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
Common minnow skin cells called alarm substance cells and is released from an injured or killed minnow. The shoalmates can detect the chemical and respond to the increased risk of predation. The production and release of this alarm substance are altruistic because the sender of the signal, who does not directly benefit from the signal released upon its injury, has to pay the cost for the production and release of the chemical. In fact, the alarm substance cells decrease in number when the common minnows are in poor physical condition due to scarce food, indicating that there is metabolic cost for producing