Binary iron oxides

Iron Blocks. Chemically, iron blacks are based on the binary iron oxide, FeOFe2 O3. Although the majority is produced in the cubical form, these can also be produced in acicular form. Most of the black iron oxide pigments contain iron(III) oxide impurities, giving a higher ratio of iron(III) than would be expected from the theoretical formula. 

Tabk 10.1 Mossbauer parameters for binary iron oxides and hydroxides... 

Iron reacts with nonmetals forming their binary compounds. It combines readily with halogens. Reaction is vigorous with chlorine at moderate temperature. With oxygen, it readily forms iron oxides at moderate temperatures. In a finely divided state, the metal is pyrophoric. Iron combines partially with nitrogen only at elevated temperatures. It reacts with carbon, sulfur, phosphorus, arsenic, and silicon at elevated temperatures in the absence of air, forming their binary compounds. 

We can start, as did the ancient craftsmen, with the fusion of the iron oxide, FeO, with silica, SiO . The phase diagram for those binary mixtures show that whereas Si02 fuses at about 1713 C and FeO at 13 9 C, mixtures containing between 20 and 40 weight percent FeO fuse below 1250 C. Complexing with additions of another iron oxide, Fe203, in amounts of up to 10%, can lower the fusion temperature to about 1150 C. 

Binary Nitric Oxide Complexes. A binary iron nitrosyl complex is not known, although described in early reports as [Fe(NO)4], the compound having that stoichiometry is a dimer with an N2O2 bridging ligand (10). 

Attention will then be turned to the major oxide minerals MgO, AljOj, and SiOj and the binary transition-metal oxides of Ti, Mn, and Fe, with some brief discussion of the series of transition-metal monoxides (MnO, FeO, CoO, NiO) and complex oxides (FeCr204, FeTiOj, etc.), and of the problem of the calculation of Mossbauer parameters in iron oxides (and other compounds). 

Wang et al. (18) have studied binary and ternary mixtures of titanium oxide with zirconium oxide, vanadium oxide and iron oxide, among others. They reported that the by-products are produced in small amounts. Some mixtures are as active or more active than the iron oxide catalyst but are less selective. These researchers noted that in addition to the aforementioned reactions, reactions 3 to 5, the following reactions are significant ... 

There is a lot of oxygen in the atmosphere, and over the millions of years since the Earth was formed many metals have combined with oxygen to form compounds called oxides. Iron, for example, occurs in the molten core of our Earth, and is often found in the Earth s crust as the ore haematite, which is iron oxide. Iron oxide is a binary compound, which means it contains only two elements. Notice that its name ends with ide . This is true for all binary compounds. Metals tend to combine with non-metals. Where a binary compound is made up of a metal and a non-metal, the first name of the compound is simply the name of the metal it contains and the second is the name of the non-metal, changed to end in ide for example, the compound between copper and chlorine is copper chloride. 

The -Alumina-related Structures.—Originally the compound )3-alumina was taken to be a binary aluminium oxide, but early Y-ray structure determinations and associated chemical analysis showed that the formula was approximately NaAlnOi7. Since then a number of isostructural compounds have been characterized in which sodium is replaced by other monovalent ions, particularly silver, and aluminium by other trivalent ions, notably gallium and iron. In addition, a number of other phases have been prepared which are structurally closely related to )8-alumina. Four principal structures are known, which are labelled / ", and P"". These can also be prepared with other monovalent cations replacing sodium, and some seem only to be formed when a few per cent of divalent cations, particularly magnesium, are present, so that they are, in fact, quaternary phases. The structure and stoicheiometry of these compounds has been summarized recently and we will only consider here those aspects relevant to the present topic. 

Suppose you were asked to name the compound with the formula FeO. Following the method for naming simple binary compounds, we would get iron oxide. The problem is that there is more than one form of iron oxide. There is another compound, for example, with the formula Fe203, which you might also call iron oxide. How do we differentiate between the names of the two compounds ... 

Concept of molecular ratio of iron oxides. Why does the activity show hump)-type curve (binary peak) with the ratio of Fe +/Fe + At first, someone suggested that it is possible the result of the increasing contents of iron in the catalysts. However, it is seen from Fig. 3.28 that the activity displays the hump-type curve along with the increasing Fe +/Fe + and this kind of difference of activity is not caused by the changing contents of the iron. Because the contents of the iron increase monotonicaUy with the increasing Fe /Fe " ", while the activity does not. 

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