The intrinsic deprotonation constant (pK(a2)(int)) and the intrinsic ion exchange constants (pK(Me+)(int)) of Li+, Na+, and K+ on SiO2 were uniquely determined at 30degreesC by using the potentiometric titration data, the Gouy-Chapman-Stern-Grahame (GSCG) model for the structure of the electrical double-layer (edl) and the double-extrapolation method. The values of these constants were pK(a2)(int) = 6.57, pK(Li+)(int) = pK(Na+)(int) = pK(K+)(int) = 5.61. The chemical meaning of intrinsic equilibrium constants and the equality in the values of pK(Li+)(int), pK(Na+)(int) and pK(K+)(int) were discussed.