86 MR. SCHUNCK ON RUBIAN AND ITS PRODUCTS OF DECOMPOSlilON. 
mined. That the acid of the analysis No. I. contained both substances in atomic 
proportions may be accidental ; and the ease with which rubiacate of potash made 
from the impure acid yields, by mere recrystaUization, a salt containing an almost 
pure acid, tends to prove that the two substances are merely mechanically mingled. 
Nevertheless it is difficult to detect the presence of rubiacine in the impure acid, 
which behaves towards almost all reagents in the same manner as the pure acid. 
The acid of the analysis No. IV., for instance, could not be distinguished from pure 
acid by its appearance. When treated with boiling alcohol the latter acquired a yellow 
colour, but on being filtered boiling hot, no rubiacine crystallized out, as would pro- 
bably have been the case had the latter only been mixed with the acid. Nevertheless, 
on heating it cautiously between two watch-glasses, a considerable quantity of yellow 
shining crystals, doubtless of rubiacine, were formed on the upper glass, while the 
rubiacic acid of analysis No. V. gave, on being heated in the same manner, only a 
trace of yellow sublimate and an abundant carbonaceous residue. The potash salt 
of the impure acid has a more granular and less silky appearance than the salt 
made from pure acid, and is also of a darker red. When heated it does not detonate 
so strongly as the pure salt. Its solutions give the same reactions as the pure salt 
with all reagents except nitrate of silver, which, as I mentioned above, gives with the 
pure salt an orange-coloured, with the impure salt a bright cinnabar-red precipitate. 
In order to ascertain whether rubiacic acid is leconvertible not only into rubiacine 
but also into rubiafine, I took some rubiacate of potash of the same preparation as that 
employed for the rubiacic acid No. I., dissolved it in boiling water, added caustic 
soda, and passed sulphuretted hydrogen through the solution for several hours ; I then 
precipitated with chloride of barium, filtered, washed the precipitate, decomposed it 
with muriatic acid, and crystallized the residue twice from alcohol. The crystals 
had the appearance of rubiacine or rubiafine, and possessed considerable lustre. On 
analysis I obtained the following numbers : — 
0-1685 grm. gave 0-4340 carbonic acid and 0-0705 water. 
In 100 parts it contained therefore — 
Carbon 70-24 
Hydrogen 4-64 
Oxygen 25-12 
Though this is not exactly the composition of rubiafine as given above, still it 
proves that the hydrogen and oxygen are contained in it in the same proportion as in 
that substance ; for if the formula CsaHij^Og^, which differs from that of rubiafine by 
containing ^HO less, be calculated for 100 parts, it givms 
Carbon 70-45 
Hyd rogen 4-58 
Oxygen 24-97 
Though I have not, from want of material, been able to trace the steps of the pro- 
