Polarographic Investigations of Some Metal Monocarboxylato Complexes. IV. Influence of Monocarboxylic Acid on the Half-wave Potential of Metal Ions

The influence of monocarboxylic acids (formic, ace tic and butyric) on the h a lf-wa ve potential of metal ions (lead, cadmium, copper(II) and tha llium(!)) in the monocarboxyl a te buffer was established. Since this influence is opposite to that of complex formation, it is n ecessary to investigate the monocarboxylate complexes in buffers with a constant acid concentration rather than in buffers with a constant salt-acid r a tio. The positive shift of the half-wave potential with the increase of the monocarboxylic acid concentration in the buffer is caused by the change of the liquid junction potential, by the change of the activity coefficient of the ion and by the change of the viscosity of the solution

Potentiometdc Determination of Stability Constants of Cobalt(II), Nickel(II), Copper(ll), Zinc(II), Cadmium(II) and Lead(ll) Complexes in Buffer Solutions of 2- and 3-Hydroxypropanoic Acids

Stability c01I1stants of 2- and 3-hidroxypropainoate complexes of Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) have been determined by potentiometric tttration in buff.er solutions at constant ionic strength of 2 mol dm-3• The · stability constants and their 95 per cent COiilfidence interva1s were calculated with a digi.ital computer usilllg weighted least squares procedure

Inhibitory Effect of Amines on Polarographic Processes in Acid. Solution. I. D. C. Polarographic and Oscillopolarographic Investigation

The influence of some amines as capillary active substances and as corrosion inhibitors in acid solution was studied by the conventional d. c. polarographic method and oscillopolarographically. The electrode processes of thallium, cadmium, lead, zinc and bismuth have served as indicators of the inhibitor efficiency. The inhibition of the electrode processes, resulting in a decrease of the limiting current and in the shift of the half-wave potential toward more negative values as well as in a deminution of the corresponding incision on the oscillopolarographic curve, was found to increase, generally, in the order: methylamine < n-butylamine <pyridine< < aniline < quinoline < a-naphthylamine. Since the same sequence was found for the inhibition of corrosion processes, it can be concluded that the cited effects are suited for the evaluation of the inhibiting efficiency of amines in acid solutions

On the Adsorption of Lead Iodide on the Mercury Electrode

The adsorption of lead iodide on the mercury electrode was studied by the potential-sweep chronoamperometric method, by recording of polarographic current-time curves and by the measurement of the differential capacity of the electric doublelayer. From the dependence of height and potential of the adsorption peak on\u27 the concentration of iodide the solubility product of PbI2 was calcula ted (Ks = 1.3 X 10-8). From polarographic current- time curves it could be concluded that the adsorption process is controlled by diffusion and the surface excess was calculated rs= 4.3 X 10-10 mole/cm 2). The kinetics of the adsorption process is potential dependent. The measurements of the differential capacity have shown that the adsoprtion of lead occurs after previous adsorption of iodide ion and that in solutions of h igh iodide concentration the compact adsorption layer is destroyed

Polarographic Determination of Stability Constants of Cadmium and Lead Complexes in Buffer Solution of 3-Hydroxypropionic Acid and 2-, 3-, and 4-Hydroxybutyric Acids

Stability constants of 3-hydroxypropionate and 2-, 3-, and 4-hydroxybutyrate complexes of cadmium and lead have been determined by the improved three-electrode polarographic technique. The ligand solution was delivered discontinuously, directly into the electrolytic cell. Refined half-wave potentials and diffusion currents were obtained by simultaneous computer treatment of graphically determined rough data, utilizing a least-squares program. The same program was subsequently used to calculate values of the F 0 (fLl)-function, according to the method by De Ford and Hume. These values were weighted following a suggestion by Momoki, Sato and Ogawa. By least-squares fitting of the weighted polynomials, stability constants and corresponding standard errors were obtained

Polarographic Investigations of Some Metal lVIonocarhoxylato Complexes. II. Monocarboxylato Complexes of Zinc

The stability constants of zinc monocarboxylato complexes n ave been determined by the polarographic method of DeFord and Hume in water solutions of a constant ionic strength 2 and a constant monocarboxylic acid concentration of 2 M. The examinations were carried out in the monocarboxylate concentration range up to 2 M. The following values for cumulative stability constants were obtained: formato complexes f31 = 4, [32 = 3, [33 = 4, p4 = 6; acetato complexes Pt = 4, f32 = 9, p3 = 1:2, p4 = 31; propionato complexes p1 = 8, p2 = 2, p3 = 15, p4 = 43; butyrato complexes Pl= 7, p2 = 3, p3 = 26, p4 = 103

Stability Constants of Zinc Complexes with 3-Hydroxypropionate and 2-, 3-, and 4-Hydroxybutyrates

Stability constants of zinc 3-hydroxypropionato and 2-, 3-, and 4-hydroxybutyrato complexes have been determined by potentiometric titration. The constants and their standard errors have been calculated with a digital computer. On the basis of the results obtained, the stability of these complexes is discussed with respect to the ligand basicity and the position of the hydroxyl group within the ligand molecule

On the Stability of Formato, Acetato, Propionato, Butyrato, Glycolato and Chloroacetato Complexes of Cobalt, Nickel, Copper, Zinc, Cadmium and Lead

Stability constants of formato, acetato, propionato, butyrato, glycolato and chloroacetato complexes of cobalt, nickel, copper, zinc, cadmium and lead have been determined by the potentiometric method. The change of concentration of hydrogen ions in the monocarboxylate buffer has been measured. Stability constants have been obtained by means of a digital computer applying the Gauss Z programme devised by R. S. Tobias. On the basis of these results as well as the results obtained in the former investigations by the polarographic and spectrophotometric method, the stability of the investigated monocarboxylato complexes has been discussed and the corresponding orders of stability were established

Potentiometdc Determination of Stability Constants of Cobalt(II), Nickel(II), Copper(ll), Zinc(II), Cadmium(II) and Lead(ll) Complexes in Buffer Solutions of 2- and 3-Hydroxypropanoic Acids

Stability c01I1stants of 2- and 3-hidroxypropainoate complexes of Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) have been determined by potentiometric tttration in buff.er solutions at constant ionic strength of 2 mol dm-3• The · stability constants and their 95 per cent COiilfidence interva1s were calculated with a digi.ital computer usilllg weighted least squares procedure

Potentiometric Determination of Stability Constants of Cobalt(II), Nickel(II), and Cadmium(Il) Phenylacetate Complexes Using Computer Controlled Electrometric System

The stability constants of cobalt(ll), nickel(ll) and cadmium(ll) phenylacetate complexes were obtained by potentiometric titration in a buffer solution of constant ionic strength 2 mol dm-3 (NaC104) . A computer controlled semiautomatic potentiometric titration system has been constructed in order to obtain high reproducible experimental data by different types of potentiometric titration