452 Wells and Metzger — Coesium- Antimonious Fluorides 



Upon comparing the caesium double fluorides with the salts 

 already known, it is to be noticed that two types of the former, 

 1 : 3 and 4 : 7, do not occur among the iatter, and that the 

 3 : 4, 3 : 2, 7 : 3, 3 : 1 and 4 : 1 types were not found among 

 the caesium-antimonious fluorides. The absence of a 3 : 2 fluor- 

 ide is remarkable, since the salt 3CsCl'2SbCl 8 is very spar- 

 ingly soluble, and because this is a very prominent type among 

 the chlorides, bromides, and iodides. It is evident that a close 

 relation does not exist between the caesium-antimonious fluor- 

 ides and the other antimonious double halides, and that the 

 types of the former could not have been predicted from a 

 consideration of the latter. In range, the caesium double 

 fluorides extend farther at the antimony end than the others, 

 while they do not extend as far at the alkali-metal end of the 

 series of types. 



When all the types of antimonious double halides are con- 

 sidered, they are remarkable for their large number, ten. This 

 number is probably greater than is the case with any other 

 negative element. The types, 1:3, 1 : 2, 4 : 7, 3 : 4, 1 : 1, 

 3 : 2, 2 : 1, 7 : 3, 3 : 1 and 4 : 1, with two or three exceptions, 

 are the simplest that can exist in such number between the 

 two extremes, and arithmetically they extend almost as far in 

 One direction as the other. 



Method of preparation. — Solutions of caesium fluoride and 

 antimonious fluoride were prepared by treating caesium car- 

 bonate and antimonious oxide, each with an excess of pure 

 hydrofluoric acid. To the antimonious solution the caesium 

 salt was gradually added in small quantities, and after each 

 addition the liquid was evaporated and cooled until crystalliza- 

 tion took place. If a homogeneous product was obtained a 

 portion was removed for analysis, and the process was con- 

 tinued until finally the liquid contained a very large excess of 

 caesium fluoride. In every case the products were carefully 

 inspected to make sure that they were not mixtures, and at 

 least two crops of a salt were always prepared under somewhat 

 different conditions, and were shown by analysis to be identi- 

 cal in composition before they were accepted as true com- 

 pounds. 



Method of analysis. — The crystals were carefully dried by 

 pressing between filter papers, and the portions to be analyzed 

 were preserved in glass weighing tubes which were coated 

 within with a very thin layer of parafline. For the determina- 

 tion of antimony and caesium a portion was heated in a plati- 

 num crucible with concentrated sulphuric acid until all the 

 hydrofluoric acid was removed, the residue was dissolved in 

 hydrochloric acid, antimony was precipitated as sulphide, col- 

 lected on a Gooch crucible and weighed after drying in a 



