Non-monotonic behaviour with concentration of the surface tension of certain binary liquid alloys

The surface tension σ(c) of most liquid binary alloys usually varies with concentration c in a monotonic way between the values σ₁ and σ₂ of the two pure metals, and this behaviour is well explained by current models. Some alloys show deviations from this ideal behaviour. One of those is Fe–B. The surface tension of this liquid alloy shows a minimum at 17 atomic % B, which corresponds well with the composition of the eutectic point in the phase diagram, followed by a maximum at a concentration of 24 atomic % B or higher. The usual models for the surface tension of liquid binary alloys do not explain those exceptional features, and we propose that a model involving the concentration fluctuations in the liquid alloy has the proper ingredients to account for the features in Fe–B and similar alloys.     

A study of the refractive index and surface tension synergy of the binary water/ethanol: influence of concentration

Pure alcohols or alcohols mixed with water are the most widely used solvents in a great variety of industrial applications, including the formulation of pharmaceutical and cosmetic products. As a result of water/alcohol molecular associations, variations result in the physico-chemical characteristics of the system, such as density, viscosity, refractive index and surface tension.

The present study investigates the refractive index and the surface tension of ethanol and water mixtures at a temperature of 25°C, for different molar fractions. The data obtained allow us to study the corresponding refractive index and the surface tension synergies; in this sense, an absolute maximum refractive index is recorded for a molar fraction of 0.667, while maximum synergy (both absolute and relative) is observed for a molar fraction 0.333.

As regards surface tension, minimum absolute and relative synergy is recorded for molar fraction 0.2, since synergy is negative for the surface tensions of the mixtures.

Determinations are also made of the molar refraction of the mixtures and of the variation in refractive indices with temperature.     

Density and surface tension of pure ionic liquid 1-butyl-3-methyl-imidazolium l-lactate and its binary mixture with alcohol and water

The density and surface tension of the pure ionic liquid 1-butyl-3-methyl-imidazolium l-lactate were measured from T (293.15 to 343.15) K. The coefficient of thermal expansion, molecular volume, standard entropy, lattice energy, surface entropy, surface enthalpy, and enthalpy of vaporization were calculated from the experimental values. Density and surface tension were also determined for binary mixtures of {1-butyl-3-methyl-imidazolium l-lactate + water/alcohol (methanol, ethanol, and 1-butanol)} systems over the whole composition range from T (298.15 to 318.15) K at atmospheric pressure. The partial molar volume, excess partial molar volume and apparent molar volume of the component IL and alcohol/water in the binary mixtures were discussed as well as limiting properties at infinite dilution and the thermal expansion coefficients of the four binary mixtures. The surface properties of the four binary mixtures were also discussed.     

Surface tension and density of binary mixtures of monoalcohols,water and acetonitrile: equation of correlation of the surface tension

Measurements of the surface tension (σ) and density (ρ) of binary mixtures of monoalcohols, water and acetonitrile at 298.15 K and at atmospheric pressure, as a function of mole fraction (x) have been made. The experimental values of the deviation of surface tension and the excess of molar volume (Δσ, V ^E) have been correlated by the Redlich–Kister equation. An empirical correlation equation is presented for the study of the surface tension of these mixtures, and comparisons are made of the experimental values of surface tension versus those obtained with the correlation equation and with other models of correlation. Finally, with the purpose of corroborating the validity of the correlation equation, the latter is applied to other reference binary mixtures.     

Correlation between topological features and surface tension of binary liquid mixtures

Summary The excess surface tension of a large number of binary liquid mixtures has been correlated with their topological features quantified in terms of the molecular connectivity indices. The agreement between the calculated and experimental ^E values is reasonably well for all the mixtures. A simple correlation has also been proposed between ^E and molar excess volume (V ^E ) of a binary mixture. The correlation is quite useful in correlating ^E data even for the mixtures where either one or both the components are associated in the pure state and/or there is interaction between them.

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Korrelation zwischen topologischen Gegebenheiten und Oberflächenspannung von binären flüssigen Mischungen

Zusammenfassung Die Exzeß-Oberflächenspannungen einer großen Anzahl von binären flüssigen Mischungen wurden mit der Topologie ihrer Komponenten in Form der molekularen Konnektivitätsindices korreliert. Die Übereinstimmung zwischen den ^E -Werten ist für alle Mischungen relativ gut. Es wurde ebenfalls eine einfache Korrelation zwischen ^E und den molaren Exzeß-Volumina (V ^E ) der binären Mischungen vorgeschlagen. Diese Korrelierung ist nützlich, um die ^E -Werte sogar dann für die Korrelation von Mischungen verwenden zu können, wenn entweder eine oder beide Komponenten im Reinzustand assoziiert sind und/oder eine Wechselwirkung zwischen ihnen besteht.

     

Excess volume, changes of refractive index and surface tension of binary 1,2-ethanediol + 1-propanol or 1-butanol mixtures at several temperatures

Excess molar volume, changes of refractive index, and surface tension deviations of binary mixtures of 1,2-ethanediol+1-propanol or 1-butanol have been determined at 293.15, 298.15, 303.15, and 308.15 K. The experimental data of refractive indices and surface tensions were compared with those predicted by different empirical expressions.     

Prediction of critical temperature of n-alkanes and n-alkenes from surface tension vs. temperature data

 The surface tension versus temperature data of homologous series of n-alkanes and n-alkenes is analyzed. Critical temperatures are shown to be predicted from these data, with a very high precision, after some corrections are made. The corrections are shown to arise from the effect of the critical pressure on the extrapolated data to surface tension approaching zero. Received: 29 October 1996 Accepted: 13 December 1996     

A proposal for the estimation of binary mixture activity coefficients from surface tension measurements throughout the entire concentration range

A method to estimate the concentration dependence of the bulk activity coefficients of both binary mixture components from experimental surface tension data covering the whole concentration range is presented. To this end, high-quality experimental surface tension data as a function of the concentration, paying special attention to the diluted regions, are needed. The method is based on the application of equilibrium conditions to the surface chemical potential arisen from the Volmer equation (the simplest non-ideal surface EOS) and to the bulk chemical potential coming from the three-suffix Margules equation for activity coefficients. It can be applied provided that positive aneotropy is not present and the second derivative of the surface pressure as a function of the mole fraction is not positive in any composition region, which means rather unrestrictive conditions. In order to test the method, a compilation of 25 systems for which surface tension and activity coefficient data are simultaneously available in the literature was performed, turning out that most of them involved water. It was found that surface tension data with enough concentration coverage and good quality are really scarce, which makes the development of this kind of methods difficult.     

Measurement of surface tension of desulfurization solution and thermodynamic model-(I)

According to the need of industrial design and application of new desulfurization technique, we determine surface tension of dilute SO₂ mixture gas in DMSO and DMSO?+?Mn²⁺ mixture absorbents, and establish their thermodynamic model based on experimental data, and the surface tension calculated by the model shows good agreement with experimental data.     

Surface tension of pentafluoroethane + 1,1-difluoroethane from (243 to 328) K

The surface tension of the binary refrigerant mixture pentafluoroethane (HFC-125) + 1,1-difluoroethane (HFC-152a) was measured in the temperature range from (243 to 328) K with a differential capillary rise method, for three compositions around the composition of the optimum refrigeration performance (HFC-125 + HFC152a, 15%/85%). The uncertainties of the measurement of the temperature and the surface tension were estimated to be within ±10 mK and ±0.2 mN m⁻¹, respectively. A correlation for the surface tension of the binary refrigerant mixture HFC-152a + HFC-125 was developed as a function of the composition.     

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.     

Interfacial and aggregation properties of some anionic/cationic surfactant binary systems II. Mixed micelle formation and surface tension reduction effectiveness

Mixed micelle formation and surface tension reduction effectiveness (γ_cmc) were investigated for the following systems: triethanolammonium dodecylpoly(oxyethylene)sulfate (TADPS, containing about two ethylene oxide units)/dodecyltrimethylammonium bromide, TADPS/hexadecyltrimethylammonium bromide and TADPS/hexadecylpyridinium chloride. For all these anionic/cationic systems, the mixed critical micelle concentration (cmc) values reflect a strong synergism in mixed micelle formation, with β^M values ranging from −13.8 to −18.3. The mixed micelle composition is mixing-ratio dependent and, for equimolar mixtures, the mixed micelle is richer in the surfactant with the lower cmc. Precipitation is inhibited to a certain extent, thanks to the presence of ethylene oxide groups in the anionic species. The conditions for synergism in γ_cmc, differently expressed in the literature, can be derived from the surface tension equations established in our previous article. They can be conveniently described by a few characteristic constants: Γ _i ^∞ (saturated Gibbs excess), K _i (constant in the Szyszkowski equation), the cmc of the individual surfactants and the interaction parameters, β^S and β^M, of their mixtures. Excellent agreement between theoretically predicted and experimental results is obtained. With the increase in surfactant chain length, the β^M values decrease faster than the β^S ones and this can result in the loss of synergism in γ_cmc. Received: 11 June 2000 Accepted: 4 September 2000     

Dynamic surface tension,critical micelle concentration,and activity coefficients of aqueous solutions of nonyl phenol ethoxylates

Dynamic surface tensions, σ(t) for aqueous solutions of nonyl phenol ethoxylates (NPEOs) at the temperature 298.15 K were measured using a Lauda drop volume tensiometer. The non-ionic surfactants analyzed in this work were Tergitol NP-9, NP-35 and NP-40. By using the classical Ward and Torday equation, the diffusion coefficient for each bulk surfactant concentration was calculated. The equilibrium surface tension values were determined by extrapolating the dynamic surface tension to t → ∞ on the σ(t) vs. t^−1/2 curves. These values were used to determine the critical micelle concentrations (CMC) of the surfactant aqueous solutions as well as to calculate the infinite dilution activity coefficient of the surfactant, following a model that combines the Volmer surface equation of state and the Gibbs adsorption equation.     

Novel and accurate mathematical simulation of various models for accurate prediction of surface tension parameters through ionic liquids

Ionic Liquids (ILs) as a novel class of liquid solvent simultaneously carry the positive characteristics of both molten salts and organic liquids. Remarkable positive properties of ILs have such as low vapor pressure and excellent permittivity have encouraged the motivation of researchers to use them in various applications over the last decade. Surface tension is an important physicochemical property of ILs, which its experimental-based measurement has been done by various researchers. Despite great precision, some major shortcomings such as high cost and health-related problems caused the researchers to develop mathematical models based on artificial intelligence (AI) approach to predict surface tension theoretically. In this research, the surface tension of two novel ILs (bis [(trifluoromethyl) sulfonyl] imide and 1,3-nonylimidazolium bis [(trifluoromethyl) sulfonyl] imide) were predicted using three predictive models. The available dataset contains 45 input features, which is relatively high in dimension. We decided to use AdaBoost with different base models, including Gaussian Process Regression (GPR), support vector regression (SVR), and decision tree (DT). Also, for feature selection and hyper-parameter tuning, a genetic algorithm (GA) search is used. The final R²-score for boosted DT, boosted GPR, and boosted SVR is 0.849, 0.981, and 0.944, respectively. Also, with the MAPE metric, boosted GPR has an error rate of 1.73E-02, boosted SVR has an error rate of 2.35E-02, and it is 3.36E-02 for boosted DT. So, the ADABOOST-GPR model was considered as the primary model for the research.     

The surface tension of aqueous poly(N-isopropylacrylamide-co-acrylamide)

A series of poly(N-isopropylacrylamide-co-acrylamide) copolymers with N-isopropylacrylamide (NIPAM) to acrylamide (AM) ratios varying from 95/05 to 10/90 was synthesized and surface tensions, cloud point temperatures, and enthalpies of phase separation were measured. At 25°C, 1 wt % poly(N-isopropylacrylamide) homopolymer has a surface tension of 41.8 mJ/m². Incorporation of AM moieties in the copolymer increased surface tension approaching the limiting value of 65.3 mJ/m² which was obtained for polyacrylamide solutions. The surface tension values of copolymer solutions were predicted from the surface tensions of the homopolymers applied to a one-parameter model analogous to the Margules model for the excess free energy of mixing. Heats of phase separation for the copolymer were less than expected compared with PNIPAM homopolymer. It was proposed that NIPAM moieties directly bonded to acrylamide did not contribute to the enthalpy of phase separation. Finally, surface tension lowering kinetics were slower above the cloud point temperatures because at high temperatures the copolymers were present as colloidally dispersed particles which had to diffuse to the air/water interface, unwrap, and spread to give an adsorbed monolayer. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2137–2143, 1999     

Spontaneous non-linear surface tension oscillations in the presence of a spread surfactant monolayer at the air/water interface

The phenomena accompanying the dissolution of a surfactant droplet under the water/air interface covered by a spread monolayer are studied experimentally and theoretically. It is shown that the variation of the initial surface coverage changes the way of the system evolution. With respect to the character of changes of the interfacial tension with time one can distinguish between three different regimes which replace each other by increase of the initial surface coverage: (i) single oscillation followed by a long period of the monotonous decrease of the surface tension after which repeated non-linear oscillations develop spontaneously; (ii) repeated non-linear oscillations of the surface tension (without period of the monotonous decrease); (iii) monotonous decrease of the surface tension without any oscillation. The hydrodynamics of the observed regimes are discussed.     

气-液界面上十六烷基溴化吡啶水溶液动态表面张力的研究

滴体积法测定了十六烷基溴化吡啶溶液的动态表面张力。考察了浓度、温度对动态表面张力的影响。讨论了十六烷基溴化吡啶分子在气／液界面上的吸附动力学,发现吸附遵从扩散-动力学控制机理．从表观扩散系数计算了吸附能垒,分析了吸附能垒存在的原因。     

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     

Physicochemical properties of {1-methyl piperazine (1) + water (2)} system at T = (298.15 to 343.15) K and atmospheric pressure

Densities (ρ) and viscosities (η) of aqueous 1-methylpiperazine (1-MPZ) solutions are reported at T = (298.15 to 343.15) K. Refractive indices (n_D) are reported at T = (293.15 to 333.15) K, and surface tensions (γ) are reported at T = (298.15 to 333.15) K. Derived excess properties, except excess viscosities (Δη), are found to be negative over the entire composition range. The addition of 1-MPZ reduces drastically the surface tension of water. The temperature dependence of surface tensions is explained in terms of surface entropy (S^S) and enthalpy (H^S). The measured and derived properties are used to probe the microscopic liquid structure of the bulk and surface of the aqueous amine solutions.