Polytherm diagram of the ternary system KCl–FeCl2 –H2 O between 0 and 70C. Phase equilibria in the KCl–FeCl2 –H2 O system were studied over the temperature range 0–70C by conductimetric and analytical methods. A solubility polytherm of the system was constructed. We have observed the crystallization fields of the KCl and FeCl2 6H2 O (at 0C), KCl and FeCl2 4H2 O (at 15, 30 and 40C) and KCl, FeCl2 4H2 O and of a double salt KClFeCl2 2H2 O are obtained at 70C.