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
CSX milepost prefixes in Waycross, Georgia, 587 miles south of Richmond on the branch to Montgomery, Alabama (which splits near milepost 548 in Jesup). Three-letter prefixes are used for minor branches of these branches, or minor branches off the mainline - for instance ANA is the northernmost branch of AN. Before the ACL merged into the Seaboard Coast Line Railroad in 1967, none of the prefixes had the initial "A". The letters "I" and "Q" were skipped, and double-lettered prefixes (like KK, which would be AKK post-1967) were not used. A is given to the main line from Richmond, Virginia to Port of