Iron oxides salts

Diffusion of iron oxide salts into the porous latex particles... 

Under environmental conditions, the Fe -H20 interface has a surface layer of corrosion products that develops due to the thermodynamic instability of Fe in the presence of water. Long-term batch and colunm studies have shown that this layer evolves with time into a complex mixture of amorphous iron oxides, iron oxide salts, and other mineral precipitates (2-S). Because this material lies at the metal-water interface, it must, in some manner, mediate the reduction of contaminants by the underlying metal. Understanding the mechanism by which metals reduce contaminants in the presence of a substantial layer of oxides is one of the critical, remaining challenges for researchers in this field. The goal of the following analysis is... 

If an aqueous solution of an iron(lll) salt is treated with alkali, a red-brown precipitate of iron(III) hydroxide is obtained this is probably best represented as FeO(OH). On strong heating it gives the red oxide Fe203. Iron(III) oxide, Fc20, occurs naturally as haematite, and can also be prepared by strong heating of iron(II) sulphate ... 

Naphthol Antipyrine, camphor, phenol, iron(III) salts, menthol, oxidizing materials, permanganates, urethane... 

Hexa.cya.no Complexes. Ferrocyanide [13408-63 ] (hexakiscyanoferrate-(4—)), (Fe(CN) ) , is formed by reaction of iron(II) salts with excess aqueous cyanide. The reaction results in the release of 360 kJ/mol (86 kcal/mol) of heat. The thermodynamic stabiUty of the anion accounts for the success of the original method of synthesis, fusing nitrogenous animal residues (blood, horn, hides, etc) with iron and potassium carbonate. Chemical or electrolytic oxidation of the complex ion affords ferricyanide [13408-62-3] (hexakiscyanoferrate(3—)), [Fe(CN)g] , which has a formation constant that is larger by a factor of 10. However, hexakiscyanoferrate(3—) caimot be prepared by direct reaction of iron(III) and cyanide because significant amounts of iron(III) hydroxide also form. Hexacyanoferrate(4—) is quite inert and is nontoxic. In contrast, hexacyanoferrate(3—) is toxic because it is more labile and cyanide dissociates readily. Both complexes Hberate HCN upon addition of acids. 

Iron(II) hydroxide [18624-44-7], Fe(OH)2, is prepared by precipitation of an iron(II) salt solution by strong base in the absence of air. It occurs as pale green, hexagonal crystals or a white amorphous powder. It is practically insoluble in water, fairly soluble in ammonium salt solutions, and soluble in acids and in concentrated NaOH solution. It is slowly oxidized by air. Conversion to Fe203 atH20 is eventually complete. 

Iron(III) hydroxide [1309-33-7], FeH02, is a red-brown amorphous material that forms when a strong base is added to a solution of an iron(III) salt. It is also known as hydrated iron(III) oxide. The fully hydrated Fe(OH)3 has not been isolated. The density of the material varies between 3.4-3.9 g/cm, depending on its extent of hydration. It is insoluble in water and alcohol, but redissolves in acid. Iron(III) hydroxide loses water to form Fe203. Iron(III) hydroxide is used as an absorbent in chemical processes, as a pigment, and in abrasives. Salt-free iron(III) hydroxide can be obtained by hydrolysis of iron(III) alkoxides. 

The pale blue tris(2,2 -bipyridine)iron(3+) ion [18661-69-3] [Fe(bipy)2], can be obtained by oxidation of [Fe(bipy)2]. It cannot be prepared directiy from iron(III) salts. Addition of 2,2 -bipyridine to aqueous iron(III) chloride solutions precipitates the doubly hydroxy-bridged species [(bipy)2Fe(. t-OH)2Fe(bipy)2]Cl4 [74930-87-3]. [Fe(bipy)2] has an absorption maximum at 610 nm, an absorptivity of 330 (Mem), and a formation constant of 10. In mildly acidic to alkaline aqueous solutions the ion is reduced to the iron(II) complex. [Fe(bipy)2] is frequentiy used in studies of electron-transfer mechanisms. The triperchlorate salt [15388-50-8] is isolated most commonly. 

Aluminum. All primary aluminum as of 1995 is produced by molten salt electrolysis, which requires a feed of high purity alumina to the reduction cell. The Bayer process is a chemical purification of the bauxite ore by selective leaching of aluminum according to equation 35. Other oxide constituents of the ore, namely siUca, iron oxide, and titanium oxide remain in the residue, known as red mud. No solution purification is required and pure aluminum hydroxide is obtained by precipitation after reversing reaction 35 through a change in temperature or hydroxide concentration the precipitate is calcined to yield pure alumina. 

In atomization, a stream of molten metal is stmck with air or water jets. The particles formed are collected, sieved, and aimealed. This is the most common commercial method in use for all powders. Reduction of iron oxides or other compounds in soHd or gaseous media gives sponge iron or hydrogen-reduced mill scale. Decomposition of Hquid or gaseous metal carbonyls (qv) (iron or nickel) yields a fine powder (see Nickel and nickel alloys). Electrolytic deposition from molten salts or solutions either gives powder direcdy, or an adherent mass that has to be mechanically comminuted. 

Wet preparation of red iron oxides can involve either a hydrothermal process (see Hydrothermal processing) or a direct precipitation and growth of iron oxide particles on specially prepared nucleating seeds of Fe202- In the hydrothermal process, iron(II) salt is chemically oxidized to iron(III) salt, which is further treated by alkahes to precipitate a hydrated iron(III) oxide gel. The gel can be dehydrated to anhydrous hematite under pressure at a temperature around 150°C. 

Iron oxide yellows can also be produced by the direct hydrolysis of various ferric solutions with alkahes such as NaOH, Ca(OH)2, and NH. To make this process economical, ferric solutions are prepared by the oxidation of ferrous salts, eg, ferrous chloride and sulfate, that are available as waste from metallurgical operations. The produced precipitate is washed, separated by sedimentation, and dried at about 120°C. Pigments prepared by this method have lower coverage, and because of their high surface area have a high oil absorption. 

Transparent red iron oxide is composed mainly of hematite, a-Ee202, having primary particles about 10 nm. It is prepared by a precipitation reaction from a dilute solution of an iron salt at a temperature around 30°C, foUowed by a complete oxidation in the presence of some seeding additives,... 

Iron Reduction. The reduction of nitrophenols with iron filings or turnings takes place in weakly acidic solution or suspension (30). The aminophenol formed is converted to the water soluble sodium aminopheno1 ate by adding sodium hydroxide before the iron-iron oxide sludge is separated from the reaction mixture (31). Adjustment of the solution pH leads to the precipitation of aminophenols, a procedure performed in the absence of air because the salts are very susceptible to oxidation in aqueous solution. 

Under atmospheric conditions, 3-aminophenol is the most stable of the three isomers. Both 2- and 4-aminophenol are unstable they darken on exposure to air and light and should be stored in brown glass containers, preferably in an atmosphere of nitrogen. The use of activated iron oxide in a separate cellophane bag inside the storage container (116), or the addition of staimous chloride (117), or sodium bisulfite (118) inhibits the discoloration of aminophenols. The salts, especially the hydrochlorides, are more resistant to oxidation and should be used where possible. 

In addition to the requirement to conform to steam purity needs, there are concerns that the boiler water not corrode the boiler tubes nor produce deposits, known as scale, on these tubes. Three important components of boiler tube scale are iron oxides, copper oxides, and calcium salts, particularly calcium carbonate [471-34-1]. Calcium carbonate in the feedwater tends to produce a hard, tenacious deposit. Sodium phosphate is often added to the water of recirculating boilers to change the precipitate from calcium carbonate to calcium phosphate (see also Water, industrial water treatment). 

Two or more soHd catalyst components can be mixed to produce a composite that functions as a supported catalyst. The ingredients may be mixed as wet or dry powders and pressed into tablets, roUed into spheres, or pelletized, and then activated. The promoted potassium ferrite catalysts used to dehydrogenate ethylbenzene in the manufacture of styrene or to dehydrogenate butanes in the manufacture of butenes are examples of catalysts manufactured by pelletization and calcination of physically mixed soHd components. In this case a potassium salt, iron oxide, and other ingredients are mixed, extmded, and calcined to produce the iron oxide-supported potassium ferrite catalyst. 

In spirooxaziridines like (114), /3-scission proceeds with ring opening. Stoichiometric amounts of iron(II) salt in acidic solution lead to the dicarboxylic acid derivative (115). The radical undergoes some interesting reactions with added unsaturated compounds. For example, pyridine yields a mixture of 2- and 4-alkylation products in 80% yield. Catalytic amounts of iron(II) ion are sufficient here since the adduct of the radical with pyridine is oxidized by iron(III) ion to the final product (116), thus regenerating iron(II) ion (68TL5609). 

FIG. 23-43 Reactors for solids, (a) Temperature profiles in a rotary cement lain, (h) A multiple hearth reactor, (c) Vertical lain for lime burning, 55 ton/d. (d) Five-stage fluidized bed lime burner, 4 by 14 m, 100 ton/d. (e) A fluidized bed for roasting iron sulfides. (/) Conditions in a vertical moving bed (blast furnace) for reduction of iron oxides, (g) A mechanical salt cake furnace. To convert ton/d to kg/h, multiply by 907. 

Deposits contained organic acids formed by oxidation of rolling oils. Up to 40% by weight of the lumps shown in Fig. 4.27A and B was iron oxides, hydroxides, and organic-acid iron salts. Acidic species concentrated in the deposits. 

The lifetime of a conventional exhaust system on an average family car is only 2 years or so. This is hardly surprising - mild steel is the usual material and, as we have shown, it is not noted for its corrosion resistance. The interior of the system is not painted and begins to corrode immediately in the damp exhaust gases from the engine. The single coat of cheap cosmetic paint soon falls off the outside and rusting starts there, too, aided by the chloride ions from road salt, which help break down the iron oxide film. 

Eisenozyd, n. iron oxide, specif, ferric oxide, iron(Ul) oxide. — salpetersaures —, ferric nitrate, iron(III) nitrate (and so for other salts). 

Eisenoxydul-hydrat, n. ferrous hydroxide, iron(ll) hydroxide, -oxyd, n. ferrosoferric oxide, iron(II,III) oxide, magnetic iron oxide (FeaOi). -salz, n. ferrous salt, iron(II) salt, -sulfat, n. ferrous sulfate, iron(II) sulfate, -verbindung, /. ferrous compound, iron(ll) compound. 

The Fe2+ ion ( x = -0.769 V) is much more stable toward oxidation than Cr2+. However, iron(II) salts in water solution are slowly converted to iron(III) by dissolved oxygen. In acidic solution, the reaction is... 

One of the best oxidation-reduction indicators is the 1,10-phenanthroline-iron(II) complex. The base 1,10-phenanthroline combines readily in solution with iron(II) salts in the molecular ratio 3 base l iron(II) ion forming the intensely red l,10-phenanthroline-iron(II) complex ion with strong oxidising agents the iron(III) complex ion is formed, which has a pale blue colour. The colour change is a very striking one ... 

Oxidising agents, such as chromates, dichromates, copper(II) and iron(III) salts, higher oxides, and peroxides... 

Dithiol is a less selective reagent than thiocyanate for molybdenum. Tungsten interferes most seriously but does not do so in the presence of tartaric acid or citric acid (see Section 17.34). Tin does not interfere if the absorbance is read at 680 nm. Strong oxidants oxidise the reagent iron(III) salts should be reduced with potassium iodide solution and the liberated iodine removed with thiosulphate. 

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