154 PROCEEDINGS OF THE AMERICAN ACADEMY 



From the more soluble calcium salt we obtained the /3y-dibrompy- 

 romucic acid aielting at 190-192°, which gave on analysis the proper 

 percentage of bromine. 



0.1955 grm. substance gave 0.2723 grm. AgBr. 



Calculated for CjIIjBroOa. Found. 



Br 59. 2G " ' " 59.29 



Furthermore, it was not difficult to isolate in considerable quantity 

 an acid containing but a trace of bromine, which melted at 129-130°, 

 and which possessed in other respects the character of pyromucic acid. 

 Our observations agree closely with those described by Canzoneri and 

 Oliveri in the paper already mentioned,* with the single exception that 

 they appear to liave overlooked entirely the formation of the second 

 dibrompyromucic acid melting at 167-168°. Since the two dibrom- 

 pyromucic acids and unaltered pyromucic acid were formed from a 

 product containing equal molecules of ethyl pyromueate and bromine, 

 we were led to the conciusion tljat no dibromide had been formed 

 under the conditions chosen, and that the supposed dibromide was in 

 fact only a mixture of unaltered pyromucic ether with its tetrabromide. 

 Since at ordinary temperatures quantities of hydrobromic acid were 

 evolved on mixing the pyromucic ether with bromine,t (a fact not 

 mentioned by Sehiff and Tassinari or by Canzoneri and Oliveri,) it was 

 evident that the monobrom pyromucic acid which appeared among the 

 products could readily have been formed by direct substitution. On 

 submitting the mixture of equal molecules of pyromucic ether and 

 bromine to fractional distillation in vacuo, it was easy to isolate 

 among the more volatile products the ethyl ether of g-monobrom- 

 pyromucic acid and ethyl pyromueate, melting at 34-35°. The ethyl 

 monobrompyromucate still contained ethyl pyromueate, since the per- 

 centage of bromine which we found was much too low. 



0.1890 grm. substance gave 0.1487 grm. AgBr. 



Calculated for (CII-.jCiHjBrOs. Found. 



Br 36.54 33.49 



The acid obtained from the ether, when recrystallized from water, 

 melted at 182-183°. 



* Gazzetta Cliimica, xiv. 173. 



t The evolution of hydrobromic acid was invariably observed, altliough we 

 varied in many ways the conditions under wliicli tlie reaction took place. In 

 addition to tlie glacial acetic acid recommended by Scliiff and Tassinari as a 

 solvent, we tried carbonic disulpliide and chloroform with tlie same results. 



