Madder Dyeing. 55 



madder-yellow, and is a very inferior kind of dye, its other 

 properties may be omitted. The other constituents of 

 madder require no attention here, because they are totally 

 useless as dyes. But as they (especially Rubiacic acid) 

 may interest chemists and botanists, an account of them 

 will be reserved for Poggendorff 's Annalen. 



Criticism on Analyses of Madder. — No analyst has hitherto 

 obtained any of the preceding colours in a pure state. All 

 the substances described under the names of Extractive, 

 Woody madder-red, Erythrodanum, Alizarine, red colour- 

 ing matter of madder, pink colouring matter of madder, 

 and Xanthine, were indefinite mixtures of madder-purple, 

 madder-red, madder-orange, and madder-yellow. 



The extractive madder-red of Bucholz, is an extract 

 formed by means of water and spirit ; it contains, therefore, 

 such constituents of madder as are soluble in both. The 

 madder-red of Kuhlmann, formed by precipitating an 

 acpieous infusion of madder by means of sulphuric acid, 

 contains both of the red colouring matters in madder, and 

 besides madder-yellow which is also thrown down by sul- 

 phuric acid. In Robirmet's Alizarine obtained by sublimation 

 from the carbonaceous matter of madder, madder-purple is 

 finer than any of the preceding, but it is mixed with madder- 

 red, as appears by the re-action with potash ley which is 

 not pure cherry-red but purple red, from the mixture of 

 blue which potash forms with madder-red. 



The two colouring matters which Gaultier de Claubry 

 and Persoz have separated from madder, are mixtures, 

 principally, of madder-red and madder-purple. One of 

 them, termed the red principle, is separated by carbonate of 

 soda in a hot solution, and precipitated by an acid. It is a 

 reddish-brown matter with a splendent fracture. This is 

 obviously a mixture of madder-brown and madder-yellow. 

 But all the three pigments maybe contained in this brown 

 matter as carbonate of soda dissolves them very readily, 

 and also takes up the madder root. The fact of its insolu- 

 bility in alum shews the presence of madder-red. 



The second colouring matter, they term the pink-red 

 principle. It corresponds in many respects with madder- 

 purple. Its action with solution of alum and sulphuric acid 

 is tlie same, bu1 it< other characters, a compact mass with 



