Dr. Schunck on Ruhian and its Products of Decomposition. 431 



If the formula of the potash salt be similar to that of the silver 

 salt, viz. C^^H^Qi^ + KO, it must contain in 100 parts- 

 Carbon 51-17 



Hydrogen . . . . . 2*13 



Oxygen 34-12 



Potash 12-58 



In my former experiments I obtained as an average of three 

 determinations — 



Carbon 51-37 



Hydrogen 2*41 



Oxygen 33-18 



Potash 13-04 



It appears therefore that the four first analyses given above 

 were made with impure acid. The analysis No. I. corresponded, 

 as I have shown, with the formula C^ H^^ 0^. Now if from this 

 formula be deducted that of the pure acid C^^ H^ 0^^^ the dif- 

 ference will be C^^H^^O^^, which is the formula given above 

 for rubiacine. It is therefore almost certain that it was an ad- 

 mixture of the latter substance with the acid which raised the 

 amount of carbon and hydrogen in the four first analyses. 

 Whether this impure acid is to be considered as a chemical 

 compound of acid and rubiacine, or whether it contains them 

 in a state of mechanical mixture, is a point not easily determined. 

 That the acid of the analysis No. I. contained both substances 

 in atomic proportions may be accidental ; and the ease with 

 which rubiacate of potash made from the impure acid yields, by 

 mere recrystallization, a salt containing an almost pure acid, 

 tends to prove that the two substances are merely mechanically 

 mingled. Nevertheless it is difiicult to detect the presence of 

 rubiacine in the impure acid, which behaves towards almost aU 

 reagents in the same manner as the pure acid. The acid of the 

 analysis No. IV., for instance, could not be distinguished from 

 pure acid by its appearance. When treated with boiling alcohol 

 the latter acquired a yellow colour, but on being filtered boiling 

 hot, no rubiacine crystallized out, as would probably have been 

 the case had the latter only been mixed with the acid. Never- 

 theless, on heating it cautiously between two watch-glasses, a 

 considerable quantity of yellow shining crystals, doubtless of 

 rubiacine, were formed on the upper glass, while the rubiacic 

 acid of analysis No. V. gave, on being heated in the same man- 

 ner, only a trace of yellow sublimate and an abundant carbona- 

 ceous residue. The potash salt of the impure acid has a more 

 granular and less silky appearance than the salt made from pure 

 acid, and is also of a darker red. When heated it does not de- 

 tonate so strongly as the pure salt. Its solutions give the same 



