Characteristics: Erbium metal slowly tarnishes in moist air but is more stable and does not oxidize as quickly as some other rare-earth metals. Insoluble in water, soluble in acids. Erbium salts are pink, and the element has characteristic sharp absorption spectra bands in visible light, ultraviolet, and near infrared. Low toxicity and high electrical resistivity.
Derivation: Acids are used on crushed minerals that transform insoluble rare-earth oxides into chlorides or sulfates. The filtrates are partially neutralized with caustic soda then a process is used to convert rare earths into their insoluble oxalates. By annealing the oxalates are converted to oxides, then dissolved by acid. A crystallized mixture of double salts of rare-earth metals is formed and the salts are separated by ion exchange. Eventually the rare earths are washed out by a suitable complexing agent and erbium metal is obtained by a heating process with calcium at 1450 °C under an argon atmosphere.
Erbium has been used in nuclear technology as a neutron absorber in control rods; as an alloying agent with metals such as vanadium to lower hardness and increase workability; erbium salts are used as a colorant for glass and porcelain; as a dopant in optical fiber amplifiers.
Hazards: Slightly toxic if ingested. Metallic erbium is flammable in the form of dust when exposed to an ignition source. Contact with acids may evolve flammable hydrogen gas.