CONTENTS 



Preface vii 



I. Introduction 1 



1 Biological Significance of the Pyrrole Pigments 1 



2 Fundamentals of the Chemical Structure of Pyrrole Pigments 3 



3 Variability of the Pyrrole Pigments 6 



4 Metabolism of Pyrrole Pigments 7 



II. Methods of Investigation. In collaboration with J. P. Callaghan 9 



1 Introduction 9 



2 Spectroscopy 10 



2.1 The Direct Vision Spectroscope 10 



2.2 The Hartridge Reversion Spectroscope 10 



3 Absorption Spectrophotometry 11 



3.1 Theoretical 11 



3.1.1 Theory of Light .\bsorption 11 



3.1.2 The Absorption Curve 14 



3.1.3 Determination of Concentration by Spectrophotometry 14 



3.1.4 Spectrophotometric Titrations 15 



3.2 Methods of Measurement 16 



4 Colorimetry and Fluorescence Measurement 17 



4.1 Colorimetry 17 



4.2 Fluorescence 18 



5 The Photochemical Absorption Spectrum 18 



6 Magnetochemistry and Bond Type 21 



6.1 Electronic Basis of Bond Formation 21 



6.2 Magnetic Properties of Molecules 24 



6.3 Determination of Paramagnetic Susceptibility 25 



6.4 Magnetochemical Titrations 25 



7 Potentiometric Methods 25 



7.1 Determination of Dissociation Constants 26 



7.1.1 Elementary Theory 26 



7.1.2 Titration Curves 27 



7.1.3 Titration Curves of Proteins 27 



7.1.4 Differential Titration of Proteins 28 



7.2 Oxidation-Reduction Potentials 28 



7.2.1 Fundamental Oxidation-Reduction Equation 29 



7.2.2 Effect of ;>H 32 



7.2.3 Change in Aggregation 35 



7.2.4 Combination of Oxidant and Reductant with Other 

 Substances 36 



7.2.5 Interaction between Oxidation-Reduction Systems 44 



7.2.6 Electroactivity and Electroinactivity 44 



8 Other Methods 45 



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