228 //. L. Wdls — Ocesium-Mercuric Halides. 



Calculated for 

 -Found , Cs,HgBr.,. 



Caesium 33-84 34-43 33'69 33.84 



Mercury 25-68 25-11 25-45 25'45 



Bromine 40'4S 40-40 40-52 40.71 



100-00 9994 99-66 lOO'OO 



CsHgB)\. — This compound is dimorphous, but while one 

 form is cubic, like one of the chlorides, the other is mono- 

 clinic and has no apparent relation to the orthorhombic 

 chloride. Just as in the case of the chlorides, the cubic form 

 is produced when an excess of the caesium halide is present, 

 while the second form is deposited when this excess is not as 

 great. Unlike the corresponding chloride, the second form of 

 the bromide is decomposed by recrystallization from water, the 

 salt CsHg a Br B being formed, but, as will be noticed beyond, 

 the opposite transformation can be produced by recrystallizing 

 the last mentioned salt from alcohol. The limits of forma- 

 tion of the cubic salt are wide, but it is difficult to produce 

 the other form in a pure state, and it is possible that the mono- 

 clinic crystals analyzed were mixed with a small quantity of 

 the cubes. 



, Found N Calculated for 



Cubic. Monoclinic. CsHgBr 9 . 



Caesium 23-18 22-89 23-21 



Mercury... 34-95 3554 34.90 



Bromine 41-70 41-63 41-89 



99-83 100-06 100-00 



CsHg 2 B?\. — The recrystallization of any of the other 

 double-bromides from water produces this salt, and it can be 

 recrystallized indefinitely without decomposition. It forms 

 very small, thin plates which have a very faint tinge of yellow. 

 By spontaneous evaporation of a mother-liquor from a recrys- 

 tallization of this salt somewhat larger crystals were formed. 

 Three separate crops were analyzed. 



Calculated for 

 Found. CsHg 2 Br 5 . 



Cesium 14-60 14-69 13-24 14-26 



Mercury--- 42'7l 42-87 



Bromine 42-55 42.87 



99'86 100.00 



The mother-liquor from' a third recrystallization from water 

 at about 16° was found to contain Ol 151 per cent of caesium, 

 corresponding to solubility of O807 parts of CsHg 2 Br 5 in 100 



