Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Surface mutually saturated liquids

If we consider the equilibrium of a lens floating on the surface of a mutually saturated liquid the following relationships evidently obtain... [Pg.97]

Antonow s rule is tlius only exact when the two mutually saturated liquids possess the same density. The observed values of cti2 should in general be slightly less than those determined from — In the case of oleic acid floating on water Devaux obtained a lens thickness of OT cm. Since p — 0 90 the interfacial surface tension should be O M dyne less than the value obtained with the aid of Antonow s rule. [Pg.98]

Table I. Surface and Interfacial Tensions (dynes/cm) of Mutually Saturated Liquids... Table I. Surface and Interfacial Tensions (dynes/cm) of Mutually Saturated Liquids...
The derivative of the surface tension with respect to temperature at the interface between condensed phases in binary systems can be either positive, or negative, or even change its sign when the temperature changes, which makes it different from the vapor-liquid interface in a one-component system. Within a certain approximation one may assume that in binary systems, as in single-component ones, the value r = -do/dT is the excess of entropy within the discontinuity surface. Consequently, for the interface between condensed phases, the excess of entropy can not only be positive (as it was with singlecomponent systems), but also negative. This situation is especially typical for the interface between two mutually saturated liquid solutions. [Pg.167]

If we have E >0 and S = 0, then a drop of oil on the surface of a liquid will in principle be spread over that surface to form a duplex flhn at equilibrium (obeying Antonow s rule [20]). In contradiction Harkins [18] has claimed that 5 < 0 always prevails at equilibrium even if the initial spreading coefficient 5 > 0. However, Rowlinson and Widom [19] emphasize convincingly that. S = 0 is allowed so that stable duplex films can often be found between mutually saturated liquids at equilibrium. [Pg.61]

A complication now arises. The surface tensions of A and B in Eq. IV-2 are those for the pure liquids. However, when two substances are in contact, they will become mutually saturated, so that 7a will change to 7a(B) and 7b to 7B(A). That is, the convention will be used that a given phase is saturated with respect to that substance or phase whose symbol follows in parentheses. The corresponding spreading coefficient is then written 5b(A)/a(B)-... [Pg.105]

The possibility of determination of the difference of surface potentials of solvents, see Scheme 18, among others, has been used for the investigation of Ajx between mutually saturated water and organic solvent namely nitrobenzene [57,58], nitroethane and 1,2-dichloroethane (DCE) [59], and isobutyl methyl ketone (IB) [69]. The results show a very strong influence of the added organic solvent on the surface potential of water, while the presence of water in the nonaqueous phase has practically no effect on its x potential. The information resulting from the surface potential measurements may also be used in the analysis of the interfacial structure of liquid-liquid interfaces and their dipole and zero-charge potentials [3,15,22]. [Pg.35]

Spreading (Eq. (iii) of Fig. A.4.4) occurs when the oil adheres to the water more strongly than it coheres to itself this is generally the case when a liquid of low surface tension is placed on one of high surface tension. This mineral oil spreads on water, but water cannot spread on this oil. The initial spreading coefficient does not consider that the two liquids will, after contact, become mutually saturated. The addition of surfactants which lower yow and ysw (cf. Fig. A.4.3) cause the dispersion of the oil into droplets. [Pg.147]

Some interesting conclusions may be drawn from a consideration of the magnitude of the interfacial surface tensions of various liquids. The significance of these was first pointed out by Hardy Froc. Roy. Soc. A, Lxxxviii. 303, 1913) and emphasised by Harkins J.A.G.S. XXXVIII. 228,1916 xlil 700,1920). We have noted that Antonow s rule only applies to mutually saturated solutions. If two... [Pg.102]

For thermodynamic treatment of surface phenomena, the thickness of the boundary regions can often be ignored or their effect eliminated by selection of a convenient location for the interface IGL. The liquid—liquid interface, ILL (Fig. lb) is similarly associated with interfacial regions, RA and RB, which can be treated like the gas—liquid interface in most analyses. Because few liquids are completely immiscible, mutual saturation is taken as the equilibrium condition. [Pg.234]

Energy of Adhesion. The interfacial energy between two mutually insoluble saturated liquids, A and B, is equal to the difference in the separately measured surface energies of each phase ... [Pg.234]

Hence, in the case of two liquids whose surface and interfacial tensions are such that one will spread on the other, before they are mutually saturated, it is to... [Pg.214]

If (5) is combined with Dupr6 s equation (Chap. I (2)), we see that WAB = 2y i.e. the work of adhesion for two liquids mutually saturated with each other is equal to the work of cohesion of the liquid of lower surface tension, after saturation with that of higher tension. This must mean that the surface of B> after saturation, becomes very similar to that of A as regards external field of force— not necessarily identical as regards molecular composition. [Pg.215]

Rapid spreading is often observed when a liquid with low surface tension is introduced on a liquid with high surface tension. After a certain time in the course of mutual saturation of liquids A and B, the systems approach equilibrium and the positive initial spreading coefficient becomes 0 or negative. So, at se < 0, the excess of liquid B accumulates in a lens. The typical form of the lens is given in Fig. 3.117. At equilibrium this form has been studied in a number of works [e.g. 204]... [Pg.312]

The relations between the surface tensions and interfacial tension given in 9.VIII G apply strictly only to immiscible liquids when the liquids are partly miscible, the surface tensions change. For this case Antonoff proposed a rule which is generally understood (but perhaps not correctly) to mean that the interfacial tension between the two saturated liquid layers is equal, or very approximately equal, to the difference between the surface tensions of the two [mutually saturated] phases or solutions [against their common vapour] ... [Pg.170]

In appendix 1 examples of liquid-vapour surface tensions and of liquid-liquid interfacial tensions are given. From this tabulation spreading tensions can be computed. As a rule, a liquid of low surface tension spreads over a liquid of high surface tension. For instance, from the tabulated vcdues it follows that at 293 K benzene initially spreads over water, because (= 72.8 - 28.9 - 35.0) > 0 mN m L However, benzene and water are not completely immiscible after some time there will be mutual saturation. As the surface tension of water saturated with benzene equals 62.2 mN m cind that of benzene saturated with water 28.8 mN m , the corresponding value for < 0. This explains why a drop of pure benzene,... [Pg.213]

Figure 5.5 Vectorial equilibrium of the lens of liquid (1) on the surface of a sub-phase liquid (2). In equilibrium, (1) and (2) must be mutually saturated in each other and hence the surface and interfacial tensions will not necessarily be those of pure liquids. Figure 5.5 Vectorial equilibrium of the lens of liquid (1) on the surface of a sub-phase liquid (2). In equilibrium, (1) and (2) must be mutually saturated in each other and hence the surface and interfacial tensions will not necessarily be those of pure liquids.
If there is not enough space for all of the liquid (1) to spread fully, it spreads as a polylayer or a relatively thick him on the surface of the sub-phase liquid (2), where the corresponding liquid surface tensions, and Yi retain their bulk values and the interfacial tension of the mutually saturated solutions, y12, can be measured experimentally. [Pg.194]

The term adhesion is used if the interaction occurs between different types of molecule, and the work of adhesion, W 2 is dehned as the reversible work, per unit area, required to separate a column of two different liquids at the interface (or to separate a liquid from an underlying liquid), creating two new equilibrium surfaces of two pure materials, and separating them to inhnite distance. However, the derivation of Wis different from that of WJ because of the presence of equilibrium interfacial tension of the mutually saturated solutions, y12. Since two new surfaces (1) and (2) are formed, and the interfacial area (12) disappears during the separation process of two different liquids, then the work of adhesion can be formulated as given by Dupre... [Pg.194]

At temperatures above 97.5°, a mixture of sodium metal and a saturated hydrocarbon constitutes a binary system of mutually insoluble liquids that can be emulsified in much the same manner as oil and water. When this sodium-in-oil emulsion is permitted to cool below this temperature, the sodium solidifies as microscopic spheres suspended in the hydrocarbon. Addition of certain surface-active agents1 such as oleic acid, prior to cooling, assists in keeping the sodium in suspension. Such a formulation is known as a sodium dispersion. [Pg.6]

It is important to realize that for two mutually soluble liquids the values of a, and o2 correspond to the surface tensions of their saturated solutions. The latter is especially important for polar liquids, as the surface tension can be significantly lowered by the dissolution of a less polar (and, therefore, surface... [Pg.174]

Assume (i) that the temperature is 20 C and that the phase volume = 0.40. (ii) that the surface tension between two immiscible liquids that are mutually saturated with each other can be estimated from the relationship of Good and Girifalco (J. Phys. Chem., 64,561,1960). [Pg.315]

A related subject is the interfacial potential between water (W) and the liquid S, where the latter could be either miscible or immiscible with water. In the first case the individual surface potentials between W and air (A), Ax, and between S and air, A X, are measured or estimated and the difference is taken A x = A x - A x. In the latter case direct measurements of the interfacial potential (at zero charge) between the mutually saturated W(S) and S(W) are possible. Koczorowski et al. (1989) presented values for many liquids S of both kinds, and these are compared with values for some water-miscible liquids obtained by other authors in Table 4.2. It should be noted that for the mutually immiscible pair water/nitrobenzene the interfacial potential, 0.105 0.20 V (Koczorowski and Zagorska 1983), is considerable lower than that estimated for the neat liquids, 0.24 V. [Pg.148]

The aim of this chapter is to provide a short review covering the present state of research and knowledge, as well as the problems concerning electrochemistry of liquid interfaces at equihbrium. These systems are best described by mutually related chemical parameters, such as ion transfer energy, A%Gi, and electrical parameters, such as Galvani and Volta potentials, A cp and A%,xp, where s and w refer to the system consisting of organic and aqueous phases mutually saturated. It is well known that both these potentials can be correlated with the difference of surface potentials of the s... [Pg.78]

It must be emphasized that Yi Y2 Equations (2,3,4 and 8), are the surface tensions of the pure liquids, not the mutually saturated solutions. Physically, this is a consequence of assuming that, in a binary liquid-liquid system, there is not any appreciable surface excess of either component at the interface. This is reasonable for a binary system but in a ternary system, it is not permissible to make any such assumption c.f. Melrose ... [Pg.114]

Here yj is the specific surface free energy of liquid A, 7g that of liquid B and 7 5 the specific interfacial free energy of the contact surface. The quantity S, defined as 7g — 7 "TaB known as the spreading tension or spreading coefficient. In practice, liquid A will, in time, become saturated with liquid B, even though they do not mix, and a distinction should be made between the initial spreading tension and the equilibrium value when the liquids are mutually saturated. [Pg.181]


See other pages where Surface mutually saturated liquids is mentioned: [Pg.177]    [Pg.7]    [Pg.632]    [Pg.99]    [Pg.189]    [Pg.214]    [Pg.215]    [Pg.213]    [Pg.575]    [Pg.196]    [Pg.241]    [Pg.106]    [Pg.100]    [Pg.59]    [Pg.167]    [Pg.173]    [Pg.264]    [Pg.714]   
See also in sourсe #XX -- [ Pg.143 ]




SEARCH



Liquid surface

Liquidous surface

Liquids saturated

Mutual

Mutualism

Mutuality

© 2024 chempedia.info