The Collaborative International Dictionary
supercarbonate
Bicarbonate \Bi*car"bon*ate\, n. [Pref. bi- + carbonate.] (Chem.) A carbonate in which but half the hydrogen of the acid is replaced by a positive element or radical, thus making the proportion of the acid to the positive or basic portion twice what it is in the normal carbonates; an acid carbonate; -- sometimes called supercarbonate.
Wiktionary
supercarbonate
n. (context chemistry obsolete English) bicarbonate