What Is Chromium?
Chromium is a metallic element with atomic number 24 and element symbol Cr.
It was named by René Just Haüy after the Greek word chroma, meaning color, because compounds of chromium have a variety of colors.
Chromium is mainly extracted from chromite ore (FeCr2O4). More than 90% of the world’s chromium resources are concentrated in two countries, South Africa and Kazakhstan, and are highly unevenly distributed.
Uses of Chromium
Chromium is used primarily in the steel industry. Alloys of chromium and iron containing more than 12% chromium are called stainless steels and are widely used in machinery and kitchenware as a rust-resistant metal with high corrosion resistance. In addition, chromium metal is available as a plating because of its luster and high corrosion resistance.
Chromium is also an essential mineral involved in human metabolism. In particular, its ability to stimulate lipid metabolism helps lower cholesterol levels and neutral fats and can prevent arteriosclerosis and hypertension. It also helps insulin work and is said to be effective in preventing diabetes.
Properties of Chromium
Chromium is a hard, silvery-white metal with a melting point of 1,907°C and a boiling point of 2,671°C. It is extremely stable at room temperature.
When dissolved in hydrochloric acid or dilute sulfuric acid, it forms a solution of divalent chromium salts, which are quickly oxidized to trivalent chromium by oxygen in the air due to its unstable divalent state.
Structure of Chromium
The electron configuration of chromium is [Ar] 3d5 4s1. The crystal structure is a body-centered cubic lattice for α, a cubic close-packed structure for β, and a hexagonal close-packed structure for γ.
Other Information on Chromium
1. Chromium in the Body
Chromium is a trace essential element for humans. It is a material used to make up glucose tolerance factors that help bind insulin and receptors in the body. When the body is deficient in chromium, abnormalities in glucose metabolism may occur and diabetes may develop.
Examples of foods rich in chromium include shrimp, liver, mushrooms, beans, brewer’s yeast, and black pepper. The daily requirement for chromium is 50 to 200 µg.
Unrefined grains contain it, but most chromium is lost during refining. It is reported that 98% of chromium is lost when flour is refined and 92% of chromium is lost when rice is refined. Furthermore, chromium is a mineral that is difficult to absorb into the body. Supplements are available to help the body absorb chromium.
2. Dangers of Chromium
Chromium alone and trivalent chromium are not toxic. However, hexavalent chromium compounds are highly toxic. In the past, hexavalent chromium was used for plating, but it is no longer used in chromate treatment of zinc plating due to soil contamination and other problems.
Chromium is a carcinogen found in cigarettes; tetravalent chromium compounds have been reported to be carcinogenic.
3. Isotopic Applications of Chromium
53Cr is a decay product of 53Mn, and isotopic contents of chromium and manganese are related and available in isotopic geology. Given the compositional ratios of chromium and manganese isotopes, the presence of 26Al and 107Pd in the early solar system is an indication that these isotopes were present in the early solar system. The diverse compositional ratios of 52Cr and 53Cr and Mn and Cr in the asteroid suggest that 53Mn decayed early in the formation of the object.