The iron (II) oxide, or ferrous oxide, is a black inorganic solid that is formed by the reaction of oxygen (Otwo) with iron (Fe) up to the oxidation state +2. It is also called iron monoxide. Its chemical formula is FeO.
It is found in nature as the mineral wustite, a member of the periclase group. It is also known as wuestite, iosiderite or iozite. Wustite is an opaque mineral, black to brown in color, although under reflected light it is gray. Has metallic luster.
Iron (II) oxide can be obtained by thermal vacuum decomposition of iron (II) oxalate, obtaining a pyrophoric black powder. This powder decreases its state of division and becomes less reactive when heated to high temperatures..
Iron (II) oxide crystals can only be obtained under high temperature equilibrium conditions, rapidly cooling the system. If the reaction is carried out at lower temperatures, FeO is unstable and becomes iron (Fe) and Fe oxide3OR4, since slow cooling favors disproportion.
Because it is pyrophoric, it is a material that presents a fire risk. In addition, it is dangerous if inhaled in large quantities and for a long time, as it can cause lung disease.
Iron (II) oxide is used as a pigment in ceramics, enamels, glasses and cosmetics. Because of its magnetic properties it is used in medicine. It is also used as an antioxidant in packaged foods and, additionally, it is used in catalysis of reactions and in pesticide formulas.
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Iron (II) oxide (FeO) theoretically possesses the cubic structure of rock salt, having 4 Fe ionstwo+ and 4 O ionstwo- for each unit cell, and Fe ionstwo+ occupying the octahedral sites.
However, the reality is that it deviates significantly from the ideal rock salt structure of FeO, as it is a complex faulty arrangement..
Some Fe ionstwo+ are replaced by Fe ions3+, so the crystalline structure always presents some iron deficiency. For this reason it is said to be a non-stoichiometric solid. The formula that best describes it is Fe1-xOR.
On the other hand, hydrated iron (II) oxide (FeO.nHtwoO) is a green crystalline solid.
It has several denominations:
- Iron (II) oxide.
- Ferrous oxide.
- Iron monoxide.
- Wustite.
- Wuestite.
- Iosiderite.
- Iozita.
Crystalline solid.
5-5.5.
71.84 g / mol.
1368 ºC.
5.7 g / cm3
Practically insoluble in water and alkalis. Quickly soluble in acids. Insoluble in alcohol.
2.23.
- It rusts easily in air. Under certain conditions it ignites spontaneously in air. That is why it is said to be pyrophoric.
- It is a strong base and absorbs carbon dioxide quickly.
- The natural mineral wustite is highly magnetic. However, below -75 ºC FeO is antiferromagnetic.
- Wustite behaves like a semiconductor.
- The magnetic and electrical conductivity properties, as well as its structure depend on its thermal history and the pressures to which it has been subjected..
- Inhalation of iron (II) oxide dust or fumes is considered dangerous, as it can cause irritation of the nose and throat and can affect the lungs..
- High levels of exposure to FeO dust can lead to a condition called metal fume fever, an occupational exposure disease that causes flu-like symptoms..
- Continued exposure to high levels of FeO can have more serious effects, including a disease known as siderosis. This is an inflammation of the lungs that is accompanied by symptoms similar to pneumonia.
FeO has long been used as a pigment in ceramic mixtures..
Due to its green color, hydrated ferrous oxide (FeO.nHtwoO) excels in manufacturing green glass with heat absorbing characteristics. This type of glass is used in buildings, cars, wine bottles and other applications..
FeO is used as a raw material in the manufacture of steel. It is important to underline that in this application the FeO activity must be controlled, since if it is in excess it can negatively affect the process, especially it can increase the oxidation of aluminum. To avoid this, aluminum or calcium carbide is often added to the slag phase..
It is used as a catalyst in a large number of industrial and chemical operations. In catalyst preparations, those used in the synthesis of NH stand out.3 and metanation.
It is used in formulas for home control of insects.
Used in cleansers, regenerators, and personal care creams.
As a coloring agent or pigment in cosmetics, it is used to cover imperfections on the surface of the skin. Because it is insoluble in water, when used it remains in the form of crystals or particles and allows greater coating.
Being a mineral pigment, it is more resistant to light than organic dyes. Mineral pigments are more opaque but less shiny. Hydrated iron (II) oxide offers excellent stability and is among the most used mineral pigments in makeup..
Magnetic FeO nanoparticles are widely used in this field. For example, pharmaceutical drug targeting and techniques such as cell sorting take advantage of the attraction of magnetic particles to high magnetic flux densities. This applies to cancer treatment.
FeO acts as an antioxidant in food packaging. It is added as a fine powder in a bag or label attached to the packaging, separated from the product. In this way it is released at a controlled rate.
Due to its property of reacting easily with oxygen, it acts as an O uptake agent.two, reducing the concentration of this inside the packaging where the edible is located.
Thus the oxidative degradation of the food is delayed, increasing its duration. It is used especially in the preservation of meats.
The cosmetic industry uses FeO to create pigments in enamels.
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