Holmium Ho

Discovery

In 1878 Marc Delafontaine and Jacques-Louis Soret in Geneva noticed unexplained absorption bands in the spectrum of erbia and referred to the unknown source as "element X".

A year later, in 1879, Per Teodor Cleve at Uppsala separated erbia chemically into a brown oxide and a green oxide. He called the brown one holmia and the green one thulia. Holmium's discovery is therefore usually shared between the Geneva pair and Cleve. Cleve's holmia was not pure either: in 1886 Lecoq de Boisbaudran extracted dysprosium from it.

Origin of the name

The name comes from Holmia, the Latin name for Stockholm, Cleve's home city.

Main uses

• Surgical lasers: holmium-doped YAG lasers emit infrared light at about 2.1 micrometres, which water absorbs strongly, so the beam cuts and coagulates tissue with shallow penetration. They are widely used for lithotripsy of urinary stones and for prostate surgery.
• Magnetic pole pieces: because holmium has a very high saturation magnetisation, it is used to concentrate magnetic flux in devices that produce extremely strong static fields.
• Wavelength standards: holmium oxide glass and solutions have sharp, well-characterised absorption peaks and are used to calibrate spectrophotometers.
• Colouring: it tints glass and cubic zirconia yellow or reddish.

Isotopes

Natural holmium consists entirely of stable holmium-165. Radioactive holmium-166 (half-life about 27 hours) emits beta particles and can also be seen on MRI, so it is used in microspheres for radioembolisation of liver tumours. The long-lived isomer holmium-166m, with a half-life of around 1,200 years, serves as a calibration source for gamma spectrometers.

In everyday life

If a urologist breaks up a kidney stone with a laser, there is a good chance it is a holmium laser. In 2017 researchers reported writing and reading one bit of magnetic information on a single holmium atom sitting on a surface, a striking demonstration of atomic-scale data storage. Holmium has no known biological role and is considered to be of low toxicity.