The Formula Section lists the molecular formulas for all substances of known chemical constitution appearing in the TSCA Candidate List of Chemical Substances, which are in the other two volumes. Where two or more substances share the same molecular formula, their names are ordered alphabetically by the principles described before the Substance Name Section. Element symbols in the molecular formulas are arranged according to the Hill system. The resulting complete molecular formulas are arranged in alphabetical order in the Formula Section, with each chemical element and its particular numerical suffix being considered as a separate unit. Salts, molecular addition compounds, and copolymers are represented in the Formula Section by the molecular formula for only one of their components, rather than by a summation formula which includes all the components. The molecular formula chosen to represent a substance of this type is the formula of the component whose name is selected as the principal heading for the substance in the CA Chemical Substance Index. In general, metal salts of acids appear at the molecular formulas of the acids; salts of organic bases with inorganic acids or common organic acids appear at the molecular formulas of the bases; salts with more complex organic acids appear at the molecular formulas of the acids; molecular addition compounds and copolymers appear at the molecular formula of the component chosen to receive the principal index name for the substance by the nomenclature policies used for CA indexes. Thus, a user of the Formula Section who wishes to find an entry for a salt, molecular addition compound, or copolymer is advised to consult entries at the molecular formulas for each of the components before concluding that the substance is not cited in the Formula Section.