Platinum pentafluoride has been prepared, by a new preparative method, in a more stable, pure and crystalline form than the material already described. It has been shown, by x-ray powder photography, to be isomorphous with other noble metal pentafluorides and almost isodimensional with rhodium pentafluoride. A tetrameric structural unit like that observed in ruthenium pentafluoride is also assumed for platinum pentafluoride. Its magnetic properties have been shown to be representative of a third transition series d⁵ ion in a distorted octahedral environment. The nature of the bonding in germanium difluoride is discussed in the light of the crystal structure, which has been deduced from data obtained from single crystals prepared in this work. The products of interaction of chlorine or bromine with the difluoride are consistent with the structural findings. The ¹⁹F n.m.r. spectra of the mixed chlorofluorides (GeFCl₃, GeF₂Cl₂, GeF₃CI, GeF₄ ) and bromofluorides, indicate that intermolecular exchange between these compounds must be extremely slow, at least in the absence of a catalyst. It has been shown that germanium difluoride is so strong a reducing agent that it reduces iodine pentafluoride to iodine below room temperature. The powerful reducing properties of the difluoride were also illustrated by the reduction of platinum tetrafluoride to the metal at room temperature. Attempts to reduce tungsten hexafluoride at 300° led to the formation of Ge₂WF₈. In glass the germanium difluoride reacted with tungsten hexafluoride and the container to yield WO₂F. / Science, Faculty of / Chemistry, Department of / Graduate