The Temperature of Inversion of the Joule-Kelvin Effect for Hydrogen 1

Abstract

IN the year 1854 it was proved by Joule and Lord Kelvin that hydrogen on free expansion behaved differently to all other gases. Air, when allowed to expand from a higher to a lower pressure without performing external work, became cooled, the fall of temperature being proportional to the difference of pressure; hydrogen, on the other hand, became warmer. As is well known, the Joule-Kelvin effect has been applied by Hampson and Linde to the liquefaction of air in quantity, but since for hydrogen the effect is of opposite sign, it was obvious that the Hampson-Linde apparatus could not be directly applied to the liquefaction of that gas; a conclusion which is confirmed by this research. There seemed no doubt,1 however, that after due modification the Hampson-Linde method would be applicable to the liquefaction of hydrogen, the necessary condition being that the gas should be cooled to below the temperature at which the Joule-Kelvin effect changes sign before entering the regenerator coil of the apparatus. Below this temperature the gas would become cooled on free expansion; as in the case of air in the ordinary Hampson apparatus, the cooling would be progressive and, were the heat insulation sufficiently perfect, would result in the partial liquefaction of the gas.