MR. SCHUNCK ON RUBIAN AND ITS PRODUCTS OF DECOMPOSITION. 
95 
acid, which destroyed the alizarine, leaving the two other substances behind in the 
shape of a yellow powder, which was filtered, washed, dried and weighed. By 
deducting its w^eight from the total weight of the three, the weight of the alizarine 
was ascertained. The liquid filtered from the alumina precipitate deposited on the 
addition of sulphuric acid and water a yellow powder, which was collected on a filter, 
washed, dried and weighed. It was then treated with a little cold alcohol. This 
left undissolved a quantity of rubiagine, which was again collected on a filter, dried 
and weighed. The alcohol left on evaporation a dark brown mass, the fatty nature 
of which showed that it contained rubiadipine in addition to rubiretine. Now I ob- 
tained from that half of the solution to which carbonate of soda had been added, the 
following quantities of these various substances: — 0'323 grm. alizarine, 0‘220 grrn. 
rubiafine, 0T67 grm. of the mixture of rubiafine and verantine, 0‘250 grm. rubiagine, 
and OT/O grm. of the mixture of rubiretine and rubiadipine. From the other half, to 
which sulphuric acid had been added, I obtained the following quantities of the same 
bodies: — 0-2030 grm. alizarine, 0 340 grm. rubiafine, 0-157 grm. of the mixture of 
rubiafine and verantine, 0-310 grm. rubiagine, and 0-230 grm. of the mixture of rubire- 
tine and rubiadipine. In both cases a quantity of rubian remained undecomposed, 
but the quantity actually decomposed was capable of being approximately determined 
from the quantities of products of decomposition formed. Assuming the formula of 
rubiafine to be C32 H13 O9, that of rubiagine C32 H14 Oio, assuming further that the 
mixture of rubiafine and verantine consisted entirely of the latter substance, by 
w'hich no great error is committed (since the quantities of rubiafine and verantine 
which one atom of rubian is capable of yielding are to one another as 277 to 258), 
and leaving out of consideration the trifling quantity of rubiadipine formed (the rubi- 
retine being given by the amount of verantine), then the quantities of the various 
substances obtained correspond respectively to the following quantities of rubian : — 
Rubian. 
Alizarine . 0-323 corresponds to 0-407 
Rubiafine . 0-220 corresponds to 0-484 
Rubiagine . 0-250 corresponds to 0-533 
Verantine . 0- 167 corresponds to 0-394 
Rubian. 
0-203 corresponds to 0-255 
0-340 corresponds to 0-748 
0-310 corresponds to 0-661 
0-157 corresponds to O-371 
1-818 
2-135 
Hence it appears that though the amount of rubian which actually underwent 
decomposition was less when carbonate of soda was added than when sulphuric acid 
was employed in addition to the ferment, still the amount of the alizarine produced 
was greater in the former than the latter case, while the amount of almost all the other 
substances was proportionally less. In using carbonate of soda, the quantity of 
alizarine formed amounted to 17'7 per cent., in using sulphuric acid it amounted to 
9-5 per cent, of the rubian decomposed. The quantity which should be formed, if 
the rubian were entirely converted into alizarine, is 79'3 per cent. 
o 2 
