Partial Molal Volumes and Volume Changes for the Complex Formation of Metal Chelate Electrolytes, Na2[M(edta)] and K[M(hedta)(H2O)

Abstract

Abstract The partial molal volumes, V∞, of [M(edta)]2− and [M(hedta)(H2O)]− (M=Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) and H3hedta=N-(2-hydroxyethyl)ethylenediamine-N,N′,N′ -triacetic acid) and two free ligands, edta4− and hedta3−, have been determined from density measurements at 25 °C. From the results for V∞, the volume changes for the complex formation of [M(edta)]2− and [M(hedta)(H2O)]−, ΔV∞, were estimated. The values of ΔV∞, for [M(edta)]2− (32.8 to 45.8 cm3 mol−1) and for [M(hedta)(H2O)]− (25.2 to 36.5 cm3 mol−1) were large, positive ones, and a linear relationship between ΔV∞ and ΔS was observed for these metal chelate ions.