An acid solution of KReO4 sample containing 26.83 mg of combined rhenium was reduced by passage through a column of granulated zinc. The effluent solution including the washings from the column, was then titrated with 0.05 N KMnO4. 11.45 mL of the standard KMnO4 was required for the reoxidation of all the rhenium to the perrhenate ion ReO4−. Assuming that rhenium was the only element reduced, what is the oxidation state to which rhenium was reduced by the zinc column?