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



Good madder contains sufficient ferment to convert an ex- 

 cess of xanthine into available colouring matter. I made 

 several experiments with different quantities, and found 20 

 per cent, additional to be the greatest quantity madder would 

 convert. 



With a view to place the utility of xanthine in dyeing be- 

 yond all doubt, I made the following experiments : — 



No. 1. Two equal portions of the same madder were taken, 

 and an equal quantity of water at 120° F. added to each; to 

 one, one-tenth of its weight of dry xanthine was added : I 

 kept them at the same heat for half an hour, then put in each 

 an equal quantity of mordanted cloth of the same pattern, 

 and heated gradually on a sand-bath, observing that the heat- 

 ing of the two dyeings progressed equally. At the end of an 

 hour and a half, when the heat was 180° F., I removed the 

 dyed cloth, washed and dried it: the piece dyed with the 10 

 per cent, additional xanthine was much darker and better 

 dyed than that with madder alone ; the whites were equally 

 good. 



No. 2. The same experiment was repeated with 20 per cent, 

 additional xanthine with increased advantage. 



No. 3. Two equal weights of madder were taken : to one 

 a certain quantity of boiling water was added, and the mixture 

 allowed to cool ; to the other portion the same quantity of cold 

 water was added. Two equal quantities of mordanted cloth 

 were then introduced, the temperature being the same in 

 each, and the dyeings made with the same precautions as 

 before. That dyed with the portion treated with cold water 

 was immeasurably superior to the one treated with boiling 

 water, having fine solid colours; those of the other being 

 pale, meagre and dirty-looking. The whites of the cold 

 one were also good ; those of the hot very bad. The liquors 

 after dyeing were saved and examined, being filtered from the 

 woody matter; that from the hot portion contained abundance 

 of xanthine, whilst that from the other contained none. 



No. 4. The preceding experiment was repeated with a little 

 variation. Lest by the action of boiling water it might have 

 happened that the alizarine was merely thrown into an inso- 

 luble condition, and consequently the madder weakened in 

 power, I resolved to convert the residue of each dyeing into 

 garancine, and dye with it some more mordanted cloth ; I 

 therefore, after taking out the dyed cloth, added to each the 

 same quantity of sulphuric acid and boiled half an hour, then 

 filtered, and washed each with the same quantity of water. The 

 •*-i!w*i two garancines were then put into an equal quantity of water, 

 and mordanted cloth dyed in them as before. Now if the 



