Dr. Schunck on Rubian and its Products of Decomposition. 417 



witli boiling nitric acid, it dissolves, nitrous acid is disengaged, 

 and the liquid on cooling deposits nothing, so that the substance 

 seems to be decomposed by the acid. Towards alkalies rubia- 

 dine behaves in a similar manner to rubianine. Ammonia and 

 carbonate of soda change its colour very little in the cold. It is 

 only on boiling the alkaline liquids that it dissolves with a blood- 

 red colour. It is precipitated from its alkaline solutions by 

 acids in thick yellow flocks. The ammoniacal solution on expo- 

 sure 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, pro- 

 duces 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 mo- 

 ments a dark brownish-red precipitate falls; the supernatant 

 liquid remains yellow, but contains very little rubiadine in solu- 

 tion. 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 decomposi- 

 tion, and is soluble in boiling water. 



I only obtained sufiicient rubiadine in a state of purity for one 

 analysis, which gave the following results : — 



0*2575 grm. 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 formulae with which this composition agrees, 

 but only two which at the same time satisfactorily explain the 

 formation of this substance, viz. C^^jjiaQS and C^H'^O'i. 

 The great similarity in properties between rubiadine and rubia- 

 nine 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^^ H^^ O^^, it follows that the true formula of rubiadine 

 must be one of the two just given. 



