Kinetics of liquid/liquid capillary rise

The classical capillary rise experiment is performed for the first time with liquid/liquid systems. The lower (advancing) liquids are glycerol-water solutions of various compositions, while the upper (displaced) liquids are pure hydrocarbons ranging from light to polymeric; viscosity ratios span 0.4 to 232 for 13 different liquid pairs. Capillaries are glass, of radius 0.10 and 0.05 cm, and are pretreated in three different ways to produce surfaces that are dry, prewet, or prewet-dried. The meniscus position, h, is tracked by cathetometer and movie film, from the moment of tube entry until motion stops at h∞. Results are shown for representative systems, in terms of kinetic rise curves, h(t). These are nearly independent of the upper nonwetting fluid viscosity but sensitive to the lower wetting fluid viscosity. Rise is much faster in prewet tubes than in dry and prewet-dried tubes. Photos of menisci show asymmetric "sidling" motions in many cases, and even well-behaved prewet systems display nonconstant meniscus shapes. Data are analyzed in terms of both the dynamic contact angle and a new concept of excess force.