A general thermodynamics-related model of oxygen solubility, previously dev
eloped for water and aqueous inorganic solutions, has been applied to bleac
hing solutions. The model allows estimations of dissolved oxygen concentrat
ions to be made for different combinations of temperature, oxygen partial p
ressure and inorganic solute concentrations likely to be encountered during
oxygen bleaching of pulp. Combination of the model with oxygen diffusion k
inetics allows optimum temperatures for transport-controlled oxygen deligni
fication rates to be estimated.