Solid-State Reaction between Iodine and Mercurous Halides
R. P. Rastogi, B. L. Dubey
The stoichiometry and kinetics of reactions, between (i) iodine and mercurous chloride, (ii) iodine and mercurous bromide, and (iii) iodine and mercurous iodide have been studied. HgClI is formedin reaction i and dissociates after some time into mercuric chloride and mercuric iodide. HgBrI and HgI2 are formed in reactions ii and iii, respectively. The stoichiometry is confirmed by gravimetric studies, chemical analysis, reflectance spectra, and thermal studies. The mechanism of lateral diffusion has been established by kinetic studies (a) when the reactants are kept in contact, and (b) when they are separated by an air gap of different length. The data for reaction i are best fittedby the equation ¤2 = 2kite-p¤ where ¤ is the thickness of product layer at time t, and p and ki, are constants. For the other two reactions ¤n = kt is obeyed by the data, where k and n are constants. It has been established that diffusion in the above reactions is predominantly controlled via vapor phase, although, in reactions ii and iii, diffusion by surface migration is also significant. The diffusion coefficient of iodine in air and the diffusion coefficient for surfacemigration have been experimentally determined. The inward penetration of iodine in the grains of mercurous halides has been investigated by gravimetric studies. In order to have an idea about themagnitude of energy changes, thermochemical studies in the solid state have been made. © 1967, American Chemical Society. All rights reserved.
