Polarographic Determination Of Stability Constants Research Articles

Polarographic Determination of Stability Constants of Ternary Complexes of Cadmium with α-Alanine as Primary Ligand and Oxalic Acid as Secondary Ligand

Polarographic Determination of Stability Constants of Ternary Complexes of Cadmium with α-Alanine as Primary Ligand and Oxalic Acid as Secondary Ligand

On the influence of adsorption of electroactive species on the polarographic determination of stability constants

The influence of specific adsorption of electroactive species on the polarographic determination of stability constants is studied quantitatively. An expression for the term that permits correction of the effect of the adsorption and the “true” value of the constants to be obtained from the “apparent” value is deduced. The sense of the correction shows that the “apparent” constants are always higher than the “true” ones, which is in agreement with some experimental observations. Analysis of the dependence of the correction term on the adsorption parameters shows that even moderate adsorption exerts a significant influence on the values of the stability constants.

Polarographic Determination of Stability Constants of Cadmium and Lead Ternary Complexes with Thiosemicarbazide and Thiosulphate

Polarographic Determination of Stability Constants of Cadmium and Lead Ternary Complexes with Thiosemicarbazide and Thiosulphate

Polarographic Determination of Stability Constants and Thermodynamic Parameters of the Complexes of Praseodymium(III) with Hydroxylamine, Hydrazine and Phenylhydrazine

Polarographic Determination of Stability Constants and Thermodynamic Parameters of the Complexes of Praseodymium(III) with Hydroxylamine, Hydrazine and Phenylhydrazine

The polarographic determination of stability constants of urea/crown ether complexes in methanol

A general method for determination of the stability constants of complexes of crown ethers and related compounds with small organic molecules in polar solvents is described, based on an indirect polarographic procedure. Computerized evaluation of the data forms an essential part of the procedure.

Polarographic Determination of Stability Constants and Thermodynamic Parameters of the Complexes of Nd(lll) with Hydroxyl- amine, Hydrazine and Phenylhydrazine

Polarographic Determination of Stability Constants and Thermodynamic Parameters of the Complexes of Nd(lll) with Hydroxyl- amine, Hydrazine and Phenylhydrazine

Polarographic determination of stability constants and thermodynamic parameters of lead(II) propanoate and 2-hydroxypropanoate complexes with a computer-controlled system

A computer-controlled electrometric system is described. It is used for d.c. polarographic determinations of the stability constants of lead(II) propanoate and 2-hydroxypropanoate complexes at four temperatures. From the values of the monoligand complex stability constants obtained at different temperatures, standard thermodynamic functions (Δ H j and Δ S j ) for the first and second steps of complex formation were obtained. Closed-loop interaction between the minicomputer and electrometric instrument was achieved through computer control of the potentiostat, drop-life timer, burette and valve for nitrogen purging. Computer programs are outlined for numerical and statistical evaluation of the experimental data giving E 1 2 i d and slope of logarithmic presentation of polarograms, F o functions and cumulative stability constants, β j as well as for calculation of the standard thermodynamic functions.

Indirect polarographic determination of stability constants: Zinc complexes with glycollic acid

A study of the glycollate complexes of zinc using indium as the indicator ion gave results identical to that obtained with cadmium as the indicator ion. It appears that the reversible reduction of the indicator ion is not an essential prerequisite provided that the kinetic parameters for the reduction of the indicator ion remain the same in the absence and in the presence of the metal under study.

Polarographic determination of stability constants of 2-, 3- and 4-hydroxybutyrate complexes of copper(II)

Polarographic determination of stability constants of 2-, 3- and 4-hydroxybutyrate complexes of copper(II)

Indirect polarographic determination of stability constants

Zinc, complexes of glycollic and lactic acids were studied by an indirect polarographic method using cadmium as the indicator ion. The half-wave potentials of cadmium complexes shift to more positive values in the presence of zinc. From this shift, the formation function, n, for zinc was obtained as a function of ligand concentration and the stability constants were calculated.

Improved technique for determination of stability constants by polarographic method

A technique for the polarographic determination of stability constants, including preparation of solutions within the polarographic cell and use of a three-electrode system for measurement, is presented. The necessity for numerical treatment of polarographic data and the use of a digital computer are discussed. A block diagram for complete numerical least-squares treatment of data is given. E1/2 and id are obtained by simultaneous refinement of graphically estimated values, while the stability constants are obtained by least-squares fitting of the weighted Leden polynomial, F0, to experimental data. The technique has been applied to the system of lead 2-hydroxybutyrato complexes.

On the validity of the polarographic determination of stability constants of metal ions in the case of adsorbable electroactive species

Summary The idea that anion-induced adsoprtion of the electroactive species might interfere with the determination of stability constants via shifts in the half-wave potential is critically examined. It is shown that this adsorption occurs only if the standard thermodynamic potential at the electrode-solution interface differs from that in the solution. The final conclusion is that the position of the reversible half-wave potential is not influenced by the adsorption of the electroactive species if the reactions between the complexes, and all adsorption phenomena, proceed infinitely fast.

On the validity of the polarographic determination of stability constants of metal ions in the case of adsorbable electroactive species

On the validity of the polarographic determination of stability constants of metal ions in the case of adsorbable electroactive species

Polarographic Determination of Stability Constants and Rate Constants of Iron Chelates.

Polarographic Determination of Stability Constants and Rate Constants of Iron Chelates.

The validity of the polarographic determination of stability constants of metal ions with adsorbable ligands

The validity of the widely used polarographic method for the determination of stability constants is considered for adsorbable ligands. A polarographic study of the stability constants of the lead(II)-halides indicates that results become less reliable down the group. Agreement with accepted values for the fluoride and chloride systems is good. However, the bromide and iodide stability constants are significantly higher than values obtained by other techniques. This is attributed to complexation with adsorbed ligand in the double layer. It is concluded that polarographically determined stability constants of metal ions with adsorbable ligands are liable to be higher than “true” values. Such systems would be better evaluated by other techniques.

The validity of the polarographic determination of stability constants of metal ions with adsorbable ligands

The validity of the widely used polarographic method for the determination of stability constants is considered for adsorbable ligands. A polarographic study of the stability constants of the lead(II)-halides indicates that results become less reliable down the group. Agreement with accepted values for the fluoride and chloride systems is good. However, the bromide and iodide stability constants are significantly higher than values obtained by other techniques. This is attributed to complexation with adsorbed ligand in the double layer. It is concluded that polarographically determined stability constants of metal ions with adsorbable ligands are liable to be higher than “true” values. Such systems would be better evaluated by other techniques.

Indirect polarographic determination of stability constants

The stability constants of cadmium thiosulphate complexes have been determined in 25% methanol medium. The stability constants of thiosulphate complexes of zinc and lanthanum have been determined by the indirect method using cadmium as the indicator ion.

Indirect polarographic determination of stability constants

Polarograms of cadmium at different concentrations of pyridine were taken in 0·5 M potassium nitrate medium. From a plot of the half-wave potentialvs. log (Py), the co-ordination numbers of the complexes were calculated to be one and two. The indirect method was applied to the study of cobalt complexes of pyridine. From the shift in the half-wave potentials of cadmium in the presence of cobalt, a plot of n vs. pA was obtained which indicated the presence of higher complexes of cobalt and pyridine. The stability constants were calculated.