Hard and Soft Water
The question of hard and soft water is one that must of necessity receive some consideration, but it is of more importance from an economic standpoint than from a sanitary standpoint. Soft water is generally considered to be more desirable for drinking purposes, and it is certainly more desirable for cooking. From an economical standpoint, soft water is more preferable as the hard water requires more soap to produce a lather.
Hardness of water is spoken of as being temporary or permanent. If the water remains hard after having been boiled it is known as permanently hard water. Hardness of water is due to the presence of the soluble salts of the alkaline earth metals, especially calcium and magnesium. Temporary hardness is due to calcium or magnesium carbonate held in solution as a bicarbonate by the dissolved carbon dioxide. The hardness is temporary because the carbon dioxide is driven off by boiling, and the soluble bicarbonates are precipitated as insoluble carbonates.
Permanent hardness, on the other hand, is due mainly to sulphates and chlorides of calcium or magnesium. These salts are stable and therefore are not precipitated by boiling.