Emily Dickinson Lexicon

SO'DA, n. [G. soda; D. souda; It. soda; Sp. soda or sosa, glasswort, barilla.]

1. The protoxyd of the metal sodium, formerly called, though not appropriately, mineral alkali. It has likewise been called fixed alkali, in contradistinction from ammonia, which is a volatile alkali.
2. The carbonate of soda, formerly called natron, obtained by lixiviating the ashes of marine plants. In this state however, it is never pure.