Cerium was separated from the light rare earths by ignition of the nitrates whereby the cerous nitrate was decomposed to eerie oxide. Small scale investigations were made using sodium nitrate and magnesium nitrate hexahydrate as fluxes. A cost estimate based on data from the small scale investigations showed the sodium nitrate ignition to be more economical; therefore, bench scale investigations were made using sodium nitrate. With a weight ratio of sodium nitrate to rare earth nitrate hexahydrate of 1:2 and a temperature of approximately 295oC for 12 to 16 hours, a nearly quantitative conversion of cerous nitrate to eerie oxide was obtained. The eerie oxide obtained upon dissolving the soluble sodium nitrate and undecomposed rare earth nitrates and filtering, using "Celite'' filtering aid as a precoat, was found to be quite pure. Indications are that an even purer eerie oxide could possibly be obtained if a lower temperature for a longer length of time had been used.
Johnson, Russell W. and Olson, Edwin H., "Separation of cerium from other rare earths by ignition of the nitrates" (1958). Ames Laboratory ISC Technical Reports. 202.