OF ARTS AND SCIENCES. 213 



Fittig and Petri fouud in two determinations of water, in the bariuna 

 salt of their acid, a somewhat higher percentage' (6.73 and 7.27), and 

 therefore assign it the formula Ba(C3HBr202)2-25H2^ — (calculated 

 7.03 per cent). 



The solubility of the salt we determined by V. Meyer's method. 

 I. 3.9749 grm. of a solution, satui-ated at 23°, gave, on evaporation 

 with H^SO^ and ignition, 0.1748 grm. BaSO^. 

 n. 3.9148 grm. of a solution, saturated, at 20°, gave 0.1719 grm. 

 BaSO,. 



According to these determinations, the aqueous solution saturated at 

 20° contained the following percentages of the anhydrous salt : — 



I. II. 



11.23 11.21 



Calcic Dihromacrylate, Ca(C3HBr202)2.3|^H20. The calcium salt 

 we prepared by neutralizing a solution of the acid with calcic carbo- 

 nate. On cooling the concentrated solution, the salt separated in long 

 radiating needles. 



I. 0.5625 grm. of the air-dried salt lost, when heated to 100°, 

 0.0668 grm. H2O, and gave, when ignited with H2S0^, 0.1356 

 grm. CaSO^. 

 11. 0.3460 grm. of the salt lost at 100° 0.0394 grm. B.f> and 

 gave 0.0850 grm. CaSO^. 



Calculated for Oa(C3HBr202)2.3iHjO. 



Ca 7.13 



HgO 11.23 



Fittig and Petri found in two determinations of water, in the cal- 

 cium salt of their acid, the percentages 11.56 and 11.47, from which 

 they calculate the formula with ^\ molecules of water given above. 



The physical properties of the acid, and the analyses of the barium 

 and calcium salts, leave no doubt of the identity of this dibromacrylic 

 acid with that described by Fittig and Petri, although our results 

 differ slightly in some respects from theirs. The acid from tribromsuc- 

 cinic acid we have made only in sufficient quantity to assure ourselves 

 that no qualitative differences are to be detected in the properties of 

 the two acids, or in the habit of several of their salts. 



