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.
When First Made. - How it is Made. - No Danger of Explosion. - A Simple Process. - It can be Used for Various Things.
Mr. A. Convert writes in the National Bottlers' Gazette on this subject as follows:
"Although the well-known natural philosopher Faraday, in 1823, succeeded in condensing the carbonic acid gas to a liquid, it remained for our time to make a practical use of this article. The carbonic acid, as generally known, is, in its ordinary state and at ordinary pressure, a colorless gas; but by a pressure of about fifty to sixty atmospheres (which requires powerful machinery - one atmosphere 14.7 pounds to the square inch), it can be condensed to a very perceptible liquid, which does not mix with water, but floats on it like oil. In the open air it rapidly evaporates, generating a temperature of - 79° Centigrade or 174° Fahr. below zero, congealing then to a snowy white substance, which can be held in the hand for a while if it is not grasped too tightly. For, by the continuous rapid evaporation, there is a layer of gas around the solid mass, which prevents immediate contact with the skin; but if pressed tightly it causes a pain, like touching red-hot iron, and provokes a blister.
"Now, considering the fact that the expense of the materials for manufacturing carbonic acid in those comparatively small quantities used to manufacture carbonated drinks are considerably increased by freight, spoiling, etc., and that the gas cannot be made valuable in proportion to the cost of its generation, it occurs to me that it can be manufactured on a large scale, and by condensing it to a liquid it could be shipped cheaply and easily to any point, and employed with greater economy than as now manufactured. Besides this, a large percentage of manufacturing expenses are saved, trouble avoided, uniformity in quality is obtained and every kind of waste is avoided.
"The compressed gas is manufactured already in three factories in Germany, one of which uses natural gas as it comes out of the earth. The gas (the manufactured as well as the artificial) must be carefully purified and dried, and is then compressed with the aid of strong pumps. During the condensing process a great deal of heat is liberated, and the gas must be continually cooled, which is easily done by a cold liquid streaming along outside of the pipes. The liquid is transported in strong iron flasks, similar to our fountains, containing about sixteen pounds of liquid acid, equal to one thousand gallons of the gas. This method guarantees a thoroughly purified gas in itself, inasmuch as a poor quality could only be liquefied by an exceedingly heavy pressure, if it could be done at all. The advantages of an absolutely pure gas, such as this process would insure, are of more importance and value than a great many manufacturers of soda water may think; especially for making artificial mineral waters, in which the presence of atmospheric air leads to many inconveniences. By the use of this preparation a comparatively large quantity of carbonated water may be manufactured in a very short time.
"The necessary apparatus for using the liquid acid in the bottling trade is, of course, very simple, as the present arrangements for manufacturing the gas are not needed. The new machinery would consist of a mixing cylinder, and the liquid carbonic acid bottle. This latter is connected with the mixing cylinder by a delivery valve; an ordinary gauge indicates the pressure, and a safety-valve prevents any dangerous eventuality. After the mixing cylinder is provided with the necessary water, ingredients, etc., the valve between the liquid carbonic acid bottle and mixer is opened and the water saturated with the gas. As soon as the water is bottled, the mixer is filled again and the remaining gas used for the new filling".
This is only possible on pump apparatus; on others the remaining gas must be allowed to escape before the fountains can be filled again. The expense of manufacturing 250 bottles of mineral water in Germany amounts to about one dollar. If this method could be profitably adopted in this country it might bring about a radical change in the trade. The practical principles of liquefying carbonic acid gas we may consider thus:
A volume of water, at 60° Fahr., will absorb or dissolve and hold in solution one volume of gas, if thoroughly agitated. Now, put this volume of water holding the gas in solution in a receiver or fountain furnished with an agitator and pressure gauge, and force by proper means another volume of gas into the water, and thoroughly agitate. The gauge will then indicate fifteen pounds per square inch (the pressure required to confine an additional atmosphere or volume). Now, force in another volume of gas under the same conditions, and the gauge will indicate thirty pounds per square inch, and so on increasing fifteen pounds pressure for each additional volume of gas until the liquefying point or pressure is reached, which is about 500 to 800 pounds per square inch, according to the temperature. Now, a complete change of affairs takes place, for the greater part of the gas that has been accumulating in the water, and now amounts to thirty-five or fifty volumes, is suddenly forced or squeezed out, and will float on the surface like oil - the water under these conditions acting like a sponge, absorbing and storing the gas in its gaseous state, and then separating it in its anhydrous or liquid condition under this high pressure, insoluble in water, and of strange and peculiar properties.
This was the commercial liquid acid that has been thrown on the market with crude and defective apparatus to utilize the same for bottling purposes. A German company, about two years ago, made the first attempt to furnish the compressed gas to the American trade, on a basis commensurate with commercial purposes, but failed by reason of its ignorance respecting the requirements of the carbonating industry here. The practical application of liquid carbonic acid was never fully demonstrated by this concern, and its exertions were, therefore, viewed with apathy by the trade.