20 



Wells and Foote- 



-Double Fluorides, etc. 



was added in slight excess to the filtrate and all the ammonia 

 was removed by evaporation. To the hot solution calcium 

 nitrate was added, and the resulting precipitate, after ignition, 

 was cautiously treated with dilute formic acid until, after 

 evaporation on the water-bath, a further addition of the acid 

 produced no effervescence. The calcium fluoride finally 

 remaining after a final evaporation was washed, ignited and 

 weighed. The results of the fluorine determinations were 

 invariably somewhat low. 



The substitution of formic acid for the acetic acid usually 

 used in removing calcium carbonate from the fluoride was sug- 

 gested by the greater volatility of the first acid and the solu- 

 bility of its calcium salt. We have found the modification to 

 be an improvement as far as convenience is concerned, but we 

 are not yet prepared to say that it is more accurate than the 

 old method. 



Water was determined by heating the substance in a boat 

 behind a layer of dry sodium carbonate in a combustion-tube, 

 and collecting and weighing it in a calcium chloride tube. 



The following analyses of separate crops were made : 



Caesium 



Zirconium 



Fluorine . 



A. 



56-41 



18-94 



22*73 



2CsF 

 B. 



19-30 



22*75 



0-98 



ZrF 4 

 C. 



55-51 

 19-16 



0-97 



Calculated 

 56-60 

 19-15 

 24-25 



Water 



1-63 





The small amount of water found in the analyses was evi- 

 dently mechanically included, for, under the microscope, bub- 

 bles of mother-liquor could be occasionally seen within the 

 crystals. 



CsF . ZrF 4 . H a O 

 A. B. Calculated. 



Caesium 38-44 39*58 



Zirconium. 27*19 27*11 26*79 



Fluorine _ 27*24 27*52 28*27 



Water _ 6*27 5'20 5*36 



2CsF.3ZrF 4 .2H 2 

 A. B. Calculated. 



Caesium 32*03 30*56 31*74 



Zirconium 32*45 33*48 32*22 



Fluorine 31*09 30*43 31*74 



Water. 4*40 3*96 4*30 



Sheffield Scientific School, 

 New Haven, Conn., July, 1895. 



