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.
The American Carbonate Co., of New York, has introduced a new and improved method for obtaining the gas in absolute purity, by which the product is not dependent upon the uncertain and ofttimes impure natural gas, and by which no mineral acid is used. To make the gas, broken marble is heated in a kiln especially constructed for that purpose, to a sufficient temperature to drive the gas off. The generated gas passes from the kiln through the coolers and thence into the compressors, which reduces the gas to the liquid form. The refuse or by-product makes an excellent lime for building purposes. The exclusion of all impurities, such as sulphurous acid and nitrous oxides, which are always present in sulphuric acid, are said, therefore, to be absolutely secured by the heating process. A small quantity of iron or silica and traces of other substances are often contained in marble, which are not affected by the heat, but some are more or less affected when acid is used to generate the gas.
The compressed or liquefied gas is stored and shipped in a strong wrought-iron cylinder, fitted at one end with an outlet valve, tested to four thousand pounds hydrostatic (water) pressure, which precludes any possible danger by explosion. As a matter of fact, there is no explosive power attached to carbonic acid gas in its pure state, in the same sense as gunpowder or dynamite and similar well-known explosives. Of course, there is a strong pressure in the cylinder, and if anything should happen, such as an unusual degree of heat, as in case of fire, or the cylinders were too weak (which the high testing pressure absolutely prevents a possibility of), the gas would escape with a hissing noise through the fracture, but the vessel would otherwise remain intact and not be hurled about with great violence, as in boiler or the ordinary generator explosions.
Above the liquid in the bottle, within two or three inches of the top, is a volume of carbonic acid gas, corresponding in pressure to the ordinary temperature outside, which escapes when the valve is opened. As previously stated, the natural state of carbonic acid is the gaseous form, and cannot be held in any other condition but by pressure. Therefore, when the pressure is removed from the liquid it immediately resumes its natural or gaseous state. By laying the bottle or flask on its side, placing a bag over the valve, which is opened to the full extent, the liquid acid flows out freely and assumes a snow-like mass, which slowly evaporates. A pressure of one thousand pounds to the square inch prevails during this interesting operation, and is accompanied by a sharp, hissing sound.
Thus far the material and its manufacture have been treated upon to the entire exclusion of the uses to which it is and has been adopted in the industrial arts. Its practical applications are manifold and important, and in Germany the manufacture of liquid carbonic acid has assumed large proportions. The American company is convinced that its future in this country is big with promise, and feels assured that the extensive plant it has erected for the production of the liquid gas for various commercial purposes will be taxed to its utmost in a short time, when the nature, capabilities and quality of its product are fully understood.
The method of generating gas for the manufacture of carbonated waters is held to be defective, and the gas produced not as pure as it should be. A stock of gas ready at hand, of absolute purity and uniform quality, is certainly a desideratum, and this the "liquid carbonate," as the American Carbonate Co. felicitously terms its liquid carbonic acid, proposes to accomplish. No extra machinery is required for its use; on the contrary, the labor of obtaining the gas by the present methods, and the cost and danger of handling the gas-producing materials and apparatus, are entirely obviated. A bottle of the liquid gas, a mixing cylinder and a pressure-registering gauge are all the appliances needed. In fact, any style of carbonating apparatus can be readily adapted for using the liquefied gas. When the cylinder containing the liquid carbonic acid is attached to the fountain, rapid evaporation produces an intense cold, which reduces the temperature of the water to be charged, in a corresponding degree, and the absorption of the gas is more rapidly and easily accomplished at a much less pressure than is necessary by the ordinary apparatus, the natural expansion of the gas contributing the necessary pressure required for saturating the water. The presence of atmospheric air in the charging cylinders or fountains is and has always been a detriment to the proper gasing of the water; and the entire absence of air from liquid carbonic acid cannot but be advantageous in the preparation of true mineral waters and highly carbonated saccharine beverages.
The whole process is very simple, and in the next chapter on apparatus we append cuts and explanation of the appli-cation of the liquid carbonic acid. From other parts of the globe, Europe and Australia, very fair results are reported by its application. Our manufacturers of machinery are cautious and conservative respecting the practicability of the liquefied gas, but if it should prove successful, they will not be the last ones to advocate its adoption.