The differential and integral enthalpies ( Δ H L and ΔH L) and entropies ( Δ S L and ΔS L ) of water adsorption by mixtures of montmorillonite and humate were calculated from calorimetric and multitemperature vapour adsorption measurements. Both methods gave identical values of enthalpies and entropies. The differential and integral enthalpies ( Δ H L and ΔH L ) of water adsorption by montmorillonite and humate and their mixtures are negative. The differential entropies ( Δ S L ) of montmorillonite, humate and their mixtures are negative and increase with the increase in water adsorption. The integral entropies ( ΔS L ) of water adsorption by the pure montmorillonite are negative and by the pure humate and mixtures (> 10% humate) are positive. By increasing water adsorption, the integral entropy increased for montmorillonite and decreased for humate and mixtures. It seems that water on the surface of humate is less ordered than on the surface of montmorillonite. The integral enthalpies like that of vapour adsorption, surface areas and heat of wetting are not additive for mixtures.