To separate ammonium dinitramide from the reaction mixture obtained in the reaction between NO2HS2O7 and nitramine in acetonitrile and subsequent neutralization with NH3 (aqua) the following procedure was applied: separation of the solid precipitated during the reactions; evaporation of the acetonitrile solution; extraction of the obtained solid with isopropanol; evaporation of the isopropanol solution; crystallization this way obtained crude ammonium dinitramide from ethyl acetate. According to the crude ammonium dinitramide concentration in the crystallization solvent, products with various compositions were obtained. For determined concentrations good yield and selectivity of the crystallization were attained. IR, TG, DTA and elementary analysis examined the selected products of the separations what allowed connecting the recorded spectra and thermographs with determined purity of ammonium dinitramide samples.