A 0.4423 g sample of pewter, containing tin, lead, copper, and
zinc, was dissolved in acid. Tin was precipitated as SnO2·4H2O and
removed by filtration. The resulting filtrate and washings were
diluted to a total volume of 200.0 mL. A 15.00 mL aliquot of this
solution was buffered, and titration of the lead, copper, and zinc
in solution required 35.87 mL of 0.001481 M EDTA. Thiosulfate was
used to mask the copper in a second 20.00 mL aliquot. Titration of...