It is shown that the failure of wool to reach equilibrium with alkaline solutions under the conditions of titration experiments is due to the reaction of base with the disulfide groups of the cystine. The results indicate that the extent of this reaction can be determined. The data also afford confirmation of the earlier observation that the alkali degradation of the cystine in wool involves the loss of only one sulfur atom from each cystine residue.The apparent base-combining capacity increases with increasing duration of contact of wool with alkali and with increasing temperature, but the intrinsic base-combining capacity, obtained by making corrections for the dissolved, protein and for the base bound by the sulfhydryl groups, becomes constant after approximately two hours. The most consistent data are obtained at a low temperature where, it appears, secondary reactions are greatly inhibited.Determination of the amount of base absorbed from solutions of various concentrations indicates that a limiting amount of about 0.7 millimole per gram of wool is reached above concentrations of about 0.2 N sodium hydroxicte. Because of discrepancies in the data obtained at concentrations greater than 0.3 N, it is suggested that this value be considered for the present as tentative.