Dr. Schunck on Rubian and its Products of Decomposition. 219 



to that of the other constituents. If the oxide of lead be de- 

 ducted, then the rubihydran combined with it will have the 

 following composition in 100 parts : — 



I. II. 



Carbon 51-37 51-38 



Hydrogen .... 6-12 5-92 



Oxygen 4251 4270 



100-00 100-00 



It will be seen that this is exactly the composition of the 

 substance itself according to the analysis given above, and it 

 follows that the composition of rubihydran, both in a perfectly 

 dry state and when in combination with oxide of lead, is ex- 

 pressed by the formula C^ H^^ 0^^. It differs therefore from 

 rubian by containing the elements of 5 equivalents more of 

 water. That it should yield the same products of decomposition 

 as rubian and rubidehydran is therefore not at all extraordinary. 



The rubiadine which is formed by the decomposition of rubi- 

 hydran with acids may be obtained in a state of greater purity 

 and with much greater facility from this, than from any other 

 source. It is separated from the other products of decomposi- 

 tion in the manner I have described when treating of the action 

 of alkalies on rubian. It is purified by dissolving it in boiling 

 alcohol and adding to the boiling solution hydr^ted oxide of 

 lead, when it crystallizes from the filtered solution in beautiful 

 golden-yellow, glittering scales, some of which assume the form 

 of regular four-sided tables, possessing all the properties of ru- 

 biadine*, but evidently freer from impurities than when obtained 

 by the action of alkalies on rubian. 



I. 0'3060 grm. of this substance, dried at 100° C, gave 

 07795 carbonic acid and 0-1380 water. 



II. 0*2580 grm. of the same, recrystallized from boiling alco- 

 hol, gave 0-6600 carbonic acid and 0*1190 water. 



From these numbers it may be inferred that its composition 

 is as follows : — 



* In examining these crystals I discovered a property of rubiadine which 

 I had not previously observed. If the ammoniacal solution, which is red, 

 be mixed with chloride of barium, it deposits a quantity of dark brownish- 

 red needle-shaped crystals, which are evidently the baryta compound of 

 rubiadine, while the liquid loses almost all its colour. The rubiadine de- 

 rived directly from rubian also yields these crystals. 



