48 Dr. Schunck on the Colouring Matters of Madder. 



come of a bright yellow colour. They are then dissolved in boiling 

 alcohol, from which they separate on cooling in yellow transparent 

 plates and needles having a strong lustre. Alizarin prepared in 

 this way has the following properties : — It has a pure yellow colour 

 without any admixture of red. It may be volatilized without leaving 

 any residue. The vapour crystallizes on cooling in beautiful yellow 

 plates and needles. It suffers hardly any change if exposed to the 

 action of the most powerful reagents. It dissolves without change 

 in cold concentrated sulphuric acid. Concentrated nitric acid hardly 

 affects it even on boiling. It is not changed by chlorine. It is in- 

 soluble in water, but soluble in alcohol with a yellow colour. It 

 dissolves in alkalies with a beautiful purple colour. Its compounds 

 with the alkaline earths are red and slightly soluble in water. Its 

 compounds with the earths and metallic oxides are insoluble in water 

 and exhibit different shades of red. It imparts no colour to cloth 

 mordanted with acetate of alumina or oxide of iron, on account of 

 its insolubility in M'ater. Very little alizarin is obtained in this way ; 

 perhaps one 1 gr. from 1 lb. of madder, though there is more of it 

 contained in the root. 



I shall now shortly describe two other colouring matters which I 

 have obtained from madder. If an extract of madder be made with 

 hot or cold water, and a strong acid, such as muriatic or sulphuric 

 acid, be added to the fluid, a dark reddish-brown flocculent preci- 

 pitate is produced. This precipitate was separated by filtration and 

 washed until the acid was removed. On being treated with boiling 

 water, a part of it dissolves with a brown colour. On adding a few 

 drops of acid to the filtered solution a dark brown precipitate is 

 produced, which seems to me to be a peculiar colouring matter 

 similar in its properties to orcein, hematin and other soluble colour- 

 ing matters. It dissolves in alkalies with a red colour, and is capable 

 of imparting very lively colours to mordanted cloth. As far as I 

 am aware it has not been described in the former investigations of 

 this subject, though it seems to be the principal substance concerned 

 in the production of the colours for which madder is used in the 

 arts. I have however only examined it very slightly as yet. The 

 residue left behind by the boiling water was treated with dilute 

 boiling nitric acid, by which every trace of the preceding substance is 

 destroyed, and the residue itself acquires a bright yellow colour 

 and a more powdery consistence. This yellow powder contains 

 alizarin, as is shown by its giving crystals of that substance on 

 being gently heated; in fact it contains all the alizarin of the root, 

 but mixed with another substance of an amorphous natui'e but very 

 similar properties, from which it is difficult to separate it. By crys- 

 tallising from alcohol no separation can be effected, as they are both 

 about equally soluble in that menstruum. They also behave in a 

 similar manner towards the alkalies, the earths and most of the me- 

 tallic oxides. I have hitherto only succeeded in discovering one 

 method of separating them, which is as follows : — The mixture of the 

 two is dissolved in a little caustic potash. To the solution is added 

 perchloride of iron, which produces a dark reddish-brown precipi- 



