Effective charges of Bjerrum and ionic defects were estimated from temperature dependences of the dispersion strength of pure ice : eDL=0.374e and e±=0.626e. From those effective charges and measured conductivities of HCl-doped ice, conductivity components of point defects were derived, showing the existence of a crossover behavior, which is an exchange of roles between two types of point defects. Analyses gave the dissociation energy of HCl in ice 0.65±0.018 eV and migration energies of L and positive ionic defects are 0.190±0.017 eV and nearly zero respectively