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   ScScandium

(L. Scandia, Scandinavia)

Sc at. wt. 44.956
   at. no. 21
   m.p. 1539°C 
   b.p. 2832°C
   sp. gr. 2.989 (25°C)
   valence 3. 

Scandium was discovered in 1876. 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 the minerals euxenite and gadolinite, which had not yet been found anywhere except in Scandinavia. By process- ing 10 kg of euxenite and other residues of rare-earth minerals, Nilson was able to prepare about 2 gins of scandium oxide of high purity. Cleve later pointed out that Nilson's scandium was identical with Mendeleev's eka- boron. Scandium is apparently a much more abundant element in the sun and certain stars than here on earth. It is about the 23rd most abundant element in the sun com- pared to the 50th most abundant on earth. It is widely dis- tributed on earth, occurring in very minute quantities in over 800 mineral species. The blue color of beryl (aqua- marine variety) is said to be due to scandium. It occurs as a principal component in the rare mineral thortveitite, found in Scandinavia and Malagazy. It is also found in the resi- dues remaining after the extraction of tungsten from Zinnwald woframite, and in wilkite and bazzite. Most scandium is presently being re,covered from thortveitite or as a by-product of the extraction of uranium from davidite, which contains about 0.02 % 5c203. Metallic scandium was first prepared in 1937 by Fischer, Brunger, and Grienei- sen, who electrolyzed a eutectic melt of potassium, lithium, and scandium chlorides at 7o(k8000C. Tungsten wire and a pool of molten zinc served as the electrodes in a graphite crucible. Methods of producing the metal are now some- what more complicated. The production of the first pound of 99% pure scandium metal was announced in 1960 as having been made under a U.S. Air Force contract. Scan- dium is a silvery white metal which develops a slightly ThE ELEMEN.~4Continucd) yellowish br pinkish cast upon exposure to air. It is rela- tively soft, and is repdrted to resemble yttrium and the rare- earth metals more than it resembles aluminum or titanium. It is a very light metal and has a higher melting point than aluminum, making it of interest to designers of space missiles. Scandium is not attacked ,by a 1:1 'mixture of conc. HND3 and 48 %HF. This mixture can be used to dissolve tantalum from scandium. Scandium reacts rapidly with many acids. Eleven isotopes of scandium are recognized. The metal is still expensive, costing about $20 to $60 or more per gram, or about $7500 per pound with a purity of about '99.9 %. It has been reported that several hundred pounds of scandium have now been produced (1970). Scandium oxide costs, about $8/gm. Little is yet known about the toxicity of scandium; therefore it should be handled with care.

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