PURPOSE:To form powdery hematite particles separated individually and independently by the reaction at high concn. at low temp. and for a short time by adjusting the pH of aq. suspension contg. beta-FeOOH to a specified pH by the addition of alkaline aq. soln., acidifying then the suspension by the addition of hydrochloric acid, and then subjecting the acidified suspension to the hydrothermal treatment. CONSTITUTION:Aq. suspension having =8 pH is obtd. by adding alkaline aq. soln. to aq. suspension contg. beta-FeOOH, then hydrochloric acid is added to the obtd. aq. suspension to obtain aq. suspension having =7 pH and contg. the beta-FeOOH. Thereafter, the finally obtd. aq. suspension is subjected to hydrothermal treatment at 100-130 deg.C, obtd. thus hematite particles having uniform grain size. By the above described process, formation of hematite particles is possible even if the concn. of the aq. suspension contg. beta-FeOOH is so high as ca. 1.0mol/liter.
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