III oxides

CHEMICAL NAME = iron(lll) oxide CAS NUMBER = 1317-60-8 MOLECULAR FORMULA = Fe205 MOLAR MASS = 159.7 g/mol COMPOSITION = Fe(69.9°/o) 0(30.1%) 

MELTING POINT = 1,565°C BOILING POINT = not reported DENSITY = 5.24 g/cm3 

Iron (III) oxide exists in mineral form as hematite. It is 70% iron and is the primary source of iron ore in the world. About 90% of the iron mined in the United States is hematite. World production of this ore is more than 1 billion tons. Magnetite and taconite are two other primary iron oxide minerals used as iron ore. The name hematite comes from the blood-red color of powdered hematite. The Greek word hematite means blood-like. Some ancients held the belief that hematite was formed in areas where batdes were fought and blood was spilled into the earth. Large deposits of hematite have been identified on Mars. 

In iron production, iron ores are reduced to produce iron metal. The opposite process occurs when iron metals are oxidized to produce iron oxides or rust. Rust is primarily iron(III) oxide. Iron does not combine directly with oxygen to produce rust but involves the oxidation of iron in an electrochemical process. There are two requirements for rust oxygen and water. The necessity of both oxygen and water is illustrated when observing automobiles operated in dry climates and ships or other iron objects recovered from anoxic water. Autos and ships subjected to these conditions show remarkably little rust, the former because of lack of water and the latter because of lack of oxygen. 

As noted, water serves as an electrolyte through which iron ions migrate. This explains why vehicles rust much more rapidly in regions where road salts are used to melt winter ice. The salts improve the conductivity of the electrolyte, thereby accelerating the corrosive process. 

Hematitite forms naturally when iron-containing rocks and minerals react with oxygen in the air to form iron(III) oxide. The oxide can he made synthetically by a variety of 

Iron(lll) oxide. Red atoms are oxygen and orange atoms are iron, publishers 

In the eighteenth century, the blast furnace process was further developed so that iron could be made commercially. This process can be traced to the region around 

The name hematite is derived from the Greek word for blood. 

When hematite is made into an ornament, it is sometimes called black diamond. 

The equilibrium solubilities of the oxalates in water are very small. However, they tend to form supersaturated solutions. This tendency is most pronounced for the magnesium salt, and therefore magnesium iron(III) oxide is the most difficult to prepare. If the precipitations are carried out in acetic acid solution, they can be made nearly quantitative. Metal acetates are the best starting materials because they yield acetic acid as a by-product. Iron(II) acetate is obtained by dissolving pure iron in acetic acid. The solution must be kept out of contact with the air to prevent the formation of iron(III), which gives a soluble oxalate. 

The precipitation of the mixed oxalates is carried out conveniently in a 1-1. Pyrex three-necked Wolff bottle, with standard-taper connections. One neck is fitted with a reflux condenser, another with a gas inlet tube, and the third with a separatory funnel. A Teflon-covered magnetic stirring bar rests in the bottle, which is set on an electric hot plate equipped with a magnetic stirring device. The iron powder (0.0800 mol, assayed for iron content) and magnesium acetate (0.0400 mol) are weighed into the bottle. 

These spinels are easily obtained with ideal formula MFe204. The appropriate acetates and iron (same number of mols as in Part A) are dissolved in 400 ml. of acetic acid solution (1 3 by volume) and the precipitation carried out 

Zinc iron(III) oxide should not be ignited for more than 1 or 2 hours above approximately 1100°. At very high temperatures there is a tendency for a small amount of iron(II) to form through loss of oxygen. The iron(II) reduces a small amount of zinc to the metallic condition. Although this reaction is probably unfavorable energetically, equilibrium is continuously disturbed by the evaporation of zinc, and the stoichiometry can be changed appreciably.  

Formula starting materials, mol Ignition temperature Weight Fe, %  

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Boron III) oxide, B2O3, is obtained by ignition of boric acid. Combines with water to reform B(0H)3. The fused oxide dissolves metal oxides to give borates. 

Aluminium is obtained on a large scale by the electrolysis of the oxide, dissolved in fused cryolite The oxide, occurring naturally as bauxite, AI2O3.2H2O, usually contains silica and iron(III) oxide as impurities. These must be removed first, since aluminium, once prepared, cannot be freed of other metals (which will be deposited on electrolysis) by refining it. The crude oxide is dissolved under pressure in caustic soda solution the aluminium oxide and silica dissolve and the ironflll) oxide is left ... 

None of the common allotropic forms of these metals is affected by air unless they are heated, when aU burn to the (III) oxide. 

Arsenic dissolves in concentrated nitric acid forming arsenicfV) acid, H3ASO4, but in dilute nitric acid and concentrated sulphuric acid the main product is the arsenic(III) acid, HjAsOj. The more metallic element, antimony, dissolves to form the (III) oxide Sb O, with moderately concentrated nitric acid, but the (V) oxide Sb205 (structure unknown) with the more concentrated acid. Bismuth, however, forms the salt bismulh(lll) nitrate Bi(N03)3. 5H,0. 

Phosphorus(lll) oxide is prepared by passing a slow (i.e. limited) stream of air over burning white phosphorus. A mixture of the two oxides P40(, and P40,o is thereby formed the (V) oxide can be condensed out of the emerging gas stream as a solid by passing through a U tube heated in a water bath to about 330 K the more volatile (III) oxide passes on and can be condensed in a second U trap surrounded by ice. 

Phosphorus(III) oxide dissolves in several organic solvents, for example benzene, carbon disulphide the molecular weight in these solvents corresponds to the formula P40(, as does the density of the vapour, and the structure is ... 

Phosphorus(III) oxide reacts slowly with oxygen at ordinary temperatures to give the pentoxide, P40,g. The reaction is rapid if the oxide is heated in air. It is oxidised vigorously by chlorine and bromine which form the oxidehalides, POX3. 

Phosphorus(III) oxide dissolves slowly in cold water to yield phosphoric(III) acid, H3PO3 (phosphorous acid) ... 

This is formed when arsenic burns in air (cf. phosphorus which gives P4O10). It can exist in two crystalline modifications the stable one at room temperature, which also occurs naturally as arsenolite, has an octahedral form. Solid arsenic(III) oxide is easily reduced, for example by heating with charcoal, when arsenic deposits as a black shiny solid on the cooler parts of the tube. 

Arsenic(III) oxide is slightly soluble in water, giving a solution with a sweetish taste—but as little as 0.1 g can be a fatal dose (The antidote is freshly-precipitated iron(III) hydroxide.) The solution has an acid reaction to litmus, due to the formation of arsenic(III) acid ... 

Unlike phosphorus pentoxide, this oxide cannot be made directly. Arsenic(V) acid, H3ASO4 (strictly, tetraoxoarsenic acid), is first prepared by oxidising arsenic(III) oxide with concentrated nitric acid or some other strong oxidising agent ... 

Arsenic(V) oxide is a white deliquescent solid, which liberates oxygen only on very strong heating, leaving the (III) oxide ... 

Arsenic(III) (arsenious) acid, H3ASO3.—When arsenic(III) oxide is dissolved in water the corresponding acid is formed ... 

Since arsenic is often found in nature associated with sulphide ores, sulphur dioxide obtained by this method may contain some arsenic(III) oxide as impurity, and in certain processes this is a distinct disadvantage. 

The iodine is then liberated by heating the copper(I) iodide with sulphuric acid and iron(III) oxide ... 

By the reaction of chlorine with a heated mixture of chrom ium(III) oxide and carbon ... 

Alkali metal ferrates(VI), for example K2pe04, are obtained by oxidation of a suspension of hydrous iron(III) oxide (assumed to be Fe(OH)3 in the equation below) by chlorate(I) in concentrated alkali ... 

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 ... 

The mixed oxide Fc304 (tri-iron tetroxide) is a black solid, which occurs naturally as magnetite it is formed when iron(III) oxide is strongly heated, and its structure is effectively made up of oxide (O ) and iron(II) and iron(III) ions. 

This is the most important reaction of iron from an economic point of view essentially, rusting is the formation of hydrated iron(III) oxide in the presence of oxygen and water. The process is essentialh... 

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