Interaction of silver molybdate and mercuric bromoiodide in solid state

Abstract

The kinetics and the mechanism of the solid-state reaction between silver molybdate and mercuric bromoiodide were studied. Ag 2MoO 4 and HgBrI react in an equimolar ratio at room temperature to give Ag 2HgI 4, AgBr, AgI, and HgMoO 4 whereas AgI, AgBr, and HgMoO 4 are the end products when the same mixture is heated at 100°C for 24 hr. The mechanism of the reaction has been established by X-ray diffraction analyses and thermal and electrical conductivity measurements. The kinetics have been studied by visual technique. The rate of product thickness follows the parabolic rate law, x 2 = kt, x being the thickness of product layer at time t and k the parabolic rate constant. This is multiple solid-state ionic reaction, controlled by diffusion of HgBrI molecules and not by counter diffusion of cations. The diffusion coefficient of HgBrI for vapor phase and surface migration were determined.