Iron dioxide

Iron dioxide is not known in the free state, but it can exist in combination, as witness such ferrites as barium ferrite, BaFc03. The dioxides of ruthenium, RuOa, and osmium, 0s02, arc known. The former is isomorphous with cassiterite, Sn02, and rutile, TiOa and combines with bases to form ruthenites, for example, barium ruthenite, BaRuOg. 

The mixture of various catalytic multimers, like thioesters and phosphorylated organic molecules, presents the background for a protometabolism in the thioester world theory. Protometabolitic reaction pathways rapidly form networks. The latter would have included cyclic mass flows that are stabilized by interactions among metabolites. These pathways could have occurred in associations with pyrite, clays or iron dioxide flocks produced by UV photooxidation. 

CuFe02 COPPER IRON DIOXIDE 623 EuF3[g] EUROPIUM FLUORIDE (GAS) 667... 

LiFe02 LITHIUM IRON DIOXIDE 979 MgS MAGNESIUM SULFIDE 1026... 

The behavior of plutonium in surface waters is dependent upon the oxidation state and the nature of the suspended solids and sediments. Plutonium(lll) and plutonium(IV) are considered to be the reduced forms of plutoniwm while plutonium(V) and plutonium(VI) are the oxidized forms. The oxidized forms of plutonium are found in natural waters when the concentrations of dissolved organic matter or dissolved solids are low (Nelson et al. 1987). Humic materials (naturally occurring organic acids) were found to reduce plutonium(V) to plutonium(IV) in sea water. This was followed by adsorption of plutonium(IV) onto iron dioxides and deposition into the sediments (Choppin and Morse 1987). 

Example EO NaFe02 sodium iron dioxide, or sodium iron(III) oxide... 

If the white precipitate does not appear, titrate this solntion with 40% stannons ehloride in hydrochloric acid, using a 2 ml pipette nntil the yellow eolor disappears. (If it changes after one or two drops, then it can be assumed there is no iron dioxide). 

Carbon dioxide (CO2) is a very common contaminant in hydrocarbon fluids, especially in gases and gas condensate, and is a source of corrosion problems. CO2 in the gas phase dissolves in any water present to form carbonic acid (H2CO3) which is highly corrosive. Its reaction with iron creates iron carbonate (FeCOg) ... 

A substantial fraction of the named enzymes are oxido-reductases, responsible for shuttling electrons along metabolic pathways that reduce carbon dioxide to sugar (in the case of plants), or reduce oxygen to water (in the case of mammals). The oxido-reductases that drive these processes involve a small set of redox active cofactors , that is, small chemical groups that gain or lose electrons. These cofactors include iron porjDhyrins, iron-sulfur clusters and copper complexes as well as organic species that are ET active. 

In strongly acid solution, substances which are normally reducing agents reduce sulphur dioxide solution or sulphites, for example iron(II) and zinc ... 

Concentrated sulphuric acid is an oxidising agent, particularly when hot, but the oxidising power of sulphuric acid decreases rapidly with dilution. The hot concentrated acid will oxidise non-metals, for example carbon, sulphur and phosphorous to give, respectively, carbon dioxide, sulphur dioxide and phosphoric(V) acid. It also oxidises many metals to give their sulphates cast iron, however, is not affected. The mechanisms of these reactions are complex and the acid gives a number of reduction products. 

Titanium is not a rare element it is the most abundant transition metal after iron, and is widely distributed in the earth s surface, mainly as the dioxide TiOj and ilmenite FeTi03. It has become of commercial importance since World War II mainly because of its high strength-weight ratio (use in aircraft, especially supersonic), its... 

The extraction of titanium is still relatively costly first the dioxide Ti02 is converted to the tetrachloride TiCl4 by heating with carbon in a stream of chlorine the tetrachloride is a volatile liquid which can be rendered pure by fractional distillation. The next stage is costly the reduction of the tetrachloride to the metal, with magnesium. must be carried out in a molybdenum-coated iron crucible in an atmospheric of argon at about 1100 K ... 

The dichromate ion oxidises iron(II) to iron(III), sulphite to sulphate ion, iodide ion to iodine and arsenic(III) to arsenic(V) (arsenate). Reduction of dichromate by sulphite can be used to prepare chrome alum, since, if sulphur dioxide is passed into potassium dichromate acidified with sulphuric acid, potassium and chromium(III) ions formed are in the correct ratio to form the alum, which appears on crystallisation ... 

In combination, carbon is found as carbon dioxide in the atmosphere of the earth and dissolved in all natural waters. It is a component of great rock masses in the form of carbonates of calcium (limestone), magnesium, and iron. Coal, petroleum, and natural gas are chiefly hydrocarbons. 

Its conductivity increases slightly with exposure to light. It can be doped with silver, copper, gold, tin, or other elements. In air, tellurium burns with a greenish-blue flames, forming the dioxide. Molten tellurium corrodes iron, copper, and stainless steel. 

Laughing gas, see Nitrogen(I) oxide Lautarite, see Calcium iodate Lawrencite, see Iron(II) chloride Lechatelierite, see Silicon dioxide Lime, see Calcium oxide Litharge, see Lead(II) oxide... 

Sellaite, see Magnesium fluoride Senarmontite, see Antimony(III) oxide Siderite, see Iron(II) carbonate Siderotil, see Iron(II) sulfate 5-water Silica, see Silicon dioxide Silicotungstic acid, see Silicon oxide—tungsten oxide—water (1/12/26)... 

Thenardite, see Sodium sulfate Thionyl, see Sulflnyl Thorianite, see Thorium dioxide Topaz, see Aluminum hexafluorosilicate Tridymite, see Silicon dioxide Troilite, see Iron(II) sulflde... 

Manganese(II) can be titrated directly to Mn(III) using hexacyanoferrate(III) as the oxidant. Alternatively, Mn(III), prepared by oxidation of the Mn(II)-EDTA complex with lead dioxide, can be determined by titration with standard iron(II) sulfate. 

If poUed, most aquaculturists would probably indicate a preference for well water. Both freshwater and saline wells are common sources of water for aquaculture. The most commonly used pretreatments of well water include temperature alteration (either heating or cooling) aeration to add oxygen or to remove or oxidize such substances as carbon dioxide, hydrogen sulfide, and iron and increasing salinity (in mariculture systems). Pretreatment may also include adjusting pH, hardness, and alkalinity through the appHcation of appropriate chemicals. 

Elastomeric shield materials (ESM) have been developed as low density flexible ablators for low shear appHcations (49). General Electric s RTV 560 is a foamed silicone elastomer loaded with silicon dioxide [7631-86-9] and iron oxide [1317-61 -9] particles, which decomposes to a similar foam of Si02, SiC, and EeSiO. Silicone resins are relatively resistant to thermal decomposition and the silicon dioxide forms a viscous Hquid when molten (50) (see... 

Aniline Oxidation. Even though this is quite an old process, it still has limited use to produce hydroquinone on a commercial scale. In the first step, aniline is oxidized by manganese dioxide in aqueous sulfuric acid. The resulting benzoquinone, isolated by vapor stripping, is reduced in a second step by either an aqueous acidic suspension of iron metal or by catalytic hydrogenation. 

The yield of hydroquinone is 85 to 90% based on aniline. The process is mainly a batch process where significant amounts of soHds must be handled (manganese dioxide as well as metal iron finely divided). However, the principal drawback of this process resides in the massive coproduction of mineral products such as manganese sulfate, ammonium sulfate, or iron oxides which are environmentally not friendly. Even though purified manganese sulfate is used in the agricultural field, few solutions have been developed to dispose of this unsuitable coproduct. Such methods include MnSO reoxidation to MnO (1), or MnSO electrochemical reduction to metal manganese (2). None of these methods has found appHcations on an industrial scale. In addition, since 1980, few innovative studies have been pubUshed on this process (3). 

Minerals. Iron-bearing minerals are numerous and are present in most soils and rocks. However only a few minerals are important sources of iron and thus called ores. Table 2 shows the principle iron-bearing minerals. Hematite is the most plentiful iron mineral mined, followed by magnetite, goethite, siderite, ilmenite, and pyrite. Siderite is unimportant in the United States, but is an important source of iron in Europe. Tlmenite is normally mined for titania with iron as a by-product. Pyrite is roasted to recover sulfur in the form of sulfur dioxide, leaving iron oxide as a by-product. 

Carbonates. Iron(II) carbonate [563-71-3] FeCO, precipitates as a white soHd when air-free solutions of alkah metal carbonates and iron(II) salts are mixed. The limited tendency of [Fe(H20)g] to hydroly2e is illustrated by the lack of carbon dioxide evolution in this reaction. The soHd rapidly... 

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