Carbonic acid gas is a powerful preservative. We have made the observation, that a beverage from which the atmospheric air has been expelled, according to the rules we explained on page 122, and that could be consequently well and highly charged with carbonic acid gas, and carefully bottled so as to prevent any loss of gas, has never become ropy. Carbonic acid gas is a powerful destroyer of germs of all kinds, and as long as it is combined with the beverage, and is prevented from escaping by carefully stoppering and treating the bottles, this much is sure - no fungus can develop - and we are supported in this opinion by experiments carefully made, and by the experiments made with water by Dr. Phelp, and stated in the Chapter on Water, page 64 and following. The germs are checked or killed by the carbonic acid, but the few possibly remaining start activity proportionally to the loss of the gas, to which too little attention generally is paid.

We are led to put down as chief preservative, and remedy against ropiness, the exclusion of atmospheric air, and a perfect gasing of the beverage.

Other important preventives should be exercised. The first one is thorough cleanliness in all stages of carbonating, scalding and rinsing all apparatus, accessories, connections, etc. Another is a clean and properly ventilated work-shop. The next is to employ only preserved and carefully filtered fruit acids, which in themselves are able to introduce fungoid growth developing in the beverage. All other materials, especially water, should be pure, and all gummy preparations intended to produce foam should be freshly and carefully prepared, as they are well apt to be a carrier of fungus into the beverage. The use of glucose, containing most invariably dextrine, will cause a sediment, if nothing worse, and is easily fermentable.

These are the chief requirements for preventing ropiness, and will prevent it. It is also prevented by a very small quantity of carbolic or sulphurous acid or by a considerable proportion of alcohol, but these means are inopportune, the former on account of their odor. Salicylic acid and peroxide of hydrogen are about the only well-known anti-ferments or preservatives used for carbonades, but a well-gased beverage preserves itself, and these anti-ferments, when admitted, may check the development of any ferment, in case the gas escapes by improper stoppering or other carelessness.