Editorial Feature

Holmium (Ho) - Discovery, Occurrence, Production, Properties and Applications

Swiss chemists M. Delafontaine and J. L. Soret first observed the absorption spectrum of an unknown element in 1878. Later, in 1879, Per Theodor Cleve, a Swedish chemist discovered the element holmium while performing an experiment to remove the impurities present in the oxides of erbium using the method developed by Carl Gustaf Mosander. The results yielded two new materials that were brown and green in color. He named the brown material holmia, the oxide of holmium and green material thulia, the oxide of thulium.

Basic Information

Name Holmium
Symbol Ho
Atomic number 67
Atomic weight 164.9 amu
Standard state Solid at 298 K
CAS Registry ID 7440-60-0
Group name Lanthanoid
Period in periodic table 6
Block in periodic table f-block
Color Silvery white
Classification Metallic
Melting point 1747 K (1474°C or 2685°F)
Boiling point 2973 K (2700°C or 4892°F)
Density 8.8 g/cm3
Phase at room temperature Solid

Occurrence

It is estimated that only around 0.7 to 1.2 ppm of holmium is present in the Earth’s crust. The principal source of holmium includes ores of monazite and gadolinite minerals. It can be obtained by reducing the anhydrous fluoride using calcium metal.

Isotopes

Holmium has 30 isotopes with mass numbers ranging from 141Ho to 172Ho out of which 165Ho is a naturally-occurring stable isotope. The most stable isotope is 163Ho with a half-life of 4570 years.

Production

Pure holmium can be obtained through the reduction of holmium fluoride with calcium metal.

         2HoF3 + 3Ca → 2Ho + 3CaF2

Commercially, it is extracted mainly from monazite or gadolinite ores with sodium hydroxide, hydrochloric acid or sulfuric acid through ion exchange chromatography or solvent extraction techniques.

Key Properties

The following are the key properties of holmium:

  • It is soft, malleable and ductile.
  • It is stable in dry air at room temperature
  • It is reactive at high temperature or moist air
  • It has the highest magnetic moment of all elements present in nature
  • It often exists in its trivalent state.

Applications

Some of the major applications of holmium include the following:

  • It is used as a neutron absorber in nuclear control rods of nuclear reactors
  • It is used in filters for calibrating the wavelength settings of UV spectrophotometers
  • It is used as magnetic flux concentrator for creating strong magnetic fields
  • It is used in specialized lasers for treating eye disorder, kidney stones and cancer
  • It is used as yellow/red coloring for glass or cubic zirconia.

Sources and Further Reading

G.P. Thomas

Written by

G.P. Thomas

Gary graduated from the University of Manchester with a first-class honours degree in Geochemistry and a Masters in Earth Sciences. After working in the Australian mining industry, Gary decided to hang up his geology boots and turn his hand to writing. When he isn't developing topical and informative content, Gary can usually be found playing his beloved guitar, or watching Aston Villa FC snatch defeat from the jaws of victory.

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