Composition of Water
Water is not, as was previously supposed, an elementary substance. In 1781 it was shown by Cavendish that it consisted of two parts of hydrogen and one part of oxygen (H2O), and that it could be made synthetically by combining hydrogen and oxygen in this proportion, and that it could be separated analytically by various methods into its component parts.
By volume, water is composed of two parts of hydrogen to one part of oxygen; by weight, one part of hydrogen to eight parts of oxygen. However, pure water does not exist in Nature since water is a universal solvent and in Nature it comes in contact with so many substances; therefore, it contains many substances in solution. Chemically pure water is found only in the chemist’s flask.
Water is a liquid which is clear, colorless and odorless. To be palatable it should be cool, soft, well aerated and free from sediment and suspended impurities. One cannot judge the purity of water by any one of these qualities, for water that is palatable and gives no offense upon drinking might be polluted with that which would be detrimental to health. The palatability of water may be due to the carbonic acid present, which results from the decomposition of products contained in it.
The carbon dioxide, which is present in rain water, is obtained from the air through which the rain passes. Carbon dioxide is also taken up by the water as it percolates through ground covered with vegetation. The presence of this gas increases the solvent powers of the water. Water may also contain metal in solution such as iron, arsenic and copper.
The important foreign ingredients in water are those of organic origin, such as microscopic plants, vegetable fungi, detritus of vegetable life, minute insects, infusoria, ova of insects, minute parasites, and animal debris. Water usually contains millions of various micro-organisms, mostly harmless, although at times it may also contain so-called pathogenic germs.