Dr. Schunck ofi Colouring Mailers. 209 



contained a large quantity of lime and a trace of magnesia. The 

 precipitate consisted of alumina, peroxide of iron, phosphate of lime, 

 and a trace of phosphate of magnesia. As it became probable from 

 the preceding reactions that the pinkish-white precipitate contained 

 oxalate of lime, the rest of it was treated with boiling dilute sulphuric 

 acid. The liquid after filtration was evaporated. It gave crystals 

 which were dissolved in alcohol to separate the sulphate of lime. 

 The alcohol on evaporation gave colourless crystals of pure oxalic 

 acid. Hence I infer that the following substances were extracted 

 from the madder by means of muriatic acid : — lime, magnesia, oxa- 

 late of lime, phosphate of lime, alumina and peroxide of iron. The 

 madder which had been subjected to the action of muriatic acid was 

 now well-washed with water, and then treated with boiling caustic 

 potash ley. A dark red solution was obtained, which, after being 

 strained through a cloth', produced, on being supersaturated with an 

 acid, a dark reddish-brown precipitate. This precipitate was thrown 

 on a filter, and well-washed with cold water, to remove the excess 

 of acid. 1 found this precipitate to dye mordanted cloth quite full, 

 and of the same colours as madder itself. There could therefore 

 be no doubt about its containing alizarine. Moreover on treating 

 the precipitate with boiling alcohol, a brownish-yellow liquid was 

 obtained, which left on evaporation a brownish-red residue. A 

 small portion of this residue being heated between two watch- 

 glasses, an abundance of orange- coloured crystals of sublimed aliza- 

 rine appeared on the upper glass. By treating the precipitate with 

 boiling water, and filtering boiling hot, the liquid deposited on 

 cooling orange-coloured flocks, which were impure alizarine, for they 

 dyed mordanted cloth, and after being dried and heated in a tube, 

 they gave a crystalline sublimate. The liquid gave on evaporation 

 pectic acid. That part of the precipitate which was left undissolved 

 by boiling water, was treated with a boiling solution of nitrate of 

 iron. The filtiered liquid gave, on the addition of muriatic acid, a 

 slight yellow precipitate, which was probably rubiacic acid from the 

 rubiacine of the precipitate. The greater part was insoluble in ni- 

 trate of iron. By treating the insoluble residue with boiling mu- 

 riatic acid, filtering, washing with water, and treating with boiling 

 alcohol, an abundance of beta-resin was procured. 



I infer from these experiments that the substances extracted from 

 madder by caustic potash, after exhaustion with boiling water and 

 treating with acid, previously existed in the root in combination with 

 lime and magnesia ; that these substances are not different from 

 those extracted by boiling water, viz. alizarine, rubiacine, resins and 

 pectic acid ; that the compounds of these bodies with lime and mag- 

 nesia are insoluble in water, and, with the exception of pectate of 

 lime, insoluble in caustic alkalies ; and that therefore, in order to 

 extract them by means of water or an alkali, it is first necessary to 

 remove the lime and magnesia with which they are combined by 

 means of an acid. 



I shall now proceed to give some further details concerning the 

 properties and composition of the substances extracted from madder. 



Phil. Mag. S. 3. Vol. 35. No. 235. Sept. 18*9. P 



