What is Holmium

Holmium (pronunciation: HOHL-mee-em) is a silvery metal belonging to the group of lanthanides and represented by the chemical symbol Ho ^{[1, 2]}. It has one stable naturally occurring isotope, ¹⁶⁵Ho, with a natural abundance of 100% while its most stable radioisotope, ¹⁶³Ho has a half-life period of 4,570 years ^[3].

Where is Holmium Found

Although Holmium does not freely occur in nature, it is found as a component in several minerals including bastnaesite and monazite ^{[1, 4]}. Commercially, it is obtained from monazite, bastnaesite, and xenotime ores through ion exchange and is isolated by calcium reduction of its anhydrous fluoride ^{[1, 4, 5]}. While top 3 holmium producing countries include China, Russia, and Malaysia, the top 3 nations with the largest holmium holdings in the world are China, the CIS countries, and the USA ^[1].

History

Origin of its Name: It is derived from ‘Holmia’, the Latin name for the Swedish capital Stockholm ^[1].

Who discovered it: Holmium was discovered by the Swedish chemist Per Teodor Cleve, and independently by the Swiss chemist Louis Soret along with Marc Delafontaine ^[1].

When and How was it Discovered

In 1878, Louis Soret and Marc Delafontaine while investigating yttrium at Geneva found that it was contaminated with other lanthanoids, observing unexplained spectral lines ^{[1, 4]}. They extracted a new element ‘X’, which is now known as holmium ^[4]. In that same year, Per Teodor Cleve worked with erbium at Uppsala to discover a brown and a green substance, which he named holmia (holmium oxide) and thulia (thulium oxide) respectively ^[4].

The pure form of holmium was separated by the Swedish botanist Otto Holmberg ^[4].

Holmium Identification
Atomic number	67 [1]
CAS number	7440-60-0 [1]
Position in the periodic table	Group	Period	Block
	Lanthanides [1]	6 [1]	f [1]

Properties and Characteristics of Holmium

Atomic Data of Holmium (Element 67)

How is Holmium Used

• Since it is an excellent absorber of neutrons, its isotopes are used in the control rods of nuclear reactors to control fission chain reactions ^{[1, 4]}.
• Holmium has special magnetic properties, and so its alloys are used for producing magnets and flux concentrators for high-intensity magnetic fields ^[4].
• Holmium-doped solid-state lasers are used for medical procedures including breaking-up of kidney stones (lithotripsy), and benign prostatic hyperplasia surgeries like prostate enucleation (HoLEP), resection (HoLRP), and ablation (HoLAP) ^{[4, 8]}.
• Holmium oxide or holmia can be used as a red or yellow coloring agent for cubic zirconia and glass ^[4].

Holmium Toxicity

The element 67 is not considered to be harmful because it has low toxicity ^[4]. However, holmium salts can be toxic if orally consumed, inhaled, or injected in large amounts ^[9].

Interesting Facts

• Holmium is graphically represented by an image of the coat of arms of Stockholm, the Swedish capital after which the element is named ^[1].
• The element quickly oxidizes at high temperatures and in the moist air ^[5].

Cost of Holmium

The cost of pure holmium is $8.6 per gram and $8600 per kg ^[4], but in bulk, its price is $10 per gram ^[10].

References
1. http://www.rsc.org/periodic-table/element/67/holmium
2. https://education.jlab.org/itselemental/ele067.html
3. https://www.webelements.com/holmium/isotopes.html
4. https://www.chemicool.com/elements/holmium.html
5. https://www.livescience.com/38360-facts-about-holmium.html
6. http://www.periodictable.com/Elements/067/data.html
7. http://chemistry-reference.com/q_elements.asp?Symbol=Ho&language=en
8. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4526611/
9. http://nautilus.fis.uc.pt/st2.5/scenes-e/elem/e06740.html
10. http://hobart.k12.in.us/ksms/PeriodicTable/holmium.htm