Dr. Schunck on Rubian and its Products of Decomposition. 501 



In the first part of this paper I have pointed out the possibility 

 which exists in theory of converting rubian entirely into alizarine, 

 to the exclusion of every other product of decomposition ; and 

 though I cannot say that I have approached much nearer to its 

 practical realization, still if, as the experiments just described 

 prove, the fermentative process whereby alizarine is formed is of 

 so plastic a nature as to be capable of yielding under different 

 circumstances, sometimes more, sometimes less, occasionally none, 

 of the latter substance, then the prospect of our being able so to 

 modify it as to lead to the formation of a much larger quantity 

 of alizarine from a given quantity of rubian than is at present 

 possible, becomes less distant. 



The experiments which I shall now describe were made in 

 order to ascertain the effect produced on rubian by other fer- 

 mentative substances besides that contained in madder itself. 



I first took a solution of rubian and mixed it well with a solu- 

 tion of albumen made from white of egg. The mixture was 

 allowed to stand in a moderately warm place for two months, 

 but though the albumen had entered into a state of putrefaction, 

 the rubian was still for the most part undecomposed, as was 

 evident from the taste and colour of the liquid. At the bottom 

 of the vessel there was found a small quantity of a dark reddish- 

 brown deposit, which was collected on a filter. On treating this 

 deposit with boiling alcohol, the latter acquired a red colour, 

 and left on evaporation a small quantity of a yellow bitter sub- 

 stance, soluble in water, which only differed from rubian in 

 being somewhat viscid. The remainder of the dark brown de- 

 posit I treated with a mixture of muriatic acid and alcohol, when 

 it immediately became almost white, while the substance which 

 had coloured it dissolved in the alcohol with a yellow colour. 

 The alcohol was filtered from the insoluble part, which was pro- 

 bably merely modified albumen, and evaporated to dryness, when 

 it left a reddish-yellow, uncrystalline residue. This residue was 

 impure ahzarine, for it gave on being heated in a tube a crystal- 

 line sublimate, it dissolved in caustic alkali with a violet colour, 

 and its alcoholic solution became purple on the addition of ace- 

 tate of copper. In the reddish-brown deposit it was doubtless 

 contained in combination with some base, perhaps lime. The 

 greatest part of the rubian remained in solution mixed with the 

 albumen. The solution was slowly evaporated to dryness, when 

 it left a red transparent substance like gum or varnish, which 

 was treated with boiling alcohol. The alcohol acquired a reddish- 

 yellow colour, and left on evaporation a yellowish-red, deliques- 

 cent, bitter residue, consisting apparently of rubian mixed with 

 some nitrogenous substance. It was entirely soluble in water 

 with a reddish colour. The solution gave with acetate of lead a 



