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
Epoxy the ratio of the amount of substance of epoxide groups, "n"(EP), and the mass "m"(B) of the material B, with the SI unit "mol/kg", or the so-called "epoxide equivalent weight", which is the ratio of the mass of a sample B of the resin and the amount of substance of epoxide groups present in that sample B, with the SI unit "kg/mol". The so-called "epoxide equivalent weight" is simply the inverse of the so-called "epoxide number". The specific amount of substance of epoxide groups is used to calculate the mass of co-reactant (hardener) to use when curing epoxy resins. Epoxies