Carbonades should contain no foreign salts, and especially no salts of iron or earthy oxides. We have already in a former Chapter referred to the importance to the bottlers, that the water they use should not contain an excessive amount of iron, as this metal.has a very deleterious action upon the flavoring compounds used in the preparation of the beverage, mars their delicate flavor, and in some cases entirely destroys it. Iron will turn beverages, such as prepared from bark extracts, containing tannin, inky and dark. The tannin may also be extracted from the corks employed in stoppering the bottle (see page 386). Test for iron in the water, and, if present, remove it as directed on pages 24 and 85 of this work.

The disagreeable odor, suggesting that of rotten eggs, occasionally noticed in carbonated beverages, is often due to decomposition of ultramarine in the sugar used for syrups (apply the tests given for sugar), or it may also originate from using unprotected patent (rubber) stoppers, which contain sulphur from the process of their vulcanization, and then furthermore it may be due to the presence of sulphur in water.

If the fountains are recklessly charged, and the water from the gas-washers are discharged into the fountains, and consequently enter into the beverage, a bad odor will likewise adhere to the goods, as in this water, with its chemical ingredients for purifying the gas, are absorbed the bituminous, sulphuretted and other gases from impure carbonates, and nitrogenous or sulphurous gases from impure acid. It will also be contaminated from impure carbonic acid gas, when carelessly generated and imperfectly purified. If sulphuric acid from the generator has passed over into the fountains, or if sulphuric acid is present in the beverage by the use of inferior glucose, the delicate flavors are impaired, aniline and cochineal colors fade entirely or but partially, thus indicating approximately the proportion of contamination by sulphuric acid.

The presence of lime in water neutralizes to some degree the acidulous taste of the beverage, and tartaric acid causes a precipitate (see Sediments).

The deleterious effects of light upon beverages when in colorless bottles, and exposed for some time to the light, we have mentioned on page 363, and refer thereto.