436 Dr. Schunck on Ruhian and its Products of Decomposition. 



the latter in always remaining soft and viscid, and never becoming 

 hard and brittle, however long it may be heated. It is similar 

 in appearance to a semifluid fat tinged with colouring matter. 

 Its colour is yellowish-brown. When heated on platinum foil it 

 melts to a brown liquid and then burns with a bright flame, 

 leaving a carbonaceous residue. When heated in a tube it evolves 

 acrid fumes, similar to those produced by fat when exposed to 

 destructive distillation. It is not much afi'ected by boiling nitric 

 acid, but concentrated sulphuric acid chars it when heated. When 

 thrown into boiling water rubiadipine melts, forming oily drops, 

 which rise to the surface. It is soluble in caustic alkalies with 

 a blood-red colour, but the solutions do not froth when boiled 

 like solutions of soap. The ammoniacal solution gives only a 

 slight precipitate with chloride of barium* On adding to the 

 alcoholic solution a small quantity of acetate of lead, a pale red- 

 dish-brown precipitate is formed, which is the lead compound. 

 This precipitate is insoluble in boiling alcohol, but dissolves 

 entirely when an excess of acetate of lead is added to the boiling 

 liquid, forming a dark brownish-red solution. From this solu- 

 tion it is again precipitated by water, and after filtering and 

 washing is found to be again insoluble in boiling alcohol. In 

 its behaviour to sugar of lead it therefore resembles rubiagine. 

 The alcoholic solution gives no precipitate on the addition of 

 acetate of copper. The substance itself cannot be obtained in a 

 state fit for analysis, I therefore confined myself to the examina- 

 tion of the lead compound formed in the manner just described. 

 The quantity of the substance obtained was, nevertheless, so 

 small that I had only sufficient for one analysis at my disposal. 



0-2020 grm., dried at 100° C, gave 0-3770 carbonic acid and 

 01260 water. 



0*1150 grm. gave 0*0490 sulphate of lead, containing 0*03605 

 oxide of lead. 



These numbers lead to the formula C^o 11^4 0^ -|- PbO, as the 

 following calculation shows :■ 



355-7 100*00 10000 

 If this formula represents the true composition of rubiadipine, 

 I confess I am unable to explain its formation from rubian. The 

 great excess of hydrogen contained in it, shows that some sub- 

 stance must be formed simultaneously containing a large pro- 

 portion of oxygen, but which has hitherto escaped detection. 

 [To be continued.] 



