Modern Methods of Geochemical Analysis

The founders of geology at the beginning of the last century were suspicious oflaboratories. Hutton's well-known dictum illustrates the point: "There are also superficial reasoning men . . . they judge of the great oper­ ations of the mineral kingdom from having kindled a fire, and looked into the bottom of a little crucible. " The idea was not unreasonable; the earth is so large and its changes are so slow and so complicated that labo­ ratory tests and experiments were of little help. The earth had to be studied in its own terms and geology grew up as a separate science and not as a branch of physics or chemistry. Its practitioners were, for the most part, experts in structure, stratigraphy, or paleontology, not in silicate chemistry or mechanics. The chemists broke into this closed circle before the physicists did. The problems of the classification of rocks, particularly igneous rocks, and of the nature and genesis of ores are obviously chemical and, by the mid- 19th century, chemistry was in a state where rocks could be effectively analyzed, and a classification built up depending partly on chemistry and partly on the optical study of thin specimens. Gradually the chemical study of rocks became one of the central themes of earth science.

Contenu

1 Introduction.- 1. Classical Definition of Geochemistry.- 2. The Role of Geochemical Analysis.- 2.1. Geology.- 2.2. Geochemistry.- 2.3. Mineralogy.- 2.4. Petrology.- 2.5. Exploration.- 2.6. Mining.- 2.7. Ore Dressing.- 2.8. Chemical Processing.- 3. Summary.- 2 Statistics.- 1. Introduction.- 1.1. The Nature and Scope of Statistics.- 1.2. The Importance of a Statistical Approach in Analytical Chemistry.- 2. Basic Concepts.- 2.1. Variation.- 2.2. Populations and Samples: Parameters and Statistics.- 2.3. Types of Population and Variable.- 2.4. Probability and Random Selection.- 3. Measures of Location and Dispersion.- 3.1. Average: Arithmetic Mean.- 3.2. Variability: Standard Deviation and Variance.- 3.3. Degrees of Freedom.- 3.4. Calculation of the Standard Deviation.- 3.5. Coefficient of Variation.- 4. Frequency Distributions.- 4.1. Normal Distribution.- 4.2. Equation and Properties of the Normal Distribution.- 4.3. Justification for the Assumption of Normality in Practice.- 4.4. Binomial and Poisson Distributions.- 5. Standard Error.- 5.1. Sampling Distributions.- 5.2. Standard Error.- 5.3. Theoretical Derivations.- 5.4. The t Distribution.- 6. Tests of Significance.- 6.1. Introductory Note.- 6.2. Normal Deviate Test.- 6.3. t Test.- 6.4. Variance Ratio (F) Test.- 7. Regression.- 7.1. Introduction.- 7.2. Method of Least Squares.- 7.3. Variance about Regression.- 7.4. Error of Estimation of X from Regression Line.- 8. Analysis of Variance.- 9. Sampling Methods.- 9.1. General Comments.- 9.2. Remarks on Analytical Procedure.- 9.3. Computation of Error Distribution.- 10. Statistical Tables.- 10.1. Values of t.- 10.2. Values of F (P' = 0.05).- 11. Applications to Analytical Methods.- 11.1. Introduction.- 11.2. Reduction in Operational Time.- 11.3. Sampling Errors.- 11.4. Calibration.- 11.5. Blank Variation.- 11.6. Multicomponent Methods of Analysis.- 11.7. Particle Counting.- References.- 3 Chemical Analysis and Sample Preparation.- 1. Introduction.- 2. Sample Preparation.- 2.1. Sampling Procedures.- 2.2. Sample Dividing.- 2.3. Homogenizing.- 2.4. Sample Storage.- 3. Dissolution of Geologic Samples.- 3.1. Acid Digestion.- 3.2. Sample Fusions.- 4. Methods of Separation.- 4.1. Precipitation Methods.- 4.2. Electrolytic Separations.- 4.3. Solvent Extraction.- 5. Methods of Determination.- 5.1. Gravimetric Analysis.- 5.2. Fire Assay.- 5.3. Volumetric Analysis.- 6. Advantages, Disadvantages, and Limitations of Wet Chemical Analyses.- 6.1. General Considerations.- 6.2. Standardization.- References.- 4 Ion-Exchange Chromatography.- 1. Introduction.- 2. Ion-Exchanging Materials.- 2.1. Ion-Exchange Resins.- 2.2. Inorganic Exchangers.- 2.3. Ion Exchangers Based on Cellulose.- 3. Ion-Exchange Selectivity.- 3.1. Inherent Selectivity.- 3.2. Complex Ion Formation.- 4. Anion-Exchange Separations of Metals.- 5. Mixed Solvents in Ion-Exchange Separations.- 6. Special Ion-Exchange Techniques.- 6.1. Ligand Exchange.- 6.2. Isotopic Ion Exchange.- 6.3. Precipitation Ion Exchange.- 6.4. Difference Chromatography.- 6.5. Ion-Exchange Papers.- 7. Applications to Geochemical Analysis.- 7.1. Concentration of Traces of Metals.- 7.2. Removal of Interfering Ions.- 7.3. Systematic Analysis of Silicate Rocks.- 7.4. Individual Elements in Silicate Rocks.- References.- 5 Colorimetry.- 1. Introduction.- 2. Theoretical Considerations.- 2.1. Measurement of Light Absorption.- 2.2. Colorimetric Techniques.- 3. Instrumentation.- 3.1. Filter Photometers.- 3.2. Spectrophotometers.- 3.3. Instrument Selection.- 4. Sample Preparation.- 4.1. Range of Optimum Concentration.- 4.2. Preparation of the Colored System.- 5. Photometric Measurements.- 5.1. Accuracy and Precision.- 5.2. Advantages.- 5.3. Limitations.- 6. Applications.- 6.1. Determination of Metals.- 6.2. Determination of Nonmetals.- References.- 6 Infrared Spectrometry.- 1. Introduction.- 1.1. Historical.- 1.2. Theory.- 1.3. Instrumentation.- 2. Techniques of Sample Presentation.- 2.1. Absorption.- 2.2. Attenuated Total Reflection (ATR).- 2.3. Reflection.- 2.4. Emission Spectroscopy.- 3. Quantitative Applications in Geochemistry.- 4. Mineral Identification with Infrared.- 4.1. Minerals Containing H2O, OH-, and Hydrogen Bond.- 4.2. Carbonate Minerals.- 4.3. Nitrate Minerals.- 4.4. Borate Minerals.- 4.5. The Sulfate Group Minerals.- 4.6. The Silicate Minerals.- 4.7. Phosphates, Vanadates, and Arsenates.- 4.8. Molybdates and Tungstates.- 4.9. Oxide Minerals.- 5. Crystal-Chemistry Studies.- 5.1. Solid-Solution Series.- 5.2. Polymorphous Series.- 5.3. Leaching Studies.- 5.4. Firing Studies.- 5.5. Alteration Studies.- References.- 7 Optical Emission Spectroscopy.- 1. Introduction.- 1.1. History.- 1.2. Principles.- 1.3. Relation to Other Techniques.- 2. Equipment and Facilities.- 2.1. Components and Functions.- 2.2. Laboratory Facilities.- 2.3. Field Facilities.- 2.4. Special-Purpose Equipment.- 3. Techniques.- 3.1. Qualitative Analyses.- 3.2. Semiquantitative Analyses.- 3.3. Quantitative Analyses.- 4. Geochemical Applications.- 4.1. Element Abundance and Distribution.- 4.2. Environmental Studies.- 4.3. Mineral Exploration.- 5. Literature.- 6. Evaluation of the Method.- 7. Future Developments.- References.- 8 Atomic Absorption.- 1. Introduction.- 2. Principles of Atomic Absorption.- 3. Apparatus.- 3.1. Source.- 3.2. Absorption Flame.- 3.3. Spectrometer.- 3.4. Detector.- 3.5. Amplifier and Measuring System.- 4. Sensitivity, Accuracy, and Interferences.- 4.1. Sensitivity.- 4.2. Accuracy.- 4.3. Interferences.- 5. Analysis of Geologic Samples by Atomic Absorption.- 5.1. Major Elements.- 5.2. Minor and Trace Elements.- 5.3. Microtrace Elements after Chemical Enrichment.- 5.4. Water Analysis.- 6. Geochemical Prospecting.- 7. Recent and Future Developments.- References.- 9 X-Ray Techniques.- 1. Introduction.- 2. Theoretical Considerations.- 2.1. Nature and Excitation of X Rays.- 2.2. Interaction of X Rays with Matter.- 2.3. X Rays and Atomic Structure.- 3. Instrumentation.- 3.1. Analytical Systems.- 3.2. Measurement of X-Ray Intensities.- 4. X-Ray Diffraction.- 4.1. Description.- 4.2. Applications.- 5. X-Ray Absorptiometry.- 6. X-Ray-Emission Spectrography.- 6.1. Discussion.- 6.2. Applications.- 6.3. Electron Microprobe.- 6.4. Portable X-Ray-Emission Spectrograph.- References.- 10 Radiometric Technique.- 1. Introduction.- 2. Fundamentals.- 2.1. Nuclear Data of Natural Radioisotopes.- 2.2. Background Radiation.- 2.3. Interaction of Radiation with Matter.- 3. Radiation Detectors.- 3.1. Beta and Gamma Measurement.- 3.2. Alpha Measurement.- 3.3. Scaler and Ratemeter Circuits for Integral Counting, Pulse-Height Analysis.- 3.4. Autoradiographic Methods.- 3.5. Background Reduction for Laboratory Measurem…