Magnetite formula

When mild steel is heated in air at between 575 and 1 370°C an oxide or scale forms on the steel surface. This scale consists of three well-defined layers, whose thickness and composition depend on the duration and temperature of heating. In general, the layers, from the steel base outwards, comprise a thick layer of wiistite, the composition of which approximates to the formula FeO, a layer of magnetite (FejOJ, and a thin layer of haematite (FejO,). 

Give the systematic name and chemical formula of the principal component of (a) magnetite (b) malachite ... 

Beyond these two columns, the removal of all valence electrons is usually not energetically possible. For example, iron has eight valence electrons but forms only two stable cations, Fe and Fe. Compounds of iron containing these ions are abundant in the Earth s crust. Pyrite (FeS2) and iron(II) carbonate (FeC03, or siderite) are examples of Fe salts. Iron(IIt) oxide (Fc2 O3, or hematite) can be viewed as a network of Fe cations and O anions. One of the most abundant iron ores, magnetite, has the chemical formula FC3 O4 and contains a 2 1 ratio of Fe and Fe cations. The formula of magnetite can also be written as FeO FC2 O3 to emphasize the presence of two different cations. 

From this equation It Is clear that a plot of M/Mg versus MgpH/3kT will yield a line with slope v /v. The only unknown In this equation Is the value of Mg. Assuming that this does not change as a function of particle size (no dead layers) this can be determined for magnetite from the formula of Pauthenet (23) ... 

Magnetite differs from most other iron oxides in that it contains both divalent and trivalent iron. Its formula is written as Y[XY]04 where X = Fe , Y = Fe " and the brackets denote octahedral sites (M sites). Eight tetrahedral sites (T sites) are distributed between Fe" and Fe", i.e. the trivalent ions occupy both tetrahedral and octahedral sites. The structure consists of octahedral and mixed tetrahedral/octahedral layers stacked along [111] (Fig. 2.13a). Figure 2.13b shows the sequence of Fe- and O-layers and a section of this structure with three octahedra and two tetrahedra is depicted in Figure 2.13 c. 

The permanent moments of the cations in the octahedral and tetrahedral sites are antiparallel. Thus, the moments of the trivalent cations (Fe +) cancel out, and the net moment is due to the divalent cations. If the individual divalent cation moments are known, then it is possible to calculate the net moment per formula unit (see Cooperative Learning Exercise 6.7). In a formula unit of magnetite, there is one divalent iron ion that has a total moment of 4/tb resulting from four unpaired electrons, which is very close to the observed value. Similarly, in NiFc204, the moment per formula unit is 2/j.b identical to that of the divalent nickel ion. 

Yushkin (1971) proposes for proper interpretation of hardness anisotropy the construction of hardness indicatrices or comparison of hardness formulae, in which the numbers give the hardness in a particular crystallographic direction. For the example of Ural magnetite crystal, such a hardness formula is written as follows ... 

Structural Formula Poly[N-(2-aminotethyl)-3-aminopropyl]siloxane-coated non-stoichiometric magnetite... 

Magnetite (FC3O4) is a component of the water-gas shift reaction that crystallizes to the inverse spinel structure. The general formula of the oxides known as spinel is AB204. In the normal spinel-type structure, A is an A2+ metal, and B is a B3+ metal. O2- forms a CCP anionic framework, where the A atoms occupy 1/8 of the tetrahedral sites and the B atoms occupy 1/2 of the octahedral sites (see Figures 1.6 and 1.7). An example of a normal spinel is Mg A1204. 

Magnetic iron oxide, Fe304, occurs naturally as the mineral magnetite. It has an inverse spinel structure (see Chapter 9) because it contains Fe2+ and Fe3+, and the formula can be written as FeO Fe203. 

Chromitite occurs as dull, magnetic crystals, resembling magnetite, and has a mean composition represented by the formula Fe203.Cr203.5... 

The most notable development for the magnetite system was the introduction of cobalt as an additional component by ICI in 1984 [395], [396]. The cobalt-enhanced catalyst formula was first used in an ammonia plant in Canada using ICI Catalco s AMV process (later also in other AMV license plants) and is also successfully applied in ICl s LCA plants in Severnside. 

Examine specimens of hematite, limonite, and magnetite. Describe each. Draw the first two across a sheet of rough paper or a piece of ground glass, and describe the streak made by each. What is the formula of each (pure) compound Significance of each name ... 

Give the chemical name and formula of red hematite, iron pyrites, magnetite, loadstone, copperas, green vitriol, iron liquor. 

Magnetite, ideal formula Fe304, is an intriguing mineral, and not only because it is magnetic. The formula could be written Fe "Fe 04, which more precisely designates one of its peculiarities. It contains both ferrous (Fe ) and ferric (Fe ) ions implying synthesis, growth, and stability... 

The solid solution (ss) on the left has been represented as a mixture consisting of 1 — X moles of magnetite and x moles of zinc ferrite per formula unit of ss. It is assumed that the zinc ferrite moiety remains passive while any changes relating to the oxygen/cation composition occur exclusively in the magnetite component. 

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