[ 282 ] 



XLIV. On the Colouring Matters of Madder. 

 By James Higgin, Esq., Manchester*. 



r I^HE various analyses I have made of madder have led me 

 -*- to the same conclusion as Dr. Schunck, in his recent 

 valuable paper "On the Substances contained in Madder," viz. 

 that there are three colouring matters capable of isolation — 

 xanthine, a yellow ; an orange, which he names rubiacine ; 

 and alizarine, a red. To this latter alone he ascribes all the 

 tinctorial power of madder, an opinion from which I am com- 

 pelled to differ ; and the object of my present paper is to show 

 that, under proper circumstances, the other two colouring 

 matters have a great influence on its dyeing properties. 



I believe the difference in our results to have arisen from 

 the use, in one case, of boiling water to extract the principles, 

 and in the other of cold or tepid water ; the temperature having 

 a remarkable influence on the products of extraction. 



I will here state the method I employ to separate from each 

 other the three colouring matters $ observing that, when sepa- 

 rated, they differ little in their properties from those described 

 by Dr. Schunck. I will afterwards show that, as existing in 

 madder, and in the condition in which they are applied in 

 dyeing, peculiar reactions take place, which, as far as 1 know, 

 have never been described before. 



The same method was employed for various sorts of mad- 

 der, viz. Dutch, French, Turkey, &c, with the same results, 

 varied of course in the amount and proportion of colouring 

 matters. 



I put the madder on a conical calico filter, and wash well 

 with boiling w ater till the liquor comes away only faintly 

 ^9j\o^Jji-i coloured and has no particular taste. I object altogether to 

 t}~ boiling madder in water, as I find that substances are obtained 



by so doing which have no existence in normal madder, being 

 the result of decomposition; and consider the action ought to 

 be as brief as possible. The extract by hot water, when cold, 

 is acidulated with sulphuric acid, which causes a flocculent 

 precipitate, which is collected on a filter. The precipitate con- 

 tains rubiacine and alizarine, with some pectine. The deep 

 yellow filtrate contains all the xanthine, slight traces of aliza- 

 rine and rubiacine, some sugar, and the various organic and 

 inorganic salts. 



The filtrate is neutralized with carbonate of soda, and a 

 very small quantity of hydrate of alumina added ; the mixture 

 is digested at a temperature of 130° F. for about half an hour, 



* Communicated by the Author, having been read at the Meeting of the 

 British Association held at Swansea, August 9, 1848. 



JL- - 



