The rates of sublimation of ammonium chloride, bromide, iodide, and fluoride have been determined by two different experimental techniques over the temperature range of 100deg; to 600deg;C, corresponding to an increase in sublimation rate of 104. The two experimental methods employed were the isothermal rate of weight loss using a quartz spring balance, and the hothyphen;plate linear pyrolysis method. The low activation energy (about onehyphen;third the heat of sublimation) found for ammonium chloride by earlier investigators has been verified and found to extend to the other halides. The frequency factor is also abnormally low for the ammonium halides, by a factor of roughly 104, with the exception of the fluoride, for which the factor is only about 500. These results are in fair agreement with the Schultzmdash;Dekker mechanism for ammonium halide sublimation.
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