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

Potentiometric Determination of Stability Constants of 2,3-Dihydroxypropanoate Complexes of Zinc(II), Cadmium(II), and Lead(II)

Stability constants of 2,3-dihydroxypropanoate complexes of zinc(II), cr. clmium(II) and lead(II) were determined by potentiometric titration in buffer solution using glass and quinhydrone electrodes. All measurements were carried out at (298.2 ± 0.1) K in buffer solutions of constant ionic strength of 2 mol dm-3• Stability constants n:id their 95 per cent confidence intervals were calculated on a digital computer using an algorithm described elsewhere11 • On the basis of the obtained stability constants, different factors governing the stability of the investigated complexes were discussed

A Polarographic Study of the Monocarboxylato Complexes of Lead

The formation of monocarboxylato complexes of lead has been investigated by polarographic method in aqueous solutions containing excess of sodium formate, acetate, propionate, butyrate, n - valerate, iso-valerate, monochloracetate, and glycollate, respectively. The concentrations of monocarboxylate ions have been ranged from 0 to 3M. To avoid the hydrolysis of monocarboxylato complexes, the solutions contained a constant concentration (2 M) of the corresponding monocarboxylic acid, and, in the case of less soluble valeric acids, 200/o of free acid

Polarographic Determination of Stability Constants of Glycerato Complexes of Cadmium and Lead

Stability constants of glycerato complexes of cadmium and lead were determined by the polarographic method. Measurements were performed in buffer solutions of sod1um salt of DL-glyceDic acid. The concentration of the glyceric aoid in the buffer solutions was constant: 0.0 7 M for cadmium, and 0.05 NI for lead. The ionic strenght of solutions was 2 and -it was kept constant by m e ans of sodium perchlorate . The following cumulative stability constants were obta;ined: Cadmium: Bi = 40, B2 = 130, B3 = 340, B = 2.10. Lead: [3 1 = 340, B2 = 5.7 X 10 3, Ba = 2.8 X 10 3, B4 = 4.8 X 10 3

On the Stability Constants of Copper(II) Formato, Acetato, Propionato, Butyrato and Glycolato Complexes Determined by the Spectrophotometric Method

In an earlier paper1 the stability constants of Oo(II), Ni(II), Zn(II), Cd(II) and Pb(II) formato, acetato, propionato, butyrato, glycolato and chloroacetato complexes, determined by potentiometric1, polarographic~ , 3 and spectrophotometric4 methods, were summarfaed. Good agreement between stability constants determined by different methods were obtained, except for the complexes specified ~n the title, which were examined spectrophotometrically and polarographically

Polarographic Investigations of Some Metal Monocarhoxylato Complexes. III. Monocarhoxylato Complexes of Cadmium and Copper

The stability constants of cadmium and copper monocarboxylato complexes have been determined by the polarog raphic method 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 of cumulative stability constants were obtained: Cadmium : formato complexes ~ 1 = 20 ± 2, ; Be = 50 ± 5, p3 = 40 ± 8, p4 = 36 ± 8; acetato complexes P1 = 40±5, B2 = 110±10, p3 = 110 ± 15, p4 = 215 ± 20; propionato complexes P1 = 30 ± 2, B2 = 80 ± 20, Ps = 400 ± 50, p4 = 290 ± 30; butyrato complexes P1 = 17 ±,2, B2 = 160 ± 20 , Bs = 400 ± 50, B4 = 480 ± 60. Copper: formato complexes p1 = 45 ± 5, Bo.= 200 ± 30, ~ 3 = = 200 ± 40 , B4 = 270 ± 40; acetato complexes Bi = 100 ± iO , B2 = 500 + 50, B3 = 1000 + 100 , P4 = 1250 + 200; propionato complexes Bi= l.10 ± 10, B2 = 450 ± 50, Ba = 1100 ± 200 , B4 = 1100 ± 200, B; = 950 ± 200; butyrato complexes B1 = 80 ± 10, P2 = 600 ± 100 , Ba = 2000 ± 300, B4 = 1700 ± 300, Ps = 2000 ± 300

On the Stability Constants of Copper(II) Formato, Acetato, Propionato, Butyrato and Glycolato Complexes Determined by the Spectrophotometric Method

In an earlier paper1 the stability constants of Oo(II), Ni(II), Zn(II), Cd(II) and Pb(II) formato, acetato, propionato, butyrato, glycolato and chloroacetato complexes, determined by potentiometric1, polarographic~ , 3 and spectrophotometric4 methods, were summarfaed. Good agreement between stability constants determined by different methods were obtained, except for the complexes specified ~n the title, which were examined spectrophotometrically and polarographically

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