OF ARTS AND SCIENCES. 281 



No. II. — ON a- AND /3-CHLORDIBROMACRYLIC ACIDS.* 

 By Charles F. Mabery and Rachel Lloyd. 



a-CHLORDIBROMACRYLIC AciD. 



In a former paper by F. C. Robinsou and one of us,t a brief account 

 was given of certain experiments in which we had tried to obtain gdi 

 addition product of brompropiolic acid with chlorine monobromide. 

 Altliough the results then obtained were rather unsatisfactory, it 

 seemed possible nevertheless to prepare the addition product in a 

 state of purity, and this became especially desirable when it was 

 found that an acid of the same empirical composition could be formed 

 from chlortribrompropionic acid. 



In resuming the study of this reaction, it was evidently necessary to 

 'secure at the outset a combination of the halogens containing no free 

 bromine, inasmuch as previous results had shown that a small percent- 

 age even of tribromacrylic acid could not be removed from the product 

 by crystallization. On the other hand, an excess of chlorine was xaot 

 objectionable since it had been found that this substance in the free 

 state united much less readily with brompropiolic acid than when com- 

 bined with bromine. The chlorine monobromide used to form this 

 addition product was therefore made by saturating bromine at 0° with 

 chlorine; and to insure complete saturation the resulting product was 

 dissolved in chloroform and this solution saturated at 0°. Brompro- 

 piolic acid was then added gradually, taking care to keep the solution 

 cold and the chlorine monobromide in excess. Chemical action imme- 

 diately ensued, and the formation of the addition product was complete 

 after standinsr half an hour. Evaooration of the chloroform left a 

 solid residue, which was easily purified by crystallization from hot 

 water. 



This acid is sparingly soluble in cold, very soluble in hot water, 

 more soluble in hot than in cold carbonic disulphide, and very sol- 

 uble in chloroform. Its melting point is 104°. By slow evapora- 

 tion it separates from a solution in carbonic disulphide in triclinic 

 prisms. These crystals have been submitted to careful study by 



* The results described in papers II., III., and IV. were obtained under my 

 direction in the summer course of instruction in chemistry for 1883. — C. F. M. 

 t These Proceedings, Vol. XVIII. p. 41. 



