Refraction and Dispersion of Fluorbenzene. 





Per cent. 



Temp. 



C. 



Density. 



Pa- 



/i r 



/%• 



Hydrofluosilieic acid.... 



36-72 

 22-80 



o 



14'3 

 110 



1-3918 

 1-2198 



1-3431 

 1-3390 



1-3507 

 1-3472 



1-3568 

 1-3536 



The next table gives the molecular refraction calculated 

 from these two sets of observations ; and from the mean value 

 is deducted the usual values for hydrogen, and the following- 

 values for silicon, viz. R A =7'07, R F = 7*26, and R H = 7'39. 





Per cent. 



B A . 



»r 



E H . 



Hydrofluosilieic acid ... 



36-72 



22-80 



15-02 

 15-05 



15-13 

 15-32 



15-22 



9-90 



15-21 

 15-47 



15-34 

 1007 



Mean value H 2 SiP 6 



H 2 Si 



1503 



9-67 



F 6 



5-36 



5-32 



5-27 



which gives the R A for fluorine = 0*89, and a scarcely per- 

 ceptible negative dispersion. It is of course quite possible 

 that in the case of this acid also the refraction may be raised 

 above the normal. 



Solid Fluo silicates. — Messrs. Topsoe and Christiansen have 

 determined the refraction of a number of crystalline fiuo- 

 silicates for the lines C, D, and F. Unfortunately only one 

 of these belongs to the regular system of crystals, viz. the fluo- 

 silicate of ammonium. The refraction-equivalents for this 

 one are given below, and from these are deducted the values 

 for silicon and ammonium. 





E c . 



E D . 



R F 



(NELVSiF, 



3314 



27-78 



33-26 

 27-93 



33-50 

 28-36 



(NH^oSi 





F R 



5-26 



5-33 



5-14 





