The Food Chemicals Codex is the accepted standard for defining the quality and purity of food chemicals. It is frequently referenced by the U.S. Food and Drug Administration and many international food regulatory authorities. This Second Supplement to the Fourth Edition provides revisions and updates, reports on changes in tests and assays, and includes an errata section to both the First Supplement as well as to the Fourth Edition. This supplement also includes eight new and 34 revised monographs, two new and two revised general analytical test methods, and one new test solution. As in the First Supplement, each monograph will be presented in its entirety with a boxed explanatory section preceding it. The corrected or new sections of general analytical tests are also presented in their entirety. A more specific table of contents and the use of page headers, along with other planned design changes, will make this text even easier to use. The supplement will be of interest to producers and users of food chemicals, including processed-food manufacturers, food technologists, quality control chemists, research investigators, teachers, students, and others involved in the technical aspects of food safety.