The Theory of Valency, written by John Newton Friend and published in 1909, is a comprehensive exploration of the concept of valency in chemistry. The book delves into the historical development of the theory of valency, as well as its practical applications in chemical reactions and molecular structures. Friend also discusses the various methods for determining valency, including experimental techniques and theoretical models. The book is aimed at chemists and students of chemistry who are interested in gaining a deeper understanding of the fundamental principles of chemical bonding and reactivity. Overall, The Theory of Valency is a valuable resource for anyone seeking to broaden their knowledge of chemistry and its applications.This scarce antiquarian book is a facsimile reprint of the old original and may contain some imperfections such as library marks and notations. Because we believe this work is culturally important, we have made it available as part of our commitment for protecting, preserving, and promoting the world's literature in affordable, high quality, modern editions, that are true to their original work.