This section is from the book "A Treatise On Beverages or The Complete Practical Bottler", by Charles Herman Sulz. Also available from Amazon: A Treatise On Beverages.
Its Composition. - How Produced. - Its Absorption by Water. - An Interesting .Table. - Atmospheric Air should be Removed. - Weight of Carbonic Acid Gas. - Influence of Temperature and Pressure. - Its Effects.
The most important ingredient in the manufacture of carbonated waters, and that which gives them all their distinctive qualities, is, besides pure water, carbonic acid gas. All effervescent drinks depend for their refreshing qualities, their sparkling, prickling and excellent taste, on the carbonic acid gas impregnated with them. Carbonic acid gas must be perfectly pure, free of atmospheric air, and should not contain any bad odors, such as sulphuretted hydrogen, etc. As it may be very useful to those who deal so largely in it to know accurately its qualities and characteristics, we annex a few leading particulars extracted from a standard work on Chemistry ("Miller's Chemistry," London, 1868, Part II.).
"Carbonic acid gas is composed of carbon and oxygen in the following proportions:
Carbon . . . 27.28 Oxygen . . . 72.72
"Its chemical sign is C O2.
"Carbonic acid gas was originally termed 'fixed air,' from the circumstance of its having been discovered by Dr. Black in 1757, as a solid or fixed constituent in limestone, and from its becoming fixed or absorbed by solution of the caustic alkalies.
"The name of carbonic acid was given to it by Lavoisier, nearly twenty years later.
"Under the ordinary pressure of the atmosphere it is a colorless transparent gas, with a faintly acidulous smell and taste, and it turns blue litmus paper red. At the ordinary temperature the gas is soluble in about its own bulk of water (or in other words, a body of water will dissolve about its own bulk of gas), and its solubility increases if the pressure be increased; that is to say, that under a higher pressure the water will absorb more gas. But when the compression is suddenly removed, the gas escapes with brisk effervescence. Advantage is taken of this circumstance in the preparation of soda water, as it is called. One important point to be borne in mind, in connection with the combination of carbonic acid and water, is that the water absorbs a greater amount of gas at low temperatures than at higher ones. This is often lost sight of, and causes great practical difficulties and perplexities to those who overlook it. It is desirable that the factory, and especially the gasholder and the water supply, should be protected from the sun and kept as cool as possible. The temperature of the factory should, if possible, not exceed 50° F., and the lower it is, short of freezing, the better".
Carbonic acid, while unsuited for breathing, is highly beneficial when taken into the stomach, and is a valuable agent in preserving and restoring health.