Hydrated magnetite

Chry sotile is a hydrated magnesium siHcate and its stoicliiometric chemical composition may be given as AIg2Si20 (0H)4 [12001 -29-5]. However, the geothermal processes wliich ield the chry sotile fiber formations usually involve the co-deposition of v arious other minerals. Tliese mineral contaminants comprise brucite [1317-43-7] (AIg(OH)2), magnetite [1309-38-2] (Fe O, calcite [13397-26-7] (CaCO ), dolomite [16389-88-1] (AIg,CaC02),... 

Ferric and ferrous hydroxide usually contain water of hydration. A layer of hydrated magnetite sometimes forms between the ferric and ferrous hydroxides (see Fig. 3.2). The threefold layer of corrosion products is usually called rust. The bulk of rust is the ferric hydroxide layer. (In tubercles, however, ferrous hydroxide often is the major component see Chap. 3.)... 

The product, ferrous hydroxide, is commonly further oxidised to magnetite (Fej04) or a hydrated ferric oxide (FeOOH), i.e. rust. 

In rusting, the initial corrosion product of iron is ferrous hydroxide. Reacting with oxygen and water, it forms higher oxides, mainly hydrated ferric oxide and magnetite. Rust formed in industrial or marine environments contains corrosion-promoting salts and is particularly dangerous. Rust is not considered a satisfactory base over which to paint and it too must be removed. 

For steel, passivation is achieved by the surface formation of a tough, adherent mixture of oxides. The passive film is primarily gamma-magnetite (y-Fe203) but also contains gamma-hydrated ferric oxide (y-FeOOH). The film thickness is perhaps 15 A to 30 A (angstrom units). 

The release of adriamycin from BSA microspheres both with and without magnetic particles present as magnetite was investigated (137). While the presence of drug and/or magnetite had no effect on the size of the hydrated or unhydrated microspheres, the stabilization temperature affected the size of hydrated microspheres. 

Li, Z Sun, Q. and Gao, M.Y. (2005) Preparation of water-soluble magnetite nanocrystals from hydrated ferric salts in 2-pyrrolidone mechanism leading to Fe304. Angewandte Chemie International Edition, 44 (1), 123-126. 

Insol in w, ale. or eth sol In acids occurs in nature as mineral magnetite. Can be prepd in pure state by dehydrating pptd hydrated ferric oxide, followed by reduction with hydrogen. 

Fe- Oxides Magnetite Goethite Lepidocrocite MAmorphous"hydrates 4 ... 

Finely divided magnetite deposited on a support is liable to oxidation and hydrolysis, which leads to hydrated supported iron(III) oxide. To prevent oxidation and hydration, the loaded support has to be dried in an inert gas. After being dried the supported magnetite is fairly stable on exposure to atmospheric air, although reaction to y-Fe203 may proceed. 

Fig. 1. If equilibrium is maintained on cooling, CO will be converted largely to CH4 (solid lines) before metastable formation of more complex hydrocarbons by the Fischer-Tropsch reaction becomes possible (dashed lines). However, the reaction is very slow in the absence of catalysts, and may not have begun until about 400 K, when catalysts such as serpentine and magnetite became available through the hydration of olivine. Thus CO may have persisted metastably between 600 and 400 K...

An answer to the first question was suggested by Lancet and Anders (1970). The principal meteoritic phases stable above 350-400 K (olivine, pyroxene, Fe, FeS) are not effective catalysts for the Fischer-Tropsch reaction, whereas the phases forming below this temperature (hydrated silicates, magnetite) are. P hough metallic iron is often regarded as a catalyst for this synthesis, the catalytically active phase actually is a thin coating of FCjO formed on the surface of the metal (Anderson, 1956)]. Thus CO may have survived metastably until catalysts became available by reactions such as ... 

The Ores of Iron. The chief ores of iron are its oxides hematite. Fe- Og, and magnetite, Fe O, and its carbonate side rite, FeCO.,. The hydrated ferric oxides such as limonite are also important. The sulfide pyrite, FeSo, is used as a source of sulfur dioxide, but the impure iron oxide left from its roasting is not satisfactory for smelting iron, because the remaining sulfur is a troublesome impurity. 

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