Sequanium was the proposed name for a new element found by the Romanian physicist Horia Hulubei in 1939. The name derived from the Latin word Sequana for the river Seine running through Paris where Hulubei worked at that time.
Hulubei thought he had discovered element 93 in a tantalite sample from the French region Haute-Vienne. Later it was proven that element 93 is not present in the natural environment and is only produced in nuclear reactions. The element 93 was synthesised in 1940 and named neptunium.
- Fontani, Marco (2005-09-10). "The Twilight of the Naturally-Occurring Elements: Moldavium (Ml), Sequanium (Sq) and Dor (Do)". International Conference on the History of Chemistry. Lisbon. pp. 1–8. Archived from the original on 2006-02-24. Retrieved 2007-04-08.
- Hulubei, H.; Cauchois, Y. (1939). "Nouvelles recherches sur l'élément 93 naturel". Comptes rendus 209: 476–479.
- Mcmillan, Edwin; Abelson, Philip (1940). "Radioactive Element 93". Physical Review 57 (12): 1185. Bibcode:1940PhRv...57.1185M. doi:10.1103/PhysRev.57.1185.2.