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 generation of carbonic acid gas is a question of vital importance to the mineral-water manufacturer, inasmuch as the purity of the gas affects considerably the flavor and sharpness of carbonated waters.
The process of generating and purifying it is not as thoroughly understood as it should be. Novices are apt to regard the flavoring of the various drinks as of more importance, and bend their energies to securing good results in this particular, giving scant attention to the effervescent quality of their waters. The average bottler has but a hazy idea of the proper manipulation of his carbonating apparatus, which is frequently as much a mystery after years of use as on the first day of its arrival. By this is meant, that while perfectly familiar with its operation, the " why and wherefore "of its workings remain an everlasting and unsolvable problem. This state of affairs may be attributed in no small measure to the inferior class of men that have at times embarked in the carbonating business. This assertion is made in no disparaging spirit toward the many highly intelligent and well-informed people now numbered among the fraternity. A marked improvement in this respect is noticeable in all parts of the country, and every year shows the advancement of progressive views and their practical application.
No branch of the business requires more care and skillful handling than that pertaining to the production and purification of gas. The process of making the gas is extremely simple. Sufficient water and marble dust, whiting, bi-carbonate of soda, or other suitable carbonate is placed in the generator, and a proper quantity of sulphuric acid is permitted to enter, which is mixed with the marble dust, etc., by means of an agitator; an effervescence takes place, that throws off the carbonic acid gas, which is forced by its own pressure into the purifiers, gasometers, eta, and thence into the fountains, cylinders or condensers, as the case may be. Despite the evident simplicity of the process, careless and ignorant operators frequently "charge up" without the slightest idea of the damage, delay and consequent annoyance and trouble they may cause by not observing the precautions invariably necessary in operating any and every style and make of apparatus. There may be different ways of admitting the vitriol, agitating the generator and checking the pressure, but all manufacturers of machinery are united in requesting that a fair amount of caution and care be exercised in priming or charging a generator. Not that there is any particular danger, but to prevent the clogging of pipes, caking of the carbonate and other troubles bound to arise when careless workmen are permitted around.
After the generator has received its charge of water and marble dust (which will be selected as the carbonate most commonly used in this country) and a small amount of acid has been admitted, the valve or plunger should be closed and the generator turned slowly. A bubbling of gas in the purifiers will be heard. The gauge attached indicates the exact state of affairs inside the generator. The pressure should be gradually increased, while keeping up the agitation at regular intervals, thus allowing a slow, easy flow of the gas. When the valve is very gradually opened for passing the gas into the fountains, say in the neighborhood of 145 to 150 pounds pressure, by adding more acid or increasing or diminishing the current of gas, a uniform pressure is preserved, which should not vary many pounds one way or the other. When this mode of procedure is followed no trouble will ensue from clogged pipes or contaminated beverages. But when the operator is slipshod or haphazard in his method of charging, and allows the gas to reach a considerable height in the generator before opening the valve leading into the purifier, which he does suddenly, the rush of gas is bound to carry over a portion of the charge, clogging up the apparatus and frequently carrying a portion of it clear over into the fountains or cylinders. Extremely careless carbonators allow the pressure to run up to over two hundred pounds, and then back to sixty or eighty, a practice reprehensible to the last degree, as such extremes strain the generator, force the gas over into the purifiers too rapidly and always choke up the pipes. A safe rule to follow is to maintain a uniform pressure, agitate the material slowly and regulate the flow of acid.
A sudden flow of gas from the generator has a tendency to carry over a portion of the acid and other deleterious material, which, were it not purified, would enter the fountain and contaminate its contents.
When the gas is, from accident or otherwise, allowed to rush through the pipes in a strong current, its purification is incomplete and has a tendency to cause ropiness.
The directions for operating the different styles of apparatus we have appended to the descriptive explanations in the foregoing part.