MR. SCHUNCK ON RUBIAN AND ITS PRODUCTS OF DECOMPOSITION. 73 
red colour. It is precipitated from its alkaline solutions by acids in thick yellow 
flocks. The ammoniacal solution on exposure to the air loses its ammonia and 
deposits the substance in the shape of a yellow uncrystalline pellicle. On adding 
chloride of barium to the ammoniacal solution, no effect is produced at first, but after 
some time a slight dark red precipitate falls. Chloride of calcium, added to the 
ammoniacal solution, produces almost immediately a copious light red precipitate. 
Acetate of lead gives no precipitate in an alcoholic solution of rubiadine, and water 
throws down rubiadine in an uncombined state. On adding acetate of copper to 
the alcoholic solution, no effect ensues at first beyond a darkening of the solution, but 
after a few moments a dark brownish-red precipitate falls ; the supernatant liquid 
remains yellow, but contains very little rubiadine in solution. When treated with a 
boiling solution of perchloride of iron, rubiadine does not dissolve. The liquid changes 
very slightly in colour, and gives after filtration only a very slight precipitate on the 
addition of muriatic acid. The residue left undissolved by the perchloride of iron is 
unchanged rubiadine. By its volatility, when exposed to heat, and by its insolubility 
in boiling water, rubiadine may be easily distinguished from rubianine, which cannot 
be strongly heated without decomposition, and is soluble in boiling water. 
I only obtained sufficient rubiadine in a state of purity for one analysis, which gave 
the following results; — 
0'2575 grin, gave 0'6725 carbonic acid and 0'1120 water. 
These numbers correspond in 100 parts to — 
Carbon 71*22 
Hydrogen 4’83 
Oxygen 23*95 
There are several formulee with which this composition agrees, but only two which 
at the same time satisfactorily explain the formation of this substance, viz. CagHjaOg 
and C 44 H ,5 0,i. The great similarity in properties between rubiadine and rubianine 
makes it probable that both have a similar composition, and as it is almost certain 
from the experiments above detailed that the formula of the sugar resulting from the 
decomposition of rubian is C 12 H 12 0 , 2 , it follows that the true formula of rubiadine 
must be one of the two just given. 
These formulae require respectively in 100 parts — 
C32HJ2O8. C 44 H ,5 0ii. 
Carbon . . . 71*64 71*93 
Hydrogen . . 4*47 4*08 
Oxygen . . . 23*89 23*99 
If the first formula be the correct one, then the formation of rubiadine is due to the 
splitting up of 1 equiv. of rubian, after the assimilation of 2 equivs. ofwater, into 1 equiv. 
of rubiadine and 2 equivs. of sugar, as will be seen by the following equation ; — 
2 equivs. of Sugar . . . =C 24 H 24 O 24 I _ fCsg H 34 030 = 1 equiv. of Rubian. 
1 equiv. of Rubiadine . . =C 32 Hi 2 0 8J 1 TC O 2=2 equivs. of Water. 
C56 Hse O32 C56 H 3 g O32 
