- 

 sequently examined by Mr. Perkin f. Its isomerism with 

 alizarine was established by Mr. Perkin, who was the first 

 to obtain it in a state of perfect purity. 



5. Anthraflavon, a product obtained by the action of 

 diluted sulphuric acid on oxybenzoic acid. The account 

 of this body given by its discoverers. Earth and Sennhofer, 

 shows that in most of its properties it closely resembles 

 anthraflavine. 



6. Quinizarine, obtained by Grimm by the action of 

 phthalic acid on hydroquinone. Of all the isomerides it 

 most resembles alizarine itself. Its alkaline solutions have a 



* Memoirs, 3rcl Series, vol. v. p. 227. 



f Journ. Chern. Soc. xxiv. p. 1109, and xx^i. p. 19. 



