From the CRC handbook of Chemistry and Physics, CRC Press, Cleveland, 55th ed., 1974-75 "The Elements" by C.R. Hammond. page B-7
Berkelium (Berkeley, home of Univ. of Calif.), Bk; at. wt. (247); at. no. 97; valence 3 or 4; sp. gr. 14(est.). Berkelium, the eighth member of the actinide transition series, was discovered in December 1949 by Thompson, Ghiorso, and Seaborg, and was the fifth transuranium element synthesized. It was produced by cyclotron bombardment of milligram amounts of Am (241) with helium ions at Berkeley, California. The first isotope produced had a mass number of 243 and decayed with a half-life of 4.6 hrs. Eight isotopes are now known and have been synthesized. The existence of Bk (249), with a half-life of 314 days, makes it feasible to isolate berkelium in weighable amounts so that its properties can be investigated with macroscopic quantities. One of the first visible amounts of a pure berkelium compound - berkelium chloride - was produced in 1962. It weighted 3 billionth of a gram. Berkelium has not yet been prepared in elemental form, but it is expected to be a silvery metal, easily soluble in dilute mineral acids, and readily oxidized by air or oxygen at elevated temperatures to form the oxide. X-ray diffraction methods have been used to identify the following compunds: BkO2, Bk2O3, BkF3, BkCl3, and BkOCl. As with other actinide elements, berkelium tends to accumulate in the skeletal system. The maximum permissible body burden of Bk(249) in the human skeleton is about 0.0004ugm. (micrograms). Because of its rarity, berkelium presently has no commericial or technological use.
