MESSRS. DALE AND SCHORLEMMER ON AURIN. 251 



cohol^ until its composition became constant, and found it 

 to have the same formula. 



Aurin therefore appears to be the lower homologue of 

 rosolic acid ; like the latter, it readily forms a tetrabromo 

 compound, which we obtained pure by the following pro- 

 cess : — Pure aurin was dissolved in hot glacial acetic acid, 

 and this solution poured into a mixture of an excess of 

 bromine and acetic acid. The liquid remained perfectly 

 clear ; but on standing for a few days, the tetrabromaurin 

 crystallized out almost completely. It forms small 

 brownish-green crystals with a metallic lustre, which 

 dissolve in alkalies with a purple colour. The determi- 

 nation of the bromine gave numbers agreeing closely with 

 those required for the formula Cj^H^JirJDy 



Whilst this investigation was going on, a new light was 

 thrown on the subject by the researches of E. and O. 

 Fischer. In order to elucidate the constitution of rosani- 

 line, these chemists endeavoured to convert rosaniline into 

 the hydrocarbon from which it is derived. In this they 

 did not succeed ; but they were able to transform leuca- 

 niline (CjoH^iNJ, which stands to rosaniline in the same 

 relation as leucaurin to aurin, into a hydrocarbon CjoH,8, 

 which is the mother substance of this base, and from which 

 it follows that the hydrocarbon corresponding to rosaniline 

 has the composition CioHjg, which also confirms the cor- 

 rectness of Hofmann^s formula for rosaniline. The leu- 

 caniline which they employed was obtained from com- 

 mercial rosaniline ; but Rosenstiehl has shown that this 

 body, which is prepared by oxidizing a mixture of aniline, 

 solid paratoluidine, and liquid pseudotoluidine, contains 

 several, probably isomeric, bases. E. and O. Fischer 

 therefore, in continuing their research*, prepared one of 

 them in the pure state by using a mixture of pure aniline 

 * Ber. deutsch. chem. Ges. xi. 195. 



