The presence of an abnormally large amount of earthy carbonates in a natural water is very undesirable. These can be removed also by adding a little soda to the water, where such addition is not likely to be objectionable; on standing the earthy salts are precipitated. Thus the magnesia and lime are replaced by soda, so that the water may be used for washing and cooking, but it is no better for drinking, since soda salts are nearly as purgative as the magnesia compounds. However, the carbonate of soda does not form any precipitate with citric or tartaric acid used in carbonated beverages as the carbonate of lime or magnesia, if present, would do, being entirely soluble. Therefore we rather prefer the application of soda, if no other more effective and unobjectionable remedy for purification, as alum, limewater, or boiling, is employed.