Chemical composition Iron oxide

The amount of soluble silica available to plants in soil moisture is greatly affected by the chemical composition. Free oxides or iron or alumina absorb and insolubilize the silica. Oats take up silica at a rate that depends directly on the amount of silica in solution in the soil and the total. silica increases with the amount of water transpired. In the oat plant, silica thus plays a passive role from a biochemical standpoint (137). ... 

The choice of selected raw materials is very wide, but they must provide calcium oxide (lime), iron oxide [1309-37-1/, siHca, and aluminum oxide (alumina). Examples of the calcereous (calcium oxide) sources are calcium carbonate minerals (aragonite [14791-73-2] calcite [13397-26-7] limestone [1317-65-3] or mad), seasheUs, or shale. Examples of argillaceous (siHca and alumina) sources are clays, fly ash, mad, shale, and sand. The iron oxide commonly comes from iron ore, clays, or mill scale. Some raw matedals supply more than one ingredient, and the mixture of raw matedals is a function of their chemical composition, as deterrnined by cost and availabiHty. 

In our case the chemical composition and, consequently, the structure of the iron oxide is changed with time during reaction. Gold diffusion from film and nanoparticles underneath may occur but seem not to be the decisive factor in promoting the CO oxidation activity. 

Besides this iron meteorite, there have been four other rocks identified to be probably of meteoritic origin. These centimeter-sized pebbles, named Barberton, Santa Catarina, Santorini and Kasos, show troilite and/or kamacite signatures in the corresponding Mossbauer spectra [359]. The range of Fe oxidation states suggests the presence of a fusion cmst. The four cobbles have a very similar chemical composition determined by the APXS, and therefore they may be fragments of the same impactor that created Victoria Crater [361]. 

The chemical composition of the soil and groundwater, specifically the amount of natural organic matter (NOM) and other reduced species, such as iron (II) or manganese (II) often analyzed as the chemical oxygen demand (COD) of the soil, or the soil oxidant demand. 

The composition of the particles is related to that of the source rocks. Quartz sand [composed of silica (silicon dioxide)], which makes up the most common variety of silica sand, is derived from quartz rocks. Pure quartz is usually almost free of impurities and therefore almost colorless (white). The coloration of some silica sand is due to chemical impurities within the structure of the quartz. The common buff, brown, or gray, for example, is caused by small amounts of metallic oxides iron oxide makes the sand buff or brown, whereas manganese dioxide makes it gray. Other minerals that often also occur as sand are calcite, feldspar and obsidian Calcite (composed of calcium carbonate), is generally derived from weathered limestone or broken shells or coral feldspar is an igneous rock of complex composition, and obsidian is a natural glass derived from the lava erupting from volcanoes see Chapter 2. 

Primary clay is also known as residual clay, indicating that they are either the in situ residue of one type of weathered rock or the transported residue of many types of rocks most primary clay deposits occur, however, in situ, at the location where the clay particles were formed. The clay is usually quite pure and colorless or white, but very small relative amounts of minerals mixed with the clay, such as quartz and/or iron oxides, may impart to it a yellow, brown, or green color. Primary clay is also characterized by the extreme fineness of its particles, which usually measure below 2 micrometers (0.002 mm) in diameter. The more than 20 different types of primary clay minerals can be distinguished by their chemical composition, which varies widely, and by their physical properties. Primary clays that have been used for making ceramic objects are listed in Table 55. 

The chemical composition of the Earth s interior determined the character (the oxidation state) of the primeval atmosphere. If metallic iron had collected in the Earth s core in the early phase of the accretion, the exhalations from the interior of the Earth would have consisted mainly of CO2 and H20, since the gas from the interior could only have come into contact with FeO and Fe203 silicates in the mantle. If, however, metallic iron had been distributed throughout the mantle, the iron and the FeO silicates would have had a reductive influence on the gases the gas exhaled into the atmosphere would then have consisted of CH4, H2 and NH3 (Whittet, 1997). 

The planets nearest the Sun have a high-temperature surface while those further away have a low temperature. The temperature depends on the closeness to the Sun, but it also depends on the chemical composition and zone structures of the individual planets and their sizes. In this respect Earth is a somewhat peculiar planet, we do not know whether it is unique or not in that its core has remained very hot, mainly due to gravitic compression and radioactive decay of some unstable isotopes, and loss of core heat has been restricted by a poorly conducting mainly oxide mantle. This heat still contributes very considerably to the overall temperature of the Earth s surface. The hot core, some of it solid, is composed of metals, mainly iron, while the mantle is largely of molten oxidic rocks until the thin surface of solid rocks of many different compositions, such as silicates, sulfides and carbonates, occurs. This is usually called the crust, below the oceans, and forms the continents of today. Water and the atmosphere are reached in further outward succession. We shall describe the relevant chemistry in more detail later here, we are concerned first with the temperature gradient from the interior to the surface (Figure 1.2). The Earth s surface, i.e. the crust, the sea and the atmosphere, is of... 

The chemical composition of particles can be just as varied as their shape. Commercial particles can consist of polymers or copolymers, inorganic constructs, metals and semiconductors, superparamagnetic composites, biodegradable constructs, and synthetic dendrimers and dendrons. Often, both the composition of a particle and its shape govern its suitability for a particular purpose. For instance, composite particles containing superparamagnetic iron oxide typically are used for small-scale affinity separations, especially for cell separations followed by flow cytometry analysis or fluorescence-activated cell sorting (FACS). Core-shell semiconductor particles, by... 

The Renison Bell tin mine is a large, but complex, oxide mineral deposit. Renison ore consists largely of pyrrhotite, quartz, dolomite, siderite and dorite. The chemical composition of the iron varies considerably. Some of the ore types are high in copper and silver. Table 21.5 shows the chemical analyses of various ore types. 

Discussion and Conclusion The chemical composition of iron oxides is useful to discriminate a range of mineral deposit types. Discriminant diagrams can be used to identify potential for specific mineral deposit types to occur in an area that has been glacially eroded using till. In this study, a small subset of the ferromagnetic fraction (50 grains, 0.5-1.0 mm size fraction) of a till has been shown to adequately display the compositional... 

Both rust and oxide scales are usually mixtures of iron oxides vith other Fe (e. g. siderite) and non-Fe compounds (CaCOs). In some cases there is a more or less random mixture of components, vhereas in others, the different oxides are arranged in layers to form duplex or triplex scales. Layer-type rust arises as a result of potential or chemical gradients across the film. As these gradients vary ivith film thickness, the composition of the rust changes with the distance from the metal. On the whole, if Fe " and Fe" are present, the oxide containing Fe" is found in the inner layer of the rust. 

In most industrial processes, copper is produced from the ore chalcopyrite, a mixed copper-iron sulfide mineral, or from the carbonate ores azurite and malachite. The extraction process depends on the chemical compositions of the ore. The ore is crushed and copper is separated by flotation. It then is roasted at high temperatures to remove volatile impurities. In air, chalcopyrite is oxidized to iron(ll) oxide and copper(ll) oxide ... 

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