The amalgamation behavior of heavy elements—IV the tracer chemistry of divalent mendelevium

Abstract

In this paper it is shown that the extraction of medelevium into sodium amalgam from sodium acetate solutions results in about a ten fold enrichment relative to the lighter actinides (Pu, Am, Cm, Bk). Separation of Md from the heavier actinides may be accomplished by either of two methods: (1) an amalgam containing Md, Fm, Es, and Cf can be decomposed in cold concentrated HCl and then the Md may be coprecipitated with EuCl 2 with one order of magnitude enrichment from Fm; (2) Md can be separated by electrolysis in acetate or citrate-acetate solution on an electrode of mercury amalgamated with sodium. In the lanthanide series method (2) is used to separate Eu or Sm from the other rare earths. The sequence of electrodeposition of actinides in acetate-citrate solution is Md > Fm > Es > Cf. These separation methods probably depend on the formation of stable Md 2+. The potential of the Md 3+ + e → Md 2+ couple was estimated by a series of reductions, using YbCl 2, Zn, EuCl 2, CrCl 2, VCl 2, and TiCl 3, all in 2 M HCl. All except TiCl 3 appear to reduce Md 3+ to Md 2+, which can then be coprecipitated with EuSO 4 or BaSO 4; Md is thereby enriched 10–30 X in the precipitate, relative to the daughter isotope 256Fm in solution.