<P> 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 . </P> <P> The alchemists, and especially the early metallurgists, probably had some notion of amount of substance, but there are no surviving records of any generalization of the idea beyond a set of recipes . In 1758, Mikhail Lomonosov questioned the idea that mass was the only measure of the quantity of matter, but he did so only in relation to his theories on gravitation . The development of the concept of amount of substance was coincidental with, and vital to, the birth of modern chemistry . </P> <Ul> <Li> 1777: Wenzel publishes Lessons on Affinity, in which he demonstrates that the proportions of the "base component" and the "acid component" (cation and anion in modern terminology) remain the same during reactions between two neutral salts . </Li> <Li> 1789: Lavoisier publishes Treatise of Elementary Chemistry, introducing the concept of a chemical element and clarifying the Law of conservation of mass for chemical reactions . </Li> <Li> 1792: Richter publishes the first volume of Stoichiometry or the Art of Measuring the Chemical Elements (publication of subsequent volumes continues until 1802). The term "stoichiometry" is used for the first time . The first tables of equivalent weights are published for acid--base reactions . Richter also notes that, for a given acid, the equivalent mass of the acid is proportional to the mass of oxygen in the base . </Li> <Li> 1794: Proust's Law of definite proportions generalizes the concept of equivalent weights to all types of chemical reaction, not simply acid--base reactions . </Li> <Li> 1805: Dalton publishes his first paper on modern atomic theory, including a "Table of the relative weights of the ultimate particles of gaseous and other bodies". </Li> </Ul> <Li> 1777: Wenzel publishes Lessons on Affinity, in which he demonstrates that the proportions of the "base component" and the "acid component" (cation and anion in modern terminology) remain the same during reactions between two neutral salts . </Li>

Amount of matter in one unit of volume