It contains, in 100 parts, 88.8 parts of oxygen and i i.i parts of hydrogen. We know it in three different aggregates - as vapor, as fluid, and as ice. Being one of the chief means for dissolving the most heterogeneous solid substances, and being capable of mixing itself with most of the liquids, it is never found in nature perfectly pure; nor is this at all desirable, as chemically pure water would taste vapid.

Natural water, e. g., rain-water, contains ingredients that were taken from the atmosphere - as nitrogen, carbonic acid gas, dust, salts, germs of organisms, ammonia, nitric and nitrous acids, peroxide of hydrogen.

These ingredients are partly disposed of again by filtering through rocks and gravelly soil. Spring-water contains substances of the soil; these, varying according to the soil's composition, are useful, and in many cases indispensable for the organisms.

The sparkling of the water indicates the presence of gases, without which it is never refreshing. Boiling will drive out all gases, precipitate the bicarbonate of lime and some of the coagulable matters, and destroy some of the germs of disease. Solids - fixa - as we find in water, are chiefly combinations of calcium, magnesium, alkali metals, aluminium, iron, manganese in form of carbonates, chlorides, sulphates, silicates, etc., and organic particles.

Good and palatable drinking water should contain less than 10100 of these fixa; some of them are better not found at all, and if they are, they should be in the smallest possible proportions. The limit of lime is 1/5000; too great a percentage of magnesia is harmful. Organic particles should be not more than to require 3/10 to 6/10 % of oxygen for their oxidation, i. e., as a maximum 5/1000 %•

The reasons why waters not answering these requirements are doomed, are: Firstly, it is proven beyond any doubt that the spreading of epidemics is in the closest connection with the composition of water, which, having absorbed germs of disease on one place, deposited them on another; secondly, the presence of too great quantities of organic matter, as also of ammonia, nitric and nitrous acids, shows generally an impurity of the water - this being contaminated by filth from cesspools and other sources.

Water, by various methods, may be rid of much of its injurious matter, although a thorough purification is out of question. Filtering through charcoal or oxide of iron will secure water pure enough for use; nor will it lose much of its taste. For special purposes, f. i., for use in hospitals, it is advisable to boil the water first, to cool it, and to add, artificially, carbonic acid gas.

Spring waters, which have a large, and by the taste easily distinguishable, amount of salts, are used mostly for therapeutical purposes, some of them because being palatable and refreshing also instead of ordinary drinking water. We have to dwell only on the latter ones to which belong those having but a few of solid ingredients and dissolved carbonic acid gas, not under 40 vol. per cent, as f. i., Apollinaris, the waters of Heppingen and Dorotheenauer Spring at Carlsbad, etc.; likewise the waters containing alkalies and alkalic muriatic acids with a certain quantity of natrium bi-carbonicum and chloride of natrium, besides freely dissolved carbonic acid gas are frequently used as table waters, as those of Vichy, Giesshuebel, Rodna, Ems, Selters, etc.

The waters are either consumed at the springs or bottled; preparations containing their active ingredients, like the pastilles of Bilin, the Carlsbad Salt, etc., are shipped to all parts of the globe; these preparations must be dissolved according to prescription in a certain volume of water to secure the desired therapeutical effect.

Of higher importance, however, are the artificial mineral waters which, in harmony with the exact analysis of the natural waters, are prepared by saturating a solution of the corresponding salts under higher pressure with carbonic acid gas.

With these waters the greater or lesser amount of carbonic acid gas, the greater or lesser purity of the materials used for them, the greater or lesser safety in the emballage are utterly essential; therefore it should be borne in mind where to get these waters from; moreover, waters of certain compositions and established names, such as Vichy, etc., should be prepared under the supervision of expert chemists, and never be ordered from firms that stand under the control of quacks.