The rate of stabilization of hydrocellulose and glucose against alkaline degradation by hydrogen sulfide was studied as a function of pH and H2S-concentration. The rate of this reaction increases to a maximum with an increase in pH from 3.5 to 6.3. The maximum rate is significantly enhanced by the presence of ammonia base. With increasing H2S-concentration, the stabilization rate increases in a sigmoidal manner. It is demonstrated that this kinetic pattern is in full accordance with the reaction mechanism proposed by Procter involving conversion to a thioalditol via a gem-dithiol intermediate.