Antimony with Rubidium. 271 



was then used to precipitate the antimony and, when the solu- 

 tions had cooled, the resulting sulphide was filtered on asbes- 

 tos in a Gooch crucible, washed with water and alcohol and 

 then heated to 230° in an oven filled with carbonic acid. On 

 cooling, the sulphide was weighed as Sb 2 S 3 . The rubidium 

 was determined bj^ evaporating the filtrate from the antimony 

 sulphide to dryness with an excess of sulphuric acid, the 

 residue was then converted into normal sulphate by ignition 

 in a stream of air containing ammonia. The atomic weights 

 used in the calculation of results were the following : 



CI, 35-5; Br, 80; I,-127; Sb, 120; Rb, 85'5 



The Double Chlorides. 



The crystals of the double chlorides are colorless, with the 

 exception of the salt 3RbCl . 2SbCl s ; this salt has a pale yellow 

 color exactly similar to the salts 3RbCl. 2AsCl 3 and 3CsCl . 

 2AsCl,. The stability of the double chlorides, on exposure, 

 appears to vary inversely with the quantity of antimony chlo- 

 ride which they contain. 



1 : 2 Rubidium Antimony Chloride, RbCl . 2SbOl 3 . Hfi. 

 — This new salt was obtained from hydrochloric acid solution 

 when the constituents were mixed in the proportion of ten, 

 eight or six molecules of SbCl, to one of RbCl. On concen- 

 trating these mixtures supersaturated solutions were obtained 

 which sometimes remained for days without giving crystals, 

 but on shaking or stirring with a glass rod the crystallization 

 was induced. The crystals separate in the form of elongated, 

 colorless, monoclinic tables. Analysis of different crops gave : 







From 







From solution 



solution 



Calculated 



From solutions of 



of 8SbCl 3 to 



of 6SbCl 3 



for 



10SbCl 3 to lRbCl. 



lRbCl. 



to 1 RbCl. 



RbC1.2SbCl 3 .H 2 0. 



Rb 14-61 14-71 14-74 



14'64 



15-07 



14-44 



Sb 40-75 40-97 41-09 



41-07 



40-97 



40-54 



CI 41-83 41-53 4M1 







41-98 



HO 3-20 3-10 3-18 



3-08 





3-04 



The crystals of this salt have a brilliant luster when first re- 

 moved from the mother liquor, but on exposure they soon 

 lose their luster, becoming opaque and decomposing. In the 

 preparation of this salt for analysis the crystals were crushed 

 and thoroughly pressed on filter paper, and when it was certain 

 that the powder did not contain any mechanically mixed water, 

 it was placed in a weighing tube. This salt is readily dis- 



