134 PROCEEDINGS OF THE AMERICAN ACADEMY 



the same acid has shown us that their assertion, though unsujiporteci 

 by eviilence, was accidentally correct. 



Dihromacrylic Acid, CgHgBr^Og . In the preparation of the tri- 

 brompropionic acid neces.^ary for this research we followed quite 

 closely the method of Michael and Norton, although we did not con- 

 sider it necessary to purify the dibrompropyl alcohol by distillation 

 under diminished pressure before oxidation. For the conversion of 

 the tribrompropionic acid into the corresponding dihromacrylic acid 

 we have found it most advantageous to dissolve it in the calculated 

 amount of a titrated solution of baric hydrate, and to allow the 

 reaction to proceed at ordinary temperatures. After standing for 

 several days the neutral or at most feebly alkaline solution was evap- 

 orated, and the acid extracted from the recrystallized barium salt thus 

 obtained. Since this acid was found by preliminary trial to give a 

 sparingly soluble acid potassium salt which crystallized in long silky 

 needles, for further purification it was converted into this salt. After 

 several recrystallizations from hot water, the acid was set free by the 

 addition of hydrochloric acid and extracted with ether. The acid thus 

 obtained crystallized in small oblique prisms readily soluble in alcohol, 

 ether, and chloroform, more sparingly in benzol or carbonic disuljihide. 

 Under water the crystals melted at about 20° to a colorless oil which 

 dissolved readily on heating. The acid dried over sulphuric acid 

 melted at 85-86°, and gave on analysis percentages corres^jonding to 

 the formula CgHgBrgOg . 



I. 0.7497 grm. substance gave on combustion 0.4341 grm. CO^ and 

 0.0673 grm. Hp . 

 II. 0.2863 grm. substance gave 0.4691 grm. AgBr. 

 III. 0.2093 grm. substance gave 0.3432 grm. AgBr. 



Calculated for C3H.,Br„0., . Found. 



' ' ' I. II. III. 



15.79 

 1.00 



69.72 69.84 



The solubility of the acid we determined by neutralizing with baric 

 carbonate an aqueous solution prepared according to the method of 

 V. Meyer and determining by precipitation the barium dissolved. 



I. 12.4640 grms. of a solution saturated at 18° gave 0.3124 grm. 

 BaSO^ . 

 II. 12.2745 grms. of a solution saturated at 18° gave 0.3091 grm. 

 BaSO,. 



