180 research outputs found
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
Flora otoka Vrgade i okolnih otočića
475 vascular plant taxa (441 species and 34 subspecies; 300 genera and 73 families) were recorded in the flora of the island of Vrgada and the three nearby islets (Artina, Obrovanj and Rakita), as well as two reefs, according to the literature data and our research during 2003–04.
In the crops, 108 taxa have been registered which have been included in the analyses. A taxonomical analysis was made, as well as an analysis of life forms and floral elements.Za floru otoka Vrgade te tri otočića (Artina, Obrovanj i Rakita) i dvije hridi na osnovi vlastitih istraživanja (2003.–2004.) i literaturnih podataka utvrđeno je 475 taksona vaskularnih biljaka (441 vrsta i 34 podvrste) u okviru 300 rodova i 73 porodice.
U kulturi je zabilježeno 108 taksona koji nisu uključeni u analize. Izvršena je taksonomska analiza te analiza životnih oblika i flornih elemenata
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
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
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
Polarography Determination of Free Formaldehyde on Treated Cotton Fabrics
Application of compounds which, on textile material, release small quantities of formaldehyde makes it necessary to develop an adequate analytical method. Polarography is one of the possible analytical methods to be used. This paper investigates the possibility of using an indirect DC polarographic method via semicarbazone, with direct extraction of formaldehyde in the polarographic cell.
Such a modified polarographic method is highly sensitive and selective, it makes it possible to measure small quantities of formal- hyde, while the maximum sample mass to be measured is around 0.2 g. Disturbances that presumably occur due to the presence of surface active agents on the textile material do not occur in the samples smaller than 0.2 g in 30 ml of the polarographic solution
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
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