Cerium

Cerium was discovered in 1803, independently by Jons Jacob Berzelius and Wilhelm Hisinger in Sweden and by Martin Heinrich Klaproth in Germany. It was named after the asteroid Ceres, which the astronomer Giuseppe Piazzi had discovered only two years before, in 1801. Cerium is a soft, silvery, reactive metal, the most abundant of all the rare earths, used in catalytic converters, in polishing powders and in the misch-metal alloy of lighter flints. Cerium shifts readily between two oxidation states, which makes it a valuable catalyst, notably in self-cleaning oven coatings and vehicle exhaust converters, and its oxide is the standard fine abrasive for polishing glass and precision optics.

Cerium mischmetal's pyrophoric spark, the same effect that makes lighter flints work, was also exploited in tracer ammunition and aircraft countermeasure flares during the twentieth century, extending a mundane pocket-lighter mechanism into a genuine military technology. Cerium oxide additionally serves as a UV-blocking component in some glass and ceramic glazes, and it was one of the earliest rare-earth compounds put to industrial use, decades before most of its lanthanide neighbours found any application at all.

Cerium's name descends through the asteroid to Roman religion, for Ceres, the newly found celestial body, was itself named after Ceres, the goddess of grain, agriculture and the fruitful earth, whose grief for her lost daughter Proserpina was said to bring the barren season of winter. The naming of cerium so soon after the asteroid's discovery reflects a brief moment when new heavenly bodies and new elements were being found together and their names exchanged; cerium, palladium and, later, the transuranium elements all took their names from this celestial fashion. The link is one of astronomical nomenclature rather than any inherited symbolism, but it seats cerium, through Ceres, among the oldest agricultural deities of the classical world.

Ceres corresponds to the Greek Demeter, and her cult lay at the heart of the Eleusinian Mysteries, among the most celebrated religious rites of the ancient Mediterranean world, held annually near Athens for close to two thousand years and centred on the goddess's grief and her daughter's return from the underworld as an allegory of the grain's yearly death and rebirth. Cerium's naming, however playful in its astronomical origin, thus reaches back through Ceres and Demeter to one of antiquity's longest-running and most secretive religious traditions, whose initiates were sworn never to reveal what they witnessed.