protein, which adsorbs onto the W–O interface, thereby giving rise to a
surface charge and thus to a surface potentialc 0. The oil has a relative
dielectric constant of about 3; ionic species can virtually not dissolve in oil,
henceI&0 and 1=k!?. Thus there is no electric double layer, and the
electrostatic repulsion is almost purelyCoulombic, which acts over far
FIGURE12.3 Overlap of the electrical double layers between two particles at a
distancehfrom each other. In (a) the double layers virtually do not overlap, and the
electrostatic potentialscequal zero in the middle; in (b) the particles are closer and
their electrical double layers do overlap, which causes the potentials to locally
increase. Highly schematic.