. Contributions from the Botanical Laboratory, vol. 12. Botany; Botany. 6l2 AMERICAN JOURNAL OF BOTANY [Vol. 22. June, i93Sl MOVER LATEX 613 behavior of colloidal particles. Let us consider a solid spherical particle, 5 (fig 2), at an interface between an organic phase, 0, and an aqueous phase W The line of contact of the sphere with the interface will be a circle 'in a plane normal to the plane of the paper. Let P be a point on this line of contact and let 9 be the angle of contact between 5 and the interface, with origin at P. From the point P there arise three separating surfaces OW, the oi
. Contributions from the Botanical Laboratory, vol. 12. Botany; Botany. 6l2 AMERICAN JOURNAL OF BOTANY [Vol. 22. June, i93Sl MOVER LATEX 613 behavior of colloidal particles. Let us consider a solid spherical particle, 5 (fig 2), at an interface between an organic phase, 0, and an aqueous phase W The line of contact of the sphere with the interface will be a circle 'in a plane normal to the plane of the paper. Let P be a point on this line of contact and let 9 be the angle of contact between 5 and the interface, with origin at P. From the point P there arise three separating surfaces OW, the oil-water interface, SO, the solid-oil interface, and SW, the solid-water interface. Each surface is the seat of free interfacial energy. For each of these free energy values there may be substituted a tension Organic Phase. Aqueous Phase Fig. 2. Tensional relationships arising in the interfaces between a particle and an organic and aqueous phase. After Mudd and Mudd (1931). equal to it in magnitude and parallel to the surface—the interfacial tension (Adam, 1930). Let the corresponding tensions in the surfaces meeting at P be Tow, Tso, and Tsw. At equilibrium, Tso = Tsw + Tow . cos 0. If, however, Tsw > Tso + Tow, the line of contact will be dragged toward the aqueous side until the particle lies completely in the oil. Likewise, if Tso > Tsw + Tow, the line of contact will be displaced toward the organic phase until the particle is enveloped by water. For equilibrium in the interface it is necessary that Tso < Tsw + Tow and Tsw relative to Tso; in other words, the solid exhibits marked preferential wetting by the water. This strongly indicates a hydrated surface. Mudd, Nugent, and Bullock (1932) point out that "the greater the state of hydration of a given surface, the more the surface resembles the aqueous dispersion medium and presumably the less the free interfacial ; As Harkins (1925) remarks, ''The greatest of all solubility rules is that like dis
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