Surface tension for liquids

Is It Possible to Measure Surface Tension of Solid Metal and Solution Interfaces In contrast to measurement of surface tension for liquids, the direct measurement of surface tension for solids can be considered an impossible task. However, it is possible to apply indirect measurements to obtain electrocapillary curves of solid electrodes and therefore the information from these curves. 

The quantity y is usually called the surface tension for liquid-gas interfaces and the interfacial tension for liquid-liquid interfaces. We see from Equation (13.2) that y da is the differential quantity of work that must be done reversibly on the system to increase the area of the system by the differential amount da at constant entropy, volume, and mole numbers. 

This table summarizes the best available values of the density, specific heat capacity at constant pressure (Cp, vapor pressure, viscosity, thermal conductivity, dielectric constant, and surface tension for liquid water in the range 0 — 100 °C. All values (except vapor pressure) refer to a pressure of 100 kPa (1 bar). The temperature scale is IPTS-68. 

The form of tensor L is determined by the nanoparticle shape (e.g. spherical, ellipsoidal or cylindrical) and mechanical boundary conditions. It should be noted that surface stress tensor components depend on the chemical properties of the nanoparticle ambient material and the presence of oxide interface layer [6]. In the case of chemically clean surface under the thermodynamic equilibrium with environment the diagonal components have to be positive like the surface tension for liquids, although in general case may have both positive and negative sign. 

Using the surface tension for liquid nitrogen (see footnote 14), the maximum stress arising in a pore with a diameter of 10 mn is 3.5 MPa. This value has to be compared to the... 

With this relationship, the surface tension of a liquid can be evaluated by measuring the height of the liquid level inside the capillary. The book of Adamson (see the bibliography at the end of this chapter) gives an overview of the experimental methods used to measure surface tension for liquids and solids. 

Eq. IV-9 would use the surface tensions that liquids A and B would have if their inter-molecular potentials contained only the same kinds of interactions as those involved between A and B (see Refs. 20, 22-24). For the hydrocarbon-water system, Fowkes [20] assumed that Uh arose solely from dispersion interactions leaving... 

Because of the large surface tension of liquid mercury, extremely large supersaturation ratios are needed for nucleation to occur at a measurable rate. Calculate rc and ric at 400 K assuming that the critical supersaturation is x = 40,000. Take the surface tension of mercury to be 486.5 ergs/cm. ... 

Surface Protection. The surface properties of fluorosihcones have been studied over a number of years. The CF group has the lowest known intermolecular force of polymer substituents. A study (6) of liquid and solid forms of fluorosihcones has included a comparison to fluorocarbon polymers. The low surface tensions for poly(3,3,3-trifluoropropyl)methylsiloxane and poly(3,3,4,4,5,5,6,6,6-nonafluorohexyl)methylsiloxane both resemble some of the lowest tensions for fluorocarbon polymers, eg, polytetrafluoroethylene. 

Surface tension for most liquids can be estimated for temperatures other than the ones given in the literature (usually 15 or 20°C) by using the following equation ... 

Surface tension of liquid Coalescence for removal Tabulated... 

Fig. 10. A schemalic Zisman plot for a given solid specimen. When the cosine of the static advancing contact angle is plotted against the surface tension for a series of apolar liquids against a test solid, a straight line results. Its extrapolation to cost = 1 yields the critical surface tension of the solid.

Liquid surface tension is calculated using the Sugden Parachor method [242]. Neglecting vapor density, surface tension for the liquid mixture is ... 

For Yiv > YPv> where y v and Ypv are the surface tensions of liquid and protein, respectively, AFads increases with increasing ysv, predicting decreasing polymer adsorption. An example of this is phosphate buffer saline where y]v = 72.9 mJ/m2 and Ypv is usually between 65 and 70mJ/m2 for most proteins [5]. Therefore, supports for gel-permeation and affinity chromatography should be as hydrophilic as possible in order to minimize undesirable adsorption effects. 

On the meniscus surface the deviation of vapor pressure from the saturation pressure Psat depends on the surface tension a, liquid density p( gas constant R, temperature T, and radii of curvature r. When p( > -Psat(T) < (2[Pg.354]

Water forms hydrogen-bonded clusters with itself and with other proton donors or acceptors. Hydrogen bonds account for the surface tension, viscosity, liquid state at room temperature, and solvent power of water. 

Here, is the average effective radius of pore, is surface tension between liquid and vapor, 0 is the contact angle, rj is the dynamic viscosity of the electrolyte, and h is the height elevation of the electrolyte within pore at time r. In the experiment, the amount of electrol he wetted within the anode electrode, m, expressed as h = m/pAP, was measured instead of the height, h. Integrated Eq. (l)for t becomes Eq. (2). 

FHH (Frenkel-Halsey-Hill) theory is valid for multi molecules adsorption model of the flat surfrtce material. When this model is applied for the surface fractal in the range of capillary condensation, in other words, in the state of interface which was controlled by the surface tension between liquid and gas, the modified FHH equation can be expressed as Eq. (3). 

We shall illustrate the applicability of the GvdW(S) functional above by considering the case of gas-liquid surface tension for the Lennard-Jones fluid. This will also introduce the variational principle by which equilibrium properties are most efficiently found in a density functional theory. Suppose we assume the profile to be of step function shape, i.e., changing abruptly from liquid to gas density at a plane. In this case the binding energy integrals in Ey can be done analytically and we get for the surface tension [9]... 

It is usually difficult to find experimental values for surface tension for any but the more commonly used liquids. A useful compilation of experimental values is that by Jasper (1972), which covers over 2000 pure liquids. Othmer et al. (1968) give a nomograph covering about 100 compounds. 

TABLE III. SURFACE TENSIONS OF LIQUIDS USED FOR SOLID SURFACE CHARACTERIZATION... 

What characterizes surfactants is their ability to adsorb onto surfaces and to modify the surface properties. At the gas/liquid interface this leads to a reduction in surface tension. Fig. 4.1 shows the dependence of surface tension on the concentration for different surfactant types [39]. It is obvious from this figure that the nonionic surfactants have a lower surface tension for the same alkyl chain length and concentration than the ionic surfactants. The second effect which can be seen from Fig. 4.1 is the discontinuity of the surface tension-concentration curves with a constant value for the surface tension above this point. The breakpoint of the curves can be correlated to the critical micelle concentration (cmc) above which the formation of micellar aggregates can be observed in the bulk phase. These micelles are characteristic for the ability of surfactants to solubilize hydrophobic substances in aqueous solution. So the concentration of surfactant in the washing liquor has at least to be right above the cmc. 

Periodic variations in the surface tension of liquid metals, c1 , are shown in Figure 6.5. The much higher surface tension of rf-block metals compared to the s- and p-block metals suggests that the surface tension relates to the strength of interatomic bonding. Similar periodic trends can be found also for the melting temperature and the enthalpy of vaporization, and the surface tension of liquid metals is strongly... 

In the body of a liquid, intermolecular forces pull the molecules in all directions. At the surface of the liquid, the molecules pull down into the body of the liquid and from the sides. There are no molecules above the surface to pull in that direction. The effect of this unequal attraction is that the liquid tries to minimize its surface area. The minimum surface area for a given quantity of matter is a sphere. In a large pool of liquid, where sphere formation is not possible, the surface behaves as if it had a thin stretched elastic membrane or skin over it. The surface tension is the resistance of a liquid to an increase in its surface area. It requires force to break the attractive forces at the surface. The greater the intermolecular force, the greater the surface tension. Polar liquids, especially those that utilize hydrogen bonding, have a much higher surface tension than nonpolar liquids. 

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