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

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

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