|Of all compound substances occurring on the earth in a fairly pure condition, water is by far the most abundant. Not only does it exist in immense quantities in seas, rivers, glaciers, and lakes, but it is also remarkably widespread as a necessary constituent of the tissue of all living organisms whether animal or vegetable. It is also present as vapour in the atmosphere, whence it separates as clouds and rain. Some minerals, for example clay, also contain very appreciable quantities of this substance in combination. |
Although there is a possibility that the compound nature of water was realised by the Chinese at a very early date, in Europe the substance was regarded as an elementary substance, Aristotle grouping it with fire, air, and earth, as one of the basic or fundamental elementary bodies composing the universe. And so it remained until the latter portion of the eighteenth century when Cavendish, c. 1781, demonstrated its formation by the combination of hydrogen and oxygen either by burning or explosion when the gases disappeared in the approximate ratio of 2:1 by volume. A year or so later, Lavoisier effected the synthesis from oxygen and hydrogen, the latter of which he learned to obtain from steam by the action of heated iron. Almost simultaneously an investigation was made by Monge, who demonstrated the combination of two volumes of hydrogen with one volume of oxygen when a mixture was exploded, and from this result, together with a knowledge of the density of the gases, calculated the relative proportions by weight. On account of the presence of moisture in the gases the latter result was inaccurate, but the method is of interest as anticipating the procedure adopted later by Scott and Morley in their well-known experiments. In 1800 Nicholson and Carlisle effected the quantitative analysis of water by the passage of an electric current, an experiment which, as a proof of the composition, is not as satisfactory as might be wished because it is not possible with pure water, but requires the presence of small quantities of an electrolyte. Hence the decomposition is actually a secondary result dependent on the interaction of the water with the discharged ions of the electrolytic impurity.
|For domestic and ordinary chemical purposes water is invariably obtained by the purification of natural waters from various sources. Enormous quantities are required by civilised communities, as is evident from the accompanying data giving the average number of gallons consumed per head per day in the cities named: |
The above figures, of course, refer to the consumption of purified water for all purposes, and not merely for domestic use.
A convenient method for classifying natural waters is that adopted for potable or domestic supplies. Such a classification must be based largely upon local conditions of climate, population, etc. For example, waters that would have been perfectly wholesome a century ago may now be suspicious and even dangerous, in consequence of the enormous increase in population. Bearing these reservations in mind, the following scheme is reasonably applicable to British waters:
Classification of Portable waters
|Surface, from cultivated areas|
Spring water, particularly that derived from deep-seated springs, is usually beautifully clear and sparkling. The clearness is mainly due to thorough filtering during percolation through the soil, whilst the sparkle is caused by the presence of gases, mainly carbon dioxide, in solution. The temperatures of different springs may vary considerably. Water from deep springs is usually cold, whilst that from shallow springs varies with the seasons. Should the temperature of the water be appreciably above that of the atmosphere the spring is termed a thermal spring. Typical thermal waters in England are those at Bath (Somerset), the temperature of the different springs ranging from 31° C. (88° F.) to 50° C. (122° F.). The springs supplying the Corporation baths are stated1 to yield upwards of half a million gallons of water per day at 45° C. (113° F.). At Coulsworthy (Shropshire) the temperature is 11° C. (52° F.), that is, the waters are warmer in winter but cooler in summer than the average temperature of the atmosphere. The Bath waters are aerated and sold in bottles as sulis water.
Very frequently deep-spring waters contain dissolved salts which impart to them characteristic properties. Such springs as yield these are termed mineral springs, and are classified according to the nature of the dissolved impurities. Many towns owe their popularity as health resorts entirely to the reputed medicinal properties of their mineral waters. It is not improbable that many of the curative properties are either due to, or enhanced by, the presence of radioactive substances, and this would account for the well-known fact that artificially prepared mineral waters do not always possess the same medicinal values as the natural waters. Radium or radioactive material, for example, has been discovered in the springs at Bath and Buxton, in this country; numerous other springs in France, Spain, the Jura mountains, Tuscany, Alps, Switzerland, Italy, Austria, Tyrol, Silesia, Bohemia, Indiana, at Carlsbad, the Taunus, Wiesbaden, Kissingen, Durkheim, and other parts of Germany, Hungary, Norway, Sweden, Russia, Roumania, Greece, Canada, Yellowstone Park, Colorado, New York, Canary Islands, The Philippines, Iceland, and Sardinia.
The actual amount of radioactive material in the waters is of course infinitesimal, being of the order, in some typical cases, of 10-11 grams per litre, whilst in others it is very much less. The springs at Bagneres de Luchon (France) are amongst the most radioactive in the world, and contain from 0.4 to 41.5 millimicrocuries of radium emanation per litre, equivalent to from 4×10-10 to 4.15×10-8 gram of radium per litre.
The term mineral spring has also been extended to include certain springs containing very little, if any, more than the normal amount of dissolved material, but which are regarded as possessing medicinal properties. Such, for example, are the Buxton and Malvern waters.
A convenient method of classifying mineral waters is as follows:
The following analyses of various well-known spring and spa waters are characteristic:
- Muriated. - These contain chiefly sodium chloride with varying amounts of the chlorides of potassium, calcium, and magnesium. The Droitwich (Worcestershire) and two of the Cheltenham (Pittville and Lansdown) springs are characterised by their high content of sodium chloride, the waters being in considerable demand for rheumatic and sciatic affections. The Airthrey Waters (Bridge of Allan, Scotland) closely resemble many continental spa waters, and contain chlorides of calcium and magnesium as well as common salt.
- Sulphatic waters contain sulphates mainly as sodium, calcium, and magnesium salts, and are consequently aperient. E.g., Bath, Cheltenham (Chadnor Villa Well), and Scarborough. If ferrous sulphate is present, as at Trefriw (Carnarvon, N. Wales), the waters are termed -
- Chalybeate or Ferruginous. - Usually these waters contain iron in solution, as the soluble ferrous hydrogen carbonate FeH2(CO3)2. Tunbridge Wells, Flitwick (Beds), Cheltenham (Cambray Well), and Leamington, are well-known examples. The corresponding manganous salt may also be present.
- Carbonated waters may hold sodium hydrogen carbonate, NaHCO3, in solution, as their chief salt, as for example in Apollinaris water. Magnesian waters contain magnesium hydrogen carbonate, MgH2(CO3)2, and calcareous waters the corresponding calcium salt, CaH2(CO3)2. Such springs may be looked for in dolomitic, limestone, and chalky districts.
- Sulphuretted waters are characterised by the presence of hydrogen sulphide which imparts to them its taste and odour. A considerable number of these springs occur in the British Isles, perhaps the best known being those at Harrogate (Yorks), The Leper's Well (Dinsdale, Durham), Lisdoonvarna (Clare, Ireland), Llandrindod Wells (Wales), Llanwrtyd (Wales), Moffat (Dumfries), Peebles, and Strathpeffer (Ross). Such waters have frequently been used in bygone years for secret correspondence. Letters written with a solution of lead acetate become legible when dipped, for example, in Harrogate water.
- Lithiated waters are in high pharmaceutical repute, the lithium being usually present as chloride. Baden-Baden (Germany) and Kissingen (Bavaria) are two well-known resorts of this type.
- Bromiuretted (Woodhall, Lincolnshire) waters contain small quantities of arsenic and bromine (as an alkali bromide) respectively. Goitrigenic Certain waters are particularly liable to cause abnormal activity of the thyroid gland, resulting in the enlargement known as goitre or Derbyshire neck. This is usually attributed to the presence in the water of organic matter, possibly a protozoon, but the suggestion has also been made that a connection may exist between radioactivity and goitrigenic properties of certain springs.
Buxton thermal water
Temperature 25.8° C. Density at 25.8° C. 0.99686
|Parts per 100,000||Grains per Gallon|
|Free carbon dioxide||0.287||0.201|
Droitwich brine contains:
|Sodium chloride||22.452 per cent.|
|Sodium sulphate||0.390 per cent.|
|Calcium sulphate||0.387 per cent.|
|Calcium carbonate||0.052 per cent.|
|Magnesium carbonate||0.115 per cent.|
With traces of alkali bromides and iodides, phosphates of calcium and iron, and silica.