In batch gas absorption, a soluble vapor is absorbed from a mixture by means of a liquid in which the gas is more or less soluble. Unlike distillation, absorption is based on different solubility of the components in liquid and not based on boiling point difference. Absorption followed by reaction in the liquid phase is often used to get more complete removal of a solute from a gas mixture. Although, most of the absorption columns are operated continuously, batch absorption is important in the measurement of reaction rate constants and mass transfer coefficients. These absorption equipment are often carried out in a tank where gas bubbles are dispersed in the liquid phase as shown in Figure 6.1.