Studies of a Mixed Adsorption Layer of n-Butanol and m- and p-Toluidine on Mercury Electrode

1995 ◽  
Vol 60 (9) ◽  
pp. 1457-1468 ◽  
Author(s):  
Jadwiga Saba
Keyword(s):  
Rate Constants ◽  
Concentration Ratio ◽  
Adsorption Layer ◽  
Mercury Electrode ◽  
Wide Concentration Range ◽  
Surface Excess ◽  
Adsorption Layers

The mixed adsorption layers of n-butanol-m-toluidine and n-butanol-p-toluidine were studied and the surface excess of pure components and their mixtures was determined. The occurrence of synergetic coadsorption was observed. The rate constants of Zn(II) ion reduction were determined in 1 mol l-1 NaClO4 in presence of n-butanol as an inhibitor, m- and p-toluidine as accelerating substances and in their mixtures. It was found that the inhibiting or accelerating effect depends on the concentration of n-butanol and m- or p-toluidine. Compensation of these effects achieved at the concentration ratio of CBU : CpT ~ 35 and CBU : CmT ~ 85 in a wide concentration range is an evidence of toluidine predominance in the formation of a mixed adsorption layer.

Studies of a Mixed Adsorption Layer of Butan-1-ol and o-Toluidine on Mercury Electrode

2002 ◽  
Vol 67 (11) ◽  
pp. 1579-1588 ◽  
Author(s):  
Dorota Sieńko ◽  
Dorota Gugała ◽  
Jolanta Nieszporek ◽  
Joanna Jankowska ◽  
Jadwiga Saba
Keyword(s):  
Thermodynamic Analysis ◽  
Adsorption Layer ◽  
Supporting Electrolyte ◽  
Mercury Electrode ◽  
Interaction Constant ◽  
Repulsive Interaction ◽  
Surface Excess ◽  
Adsorption Parameters ◽  
Frumkin Isotherm ◽  
Adsorption Layers

The results of thermodynamic analysis of o-toluidine adsorption on a mercury electrode in the presence of various butan-1-ol amounts complete our previous studies on properties of mixed adsorption layers of toluidine isomers-butan-1-ol. The values of the relative surface excess Γ'°T obtained for o-toluidine show that adsorption of this compound decreases with increasing of butan-1-ol concentration. Analysis of adsorption parameters derived from the Frumkin isotherm indicates that in the presence of 0.33 M BuOH in 1 M NaClO4 with adjusted pH 3 as supporting electrolyte, ∆G0 values for o-toluidine are the highest and, at the same time, the strongest repulsive interaction occurs. In the presence of 0.11 M butan-1-ol, smaller values of ∆G0 for o-toluidine correspond to weaker repulsive interaction. Therefore the change of the Γ'°T value for o-toluidine as a function of butan-1-ol concentration is the result of mutual changes of ∆G0 and interaction constant A between adsorbate molecules.

The Effect of p-Toluidine on the Two-Step Electroreduction of Zn(II) in Water-Methanol and Water-Dimethylformamide

1999 ◽  
Vol 64 (4) ◽  
pp. 585-594 ◽  
Author(s):  
Barbara Marczewska
Keyword(s):  
Electron Transfer ◽  
Binary Mixtures ◽  
Rate Constant ◽  
Rate Constants ◽  
Electrode Surface ◽  
Mercury Electrode ◽  
Forward Rate ◽  
Solvent Molecules ◽  
Activated Complex

The acceleration effect of p-toluidine on the electroreduction of Zn(II) on the mercury electrode surface in binary mixtures water-methanol and water-dimethylformamide is discussed. The obtained apparent and true forward rate constants of Zn(II) reduction indicate that the rate constant of the first electron transfer increases in the presence of p-toluidine. The acceleration effect may probably be accounted for by the concept of the formation on the mercury electrode an activated complex, presumably composed of p-toluidine and solvent molecules.

scholarly journals KINETIC MODEL OF THIOUREA DIOXIDE DECOMPOSITION IN AQUEOUS SOLUTIONS OF DIFFERENT ACIDITY

2018 ◽  
Vol 61 (12) ◽  
pp. 87-93
Author(s):  
Yuri V. Polenov ◽  
Gleb A. Shestakov ◽  
Elena V. Egorova
Keyword(s):  
Kinetic Model ◽  
Rate Constants ◽  
Silver Chloride ◽  
Mercury Electrode ◽  
Calculated Data ◽  
Correlation Coefficients ◽  
F Test ◽  
Thiourea Dioxide ◽  
Dropping Mercury Electrode ◽  
The Individual

A stoichiometric mechanism for full thiourea dioxide decomposition in aqueous solution under pH of 4.0 is proposed based on dependences of concentrations of thiourea dioxide and its decomposition products on the time and literature data. The concentration of thiourea dioxide was measured via iodometry, while the intermediates were quantified using the polarography. Polarography was carried out in glass two-electrode electrochemical cell by means of PU-1 polarograph in differential mode. Dropping mercury electrode was used as working one and silver chloride as a reference one. Rate constants for individual stages are obtained via mathematical modeling, presented a system of differential equations. Absolute errors of rate constants, correlation coefficients, and F-factors were also calculated. Verification of supposed kinetic model was conducted using the comparison between experimental and calculated concentrations, F-test and the calculated values of correlation coefficients of the individual stages of the process. Supposed kinetic model of decomposition consists of a number of consequent stages including various compounds such as sulfur monoxide, thiosulfuric, sulfuric, dithionic, hydrosulfuric acids as intermediates was used for previously obtained data for pH of 8.85. To test the universality of supposed model, we simulated kinetics of thiourea dioxide decomposition reaction at pH of 8.85. Experimental kinetic data were taken from literature. The initial approximations of the individual stages constants were taken from previous calculations. Analysis of calculated data: concentration values, F-test, correlation coefficients allowed to conclude about the applicability of proposed mechanism for the process of thiourea dioxide decomposition in a weakly alkaline medium.

Steps in p-aminohippurate transport by kidney slices

1958 ◽  
Vol 196 (1) ◽  
pp. 86-92 ◽  
Author(s):  
Ernest C. Foulkes ◽  
Benjamin F. Miller
Keyword(s):  
Cell Membrane ◽  
Transport System ◽  
Rate Constants ◽  
Extracellular Space ◽  
Concentration Ratio ◽  
Tissue Concentration ◽  
The Other ◽  
Facilitated Diffusion ◽  
Tubular Lumen ◽  
Cortical Slices

The existence of two intracellular fractions of PAH was demonstrated in renal cortical slices of the rabbit on incubation with C14-labeled PAH. One of these fractions is rapidly diffusible and rapidly equilibrates with extracellular PAH. The other fraction, in contrast, diffuses and equilibrates slowly; it is responsible for the high slice to medium concentration ratio of PAH. On the basis of these results a model of the PAH transport system in slices is proposed. This consists of step I, the diffusion of PAH from the medium into the extracellular space in the tissue; there follows step II, a facilitated diffusion step at the peritubular cell membrane; within the cell step III builds up a high tissue concentration of PAH; finally step IV transfers PAH across the luminal border of the cell into the tubular lumen from which it may diffuse back into the medium. Experiments were designed in which each of these steps could be measured individually and their rate constants determined. Alteration of the value of these rate constants by specific drugs localizes the action of such compounds at the peritubular cell membrane (Benemid, 9-alphafluorohydrocortisone) or at the level of both steps II and III in the case of DNP, octanoate and Diodrast. An explanation is also offered for the effect of cold on PAH influx and efflux. It can be calculated that the contribution of step IV to the turnover of PAH in slices is not quantitatively significant.

scholarly journals Ion-Specific Effects on Equilibrium Adsorption Layers of Ionic Surfactants

2018 ◽  
Vol 2 (2) ◽  
Author(s):  
Stoyan I. Karakashev
Keyword(s):  
Experimental Validation ◽  
Adsorption Layer ◽  
Liquid Films ◽  
Thin Liquid Films ◽  
Ionic Surfactant ◽  
Surfactant Adsorption ◽  
Specific Effects ◽  
Counter Ions ◽  
The Stability ◽  
Adsorption Layers

This review article reports on the effect of the counter-ions on the ionic surfactant adsorption layer and its relation to the stability of foams and emulsions. The adsorption theory of Davies about the ionic surfactant monolayer was revisited and it is shown how to account for the type of the counter-ions. The experimental validation of this theory on thin liquid films was shown as well, thus explaining the effect of Hofmeister. However their effect on foams and emulsions is more complex. Furthermore, it is shown how the counter-ions affect in complex way the stability of foams and emulsions via the surfactant adsorption layer in the light of the newest theory. To elucidate the nature of this effect further investigation is called for. 

scholarly journals Structure and Undulations of Escin Adsorption Layer at Water Surface Studied by Molecular Dynamics

Molecules ◽  
2021 ◽  
Vol 26 (22) ◽  
pp. 6856
Author(s):  
Sonya Tsibranska ◽  
Anela Ivanova ◽  
Slavka Tcholakova ◽  
Nikolai Denkov
Keyword(s):  
Molecular Dynamics ◽  
Adsorption Layer ◽  
Gas Permeability ◽  
Surface Elasticity ◽  
Mutual Orientation ◽  
Horse Chestnut ◽  
Thin Elastic Sheets ◽  
Characteristic Wavelength ◽  
Dynamics Simulations ◽  
Adsorption Layers

The saponin escin, extracted from horse chestnut seeds, forms adsorption layers with high viscoelasticity and low gas permeability. Upon deformation, escin adsorption layers often feature surface wrinkles with characteristic wavelength. In previous studies, we investigated the origin of this behavior and found that the substantial surface elasticity of escin layers may be related to a specific combination of short-, medium-, and long-range attractive forces, leading to tight molecular packing in the layers. In the current study, we performed atomistic molecular dynamics simulations of 441 escin molecules in a dense adsorption layer with an area per molecule of 0.49 nm2. We found that the surfactant molecules are less submerged in water and adopt a more upright position when compared to the characteristics determined in our previous simulations with much smaller molecular models. The number of neighbouring molecules and their local orientation, however, remain similar in the different-size models. To maintain their preferred mutual orientation, the escin molecules segregate into well-ordered domains and spontaneously form wrinkled layers. The same specific interactions (H-bonds, dipole–dipole attraction, and intermediate strong attraction) define the complex internal structure and the undulations of the layers. The analysis of the layer properties reveals a characteristic wrinkle wavelength related to the surface lateral dimensions, in qualitative agreement with the phenomenological description of thin elastic sheets.

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