144 PROCEEDINGS OF THE AMERICAN ACADEMY 



already described.* Dr. W. II. Melville kiudly made a crystallo- 

 graphic study of the crystals which we obtained, and established their 

 identity with those he had previously examined, which were prepared 

 by the addition of bromine to brompropiolic acid. A description of 

 the crystalline form of tribromacrylic acid Dr. Melville presents in 

 a separate communication. 



a Dichlorhrompropionic Acid. 



In studying the dichloracrylic acid made from raucochloric acid 

 W. Z. Bennett and one of us found that even at 100° it would not 

 take up bromine when dissolved in chloroform.f Subsequently it 

 appeared from the experiments of C. W. Andrews that the substituted 

 propionic acid could readily be made by the action of undiluted bro- 

 mine, although circumstances at the time prevented a detailed study 

 on his part. As a precise characterization of this addition product 

 seemed of interest we undertook its preparation and investigation. 



Pure dichloracrylic acid melting at 85-86° was heated with a mol- 

 ecule of bromine for several hours at 100°. The almost colorless 

 product of the reaction was pressed thoroughly with paper and purified 

 by crystallization, at first from carbonic disulphide, and finally from 

 chloroform. When dried over sulphuric acid this substance gave on 

 analysis percentages agreeing closely with those required by the for- 

 mula CHgCljBr^Oj. In the indirect determination of the halo- 

 gens we used the extremely convenient and accurate method recently 

 described by Mr. L. P. Kinnicutt.J 



I.§ 0.8124 grm. substance gave 0.3550 grm. CO^ and 0.06G5 grm. 

 HoO. 

 11. 0.1715 grm. substance gave 0.3775 grm. AgCl -\- AgBr. 

 III. 0.4790 grm. substance gave 1.0559 grm. AgCl -f- AgBr. From 

 this by reduction was obtained 0.6887 grm. Ag. 



* These Proceedings, Vol. XVI. (n. s. viii.) p. 210. ISIauthner and Suida 

 assign to the barium and calcium salts of this acid, prepared by them from tetra- 

 brompropionic acid, formulae differing greatly from those which we formerly 

 established by our analyses. Since their determinations were made with 

 small quantities of material, we have not thought it necessary to make further 

 analyses in support of our formulae. 



t Tliese Proceedings, Vol. XVI. (n. s. viii.) p. 211. 



X These Proceedings, Vol. XVn.(N. s. xi.) p. 91. 



§ These analyses were made by Mr. Andrews. 



