In the Ni(II)-S(IV)-O 2 system in the region of pH > 8.4, both Ni(II) and S(IV) are simultaneously autoxidized, and when sulfur is consumed fully NiOOH precipitates. At pH > 8.4, ethanol has no effect on the rate, whereas ammonia strongly inhibits the reaction when pH > 7.0. The kinetics of the reaction, in both the presence and the absence of ethanol, is defined by the rate lawwhere k is the rate constant, K O is the equilibrium constant for the adsorption of O 2 on Ni(OH) 2 particle surface. In ammonia buffer, the factor F is defined by