Chemical properties of positive singly charged astatine ion in aqueous solution

The mobility of oxidized astatine in solutions H(Na)ClO4 (μ=0.4M)-1.10-4M K2Cr2O7 has been measured at 25 degC in the interval 0.63<=pH<=1.68. Under these conditions astatine migrates to the cathode only. The speeds of the migration depends upon the concentration of hydrogen ions in solutions are: pH 1.68 Usub(c)=1.17.10-4 cm2 V-1 s-1; pH 0.63 Usub(c)=2.67.10-4 cm2 V-1 s-1. The effect agrees with the opinion that the singly charged cation of astatine formed in acidic solutions is a strong aquacomplex [(H2O)sub(x)At]+ (x=1-2) (protonated hypoastatic acid). Deprotonation constant of this cation is Ksub(dp)=0.032+-0.005. Specific properties of the astatine cation are given. They can be explained, probably, through the peculiarities of its structure. (author)