The liquid–gas interface of oxygen–nitrogen solutions: 1. Surface tension

The capillary method of surface tension measurement has been used to measure the surface tension of oxygen–nitrogen solutions in the temperature range from 80 to 132 K. At temperatures below the nitrogen critical temperature (T_c = 126.2 K) the capillary constant and the surface tension of solutions are smaller than their additive values and vary linearly with the temperature. Experimental data are compared with the results of calculating the surface tension by the theories of Pinnes and Rowlinson.     

Dynamic surface tension of micellar solutions studied by the maximum bubble pressure method. 1. Experiment

The effect of the micelles on the dynamic surface tension of micellar surfactant solutions is studied experimentally by means of the maximum bubble pressure method. Different frequencies of bubbling ranging approximately between 1 and 30 s^–1 are applied. The time dependence of the surface tension is calculated using a dead time correction. Water solutions of two types of surfactants with different concentrations are investigated: sodium dodecyl sulfate and nonylphenol polyglycol ether. The surface tension relaxes more quickly in the presence of micelles. The characteristic times of relaxation of the surface tension seem to be in the millisecond range. The time constants observed experimentally are explained in terms of the theory of surfactant diffusion affected by micellization kinetics.     

Determination of the surface tension of surfactant solutions applying the method of Lecomte du Noüy (ring tensiometer)

Summary Starting from a comparative assessment of the outstanding works on the ring method (du Noüy) for the determination of the surface tension of liquids and its solutions it is shown that the application of this method to surfactant solutions can lead to substantial errors if one follows conventional conditions. These errors are mainly connected with so far unknown phenomena occurring during the raising of the ring and concerning the influence of the hydrophilic vessel wall above the solution level and the stretching of the solution surface. This is demonstrated quantitatively with surfactant solutions of different kind and concentration. These effects can be explained theoretically very simply by introducing certain assumptions on the behaviour of a surfactant adsorption layer on the inner vessel wall. Conditions leading to the elimination of these errors are given, thus enabling the application of the ring method to the determination of the surface tension of surfactant solutions.With 10 figures and 3 tables     

The determination of interfacial tension by differential capillary rise

A method for directly determining interfacial tension without iteration from the difference in height between two capillaries is presented. An experimental technique is described for organic liquids both lighter and heavier than water, in which the menisci recede over surfaces wetted by the aqueous phase, thus providing the most favourable conditions for zero contact angle. The values determined experimentally using tables prepared from the known shapes of sessile interfaces agree well with accepted values of the interfacial tension.     

How surface tension of surfactant solutions influences the characteristics of sprays produced by hydraulic nozzles used for pesticide application

The sprays produced by hydraulic agricultural nozzles are influenced by the surface tension of the spray liquid, but models of spray formation relate only to pure liquids with constant surface tension. The way surfactant solutions affect spray formation is studied by investigating sprays of pure liquids compared with a range of surfactant solutions. Some surfactants caused changes in the appearance of the liquid sheet produced by the nozzles, which did not occur with pure liquids, and smaller spray drop sizes than pure liquids, suggesting that other surface properties may also be important.     

An experimental investigation and modelling of the solubility, density and surface tension of 1,1,1,3,3-pentafluoropropane (R-245fa)/synthetic polyolester compressor oil solutions

This paper reports experimental data for the solubility, density and capillary constant for solutions of refrigerant 1,1,1,3,3-pentafluoropropane (R-245fa) with polyolester compressor oil Planetelf ACD 100FY over a wide range of temperatures and concentrations. The experimental data were obtained in the temperature range from 333 to 425 K and at pressures up to 33 bar using static methods. Based on information for the capillary constant, the surface tension of the solutions R-245fa/Planetelf ACD 100FY is determined. The enthalpy of liquid phase of the R-245fa/Planetelf ACD 100FY solutions is calculated. The analysis of the behaviour of the excess thermodynamic functions is carried out. Information about the changing concentration of refrigerant in the liquid phase of the refrigerant/oil solutions (ROS) and in the surface layer of the liquid phase of the ROS at increasing temperature is presented.     

Surface tension of electrolyte solutions

A simple analytic expression is derived for the excess surface tension of electrolyte solutions, which is in good agreement with the experimental data on NaCl in the concentration range up to as high as 1 M. This expression is consistent with the following two theories: (i) The recent theory of Levin and Flores-Mena (Europhys Lett (2001) 56:187), who demonstrated the important contribution of the formation of an ion free layer at the air–electrolyte solution interface, and (ii) the Onsager–Samaras theory (J Chem Phys (1934) 2:528) modified by taking into account the ion-free layer effect. It is shown that the excess surface tension consists of three parts: the contributions of the ion-free layer, the image interaction between the electrolyte ions and the ion-free layer, and the image interaction between the electrolyte ions and air.     

Surface tension of general electrolyte solutions

A simple analytic expression is derived for the surface tension of a solution of general electrolytes including symmetrical and unsymmetrical electrolytes. Following the theory of Levin and Flores-Mena (Europhys Lett (2001) 56:187), we have introduced an ion-free layer of thickness just below the Gibbs dividing surface at the air/electrolyte solution interface. We use the linearized Poisson-Boltzmann equations for the mean potential and for the local fluctuation potential around an ion in the electrolyte solution, together with the Laplace equation for these potentials in the ion-free layer. It is found that the contribution of the mean potential as well as the tangential Maxwell stress along the interface vanishes for low potentials. Experimental data by Matubayasi et al (J Colloid Interf Sci (1999) 209:398, ibid (1999) 209:403, ibid (2001) 243:444) are analyzed with the present theory in order to estimate the values of for several electrolytes.     

Dynamic surface tension of micellar solutions studied by the maximum bubble pressure method

A theoretical model for the dynamic surface tension of an air bubble expanding in micellar surfactant solution is proposed. The model accounts for the effect of expansion of the bubble surface during the adsorption of surfactant molecules (monomers) and the effect of disintegration of polydisperse micelles on the surfactant diffusion. Assuming small deviations from equilibrium and constant rate of expansion analytical expression for the surface tension and the subsurface concentration of monomers as a function of time is derived. The characteristic time of micellization is computed from the experimental data for two surfactants (sodium dodecyl sulfate and nonylphenol polyglycol ether) obtained by the maximum bubble pressure method.     

Impact of carbon dioxide on the surface tension of 1-hexanol aqueous solutions

Effects of carbon dioxide presence on the surface tension and adsorption kinetics of 1-hexanol solutions were investigated. Experiments were performed at a range of carbon dioxide vapor pressures and varying concentrations of 1-hexanol aqueous solution. Both dynamic and steady-state surface tensions of 1-hexanol aqueous solution were found to decrease with carbon dioxide pressure, and a linear relationship was observed between the steady-state surface tension and carbon dioxide pressure. To explain the experiments, adsorption and desorption of the two species (1-hexanol and carbon dioxide) from two sides of the vapor-liquid interface were considered. A modified Langmuir isotherm, the modified Langmuir equation of state and the modified kinetic transfer equation were developed. The resulting steady-state and dynamic surface tension data were modeled using the modified Langmuir equation of state and the modified kinetic transfer equation, respectively. Equilibrium constants and adsorption rate constants of 1-hexanol and carbon dioxide were evaluated through a minimization procedure for CO₂ pressures ranging from 0 to 690 kPa. From the steady-state modeling, the equilibrium parameters for 1-hexanol and carbon dioxide adsorption from vapor phase and liquid phase were found unchanged at different pressures of carbon dioxide. From the dynamic modeling, the adsorption rate constants for 1-hexanol and carbon dioxide from vapor phase and liquid phase were found to decrease with carbon dioxide pressure. Some fluctuations in the fitting parameters of the dynamic modeling (adsorption rate constants) were observed. These fluctuations may be due to experimental errors, or more likely the limitations of the model used. A major limitation of the model is related to large differences in adsorption/desorption between initial and final stages of the process, and a single set of property parameters cannot describe both initial and final states of the system. Variations may occur depending on which set of data, of initial or final states, is used in the model predictions over the entire time range.     

Disjoining pressure and the film-height-dependent surface tension of thin liquid films: New insight from capillary wave fluctuations

In this paper we review simulation and experimental studies of thermal capillary wave fluctuations as an ideal means for probing the underlying disjoining pressure and surface tensions, and more generally, fine details of the Interfacial Hamiltonian Model. We discuss recent simulation results that reveal a film-height-dependent surface tension not accounted for in the classical Interfacial Hamiltonian Model. We show how this observation may be explained bottom-up from sound principles of statistical thermodynamics and discuss some of its implications.     

毛细管口气泡的曲率半径和附加压力变化

The profiles of the curved surface at critical status during formation of a bubble are drawn schematically, and the dependence of the radius of curvature on time is obtained in this work. The curve is useful for the students to better understand the evolution of radius of curvature and excess pressure in the laboratory experiment of surface tension measurements by the bubble pressure method, and helpful to interpret the exercises regarding excess pressure.     

Study of polymer-surfactant interactions via surface tension measurements

Interactions between a polymer and a surfactant were studied via surface tension measurements. Poly(ethylene glycol) and sodium dodecyl sulfate were used as a polymer and a surfactant, respectively. The addition of polymer affected the CMC value of the surfactant. The interpretations of the data and theoretical plots of polymer-surfactant interactions are discussed using a theoretical model. Received: 28 September 2000 Accepted: 3 October 2000     

Application of the ISM EoS for polymer solutions and blends

A method for predicting an analytical equation of state for polymer mixtures and blends from surface tension and liquid state density at normal (ordinary) temperature (γ_n, ρ_n), as scaling constants, is presented. B₂(T) follows a promising corresponding-states principle. Calculation of (T) and b(T), the two other temperature-dependent constants of the equation of state, are made possible by scaling. As a result, γ_n and ρ_n are sufficient for determination of thermophysical properties of polymer mixtures and blends.

We applied the procedure to predict liquid density of poly(ethylene glycol) (PEG-200) + 1-octanol solutions and poly(propylene glycol) (PPG) + poly(ethylene glycol) (PEG-200) blends at compressed state with temperature range from 298.15 to 338.15 K and pressures up to 40 MPa. In this work, the ISM EoS is extended to polymer mixtures and blends as well as pure case without proposing any mixing rule.     

Dynamic surface tension measurements of surfactant solutions using the maximum bubble pressure method – limits of applicability

One of the essential differences in the design of bubble pressure tensiometers consists in the geometry of the measuring capillaries. To reach extremely short adsorption times of milliseconds and below, the so-called deadtime of the capillaries must be of the order of some 10 ms. In particular, for concentrated surfactant solutions, such as micellar solutions, short deadtimes are needed to minimize the initial surfactant load of the generated bubbles. A theoretical model is derived and confirmed by experiments performed for a wide range of experimental conditions, mainly in respect to variations in deadtime and bubble volume.     

Surface tension of liquid marbles

Effective surface tension of liquid marbles was measured by three independent experimental techniques: vibration, shape analysis, and maximal marble height. Marbles obtained with various powders: polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, and lycopodium, were studied. The effective surface tension depends strongly on the kind of powder coating the marble. The capillary interaction between particles coating the marble was involved for qualitative interpretation of the reported data.     

Simultaneous study of interfacial tension,surface tension,and viscosity of few surfactant solutions with survismeter

Surfaces and interfaces are receptive valuable significant property of chemical molecules due to their potential to develop several phenomena in a self‐controlled mechanism. Science of surfaces is vast and is being used industrially since time immemorial. Their accurate and simultaneous estimation is necessary; therefore, the survismeter was used for measuring them along with viscosity. Individually tensiometers, X‐ray reflective microscope, and viscometers are used for surface tension, interfacial tension, and viscosity, respectively. These devices are sophisticated, expensive, and individually consume much time and resources with poor reproducibility in measurements. Survismeter is an alternative device for similar measurements together with higher accuracies and reproducibility. It works on a principle of capillary flow and pressure gradient (PG) inside liquid‐holding and air‐filled bulbs. Several liquids have been used for study with ± 0.01 mN/m, ± 0.01 mN/m and ± 1 × 10^?5 N s/m² accuracies in respective data. Copyright © 2008 John Wiley & Sons, Ltd.     

Density and surface tension of binary mixtures of 1-ethyl-3-methylimdazolium nitrate with alcohols

New experimental data of densities and surface tensions are presented for the binary mixtures of the ionic liquid 1-ethyl-3- methyl imidazolium nitrate（[EMIM]NO₃） with methanol and ethanol.Measurements were performed at 298.15 K and atmospheric pressure,covering the whole composition range.Excess molar volumes V^E and the surface tension deviations Sy have been determined.For the excess molar volumes of binary mixture,there is a region of negative V^E at low IL mole fraction,passing through a minimum and then V^E increases and becomes positive,showing maximum at higher IL mole fraction.It is shown that the surface tension deviations Sy of[EMIM]NO₃ + methanol system are positive but those of[EMIM]NO₃ + ethanol system are negative over the entire mole fraction range.