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
Chemical safety assessment the European Chemicals Agency as part of the respective registration dossier. The purpose is to ensure that the risks related to the substance are controlled. The chemical safety assessment of a substance comprises the following steps: The European Chemicals Agency (ECHA) has developed a software tool to support industry in preparing a Chemical Safety Assessment (CSA) and Chemical Safety Report (CSR). Chesar Beta version can be downloaded from the Chesar website. Chemical Safety Reports are the main end point for data assessment under REACH (the European Community Regulation on chemicals and their safe use, concerning the Registration, Evaluation, Authorisation and