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 and maintaining the specialized cells. The apparent altruistic behavior is not clearly understood, because the likely explanation of kin selection is not supported by the shoal structure of common minnows in which shoalmates are not necessarily closely related. When common minnows sense the alarm substance, they form tighter shoals as individuals move to be in the central position in their shoaling group. However, in an experiment where common minnows were habituated to the chemical by continuous exposure, common minnows did not react to the signal. Only the naïve common minnows reacted to the signal by relocating themselves to the central