Amount of substance in use in chemical engineering in the United States is the pound-mole, having the symbol lb-mol. One pound-mole is . When quoting an amount of substance, it is necessary to specify the entity involved, unless there is no risk of ambiguity. One mole of chlorine could refer either to chlorine atoms, as in 58.44 g of sodium chloride, or to chlorine molecules, as in 22.711 liters of chlorine gas at STP. The simplest way to avoid ambiguity is to replace the term "substance" by the name of the entity or to quote the empirical formula. For example: Amount of substance
Chemical nomenclature of technical terms used in chemistry. Similar compendia exist for biochemistry (the "White Book", in association with the IUBMB), analytical chemistry (the "Orange Book"), macromolecular chemistry (the "Purple Book") and clinical chemistry (the "Silver Book"). These "color books" are supplemented by shorter recommendations for specific circumstances that are published periodically in the journal "Pure and Applied Chemistry". The primary function of chemical nomenclature is to ensure that a spoken or written chemical name leaves no ambiguity concerning which chemical compound the name refers to: each chemical name should refer to a single substance. A less important aim is to ensure