MESSRS. DALE AND SCHORLEMMER ON AUBIN. 249 



other organic colouring-matters, with hydrogen, yielding 

 leucaurin (CioHi^Oj), which readily crystallizes in large 

 colourless prisms, whilst on heating aurin with ammonia 

 under pressure a new red colouring-matter is formed which 

 is called red aurin or peonin. 



The further investigation of this body showed that it 

 contained nitrogen, which, on heating with soda-lime, was 

 evolved in some cases completely as ammonia, while in 

 others, where the action of the ammonia went on longer, 

 it was given off, at least partly, in the form of aniline. 

 We then found that, on continuing the heating, the red 

 colour of the liquid became paler, and at last a yellowish 

 solution was obtained, from which water precipitated a 

 white crystalline body possessiug all the characteristic 

 properties of rosaniline *. The formation of this compound 

 might be explained by the following equation : — 



C.0H.4O3 + 3NH3 = C,oH.,N3 + 3H,0. 



But Hofmann, who has most carefully examined rosa- 

 niline as well as a great number of its derivatives, found 

 that the formula of this base is C^Ji^^O^ ; and this result 

 has been confirmed by Caro and Grabef, who showed that 

 rosolic acid, which is obtained from rosaniline by a reac- 

 tion which may be shortly stated to be the inverse of that 

 above given, has the composition C^oHj^Oj, whilst its 

 properties are in almost all respects so similar to aurin 

 that some chemists, including ourselves, have been inclined 

 to regard them as identical. 



In order to clear up these points, it was necessary to 

 prepare a considerable quantity of pure aurin. We have 

 already shown, in our memoir read before the Chemical 

 Society J, that a pure compound is readily obtained by 



* Journ. Chem. Soc. (2) xi. 434. t Liebig's Ann. clxxix. 148. 



I Journ. Chem. Soo. 1877, ii. 121, 



