CARBONATES

(salt of carbonic acid), widely distributed in nature, commonest being calcium carbonate (Ca |CO:;), e.g. limestone, chalk, marble; all insoluble except those of alkali metals; decomposed by heat into carbon dioxide and the metallic oxide. Bicarbonate is @ salt in which only one of the hydro-. atoms of the acid is displaced, (¢.g.) aHCoO:;, an acid c.