4 ( Ln denote a mixture of all the lanthanides except promethium ) , and the third is a fluorocarbonate LnCO3F . Monazite also contain thorium and yttrium , which complicate handling because thorium and its decay products are radioactive . For the extraction from the ore and the isolation of individual lanthanides , several methods have been developed . The choice of method is based on the concentration and composition of the ore and on the distribution of the individual lanthanides in the resulting concentrate . Roasting the ore and subsequent acidic and basic leaching is used mostly to produce a concentrate of lanthanides . If cerium is the dominant lanthanide , then it is converted from cerium ( III ) to cerium ( IV ) and then precipitated . Further separation by solvent extractions or ion exchange chromatography yield a fraction which is enriched in europium . This fraction is reduced with zinc , zinc / amalgam , electrolysis or other methods converting the europium ( III ) to europium ( II ) . Europium ( II ) react in a way similar to that of alkaline earth metals and therefore it can be precipitated as carbonate or is co @-@ precipitated with barium sulfate . Europium metal is available through the electrolysis of a mixture of molten EuCl3 and NaCl ( or CaCl2 ) in a graphite cell , which serve as cathode , using graphite as anode . The other product is chlorine gas .