Scandium

History

(L. Scandia: Scandinavia) On the basis of the Periodic System, Mendeleev predicted the existence of ekaboron, which would have an atomic weight between 40 of calcium and 48 of titanium.

The element was discovered by Nilson in 1878 in the minerals euxenite and gadolinite, which had not yet been found anywhere except in Scandinavia. By processing 10 kg of euxenite and other residues of rare-earth minerals, Nilson was able to prepare about 2g of highly pure scandium oxide. Later scientists pointed out that Nilson's scandium was identical with Mendeleev's ekaboron.

Sources

Scandium is apparently much more abundant (the 23^rd most) in the sun and certain stars than on earth (the 50^th most abundant). It is widely distributed on earth, occurring in very minute quantities in over 800 mineral species. The blue color of beryl (aquamarine variety) is said to be due to scandium. It occurs as a principal component in the rare mineral thortveitite, found in Scandinavia and Malagasy. It is also found in the residues remaining after the extraction of tungsten from Zinnwald wolframite, and in wiikite and bazzite.

Most scandium is presently being recovered from thortveitite or is extracted as a by-product from uranium mill tailings. Metallic scandium was first prepared in 1937 by Fischer, Brunger, and Grienelaus who electrolyzed a eutectic melt of potassium, lithium, and scandium chlorides at 700 to 800oC. Tungsten wire and a pool of molten zinc served as the electrodes in a graphite crucible. Pure scandium is now produced by reducing scandium fluoride with calcium metal.

The production of the first pound of 99% pure scandium metal was announced in 1960.

Properties

Scandium is a silver-white metal which develops a slightly yellowish or pinkish cast upon exposure to air. A relatively soft element, scandium resembles yttrium and the rare-earth metals more than it resembles aluminum or titanium.

It is a very light metal and has a much higher melting point than aluminum, making it of interest to designers of spacecraft. Scandium is not attacked by a 1:1 mixture of HNO3 and 48% HF.

Uses

About 20 kg of scandium (as Sc2O3) are used yearly in the U.S. to produce high-intensity lights. The radioactive isotope ⁴⁶Sc is used as a tracing agent in refinery crackers for crude oil, etc. Alloys of scandium and aluminum are used in some kinds of athletic equipment, such as aluminum baseball bats, bicycle frames and lacrosse sticks. Scandium iodide is added to mercury vapor lamps to produc a highly efficient light source resembling sunlight, which is important for indoor or night-time color TV.

Handling

Little is yet known about the toxicity of scandium; therefore it should be handled with care.