Fermium was studies only in traced quantities. Main studies were carried out with isotopes 255Fm (T1/2 = 20.07 hours) and 257Fm (T1/2 = 100 days). Chemical properties of Fermium are generally similar to those observed for trivalent actinoids. Enthalpy of formation of infinitely diluted Fm3+ ion in water solution is -589.38 kJ/mol.
During reactions with highly concentrated acids, such as HCl, HNO3, NH4CNS, Fermium forms anion complexes and can be sorbed by anions. The stability constant of a complexes of Fm3+ with Diethylene triamine pentaacetic acid (EDTA), 1,2-diamino-cyclohexane-N,N,N',N'-tetraacetic acids, Lactic acid and Tartaric acid is 19.56, 22.70, 6.36 and 6.80 at 25°C, respectively. Fermium can be separated from other trivalent actinoids by cation-exchange chromatography with elution by 2-Hydroxy-2-methylpropanoic acid or by extraction chromatography technique with di-(ethyl hexyl)-phosphoric acid. |