Voltammetric study of ammonium amalgam

Abstract

Ammonium amalgam formation has been studied at mercury ultramicroelectrodes in various organic solvents and at standard size mercury electrodes in aqueous solution. Numerical simulations were carried out in order to establish the kinetics of the process. Ammonium amalgam is formed via a fast charge-transfer process, but it undergoes a decomposition according to the first-order rate law with a rate constant of about 0.6 s −1. In addition, some NH 4 + ions are irreversibly discharged at the electrode surface, presumably to form H 2 and NH 3. This competing process is affected strongly by the nature of the solvent. Matching of experimental and simulated curves suggests that the diffusion coefficient of NH 4 in mercury is about 1.8 × 10 −5 cm 2 s −1. The standard potential of NH 4 +(aq)/NH 4(Hg) was determined to be −1.723 V/SHE. The absolute chemical potential of ammonium ions in mercury was calculated and compared with that of alkali metal ions.