Demonstration of Lanthanide Reactivity A very effectrw demunrtration of the reacuwty of the l~nthanldesinvuhes striking a cigarette 1w.htt.r ur a burner lighter. This nution 9hou.s the spontaneous ign~tionin a x c,f lanthanidc metal pieces w t h large surface area, which are no longer cobwed hg the protective cont:ng of the sparking lighter flrnt. An even mure exciting demonstratrm inr.ul\.et scraping a pieeeof "misehmetal" with a file or a knife blade. "Misehmetal" is not available from laboratory suppliers. However, a possible source is an iron foundry or a steel mill with sympathetic management. This alloy is best cut slowly with a hack saw. A convenient-sized pieee for a lecture demonstration, about 112 x 112 x 3 in., can be stored in a plastic bag. Even a tightly wrapped bag soon becomes coated with metal oxide powder. A thin coating of oxide on the metal piece does not prevent a spectacular demonstration. " M i s ~ h m e t a l "is~ a mixture of about 94% rare earth metals, mostly cerium, less than 5% iron, and small amounts of other metals. The largest use of this material is in an alloy of about 70% "misehmetal" and 30% iron. This alloy is used to make light flints. Another use of "misehmetal" is in the iron foundry in making other alloys. Addition to ferrous a h y s is generally on the order of 0.1-0.2%. The rare earths reduce and desulfurize the impurities in the mixture. Some product rare earth oxides and sulfides are found in the slag. The lanthanides that remain in the alloy may function to increase hardness, electrical and thermal conductivity, and high-temperature strength.
"Kirk-Othmer Encyclopedia of Chemical Technology," 2nd Ed., Interscience Publishers, division of John Wiley & Sons, Inc., New York, 1963-9, volume 4, page847, andvolume 17, page 160.
State University of New York a t Buffalo Buffalo, New York 14214
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