Naslov
Determination of Stability Constants of Chlorocadmium Complexes in Water from Electromotive Force Measurements

Autori
Tomaš, Renato ; Višić, Marija ; Tominić, Ivo ; Sokol, Vesna

Izvornik
Croatica Chemica Acta (0011-1643) 74 (2001), 1; 91-101

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
direct potentiometry; three-electrode cell; chlorocadmium complexes; concentration stability constants

Sažetak
A potentiometric method using a three-electrode cell was applied to determine the concentration stability constants of chlorocadmium complexes in water at 298.15 K and an ionic strength I = 1 mol dm^-^3. Initially, the calibration diagrams were derived for the cadmium and chloride ion, based on the measurements of potential difference between the glass and the cadmium-amalgam electrode for known Cd^2^+ ion concentrations, and between the glass and AgCl / Ag electrode for known Cl^- ion concentrations, respectively. To determine the concentrations of free Cd^2^+ and Cl^- ions by means of calibration diagrams the potential differences between the same electrodes were measured in the three-electrode cell by changing the concentration of total chlorides while keeping the concentration of cadmium ions constant. These data were used to determine the concentration stability constants of the formed complexes CdCl^+, CdCl_2, and CdCl_3^- by applying Leden’s graphical method and three numerical methods: nonlinear regression without scaling, nonlinear regression with scaling, and orthogonal polynomials. The last two methods gave identical constants, namely: 24.6, 68, and 69 for the three complexes. The obtained concentration stability constants were compared with the available data for the same complexes obtained from the electromotive force measurements (e.m.f.) of the concentration cell with transference, calculated using the same methods. As a result it was possible to compare both experimental methods applied in determining the concentration stability constants of chlorocadmium complexes in water medium at 298.15 K and an ionic strength I = 1 mol dm^-^ 3.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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