The complete ladder of ΔG10determinations obtained from measurements of some 110 gas phase proton transfer equilibria A1− + A2H = A1H + A2−involving some 60 acids AH and connecting to the standard acid HCl is given. Evaluation of the entropy changes leads to values for the deprotonation energies ΔHD0and ΔGD0(at room temperature) corresponding to the gas phase process AH = A− + H+; ΔHD0 = D(A—H) − EA(A) + 313.6 kcal/mol. Comparison of the present data with literature determinations of the bond dissociation energies and electron affinities shows agreement within 2 kcal/mol. Some experimentally determined entropy changes ΔS10are compared with the theoretically calculated values.