Berkelium(III) and berkelium(IV) hydroxides are both stable in 1 M sodium hydroxide solutions. Berkelium(III) phosphate (BkPO4) has been prepared as a solid, which shows strong fluorescence under argon laser (514.5 nm line) excitation.Peterson, pp. 39–40 Berkelium hydrides are produced by reacting metal with hydrogen gas at temperatures about 250 °C. They are non-stoichiometric with the nominal formula BkH2+x (0 < x < 1). Whereas the trihydride has a hexagonal symmetry, the dihydride crystallizes in an fcc structure with the lattice constant a = 523 pm.Peterson, p. 53 Several other salts of berkelium are known, including Bk2O2S, (BkNO3)3·4H2O, BkCl3·6H2O, Bk2(SO4)3·12H2O and Bk2(C2O4)3·4H2O. Thermal decomposition at about 600 °C in an argon atmosphere (to avoid oxidation to Bk2O) of Bk2(SO4)3·12H2O yields the body-centered orthorhombic crystals of berkelium(IV) oxysulfate (Bk2O2SO4). This compound is thermally stable to at least 1000 °C in an inert atmosphere.Peterson, p. 54
