The Tl in a 9.57-g sample of rodenticide was oxidized to the trivalent state and treated with an unmeasured excess of Mg/EDTA solution. The reaction is
Tl3+ + MgY2 → TlY- + Mg2+
Titration of the liberated Mg2+ required 12.77 mL of 0.03610 M EDTA. Calculate the percent Tl2SO4 (504.8 g/mol) in the sample.