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
Stoic physics Stoic physics Stoic physics is the natural philosophy adopted by the Stoic philosophers of ancient Greece and Rome used to explain the natural processes at work in the universe. To the Stoics, the universe is a single pantheistic God, but one which is also a material substance. The primitive substance of the universe is a divine essence ("pneuma") which is the basis of everything which exists. This "pneuma", which is the active part or reason ("logos") of God, provides form and motion to matter, and is the origin of the elements, life, and human rationality. From their physics, the Stoics