Lewis acids and bases studied chemical bonding. In 1923, Lewis wrote "An acid substance is one which can employ an electron lone pair from another molecule in completing the stable group of one of its own atoms." The Brønsted–Lowry acid–base theory was published in the same year. The two theories are distinct but complementary. A Lewis base is also a Brønsted–Lowry base, but a Lewis acid doesn't need to be a Brønsted–Lowry acid. The classification into hard and soft acids and bases (HSAB theory) followed in 1963. The strength of Lewis acid-base interactions, as measured by the standard enthalpy of formation of an adduct
GESTIS Substance Database results. A mobile version of the GESTIS Substance Database, suitable for smartphones and tablets, is also available. GESTIS Substance Database GESTIS Substance Database is a freely accessible online information system on chemical compounds. It is maintained by the Institut für Arbeitsschutz der Deutschen Gesetzlichen Unfallversicherung (IFA, Institute for Occupational Safety and Health of the German Social Accident Insurance). Information on occupational medicine and first aid is compiled by Henning Heberer and his team (TOXICHEM, Leuna). The database contains information for the safe handling of hazardous substances and other chemical substances at work: The available information relates to about 9,400 substances.