Arsenic ivith Caesium and Rubidium. 91 



Prepared with Prepared with Calculated for 



excess of CsCl excess A sCl 3 3CsC1.2AsCl 3 



Cs 46*14 45*27 45-09 45'94 



As 17-15 17-11 17-27 



CI 36-89 36-74 36-12 36-79 



Calculated for 

 Pound. 3RbC12AsCl 3 



Rb 35-55 35-33 



As 20-14 2066 



CI ._ .._ 44-04 44-01 



Both salts can be recrystallized from hydrochloric acid of 

 sp. gr. 1*1. 100 parts of HC1 sp. gr. 1*2 dissolve *429 parts of 

 the caesium salt and 2*935 parts of the rubidium compound. 

 Since the corresponding potassium salt apparently does not 

 exist, these solubilities suggest a convenient method for obtain- 

 ing caesium and rubidium free from potassium. 



Ccesium and Rubidium Arsenious Bromides: SCsBr. 

 2AsB?\ and SRbBr .2AsBr r — These are amber-yellow, the 

 shade being somewhat darker than that of the chlorides. They 

 are most conveniently prepared by using an excess of the alkaline 

 halide. Strong hot solutions of the alkaline bromides were 

 made in about 40 per cent HBr. On adding crystals of AsBr 3 

 these melted but soon solidified to a yellow mass of the double 

 halide. This dissolved on boiling, and, on cooling, brilliant 

 yellow crystals were obtained. These compounds can be re- 

 crystallized unaltered from strong HBr. Analysis gave : 



Calculated for 

 Found. 3CsBr.2AsBr 3 



Cs 31-91 31-44 



As ._ 11-89 11-82 



Br 56-94 56-74 



Prepared with Prepared with Calculated for 



excess of RbBr excess of AsBr 3 3RbBr.2AsBr 3 



Rb -/3-35 22-77 



As 12-55 13-31 



Br 63-97 64-43 63-92 



Ccesium and Rubidium Arsenious Iodides: SCsI.2AsI 3 

 andZRbl ' . 2AsI y — These are deep red, the larger crystals of the 

 caesium compound are more opaque and appear black. To 

 prepare these compounds the normal alkaline iodides were dis- 

 solved in strong colorless hydriodic acid and these solutions 

 were then saturated boiling with crystals of AsT 3 . Unless the 

 hydriodic acid is decolorized the product obtained in the case 

 of the caesium salt is generally impure, being mixed with Csl 3 .* 



*This Journal, xliii, 17; Zeitschr. f. Anorg. chem., i, 85. 



