Ammonium lanthanide double sulphate dihydrates

Abstract Ammonium lanthanide double sulphate dihydrates NH 4 Ln(SO 4 ) 2 · 2H 2 O ( Ln ≡ Er , Tm , Yb , Lu and Y ) were synthesized and characterized by chemical, infrared, thermal and X-ray diffraction methods. The X-ray data showed that the crystals are monoclinic, space group P 2 1 / c , with four formula units per unit cell. The compounds are structurally isomorphous with KLu(SO 4 ) 2 · 2H 2 O reported in the literature, and the metal ion is coordinated to eight oxygen atoms. The infrared spectra suggested that both water molecules are coordinated to the metal ion. The compounds lost both water molecules between 120 and 225°C. The heat of dehydration was calculated from measurements of the peak area under the differential thermal analysis curve, recorded during thermal dehydration of the compounds. It showed satisfactory agreement with the heat of dehydration obtained by the solution calorimetric method for NH 4 Lu(SO 4 ) 2 · 2H 2 O.