Variation of Reaction Mechanism with Surface Conditions in the Reduction of Silver Salts by Hydroxylamine

Silver bromide oxidizes hydroxylamine at pH 10.2–10.8 to nitrogen and water. Under comparable conditions, silver thiocyanate yields a mixture of nitrogen and nitrous oxide as the gaseous products. By varying the surface conditions of the thiocyanate, the composition of the reaction product may be varied over a wide range. Small additions of bromide or iodide greatly decrease the nitrous oxide yield. With initial partial coverage of the precipitate surface by gelatin, the nitrous oxide yield increases to a maximum. Further gelatin additions progressively decrease the yield. Aging a fresh precipitate increases the nitrous oxide yield. The results are explained by the effects of adsorption upon the relative rates of two competing reaction mechanisms.