294- Mr. J. Higgin on the Colouring Matters of Madder. 



and to be remarkably free from rubiacine, xanthine, pectine, 

 and the nitrogenous matter. In no way have I been able to 

 separate any of these substances from the specimens I have 

 tried. The peculiar utility of garancine consists in all sub- 

 stances being removed which have an injurious influence on 

 the action of alizarine. From the experiments of Schunck 

 it appears, that any of these substances, when used in conjunc- 

 tion with pure alizarine, injure the dyed colour and stain the 

 whites. In the making of garancine, they are rendered inert, 

 as the following experiments will attest. 



1. I took xanthine, dissolved it in a little sulphuric acid, 

 and heated the solution for some time. From being a bright 

 orange, it grauually became a dark brown ; when diluted with 

 water, a brown powder separated, wh'ch, when dry, was in- 

 soluble in any menstruum except sulphuric acid. 



2. I treated rubiacine in the same way, and obtained 

 exactly the same results. 



3. Alizarine treated the same way was not decomposed 

 even by long heating, but remained as a rich red solution, 

 from which water threw down all colouring matter. 



4. I then made a mixture of alizarine, rubiacine, and xan- 

 thine, dissolved in sulphuric acid, and heated some time. 

 The solution gradually became da<k brown; and on addition 

 of water a brown powder fell, which when washed and dried, 

 was a soft velvety substance, possessing an intense tinctorial 

 power; hot alcohol separated aU the alizarine and left the 

 dark brown powder obtained from xanthine and rubiacine. 

 This compound of alizarine and the brown matter may be 

 considered as pure garancine freed from woody fibre. 



As to the greater proportional dyeing power of garancine 

 over madder, I coincide in the opinion of Dr. Schunck, that 

 the lime-salts being removed, no alizarine can remain com- 

 bined with lime, and that in garancine dyeing all colouring 

 matter is used up, whilst in madder only two-thirds are used. 



The foregoing series of experiments, though perhaps not 

 possessing the completeness they might have, warrant us, I 

 think, in drawing the conclusion, that aU the colouring matter 

 in madder springs primarily from xanthine, an opinion held 

 by Decaisne, who observed that fresh madder roots contained 

 only a deep yellow fluid, and acquired a granular appearance 

 only during the process of drying. 



