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 epoxy resins is the epoxide group content. This is correctly expressed as the specific amount of substance of epoxide groups in the material B under consideration, calculated as the ratio of the amount of substance of epoxide groups in this material B, "n"(EP), divided by the mass "m"(B) of the material B under consideration, in this case, the mass of the resin. The SI unit for this quantity is "mol/kg", or multiples thereof. Deprecated quantities which are still in use are the so-called "epoxide number" which is (not a number and should therefore not be referred to as such, but)