AbstractA theoretical study of the countercurrent flow of a dispersed phase in a continuous phase resulted in the following equation relating holdup X to the flow rates of the two phases.\documentclass{article}\pagestyle{empty}\begin{document}$$ A\left({\frac{{U_C}}{{U_D}}} \right)^{2 - n} \left({\frac{X}{{1 - X}}} \right)^3 + B = \frac{{X^3}}{{U_D ^{2 - n}}} $$\end{document}For packed towers this equation has been used in the following form:\documentclass{article}\pagestyle{empty}\begin{document}$$ \frac{{X^3}}{{U_D ^{1.5}}} = A'\frac{{U_C ^r}}{{U_D ^{1.5}}}\left({\frac{X}{{1 - X}}} \right)^3 + B' $$\end{document}Values ofA', B', andrfor three liquid pairs, and two packing types are reported, using new holdup data determined in this research.Graphical correlations are shown and values ofrare reported for some of the data of Gayler and Pratt.For spray towers the equation suggested a correlation of\documentclass{article}\pagestyle{empty}\begin{document}$ \frac{{X^3}}{{U_D ^{1.8}}} $\end{document}against the group\documentclass{article}\pagestyle{empty}\begin{document}$ \frac{{U_C ^{0.2}}}{{U_D ^{1.8}}}\left({\frac{X}{{1 - X}}} \right)^3 $\end{document}This has been tested using data previously published by one of the authors.