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In recent papers, electroadsorption observed at oil-water interfaces is interpreted as electrocapillarity. We studied the behavior of oil-water interfaces under electrocapillarity conditions, i.e., with an oil-water polarizable interface. For this, we observed the behavior of several typical interfaces with ionic, surface active, or inactive species. The experiments have been compared with electrocapillarity measurements and the results are compared to Blank's and Watanabe's earlier works. An explanation of the phenomenon observed, which distinguishes electroadsorption from electrocapillarity, is proposed.

The specific adsorption of ascorbate ion (AH − ) on a mercury electrode in aqueous solutions of 10 −2 M KClO 4 has been determined from electrocapillary and capacity measurements. The ascorbate anion removes the perchlorate ion from the interface when its concentration is greater than 1 × 10 −3 M . The adsorption of ascorbate anions can be fitted by a Frumkin isotherm with a value of −2.4 for the α-parameter. The standard Gibbs energy of adsorption is a linear function of the surface charge and the Δ G ° value at zero charge is −20.3 kJ mol −1 . The inner-layer capacity is analyzed into its components. Comparison of the results obtained for AH − with those reported for its conjugated acid, vitamin C, shows that the interaction energy between the electrode and both species is very close at the uncharged mercury surface. At zero charge, the anion is adsorbed less than the acid. The difference in behaviour at the interface between the anion and the acid is discussed.

The adsorption of methyldiphenylphosphine oxide, ethyldiphenylphosphine oxide, dodecyldiphenylphosphine oxide and triphenylphosphine oxide on the mercury electrode from methanolic solutions of LiCl has been studied by means of electrocapillary measurements. Results suggest that molecules of all the phosphinoxides examined are adsorbed with the phenyl and alkyl groups in contact to the mercury surface, while the polar group is directed towards the solution. The adsorption isotherms appear to be congruent with respect to both charge and potential over all the polarization range examined with an exception for dodecyldiphenylphosphine oxide which exhibits simultaneous congruence only at negative surface charges. Finally the adsorption of triphenylphosphine oxide has been found to follow a Langmuir isotherm, while the other phosphinoxides conform to a Frumkin isotherm with particle-particle repulsion. The experimental isotherms have been also analyzed by means of Bennes isotherm and the relevant adsorption parameters obtained are compared to the corresponding parameters of Frumkin's isotherm and they are further discussed.

Electrocapillary curves have been measured at the polarized nitrobenzene–water interface in the presence of dilauroylphosphatidylcholine (DLPC) in the nitrobenzene phase. DLPC formed a saturated monolayer when the concentration of DLPC was above 10 μmol dm−3. The area occupied by a DLPC molecule in the saturated monolayer was 0.93 nm2, indicating that the monolayer was in the liquid-expanded state. The stability of the monolayer was strongly affected by the electrical potential difference across the interface. The monolayer was stable when the interface was negatively polarized, i.e., the potential in the aqueous phase was negative with respect to that in the oil phase. The potential of zero charge shifted to a negative potential as the adsorption of DLPC increased, which indicated the specific adsorption of lithium ions in the aqueous phase to the head group of the DLPC molecules exposed to the aqueous phase. When the interface was positively polarized, the adsorption of DLPC abruptly decreased and the m...

It has been shown that, in a state of equilibrium, for every portion of the matter composing a system, whether contained in the homogeneous parts or in the non-homogeneous parts about the interfaces, the following equations hold :— t=T; μ1≧ M1⋅⋅⋅ μ≧Mg; for components,(μh+ahV) ≧ Mh;⋅⋅⋅( μh+ahV) ≧ Mh⋅⋅⋅(μnanV) ≧ Mn; for ions, where ah⋅⋅⋅anare the quantities of electricity associated with unit mass of ions, h⋅⋅⋅n, and where the equality refers to actual components of the matter in question, the inequality to possible components. The conditions at the interface between two phases may be obtained by the general method of Gibbs (1). A closed surface is drawn about the portion of the interface at which the conditions are to be investigated, containing parts of the two homogeneous phases and cutting the non-homogeneous parts normally to the interface. The volume V within this surface is divided into two parts I and II by a dividing surface s, which is drawn parallel to and sensibly coincident with the actual interface.

The adsorbability of surface active agents at oil-water interfaces and the influence of various norganic electrolyte on it were investigated by making electrocapillary curves. The oil phase was the solution of tetrabutylammonium chloride in methylisobutylketone, and the aqueous phase contained anionic, cationic or nonionic surface active agents in addition to the inorganic electrolyte. It was found that the interfacial tension decreased over the anodic or cathodic polarization range, depending upon whether the surface active agent was anionic or cationic. This decrease was strongly influenced by the kind and concentration of the electolyte in the aqueous phase.Linear relations held between the interfacial excess of the surface active agent and the cubic root of surface active agent concentration of the aqueous phase, as well as between the former and the cubic root of the ionic strength of the aqueous phase. These were in good agreement with Davies' equation derived theoretically. For alkylsulphate ions of various chain length, the free energy of desorption was calculated to be ca. 750 cal mol-1 for each -CH2- group.

(1913). LI. A contribution to the theory of electrocapillarity. The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science: Vol. 25, No. 148, pp. 475-481.

From measurements of electrocapillarity at oil-water interfaces, interfacial isoeleetric points, pHi * of phosphatidyl choline (PC), sphingomyeline (SM) and phosphatidyl ethanolamine (PE) were obtained as functions of the electrolyte concentration in the aqueous solutions. In the case of 10−4 M KNO3 the isoelectric point of PC was 3.3, which was in good agreement with that obtained from the electrophoresis of O/W type emulsions. The limiting values of pHi * at low electrolyte concentrations were characteristic to the lipids. They were 3.1, 2.3 and 1.4 for PC, SM and PE, respectively. The pHi * was influenced by the cationic species in the aqueous phase. For instance, for PC or SM it decreased with increasing Th4+ ion concentration. While, in the case of PE, an opposite tendency was observed. The former effect was explained by the adsorption of the Th4+ ion at the interface, thus increasing the interfacial potential. While, the latter could be ascribed to the competition between the hydrogen and metal ions for the phosphate sites of adsorbed lipid molecules.

The impedance of an electrode as a function of the potential for lowfrequency ac corresponds to the derivative of the polarization curve, while for high-frequency ac it corresponds to the electrocapillarity curve. Medium frequencies give an intermediate result.

(1935). LXXIX. The theory of electrocapillarity.—III. The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science: Vol. 19, No. 129, pp. 965-989.

Different methods of deducing the basic equation of the thermodynamic theory of electrocapillarity for hydrogen-adsorbing metals are compared. The relations that determine the value of the isoelectric potential shift under different conditions, as well as the value of the dependence of the potential on the solution pH, the free charge remaining constant, have been deduced and experimentally verified. Quantitative formulae are given for the contributions of atoms and ions to the setting up of the pd at the metal/electrolyte-solution interface.

Polyelectrolyte molecules are large and diffuse only slowly in aqueous solution. Their electrocapillary properties must be examined at static and readily accessible surfaces. Apparatus and techniques which meet these requirements have been developed to determine the differential capacity of the interfacial layer and the interfacial tension of the mercury/ solution interface. A stationary hanging drop was used for the capacity measurements and a sessile drop for the interfacial tension measurements.

The thermodynamic theory of electrocapillarity is extended to include the explicit dependence of the interfacial tension of an ideal polarized electrode on interfacial curvature. Interfacial curvature adds one additional independent variable to the electrocapillary equation. At any constant curvature, the form of the Lippmann equation, the other first partial differential coefficients of the interfacial tension and the relationship between interfacial tension and differential capacitance depend upon curvature. However, the second cross partial differential coefficients of interfacial tension and the Esin and Markov coefficient have the same form as for a planar electrode. The effect of varying curvature is investigated on the basis of a theory of Tolman, and the results obtained are applied to the estimation of the probable curvature dependence of a mercury electrode.

An optical modulator based on the electrocapillarity effect has been built and demonstrated. Optically, the device consists of a plane, variable radius circular mirror formed by the contact of mercury and a glass sheet. The mercury is also in contact with an aqueous electrolyte, and the diameter of the mirror is switched between two stable values by applying voltage pulses to the mercury/electrolyte interface. Switching times of 3 ms have been observed.

A novel means of generating and detecting surface waves at liquid–gas interfaces has been successfully developed. Electrocapillarity is used to generate the waves which are detected via specular reflection of a laser beam from the fluid surface to a position sensitive photodiode. Such a scheme is compact, sensitive, and does not mechanically touch the fluid surface. A preliminary study of highly damped waves on the magnetically oriented liquid crystal MBBA is reported.

Oil/water interfaces are classified into the ideal-polarized interface and the nonpolarized interface. The interface between a nitrobenzene solution of tetrabutylammonium tetraphenylborate and an aqueous solution of lithium chloride behaves as an ideal-polarized interface in a certain potential range. Electrocapillary curves of the interface were measured. The results are analyzed using the electrocapillary equation of the ideal-polarized interface and the Gouy-Chapman theory of diffuse double layers. The electric double layer structure consisting of the inner layer and the two diffuse double layers on each side of the interface is discussed. Electrocapillary curves of the nonpolarized oil/water interface are discussed for two cases of a nonpolarized nitrobenzene/water interface.

A new type of optical modulator has been developed, and has proved to be particularly well suited to the task of projection display. The device uses electrocapillarity (an electrochemical surface tension effect) to switch small mercury mirrors on and off. These mirror elements have the high optical efficiency required for projection light valves; they have thresholding and memory, are amenable to matrix address, and can be switched with small voltages. An 8 x 8 array has been built and operated.

Anionic surfactants constitute nearly 70% of the world production of surface-active agents. Surfactants of all types also form a large part of the formulation of commercial detergents. Thus, the determination of anionic surfactants plays a significant role in production control. For this, two-phase titration with visual indication of the end-point is regarded as the most important method. Further advance was the use of mixed indicators. The main disadvantage is the visual end-point detection. The recent literature contains many reports of potentiometric titrations with the use of liquid-membrane ion-selective electrodes. The use of other types of surfactant-selective electrodes has also been reported. Our approach is to use the phenomenon of electrocapillarity caused by the adsorption of anionic surfactants on a drop of mercury, producing a change in the electrode potential. A sitting mercury drop electrode (SMDE) was used as the end-point detector in the titration of anionic surfactants with cationic ones (antagonist titration).

A noncontact optical method for measuring the wavelength of capillary ripples on a liquid–liquid interface is proposed and demonstrated. The dispersion relationship for the aforementioned capillary waves is derived, relating the wavelength to the interfacial tension. Measurements of the wavelength, and thus the interfacial tension, are presented. Temporal measurements of the change in wavelength in response to an applied voltage (electrocapillarity) are presented and an upper limit is presented for any spatial variation of the wavelength on the interface.

In the multilayer thermodynamic framework, the authors show the influence of the dipole orientation in electrocapillary systems. In the case of a low rate of orientation in the surface layer, the electrocapillarity equation of Lipmann must be modified. The new terms allow an approach of the electrocapillary phenomena when the orientation is delayed., SCOPUS: ar.j, info:eu-repo/semantics/published

It is assumed that each atom in mercury is ionized into a positive ion and an electron. Because of the crowded state of the positive ions it is supposed that they cannot move in an electric field, while, following Sommerfeld and Pauli, the electrons are assumed to act like a completely degenerate gas following the Fermi statistics. The distribution of electrons under an electric field due to a charge on the surface of the metal is discussed, and a relation derived which gives the charge on the surface in terms of the potential difference between surface and interior. To a first approximation the charge and potential difference are proportional to each other, as if there were a condenser of constant capacity at the surface. In order to find the capacity an estimate must be made of the dielectric constant of the mercurous ions of the mercury. This is done with the aid of measurements of the refractive index of mercurous ions. The magnitude of the equivalent capacity is such that, when considered in conjunction with the diffuse layer of ions in the solution, electrocapillary curves can be explained.

A low-voltage, low-power method of electrically deforming a liquid-metal droplet via the direct manipulation of its surface tension is presented. By imposing a quasi-planar geometry on the liquid metal, its sensitivity to electrocapillary actuation is increased by more than a factor of 40. This heightened responsiveness allows the liquid metal to be deformed at rates exceeding 120 mm/s, greater than an order of magnitude faster than existing techniques for electrical deformation. Significantly, it is demonstrated how this process can be combined with voltage-controlled oxide growth on the surface of non-toxic, gallium-based liquid metals to reversibly form and maintain arbitrary, high-energy shapes.

Mesures des variations de la tension interfaciale aux interfaces electrode solide/solution en fonction du potentiel de l'electrode et evaluation du potentiel de charge nulle