250 MESSRS. DALE AND SCHORLEMMER ON AURIN. 



heating pure phenol with oxalic and sulphuric acids for a 

 few days to about 105° C. Although a good product is 

 thus obtained^ the yield is but small^ while on heating the 

 mixture longer^ or to a higher temperature, by-products 

 are formed. Some chemists have stated that the formation 

 of the latter cannot be avoided, and that it is very difficult 

 to obtain thus a pure aurin. We believe that we are able 

 to explain these different results. The formation of a pure 

 compound depends much on the proportions and the 

 manner in which phenol and the acids are mixed. As, 

 however, the preparation of pure aurin by this method is 

 a very tedious j)rocess, we endeavoured to obtain it from 

 the commercial product by the method which we have de- 

 scribed in our first paper, and purifying it by repeated 

 recrystallization from alcohol, the crystals separating out 

 first being used for further purification, because we found 

 that the purer aurin is, the less soluble it becomes, its so- 

 lubility being increased by the admixtures which are 

 present in the crude product. 



Another method for purification which we employed 

 consisted in washing good commercial aurin with cold 

 alcohol until only a comparatively small residue was left, 

 which was then treated as above stated. 



The different crops of crystals were analyzed, and the 

 purification continued until the product did not change its 

 composition any more. A great number of analyses were 

 thus required ; and we have great pleasure in expressing 

 our best thanks to Mr. L. T. O^Shea, who performed them 

 with great care. 



The results did not, however, agree with our former ; 

 the product, having a constant composition, and crystal- 

 lizing exceedingly well, gave numbers agreeing with the 

 formula C,gH,4,0j. We therefore again prepared aurin 

 from pure phenol, and crystallized it repeatedly from al- 



