12 



" On Aiirine/' by R. S. Dale, B. A., and C. Schoelemmer, 

 F.RS. 



In the July number of the Journal of the Chemical 

 Society, we have published a short note on Aiirine, a 

 colouring matter discovered by Kolbe and Schmitt, in 1861, 

 and which is now found in commerce under the name of 

 aurine, yellow coralline, or rosolic acid. The commercial 

 product which is obtained by heating phenol with oxalic 

 and sulphuric acids, is a mixture of different bodies, from 

 which we have isolated the pure colouring matter by 

 dissolving the crude aurine in alcohol, and treating this 

 solution with ammonia. A crystalline precipitate, a com- 

 pound of aurine with ammonia separated out, whilst the 

 other bodies present remained in solution. The ammonia 

 compound was washed with alcohol by means of Bunsen's 

 filter pump, and decomposed by dilute acetic acid. The 

 aurine thus obtained was further purified by repeated 

 crystallisation from strong acetic acid. It crystallised in 

 rhombic needles or prisms, the colour of which varies 

 according to the concentration of the acid, and as it appears 

 also, according to the purity of the substance. We have 

 obtained it in needles having the colour of chromic acid, 

 and a brilliant diamond lustre, or in darker red crystals of 

 varying shades, with a steelblue, greenish blue, or splendid 

 beetle-green reflection. We have analyzed these difi'erent 

 specimens, partly dried at 100° and partly at higher tem- 

 peratures, and although samples of the same preparation 

 gave very a.greeing results, those of difierent preparations 

 varied very much in their composition. The reason of this 

 is, that aurine retains most obstinately water a.nd acetic 

 acid, a fact which has also been observed by Fresenius,* 

 who has lately published a note on the same subject. 



From concentrated hydrochloric acid aurine crystallises 



in fine, hair like red needles, which, dried at 110°, contain a 



large quantity of hydrochloric acid. We tried to obtain the 



pure compound by precipitating a dilute alkaline with 



* Journ. f. Pract. Chem., No. 10, 1871. 



