Surface Tension Data Research Articles

A unified surface tension model for multi-component salt, organic, and surfactant solutions.

Despite the fact that the surface tension of liquid mixtures is of great importance in numerous fields and applications, there are no accurate models for calculating the surface tension of solutions containing water, salts, organic, and amphiphilic substances in a mixture. This study presents such a model and demonstrates its capabilities by modelling surface tension data from the literature. The presented equations not only allow to model solutions with ideal mixing behaviour but also non-idealities and synergistic effects can be identified and largely reproduced. In total, 22 ternary systems comprising 1842 data points could be modelled with an overall root mean squared error (RMSE) of 3.09 mN m-1. In addition, based on the modelling of ternary systems, the surface tension of two quaternary systems could be well predicted with RMSEs of 1.66 mN m-1 and 3.44 mN m-1. Besides its ability to accurately fit and predict multi-component surface tension data, the model also allows to analyze the nature and magnitude of bulk and surface non-idealities, helping to improve our understanding of the physicochemical mechanisms that influence surface tension.

Surface accumulation and acid-base equilibrium of phenol at the liquid-vapor interface.

We have investigated the surfactant properties of phenol in aqueous solution as a function of pH and bulk concentration using liquid-jet photoelectron spectroscopy (LJ-PES) and surface tension measurements. The emphasis of this work is on the determination of the Gibbs free energy of adsorption and surface excess of phenol and its conjugate base phenolate at the bulk pKa (9.99), which can be determined for each species using photoelectron spectroscopy. These values are compared to those obtained in measurements well below and well above the pKa, where pure phenol or phenolate, respectively, are the dominant species, and where the Gibbs free energy of adsorption determined from surface tension and LJ-PES data are in excellent agreement. At the bulk pKa the surface-sensitive LJ-PES measurements show a deviation of the expected phenol/phenolate ratio in favor of phenol, i.e., an apparent upward shift of the at the surface. In addition, the Gibbs free energies of adsorption determined by LJ-PES at the bulk pKa for phenol and phenolate deviate from those observed for the pure solutions. We discuss these observations in view of the different surface propensity of phenol and phenolate as well as potential cooperative interactions between them in the near-surface region.

Surface tension of falling droplets at high temperature

Surface tension is an essential parameter that defines many aspects of materials processing. In particular, at high temperatures, surface tension data of metals is missing. Due to the challenges during high temperature measurements, mainly extrapolated or theoretical data are available. Therefore, an adaption of the falling oscillating droplet method is suggested to derive surface tension values of liquid steel surfaces. A spherical droplet was pre-positioned on plastic foil to be melted by a laser beam. During falling, high-speed imaging could record the oscillations and related frequency spectra were derived. Based on extracted characteristic frequencies, surface tension values were obtained comparing different theoretical models and adaptions to impacts of gravity, asphericity and viscosity of the material. The method was shown to give reasonable values of surface tension when accounting for gravity impacts.

A study on the dilational modulus of adsorbed globular protein films – Under a near periodic area fluctuation and rapid surface perturbation

BackgroundUnderstanding how surface area (SA) fluctuation affects the dilational modulus (E) of globular protein films is crucial for evaluating their mechanical properties and practical utility. However, limited reports are available in the literature and the measurement error is unclear. MethodThe impact of SA fluctuation and large, forced perturbation on the E of bovine serum albumin (BSA) and human serum albumin (HSA) film was investigated. The E was evaluated by analyzing surface tension (ST) and SA relaxation data obtained using a pendant bubble tensiometer. Significant findingsThe data revealed that a large fluctuation in SA exerted a notable influence on the E: a distinct peak and minima in E being detected at the onset and end, respectively (at magnitude ΔA/A > ∼3 % and at oscillation frequency ƒ = 0.3 – 1.1 mHz for adsorbed BSA/HSA film). In contrast, a comparatively smaller SA fluctuation caused only a slight variation in E. Furthermore, a large, forced perturbation led to a rise in E, exhibiting a distinctly high value after a rapid bubble compression, followed by a subsequent decrease to a distinctly low E.

Exploring the effects of interactions between nonylphenol ethoxylate and ionic surfactants on interfacial and foaming properties

Nonylphenol ethoxylate (NPE-9) is a widely recognized non-ionic surfactant that finds extensive applications in various industries, including detergency, emulsification, and agriculture. Combining NPE-9 with an ionic surfactant reflects an inexpensive and highly promising approach for enhancing the efficacy of NPE-9. This study explores the molecular interactions between NPE-9 and ionic surfactants (SDS and CTAB) and examines the impact of these interactions on interfacial properties and foaming. The micellization parameters, including the critical micelle concentration (CMC), degree of counterion binding (β), degree of counterion dissociation (α), and change in free energy of micellization (ΔGmic), were investigated for sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) in the presence and absence of NPE-9, using conductometric measurements. The combined effect of NPE-9 and an ionic surfactant resulted in a synergistic interaction, reducing the CMC of the ionic surfactant, and promoting the formation of micelles. The interaction between NPE-9 and ionic surfactants at the air/water interface was investigated using surface tension measurements. The interfacial properties improved through the competitive adsorption and synergistic effect observed between NPE-9 and an ionic surfactant. In this context, the surface tension data of NPE-9 is utilized to calculate interfacial parameters, including maximum surface excess concentration (Γmax), minimum area per molecule (Amin), and surface effectiveness (π). Adding SDS and CTAB to NPE-9 solutions resulted in a notable enhancement in foamability and foam stability. The utilization of various techniques consistently produced improvements in the interfacial and foaming properties of NPE-9.

Pressure dependence of adsorption isotherm parameters and transport dynamics of a nonionic surfactant, LS-36, at the carbon dioxide (CO[formula omitted]) gas–liquid water interface

Surfactants are important to a wide variety of elevated pressure processes; however, little is understood about the effect of pressure on surfactant interfacial thermodynamics or transport. While some experimental studies exist, concrete conclusions are difficult to infer due to experimental artifacts, e.g., non-equilibrium conditions. We recently showed that few experiments are capable of achieving bulk fluid saturation, which is essential to careful measurements of surfactant thermodynamics and transport dynamics. In other words, the accurate study of surfactant adsorption equilibrium and transport parameters first and foremost requires bulk fluids that are otherwise in equilibrium. This work uses our recently developed high pressure microtensiometer (HPMT), which ensures bulk phase saturation, to measure thermodynamic isotherms for tri(ethylene glycol)-hexa(propylene glycol)-monododecyl ether (LS-36) surfactant (concentrations between 10−7 and 10−3mol/L and pressures between 1 and 57bar) at the CO2 gas–liquid water surface. All measurements were conducted at 22.5 °C. Note that in this study, the surfactant was dissolved in the liquid water phase and is unable to partition into the gaseous CO2 phase. Isotherms at different pressures were determined from surface tension data, analyzed, and compared to determine trends in thermodynamic parameters. Dynamic surface tension measurements were performed to assess transport dynamics in terms of the well-studied diffusion timescale. We find that surface tension depends non-linearly on pressure and surfactant concentration, such that surfactants are less effective at lowering surface tension as pressure increases. Furthermore, surfactant adsorption is a non-monotonic function of pressure and goes through a maximum at intermediate pressures. This result suggests that surfactant adsorption is strongly dependent on the free energy of the CO2-water surface. Overall, this work shows that the thermodynamics of surfactants at equilibrium surfaces under pressure are non-trivial and need additional investigation to quantify the driving forces for surfactant adsorption and to develop models for high pressure processes.

Estimation of the Thermophysical Properties of Pentaalkylguanidinium-Based Magnetic Ionic Liquids with Unusual Thermal Expansion Coefficient.

The thermal expansion coefficient (αexp. ), the molecular volume (Vm ), the entropy of surface formation (Sa ), and the Gibbs energy of surface formation (Ea ) of four pentaalkylguanidinium-based MILs [Cn TMG][FeCl3 Br] (n=2, 4, 6, 8) were calculated based on the density and surface tension data determined from 278.15 to 323.15 K. In terms of classical semiempirical methods, the standard molar entropy (S0 ), the lattice energy (UPOT ), the molar enthalpy of evaporation ( , (298 K)), and the thermal expansion coefficient (αest. ) of the MILs were further estimated. The estimation results indicate that the classical semiempirical methods are suitable for estimating the thermophysical properties of the MILs, except the unusual αexp. , which were extremely larger than those of representative non-magnetic ionic liquids (ILs). We further optimized the estimation methods and discussed the potential reasons for the unusual thermal expansion coefficient of the MILs.

Thermodynamic Evaluation of the Surface Tension and Viscosity of Liquid Quaternary Alloys: The Ti-Al-Cr-Nb System

Surface tension and viscosity of complex Ti-based industrial alloys are important for simulation of liquid assisted industrial processes such as casting, joining, crystal growth and infiltration. Modelling of the interface and mass transport during liquid-solid phase transition requires reliable surface tension and viscosity data. Therefore, to obtain accurate predictions of microstructural evolution during solidification related processes, only reliable input data are necessary. In the case of liquid Ti-Al alloys, the experimental difficulties related to high temperature measurements and reactivity of these alloys with supporting materials or containers as well as inevitable presence of oxygen may lead to data gaps including a complete lack of property data. An alternative for container-based methods are containerless processing techniques that offer a significant accuracy improvement and / or make possible to measure temperature and composition dependent thermophysical properties of metallic melts, as in the case of the Ti-Al-Cr-Nb system. Advanced mathematical models and computer simulations, developed in several theoretical frameworks, can be used to compensate the missing data; on the other side, for the validation of theoretical models, the experimental data are used. In the present work, an evaluation of the surface tension and viscosity of liquid Ti-Al-Cr-Nb alloys by means of the predictive models and a comparison to the available experimental data were done. The proposed methodology is a tool to assess the reliability of thermophysical properties data of multicomponent alloy systems.

Micelle formation of tetradecyltrimethylammonium X‐benzoate surfactants: Benzoate counterion substituent effects

AbstractTetradecyltrimethylammonium (TTA+) benzoate surfactants have a range of CMC values dependent on the substituent effects of the benzoate counterions. Twenty‐three TTA+/X‐benzoate CMC values were determined by conductivity and surface tension. The 12 TTA+/para‐ and meta‐benzoate and the unsubstituted benzoate CMC values yield a correlation to the hydrophobicity parameter (log P) of the benzoic acid, as the counterion. The logarithm of conductivity CMCs correlated to the log P value of the benzoic acid yields a slope of—0.4399. All 10 of the TTA+/ortho‐benzoate CMC values do not yield a correlation with hydrophobicity yet the TTA+/ortho‐halogenated benzoates give a strong correlation to hydrophobicity (log P). For this subset, the correlation was nearly identical to one of the TTA+/para‐ and meta‐benzoates. The slope of the logarithm of TTA+/ortho‐halogenated benzoate CMC values to the log P of benzoic acid is—0.413. Another subset is the TTA+/ortho‐hydrogen bond donating benzoates which clearly show micelle formation is favored in addition to the hydrophobic effect. The surface tension data CMCs yield a similar correlation to the conductivity data. This combined data yields further insight on the structural features of the counterion contribution to micelle formation. Specifically, the benzoates show both hydrophobicity effects and when ortho‐hydrogen bond donating substituents are present, micelle formation is strongly enhanced in addition to the hydrophobic effect of the anion.

Impact of critical point restriction on the calculation of surface tension of organic acids using group contribution models

This manuscript reports the calculation of surface tension of organic acids using new group contribution models. These models were obtained from the Jasper equation and the van der Waals principle of corresponding states. A special analysis was performed to determine the impact of incorporating the critical point restriction on the performance of tested group contribution models. This restriction was incorporated via a penalty term on the objective function used in the group contribution determination, and using the reduced temperature as the input model variable. A total of 885 experimental surface tension data points for 78 organic acids (including aliphatic, aromatic, dicarboxylic, and polyfunctional acids) were used to compare the performance of these group contribution models. The results showed that tested models calculated the surface tension of polyfunctional and aliphatic organic acids with modeling errors lower than 5%. However, the calculation of surface tension of aromatic and dicarboxylic acids was challenging for all tested models. The incorporation of critical point restriction of surface tension as a penalty term in the data processing stage did not improve the performance of tested group contribution models. Group contribution models that used the reduced temperature as an input variable showed the best performance for the calculation of the surface tension of these organic compounds.

Thermodynamic Insights of the Molecular Interactions of Dopamine (Neurotransmitter) with Anionic Surfactant in Non-Aqueous Media.

This study was aimed at establishing the interactions prevailing in an anionic surfactant, sodium dodecyl sulfate, and dopamine hydrochloride in an alcoholic (ethanol) media by using volumetric, conductometric, and tensiometric techniques. Various methods were utilized to estimate the critical micelle concentration (cmc) values at different temperatures. The entire methods yielded the same cmc values. The corresponding thermodynamic parameters viz. the standard free energy of micellization (Gmico), enthalpy of micellization (Hmico), and entropy of micellization (Smico) were predicted by applying the pseudo-phase separation model. The experimental density data at different temperatures (298.15 K, 303.15 K, 308.15 K, and 313.15 K) were utilized to estimate the apparent molar volumes (Vϕo) at an infinite dilution, apparent molar volumes (Vφcmc) at the critical micelle concentration, and apparent molar volumes (ΔVφm) upon micellization. Various micellar and interfacial parameters, for example, the surface excess concentration (Γmax), standard Gibbs free energy of adsorption at the interface (ΔGoad), and the minimum surface area per molecule (Amin), were appraised using the surface tension data. The results were used to interpret the intermolecular interactions prevailing in the mixed systems under the specified experimental conditions.

Tensiometric and Thermodynamic Study of Aliphatic and Aromatic Amine in Aqueous D-Glucose Solutions: A Comparative Study

The surface tensions of aqueous taurine (TAU) and tyramine (TYR) with D-glucose mixed solvents were elevated from 298.15 to 318.15 K by the KSV sigma 702 tensiometer. The purpose of the study was to elucidate comparative studies of the thermodynamic and transport aggregation properties of aliphatic and aromatic amine, i.e., taurine and tyramine, which provide information in pharmacology and biochemistry. The experimental data investigated by this study were utilized to evaluate various interfacial parameters, including surface pressure, surface excess concentration, and other thermodynamic parameters of surface assembly, which are discussed in terms of solute–solvent and solute–solute interactions. The surface tension data have been analyzed using the Gibbs adsorption isotherm. The results signify that the negative isotherm exhibited by the ionic solute, i.e., taurine, an aliphatic amine, is contrary to the positive isotherm of tyramine, a biogenic aromatic amine. Both the amines exhibit surface properties such as surfactant molecules, which is elucidated in terms of ionic–hydrophilic and hydrophobic–hydrophobic interactions. The positive entropy values state that the process of surface formation is favored by entropy gain as well as the enthalpy effect. The present system provides a better understanding of the intermolecular interactions, which are required for their usefulness in the field of nutrition, pharmacy, and the food industry.

An Investigation into the Mechanism of Alkaline Extraction-Isoelectric Point Precipitation (AE-IEP) of High-Thiol Plant Proteins

Hempseed protein isolate (HPI) has drawn significant attention as a promising source of plant-based protein due to its high nutritional value. The poor functionality (e.g., solubility and emulsifying properties) of HPI has impeded its food application for years. This study provides important new information on hempseed protein extraction, which may provide further insights into the extraction of other high-thiol-based plant proteins to make valuable plant-based products with improved functional properties. In this study, HPI was produced from hempseed meals using the AE-IEP method. The underlying mechanisms and extraction kinetics were investigated under different experimental conditions (pH 9.0–12.0, temperature 24–70 °C, and time 0–120 min). The results suggested that disulphide bond formation is an inevitable side reaction during hempseed protein extraction and that the protein yield and the free -SH content can be influenced by different extraction conditions. A high solution pH and temperature, and long extraction time result in increased protein yield but incur the formation of more intermolecular disulphide bonds, which might be the reason for the poor functionality of the HPI. For instance, it was particularly observable that the protein solubility of HPI products reduced when the extraction pH was increased. The emulsifying properties and surface tension data demonstrated that the functionality of the extracted hempseed protein was significantly reduced at longer extraction times. A response surface methodology (RSM) optimization model was used to determine the conditions that could maximise HPI functionality. However, a three-fold reduction in protein yield must be sacrificed to obtain the protein with this high functionality.

Cavitation Rheology of Model Yield Stress Fluids Based on Carbopol

Measuring the surface tension of yield stress fluids has remained a critical challenge due to limitations of the traditional tensiometry techniques. Here, we overcome those limits and successfully measure the surface tension and mechanical properties of a model yield stress fluid based on Carbopol gels via a needle-induced cavitation (NIC) technique. Our results indicate that the surface tension is approximately 70 ± 3 mN/m, and is independent of the rheology of yield stress fluid over a wide range of yield stress values σy = 0.5-120 Pa. In addition, we demonstrate that a Young modulus smaller than E < 1 kPa can be successfully measured for Carbopol gels with NIC method. Finally, we present a time-resolved flow structure around the cavity in a host of yield stress fluids, and assess the impact of fluid rheology on the detailed form of flow around the cavity. Interestingly, prior to the critical point associated with cavitation, the yield stress fluid is weakly deformed suggesting that the measured surface tension data reflect the near equilibrium values. Beyond the critical point, the yield stress fluid experiences a strong flow that is controlled by both the critical pressure and the non-Newtonian rheology of the yield stress fluid.

Interfacial and micellar synergistic interactions between a phosphonium surface active ionic liquid and TX-100 nonionic surfactant: Surface tension and 1H NMR investigations

The adsorption and self-aggregation behaviors of a mixed system made of a cationic surface active ionic liquid (SAIL), dodecyltriphenylphosphnium bromide (C12TPB), and a nonionic surfactant, polyoxyethylene p-tertoctylphenyl ether (TX-100), were investigated in aqueous solution using tensiometry and 1H NMR measurements. From the surface tension data, relevant physico-chemical parameters were determined for different proportions of the components: critical micelle concentration (cmc), surface saturation adsorption, minimum surface area per surfactant molecule and surface tension at the cmc. The obtained data were treated through different theoretical models, namely those of Clint, Rubingh, Maeda and Rosen, which allow the determination of key thermodynamic properties. The results revealed, in both the mixed micelles and surface monolayer, the existence of a non-ideal behavior due to rather strong attractive links, confirmed by the 1H NMR data analysis. They are attributed mainly, besides the hydrophobic interaction, to firstly the ion–dipole interaction and the complex formation between the polyoxyethylene head of TX-100 and the quaternary phosphonium group of C12TPB, and secondly to an intermolecular π-π stacking and a hydrogen-bonds formation between the protons in α position of the phosphonium and the oxygen atoms of polyoxyethylene units of TX-100, giving rise to a strong synergism.

Evidence for Ion Association at the Gas-Liquid Interface of the Mixture of 1-Butyl-3-methylimidazolium Hexafluorophosphate and Benzonitrile: A Sum Frequency Generation Spectroscopy and Surface Tension Study.

The gas-liquid interface for the mixtures of [BMIM][PF6] and benzonitrile is studied by sum frequency generation (SFG) spectroscopy and surface tension measurements as an important solute to reduce the viscosity of ionic liquids. Solvation of ionic compounds in bulk solvent is not necessarily the same as that at the surface due to the lower dielectric medium at the air/liquid interface. The results from the temperature-dependent SFG spectroscopy and surface tension study suggest that the ionic liquid in a benzonitrile solvent is associated as ion pairs at the surface rather than as dissociated─solvated─ions in the bulk solution. The influence of ionic liquids on the surface structure of benzonitrile is investigated from 0 to 1.0 mole fraction of benzonitrile. The CH stretching mode of vibration of benzonitrile in the SFG spectrum begins from a 0.2 mole fraction (x) of benzonitrile, and the intensity of the peak constantly increases on increasing the concentration of benzonitrile. However, the addition of benzonitrile does not result in extra peaks or shifting of the peak frequency to the spectra of [BMIM][PF6]. The surface tension measurements further support the presence of benzonitrile at the gas-liquid interface. The surface tension data of the mixture smoothly decrease as the benzonitrile concentration increases. The apparent tilt angle of the terminal methyl group of the cation of [BMIM][PF6] is calculated from SFG polarization spectra and shows an apparent lowering with the addition of benzonitrile. The effect of temperature on the surface structure of the binary mixture is also reported at four different temperatures between -15 and 40 °C for both the SFG spectroscopy and surface tension study. Benzonitrile shows different behavior in the mixture at higher temperatures than pure benzonitrile, as observed in the SFG spectra. In contrast, it does not show any CN peak in the mixture below 0.9 mole fraction. The temperature dependence of the interfacial tension is used to evaluate thermodynamic functions such as surface entropy and surface enthalpy. Both were found to be lowered with the increasing concentration of benzonitrile. Both spectroscopic and thermodynamic analyses indicate that the ionic liquid is highly associated as ion pairs and the benzonitrile is more ordered at the surface at concentration <0.4×.

Volumetric Properties, Molar Surface Gibbs Energy, and Its Application of Binary Systems Containing Ether-Group Functionalized Ionic Liquid with Monohydric Alcohols

Ether-group functionalized ionic liquid N-(2-methoxyethyl)-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide, [C1OC2pyrr][NTf2], was synthesized and characterized by 1H NMR, 13C NMR, and TGA. The density and surface tension of binary mixtures including [C1OC2pyrr][NTf2] and monohydric alcohols were measured over the entire range of mole fractions in different temperatures. Based on the experimental data of density and surface tension, the volumetric and surface properties of [C1OC2pyrr][NTf2] and its binary mixtures were obtained, and Vm, αp, and VE were explored. The effects of temperature and composition on these properties were investigated, and the excess molar volume of two binary mixtures was well fitted by the Redlick-Kister equation. The molar surface Gibbs energy (gs) of [C1OC2pyrr][NTf2] and its binary mixtures was calculated, and the traditional Eötvös equation was modified; moreover, all parameters had a clear physical meaning. Finally, based on gs, the surface tension of [C1OC2pyrr][NTf2] and its binary mixtures was estimated, and it is in good agreement with experimental values.

A fundamental model for calculating interfacial adsorption of complex ionic and nonionic PFAS mixtures in the presence of mixed salts.

Per- and polyfluoroalkyl substances (PFAS) are emerging contaminants that have been used extensively as firefighting agents and in a wide range of commercial applications around the world. As many of the most-common PFAS components are surfactants, they readily accumulate at interfaces, a process that can govern their environmental fate. There are thousands of PFAS compounds, and they have nearly always been used as mixtures, so it is common to find many different PFAS components present together in the environment. Furthermore, the interfacial behavior of ionic PFAS can be strongly influenced by the presence of salts, with adsorption dependent on both the composition and concentration of salts present. Any predictions of PFAS interfacial behavior made without considering both the mixed nature of PFAS present, as well as the composition of the salts present, have the potential to be off by orders of magnitude. To date, models capable of making predictions of PFAS interfacial adsorption when both mixed PFAS and mixed salts are present have not been presented. The work described here addresses this need by extending a mass-action model developed previously by the authors to allow predictions in cases where complex combinations of mixed PFAS and mixed salts are present. Predictions of PFAS interfacial affinity for a range of PFAS mixture conditions and ionic strengths are verified using experimentally-measured surface tension data. The new model provides physically-realistic prediction of interfacial adsorption of a wide range of PFAS mixtures over a wide range of salt concentrations and compositions. The model is capable of predicting interfacial adsorption of ionic/nonionic PFAS mixtures in the presence of salts, and can also make predictions when there is competitive adsorption between different PFAS components, a common case in PFAS source zones where high concentrations of multiple components are present and in foam fractionation reactors.

Surface tension models for binary aqueous solutions: a review and intercomparison.

The liquid-air surface tension of aqueous solutions is a fundamental quantity in multi-phase thermodynamics and fluid dynamics and thus relevant in many scientific and engineering fields. Various models have been proposed for its quantitative description. This Perspective gives an overview of the most popular models and their ability to reproduce experimental data of ten binary aqueous solutions of electrolytes and organic molecules chosen to be representative of different solute types. In addition, we propose a new model which reproduces sigmoidal curve shapes (Sigmoid model) to empirically fit experimental surface tension data. The surface tension of weakly surface-active substances is well reproduced by all models. In contrast, only few models successfully model the surface tension of aqueous solutions with strongly surface-active substances. For substances with a solubility limit, usually no experimental data is available for the surface tension of supersaturated solutions and the pure liquid solute. We discuss ways in which these can be estimated and emphasize the need for further research. The newly developed Sigmoid model best reproduces the surface tension of all tested solutions and can be recommended as a model for a broad range of binary mixtures and over the entire concentration range.

Surface tension of liquid Ti, V and their binary alloys measured by electromagnetic levitation

AbstractThe surface tension of the liquid Ti-V system is systematically measured using the oscillating drop technique during electromagnetic levitation. Temperature- and compositional dependence are both investigated. The entire compositional range is covered. A linear decrease with increasing temperature is found for the pure elements as well as for all investigated alloys. The surface tension generally increases with increasing V-content. The obtained data are in good agreement with the Butler model for the ideal solution. Additionally, the Butler model for the regular solution was evaluated in the context of the obtained surface tension data. In contrast to many other Ti-based alloys, the Butler model for the regular solution yields no additional benefit for Ti-V, since there is only a neglectable small deviation between the calculations for the ideal and regular solution. Segregation effects are modeled using the Butler equation for an ideal solution. The findings are discussed considering already existing trends for the mixing behavior of liquid Ti-alloys. The results strongly suggest, that the Ti-V system obeys in general the ideal solution law.