in the presence of other immiscible fluids.
The concept of wettability is illustrated in Figure 4-1. Small drops of three liq- uids—mercury, oil, and water—are placed on a clean glass plate.
The three droplets are then observed from one side as illustrated in Figure 4-1. It is noted that the mercury retains a spherical shape, the oil droplet devel- ops an approximately hemispherical shape, but the water tends to spread over the glass surface.