90 
MR. SCHUNCK ON RUBIAN AND ITS PRODUCTS OF DECOMPOSITION. 
colouring matter. Its colour is yellowish-brown. When heated on platinum foil it 
melts to a brown liquid and then burns with a bright flame, leaving a carbonaceous 
residue. When heated in a tube it evolves acrid fumes, similar to those produced 
by fat when exposed to destructive distillation. It is not much affected by boiling 
nitric acid, but concentrated sulphuric acid chars it when heated. When thrown 
into boiling water rubiadipine melts, forming oily drops, which rise to the surface. It 
is soluble in caustic alkalies with a blood-red colour, but the solutions do not froth 
when boiled like solutions of soap. The arnmoniacal solution gives only a slight 
precipitate with chloride of barium. On adding to the alcoholic solution a small 
quantity of acetate of lead, a pale reddish-brown precipitate is formed, which is the 
lead compound. This precipitate is insoluble in boiling alcohol, but dissolves entirely 
when an excess of acetate of lead is added to the boiling liquid, forming a dark 
brownish-red solution. From this solution it is again precipitated by water, and 
after filtering and washing is found to be again insoluble in boiling alcohol. In its 
behaviour to sugar of lead it therefore resembles rubiagine. The alcoholic solution 
gives no precipitate on the addition of acetate of copper. The substance itself cannot 
be obtained in a state fit for analysis, I therefore confined myself to the examination 
of the lead compound formed in the manner just described. The quantity of the 
substance obtained was, nevertheless, so small that I had only sufiicient for one 
analysis at my disposal. 
0-2020 grm., dried at 100° C., gave 0-3770 carbonic acid and 0-1260 water. 
0-1150grm. gave 0-0490 sulphate of lead, containing 0-03605 oxide of lead. 
These numbers lead to the formula €30 O^+PbO, as the following calculation 
shows ; — 
Carbon .... 
Eqs. 
30 
180 
Calculated. 
50-60 
Found. 
50-89 
Hydrogen . . • 
24 
24 
6-74 
6-93 
Oxygen .... 
5 
40 
11-26 
10-83 
Oxide of lead . . 
1 
111-7 
31-40 
31-35 
If this formula represents 
the 
365-7 
true composition 
10000 
of rubiadipine. 
100-00 
I confess I 
unable to explain its formation from rubian. The great excess of hydrogen contained 
in it, shows that some substance must be formed simultaneously containing a large 
proportion of oxygen, but which has hitherto escaped detection. 
The experiments above detailed prove that the decomposition which rubian under- 
goes by fermentation, does not differ in its general nature from that which results 
from the action of acids or alkalies. The decotnposing effect of the ferment extends 
like that of these agents to three portions of rubian. The first portion of rubian loses 
water and gives rise to the formation of alizarine. The second loses water and pro- 
duces rubiretine and verantine in equivalent proportions. The third takes up water 
and gives sugar and rubiafine, or it takes up 1 equiv. more of water, and yields sugar 
