In the ammonium chloride crystallization region of the NH₄Cl-CuCl₂-H₂O-CH₃ON system, cocrystallization of the impurity with the main substance occurs by epitaxial adsorption of complexes of varying composition. In NH₄Cl crystals, the Cu²⁺ impurity forms oriented interlayers (ingrowths) simultaneously at the macro-and microlevels. The ratio between the two trapping forms depends on the growth conditions.