138 PROCEEDINGS OF THE AMERICAN ACADEMY 



found it necessary to add the bromine slowly, and to take care that no 

 liquid bromine comes in contact with the pyromucic acid. We have 

 accomplished this very conveniently by hanging inside the flask con- 

 taining the pyromucic acid a small glass cup, so arranged as to catch 

 the liquid dropping from the reverse cooler and drop-funnel with 

 which the flask is fitted. If the flow of the bromine be carefully 

 regulated and the flask heated in a water bath, the process requires 

 little attention. The reaction, however, is not perfectly smooth. Car- 

 bonic dioxide is evolved, and, as more or less bromine is unavoidably 

 lost with the escaping hydrobromic acid, considerably more than one 

 molecule of bromine must be added to insure the best result. For 20 

 grammes of pyromucic acid we have found it best to use 36 grammes 

 of bromine instead of the 28.57 grammes required by theory. When 

 the reaction is over, the product is dissolved in hot water, filtered, and 

 the voluminous leafy crystals which separate on cooling are purified 

 by recrystallization from hot water. If the bromine has not been 

 added with due care the product may contain more or less dibrom- 

 pyromucic acid, and is deposited then on cooling the hot aqueous 

 solution in fine granular crystals. The dibrompyromucic acid may, 

 however, readily be removed by precipitating an ammouiacal solution 

 with baric chloride and acidifying the filtered solution with hydro- 

 chloric acid. We have not succeeded in obtaining perfectly uniform 

 results in the preparation of the acid, and the yield of pure product has 

 varied between 40 and 60 per cent of the theoretical amount. While 

 we have been unable to prove that isomeric monobrompyromucic acids 

 are formed in the reaction, the properties of the y8-monobrompyromucic 

 acid subsequently described are such that a small quantity of it, if 

 formed, might easily escape detection. 



The acid crystallized from hot water and dried over sulphuric acid 

 gave on analysis the following results : — 



I. 0.2291 grm. substance gave 0.2629 grm. CO., and 0.0322 grm. Bfi. 



II. 0.2571 grm. substance gave 0.2959 grm. CO.^and 0.0400 grm. HJJ. 



III. 0.1944 grm. substance gave 0.1912 grm. AgBi\ 



IV. 0.1993 grm. substance gave 0.1957 grm. AgBr. 

 V. 0.2085 grm. substance gave 0.2051 grm. AgBr. 



IV. 



41.78 41.86 



