206 Dr. Schunck on Colouring Matters. 



therefore consists of the following substances : — alizarine, rubiacine, 

 alpha-resin, beta-resin, riibian, pectic acid, and oxidized extractive 

 matter. 



I have examined the liquid filtered from the dark brown precipi- 

 tate produced by acids more minutely since making my last report. 

 Tf oxalic acid be used as the precipitant, the excess of acid may 

 afterwards be removed by chalk, without leaving any lime-salt in 

 solution. The liquid, which had a light yellow colour, was evapo- 

 rated on the sand-bath. During evaporation it gradually became 

 brown, and left at last a thick dark brown syrup, which never became 

 dry, however long it might be exposed to the heat of the sand-bath. 

 On redissolving this syrup in water, a considerable quantity of a dark 

 brown powder remained behind. On again evaporating the filtered 

 solution on the sand-bath, an additional quantity of this powder was 

 deposited, just as in the case of extractive matter. There can be no 

 doubt that this powder is formed by the action of the air, assisted by 

 heat, on some soluble substance contained in the liquid. On burning 

 a small quantity of the brown syrup in a crucible it swelled up 

 enormously, and gave off a quantity of empyreumatic products, 

 which burned with a flame, leaving at last a considerable quantity of 

 white ash ; this ash was partly soluble, partly insoluble in water. The 

 soluble part had a strong alkaline reaction ; it consisted of a trace of 

 lime and magnesia, and a great deal of potash, combined with 

 carbonic, sulphuric and muriatic acids. The insoluble part consisted 

 of carbonate of lime, carbonate of magnesia, a trace of alumina, phos- 

 phate of lime and phosphate of magnesia. The solution of the 

 brown syrup in water had an acid reaction. It gave no precipitate 

 or peculiar colour with a persalt of iron, and therefore contained no 

 tannic acid. The addition of alcohol produced no precipitate or 

 coagulate, and therefore there was no gum present. On adding 

 muriatic or sulphuric acid to it, and then boiling, it becanne dark- 

 coloured and deposited a green powder. Sugar of lead produced 

 in the solution a dirty brown flocculent precipitate, and basic ace- 

 tate of lead a still more copious precipitate. A considerable quan- 

 tity of the brown syrup was dissolved in water, and basic acetate 

 of lead was added until no more precipitate was produced. The 

 precipitate was separated by filtration, and washed with water. 

 The percolating liquid had a yellow colour. The excess of lead was 

 removed from it by sulphuretted hydrogtn, and the filtered liquid 

 was evaporated over sulphuric acid, since, if evaporated by the as- 

 sistance of heat, the substance contained in it was changed by the 

 air, became brown, and deposited a brown powder. After remain- 

 ing over sulphuric acid for several weeks, there was left a yellow 

 or brownish-yellow syrup like honey, which did not become dry. 

 This substance, though not pure (as it contained salts of lime, mag- 

 nesia and potash), I conceive to be identical with Kuhlmann's xan- 

 thine and Runge's madder-yellow. 



If madder contains sugar, it is evident that, provided the method 

 of operating described above be followed, it must be contained in 



