noun
- Plural of didymium; a mixture of rare-earth elements (primarily praseodymium and neodymium) formerly thought to be a single element.
Usage: chemistry; historical; now largely obsolete as a term; the constituent elements are used separately in modern applications
Examples
- Didymiums were once used in optical filters and welding goggles.
- The discovery of didymium in the 19th century was later shown to be a mixture of two distinct elements.
- Early chemists isolated didymiums from rare-earth mineral deposits.
- Didymiums gave certain glass a characteristic purple or brown color.