The reaction of hydrogen chloride with liquid sodium and a sodium-barium alloy

Abstract

The reaction of hydrogen chloride with ligand sodium and sodium containing 4 At% dissolved barium was studied in the temperature range 100–250°C. The reaction took place in two distinct steps: (1) HCl → 1 2 H 2 + Cl − and (2) 1 2 H 2 → H − , with only the first step involving hydrogen chloride. The effect of barium was to decrease the rate of the hydrogen chloride reaction, step (1), but to increase that hydrogen, step (2). However, in both cases molecular hydrogen was produced quantitatively in the gas phase, indicating the absence of net hydrogen uptake in the presence of unreacted hydrogen chloride. The initial reaction of hydrogen chloride with pure sodium exhibited autocatalytic behavior. A reaction scheme was suggested in which the rate controlling process would be the growth of crystalline sodium chloride on the metal surface. In the presence of barium, however, barium chloride was the predominant product, and the hydrogen chloride reaction rate was found to decrease with time. The rate controlling process in this case was considered to involve diffusion of hydrogen chloride molecules through pores created in an otherwise protective barium chloride layer. Thus in each case, the overall reaction of hydrogen chloride was controlled by processes involving the solid reaction products. In contrast, under the conditions employed, the kinetics of the hydrogen reaction reflects the nature of the reactants.