The Refractive Indices of Water Vapour, Air, Oxygen, Nitrogen, Hydrogen, Deuterium and Helium

The method described by Essen and Froome has been used to measure the refractive indices of water vapour, air, oxygen, nitrogen, hydrogen, deuterium and helium at a frequency of 9200 Mc/s. The value of (n-1)106 obtained for water vapour at 10 mm Hg pressure and 20°c is 60.7 which is the same as the value obtained at 24000 Mc/s, showing that the absorption line at 22000 Mc/s has a negligible effect on refractive index.