Mixed metal oxides iron compounds

The Sr24 and Ba2+ salts of the ferrates(IV), Sr2Fe04 and Ba2Fe04, may be prepared by oxidation of a mixture of hydrated iron(III) oxide with the alkaline earth metal oxide or hydroxide with oxygen at 800-900°C (equation 40).478 These black compounds do not contain discrete [Fe04]4 ions and are really mixed metal oxides. They are readily decomposed by mineral acids to Fe111 and 02. Vibrational spectra of some of these systems have been recorded.479... 

Mixed oxides of Fe(IV) can be prepared by heating iron(III) oxide with a metal oxide or hydroxide in oxygen at elevated temperatures. These black compounds have general formulas M FeO, M monovalent, or M2Fe04, M divalent, but do not contain discrete [FeOJ" ions. They are readily decomposed by mineral acids to iron(III) and oxygen. 

Planar M30 units occur in the basic carboxylates of such metals as iron, ruthenium, manganese, vanadium and chromium the chromium compound has been known since 1919. The metal atoms are also linked by pairs of carboxylate ligands (often acetates), and have terminal ligands (generally pyridine or water). Mixed metal units, e.g. Fe2CrO,124 and mixed oxidation states, e.g. Ci CifO,1 ... 

One example is the displacement reaction. Aluminium is more reactive than iron to put it another way, aluminium forms positive ions more easily than iron does. Iron(IlI) oxide is an ionic compound it contains positive iron ions and negative oxygen ions. If you mix aluminium metal with iron oxide, and provide some energy by heating the mixture, the aluminium atoms will give up electrons and force them on to the iron ions, thus converting the iron oxide into metallic iron ... 

In all fractions, ganuna-alumina was the only alumina phase detected. The finos contained significant amounts of a mixed-metal vanadate phase, denoted by the peaks labelled as "3." This mixed-metal phase nay be composed of iron-vanadium-oxide or iron-vanadltjun-molybdenum oxide, based on XRD patterns of available reference compounds. The extrudates, on the other hand, are dominated by peaks due to aluminum sulfate, "1," and vanadium pentoxide, 2," with little if any peaks due to the mixed-metal phase, 3."... 

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