| 摘要 |
Chromium oxide with an average valency of 4 or higher, containing at least about 0.01 mol of nitrate(s) other than those of alkali metals (partic. alkaline earth, Pb, Th, Cr, Mn, Ni, Tl) is calcined at 250-500 degrees C. Nitrate and oxide may be formed by using dichromate and nitric acid. - Improvers containing an alkali metal (compound) and a heavy metal (or oxide, fluoride or sulphate) may also be present. Pressure may vary from reduced pressure of 400 mm Hg to overpressure; time of heating is 0.5-50 hrs. - The product has rutile structure.
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