On the complex formation between lead(II) and citrate ions in acid solution

Abstract

Complex formation between lead(II) and citrate ions ( L) has been investigated potentiometrically at 25°C and in 2 M Na(ClO 4) by using a lead amalgam electrode and a glass electrode. The experimental data can be explained by assuming the following equilibria: Pb 2++ L→ PbL log β 1, 0, 1= 4·08±0·10 Pb 2++H ++ L→ PbHL log β 1, 1, 1= 8·15±0·05 Pb 2++2H ++ L→ PbH 2L log β 1, 2, 1=10·85±0·10 Pb 2++2 L→ PbL 2 log β 1, 0, 2=6·06±0·20 Pb 2++2H ++2 L→ PbH 2L 2 log β 1, 2, 2=14·95±0·15 Pb 2++4H ++2 L→ PbH 4L 2 log β 1, 4, 2=21·68±0·15 Symbols: L = citrate ion = C 6H 5O 7 3− B = total concentration of Pb 2+ b = free concentration of Pb 2+ A = total concentration of citrate ions a = free concentration of citrate ions H = total concentration of hydrogen ions h = free concentration of hydrogen ions K n = formation constants of citric acid, defined as follows: K n = [H nL] h[H n−1L] where n=1,2,3 β q, p, r = stability constants of a species Pb q H p L r , defined as follows: β q,p,r = [Pb qH pLr] b qh pa r Charges are generally omitted.