A manual of practical hygiene : intended especially for medical officers of the Army and for civil medical officers of health / by Edmund A. Parkes.

Date:
1873
Catalogue details

Licence: Public Domain Mark

Credit: A manual of practical hygiene : intended especially for medical officers of the Army and for civil medical officers of health / by Edmund A. Parkes. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    Fed from a variety of sources, river water is even more complex in its con- stitution than spring water ; it is also more influenced by the season, and by circumstances connected with season, such as the melting of snow or ice, rains and floods, &c. The water taken on opposite sides of the same river has been found to differ slightly in composition. The general result of solution and decomposition is that the water of springs and rivers often contains a great number of constituents—some in very small, others in great amount. Some waters are so highly charged as to be termed mineral waters, and to be unfit for drinking, expect as medicines. The im- purities of water are not so much influenced by the depth of the spring as by the strata it passes through. The water of a surface spring, or of the deepest Artesian well, may be pure or impure. The temperature of the water also varies, and is chiefly regulated by the depth. The temperature of shallow springs alters with the season; that of deeper springs is often that of the yearly mean. In very deep springs, or in some Artesian wells, the tempera- ture of the water is high. The substances which are contained in spring, river, and well waters are noted more fully under the head of “ Examination of Water.” There may be suspended matters, mineral, vegetable, or animal; dissolved gases, viz., nitrogen, oxygen, carbonic acid, and in some cases sulphuretted hydrogen, and carburetted hydrogen; and dissolved solid matters, consisting of lime, magnesia, soda, potassa, ammonia, iron, alumina, combined with chlorine, and sulphuric, carbonic, phosphoric, nitric, nitrous, and silicic acids. More infrequently, or in special cases, certain metals, as arsenic, manganese, lead, zinc, and copper may be present. The mode of combination of these substances is yet uncertain; it may be that the acids and bases are equally distributed among each other, or some other modes of combination may be in play. The mode of combination is usually assumed to be as follows.* The chemist determines the amount of each separate substance, and then calculates the combination as follows. The chlorine is combined with sodium ; if there is an excess, it is combined with potassium or calcium ; if there is an excess of soda, it is combined with sul- phuric acid, or if still in excess, with carbonic acid. Lime is combined with excess of chlorine, or sulphuric acid, or if there be no sulphuric acid, or an excess of lime, with carbonic acid. Magnesia is combined with carbonic acid. So that the most usual combinations are sodium chloride; sodium sulphate ; sodium carbonate; calcium carbonate (held in solution by carbonic acid); calcium sulphate ; calcium chloride and silicate; and magnesium carbonate ; but the results of the analysis may render other combinations necessary. Distilled Water.—Distillation is now very largely used at sea, and affords an easy way of getting good water from sea or brackish water. Almost any form of apparatus will suffice, if fuel can be procured, to obtain enough water to support life; and if even the simplest appliances are not attainable, the mere suspension of clean woollen clothing over boiling water will enable a large quantity to be collected. At sea, salt water is sometimes mixed with it from the priming of the boilers, and occasionally from decomposition of magnesium chloride (probably), a little free hydrochloric acid passes off. This can, if necessary, be neutralised by sodium carbonate. As distilled water is nearly free from air, and is therefore unpalatable to some persons, and is supposed indigestible, it may be aerated by allowing it to run through a cask, the bottom of which is pierced with fine holes, so as to expose the water to the air. Plans for aerating the water distil]ed from * Fresenius, Quantitative Analysis, 3rd edit. p. 481.