Thispaper summarizes the chief trends in the development and applications of potentiometric methods of analysis since the last review in this series (152), covering the period from January 1962 to December 1963.Bates and Guggenheim (17) have reviewed the degree of standardization of pH terminology and standard buffers in Great Britain, United States, and Japan. Van Rysselberghe (235) has examined possible definitions of pH at low and at high ionic strengths and compared these with some aspects of the report on the standardization of pH by Bates and Guggenheim (17). Many practical aspects of pH measurement have been described by Mattock (14-2).