decipium

{{short description|Proposed chemical element.}}

Decipium was the proposed name for a new chemical element isolated by Marc Delafontaine from the mineral samarskite. He published his discovery in 1878 and later published a follow-up paper in 1881.{{cite journal

| title = Sur le décepium, métal nouveau de la samarskite

| first = Marc

| last = Delafontaine

| journal = Journal de pharmacie et de chimie

| volume = 28

| pages = 540

| year = 1878

| url = http://gallica.bnf.fr/ark:/12148/bpt6k78100m.image.r=Decipium.f548.langEN

}}

{{cite journal

| title = Sur le décipium et le samarium

| first = Marc

| last = Delafontaine

| journal = Comptes rendus hebdomadaires des séances de l'Académie des sciences

| volume = 93

| pages = 63

| year = 1881

| url = http://gallica.bnf.fr/ark:/12148/bpt6k3049g.image.r=Decipium.f63.langEN

}}{{cite journal

| title = Sur le décepium, métal nouveau de la samarskite

| first = Marc

| last = Delafontaine

| journal = Comptes rendus hebdomadaires des séances de l'Académie des sciences

| volume = 87

| pages = 632

| year = 1878

| url = http://gallica.bnf.fr/ark:/12148/bpt6k3044x.image.r=Decipium.f694.langEN

}}

Decipium was considered to be in the cerium group of rare earths.Harmsworth's Universal Encyclopaedia vol X, 1922 p6493 Rare Earths.

In 1880, spectral analysis proved that decipium had a high samarium content. It is now believed that Delafontaine's decipium sample was a mixture of samarium with traces of other rare earth elements.{{cite book|author1=Marco Fontani|author-link= Marco Fontani|author2=Mariagrazia Costa|author3=Mary Virginia Orna|title=The Lost Elements: The Periodic Table's Shadow Side|url=https://books.google.com/books?id=Ck9jBAAAQBAJ&pg=PA122|date=13 October 2014|publisher=Oxford University Press|isbn=978-0-19-938334-4|pages=122–123}}