Mineral waters are frequently taken as substitutes for ordinary water. They differ from ordinary water in the greater amount of gaseous and solid matters they contain. The gaseous constituents are mainly carbonic acid gas, and in much lesser degrees sulphide of hydrogen; the solid constituents are salts of sodium, potassium, magnesium, aluminium, iron, iodine, bromine, chlorine, and sulphur. Some waters have a purgative action, others a laxative, and others a diuretic effect, according to their composition. For ordinary table use a water must not contain more than 1 per cent, of mineral matter, otherwise the specific effect of the saline ingredients present may be obtained.

The natural mineral waters most largely used as table-waters in this country are Apollinaris, Johannis, Seltzer, Kronthal, St Galviier, and Vicky (Celestin). These are all alkaline, well-aerated waters, containing carbonate of lime and soda, and also sodium chloride. According to their chemical composition, mineral waters may be classified as follows: -

Purgative,

Laxative,

Diuretic and medicinal.

The purgative waters are characterised by the large amount of sodium sulphate and magnesium sulphate in this composition, the chief among these being Apenta, Hunjadi Janos, Friederichshall, Kissingen, Franz Josef. These are bitter waters.

The laxative waters are less rich in the salts which induce active peristalsis of the bowels. These include waters of Harrogate, Kissingen, Kronthal, Seltzer, Wiesbaden, Contrexeville. These are relatively rich in sodium chloride.

The diuretic and medicinal waters include the ordinary table-waters above mentioned, also special waters rich in bromine, iodine, iron, and sulphur, which are found in different health resorts.

Uses Of Mineral Waters

When taken before meals, waters containing carbonic acid have a soothing effect on the gastric mucous membrane At the same time, carbonic acid acts as a stimulant to the movements of the stomach, and may thus aid digestion. If taken in excess, all carbonated waters are apt to produce indigestion, with flatulent distension of the stomach or bowel. The slight alkalinity of some of the table-waters has led to their being used to neutralise the acidity of some of the more acid wines. In practice we find that many patients will not readily take ordinary water, but are willing to take an alkaline table-water. Probably the greatest use of aerated and simple mineral water in therapeutics is to be found in the treatment of this class of patient. Many of the natural mineral waters have been found to be distinctly radio-active, and recent observations suggest that some therapeutic value may attach to this property. In this respect the natural mineral waters have a distinct advantage over the artifically prepared waters. The sweetened mineral waters have no therapeutic value; they may be pleasant drinks to people in health, but should be avoided by gouty and rheumatic subjects, on account of the acid and sugar present in their composition.