Oxides of Zirconium

It has already been seen that zirconium is usually quadrivalent. Nevertheless the sesquioxide Zr₂O₃ exists, though probably not the monoxide ZrO. Winkler believed that the monoxide ZrO is formed when zirconia is heated with magnesium in a current of hydrogen, and this opinion was supported by the work of Dennis and Spencer; Wedekind, however, failed to obtain a lower oxide by the reduction of zirconia with magnesium; the existence of the monoxide must therefore be considered doubtful.