Aqua Acidi Carbonici.—Carbonic Acid Water.
SYNONYMS: Soda water, Mineral water, Artificial Seltzer water, Aqua carbonica.
Preparation.—This is prepared by saturating water under pressure with carbonic acid gas (see Acidum Carbonicum (not scanned)), generated by the action of diluted sulphuric acid on pulverized marble by means of an apparatus manufactured for the purpose. Five or six volumes of gas may thus be condensed in 1 volume of water.
History and Description.—At the ordinary temperature and pressure of the atmosphere, 1 volume of water absorbs 1 volume of carbonic acid gas, and acquires a specific gravity of 1.0018. By doubling the pressure, the quantity of gas absorbed by the water is doubled, and so on for other degrees of pressure; for, according to Henry's law, the quantity of gas forced into the water is directly as the pressure (P.). Thus, for water to absorb 5 times its bulk of this gas, a pressure of 5 atmospheres must be used.
The "soda water" of commerce, the well-known summer beverage, is merely a carbonic acid water, rendered more palatable by the use of some aromatic or agreeable syrup; when the carbonated water and syrup are mixed and bottled, it is then known by the name of "mineral water." Water containing carbonic acid gas is very effervescent, has a pleasant, tingling, slightly acidulous taste, and an acid reaction. The vessels containing it should be strong, and perfectly airtight, and kept in a cold place, otherwise the gas will escape, and the water lose its sparkling activity. Too much care can not be taken to avoid metallic impurities, especially lead, which should not be used at all where the carbonic acid water can come in contact with it; the pipes leading from the fountain should be made either of block tin or gutta-percha. The fountain containing this water, if made of copper, should be well lined with tin, and should be carefully examined every season before using it. The glass-lined iron fountains are preferable. Ammonium sulphide or hydrogen sulphide should not be discolored by carbonic acid water.
Action and Medical Uses.—Carbonic acid water is a refreshing, refrigerant beverage, useful to allay thirst, check nausea, and promote diuresis. It may be used in fevers, inflammatory diseases, chronic inflammation of the stomach, vomiting of pregnant females, etc.; and may be taken 3 or 4 times daily, in doses of from 3 to 6 fluid ounces.