6 Messrs. J. H. & G. Gladstone on the Refraction and 





B. 



D. 



p. 



a. 



10-79 

 10-52 



•27 



H. 



10-84 

 10-65 



19 



CnF, 



Ca 



F 2 



1060 

 10-05 



•55 



1064 

 1015 



•49 



1072 

 1033 



•39 



Sarasin (Ar. Geneve, x. 1883) gives the refractive indices 

 of fluor-spar from the line A to very far into the ultra-violet. 

 In the figures so given there seems to be no break, but a 

 regular progression quite comparable with that of quartz. It 

 is only possible for us to calculate the amount due to fluorine 

 up to the line H. 





E A- 



Ra- 



R B . 



R c . 



10-61 

 10-08 



R D . R F . 



R,, 



R n . 



CaF 2 



Ca 



10-57 

 1000 



10-59 

 1003 



10-60 

 10-05 



10-64 10-72 

 10-15 j 10-33 



10-82 

 10-57 



•25 



10-84 

 10-65 



19 



?* 



•57 



•56 



•55 



•53 



•49 -39 



All these different calculations from the indices given by 

 different observers show not only the small atomic refraction 

 for fluorine, but also a regular decrease on proceeding from 

 the less refrangible to the more refrangible portion of the 

 spectrum. 



Potassium Fluoride. — We have made two observations on 

 aqueous solutions of potassium fluoride. They were separate 

 preparations of the salt. 





Per cent. 



Temp. 



d. 



/*A- 



/i H . 





3964 

 34-24 



o 

 25 



135 



1-413 

 1-3306 



1-3593 

 1-3541 



1-3741 

 1-3692 



! 







These give the following molecular refractions, from the mean 

 of which we have deducted the value for potassium : — 



