432 Dr. Schunck on Rubian and its Products of Decomposition, 



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 reconvertible 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 cry- 

 stals had the appearance of rubiacine or rubiafine, and possessed 

 considerable lustre. On analysis I obtained the following num- 

 bers : — 



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 C^"^ H^^ 0^*, which difiers from that of rubiafine 

 by containing JHO less, be calculated for 100 parts, it gives — 



Carbon 70*45 



Hydrogen 4*58 



Oxygen ...... 24*97 



Though I have not, from want of material, been able to trace 

 the steps of the process with the requisite accuracy, I think I am 

 justified in inferring from these experiments, that by the oxidi- 

 zing agency of persalts of iron rubiafine is changed first into 

 rubiacine and then into rubiacic acid, and that the latter is 

 reconverted by the action of reducing agents, such as sulphu- 

 retted hydrogen, first into i-ubiacine and then into rubiafine. 

 The presence of rubiacine, however, in the liquor which has been 

 used for dyeing with madder, seems to prove that its direct for- 

 mation from rubian is possible. 



Rubiagine. — This substance belongs to the same group of 

 bodies which includes i*ubianine, rubiadine and rubiafine, and 

 bears a strong resemblance to these substances in properties and 

 composition. It scarcely ever appears in well-defined crystals. 

 When its alcoholic solution is evaporated spontaneously, it is 

 obtained in the shape of small lemon-yellow spherical grains, 

 which, when crushed and examined under a lens, are found to 



