MR. SCHUNCK ON RUBIAN AND ITS PRODUCTS OF DECOMPOSITION. 459 
unlikely however that the degree of temperature at which the decomposition is 
elfected may have something to do with it. It is probable that the lower the tempe- 
rature at which the acid acts on the rubian, the more rubianine and sugar are 
formed, and that at a higher temperature more alizarine, verantine and rubiretine are 
produced. In all experiments hitherto mentioned I have always obtained all five 
products of decomposition, though by no means in equal proportions, the alizarine 
being formed in the smallest quantity, the amount of rubiretine and verantine being 
somewhat greater, and the rubianine and sugar being produced in the largest quan- 
tity. In the course of this paper I shall have occasion to mention circumstances in 
which a still greater preponderance takes place in the amount of several of these 
substances formed over that of the others. Whether it would be possible to confine 
the decomposition of rubian entirely to one of these processes, or whether all three 
are essential, is a question of the highest importance, not so much in a theoretical, 
as a practical point of view. That beautiful substance, alizarine, is the only one of 
these products which is capable of yielding dyes. It is this body which in my opi- 
nion gives rise to all the beautiful colours for the production of which madder is 
employed. The others are not only useless, they are positively injurious, as I have 
shown on a former occasion. Though experimentally alizarine is formed in the 
smallest proportion, it is nevertheless theoretically possible to convert rubian entirely 
into alizarine, without the least quantity of the other substances being produced. 
From this point of view the other substances may be considered as formed at the ex- 
pense of alizarine. In fact, by adding together 1 eqiiiv. of verantine and 1 equiv. of 
rubiretine, and subtracting 1 equiv. of water, we obtain the elements of 2 equivs. of 
alizarine, for 
C„ H., 05 +C ,4 He 04=2(0,4 04 ) + HO. 
Also by adding together 1 equiv. of rubianine and 1 equiv. of sugar, and subtract- 
ing 16 equivs. of water, we obtain the elements of 4 equivs. of alizarine, for 
C44 H24 O20+C12 II]^2 Oi 2 = 4 (Cj 4 Hg 04)-!- 16 HO. 
If any chemist should succeed in changing rubian entirely into alizarine, an under- 
taking in which there is no occasion to despair of success, he would be the means of 
giving a great stimulus to many branches of manufacture and adding a large sum to 
the national wealth. 
