and Some Other Double Halides of Antimony. 453 



small oven containing carbon dioxide. Caesium was weighed 

 as normal sulphate. Fluorine was determined by converting 

 it into silicon fluoride, collecting the latter in water, and. 

 titrating with sodium hydroxide, according to a modification 

 of Offermann's method. The results of these fluorine deter- 

 minations were invariably somewhat too low, as we found by 

 testing the method with pure potassium silicon fluoride ; hence 

 the chief value of these determinations consists in showing 

 that the salts under investigation were not oxy-compounds. 



1 : 2 Caesium- Antimonious Fluoride, CsF*2SbF 3 .— This 

 salt was obtained in the form of beautiful, transparent needles 

 by adding 2 or 2 g of caesium fluoride to a solution of about 50 g 

 of antimonious fluoride in somewhat dilute hydrofluoric acid 

 solution, heating to boiling and cooling. Two separate crops 

 gave the following results upon analysis : 



Calculated for Found. 



CsSb 2 F 7 . I. II. 



Caesium 26*28 26'44 



Antimony 47*43 47*36 47*42 



Fluorine 26-28 25*23 



1:3 Caesium- Antimonious Fluoride, CsF*3SbF 3 . — This 

 salt crystallizes in the form of stout, transparent prisms. It 

 was obtained by evaporating the mother-liquors from the pre- 

 ceding compound and cooling, or by the use of somewhat less 

 caesium fluoride in proportion to the antimonious fluoride in a 

 more concentrated solution. Two crops gave the following 

 results : 



Calculated for Found. 



CsSb 3 F 10 . I. II. 



Caesium 19"47 17*81 17*60 



Antimony 52*71 52*95 53*89 



Fluorine 2782 27"01 26*84 



The rather wide variation of the results from the calculated 

 quantities is probably due to the fact that the crystals were 

 taken from a very concentrated antimonious fluoride solution 

 and were consequently not quite pure, even after careful dry- 

 ing on paper. 



4, : 7 Caesium- Antimonious Fluoride, 4CsF*7SbF 3 . — This 

 salt crystallizes in transparent plates, and is formed in the 

 presence of a little larger proportion of caesium fluoride than 

 the preceding compounds. It was obtained, for instance, upon 

 adding about 4> of caesium fluoride to a mother-liquor from the 

 last salt and crystallizing by cooling. Two crops gave the 

 following results : 



