Measurements of the scattering by crystals of NaCl, KCl, and KBr, containing ≈10−6divalent impurity concentration, at &lgr;4358 Å are reported for the temperature range 200°–1000°K. The results for equilibrium heat treatments are entirely reversible, but not for quench treatments. The equilibrium results are consistent with the predictions of the theory of charged dislocations and scattering theory for defect clouds associated with the dislocations. Formation energies for anion and cation vacancies are obtained, viz.: NaCl,g+=0.6,g−=1.4; KCl,g+=0.65,g−=1.75; KBr,g+=0.80,g−=1.40, energies in eV. Precipitation of impurities at dislocations occurs atT=273°, 213°, 223°K for NaCl, KCl, and KBr, respectively.