CARBONATE

any member of two classes of chemical compounds derived from carbonic acid or carbon dioxide (q.v.). The inorganic carbonates are salts of carbonic acid (H2CO3), containing the carbonate ion, CO2/3-, and ions of metals such as sodium or calcium. Inorganic carbonates comprise many minerals (see carbonate mineral) and are the principal constituents of limestones and dolomites; they also comprise the hard parts of many marine invertebrates. Organic carbonates are esters; that is, compounds in which the hydrogen atoms of carbonic acid have been replaced by carbon-containing combining groups such as ethyl, C2H5.