Abstract: Disclosed herein is fine acicular .alpha.-ferric oxide which has the crystallite diameter (D.sub.1014) in the direction perpendicular to the (1014) plane and the crystallite diameter (D.sub.1120) in the direction perpendicular to the (1120) plane such that their ratio D.sub.1014 /D.sub.1120 is in the range of 1-2, and also has a specific surface area of 40-50 m.sup.2 g. Disclosed also herein is fine acicular .alpha.-ferric oxide which has the crystallite diameter (D.sub.1014) in the direction perpendicular to the (1014) plane and the crystallite diameter (D.sub.1120) in the direction perpendicular to the (1120) plane such that their ratio D.sub.1014 /D.sub.1120 is the range of 1-2, and also has an average aspect ratio of 10-15 and a specific surface area of 20-40 m.sup.2 /g. They are produced by wet process including the step of hydrothermal reaction.

Abstract: Herein disclosed are a plasma treating method and an apparatus therefor. The plasma treating method comprises: the step of monitoring the energies of plasmas corresponding to the faces of a plurality of samples to be treated; the step of adjusting to equalize the energies of said plasmas on the basis of the monitored values; and the step simultaneously treating said samples with the plasmas having said equalized energies. The plasma treating apparatus comprises: a plurality of sample electrodes disposed independently of one another in positions opposed to an opposed electrode in a treating chamber evacuated to be supplied with a treating gas; power supply means for applying and adjusting electric power to said sample electrodes; and monitor means for monitoring the energies of plasmas to be generated between said opposed electrode and said sample electrodes.

Abstract: A method of producing single crystalline, acicular .alpha.-ferric oxide particles of narrow particle size distribution is provided. The method comprises heating an aqueous suspension of ferric hydroxide at temperatures of 100.degree.-250.degree. C. at an alkaline pH in the presence both a water soluble organic or inorganic compound capable of forming complexes with iron as a growth regulating agent and .alpha.-ferric oxide seed crystals of minor axes not larger than 0.4 microns in average in amounts of 0.1-25 mole % in terms of the Fe content thereof in relation to the ferric hydroxide.