All of this is not available, for carbonic acid is present as such in solution, as bicarbonate (of magnesium mainly) and as normal carbonate.
The bicarbonate forms large monoclinic prisms, permanent in the air.
Ammonia is found in small quantities as the carbonate in the atmosphere, being produced from the putrefaction of nitrogenous animal and vegetable matter; ammonium salts are also found in small quantities in rain-water, whilst ammonium chloride (sal-ammoniac) and ammonium sulphate are found in volcanic districts; and crystals of ammonium bicarbonate have been found in Patagonian guano.
There the reaction mentioned above takes place, and Owing to the concentration of the liquid the sodium bicarbonate formed is to a great extent precipitated in the shape of small crystals, forming with the mother-liquor a thin magma.
It possesses a strong ammoniacal smell, and on digestion with alcohol the carbamate is dissolved and a residue of ammonium bicarbonate is left; a similar decomposition taking place when the sesquicarbonate is exposed to air.
Chemically pure carbonate of potash is best prepared by igniting pure bicarbonate (see below) in iron or (better) in silver or platinum vessels, or else by calcining pure cream of tartar.
Amongst the most celebrated saline waters are those of Carlsbad, which contain sulphate of soda and bicarbonate of soda.
A lotion of sodium bicarbonate is useful to allay itching.
Solution of calcium bicarbonate becomes with gallic acid, on exposure to the air, of a dark blue colour.
The water in shallow seas, off the shores of islands or in lagoons, is saturated with calcium bicarbonate and if the amount of carbonic acid in solution be reduced by any means, normal carbonate must be precipitated.