The Codex deals with the direct additives used to prepare drinking water. These chemicals are categorized according to use patterns, i.e. (a) coagulation and flocculation; (b) softening, precipitation and pH control; (c) disinfection and oxidation; and (d) miscellaneous treatment applications. Impurities discussed on those already identified by the National Interim Drinking Water regulations as well as those deemed possible by virtue of manufacturing process or chemical similarity to the direct additive. The basic form of the Codex is a series of individual monographs, each dealing with a specific compound. Each such monograph contains descriptive information such as physical properties, most common usage and dosage as well as recommended purity requirements.