21. Like most rare earth elements , praseodymium most readily forms trivalent Pr ( III ) ions. 22. Thorium has been produced in excess of demand from the refining of rare earth elements . 23. Zirconium, calcium, and rare earth elements are added for sulfide-inclusion shape control which increases formability. 24. Neodymium metal, one of the rare earth elements , is the primary raw material in neo powder. 25. The rare earth elements are often found together. 26. Thorium hydroxide is dissolved in an inorganic acid and then purified from the rare earth elements . 27. Rare earth elements patterns may also be used.28. In the original draft of the book I had three chapters on the rare earth elements . 29. Later it was shown that decipium was a mixture of samarium and other rare earth elements . 30. Sinopac is engaged in development and production of rare earth elements ( REE ) in Africa.
