The Aerosol OT reversed micelle and the Schulman's reversed microemulsion with aqueous cores trapping dilute Fe2+ solution have been prepared and subjected to oxygenation by air at different temperatures between 30 and 70 °C. It was confirmed that the apparent rate of oxygenation reaction is enhanced for both the reversed micelle and reversed microemulsion by approximately 102-103-fold of that in bulk solution. By the air oxidation of the reversed microemulsion, in particular, precipitates appeared from the water pools. Electron micrographs of the precipitates showed sharp needles which are likely to be FeOOH crystals, indicating the building of a strongly alkaline environment in the aqueous cores. The probable causes of rise in pH and the resulting acceleration of overall oxidation reaction have been suggested.

Various α‐FeOOH samples have been prepared with or without addition of Cu(II) (0–5% Cu/Fe) and examined by X‐ray diffraction, BET surface area determination, electron‐microscopical observation and DTA. Doping with Cu in suitable amounts impedes completely the formation of α‐FeOOH. The mechanism of growth, based on the changes of particle size and crystallite dimension, appears to be different between pure and Cu‐doped α‐FeOOH. The reason of the remarkable effect of Cu on the crystallization process of α‐FeOOH is discussed. The effect of Cu is likely relevant to the role of Cu added to anticorrosive steel used in atmospheric environment.

The state of Cl in β-ferric oxide hydroxide (β-FeOOH) was examined by X-ray diffraction, IR absorption, chemical analysis, DTA, and TGA. The adsorption of SO2 was determined as a measure of the surface activity. No influence of Cl contained in the crystal appeared in the X-ray diffraction patterns and surface area. The absorption bands at 640 and 840 cm−1 in IR spectra showing the deformation vibration of OH group diminished with the decrease of Cl content. It was shown that the path for β-FeOOH to transform into α-Fe2O3 by heating differentiates from the sample including more than 11.5% Cl/Fe to one including less than 11.5% Cl/Fe. This critical Cl content is equal to the amount of Cl when Cl fills up the characteristic tunnels existing in the β-FeOOH crystal. Cl in β-FeOOH interferes both its transformation into α-Fe2O3 and the recrystallization of resultant α-Fe2O3. These effects were explained by the stabilization of the β-FeOOH structure by Cl in tunnels and the bonding between Cl and Fe. The amount of chemisorbed SO2 was lowered by Cl which was adsorbed on outer surfaces.

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