138 PROCEEDINGS OF THE AMERICAN ACADEMY 



tion of bromide. Even on evaporating their solutions at ordinary 

 temperatures over sulphuric acid in vacuo the barium salt was almost 

 wholly decomposed ; the calcium salt was apparently somewhat more 

 stable, for it was thus obtained in dendritic needles, although the mother- 

 liquor contained calcic bromide. Since the air-dried salt lost nothing 

 over sulphuric acid and was decomposed by heat, the water of crys- 

 tallization could not be directly determined. It gave, however, a per- 

 centage of calcium agreeing closely with that required by two 

 molecules of water. 



I. 1.1087 grm. of the air-dried salt gave on ignition with HgSO^ 

 0.2179 grm. CaSO,. 

 II. 0.7279 grm. of the air-dried salt gave on ignition with HgSO^ 

 0.1425 grm. CaSO, . 



Calculated for Ca(C3H^Br302)2- 2Hp. Found. 



Ca 5.75 5.78 5.76 



We were unable to prepare other salts. 



Dihromacrylic Acid. The ready decomposition of the tribrompro- 

 pionic acid made it seem desirable to isolate and identify the dihrom- 

 acrylic acid which was thus formed. For this purpose we dissolved 

 pure tribrompropionic acid, melting at 118°, in water and added from 

 a burette a titrated solution of baric hydrate. So ra|)id was the 

 action that an alkaline reaction could not be maintained until nearly 

 one molecule of baric hydrate had been added for each molecule of 

 the acid. When the calculated amount of baric hydrate had been 

 added the solution was allowed to stand for half an hour, and then 

 but a trace of baric carbonate could be precipitated with carbonic 

 dioxide. Ether extracted from the acidified solution a crystalline 

 acid melting at 85-86°, which gave on analysis the percentage of 

 bromine required by the formula C3H2Br20.2 . 



0.1979 grm. substance gave 0.3240 grm. AgBr. 



Calculated for CsHoBroO.^ . Found. 



Br. 69.57 " 69.66. 



The solubility of the acid in cold water was determined by the 

 method of V. Meyer. 



I. 10.7793 grms. of a solution saturated at 18° gave on neutralization 

 with baric carbonate and precipitation 0.2908 grm. BaSO^ . 

 II. 7.7354 grms. of a solution saturated at 18° gave 0.1940 grm. 

 BaSO, . 



