OP ARTS AND SCIENCES. 41 



HI. 



CONTRIBUTIONS FROM THE CHEMICAL LABORATORY OF HAR- 

 VARD COLLEGE* 



1. ON CERTAIN SUBSTITUTED ACRYLIC AND 

 PROPIONIC ACIDS. 



By C. F. Mabery and F. C. Robinson. 



Presented January 10th, 1883. 



/S-DiBROMACRTLic acid, unlike the isomeric a-acid, will not unite 

 with bromine at ordinary temperatures. After standing twelve days, 

 a solution of the acid with bromine in chloroform was not bleached, 

 and by slow evaporation of the solution crystals were deposited which 

 melted at SG'^, the melting-point of dibromacrylic acid. At 100*^ the 

 addition of bromine was easily accomplished. When pure dibrom- 

 acrylic acid was heated in a closed tube with undiluted bromine in slight 

 excess over the calculated amount for one or two hours, tetrabrom- 

 propiouic acid was formed in nearly the theoretical quantity. The 

 excess of bromine was removed by evaporation from the crude product, 

 which was purified by pressure in filter-paper and crystallization from 

 carbonic disuljihide and chloroform. From a concentrated solution in 

 carbonic disulphide it crystallizes by slow evaporation in oblique prisms. 

 It is somewhat soluble in hot water, from which it separates at first as 

 an oil ; but on further cooling it crystallizes in thick prisms. On boil- 

 ing an aqueous solution of the acid, it is rapidly decomposed, imparting 

 a milky appearance to the solution, probably from the formation of tri- 

 bromethylen. Melting point 118°-120°. Its composition was deter- 

 mined by the following analyses. 



I. 0.2149 grm. of the substance gave by Carius's method 0.4169 grm. 



AgBr. 

 II. 0.1639 grm. of the substance gave 0.3145 grm. AgBr. 

 III. 0.8899 grm. of the substance gave 0.2857 grm. CO2 and 0.0478 

 grm. H.^0. 



* This work was done in connection with the summer course of instruction 

 in chemistry for 1882. — C. F. M. 



