Electrolyte solutions in liquid ammonia—III☆The use of hydrogen electrodes

An apparatus is described with which it is possible to operate hydrogen gas electrodes on platinum in ammonium salt solutions in liquid ammonia. These electrodes have been shown to be reversible and to give stable, reproducible and accurate e.m.f.'s at −40°C over prolonged periods of time after an initial settling down period of 4–6 hr. The work proves conclusively that it will be possible to use hydrogen-on-platinum half-cells as primary standards for electrode potentials in liquid ammonia.