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

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

Reducing antioxidant capacity evaluated by means of a controlled potential oxidative attack

An analytical method suitable for an antioxidant sensor is presented following the response of these substances to an extensive oxidative attack imposed by electrochemical means. The electrochemical assay simulates the action of a reactive oxygen species (ROS) by means of electrolyses carried out at a potential which is settled at the formal potential of the ROS. The antioxidant activities of trolox and ascorbic, gallic and caffeic acids and of mixtures these antioxidants was estimated from the charge required for the complete oxidation of the antioxidants from assays where the oxidative attack by O2 and by O2 were simulated.Fundação para a Ciência e Tecnologia (FCT)Centro de Química da Universidade do Minh

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