The dependence of the pseudopotential of free ions on the ion core electron structure approximation and on the description of the exchange and correlation scattering and pseudopotential non- locality are discussed. An analysis is made of the Phillips-Kleinman method. The formfactors for 17 elements are calculated. The problem of the pseudopotential ambiguity is discussed on the basis of the Hartree-Fock Hamiltonian with nonorthogonal one-particle wave functions. It is shown that in the weak bond approximation the effective potential is unambiguous.