98 PROCEEDINGS OF THE AMERICAN ACADEMY 



quescent that we were unable to determine the water of crystalliza- 

 tion. 



0.8834 grm. of the salt dried at 80° gave 0.1842 grm. KgSO^. 



Calculated for KCaBr^IO^. Found. 



K 9.92 9.92 



Argentic dihromiodacrylate AgCgBr.^IOj. 



From a hot aqueous solution of the acid the silver salt is precipitated 

 by the addition of argentic nitrate in hexagonal plates. It may be 

 recrystallized from hot water without decomposition, and it is but 

 slightly affected by the action of light. The salt was dried over sul- 

 phuric acid for analysis. 



1.0737 grm. of the salt gave by precipitation with HBr 0.4288 grm. 

 AgBr. 



Calculated for AgC3BrJ02. Found. 



Ag 23.32 " 22.98 



When dibromiodacrylic acid is heated to 100° in a closed tube with 

 bromine, iodine is set free and bromine takes its place. The substance 

 thus formed is identical with the tribromacrylic acid described by Pro- 

 fessor H. B. Hill and one of us* as shown by its melting point 115- 

 118°, and by a study of its crystalline form. The following angles 

 were measured by Dr. Melville : — 



Tribromacrylic Tribromacrylic 

 acid from acid from 



Angles between normals, dibromiodacrylic. brompropiolic. 



Zone [010, 110] 110 and 010 65° 33' 65° $8' 



48° 40' 



Zone [010, Oil] 010 and Oil 63° 11' 63° 14' 



53° 33' 



* These Proceedings, Vol. XVI. p. 216. 



