Abstract
Abstract Measurements have been made of the conductivity of single crystals of pure and doped ammonium chloride and of single crystals of caesium chloride and potassium chloride. Less detailed studies have been made of ammonium and potassium bromides and iodides, tetramethylammonium iodide, ammonium and potassium stannichlorides, and ammonium and rubidium fluophosphates. The conductivity of ammonium chloride is significantly greater than that of a comparable alkali chloride and reasons are given for believing that a conductivity mechanism operates in the ammonium salt which is not possible for the alkali metal salts. It is suggested that this mechanism is a three-stage process, involving (1) a proton switch from an ammonium ion to a chloride ion adjacent to a vacancy, which produces an ammonia molecule and a hydrogen chloride molecule, (2) the migration of one of these molecules into the vacancy and (3) a reverse proton switch to reform a pair of ions. Part of the evidence for this mechanism comes from a consideration of the thermodynamic properties of ammonium chloride, which are consistent with the view that even at room temperature and below the formation of molecules within the lattice takes place to a significant extent.
Published Version
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