Mr. J. Higgin on the Colouring Matters of Madder. 289 



this well with alcohol to free it from colouring matter which 

 it carries down with it. It is now a brown matter, which, when 

 burnt, emits the smell of burning flesh, and leaves a large 

 quantity of ash; it probably also contains pectine and woody 

 matter, which must inevitably be pressed through the cloth. 

 It is insoluble in water. Boiled with caustic soda, it gives the 

 characteristic smell that all proteine compounds do with an 

 alkali. Nitric acid heated with it forms a yellow mass, which 

 gives to ammonia a red colour ; an acid precipitates therefrom 

 a yellow powder, which has the properties of xanthoproteic 

 acid. The mass is easily soluble in slightly alkaline liquors. 

 It appears in every respect to be similar to coagulated vege- 

 table albumen. I have not been able to extract any nitroge- 

 nized substance soluble in alcohol from madder, and believe 

 this substance to be the only one containing nitrogen. 



I have in the foregoing experiments described the changes 

 undergone in cold water ; but, as in all other fermentations, 

 a proper increase of temperature is attended with more rapid 

 results. The temperature I find best is from 120^ to 130° F. 

 Water added to madder and the mixture kept at that tempe- 

 rature, rapidly changes in appearance and taste; it gradually 

 becomes redder, loses its bitter taste, and becomes more sweet: 

 the yellow disappears, and the liquid, tested from time to time 

 by dropping on white calico, is found constantly diminishing in 

 intensity of colour. In about half an hour all xanthine has dis- 

 appeared; and the madder, if examined, isfoundtocontain abun- 

 dance of rubiacine and alizarine : if it was rich in xanthine, 

 there will be at this stage a preponderance of rubiacine, so much 

 so as to give an orange solution with boiling alum liquor, 

 without much shade of pink. If the fermenting action be con- 

 tinued, the rubiacine is found gradually diminishing, and the 

 alizarine proportionably increasing : the action is complete in 

 about two hours and a half; and if the madder be now tried, #X«-(im**vu 

 only a small quantity of rubiacine is found; and the colour of r ~\, - ( 

 the alum solution is pink, but not quite so pure as that pro- 

 duced by pure alizarine, as I have never been able to get rid G* ***' 

 of the last portions of rubiacine by this process ; a small frac- 

 tion of the quantity originally found still remains. JkcL.vJ'&t 



The quantity of water required for this reaction is small, 

 though it will take place in however dilute a solution. I have 

 frequently done it with perfect success by making madder 

 into a thin paste with water, either heating or not, and adding 

 water to replace that evaporated. If this process be continued 

 too long, the alizarine formed attaches itself to the fibre, and 

 the madder will now give out little colour to water;. treatment 

 with hot acid brings it again into a soluble condition. 



