The chemical constants of the vapours of hydrogen and of hydrogen chloride; and the entropy change accompanying the reaction H 2 + Cl 2 ⇄ 2HCl

Abstract

In a paper called “The Chemical Constant of Hydrogen Vapour, and the Entropy of Crystalline Hydrogen,” the writer has investigated the vapour pressure of crystalline hydrogen at very low temperatures. He used the Einstein-Bose statistics for the hydrogen gas, and obtained results slightly different from those of Fowler, who had used the classical statistics for the vapour phase. The result found by the writer for the chemical constant i ' was in slightly better agreement with experiment than Fowler’s result, being larger than Fowler’s by log 10 1·04 = 0·02 at the temperatures of Eucken’s experiments. Also, the writer found that when hydrogen gas was condensed to the solid phase at these very low temperatures, the ratio of the number of ortho-hydrogen molecules to the number of para-hydrogen molecules in the crystalline phase, provided that most of the molecules were in the gaseous phase, was not 3 : 1 but instead about 3 ⅙ : 1. However, there was a mistake in the writer’s calculations. He carelessly omitted, from equations (5) and (5') of his paper on hydrogen, the factors involving the work of evaporation χ at the absolute zero, per molecule.