Methods in Immunology: Volume II, Physical and Chemical Methods is a collection of papers dealing with electrophoresis, analytical ultracentrifugation, dialysis, ultrafiltration, cellulose ion exchangers, and chromatographic separation of macromolecules on porous gels. Some papers explain the applications of radioisotopes, optical analysis, and chemical analysis of proteins, carbohydrates, lipids, and nucleic acid. One paper describes the theory of electro-migration. Factors such as electrical charge or frictional coefficients govern the rate of migration of charged particles in an electric field. The differences found in their velocities can be used to separate substances or analyze them. Mobility is a characteristic property of molecules and can also be influenced by the composition of the medium or solution. Dialysis separates solvents too large to diffuse through a barrier from smaller solutes; ultrafiltration (reverse osmosis) forces solvent and solutes up to a certain critical size through the barrier by a high pressure on one side. The book notes that the membrane never becomes plugged in dialysis because of some opposite movement of the solvent. Another paper points out that the significance of radioactive tracers in immunochemistry employed to identify and label macromolecules functioning as antigens and antibodies. The collection can prove valuable to bio-chemists, cellular biologists, micro-biologists, developmental biologists, and scientists involved in immunological research.