This book deals with the principles and practices of electrochemical methods as applied to soil and water research, particularly those that can be carried out in the field. Beginning with the basis of potentiometric methods, including electrode potential, principles of potentiometric methods, reference electrodes, liquid-junction potential and characteristics of ion-selective electrodes, the author then proceeds to describe the properties and applications of various types of potentiometric electrodes, including glass, solid-state membrane, liquid-state membrane, oxidation-reduction and gas sensors. A special chapter devoted to commonly encountered problems will aid readers not familiar with potentiometric methods. Voltammetric methods, conductometric methods and electrochemical instruments are also discussed.