228 DR. E. SCHUNCK ON ANTHRAFLAVIC ACID. 



scale (for the use of dyers and printers) by their process is 

 very far from being pure alizarine — so much so, indeed, 

 that some chemists are inclined to doubt its perfect iden- 

 tity with the natural substance. Its solution in caustic 

 alkali, for instance, has not the fine violet colour of a 

 solution of pure alizarine, but is more or less purple or 

 even red. There can be no doubt, however, that the dif- 

 ferences observed between the natural and artificial pro- 

 ducts are mainly due to impurities accompanying the 

 latter. A few simple experiments are sufficient, indeed, 

 to prove that artificial alizarine, as ordinarily prepared, is 

 always accompanied by other substances, some of which 

 are coloured while others are colourless or nearly so. My 

 object on the present occasion is to describe one of these 

 substances, and to point out the relation in which it stands 

 to alizarine. 



My attention was first directed to this subject in conse- 

 quence of some experiments which I made to obtain ali- 

 zarine from anthracene according to the directions of 

 Graebe and Liebermann. I was surprised to find that, in 

 spite of all the precautions taken, I always obtained be- 

 sides alizarine a notable quantity of another body, also 

 crystalline, but differing essentially from the former by 

 its dissolving in alkalies with a yellow colour. About the 

 same time Mr. Perkin, who, as is well known, is engaged 

 in the manufacture of alizarine on a large scale, sent me 

 for examination a specimen of the residue obtained by 

 him in evaporating the mother-liquors of alizarine. This 

 residue, which was a crystalline reddish-brown mass 

 soluble in alkalies with a cherry-red colour, I found to 

 contain, in addition to alizarine, a quantity of a substance 

 apparently identical with that which I had previously 

 obtained directly from anthracene. I afterwards found 

 the same body, though in much smaller quantities, in 

 commercial alizarine, both in that manufactured by the 



