General information

Holmium is a chemical element with the element symbol Ho and the atomic number 67. In the periodic table it is in the group of lanthanides and thus also belongs to the metals of the rare earths.

In 1878 the Swiss chemists Marc Delafontaine and Jacques-Louis Soret discovered the element spectroscopically through its deviating absorption lines. They called the new element 'X'. In 1879, the Swedish chemist Per Teodor Cleve discovered the new element independently of the two Swiss and isolated it as a yellow oxide from impure erbium (erbium oxide). Cleve used a method developed by Carl Gustav Mosander; it first separated off any known impurities before attempting to separate the rest. He received a brown residue, which he named Holmia, and a green residue, which was named Thulia. It was not until 1911 that the Swedish chemist Holmberg succeeded in obtaining pure holmium oxide. It is not known whether he adopted the name Holmium, suggested by Cleve for the Swedish capital Stockholm, or regarded it as a derivative of his own name.

Metallic pure holmium was first produced in 1940. Of course, holmium only occurs in compounds. Well-known holmium-containing minerals are:

Gadolinite (occurrence at Ytterby is exhausted)
Monazite (Ce, La, Th, Nd, Y) PO4

Recovery

After a complex separation of the other holmium companions, the oxide is reacted with hydrogen fluoride to holmium fluoride. Subsequently, it is reduced to metallic holmium with calcium to form calcium fluoride. Separation of remaining calcium residues and impurities takes place in an additional remelting in vacuo.

Features

The silvery white metal of the rare earths is soft and malleable.

Holmium has special magnetic properties. Its ferromagnetic properties are far superior to iron. With 10,6 μB it has the highest magnetic moment of a naturally occurring chemical element. It forms magnetic bonds with yttrium.

Holmium is relatively stable in dry air; in humid or warm air it tarnishes quickly with the formation of a yellowish oxide layer. At temperatures above 150 ° C it burns to sesquioxide Ho2O3. It reacts with water to form the hydroxide, producing hydrogen. It dissolves in mineral acids with the formation of hydrogen.

In its compounds it is present in the oxidation number + 3, the Ho3 + cations form yellow solutions in water. Under special reductive conditions, the oxidation number + 2 can also be realized for the chlorides, eg in the holmium (II, III) chloride Ho5Cl11, but the pure holmium (II) chloride does not exist.

Usage

Because of its excellent magnetic properties, Holmium pole shoes are used for high-performance magnets to generate the strongest magnetic fields.

Other applications:

1. Magnetic bubble storage using thin-film alloys of holmium iron, holmium nickel and holmium cobalt.
2. Control rods in breeding reactors.
3. Yttrium Iron Garnet (YIG), Yttrium Aluminum Garnet (YAG) and Yttrium Lithium Fluoride (YLF) doping for solid-state lasers (Holmium laser with emission wavelength of 2,1μm [7]) and microwave components in medical technology.
4. Holmium oxide for the production of yellow glass, among others because of its sharp absorption bands for calibration functions for photometers.

Holmium has no known biological function.

Holmium and holmium compounds are considered to be of low toxicity. Metal dusts are fire and explosive.

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