Mercury-aqueous Solution Interface Research Articles

Critical exponents for two-dimensional condensation of organic adsorbates at the mercury-aqueous solution interface

The evaluation of critical exponent β for two-dimensional condensation of organic adsorbates at the mercury-aqueous solution interface is carried out using spin- 1 2 generalized Ising model formalism. The estimated value is in agreement with Onsager's value of 0.125 pertaining to two-dimensional Ising model with nearest neighbour interaction energies.

Kinetics of dissociation of copper(II)-proline complex by cyclic voltammetry with a Nafion®-coated electrode

The kinetics of dissociation of copper(II)-proline complexes were studied by cyclic voltammetry using two types of electrode: a hanging mercury drop and a Nafion®-coated thin mercury film. In the former case and depending on the free ligand concentration, quasi-labile behaviour and labile behaviour were observed for identical time scales of the technique used. This was attributed to the adsorption of the negatively charged free ligand on the mercury aqueous solution interface in the potential region where Cu(II) reduction occurs, subsequently inducing the adsorption of the metal ion. The use of the Nafion-modified electrode, i.e. the latter case, seemed to avoid interferences effectively due to adsorption of negatively charged compounds. Kinetic data obtained via cyclic voltammetry are in good agreement with the literature values obtained by spectroscopic techniques.

Coadsorption of 3-methylisoquinoline molecules and perchlorate ions at the mercury—aqueous solution interface

The coadsorption of 3-methyl-isoquinoline (3-MeisoQ) and perchlorate ions has been examined at the mercury—aqueous solution interface by various electrocapillary methods. As a function of the surfactant and anion concentrations, three distinct superficial films have been characterized. At very negative potentials, the perchlorate ions are excluded from the condensed film formed by vertically oriented 3-MeisoQ molecules. At less negative potentials, a transition delimits a region of existence of a mixed film where the superficial organization differs only from that prevailing more negatively by the presence of the adsorbed perchlorate. The third film is present mainly in dilute solutions of 3-MeisoQ or perchlorate.

水銀-水溶液系二相界面に生じる気泡形状の解析

水銀-水溶液系二相界面に生じる気泡形状の解析

The effect of anions on the phase transition in the adsorbed layer of thiourea at the mercury-aqueous solution interface

The condensation of thiourea (TU) molecules at a mercury electrode in concentrated aqueous solutions was investigated by using impedance measurements and cyclic voltammetric techniques. The effects of the nature and concentration of the supporting electrolyte, the temperature and the thiourea concentration on the position of the phase transition potentials are discussed. It is concluded that the hydrogen bonds between the-NH 2 groups of TU and water molecules from the outer part of the double layer are an immobilizing agent for the adsorbed TU molecules, which leads to a stable structure in the “pit” zone. Electrostatic interaction between the TU dipoles and anions is responsibile for the formation of a condensed structure at the positively-charged mercury electrode.

Molecular structure-interfacial activity relationship of N-substituted amino acids : Adsorption of N-dansylglycine at the mercury-aqueous solution interface

The adsorption of N-dansylglycine (5-dimethylaminonaphthalene-1-sulphanylglycine) in monoanionic and dianionic forms has been characterized in aqueous solution at a mercury electrode. At pH 6 (only the monoamonic form present in the bulk), N-dansylglycine is arranged on the metal surface in a perpendicular manner through the naphthyl moiety, and an attractive interaction factor among the adsorbed molecules is observed. At pH 12 (dianionic form), the molecules still arranged in a perpendicular way show a greater molecular area and no interaction factor is revealed. These features, together with those regarding a series of other N-substituted glycine derivatives previously studied, are related to some calculated structural indices, and a relationship is obtained between the adsorption Gibbs energy and Δ E l-h (the energy difference between the lowest unoccupied molecular orbital and the highest occupied one). Moreover, some local theoretical indices (net atomic charges, partial net π charges) are used in a tentative molecular interpretation of the disposition of the sorbate on the surface and of the significance of the Frumkin interaction factor. To offer a more general grounding to the argument, a group of naphthyl and benzoyl derivatives studied by Bockris and co-workers (J. Phys. Chem., 65 (1961) 2000) in very similar conditions is also considered.

Adsorption of N-acetylglycine and N-benzoylglycine at the mercury-aqueous solution interface

Adsorption of N-acetylglycine and N-benzoylglycine at the mercury-aqueous solution interface

A complete two-state multi-site adsorption isotherm for electrosorption of neutral organic compounds from solution

A two-state multi-site statistical mechanical model is analysed for the case of neutral organic compounds electrosorption from solution. The derived adsorption isotherm takes into account on a molecular level both the short-range particle-particle interactions and the field effects on the adsorbed molecules. It is also applicable to any kind of adsorbate and solvent molecules, irrespective of whether they are rigid linear or non-linear, open flexible or ring molecules and they occupy one or more lattice sites. The validity of this isotherm is tested by comparison with the experimental data of 2-butanol adsorption at the mercury—aqueous solution interface. It is found that the isotherm follows fairly well the experimental data only for low values of the size ratio parameter. However, the best fits are attained when some of the molecular parameters of the model take inappropriate values.

Adsorption of benzoic acid, N1-phenyl and N1-2-pyrimidinyl benzenesulfonamide derivatives at the mercury-aqueous solution interface

Adsorption of benzoic acid, N1-phenyl and N1-2-pyrimidinyl benzenesulfonamide derivatives at the mercury-aqueous solution interface

Adsorption of benzoic acid, N1-phenyl and N1-2-pyrimidinyl benzenesulfonamide derivatives at the mercury-aqueous solution interface

Adsorptions of ΦCOOH, ΦSO 2NHΦ and ΦSO 2NH pyrimidine were studied by a differential capacitance method at pH=12 at the dropping mercury electrode. The interfacial behaviour of each compound was compared with that of the corresponding p-amino derivative: The experimental γ max values are approximately the same, while the experimental −Δ G ads o, at constant potential, are lower by a constant contribution. Moreover, the two oxygen atoms still seem to be directly involved in the adsorption process. Finally, the relevance of the p-NH 2 substitution on the pharmacological properties of these compounds is discussed.

A study of the interfacial behavior of polyoxyethylene at a mercury—aqueous solution interface: Compact and diffuse layers

The adsorption of polyoxyethylene (POE) at a mercury-solution interface has been studied, using NaF, KF, and KCl as supporting electrolytes and polymers over a molecular weight range from 400 to 4000. In the first part, a flat configuration of the adsorbed macromolecule is put forward from an analysis of data concerning three characteristic properties of the adsorbed layer. In the second part, information on the diffuse layer in the presence of a saturated layer of POE is obtained from experiments at various salt concentrations. While the classical models of Gouy-Chapman (GC) and Stern-Grahame for the diffuse and global double layer are well verified for concentrations higher than 10 −2 M, a deviation from the theoretical expectation is found for more dilute solutions, increasing with the absolute value of the surface charge. It seems difficult to interpret this effect in terms of an artifact due to the experimental techniques or to solution impurities. Similar deviations from the GC model are expected in the case of electrophoretic measurements. A comprehensive explanation is not given but the results show that it is related to the particular nature of the double layer in the presence of polymer.

Specific adsorption of formate ions at the mercury—aqueous solution interface

Adsorption on polarized Hg electrode of formate ions from aqueous solutions of pure HCOONa using differential capacity measurements was studied. Anion specific adsorption was indicated by the cathodic shift of potential of zero charge with increase in bulk-electrolyte activity. Variation of charge due to surface excess of sodium ions (Γ + Z + F) and of charge due to specifically adsorbed formate ions ( q 1), with electrode charge ( q M ) indicated super-equivalent adsorption of formate ions at all positive charges and for all concentrations studied. Esin—Markov coefficient was found to be unreliable criterion of the occurence of specific adsorption. Logarithmic form of constant charge adsorption isotherms were found to be followed. The plots of φ M − 2 vs q 1 at constant q M were not linear and resembled those for F −, BF 4 − and CH 3COO − ions; which is attributed to relatively weak specific adsorption of anions.

Adsorption of Neutral α-Amino Acids at the Mercury-Aqueous Solution Interface and Hydrophobicity Scales of Amino Acid Side Chains at the Electrified Interfaces

Abstract The adsorption of glycine, Dl-serine, l-threonine, l-asparagine, l-glutamine, l-valine, l-leucine, l-methionine, and l-tryptophan at the mercury-aqueous sodium fluoride solution interface has been studied by measuring differential capacities, potentials of zero charge, pzc, and surface tensions at the pzc. The standard adsorption free energies for these amino acids and for the amino acids previously studied have been used to deduce hydrophobicity scales of amino acid side chains at positively charged, negatively charged, and uncharged interfaces. The hydrophobicity scale at the uncharged interface was basically similar to that of Nozaki and Tanford. When the surface was charged positively, the positions of serine and alanine, and of threonine and α-aminobutyric acid, in the scale were reversed. This reversion was primarily ascribed to the difference in the positions of maximum adsorption potentials between the amino acids with an aliphatic side chain and those with a hydroxyl group in the side chain.

On the kinetics of adsorption and desorption of perchlorate ions in the presence of 3-methyl-isoquinoline at the mercury—aqueous solution interface

Coadsorption of perchlorate ions and 3-methyl-isoquinoline molecules at the mercury—aqueous solution interface results in the formation of a condensed film. The process of ClO − 4 incorporation (or removal) is very slow. Characteristic relaxation times (about 10 −2 s) are several orders of magnitude larger than values typical of ion adsorption at a mercury—solution interface which is free from organic surfactant. The relationships between the rate of the process, the electrode potential and the amount of adsorbed ClO − 4 ions are determined and discussed. The results indicate that the rate of the overall process is controlled by a slow adsorption (or desorption) step whose kinetics are consonant with an isotherm of the Temkin type.

ChemInform Abstract: ELECTROCHEMICAL BEHAVIOR OF MONO‐ AND OLIGONUCLEOTIDES. PART VII. COMPARATIVE E STUDIES ON THE ADSORPTION OF CYTIDINE AT THE MERCURY‐AQUEOUS SOLUTION INTERFACE BY PULSE POLAROGRAPHY AND A.C. POLAROGRAPHY

Chemischer InformationsdienstVolume 11, Issue 41 Article ChemInform Abstract: ELECTROCHEMICAL BEHAVIOR OF MONO- AND OLIGONUCLEOTIDES. PART VII. COMPARATIVE E STUDIES ON THE ADSORPTION OF CYTIDINE AT THE MERCURY-AQUEOUS SOLUTION INTERFACE BY PULSE POLAROGRAPHY AND A.C. POLAROGRAPHY Y. M. TEMERK, Y. M. TEMERKSearch for more papers by this authorP. VALENTA, P. VALENTASearch for more papers by this authorH. W. + NUERNBERG, H. W. + NUERNBERGSearch for more papers by this author Y. M. TEMERK, Y. M. TEMERKSearch for more papers by this authorP. VALENTA, P. VALENTASearch for more papers by this authorH. W. + NUERNBERG, H. W. + NUERNBERGSearch for more papers by this author First published: October 14, 1980 https://doi.org/10.1002/chin.198041082AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume11, Issue41October 14, 1980 RelatedInformation

Electrochemical behaviour of mono- and oligonucleotides Part VII. Comparative studies on the adsorption of cytidine at the mercury—aqueous solution interface by pulse polarography and AC polarography

Cytidine has been investigated in order to explore the potentialities of normal pulse polarography and phase-sensitive ac polarography (out-of-phase mode) in connection with the DME for the study of the adsorption and interfacial behaviour of nucleotides. The results are compared with those of a previous study [8] by single-sweep and phase-sensitive ac voltammetry at the HMDE. While the joint application of these latter approaches yields more comprehensive and also more reliable information on the adsorption parameters, normal pulse polarography is also able to provide, with good approximation, the values of certain adsorption parameters for the dilute layer (adsorption coefficient b , free adsorption enthalpy − G 0 , interaction coefficient a ) provided the span of the drop life before the application of the pulse is adjusted to a period sufficiently long to attain adsorption equilibrium. Normal pulse polarography is particularly valuable for estimation of the kinetic parameters of the electrode process of non-adsorbed cytidine provided that the electrode surface is incompletely covered. Phase-sensitive ac polarography at the DME yields — for the adsorption parameters b , − G 0 and a — data of equivalent reliability to the more laborious approach by phase-sensitive ac voltammetry at the HMDE provided the drop time of the DME has been adjusted to a period sufficiently long to attain adsorption equilibrium.

Electrochemical behaviour of mono- and oligonucleotides: Part VII. Comparative studies on the adsorption of cytidine at the mercury-aqueous solution interface by pulse polarography and ac polarography

Cytidine has been investigated in order to explore the potentialities of normal pulse polarography and phase-sensitive ac polarography (out-of-phase mode) in connection with the DME for the study of the adsorption and interfacial behaviour of nucleotides. The results are compared with those of a previous study [8] by single-sweep and phase-sensitive ac voltammetry at the HMDE. While the joint application of these latter approaches yields more comprehensive and also more reliable information on the adsorption parameters, normal pulse polarography is also able to provide, with good approximation, the values of certain adsorption parameters for the dilute layer (adsorption coefficient b, free adsorption enthalpy − G 0, interaction coefficient a) provided the span of the drop life before the application of the pulse is adjusted to a period sufficiently long to attain adsorption equilibrium. Normal pulse polarography is particularly valuable for estimation of the kinetic parameters of the electrode process of non-adsorbed cytidine provided that the electrode surface is incompletely covered. Phase-sensitive ac polarography at the DME yields — for the adsorption parameters b, − G 0 and a — data of equivalent reliability to the more laborious approach by phase-sensitive ac voltammetry at the HMDE provided the drop time of the DME has been adjusted to a period sufficiently long to attain adsorption equilibrium.

An approach to non-specific interactions of the hydrophobe type based on the study of the interfacial behaviour of normal aliphatic alcohols

The adsorption of normal aliphatic alcohols at the mercury aqueous solution interface has been studied by measuring the differential capacity at the potential of minimum capacity ( i.e. maximum d'adsorption) as a function of the length of the aliphatic chain, the concentration of the alcohol in solution and the nature of the electrolyte [1]. C −1 is observed to vary linearly with the number of carbon atoms n C in the aliphatic chain and the slope varies with the nature of the anion of the base electrolyte (F −, Cl −, Br − or I − but not with the cation (K + or Na +). The limiting value for n C = 0 shows that the adsorbed layer includes at least a layer of water molecules which can be attributed to the hydration of the polar heads. These results, together with those given by Pleskov et al. [2], obtained by photoemission studies, suggest that the alcohol molecules are probably not adsorbed in their extended conformation. One also notes that C is independent of the alcohol concentration in solution once saturation is reached and what ever the base electrolyte. At the interface the situation is therefore the same as in solution with the appearance at this point of a new phase and this serves to illustrate the close correlation which exists between the physico-chemical properties of the interfacial phase as compared to those of the solution. This leads to the interesting conclusion that although the adsorption of alcohols on mercury have long been studied [3] this approach sheds a new light on the interaction between adsorbed surface active substances and the other solution constituents.

Adsorption of some aliphatic α-amino acids at the mercury-aqueous solution interface

Adsorption of some aliphatic α-amino acids at the mercury-aqueous solution interface

Adsorption of some aliphatic α-amino acids at the mercury—Aqueous solution interface

The adsorption of four aliphatic α-amino acids, DL-norleucine(NL), DL-norvaline(NV), DL-α-amino- n-butyric acid(ABA) and DL-α-alanine(AL), at the mercury—neutral aqueous solution interface has been studied by means of double layer capacity, potential of zero charge and surface tension at pzc. The capacity curves are interpreted in terms of two factors, the contribution of the zwitterion group and that of the hydrocarbon group. Two common intersection points observed on the capacity curves of NL, NV and ABA at various concentrations are verified to correspond to the inflection points of the surface excess vs. potential curves. The adsorption of NL, NV and ABA obeys the Frumkin isotherm. The interaction parameter and the potential dependence of the adsorption energy are discussed in terms of the two factors. The shifts of pzc with surface coverage are negative for AL and positive for ABA, NV and NL, which can be explained by assuming the existence of a small dipole component perpendicular to the mercury surface.