THIS manual must be regarded as the only guide to measurements in physical chemistry which has yet been published. The book is not intended to completely cover this field of investigation, but has evidently been devised with the primary object of assisting Prof. Ostwald in his course of instruction at Leipzig. It is not an introduction to the subject, as the detail supplied, both in connection with apparatus and methods, is insufficient for the requirements of the beginner; nor is it a treatise wherein a representative collection of methods may be consulted. The book is rather to be viewed as an aid to the teacher, or as indicating to the chemist or the physicist methods which for the most part the author has found to be of service in his own laboratory. Hand- und Hilfsbuch zur Ausfuhrung physiko-chemischer Messungen. Von W. Ostwald. (Leipzig: W. Engelmann, 1893.)