Dr. Schunck on Rubian and its Products of Decomposition. 355 



of rubian are usually more difficult to decompose than the first, 

 and an additional quantity of acid is therefore necessary to effect 

 their decomposition. The liquid retains to the last a light 

 yellow colour. I shall return to it presently. The orange- 

 coloured flocks are washed on the filter with cold water until 

 all the acid is removed. They now consist of four different 

 substances, three of which are bodies previously known, the 

 fourth one which has not hitherto been observed. The three 

 former are,— 1st, Alizarine; 2ndly, the substance which in my 

 former papers I have called alpha-resin, but to which I prefer 

 giving the name of Rubiretine ; 3rdly, the substance which I 

 formerly termed beta-resin, but I shall now call Verantine from 

 Verantia, the name applied to madder in the middle ages. The 

 fourth substance I shall denominate Rubianine. 



The presence of alizarine in this mixture is indicated by the 

 dark and beautiful colours which are produced when it is em- 

 ployed for dyeing a piece of mordanted cloth, and which con- 

 trast forcibly with the faint and dull tints produced by rubian. 

 It may also easily be separated from the other substances by 

 dissolving the mixture in alcohol, adding hydrate of alumina to 

 the solution, filtering, treating the alumina compound repeatedly 

 with a solution of carbonate of potash or soda, until nothing 

 more is dissolved by the latter, decomposing the alumina com- 

 pound with acid, and dissolving the residufe in alcohol, when on 

 evaporating the latter crystals of alizarine with its usual charac- 

 ters are obtained. In order however to obviate all objections 

 which might arise from the use of alkalies in regard to the effect 

 which the latter might be supposed to have in causing the for- 

 mation of the alizarine, I determined if possible to use acids and 

 salts only in the separation of the substances mentioned above. 

 Of the four substances contained in the orange-coloured flocks, 

 two, viz. alizarine and rubianine, are soluble in boiling water, 

 and may thereby be separated from the two others which are 

 insoluble in water. This method of separation is however te- 

 dious, on account of the sparing solubility of alizarine and 

 rubianine in boiling water. I therefore prefer using the fol- 

 lowing method. The orange-coloured flocks containing the 

 four substances are treated with boiling alcohol, in which they 

 dissolve with a dark reddish -yellow colour. The alcohol is 

 filtered boiling hot, and deposits on cooling a small quantity of 

 yellow crystalline particles, consisting chiefly of rubianine. The 

 treatment with alcohol is repeated as long as the latter acquires 

 a dark yellow colour. The greatest part of the rubianine remains 

 behind as a yellow or brownish-yellow crystalline mass, which 

 is treated repeatedly with boiling alcohol, in which the whole at 

 last dissolves, the greatest part again separating on the solution 

 2 A 2 



