[smith] 



DETERMINING REFRACTIVE INDICES 



149 



/ 

 / 



/ C 



7^ 



r 



t > , } t > J W J' 



/ 

 / 



'.A 



/ 

 / 

 / 

 / 



6 



1* / fl^in 



ne. 2 



kept cool by a wet rag or by a current of compressed air until the 

 remainder reaches its final temperature. The metal all condenses 

 here, and may then be entirely vapourized in a few minutes by a 

 bunsen flame. Thus it is unnecessary to watch the fringes during the 

 hour or more required to heat the furnace, and several readings^may 

 be taken at one heating. 



c 



A 





Fid 3 



As the change is from vacuum to the given density the actual 

 refractive index ^ is given by 



NX 

 ^"^= / 

 where iV is the number of fringes counted, X the wave-length and / the 

 length of the tube. , 



If we define a standard density po by the equation 

 Density of Hydrogen at 0° and 76 cms. 



Po = 



Molecular wt. of Hydrogen 



X Atomic weight of metal 



