Mr. J. Higgin on the Colouring Matters of Madder. 287 ? v</»W 4 



chloric acid, when a few yellow flocks fell, which when washed \JuAh *&*> 

 were found to be pure rubiacine. When mordanted cloth •■ fW" 

 was attempted to be dyed with this powder, only the faint ^i ^ 

 shades of rubiacine were obtained. The deep yellow filtrate 

 from the rubiacine, when left to stand several hours, deposited ^^^ 

 no more flocks, and ultimately became green, as does solution ft^T*(#ifej 

 of pure xanthine under the same circumstances. "i£o«5#ul«i 



Another portion of the filtrate from precipitation by acetate v m^u^ 

 of lime was diluted a little with water, and allowed to stand 

 about four hours; it had then lost the intense bitterness of ^ (C yl-~~ 

 taste, and retained only that of acetate of lime. On acidula- ;• 

 tion by hydrochloric acid, copious yellow flocks fell, which 

 when filtered out left the filtrate a pale yellow ; they were ffk£C*~J 

 proved to be rubiacine, and had no tinctorial power. The fljl^o^ 

 yellow filtrate was examined for xanthine, but only a ver yct^XQ33 

 small quantity was found. tfv tty 



Another portion of the original filtrate was set aside for 



about eight hours, when a quantity of reddish-orange powder K 



had subsided, and the supernatant liquor was much diminished v VtfcXvCx 

 in intensity of colour. The filtered precipitate, after treatment q , !£*• /, 

 with dilute acid and washing, had a vei'y strong tinctorial . 

 power; it was dissolved in alcohol, diluted a little with water, (jk <UwW< 

 and lime-water added ; a dark red precipitate appeared, sus- v v 

 pended in a red liquid. The filtered precipitate, washed with '.' \> 



boiling water and decomposed by hydrochloric acid, was found ,\ 



filtrate from it, acidulated with hy-"' .^. ' a 

 drochioric acid, gave yellow flocks of rubiacine. The quantity' 1 



to be pure alizarine ; the 

 drochioric acid, gave yell 



of alizarine in the powder was greater than that of rubiacine;!^, 

 the liquor from which it had subsided was acidulated with 

 hydrochloric acid, when a further quantity of powder was 

 obtained, consisting of both rubiacine and alizarine, but more 

 of the former. The filtrate from it was a pale yellow, and 

 contained no traces of xanthine. 



In these experiments, the madder liquor, from which all 

 alizarine had been taken and which had then no power to dye, 

 by spontaneous action acquired a further portion of alizarine, 

 and consequently recovered its power of dyeing. As the 

 xanthine had totally disappeared during the process, the for- I 

 mation of alizarine must have been at its expense. The action 

 is not however direct, as by stopping the process before any 

 precipitation has occurred, only rubiacine is obtained, whilst, 

 as before, xanthine has disappeared. It is evident, then, that 

 the xanthine has become first rubiacine and afterwards ali- 

 zarine. 



This reaction does not result from oxidation, since I have t 

 found it to take place equally well in vacuo; and as numerous 



