A0.4697 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 20.00 ml aliquot of this solution was buffered, and titration of the lead, copper, and zinc in solution required 34.41 ml of 0.001473 m edta . thiosulfate was used to mask the copper in a second 25.00 ml aliquot. titration of the lead and zinc in this aliquot required 34.24 ml of the 0.001473 m edta solution. finally, cyanide was used to mask the copper and the zinc in a third 30.00 ml aliquot. titration of the lead in this aliquot required 25.97 ml of the 0.001473 m edta solution. determine the percent composition by mass of each metal in the pewter sample.