12 
“ On Aurine,” by It. S. Dale, B. A., and C. Schorlemmer, 
F.R.S. 
In the July number of the Journal of the Chemical 
Society, we have published a short note on Aurine, 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 different 
specimens, partly dried at 1 00° and partly at higher tem- 
peratures, and although samples of the same preparation 
gave very agreeing results, those of different preparations 
varied very much in their composition. The reason of this 
is, that aurine retains most obstinately water and 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, hairlike 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. Clicm., No. 10, 1871. 
