Mr. Alexander has greatly enlarged his interesting little book. The new edition continues to be a readable and easily understood exposition of this subject. The theoretical section contains a brief development of the whole field of colloids, in which the author introduces and explains some of the common terms used in this field. Mathematical development is absent. The practical section gives a brief survey of the fields of recognized colloid problems. Explanations of phenomena from a colloid point of view are abundant. References to the literature are given throughout. Although the field of colloids is treated in a rather elementary fashion, perusal of this volume will clarify the view of the "great scheme of things" for the average reader.