Also 8–9 carbonat. [a. F. carbonate, ad. mod.L. carbonātum ‘a carbonated (product),’ f. CARBON or L. carbōn-em + -ATE 1 c. Cf. CARBONATED.]
1. Chem. A salt of carbonic acid, a chemical compound formed by the union of carbonic acid with a base or basic oxide. These constitute a very numerous class of bodies, some of which, e.g., Carbonate of lime, Ca CO3, exist in great quantities in nature.
Since Carbonic acid (the hydrate), CH2O3 = 2 HO . CO, contains two atoms of replaceable hydrogen, there exist two sets of carbonates, viz. Normal Carbonates in which both atoms of H are replaced by a metal, and Hydrogen Carbonates, in which only one atom of H is so replaced. Thus normal sodium carbonate (carbonate of soda) 2 Na O . CO, hydrogen sodium carbonate (bicarbonate of soda) HO . NaO . CO.
1794. Pearson, in Phil. Trans., LXXXIV. 394. Carbonate of lime (chalk) readily dissolved, with effervescence, in the liquid.
1794. G. Adams, Nat. & Exp. Philos., I. App. 546. The alkaline carbonats are soluble in water.
1807. Marcet, in Phil. Trans., XCVII. 308. Common carbonat of magnesia.
1876. Page, Adv. Text-bk. Geol., iii. 70. The alkalis and alkaline carbonates attack many rocks with great facility.
1876. Harley, Mat. Med., 245. Carbonate of lead has been known from the highest antiquity.
2. ellipt. ‘The common term in the West for ores containing a considerable proportion of carbonate of lead. They are sometimes earthy or ochreous (soft carbonates), sometimes granular and comparatively free from iron (sand carbonates), and sometimes compact (hard carbonates)’ (Raymond, Mining Gloss.).
