When the chemical composition of a pharmacopoeial substance is known or generally accepted, the empirical chemical formula and the relative molecular mass are given. For organic substances, the graphic formula, when known or generally accepted, is also given. These formulae and relative molecular masses are given at the beginning of the monographs and are those of the chemically pure substances; they are not to be regarded as an indication of the purity of the substance under test. Elsewhere, in statements of specifications of purity and strength, and in descriptions of processes for assay, it is evident from the context that the formulae denote the pure chemical substances.