HUeman — Al'kolirnet ric Estimation of Silicon Fluoride. 331 



The differences between the amounts of fluorine indicated 

 by the individual determinations in any one of these processes 

 are generally slight. The averages of the determinations by 

 potassium hydroxide and sodium hydroxide are very close 

 together, being 0*1411 grams and G'1415 grains of fluorine. 

 The average of the titrations by ammonium hydroxide is a 

 little higher, namely, 0-11:28 grams. That the differences 

 between these averages are due to gradual variations in the 

 reading tint is shown by a comparison of three titrations as 

 nearly simultaneous as possible, in which the greatest care was 

 taken to bring all to the same tint at the final reading. 



Table II. 

 Comparison of Simultaneous Titrations in Alcoholic Solution. 



Solution used. Fluorine Found, 

 cm 3. grm. 



Titration bv NH 4 OH 7-2 0-1414 



Titration b v KO H 1071 0-1418 



Titration by NaOH 9-13 0-1419 



So it appears that the results obtained are practically the 

 same by the three processes of neutralization applied to a 

 solution of fluosilicic acid. But it is to be observed that all 

 are possibly subject to a common and constant error due to the 

 presence of hydrofluoric as well as fluosilicic acid. If the 

 former acid is present it tends to raise the apparent value of 

 the latter. 



With these results of titrations in alcoholic solution are to 

 be compared the results obtained by the method of titration 

 in the water solution (in which the fluosilicate is completely 

 converted to fluoride), recorded in the following table : 







Table III. 









Titrations of Fluosilicic Acid in 



Water Solution. 





(Ac( 



jording to Offerman.) 





H.SiF, 



Standard 



Standard 



Fluorine 





Taken 



KOH 



INaOH 



Found. 



Average 



cm 3 . 



cm 3 . 



cm 3 . 



grm. 



grm. 



25 



309 







0-1358 "| 





25 



30-8 



.... _ 



0-1353 ! 



0-1358 f 



0-1355 



25 



30-9 







25 



30-79 





0-1353 J 





25 







26-2 



0-135 7 ) 





25 







26-15 



0-1355 j 





25 

 25 







26-25 

 26*2 



0-1360 ! 

 0-1357 [ 



0-1358 



25 







26'13 



0-1354 | 





25 







26-14 



0-1354 J 





