Fundamentals of AIMALYTICAL CHEMISTRY

Fundamentals of

AIMALYTICAL C H E M I S T R Y

Seventh Edition

Douglas A. Skoog Stanford University

Donald M. West San Jose State University

F. James Holler University ;of Kentucky

W r

SAUNDERS COLLEGE PUBLISHING Harcourt Brace College Publishers

Fort Worth Philadelphia San Diego New York Orlando Austin San Antonio Toronto

Montreal London Sydney Tokyo

Contents

i

4

Introduction 1

1A Role of Analytical Chemistry in the Sciences 7

1B Classification of Quantitative Methods of Analysis 2

1C Steps in a Typical Quantitative Analysis 3

Errors in Chemical Analyses 11

2A Definition of Terms 12

2B Systematic Errors 16

2C Questions and Problems 20

Random Errors in Analyses 21

3A The Nature of Random Errors 21

3B The Statistical Treatment of Random Error 25

3C The Standard Deviation of Computed Results 33

3D Methods for Reporting Computed Data 39

3E Questions and Problems 44

Application of Statistics to Data Treatment and Evaluation

4A Confidence Limits 47

4B Statistical Aids to Hypothesis Testing 51

4C Detection of Gross Errors 57

4D Estimation of Detection Limits 59

4E The Least-Squares Method for Deriving Calibration Plots

4F Quality Assurance and Control Charts 65

4G Questions and Problems 68

Gravimetrie Methods of Analysis 71

5A Gravimetrie Calculations 73

5B Properties of Precipitates and Precipitating Agents 82

5C Drying and Ignition of Precipitates 92

5D Application of Gravimetrie Methods 93


xii Contents

7

8

10

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Titrimetric Methods of Analysis 700

6A Some General Aspects of Volumetrie Titrimetry 100

6B Standard Solutions 702

6C Volumetrie Caiculations 103

6D Gravimetrie Titrimetry 7 77

6E Questions and Problems 7 78

Aqueous-Solution Chemistry 722

7A The Chemical Composition ofAqueous Solutions 722

7B Chemical Equilibrium 126


Effect of Electrolytes on lonic Equilibria 148

8A Thermodynamic Versus Concentration-Based Equilibrium Consta nts 748

8B Activity Coefficients 757


Application of Equilibrium Caiculations to Complex Systems 159

9A A Systematic Method for Solving Multiple-Equilibrium Problems 760

9B The Calculation of Solubility by the Systematic Method 764

9C Separation of Ions by Control of the Concentration of the Precipitating Agent 783

9D Questions and Problems 787

Theory of Neutralization Titrations 189

10A Solutions and Indicators for Acid/Base Titrations 789

10B Titration Curves 792

10C Titration Curves for Strong Acids and Strong Bases 794

10D Buffer Solutions 200

10E Titration Curves for Weak Acids 270

10F Titration Curves for Weak Bases 274

10G The Composition of Buffer Solutions as a Function of pH 276

10H Common Types of Acid/Base Indicators 278

101 Questions and Problems 227

Titration Curves for Complex Acid/Base Systems 224

11A Mixtures of Strong and Weak Acids or Strong and Weak Bases 224

I IB Polyfunctional Acids 228

11C Polyfunctional Bases 228

11D Buffer Solutions Involving Polyprotic Acids 229

Contents xii i

1 9 1Z

1 '"J 13

14

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11E Caiculation of the pH of Solutions of Amphiprotic Salts 231

11F Titration Curves for Polyfunctional Acids 234

11G Titration Curves for Polyfunctional Bases 240

11H Titration Curves for Amphiprotic Species 247

111 The Composition of Solutions of a Polyprotic Acid as a Function of pH 243

11J Questions and Problems 245

Applications of Neutralization Titrations 248

12A Reagents for Neutralization Titrations 248

12B Typical Applications of Neutralization Titrations 254


Precipitation Titrimetry 266

13A Titration Curves 266

13B End Points for Argentometric Titrations 270

13C Applications of Standard Silver Nitrate Solutions 275


Complex-Formation Titrations 278

14A Complex-Formation Reactions 278

14B Titrations with Aminocarboxylic Acids 279

14C Titrations with Inorganic Complexing Agents 300


An Introduction to Electrochemistry 303

15A Oxidation/Reduction Reactions 303

15B Electrochemical Cells 307

15C Electrode Potentials 377


Applications of Standard Electrode Potentials 330

16A The Thermodynamic Potential of Electrochemical Cells 330

16B Calculations of Redox Equilibrium Constants 338

16C Redox Titration Curves 343

16D Oxidation/Reduction Indicators 354

16E Potentiometrie End Points 358

16F Questions and Problems 358

Applications of Oxidation/Reduction Titrations 360

17A Auxiliary Oxidizing and Reducing Reagents 360

17B Application of Standard Reductants 362

xiv Contents

18

19

20

21

22

17C Applications of Standard Oxidants 366

17D Some Specialized Oxidants 375


Theory of Potent iometry 386

18A General Principles 386

18B Reference Electrodes 387

18C Liquid-Junction Potentials 389

18D Indicator Electrodes 390


Applications of Potent iometry 412

19A Instruments for Measuring Cell Potentials 412

19B Direct Potentiometrie Measurements 475

19C Potentiometrie Titrations 423

19D The Determination of Equilibrium Constants from Electrode Potential Measurements 427


Electrogravimetric and Coulometric Methods 431

20A The Effect of Current on the Potential of Electrochemical Cells 431

20B The Potential Selectivity of Electrolytic Methods 439

20C Electrogravimetric Methods ofAnalysis 440

20D Coulometric Methods of Analysis 446


Voltammetry 460

21A Excitation Signals in Voltammetry 467

21B Linear-Scan Voltammetry 462

21C Pulse Polarographic and Voltammetric Methods 486

21D Stripping Methods 490

21E Voltammetry with Ultramicroelectrodes 494


An Introduct ion to Spectrochemical Methods 497

22A General Properties of Electromagnetic Radiation 497

22B The Electromagnetic Spectrum 507

22C Absorption of Radiation 502

22D Emission of Electromagnetic Radiation 573


Contents xv

24

25

26

7

28

29

Instruments for Optical Spectrometry 527

23A Instrument Components 527

23B Optical Instrument Designs 550


Molecular Absorption Spectroscopy 557

24A Ultraviolet and Visible Molecular Absorption Spectroscopy 557

24B Automated Photometrie and Spectrophotometric Methods 587

24C Infrared Absorption Spectroscopy 592


Molecular Fluorescence Spectroscopy 607

25A Theory of Molecular Fluorescence 607

25B Effect of Concentration on Fluorescence Intensity 605

25C Fluorescence Instruments 606

25D Applications of Fluorescence Methods 607


Atomic Spectroscopy Based on Ultraviolet and Visible Radiation 67 7

26A Sources of Atomic Spectra 67 7

26B Atomic Spectroscopy Based upon Flame Atomization 672

26C Atomic Spectroscopy with Electrothermal Atomizers 626

26D Atomic Emission Methods Based on Plasma Sources 632


Kinetic Methods of Analysis 637

27'A Rates of Chemical Reactions: Rate Laws 638

27B The Determination of Reaction Rates 648

27C Applications of Kinetic Methods 655


An Introduction to Chromatographie Methods 660

28A A General Description of Chromatography 660

28B Migration Rates of Solutes 663

28C Band Broadening and Column Efficiency 666

28D Column Resolution 676

28E Applications of Chromatography 682


Gas-Liquid Chromatography 686

29A Instruments for Gas-Liquid Chromatography 687

29B Gas-Chromatographie Columns and the Stationary Phase 693

xvi Contents

30

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32

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29C Applications of Gas-Liquid Chromatography 698

29D Gas-Solid Chromatography 699


High-Performance Liquid Chromatography 707

30A Instruments 703

30B High-Performance Partition Chromatography 708

30C High-Performance Adsorption Chromatography 770

30D High-Performance Ion-Exchange Chromatography 770

30E High-Performance Size-Exclusion Chromatography 774

30F Comparison of High-Performance Liquid Chromatography with Gas-Liquid Chromatography 777

30G Supercritical-Fluid Chromatography 778

30H Planar Chromatography 727

301 Questions and Problems 724

The Analysis of Real Samples 725

31A Choice of Method for the Analysis of Real Samples 727

31B The Accuracy Obtainable in the Analysis of Complex Materials 732

Preparing Samples for Analysis 736

32A Sampling 736

32B Moisture in Samples 744

32C The Determination of Water in Samples 747


Decomposing and Dissolving the Sample 749

33A Sources of Errors in Decompositipn and Dissolution 749

33B Decomposing Samples by Inorganic Acids in Open Vessels 750

33C Microwave Decompositions 752

33D Combustion Methods for Decomposing Organic Samples 754

33E Decomposition of Inorganic Materials by Fluxes 756


Eliminating Interferences 760

34A The Nature of the Separation Process 760

34B Separation by Precipitation 767

34C Separation by Extraction 764

34D Application of Extraction Procedures 769

34E Ion-Exchange Separations 774

34F The Separation of Inorganic Species by Distillation 775

34G Questions and Problems 776

Contents xvii

1 ^ 1 I

36

The Chemicals, Apparatus , and Uni t Operat ions of Analyt ical

Chemistry 778

35A The Selection and Handling of Reagents and Other Chemicals 778

35B The Cleaning and Mark ing of Laboratory Ware 779

35C The Evaporation of Liquids 780

35D The Measurement of Mass 780

35E The Equipment and Manipulat ions Associated w i t h Weigh ing 787

35F Weigh t Titrations 790

35G The Equipment and Manipulat ions for Fil tration and Igni t ion 797

35H The Measurement of Volume 798

351 The Calibration of Volumetr ie Ware 806

35J The Laboratory Notebook 808

35K Safety in the Laboratory 870

Selected M e t h o d s of Analysis 812

36A Gravimetrie Methods of Analysis 813

36B Neutral izat ion Titrat ions 878

36C Precipitation Titrat ions 827

36D Complex-Formation Titrat ions w i t h EDTA 830

36E Titrat ions w i t h Potassium Permanganate 833

36F Ti t rat ion w i t h lodine 839

36G Titrat ions w i t h Sodium Thiosulfate 847

36H Titrat ions w i t h Potassium Bromate 844

361 Potentiometr ie Methods 846

36J Electrogravimetric Methods 852

36K Coulometric Titrat ions 854

36L Vol tammetry 855

36M Methods Based on the Absorpt ion of Radiation 858

36N Molecular Fluorescence 862

360 Atomic Spectroscopy 863

36P Applicat ions of Ion-Exchange Resins 866

36Q Gas-Liquid Chromatography 868

Glossary G-7

j Selected References to the Literature of Analytical Chemistry A-

A P P E N D I X 2 Solubility Product Constants A-6

A P P E N D I X o Dissociation Constants for Acids A-8

A P P E N D I X

3

xviii Contents

A P P E N D I X A Stepwise Formation Constants A-10

A P P E N D I X c Some Standard and Formal Electrode Potentials A-12

A P P E N D I X /r Designations Carried by Ashless Filter Papers A-16

A P P E N D I X -i Designations and Porosities for Filtering Crucibles A-17

A P P E N D I X Q Use of Exponential Numbers and Logarithms A-18

A P P E N D I X Q Volumetrie Caiculations Using Normality and Equivalent Weight A-23

A P P E N D I X | Q Compounds Recommended for the Preparation of Standard Solutions of Common Elements A-32

A P P E N D I X | i Propagation of Measurement Uncertainties A-34

Answers to Selected Questions and Problems A-40

Index 1-1

Fundamentals of AIMALYTICAL CHEMISTRY

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