This document discusses methods for obtaining the overall mass transfer coefficient in packed columns. It presents experimental data for oxygen-water systems using ceramic rings of different diameters. For 1/2 inch rings, the height of transfer coefficient is proportional to the liquid mass velocity to the power of 0.4. For larger rings, it is proportional to liquid mass velocity to the power of 0.2. The relationship between height of transfer coefficient and liquid mass velocity changes with ring diameter. The document also provides equations that can be used to calculate the liquid film resistance for other systems based on differences in diffusivity and viscosity.