The classification of water as food is based chiefly on its purity and palatability.

Hard And Soft Water

Water containing calcium (lime) or magnesium salts is known as hard water; and if it contains these salts in excess it is unsuited not only for drinking but for cooking and bathing, unless purified or softened. As only the carbonates can be expelled from the water, the purification is incomplete; chlorides and sulphates remain behind. For washing purposes the carbonate of lime may be precipitated by treating with lye, whereupon it rises to the surface and can be skimmed off. By adding soda to cooking water, a similar softening is obtained desirable in cooking vegetables, as they are toughened by the lime and sodium chloride. Finally, for drinking purposes hard water may be subjected to prolonged boiling and straining; by this means the carbonic acid is driven off and the lime is set free. It must be remembered that a water not suited for domestic uses may still be fit for drinking if not taken in great excess, because lime and magnesium are natural ingredients of the body.

In soft water only a small amount of salts are found and as a rule it is more desirable to use for cooking purposes, especially in the cooking of legumes or when the object is to extract the nourishment or flavor of food, as in making tea or soup, etc.

Rain water is naturally pure but devoid of any mineral content, which is sometimes a disadvantage. It is not very palatable. It should be remembered that the first part of a rain fall carries down with it dust and impurities from the air, but the latter part of a shower furnishes as pure water as can be found from any source.

Spring Water, well water, etc., vary greatly in the amount of mineral matter, organic matter, gases, etc., present. In many cases the mineral content or gas content is such as to confer a medicinal value. In other cases the mineral matter is a menace to health. In most ground-water there is organic matter which besides being undesirable in itself invites the presence of germs, which often threaten the health and safety of whole communities. Great care should be taken as to the location of a well; deep spring water and water from artesian wells is usually pure. City water is usually filtered through sand beds and otherwise purified; the law requires such waters to be frequently analyzed as to purity.

As water may dissolve the lead from pipes through which it flows, it should be allowed to run several minutes before using if it has not been recently run off (as after standing over night) to avoid the risk of lead poisoning.

Filtered Water is water freed from organic matter of all kinds. It should be pure and palatable. But filtered water as a rule cannot be depended upon for purity owing to the fact that the domestic filters require constant cleansing and serve to condense the impure organic matter which putrefies upon the filter and renders the water passed through them fouler in place of purer. Small filters screwed on faucets are of no value whatever. There are charcoal and porcelain filters on the market that are very good, but are not effective unless often and thoroughly cleansed. When there is the least doubt as to the purity of water it is best to boil it.

Boiled "Water"

Water simply sterilized by boiling and kept in bottles in a cool place is extensively used when there is suspicion as to its purity. It is rather unpalatable. Boiling renders harmless all the organic impurities and precipitates salts of lime. It must always be borne in mind that typhoid fever, cholera, dysentery and other pestilences are largely water-borne diseases, and whenever there is any suspicion that water is contaminated, the most available method for purification is boiling. Before filling the bottles, have them thoroughly cleansed and rinse with boiling hot water, as a few drops of unboiled water would be sufficient to contaminate the whole. To prevent breaking, place bottles in pan of warm water before pouring in the boiling water.

Distilled Water

This is water in its purest state. It is said by many authorities to be unsuited for a beverage because of total absence of mineral matter and gases, on account of which mineral matter is greedily abstracted from the walls of the stomach, thereby causing congestion and irritation. It is generally used for medicinal and chemical purposes. If employed as a beverage it should be aerated to improve the flavor.

Carbonated Waters

Ordinary water may be artificially charged with carbon dioxid, as soda water, etc. Among the most common carbonated waters (naturally charged) are Vichy, Apollinaris and Seltzer (effervescing waters) and Poland water (uneffervescing). These are valuable in case of fever and to tempt people to drink more water; also in relieving nausea and vomiting. They are used to advantage with acid drinks and to dilute alcoholic liquors. Carbonated water of any kind should not be taken in excess, as such waters are apt to produce indigestion, by retarding the action of the gastric juice.

Alkaline Mineral Waters are carbonated (naturally charged) and differ from ordinary water in the greater amount of gaseous (carbon dioxid and sulphuretted hydrogen) and solid matter (sodium chloride, potassium, magnesium, iron, sulphur, etc., etc.), which they contain. Some mineral waters have no medicinal value and are simply used for quenching thirst; others have purgative, laxative or diuretic effect. The following are a few examples of the latter class - Sulphur Spring, Saratoga, Vichy, Hunyadi, Londonderry, and Lithia Waters.

The benefit derived from the water cures so often prescribed is not usually from the water itself but from the change, treatment and quantity of water taken. Much benefit can be derived by following the same treatment at home.

Temperature Of Drinking Water

Luke-warm or tepid water (65° to 92° E.) which in theory should be most suited for drinking is insipid and even repugnant to most people. Hence as a beverage water is either taken warm (92° to 100° P.), hot (100° F. and over), cool (65° to 92° P.) or cold (32° to 65° F.). The taking of hot water in large quantities has been found of benefit for weak digestions and in much chronic. invalidism. It acts as a stimulant to gastric digestion; relieves thirst more quickly than cold water; is more quickly absorbed, and leaves the stomach sooner. Cool water is the normal beverage for quenching thirst. Ice water is unsuitable for all individuals when overheated, and with meals for dyspeptics and those in delicate health. Fever patients, however, may take it ad libitum; for most robust individuals who crave it with or without meals it seems to do no great harm, if taken slowly and in moderation. Its coldness acts as a natural check against overindulgence. It probably slows the movements of the stomach and as long as the stomach is chilled the action of the pepsin is curtailed since this acts best near blood temperature, but the arrest is only temporary. A small quantity of crushed ice is known to relieve nausea.