MR. SCHUNCK ON RUBIAN AND ITS PRODUCTS OF DECOMPOSITION. 399 
on a filter and slightly washed with water. As it was found to dissolve in water with 
a reddish-brown colour, as soon as the excess of nitrate of silver was removed, the 
edulcoration was completed with alcohol, in which the salt is insoluble. After being- 
dried in vacuo — 
0-6300 grm. gave 0-1370 grm. chloride of silver, equivalent to O'l 1076 or 17-58 per 
cent. of oxide of silver. The formula H 28 Osg-j-AgO requires 17‘47 per cent. 
The alizarine and sugar obtained by the decomposition of rubianic acid with acids 
and alkalies, I found to have the usual composition, as the following analyses will 
show : — 
I, 0-2190 grm. alizarine, obtained by the action of sulphuric acid on rubianic acid, 
dried at 100°C., yielded 0-5550 carbonic acid and 0-0850 water. 
II. 0-3320 grm. alizarine, formed by the decomposition of rubianic acid with 
caustic soda, dried at 100° C.., gave 0-8480 carbonic acid and 0-1195 water. 
These numbers give in 100 parts — 
Carbon . . 
I. 
.... 69-11 
II. 
69-66 
Hydrogen . 
.... 4-31 
4-00 
Oxygen . . 
.... 26-58 
26-34 
The sugar derived from the decomposition of rubianic acid with sulphuric acid 
was prepared for analysis by heating it, after the solution had been evaporated to 
a syrup, for some time at 100° C. until it became sufficiently brittle to be pulverized, 
when 
0-3600 grm. yielded 0-5840 carbonic acid and 0-2060 water, corresponding with 
the following composition : — 
Carbon 
Eqs. 
... 12 
72 
Calculated. 
44-44 
Found. 
44-24 
Hydrogen . 
... 10 
10 
6-17 
6 35 
Oxygen 
... 10 
80 
49-39 
49-41 
162 
100-00 
100-00 
This specimen of sugar had therefore the same composition as that obtained by 
the action of erythrozym on rubian^. 
The analysis of the acid, its compounds and products of decomposition just detailed, 
lead to the conclusion that its composition must be expressed by tlie formula C 52 II,g O^-, 
and that it belongs to the class of the so-called glucosides, the copula contained in it 
being alizarine. Its decomposition, by means of strong acids and alkalies into 
alizarine and sugar, is symbolized by the following equation; — 
C,2 1 - 1,9 0^7+ 5HO=2C,, H, 0,-f 2C.2 
In order to remove all doubt concerning the true formula of this substance, I deter- 
MDCCCLV. 
* Philosophical Transactions for 1853, p. 79. 
3 H 
