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Surface force nonwetting liquid

An alternate derivation of the Washburn equation can be pursued as follows. For a pore of circular cross-section with radius r the surface tension acts to force a nonwetting liquid out of the pore. The force developed due to interfacial tensions is the product of the surface tension y of the liquid and the circumference (2nr) of the pore, that is. [Pg.95]

Mercury is a nonwetting liquid that must be forced to enter a pore by application of external pressure. The surface tension of mercury causes mercury to bridge the openings of pores, cracks, and crevices until sufficient pressure is applied to force entry. For example, at atmospheric pressure, mercury will resist entering... [Pg.113]

Adhesion of gas bubbles to solid particles. In the hydrometallurgical process, flotation, gas bubbles are attached to ore particles and carry them to the surface of the liquid phase. The attraction force is adhesion of circular line elements at the contact of a nonwetted solid phase (ore), liquid phase (aqueous solutions of flotation agents), and gas phase (air or hydrogen bubble). This system is presented in Figure 1.17. [Pg.12]

Strictly speaking, the force is the molecular adhesive force in an atmosphere of saturated vapor. However, because the adsorption of vapors of a nonwetting liquid on solid surfaces is insignificant and does not influence adhesion between particles, one can nearly always assume that the value of the force Pss is ih same as that in air. [Pg.19]

It is thus evident that, within a first approximation. Equation 1.30 is valid for both wetting and nonwetting liquids, with a meniscus either present or absent. It is, however, worth pointing out that for macroscopic particles, this is valid only in the case of molecularly smooth surfaces. In this case, the equations for the molecular adhesive forces and for the capillary contraction force both contain the same macroscopic value of R. The situation is different for rough surfaces. Namely, the value of R in the expression for the molecular forces may be determined by the radii of microheterogeneities between which the contact is formed, while the value of R in the expression for the capillary adhesion force may be determined by the macroscopic radii of the particles. Consequently, particles with a microscopically... [Pg.23]

Coating a solid surface with a liquid film presents difficulties when 5 < 0 (partial and nonwetting conditions) and a thin film is desired, it will be necessary to force the liquid to spread and eventually, to avoid the subsequent retraction of the film. The ptecise meaning of thin film will be explained in Sec. 3.2. [Pg.211]

When a liquid is placed on a solid surface, either it will spread and wet that surface (Fig. 10.22fl) or it will bead up (Fig. 10.22ft). The degree of wetting and whether a system is wetting or nonwetting are quantified by the equilibrium contact angle 9 that forms between the liquid and the solid and is defined in Fig. Q.22a and ft. A simple balance of forces indicates that at equilibrium... [Pg.338]

The difference between the partial and the nonwetting situations will become clearer when discussing capillary effects. Fot now, we will just mention that the names are associated with what happens when a capillary or a porous material (the soUd surface) is placed in contact with the liquid. In total and partially wetting cases, the liquid will spontaneously penettate into the material while in the nonwetting situation the liquid will not penettate without an external force. [Pg.187]


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