Extrapolation of molar equilibrium constants to zero ionic strength and parameters dependent on it. Copper(II), nickel(II), hydrogen(I) complexes with glycinate ion and calcium(II), hydrogen(I) complexes with nitrilotriacetate ion

Abstract

The stability constants of the complexes of glycinate ion with copper(II), nickel(II) and hydrogen(I) and of nitrilotriacetate ion with calcium(II) and hydrogen(I) and the ionic product of water ( K w) were determined potentiometrically. The measurements were carried out at 25.0 °C in four different ionic strengths up to I (= I c) = 2.50 and two different ionic media (KNO 3 and (CH 3) 4NNO 3). Extrapolation of equilibrium constants to zero ionic strength and ionic strength corrections to equilibrium constants were carried out with the data obtained from both media using the TEC (thermodynamic equilibrium constant) equation and computer program. The constants of the potassium complexes with nitrilotriacetic acid at low ionic strength are also given. Successful attempts to predict equilibrium constants for other ionic media using TEC parameters and the procedure of the specific ion-interaction theory (SIT) are given. The variations of equilibrium constants with the ionic strengths and ionic media are demonstrated.