Measurement of liquid viscosities in tapered or parabolic capillaries

The possibility of using tapered or parabolic capillaries for measurement o f liquid viscosities is investigated both experimentally and theoretically. It is demonstrated that even small deviations in capillary radius from a c onstant value may substantially affect measurement results. Equations are d erived which allow correct analysis of the measurement results in tapered o r parabolic capillaries. The following cases are analyzed: a water imbibiti on into a tapered or parabolic capillary and displacement of one liquid by another immiscible liquid in tapered or parabolic capillaries, Two possibil ities are considered: (a) the narrow end of the capillary as capillary inle t and (b) the wide end of the capillary as capillary inlet. (C) 1999 Academ ic Press.