962 NEUTRAL COLOURING MATTERS. 



that the bones of animals which have taken for some time 

 madder mixed with their food, are tinged red. 



The colouring matter of madder has also been examined by 

 Gaultier de Claubry and Persoz,* by H. Schlomberger,f and by 

 Dr. F; Runge. J From their inquiries it is certain that alizarin 

 is not the only or perhaps even the most important colouring 

 matter of madder. These different inquirers have extracted 

 various substances from madder, but do not agree in the mode 

 of representing its constitution ; as the purity however of these 

 substances was not tested by analysis, their definite character is 

 necessarily very doubtful. I can only enumerate here the 

 different colouring matters extracted from madder by Dr. Runge. 

 They are (1) Madder purple, dissolved out from madder, pre- 

 viously well washed with water between 56 and 70, by a strong 

 boiling solution of alum, and precipitated from the alum solution 

 by the addition of sulphuric acid. When purified it is a light 

 crystalline powder of a beautiful orange-yellow colour. When 

 used in excess it imparts to cotton impregnated with the alum 

 mordant, a deep reddish brown purple colour; but if on the 

 contrary the cotton be in excess, the colour is bright red. 



(2) Madder red, the alizarin of Robiquet and Colin, which ac- 

 cording to Runge may be sublimed a second 'time without 

 decomposition. It may be separated from madder purple, in 

 consequence of its insolubility in a strong solution of alum. 



(3) Madder orange, which is distinguished and separated from 

 the two former, by its little solubility in spirits. When in 

 excess it imparts to alumed cotton a bright orange colour. If 

 water be added to a hot solution of it in spirit, small crystals 

 separate, as with madder-red and madder-purple under the 

 same circumstances. (4) Madder yellow is remarkable for its 

 great solubility in water and its little affinity for cloth impreg- 

 nated with alum. It abounds in Dutch madder. (5) Madder 

 brown, another principle, which like the last has no value as a 

 dye stuff. 



The most fast and brilliant reds are obtained upon cotton by 

 means of madder, as also an equally stable and valuable purple ; 



* Ann. de China, et de Phys., t. 48, 72. 

 t Bulletins of the Industrial Society of Mulhausen. 



t Dr. R. I). Thomson's Records of Science, vol. 2, p. 452, and vol. 3, pp 44 

 and 135. 



