Lateral Forces Between Particles at a Fluid Interface

Capillary forces can be calculated as described above once the curvature of the liquid interface and thus its shape is known. Since interfacial tensions between two liquid phases are usually lower than typical liquid-vapor interfacial tensions, the Kelvin length = Yab i longer and the capillary force can be more long range [583]. 

Force measurements can even be used to measure very low interfacial tensions [584], which are difficult to measure with conventional techniques. 

Lateral Forces Between Particles at a Fluid Interface 

Lateral forces between particles floating at a fluid interface or immersed in a thin liquid film are observed and utilized in some extraction and separation flotation processes [591]. They are important in stabilizing emulsions and foams, for making porous materials from emulsions and foams [593, 594], and for preparing colloidal crystals [595, 596]. The presence of lateral capillary forces has 

Two similar particles always attract each other. This attraction appears because the liquid meniscus deforms in such a way that the gravitational potential energy of the two particles decreases as they approach each other. In terms of forces, thqr attract each other because the horizontal component of the surface tensional force is stronger in the direction toward the neighboring particles than in the opposite direction. 

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