Holmium
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Holmium is a chemical element with the element symbol Ho and atomic number 67 in the periodic table it is in the group of lanthanides and also making it one of the metals of the rare earths.
History
1878 discovered the Swiss chemist Marc Delafontaine and Jacques -Louis Soret element spectroscopically by its different absorption lines. The new element called > X <. Discovered in 1879, the Swedish chemist Per Teodor Cleve the new element independently of the two Swiss and isolated it as a yellow oxide from impure erbium ( erbium oxide ). Cleveland turned to a technology developed by Carl Gustav Mosander method; First he separated from all known contaminants before he tried to separate the rest. He received a brown residue, which he called Holmia, as well as a green residue which was named Thulia.
It was not until 1911 managed the Swedish chemist Holmberg the recovery of pure holmium. Whether he took the name holmium, proposed by Cleveland for the Swedish capital Stockholm or regarded as a derivative of his own name, is not known.
Metallic pure holmium was first produced in 1940.
Occurrence
Of course Holmium occurs only in compounds. Known holmiumhaltige minerals are:
Production and representation
After an extensive separation of the other Holmiumbegleiter the oxide is reacted with hydrogen fluoride to Holmiumfluorid. Then is reduced with calcium to form calcium fluoride to the metal holmium. The remaining calcium residues and impurities are separated in an additional remelting in a vacuum.
Properties
The silver- white lustrous rare earth metal is soft and malleable.
Holmium has special magnetic properties. In its ferromagnetic properties, it is superior to the iron far. With 10.6 mB it has the highest magnetic moment of a naturally occurring chemical element. With yttrium, it forms magnetic compounds.
In dry air Holmium is relatively stable, in moist or warm air it runs, forming a yellowish oxide layer rapidly. At temperatures above 150 ° C it burns to sesquioxide Ho2O3. With water it reacts with evolution of hydrogen for hydroxide. In mineral acids it dissolves with evolution of hydrogen.
In its compounds it is in the 3 oxidation state, the Ho3 cations forming in water yellow solutions. Under special reductive conditions can be realized in the chlorides and the oxidation number of 2, for example, in holmium (II, III ) chloride Ho5Cl11, but the pure holmium (II) chloride does not exist.
Use
Because of its excellent magnetic properties of holmium pole pieces are used for high -performance magnets to produce the strongest magnetic fields.
Other applications:
- A magnetic bubble memory using thin film alloys holmium iron, holmium and holmium nickel cobalt.
- Control rods in breeder reactors.
- Doping of yttrium iron garnet (YIG ), yttrium aluminum garnet (YAG ) and yttrium lithium fluoride ( YLF ) for solid-state laser ( holmium laser with an emission wavelength of 2.1 microns ) and microwave components in medical technology.
- Holmium oxide for the production of yellow glass, inter alia, because of its sharp absorption bands for calibration of the photometer.
Physiological
Holmium has no known biological function.
Safety
Holmium and Holmiumverbindungen are to be regarded as slightly toxic. Metal dusts are fire and explosion hazard.
Compounds
- Holmium (III ) oxide Ho2O3
- Holmium (III ) fluoride Hof3
- Holmium (III ) chloride HoCl3
- Holmium (III ) bromide HoBr3
- Holmium (III ) iodide HOI3
- Holmium (III ) sulphate Ho2 (SO4) 3 · 8 H2O: yellow in daylight, artificial light (fluorescent light ) pink crystals.
- Holmium (III ) perchlorate Ho ( ClO4 ) 3: As a standard solution for calibration of spectrometers