MR. SCHUNCK ON RUBIAN AND ITS PRODUCTS OF DECOMPOSITION. 453 
These analyses show that verantine, like many substances, the acid character of which 
is not well-marked, combines with bases in various and complicated proportions. 
It appears therefore that verantine differs from alizarine by containing 1 equiv. 
more of oxygen. According to Debus, the same relation exists between alizarine and 
his oxylizaric acid. He gives for alizarine the formula C 30 Hjo O 9 , and for oxylizaric 
acid Cjs H 5 O 5 , so that 2 quivs. of the latter contain 1 equiv. more oxygen than 1 equiv. 
of the former. If my view of the composition of these substances be the correct one, 
the relation subsisting between the two is still more simple. Nevertheless I have 
some hesitation in asserting that verantine is to be considered as a higher oxide of 
the same radical as alizarine, or in supposing that it may be formed by oxidation 
from the latter. Its formation is due, as I shall presently show, not to any process 
of oxidation, but rather to the splitting up of an atom of rubian into two bodies. 
Rubiretine , — This substance is identical with that which I formerly called the alpha- 
resin of madder, from which it does not differ in properties. It is obtained as a dark 
brown, opake, resinous mass, brittle when cold, but becoming soft and almost melting 
in boiling water. On being heated to a higher degree, it melts completely without 
being decomposed. It is generally found to be mixed with a small quantity of veran- 
tine, from which it may be separated by solution in cold alcohol, which leaves the 
greatest part of the verantine behind ; I have however found it impossible to remove 
the last traces of that substance. It is almost insoluble in boiling water. Its solution 
in alcohol is dark yellow. It dissolves in concentrated sulphuric acid with a yellowish- 
brown colour, and is decomposed on boiling the solution with blackening and disen- 
gagement of sulphurous acid. Boiling nitric acid changes it into a yellow substance, 
which no longer softens at the temperature of boiling water, and is very little soluble 
in alcohol. It dissolves in alkaline liquids with a brownish-red colour, and is repre- 
cipitated by acids in brown flocks, which on boiling the liquid cohere into dark- 
brown semifluid masses. When heated in a glass tube, it usually gives a small quan- 
tity of sublimed alizarine mixed with a brown oil. It is not capable of dyeing when 
quite free from alizarine. Its analysis yielded the following results : — 
I. 0'5300 grm. from the decomposition of rubian, dried at 100 ° C. and burnt with 
chromate of lead, gave T3190 carbonic acid and 0*2405 water, 
II. 0*3785 grm. of the same preparation as the last, heated to the melting-point, 
gave 0*9465 carbonic acid and 0*1730 water. 
III. 0*4815 grm. obtained directly from madder, dried at 100° C., gave 1*2130 car- 
bonic acid and 0*2335 water. 
IV. 0*4290 grm. of the same preparation as the last, heated to the melting-point, 
gave 1*0735 carbonic acid and 0*2050 water. 
V. 0*3120 grm. of another preparation obtained directly from madder, gave 0*7855 
carbonic acid and 0* 1 460 water. 
VI. 0*2350 grm. of the same preparation as the last, gave 0*5865 carbonic acid and 
0*1065 water. 
3 N 
MDCCCLI. 
