Principles of Polarography

I. Principles of Polarography


1. The Origin of Polarography

Electrocapillarity


2. A Simple Measuring Circuit

Influence of the Resistance of the Potentiometer


3. Polarization of the Dropping Mercury Electrode and Depolarization Processes


4. Current-Potential Curves without Concentration Polarization. The Exponential Form of Polarographic Curves


5. The Polarograph

Literature

II. Polarizable Electrodes Used in Polarography

A. Mercury Capillary Electrodes


1. The Dropping Mercury Electrode


2. Streaming Mercury Electrode (Mercury Jet Electrode)

B. Stationary Mercury Electrodes

C. Solid Electrodes

Literature

III. Charging Current

Integral and Differential Capacity of the Electrode Double-Layer

Literature

IV. Influence of the Resistance of the Electrolyte on Polarographic Curves

Literature

V. Migration Currents

A. Influence of Concentration of Indifferent Electrolyte


1. Reduction of Cations


2. Reduction of Anions


3. Oxidation of Cations


4. Anodic Depolarization of Anions

B. "Exaltation" of the Migration Current

Literature

VI. Diffusion-Controlled Current

Introduction


1. Diffusion to Stationary Electrodes

Linear Diffusion

Spherical Diffusion


2. Linear Diffusion to a Growing Dropping Electrode — the Ilkovič Equation


3. Consequences of the Ilkovič Equation

a) Dependence on Concentration

b) Dependence on the Height of the Mercury Head, Capillary Characteristics and Potential


4. Influence of Temperature on the Diffusion Current


5. Correction for Spherical Diffusion in the Ilkovič Equation


6. Comparison of Experimental Results Obtained with the Simple Ilkovič

Equation and with the Equation Corrected for Spherical Diffusion

A. Assumptions made in Deriving a Diffusion Current Equation

B. Survey of Experimental Verifications of Diffusion Current Equations


7. Dropping Mercury Amalgam Electrode


8. Diffusion Coefficients


9. Influence of Viscosity and of Complex Formation on Diffusion Current


10. Diffusion Current at a Streaming Electrode


11. Rotated Disc Electrode


12. Rotated Dropping Mercury Electrode

Literature

VII. Equation of a Reversible Polarographic Wave


1. Equation of a Cathodic Wave


2. Equation of an Anodic Wave


3. Equation of an Cathodic-Anodic Wave


4. Analysis of Reversible Polarographic Waves


5. Derivative Polarographic Curves


6. Significance of Half-Wave Potentials


7. Influence of Ionic Strength on Half-Wave Potentials


8. Equation of a Polarographic Wave Corrected for Spherical Diffusion


9. i-t-Curves on the Rising Portion of a Reversible Polarographic Wave


10. Equation of a Reversible Process at the Hanging Mercury Drop Electrode

Literature

VIII. Reversible Processes Controlled by Diffusion of Complex Ions


1. Reversible Reduction of Complexes to Metals


2. Consecutive Complex Formation in which the Reduction Product Forms an Amalgam


3. Determination of the Mean Diffusion Coefficient


4. Reduction of Complexes to a Lower Valency


5. Successive Reduction of Complexes

Literature

IX. Reversible Reduction of Organic Substances

Literature

X. Deposition of Mercury Ions Formation of Salts and Complexes with Mercury


1. Reduction of Mercurous and Mercuric Ions


2. Reduction of Mercury Complexes


3. Anodic Dissolution of Mercury


4. Formation of Insoluble Salts with Mercury


5. Formation of Complexes with Mercury

Literature

XI. Polarographic Curves for the Formation of Semiquinones and Dimers


1. The Current-Voltage Curve for the Formation of Semiquinones


2. The Current-Voltage for the Complete Dimerization of a Semiquinone

Literature

XII. Diffusion Currents in Unbuffered Media and in Solutions with Insufficient Concentration of Complex-Forming Agents


1. Diffusion Currents in Unbuffered and Insufficiently Buffered Media

a) Unbuffered Solutions

b) Diffusion Currents in Poorly Buffered Media


2. Diffusion Currents for Complexes with an Insufficient Concentration of the Complex-Forming Agent


3. Reaction of Depolarization Products with Another Depolarizer

Literature

XIII. Mixed Currents. Simultaneous Oxidation and Reduction Processes

Literature

XIV. Irreversible Electrode Processes


1. An Approximate Treatment of a Slow Electrode Process


2. A Rigorous Treatment of a Slow Electrode Process


3. Polarographic Curves for Irreversible Processes at a Hanging Mercury Drop


4. Irreversible Reduction of Complexes

Complexes and the Rate of Electrode Processes


5. Determination of Activation Energy for an Irreversible Electrode Process


6. The Electrode Double Layer and the Rate of the Electrode Process

a) Properties of the Electrode Double Layer

b) Influence of Structure of the Electrode Double Layer on the Rate of an Irreversible Process


7. Reduction of Cations

A. Reduction of Hydrogen Ions and Hydrogen Overvoltage

B. Further Examples


8. Reduction of Anions and the Discontinuity on Their Polarographic Curves

a) Influence of Electrolytes on the Reduction and Half-Wave Potentials of Anions

b) Limiting Currents for Anions

c) Interpretation of the Reduction of Anions

d) Reduction of Nitrate Ions and Discontinuity on Polarographic Curves

e) Non-Reducible Anions


9. Polarography of Organic Substances

Correlations between Half-Wave Potentials and the Constitution of Organic Substances

Literature

XV. Applications of Limiting Currents

A. Limiting Current Titrations (Amperometric or Polarometric Titrations)

Types of Titrations

Apparatus

B. Polarographic Coulometry


1. Determination of the Number of Electrons n


2. Coulometry in Polarographic Analysis

C. Investigation of Kinetics of Homogeneous Reactions in Solution

Introduction

Fundamentals of the Measuring Technique

Investigation of Fast Reactions

Photo-Polarography

Literature

XVI. Adsorption Effects at the Dropping Mercury Electrode

A. Polarographic Currents Influenced by Adsorption of Electroactive Substances


1. Reversible Processes


2. Irreversible Processes

B. Polarographic Currents Influenced by Adsorption of Electroinactive Substances


1. Inhibition and Acceleration of the Electrode Process by Surface-Active Substances


2. Classification of Surface-Active Substances


3. Qualitative Interpretation of Effect of Surface-Active Substances on Electrode Processes


4. Quantitative Theories of the Effect of Surface-active Substances on Electrode Processes

Literature

XVII. Kinetic Currents

Introduction

Types of Chemical Reactions Affecting Polarographic Currents

Methods for Computing Kinetic Currents

A. Reactions Preceding the Electrode Process

B. Reactions Parallel to the Electrode Process-Catalyzed Electrode Processes

C. Reactions Subsequent to the Electrode Process

Literature

XVIII. Catalytic Hydrogen Currents

Catalysis by Platinum Metals

Catalysis by Substances Present in the Solution


1. Historical Introduction


2. Influence of pH and Buffer Concentration on Catalytic Limiting Currents of Hydrogen


3. Properties of Catalytic Currents


4. Catalytically-Active Groups


5. Interpretation of the Catalytic Evolution of Hydrogen


6. Catalysis in Buffered Solutions in the Presence of Cobalt Salts

Literature

XIX. Polarographic Maxima

A. Maxima of the First Kind

Introduction


1. Occurrence and Properties


2. Suppression of Maxima of the First Kind


3. Polarity of Maxima of the First Kind


4. Streaming of Electrolyte and Maxima of the First Kind


5. Interpretation of Maxima of the First Kind

Β. Maxima of the Second Kind

Introduction


1. Occurance and Properties


2. Suppression of Maxima of the Second Kind


3. Streaming of Electrolyte with Maxima of the Second Kind


4. Interpretation of Maxima of the Second Kind

C. Simultaneous Occurrence of Maxima of the First and the Second Kind

D. Other Maxima

E. Practical Application of Polarographic Maxima

Literature

XX. Polarography in Non-Aqueous Solvents and Melts

Introduction


1. Reference Electrodes and the Influence of the iR Drop


2. Frequently Used Solvents

a) Alcohols

b) Acetic Acid

c) Sulphuric Acid

d) Formic Acid

e) Liquid Ammonia

f) Acetonitrile

g) Ethylenediamine

h) Other Solvents


3. Polarography in Melts

Literature

XXI. The Kalousek Commutator (Switch) and Related Methods

A. Mean Currents with Square Wave (Rectangular) Voltage

Introduction


1. Selection of the Commutated Voltage and the Character of the Recorded Current-Voltage Curves


2. Later Modifications of the Commutator


3. Experimental Results


4. Calculation of Currents with a Periodically Changing Square-Wave Voltage

B. Methods Related to the Kalousek Commutator

Literature

XXII. Oscillographic Polarography

Introduction

Osciloscopic Investigation of Instantaneous Currents at Constant Potential

Measurement of Half-Wave Potentials

Oscillographic Polarography Proper

A. Oscillographic Polarography with Applied Voltage

B. Controlled-Current Oscillographic Polarography

Literature

Tables of Half-wave Potentials

List of Symbols

Text—Books on Polarography

Index