OP ARTS AND SCIENCES. 219 



about half that of the /35-dibrompyromucic acid taken. The acid dis- 

 solved readily in less than its own weight of water, leaving but the 

 slightest turbidity, and on evaporation it crystallized in colorless 

 prisms, which melted at 129-130°.* An analysis showed this sub- 

 stance to be monobrommaleic acid. 



0.2235 grm. of the acid dried over sulphuric acid gave 0.2161 grm. 

 AgBr. 



Calculated for 

 C 4 U 3 Br0 4 . Found. 



41.03 41.15 



The melting point and the complete and ready solubility of the crude 

 product showed that monobrommaleic was the only essential constitu- 

 ent. The aqueous solution from which the monobrommaleic acid had 

 been extracted with ether was warmed to expel the ether dissolved, 

 neutralized with baric carbonate, and the filtered solution evaporated. 

 A careful examination of the small amount of barium salt thus obtained 

 failed to show that even a trace of a sulphonic acid had been formed.f 

 This result is in accordance with the results of Hill and Sanger,^ who 

 found that the y-hydrogen of the /38-dibrompyromucic acid could not 

 be replaced by bromine. 



* The melting point of monobrommaleic acid is usually given as 128°, and I 

 hare frequent^ determined it myself without noticing that it varies greatly with 

 the time of heating, as is the case with dibrommaleic acid. How great this va- 

 riation may be can be seen from the following observations, which I made with 

 this one analyzed sample. The acid in thin-walled capillary tubes was dipped 

 into the bath heated to constant temperature, and the time of melting noted. 



Temperature of bath. Minutes before melting. 



143 0.17 



140 0.5 



135 0.83 



133 1.3 



131 1.5 



125 4.5 



121 8.0 



The melting point, 129-130°, given above was the result of two successive at- 

 tempts to determine it at the ordinary speed. — H. B. H. 



t The statement made in a preliminary paper (Berichte d. deutsch. chem. 

 Gesellsch., xviii. 2095), that a sulphonic acid was formed in this reaction, was 

 subsequently proved to be incorrect. 



t These Proceedings, xxi. 175. 



