142 PROCEEDINGS OF THE AMERICAN ACADEMY 



Angles between Normals. 



Observed. Calculated. 



100 and 010 = 88° 48' 

 010 " 011=36° 3' 

 Oil " 001 = 48° 5U' 

 100 " 011 = 77°2U' 

 100 " ITO = 57° 25' 

 100 " 001 =1 77° 1' 76° 2V 



y Fundamental angles. 



Argentic Tetrabrompropionate, AgC3HBr^02 . Argentic nitrate 

 added to a solution of the acid in dilute alcohol jirecipitates the silver 

 salt in clustered needles, which may further be increased in quantity 

 by the cautious addition of ammonic hydrate. The salt is extremely 

 unstable, forms argentic bromide on warming, and blackens rapidly 

 in diffused light. 



1.2182 grm. of the salt dried over HgSO^ gave 0.4744 grm. AgBr. 



Calculated for AgCgHBr^O^ . Found. 



Ag 21.78 22.38 



Baric Tetrabrompropionate, Ba(CnHBr^02)2 • 2H2O. An aqueous 

 solution of the acid dissolved baric carbonate readily in the cold, and 

 if the solution was not warmed there was no noticeable decomposition. 

 On spontaneous evaporation at ordinary temperatures the barium salt 

 was left in clusters of flattened needles. When dried by exposure to 

 the air they contained two molecules of water which they lost over 

 sulphuric acid. 

 I. 0.7239 grm. of the air-dried salt lost over HgSO^ 0.0272 grm. 



II. 0.7087 grm. of the air-dried salt lost over H^SO^ 0.0259 grm. 

 Hp. 



Calculated for Ba( CsHBriO-Jz ■ 2H.p. Found. 



I. II. 



H2O 3.79 3.76 3.G6 



0.6756 grm. of the salt dried over H.SO^ gave on ignition with 

 H2SO, 0.1742 grm. BaSO, . 



Calculated for BaiCsHBriOo). . Found. 



Ba 14.97 15.16 



