NOTE THE F ILM-FORMING ABIL IT IES OF IRON OXIDES AND

The ability of iron oxides to form coherent films is of particular interest o infrared spectroscopists. IR studies on iron oxides are usually carried out on samples that have been dried from suspension on AgC1 disks or dispersed in KBr pellets (Parfitt et aL, 1976). However, sharper spectra of the oxide, and also any adsorbate, are obtained if the oxide is examined in the form of a coherent, free-standing film.Such films of goethite (a-FeOOH) have been prepared, and found to be very suitable for both determining the orientation of hydroxyl bonds relative to the particle surface and for observing their involvement in chemical reactions (Cornell & Schindler, 1980). Preliminary experiments showed that other iron oxides, e.g. hematite (ct-Fe203) , did not appear to have the ability to form coherent films. It was decided to examine a series of iron oxides and oxyhydroxides for evidence of film-forming ability and to investigate he factors that determine this ability. The results of this study are reported here. Materials and methods Synthetic iron oxides and oxyhydroxides were prepared using conventional technique