Wood-alkali interactions in agueous solution were described with Donnan equilibrium and ionic dissociation equilibrium theories. Theoretical models of three systems, NaOH-H2O-wood, NaOH-NaCl-H2O-wood, and NaOH-Na2CO3-H2O-wood, were developed. Theoretical predictions fit experimental data well. The theoretical modeling also shows good agreement with experimental results reported in the literature when applied to NaOH-H2O-cotton system. Theoretical simulations indicate that carbohydrate hydroxyl groups can be considered as mono-basic weak acids at alkali concentrations lower than 3 M. At higher alkalinities (> 3 M), however, further hydroxyl groups are also significantly ionizable.