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.
Carbonating of Water the Radical Agent to Destroy Organisms. - Scientific inquiry has not exhausted the possibilities of carbonic acid gas in its relation to beverages. A general knowledge of its imparting pungency and palatableness to carbonated waters prevails, but beyond that the practical carbonator has not investigated. Probably the growth of organic life in water is also a matter of conjecture, and as both are subjects of more than passing moment to manufacturers of carbonated drinks, the appended experiments, observations and comments of Dr. T. Leone, a chemist of acknowledged European reputation, will prove interesting and instructive:
"The analysis of drinking waters, until the most recent times, has been in the exclusive competence of chemists. The existence of minute microscopic living organisms in drinking waters has been known, but the want of suitable methods has always compelled analysts either not to occupy themselves with this question at all, or to do it in a perfunctory manner, including these beings in the determination of the organic matter. But the existence in nature of pathogenic organisms (that is, organisms that render the water unwholesome and impure) being recognized and confirmed, has already passed into the domain of science, and the probability that some of these may be found in waters enables us to foresee what a part of its territory chemistry must, in these researches, yield up to bacteriology, as soon as this new science shall have reached its full development. Many experimentalists who have occupied themselves with the study of microbia have contented themselves with the summary appreciation of the value of a drinking water according to the number of microbia present capable of producing "colonies" in gelatin. It is believed that the bacteria derived from putrescent animal matter produce colonies which liquefy gelatin. From the number of such colonies it is believed that we may form an opinion as to the greater or less corruption of a water. But the greater part of such experimentalists think that in these researches we have not been guided by an exact conception of the nature of these microbia. Indeed, since the majority of such experimentalists have not taken account in such researches of the time which has elapsed from the moment in which the water was obtained to that when it was experimented upon, and since these experimentalists have ascribed to a water thousands and thousands of microbia in a few drops - a water which may have required two or three days' journey from its source to the point where it comes to be examined - it is to be supposed that these experimentalists have disregarded the possibility that the purest drinking water may be a good medium for the culture of microbia. What value is to be conceded to these researches will be seen from what will be explained below. "The cultivations were made upon plates of glass, upon which the gelatin was spread. The preparation of the 'cultures' was effected at a temperature below 30°, and all the instruments used which came in contact with the cultures, or might have any connection with them, were duly sterilized, either by heat or by a solution of sublimate. For the enumeration of the colonies, the culture, placed on a black ground, was covered with a plate of glass, and the colonies were enumerated with the aid of the microscope. An appreciation of drinking waters according to the criteria previously put forward, depending on the number of the colonies in general, or in particular on the number of those which liquefy gelatin, it was my first intention to examine if a drinking water, although the purest, was such a nutrient medium for microbia as to render variable, and consequently erroneous, such an appreciation if the research is not immediately executed. To this end, waters from different sources were examined, the results leading all to the same conclusion. I give those only yielded by the water supply recently introduced into the city of Munich, as this water may be taken as a type of the purest drinking waters. It contains not a trace of nitrates, nitrites, or am-moniacal salts; and the organic matter contained in a quart of the water is infinitesimal. This water was brought to a cock connected with a main in which the water, coming directly from the great reservoir, was flowing continually. The cock was sterilized by the heat of a lamp. The recipient vessels were always washed with strong sulphuric acid, then with distilled water, and were then sterilized by being heated for an hour to 150°. These recipients, filled to two-thirds and closed with plugs of cotton-wool, likewise sterilized, were left at rest in an atmosphere where the temperature ranged from 14° to 18°. For brevity's sake I omit the details of the researches, and pass directly to an exposition of the results, confining myself to say that the figure given must be considered as the mean of the values furnished by such cultures. The following are the results: 5
"The Maugfall water arrives at Munich with five microbia per cubic centimeter (about seventeen minims or drops). After twenty-four hours, being left under the conditions above described, the number of microbia is found to have risen to more than a hundred per cubic centimeter. In two days the figure reaches 10,500. In three days, 67,000. In four days, 315,000. And on the fifth day there were more than half a million of microbia per cubic centimeter. So rapid and considerable an increase of microbia in waters I find noticed only in a very recent publication by Dr. Cramer, Professor at the University of Zurich. Professor Cramer, in his "Memoir on the Waters of the City of Zurich," proves that the microbia in such waters increase rapidly on standing. But it must be observed that the action of repose has no influence on the increase of the microbia. The experiments which follow prove that the microbia in drinking waters in movement multiply with the same rapidity, and in the same proportion, as if the said waters were at rest. For these experiments were used glass tubes. They were washed with strong sulphuric acid, then with distilled water, and were then sterilized for an hour at 100° (in an atmosphere of steam). These tubes were sealed at the lamp, after being half filled with the above-mentioned Maugfall water, and were then arranged perpendicularly to the axle of a wheel, so that the angle was intersected by the middle part of the tubes. The wheel was set in continuous motion by a current of water, and the apparatus was so arranged that the entire water in the tubes was not at rest for an instant. The experiment being thus arranged, I made, from time to time, examinations of the quantity of microbia contained in the water. I shall spare the description of the detailed results of these researches, which do not need to be repeated. Approximately the same figures were found that were obtained above. The variation of the number of micro-organisms in the water in motion follows the same course as that of the same water when at rest. In both cases the number of the microbia reached on the fifth day the same maximum, and then decreased. On continuing the research, I found that on the tenth day the number of the microbia had fallen to 300,000, in a month to 120,000, and finally, in six months, the water contained only 95 microbia per cubic centimeter.