This book gives a practical account of the modern theory of calculation of absorbers for binary and multicomponent physical absorption and absorption with simultaneous chemical reaction. The book consists of two parts: the theory of absorption and the calculation of absorbers. Part I covers basic knowledge on diffusion and the theory of mass transfer in binary and multicomponent systems. Significant stress is laid on diffusion theory because this forms the basis for the absorption process. In the next chapters the fundamentals of simultaneous mass transfer and chemical reaction, the theory of the desorption of gases from liquids and the formulation of differential mass balances are discussed. Part II is devoted to the calculation of absorbers and the classification of absorbers. The chapters present calculation methods for the basic types of absorber with a detailed analysis of the calculation methods for packed, plate and bubble columns. The authors illustrate the presented material with a large number of examples, starting with simple ones for binary systems and ending with column calculation for multicomponent systems.