Thermal decomposition of antimony oxyhalides

The thermal decomposition of SbOCl, Sb4O5Cl2 and Sb8O11Cl2 has been studied by thermogravimetry with identification of the products resulting in the condensed phase by X-ray diffraction and infrared technique. It is shown that in nitrogen SbOCl undergoes progressive stepwise thermal disproportionation to Sb2O3 and SbCl3 with formation of Sb4O5Cl2 and Sb8O11Cl2 and as intermediates. It is thus confirmed that Sb3O4Cl, suggested to be formed instead of Sb8O11Cl2, is not an intermediate of this process. An identical mechanism is observed in air but with oxidation of Sb2O3 to Sb2O4.