Praseodymium: a metal that generates cold
How praseodymium was discovered and where it’s used
Praseodymium is a soft, ductile and malleable metal of a silvery color, and one of the lanthanide elements. Praseodymium is chemically active, and becomes covered with a green oxide film in air. It is encountered with other rare-earth metals in nature, and is the fourth most abundant lanthanide. Its content in the earth’s crust is 9.1 g/t. Praseodymium can be found in the minerals monazite and bastnaesite.
How praseodymium was discovered
In 1841, the Swedish doctor and chemist Carl Gustav Mosander discovered the “new element Didymium” (from the Greek δίδυμος — twin), with properties that were very similar to lanthanum – hence the name of the element. Scientists at the time believed that didymium was a mixture of two or more elements. In 1885, the Austrian chemist Carl Auer von Welsbach dissolved double ammonium nitrates of didymium in nitric acid, and then carried out fractional crystallization. It turned out that didymium really was a mixture of two new elements. One of these elements formed bright green oxides. The scientist called this element “praseodymium” (from the Greek πράσιος, light green and δίδυμος, twin). The second element was neodymium (from the Greek νέος, new and δίδυμος, twin).
Where praseodymium is used
There are not so many spheres for the application of praseodymium
Like its more abundant neighbors in the lanthanide group, praseodymium is used to turn glass a characteristic light green color. The first glass of this kind was manufactured at Moser Glassworks in Karlovy Vary, in the present-day Czech Republic. In the 1920s, Leo Moser, the son of the factory’s founder, developed glass on the basis of praseodymium – Prasemit. Additionally, praseodymium compounds are used to color ceramics yellow.
Praseodymium, like neodymium which was discovered along with it, is used to make powerful magnets and especially strong alloys for aircraft engines. Praseodymium also found an application in the film industry: it is present in the carbon arc lights used in film projectors and studio lighting.
In chemistry, a solid solution of praseodymium oxide and ceria or ceria-zirconia is used as an oxidation catalyst. However, the most interesting properties are displayed by silicate crystals doped with praseodymium ions, and also the intermetallic compound PrNi₅. Silicate crystals doped with praseodymium can slow down light to a few hundred meters per second!
PrNi₅ has magnetocaloric properties, which means it can change the temperature under the impact of a magnetic field. This effect in science makes it possible to approach record low temperatures – several hundredths of a degree of absolute zero on the Kelvin Scale, or -273.15 °С.
- Paul Parsons, Gail Dixon — The Periodic Table A visual guide to the elements (p.140);