抄録
Ferric oxide powders were prepared by roasting of ferrous sulphate crystals in air at various temperatures and heating periods ranging from 630°to 800°C, 15-30 hrs respectively. Ferrous sulphate crystals used as raw material were obta-ined by crystallization from pickling liquor and waste sulfuric acid sulution by-produced in the process of titanium dioxide production from ilmenite ore (P and I denote for each specimens prepared by roasting of ferrous sulphate crystals obtained in the former and the latter processes respectively).
The physico-chemical properties of ferric oxide powders were examined by means of chemical and spectral analyses, X-ray diffraction and electron microscopy, measurements of specific gravity, specific surface area, particle size and especially dissolution rate in dilute hydrochloric acid solution.
The results were as follows. (1) Purities of P and I specimens are about 99. 0 and 95.0% as ferric oxide respectively, which contain Mn, Cu, Zn, Ti, Al, Mg, Pb, Si probably as oxides and both specimens give X-ray diffraction of a-Fe2O3 and irregular particle shape in electron microscopic photograph. (2) Values of specific gravity, specific surface area and particle size of each specimen are dependent upon their thermal histories as previously reported. (3) Though dissolution rate of ferric oxide powders in dilute hydrochloric acid solution also depends on their roasting conditions, the ratios of these values to their specific surface areas are almost constant for both P and I specimens except the I specimen prepared by roasting at 630°C for 16 hrs, which gives about two times surface activity per unit area in dissolution rate compared with the remainder.
