n. Carbureted hydrogen gas.n. In modern chemistry and mineralogy, an acid carbonate or carbonate of hydrogen and a metal: as, hydrocarbonate of magnesia (magnesium acid carbonate), H2Mg (CO3)2; also, but improperly, applied to a compound of a metal with hydroxyl and the radical of carbonic acid: as, hydrocarbonate of copper (of the mineral malachite) equals copper hydroxycarbonate, Cu2.(HO)2.CO3.