Praseodymium (Pr, atomic number 59) is a lanthanide and is classed as a ‘light rare earth’ element. It is a soft, malleable, and ductile metal that has a diverse range of uses ranging from hybrid cars to iPods to welder’s goggles. It was first identified in 1885 by Carl Auer von Welsbach who named it using the Greek words prasios didymos, meaning ‘green twin’, because of the colour of its salts and its close association with neodymium.
Praseodymium occurs in the Earth’s crust at an average concentration of about 9.5 p.p.m. and, on average, 2,500 tonnes of praseodymium oxide are produced annually. The primary source of praseodymium is from bastnasite and monazite deposits in China and the United States, but it is also produced in Brazil, India, Sri Lanka, and Australia. Praseodymium is mildly toxic and long-term exposure to it in the work-place can cause health problems. Praseodymium dumping via the petrol industry or household waste has caused environmental concern as its accumulation in the soil over time can lead to damage in animals’ cell-membranes and reproductive systems.
Praseodymium is found in many popular household goods including iPods, energy saving lamps, televisions, and cigarette lighter flints. It is also an important part of the clean energy industry as one of four rare earth elements that are needed to make high strength magnets. These magnets are used in electric motors for hybrid cars and in wind turbines; the other necessary rare earth elements are dysprosium, neodymium and terbium.
In the past, when alloyed with magnesium, praseodymium was used to produce a very strong metal used in aircraft engines. Today it is still present, but only in small quantities as Didymium. Much more specialist super-alloys containing rhenium are used for the same purpose today. Furthermore, praseodymium is used to give glasses a yellow tint that filters out infrared radiation and is thus found in goggles needed to protect the eye-sight of welders and glass makers. Praseodymium oxide is also useful in the plastic industry as a catalyst in the production of goods such as soda bottles, bubble wrap, and sandwich bags. Thanks to its diverse applications in a range of high-tech and basic goods, praseodymium can be expected to maintain a strong and robust demand.
Relative atomic mass