Navigando in internet, ho trovato stamattina diversi post dedicati al praseodimio e al suo scopritore, il chimico austriaco Welsbach (1858-1929) - di cui ricorre oggi, 5 agosto, l'anniversario della scomparsa. I testi sono in inglese: li ho cuciti assieme, ricavando un breve brano descrittivo, su questo elemento del blocco f.
This day in 1929 Austrian chemist Carl Auer von Welsbach died. He discovered praseodymium, a chemical element that has the symbol Pr and atomic number 59.
Praseodymium is a soft, silvery, malleable and ductile metal in the lanthanide group. It is valued for its magnetic, electrical, chemical, and optical properties. It is too reactive to be found in native form, and when artificially prepared, it slowly develops a green oxide coating.
It is used as an alloying agent with magnesium to create high-strength metals that are used in aircraft engines. It forms the core of carbon arc lights which are used in the motion picture industry for studio lighting and projector lights.
Praseodymium compounds give glasses and enamels a yellow color. Silicate crystals doped with praseodymium ions has been used to slow a light pulse down to a few hundred meters per second.
Praseodymium alloyed with nickel has such a strong magnetocaloric effect that it has allowed scientists to approach within one thousandth of a degree of absolute zero.