384 Hilenian — Estimation of Fluorine Iodometrically . 







Table I. 





a 2 SiF 6 



Standard 



Standard 



Fluorine found 





NaOH 3 



. Na 2 S 2 3 

 A 







(1cm 3 = 



(1cm 3 = 







0-005137 



0-002335 







of Fluorine) 



of Flaorine) 





cm 3 . 



cm. 



cm 3 . 



Grams 



25 



10-82 







00556 



25 



10-87 



■ 



0-0559 



25 



10-83 







0-0557 



25 







23-54 



0-0549 



25 







23-52 



0-0549 * 



25 





23-48 



0*0548 



25 







23-50 



0-0548 



25 







23-45 



0-0548 



25 







23-48 

 B 



0-0548 





(1cm 3 = 



(1cm 3 = 







0-005137F 



0-002441 







of Fluorine) 



of Fluorine) 





25 



9-08 







0-0466 



25 



9-05 



_ 



0-0464 



25 



9-05 







0-0464 



25 







18-78 



0*0458 



25 







18-80 



0-0459 



Calcium fluoride was treated in the apparatus figured by the 

 method described, the silicon fluoride was absorbed in water 

 and after separating the mercury used in the apparatus by 

 means of a separating funnel, the iodide-iodate mixture was 

 added to the solution and the iodine liberated was titrated by 

 sodium thiosulphate. 







Table II. 









l(cm 3 = 



= 002335) 







CaF 2 



Na 2 S 2 3 



Theory 



Found 



Error 



Gram 





Fluorine 



Fluorine 



Fluorine 



0-2500 



51-35 



0-1216 



0-1199 



00017 



0-23O0 



46-75 



0-1119 



0-1091 



0-0028 



0-2300 



47-15 



0-1119 



o-iioo 



00019 



•NaF 











0-2000 



38-50 



0-0903 



0-0899 



0-0014 



The average error of — 0*0019 grams is considerable greater 

 than that of the alkalimetric method, 0-0008 grams. It 

 appears, therefore, that, while the iodometric method of deter- 

 mining fluorine in fluorides may in special cases present some 

 advantages, it does not equal in accuracy the alkalimetric 

 method when it is properly conducted. 



