A mixture containing the rare earth elements praseodymium and neodymium, used to color glass for optical filters. It was originally regarded as a single element.
- ‘The discovery of praseodymium is credited to the Austrian chemist Carl Auer who found that a previously discovered element, didymium, was actually a mixture of two other new elements.’
- ‘In 1879 Paul-Emile Lecoq, gallium's discoverer, announced that there was another element contaminating didymium, which he called samarium.’
- ‘Didymia, and its supposed elemental associate, didymium, then vanished from the chemical pantheon.’
- ‘This showed that considerably higher properties at elevated temperatures can be developed by didymium (neodidymium plus praseodidymium) and by cerium-free MM than by MM.’
Mid 19th century: from Greek didumos twin (because it was closely associated with lanthanum) + -ium (used as a suffix for new metals).
We take a look at several popular, though confusing, punctuation marks.