Mr. J. Higgin on the Colouring Matters of Madder. 293 



met with any resinous matter; with a view further to test 

 this, I boiled madder in alcohol repeatedly, till it became an 

 ash-gray, and no more colouring matter was given to the 

 alcohol: the solutions were mixed. Dilution with water in 

 any proportion did not produce any milkiness, even after 

 standing some time, as must have been the case had any 

 resins been dissolved by the alcohol. The solution, added to 

 alum liquor and boiled, gave a perfectly clear solution, with- 

 out any resinous matter being rejected. The alcoholic solu- 

 tion, evaporated to dryness in contact with air, and again 

 treated with alcohol, left a brown substance, insoluble in 

 boiling alcohol, ammonia, and caustic soda ; some more was 

 left on evaporating the second solution to dryness, and treat- 

 ing with alcohol. The powder seemed formed at the expense 

 of the xanthine, as on examination very little could be found 

 in the third solution; this was acidulated with sulphuric acid 

 and diluted with water, and the resulting flocks washed and 

 boiled in alum liquor. This time a small quantity of resinous 

 matter was rejected, which could not have been in the original 

 solution. 



This experiment also proves that the colouring matter of 

 madder is all free, none being united to lime, as it is capable 

 of being so perfectly exhausted by alcohol as to leave only 

 an ash-gray powder. The compound of alizarine with lime 

 is perfectly insoluble in boiling alcohol. Boiling alum solu- 

 tion also decolorizes madder more rapidly and better than 

 alcohol. If, however, madder be boiled in water, the colour- 

 ing matter cannot afterwards be wholly separated by alcohol ; 

 a large quantity remains in a state not soluble in water or 

 alcohol ; this results partly from alizarine becoming united 

 to lime during the boiling, and partly from the woody fibre 

 acting as a mordant, and withdrawing alizarine from solution; 

 woody fibre having a great affinity for that colouring matter, 

 and when introduced into its boiling solution becoming dyed 

 a dark red. I have sometimes found that, after all lime-salts 

 have been removed from madder by an acid, if dried at too 

 high a temperature, very little colouring matter is given to 

 water, and mordanted cloth receives very faint shades of 

 colour; the madder in this condition is a deep red; hot acid 

 separates alizarine again from the fibre. This fact explains 

 why garancine is spoilt by too high drying. 



Having thus detailed my experiments on normal madder, 

 I will briefly describe those which I made on that preparation 

 of it called garancine. 



I find it to contain only one colouring matter, alizarine, 



