TABLE 41 2 

 INDEX OF REFRACTION 



Indices of Refraction of Oases and Vapors 



373 



A formula was given by Biot and Arago expressing the dependence of the index of refraction of a gas on pressure and 



temperature. More recent experiments confirm their conclusions. The formula is n, — i r= : / -— > where 



K i -\- at 760 



n, is the index of refraction for temperature t, n for temperature zero, a the coefficient of expansion of the gas 



with temperature, and / the pressure of the gas in millimeters of mercury. For air see Table 4'3" 



Smithsonian Tables. 



