Investigation of Astatine Cation Electromigration

Electromigration of astatine ( 2 1 0 ' 2 " At) has been investigated in aqueous solutions of 0.25 mole I" H(Na)C10„+5 • 10" mole Γ K2Cr2 0 , o r N a 2 S 2 0 , at 25°C, 0.7 < pH < 10.4. Like K 2 Cr 2 0 , , Na2S20„ seems to oxidize astatine only to At(0) , i. e. to an univalent cation, probably being protonized hypoastatine acid (H20)nAt . The literature data on oxidation of astatine by Na, S 2 0 8 to At(AtO) were not confirmed. The mean mobility of the At(©) cation is well described by the empiric equation _ = "At(Q) (1 + *"dp · « „ ' + ) ( 1 + 6 pH) where = 7.6(3.0)· 10" molel" is the deprotonation constant of (H 2 0) n At + , δ =0.18; "ΑΙ(Θ) =+3.80(5) Χ ΙΟ" cmV"' s" . In solutions of K 2Cr 20 7 with pH > 1.7 and in solutions without oxidation agents At(0) is unstable and is converted to a neutral form, probably, At.