A review of textbook methods One of the problems facing the general chemistry instructor is to teach students to write oxidation-reduction equations. Although there has been considerable discussion of the merits and meaning of various methods in the pages of this Journal, the method learned and used by the student is somewhat dependent upon the instructor's choice of text. Many new general chemistry books have been written during the past decade and most of the older books have now been revised. All of these books contain excellent material on electrochemistry and elements with variable oxidation states. However, the contents of this material do not necessarily include directions to the student which will aid him in writing oxidation-reduction reactions. The purpose of this paper is to review those parts of a number of textbooks which do contain aids or suggestions which will help the student to balance oxidation-reduction reactions.The suggestions may be confined to a single chapter appropriately entitled "Oxidation-Reduction" (4, 7, 9, 11, 13). When the techniques of writing equations are included with other material, the chapter headings are generally composite. Typical titles are "Hydrogen Peroxide and Oxidations in General," (12) "Hydrogen, Reduction-Oxidation, Oxidation States" (6), "Chlorine and Hydrochloric acid; the Oxidation State" (5) and "Oxidation-Reduction, Half Reactions, Galvanic Cells." Sometimes there is no hint from the chapter heading that material on how to write equations is included. Thus in the book by Sorum (19) detailed instructions for balancing ionic reactions are found in Chapter 16 which is simply called "The Halogens." Finally a number of authors (6, 8, 9, 17) present the oxidation-number and the ion-electron methods for balancing equations in two (or more) separate chapters. General Advice to the Student Using bold-face type, Pauling (11) writes "BE SURE THAT YOU KNOW WHAT THE REACTANTS ARE AND WHAT THE PRODUCTS ARE." Mack, et al. (8) write nearly the identical sentence in italics.A similar emphasis on knowing what the reactants and products will be or on knowing what the oxidation numbers and characteristic compounds the elements are capable of assuming is made by several others (5, 9, 12). Often the writer then (3,4,5,11) goes on to point out that the reactants and products can be determined from a knowledge of their chemical characteristics, by direct examination and analysis, by examining the literature, and by the use of chemical theory.Only two authors give definite rules for the deter-mination of the products of oxidation and reduction.Schlesinger (//) writes:(1) The more concentrated the solution of the oxidizing agent, the smaller will be the change in its valence number. . . .(2) The stronger the reducing agent, the greater the change in the valence number of the oxidizing agent.