104 MR. SCHUNCK ON RUBIAN AND ITS PRODUCTS OF DECOMPOSITION. 
the influence of all the reagents with which madder itself under ordinary circum- 
stances is brought into contact, I find myself entirely confirmed in my opinion. I 
should indeed think it unnecessary to add anything confirmatory of the conclusions 
which must suggest themselves at once from the perusal of the preceding pages, but 
as Messrs. Wolff and Strecker have made it one of the special objects of their 
investigation to prove the existence of more than one colouring matter in madder, I 
think it may not be out of place here to add a few remarks to show how, in my 
opinion, these chemists, as well as their predecessors, have been misled, and also to 
give an account of some experiments still further confirmatory of the opinion which 
I have always held. 
The second colouring matter, which, according to the chemists just mentioned, 
exists in madder in addition to alizarine, and which has received at various times 
the names of purpurine, madder-purple, and oxylizaric acid, possesses, according to 
those observers, the property of being easily soluble with a red colour in boiling 
alum liquor. Wolff and Strecker assert that this substance is peculiarly a product 
of fermentation, and in order to prepare it, they mix madder with water and yeast, 
allow the mixture to stand in a warm place until the effervescence produced by 
fermentation has ceased, and the liquid has acquired a strong acid reaction and 
contains alcohol, after which they strain the liquid through a cloth, wash the mass 
on the cloth with water, and then treat it with boiling alum liquor. From the 
bright red solution a substance separates on cooling in red flocks, which, as well as 
the orange-coloured flocks produced by adding sulphuric acid to the liquid, consist, 
according to them, entirely of purpurine without any trace of alizarine. They purify 
it by crystallization from alcohol. Now I have shown above that the fei mentation 
of madder, which is in fact synonymous with the fermentation of rubian, is due to 
the action of a peculiar substance, which I have called erythrozym, on rubian ; that 
the action of this substance is very rapid; that it is not accompanied by any disen- 
gagement of gas ; that it is terminated long before any effervescence or any acid 
reaction of the liquid begins to appear ; that the products of the action do not differ 
essentially from those due to the action of acids and alkalies ; that the formation of 
alizarine in about the same proportion as when acids or alkalies are employed is one 
of the results of the process, and that yeast exerts no decomposing power on rubian 
whatever. Hence it necessarily follows, that if the purpurine of Wolff and JStrecker 
be not found as such among the products of the fermentation of rubian, it must consist 
of a mixture of two or more of those products. 
Now I have mentioned in the first part of this paper, that though alizarine and 
verantine are both perfectly insoluble in boiling alum liquor when acted on sepa- 
rately, yet that when a mixture of both is employed, the mixture is found to be 
soluble in alum liquor with the colour characteristic of purpurine. Hence I con- 
cluded that purpurine is in fact a mixture of those two substances, a view with 
which all that is mentioned regarding purpurine completely coincides. I may mention 
