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Electromigration of astatine ( 210 ' 2 " At) has been investigated in aqueous solutions of 0.25 mole I" 1 H(Na)C10"+5 • 10" 3 mole Γ 1 K 2 Cr 2 0, orNa 2 S 2 0, at 25°C, 0.7 < pH < 10.4. Like K 2 Cr 2 0,, Na 2 S 2 0" seems to oxidize astatine only to At(0) + , i. e. to an univalent cation, probably being protonized hypoastatine acid (H 2 0) n At + . The literature data on oxidation of astatine by Na, S 2 0 8 to At 3+ (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" 5 molel" 1 is the deprotonation constant of (H 2 0) n At + , δ =0.18; "ΑΙ(Θ) + =+3.80(5) Χ ΙΟ" 4 cm 2 V"' s" 1 . In solutions of K 2 Cr 2 0 7 with pH > 1.7 and in solutions without oxidation agents At(0) + is unstable and is converted to a neutral form, probably, At 0 .

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