178 PROCEEDINGS OF THE AMERICAN ACADEMY 



mass of indistinct, aggregated needles, extremely soluble in water, 

 ether, or alcohol ; and almost insoluble in boiling chloroform, benzol, 

 ligroin, or carbonic disulphide. From a mixture of ether and chloro- 

 form, it could be crystallized in the form of fine, felted needles. 



After standing in desiccator, the acid gave on analysis too high a 

 percentage of bromine (I.). It was therefore washed with chloro- 

 form, the excess of chloroform evaporated in a paraffine desiccator 

 according to Liebermann's suggestion ; but the percentage of bromine 

 remained essentially unaltered (II.). I therefore dissolved the acid 

 in hot water, allowed the solution to evaporate spontaneously, and 

 dried by exposure to the air alone, but failed to alter its composition 

 (III.). Subsequently I dissolved the pure anhydride described below 

 in hot water, and found that the acid obtained by spontaneous evapo- 

 ration of this solution when air-dried also contained more bromine than 

 the formula of the acid required (IV.). 



I. 0.2050 grm. substance gave 0.2860 grm. AgBr. 



II. 0.2305 grm. substance gave 0.3200 grm. AgBr. 



III. 0.2150 grm. substance gave 0.3000 grm. AgBr. 



IV. 0.2500 grm. substance gave 0.3475 grm. AgBr. 



From these experiments it would appear that the acid, even at 

 ordinary temperatures, is partially converted into its anhydride. This 

 change goes on rapidly at temperatures near 100°, so that it is impos- 

 sible to obtain constant melting points. The preparations analyzed 

 melted at 120-125° when warmed with ordinary rapidity. The acid 

 was but slightly volatile with steam, but could be distilled with 

 greatest readiness with the vapor of concentrated hydrobromic acid. 



From this acid the anhydride could be obtained without difficulty 

 in a pure state, by heating to 120° in a current of dry carbonic 

 dioxide. The sublimation began at 100°, or possibly lower, but 

 became rapid at 115-120°. The anhydride condensed in lustrous, 

 flattened needles, which melted at 114-115°. In cold water it dis- 

 solved but slowly ; in alcohol, ether, benzol, ligroin, chloroform, or 

 carbonic disulphide, it was readily soluble. 



I. 0.3672 grm. gave 0.2510 grm. CO, and 0.0010 grm. H^O. 

 II. 0.2630 grm. gave 0.3870 grra. Agiir. 



