Lanthanum was discovered in 1839 by C. G. Mosander in Stockholm, Sweden. Mosander partially decomposed a sample of cerium nitrate by heating and treating the resulting salt with dilute nitric acid. From the extracted solution, it was possible to isolate a new rare earth which Mosander called lantana, which means "hidden". The experimental work with the lanthanum was prolonged for the three following years, although the results remained unpublished.