铁的标准电极电位：j=0.70锡的标准电极电位：j=0.14计量点前（滴定误差-0.1%）：j ＝ 0.14+(0.059/2)×3＝0.23计量点（sp）：j ＝(0.14x2+0.70)/(2+1) ＝0.33计量点后（滴定误差0.1%）：j ＝0.70+0.059×(-3) ＝0.52...