123 phase and hence have no direct bearing on the retention time of solutes. However in gas-solid chromatography, a considerable quantity of the mobile phase may be adsorbed on the surface of the stationary adsorbent which diminishes the column's effective length and ability to retain solutes. In this respect helium has been found to be preferable to most other gases (GREENE and Roy, 1957) because it is adsorbed to the least extent. 3. Packed columns offer a considerable resistance to flow, which may create a pressure differential between inlet and outlet of sufficient magnitude to cause an unfavorable flow rate through a significant length of the column. A reduced inlet/outlet pressure ratio can be obtained by using light molecular weight gases toward which the column packing shows the greatest permeability. The flow rate of the mobile phase is normally adjusted by altering the column inlet pressure, for which purpose commercial pressure regulators of sufficient accuracy are available. Quantitative measurements of the flow rate can be made by a number of methods, including rotameters, orifice meters, soapfilm flow meters and displacement of water. The former two methods are the most con venient but the least accurate; moreover they create a back pressure and are temperature dependent whereas although the moving soap bubble is cumbersome to employ and unusable for continuous readings, it is preferred when the highest accuracy is required.

Inhalt
Contents.- Emission and Atomic Absorption Spectrochemical Methods..- A. Flame Emission Methods.- B. Arc Emission Analysis.- C. Spark Emission Methods.- D. Atomic Absorption Methods.- References.- Mass Spectrometric Methods..- A. Instrumentation.- B. The Sample.- C. Origin of Mass Spectra and their Interpretation.- D. Specific Applications.- Appendix I.- References.- Plant Spectra: Absorption and Action..- A. Instrumentation.- B. Light Scatter Phenomena.- C. Absorption Spectra.- D. Action Spectra.- E. Fluorescence Excitation Spectra.- References.- Gefriertrocknung..- A. Die biologischen Probleme der Gefriertrocknung.- B. Die Vakuum-Sublimation.- C. Anwendungen.- D. Verwandte Methoden.- Vapour Phase Chromatography..- A. Theoretical Approach.- B. Apparatus Requirements.- C. Techniques.- D. Applications.- E. Conclusion.- References.- Ion-Exchange Chromatography..- A. Ion-Exchange Materials.- B. Theory of Chromatographic Procedures.- C. Apparatus.- D. Experimental Procedures.- E. Some Applications of Ion-Exchange Chromatography.- F. Ion-Exclusion.- G. Mechanism of Adsorption of Solutes on Ion-Exchange Resins.- H. Applicability of Ion-Exchange Chromatography.- References.- Table 1. Chromatographie grade resins and celluloses.- Molecular Sieving other than Dialysis..- A. Ion-Exchange Materials as Ionic Sieves.- B. Molecular Sieving on Starch.- C. Dextran Gels as Molecular Sieves.- References.- Dünnschicht-Chromatographie..- A. Methode und Geräte.- B. Spezielle Arbeitstechniken.- C. Anwendungsbereich und Einsatzmöglichkeiten.- D. Anwendungsbeispiele.- Literatur.- Paper Chromatography on a Preparative Scale..- A. General.- B. Multisheet- and Cardboard-Chromatography.- C. Separation on Paper-Packs.- D. Column Chromatography.- E. Continous Paper Chromatography.- F.Accelerated Chromatography.- References.- Determination of Size, Shape and Homogeneity of Macromolecules in Solution..- A. Average Molecular Weights.- B. Osmotic Pressure.- C. Light Scattering.- D. Diffusion.- E. Ultracentrifugation.- F. Viscosity.- G. Particle Shape from Hydrodynamic Measurements.- Sectional References.- Optical Rotatory Dispersion. Its Application to Protein Conformation..- A. Mean Residue Rotation of Polypeptides and Proteins.- B. Optical Rotatory Dispersion Drude Equation.- C. Rotatory Properties of Synthetic Polypeptides.- D. Optical Rotatory Properties of Proteins.- E. Temperature Dependence of Optical Rotation.- F. Measurement of Optical Rotation.- G. Treatment of Data.- References.- Diffuse Röntgenkleinwinkelstreuung..- A. Theorie.- B. Experimentelle Methodik.- C. Anwendungsbeispiele.- Literatur.- Méthodes Calorimétriques pour l';Analyse des Végétaux..- I. Appareillage.- II. Thermogenèse de Germinations.- III. Gradients de Thermogénèse dans les Organes en Croissance.- IV. Thermogénèse des Cultures Bactériennes et Mycéliennes; Fermentations.- V. Chaleurs de Combustion d';Organes et de Produits Végétaux.- VI. Conclusion.- Références Bibliographiques.- Surface Factors Affecting the Penetration of Compounds into Plants..- A. Effect of Molecular Structure on Permeation.- B. Effect of Surface and Interfacial Factors on Potency of Treatments.- C. Surface and Interfacial Tension.- D. Wetting and Spreading.- References.- Tissue and Single Cell Cultures of Higher Plants as a Basic Experimental Method..- A. History of the Method.- B. Types of Cultures.- C. Tissue Culture Media.- D. Isolations of Organs, Tissues and Cells.- E. Transfer and Maintenance of Cultures.- F. Single CeU Cultures.- G. Growth Measurements.- H. Requirementsfor Growth of Callus Cultures.- J. Some Applications of Tissue and Cell Cultures.- K. Resume.- References.- Immunological Methods..- A. The General Principles of Immunological Methods.- B. Purification of Antigens, Immunization of Animals and Treatment of Antisera.- C. Serological Methods.- D. Antigen-Antibody Reactions in Sensitized Animals or Their Organs.- E. Quantitative Determinations of Antigens.- F. Measurements of the Amounts of Antibodies in Sera.- G. Methods for the Determination of Relationships between Antigens.- H. Immuno-Chemical Criteria of Purity of Antigens.- J. Applications.- Concluding Remarks.- References.- Polarography and Tensammetry..- A. Principles of Polarography.- B. The Practice of Polarography.- References.- Fallout Contamination in Plants..- A. Factors which Influence the Fallout Contamination of Plants.- B. Methods of Estimating Gross Fallout Contamination in Plant Material.- C. Methods of Estimating the Individual Radionuclides in Contaminated Plant Materials.- References.- Sachverzeichnis (Deutsch-Englisch).- Subject Index (English-German).- Table des Matières pour la Contribution: H. Prat, Méthodes Calorimétriques pour l';Analyse des Végétaux.