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 purification of carbonic acid gas has thus far not received so much attention from the bottlers and other beverage manufacturers as it deserves, and which it should receive as one of the main factors in the manufacture of carbonated beverages; it is one of those factors which, although unavoidable, is insignificantly looked upon, and in our estimation should receive as much, if not more, attention than either of the others that are required for the same purpose. One may be ever so cautious in the purification of waters and preparation of syrups;, and nevertheless be unsuccessful in bringing his beverage to a standard quality, when proper consideration in the purification of carbonic acid gas is not observed.
The modes of purifying carbonic acid are various. One of the singular methods was an apparatus for the production of carbonic acid gas, a generator - whether manufactured yet or not we don't know - that had no extra purifier attached or connected, whatever, and yet delivers a fine quality of purified gas. This apparatus was so ingeniously arranged, that the entire carbonic acid gas passed through a large column of alkali liquid from which it was produced, and of which there was a surplus continually on hand.
The dry purifier for carbonic acid, another singular mode, consisted of a vessel containing charcoal, or alkali or both; this once sought reputation among the bottlers, but was soon discarded, owing to its impracticability. The purification of carbonic acid, has, therefore, remained with water, which was originally resorted to, and in the writer's opinion, the purification will not be deviated therefrom, save that improvements will be made thereon, mechanically to the device, and chemically by additions to the water.