OF ARTS AND SCIENCES. 127 



carbonate, and adding to the hot solution an equal amount of the acid 

 dissolved in a little hot water. As the solution cools the salt separ- 

 ates in long silky needles, which after a few recrystallizations from hot 

 water yield an acid whose melting-point is constant. The loss in 

 recrystallization is comparatively small, since the salt is but sparingly 

 soluble in cold water and dissolves very freely in hot. The analyses 

 which I have made of the acid prepared in this way show its perfect 

 purity. 



I. 0.2183 grm. substance gave by the method of Carius 0.3573 

 grm. AgBr. 

 II. 0.2127 grm. substance gave 0.3476 grm. AgBr. 

 III. 0.2530 grm. substance gave 0.4137 grm. AgBr. 



Calculated for CsHoBrp.^. 

 Br. 69.56 



The pure acid melts at 85.5-86°, but in other respects does not differ 

 essentially in its physical properties from the product which I have 

 already described. The solubility of the acid was determined by 

 neutralizing with baric carbonate an aqueous solution of the acid 

 prepared according to the method of V. Meyer, and precipitating 

 with sulphuric acid the barium dissolved. 



I. 12.7854 grms. of a solution saturated at 17°. 5 gave 0.3107 grm. 

 BaSO, . 

 II. 13.5723 grms. of a solution saturated at 17°.5 gave 0.3303 grm. 

 BaSO, . 



III. 10.8488 grms. of a solution saturated at 18° gave 0.2695 grm. 



BaSO, . 



IV. 9.7341 grms. of a solution saturated at 18° gave 0.2484 grm. 



BaSO^ . 



According to these determinations the aqueous solution saturated 

 at 17°. 5 and 18° contains the following percentages : — 



17°.5. 18°. 



I. n. III. IV. 



4.80 4.81 4.90 4.94 



Baric Dibromacrylate, Ba(C3HBr202)2 • H.,0. The barium salt 

 prepared by neutralizing a solution of the pure acid with baric car- 



