The methods of preparation of ferric hydrous oxide sots consisting of particles, uniform in shape, of narrow size distribution are described in detail. To produce such sots, acidic solutions, containing ferric ions and nitrate, perchlorate, or chloride ions, respectively, were aged at elevated temperatures for times ranging from a few hours to a few weeks. Solids formed from the solutions containing chloride consisted of either β-FeOOH or α-Fe2O3 depending on the concentration of ferric and chloride ions, whereas particles generated in solutions containing nitrate or perchlorate ions consisted of α-Fe2O3. Particle shape varied greatly as the conditions of colloid preparation were altered. It was possible to produce systems consisting of cubic, ellipsoidal, pyramidal, rodlike, and spherical particles. Such dispersions differed greatly in color. Complete domains are given in terms of ferric salt and corresponding acid concentrations which delineate regions of particle formation of given chemical composition and shape. Electrokinetic measurements show relatively small difference in point of zero charge for the various sots studied.

Ferric hydrous oxide sols

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Phosphorus binding by poorly crystalline iron oxides in North Sea sediments

Formation of ferric oxides from aqueous solutions: A polyhedral approach by X-ray absorption spectroscdpy: I. Hydrolysis and formation of ferric gels

Hydrolysis-precipitation studies of iron solutions. I. Model for hydrolysis and precipitation from Fe(III) nitrate solutions

A model for inorganic control of phosphate concentrations in river waters

Infrared and Mössbauer spectroscopy, electron microscopy and chemical reactivity of ferric chloride hydrolysis products

Mossbauer spectroscopic results indicated that aging the gel in a variety of ways produced poorly crystalline products (in agreement with their chemical reactivity) which had previously been identified as α-Fe 2 0 3 or mixtures of α-Fe 2 0 3 and α-FeOOH. The HFS of aged products as observed by Mossbauer spectroscopy is believed to be a sensitive indication of crystallinity; α-Fe 2 0 3 produced by heating the gel at 430°C for 48hr showed a 7% reduction in HFS compared to well-crystallized hematite. Finally, the thermal conversion of the gel to α-Fe 2 0 3 involved an intermediate structural state that was interpreted to mean considerable variety in the number and arrangement of ligands around the iron atoms, and a large distribution of magnetic fields. The state, observed after heating the gel for 18 hr at 320°C, gave an almost featureless Mossbauer absorption at room temperature.

Kenneth Kauffman

Papers

Infrared and Mössbauer spectroscopy, electron microscopy and chemical reactivity of ferric chloride hydrolysis products

Mössbauer spectroscopy of aged ferric oxide gels

Mössbauer analysis of cyanide reaction with ferric chloride hydrolysis products