Mole (unit) measure the amount of substance (although in practice it is usual). There are many physical relationships between amount of substance and other physical quantities, the most notable one being the ideal gas law (where the relationship was first demonstrated in 1857). The term "mole" was first used in a textbook describing these colligative properties. Chemical engineers use the unit extensively, and decimal multiples may be more suitable for industrial use. For convenience in avoiding conversions in the imperial (or American customary units), some engineers adopted the "pound-mole" (notation "lb-mol" or "lbmol"), which is defined as the number of entities in
Amount of substance the molar mass. Molar quantities are sometimes denoted by a subscript Latin "m" in the symbol, e.g. "C", molar heat capacity at constant pressure: the subscript may be omitted if there is no risk of ambiguity, as is often the case in pure chemistry. The main derived quantity in which amount of substance enters into the numerator is amount of substance concentration, "c". This name is often abbreviated to "amount concentration", except in clinical chemistry where "substance concentration" is the preferred term to avoid ambiguity with mass concentration. The term "molar concentration" is incorrect, but commonly used. The alchemists, and