Decipium was the proposed name for a new chemical element isolated by

Marc Delafontaine Marc Delafontaine (March 31, 1837/1838, Céligny, Switzerland–1911) was a Swiss chemist and spectroscopist who was involved in discovering and investigating some of the rare earth elements. Career Delafontaine studied with Jean Charles Galis ...

from the mineral

samarskite Samarskite is a radioactive rare earth mineral series which includes samarskite-(Y), with the chemical formula and samarskite-(Yb), with the chemical formula . The formula for samarskite-(Y) is also given as . Samarskite crystallizes in the orth ...

. He published his discovery in 1878 and later published a follow-up paper in 1881. Decipium was considered to be in the cerium group of rare earths.

Harmsworth's Universal Encyclopaedia ''Harmsworth's Universal Encyclopaedia'' is an encyclopedia edited by John Hammerton and published in London, England by The Education Book Co. Ltd., a subsidiary of Northcliffe's Amalgamated Press, in 1921/22. Aimed at a middle-income market ...

vol X, 1922 p6493 Rare Earths. In 1880 spectral analysis proved that decipium had a high

samarium Samarium is a chemical element with symbol Sm and atomic number 62. It is a moderately hard silvery metal that slowly oxidizes in air. Being a typical member of the lanthanide series, samarium usually has the oxidation state +3. Compounds of samar ...

content. It is now believed that Delafontaines decipium sample was a mixture of

with traces of other

rare earth elements The rare-earth elements (REE), also called the rare-earth metals or (in context) rare-earth oxides or sometimes the lanthanides (yttrium and scandium are usually included as rare earths), are a set of 17 nearly-indistinguishable lustrous silve ...

References

Misidentified chemical elements Samarium 1878 in science {{Chem-stub