216 Dr. Schunck on Colouring Matters. 



I. 0*4490 grin, rubiacate of potash gave 0*1090 sulphate of pot- 

 ash, equivalent to 0*0589 potash. 



0*4350 grm. gave 0*7950 carbonic acid and 0*0900 water. 



II. 0*3245 grm. gave 0*0790 sulphate of potash, equivalent to 

 0*0427 potash. 



0*2890 grm. gave 0*5315 carbonic acid and 0*0665 water. 

 From these numbers it may be inferred that the salt is com- 

 posed as follows : — 



Calculated ^«y"'i- 



360*27 100*00 100*00 100*00 



I. 0*3785 grm. rubiacic acid, dried at 212° and burnt with oxide 

 of copper, gave 0*7940 carbonic acid and 00845 water. 



II. 0*3605 grm. of another preparation gave 0*7610 carbonic 

 acid and 0*0795 water. 



III. 0*4670 grm. of the same preparation as the preceding gave 

 0*9775 carbonic acid and 0*1050 water. 



Hence was deduced the following composition : — 



Found. 



Calculated 



31 eqs. Carbon .. 186 



8 ,, Hydrogen 8 



16 „ Oxygen . . 128 



322 100*00 100*00 100*00 100*00 

 0*3150 grm. rubiacine, dried at 212° and burnt with oxide of cop- 

 per, gave 0'7740 carbonic acid and 0*0935 water. 

 This gives the following composition : — 



Calculated. Found. 



31 eqs. Carbon 186 67*63 67*01 



9 „ Hydrogen 9 3*27 3*28 



1 „ Oxygen , _80 29*10 29*71 



275 100*00 100*00 



The formula of rubiacine being C31 HgOjo, and that of rubiacic acid 

 CgiHgOis, it follows that when rubiacine is converted into rubiacic 

 acid, it loses one equivalent of hydrogen and takes up six equi- 

 valents of oxygen, and that when rubiacic acid is reconverted into 

 rubiacine, it loses six equivalents of oxygen and takes up again one 

 of hydrogen. This oxidation and reduction is accomplished with 

 the same certainty and precision as any similar process with inorganic 

 bodies. 



Alpha-resin. — This resin is a constituent of the dark brown pre- 

 cipitate produced by acids in a decoction of madder. It dissolves 

 together with rubiacine, when this precipitate is treated with a boil- 



