Human Foods and Their Nutritive Value by Harry Snyder (dark academia books to read .TXT) 📕
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The argument is sometimes advanced that the mineral matter present in water is needed for the construction of the bone and other tissues of the body, and that distilled water fails to supply the necessary mineral matter. This is an erroneous assumption, as the mineral matter in the food is more than sufficient for this purpose. When water is highly charged with mineral salts, additional work for their elimination is called for on the part of the organs of excretion, particularly the kidneys; and furthermore, water nearly saturated with minerals cannot exert its full solvent action.
In discussing the immediate benefits resulting from improvement of water, Fuertes says:[92]
"Immediately after the change to the 'four mile intake' at Chicago in 1893, there was a great reduction in typhoid. Lawrence, Mass., showed a great improvement with the setting of the filters in operation in September, 1893; fully half of the deaths in 1894 were among persons known to have used the unfiltered canal water. The conclusion is warranted that for the efficient control of the death rate from typhoid fever it is necessary to have efficient sewerage and drainage, proper methods of living, and pure water. The reason why our large cities, which are all provided with sewerage, have such high death rates is therefore without doubt their continuance of the filthy practice of supplying drinking water which carries in solution and suspension the washings from farms, from the streets, from privies, from pigpens, and the sewage of cities.... And also we should recognize the importance of flies and other winged insects and birds which feed on offal as carriers of bacteria of specific diseases from points of infection to the watersheds, and the consequent washing of newly infected matter into our drinking water by rains."
There is a very close relationship between the surface water and that of shallow wells. A shallow well is simply a reservoir for surface water accumulations. It is stated that, when an improved system of drainage was introduced into a part of London, many of the shallow wells became dry, indicating the source from which they received their supply. Direct subterranean connection between cesspools and wells is often traced in the following way: A small amount of lithium, which gives a distinct flame reaction, and a minute trace of which can be detected with the spectroscope, is placed in the cesspool, and after a short time a lithium reaction is secured from the well water.
Rain water is relied upon in some localities for drinking purposes. That collected in cities and in the vicinity of barns and dwellings contains appreciable amounts of organic impurities. The brown color is due to the impurities, ammonium carbonate being one of these. There are also traces of nitrates and nitrites obtained from the air. When used for drinking, rain water should be boiled.
270. Improvement of Waters.—Waters are improved by: (1) boiling, which destroys the disease-producing organisms; (2) filtration, which removes the materials mechanically suspended in the water; and (3) distillation, which eliminates the impurities in suspension and solution, as well as destroys all germ life.
Fig. 62.—Pasteur
Water Filters.
271. Boiling Water.—In order to destroy the bacteria that may be in drinking water, it is not sufficient to heat the water or merely let it come to a boil. It has been found that if water is only partially sterilized and then cooled in the open air, the bacteria develop more rapidly than if the water had not been heated at all. It should boil vigorously five to ten minutes; cholera and typhoid bacteria succumb in five minutes or less. Care should be taken in cooling that the water is not exposed to dust particles from the air nor placed in open vessels in a dirty refrigerator. It should be kept in perfectly clean, tight-stoppered bottles. These bottles should be frequently scalded. Great reliance may be placed upon this method of water purification when properly carried out.
272. Filtration.—Among the most efficient forms of water filters are the Berkefeld and Pasteur. The Pasteur filter is made of unglazed porcelain, and the Berkefeld of fine infusorial earth (finely divided SiO2). Both are porous and allow a moderately rapid flow of water. The flow from the Berkefeld filter is more rapid than from the Pasteur. The mechanical impurities of the water are deposited upon the filtering surface, due to the attraction which the material has for particles in suspension. These particles usually are the sources of contamination and carry bacteria. When first used, filters are satisfactory, but unless carefully looked after they soon lose their ability to remove germs from the water and may increase the impurity by accumulation. Small faucet filters are made of porous stone, asbestos, charcoal, etc. Many of them are of no value whatever or are even worse than valueless. Filters should be frequently cleansed in boiling water or in steam under pressure. Unless this is done, the filters may become incubators for bacteria.
273. Distillation.—When an unquestionably pure water supply is desired, distillation should be resorted to. There are many forms of stills for domestic use which are easily manipulated and produce distilled water economically.[93] The mineral matter of water is in no way essential for any functional purpose, and hence its removal through distillation is not detrimental.
Fig. 63.—Water Still.
274. Chemical Purification.—Purification of water by the use of chemicals should not be attempted in the household or by inexperienced persons. When done under supervision of a chemist or bacteriologist, it may be of great value to a community. Turneaure and Russell,[94] in discussing the purification of water by addition of chemicals, state:
"There are a considerable number of chemical substances that may be added to water in order to purify it by carrying down the suspended matter as well as bacteria, by sedimentation. Such a process of purification is to be seen in the addition of alum, sulphate of iron, and calcium hydrate to water. Methods of this character are directly dependent upon the flocculating action of the chemical added, and the removal of the bacteria is accomplished by subsidence."
275. Ice.—The purity of the ice supply is also of much importance. While freezing reduces the number of organisms and lessens their vitality, it does not make an impure water absolutely wholesome. The way, too, in which ice is often handled and stored subjects it to contamination, and foods which are placed in direct contact with it mechanically absorb the impurities which it contains. For cooling water, ice should be placed around rather than in it. Diseases have frequently been traced to impure ice. The only absolutely pure ice is that made from distilled water.
276. Mineral Waters.—When water is charged with carbonic acid gas under pressure, carbonated water results, and when minerals, as salts of sodium, potassium, or lithium, are added, artificial mineral waters are produced. Natural mineral waters are placed on the market to some extent, but most mineral waters are artificial products and they are sometimes prepared from water of low sanitary character. Mineral waters should not be used extensively except under medical direction, as many have pronounced medicinal properties. Some of the constituents are bicarbonates of sodium, potassium, and lithium; sulphates of magnesium (Epsom salts) and calcium; and chloride of sodium. The sweetened mineral waters, as lemonade, orangeade, ginger ale, and beer, contain sugar and organic acids, as citric and tartaric, and are flavored with natural or artificial products. Most of them are prepared without either fruit or ginger. Natural mineral waters used under the direction of a physician are often beneficial in cases of chronic digestion disorders or other diseases.
Fig. 64.—Typhoid
Bacilli.
277. Materials for Softening Water.—The materials most commonly used for softening water are sodium carbonate (washing soda), borax, ammonia, ammonium carbonate, potash, and soda lye. Waters that are very hard with limestone should have a small amount of washing soda added to them. Two ounces for a large tub of water is the most that should be used, and it should first be dissolved in a little water. If too much soda is used, it is injurious, as only a certain amount can be utilized for softening the water, and the excess simply injures the hands and fabric. When hard limewater is boiled and a very little soda lye added, a precipitate of carbonate of lime is formed, and then if the water is strained, it is greatly improved for washing purposes. Borax is valuable for making some hard waters soft. It is not as strong in its action as is sodium carbonate. For the hardest water ¼ pound of borax to a large tubful may be used; most waters, however, do not need so much. Ammonia is one of the most useful reagents for softening water. It is better than washing soda and borax, because the ammonia is volatile and does not leave any residue to act on the clothes, thus causing injury. For bathing purposes, the water should be softened with ammonia, in preference to any other material. Ammonia should not be poured directly into hot water; it should be added to the water while cold, or to a small quantity of cold water, and then to the warm water, as this prevents the ammonia from vaporizing too readily. Ammonia produces the same effect as potash or soda lye, without leaving a residue in the garments washed. It is especially valuable in washing woolen goods or materials liable to shrink. Waters which are hard with alum salts are greatly benefited by the addition of ammonia. A little in such a water will cause a precipitate to form, and when the water is strained it is in good condition for cleaning purposes. Ammonium carbonate is used to some extent as a softening and cleaning agent, and is valuable, as there is no injurious effect upon clothing, because it readily volatilizes. Caustic potash and caustic soda are sometimes employed for softening water, but they are very active and are not adapted to washing colored or delicate fabrics. They may be used for very heavy and coarse articles that are greasy,—not more than a gram in a gallon of water. Bleaching powder is not generally a safe material for cleansing purposes, as it weakens the texture of clothing. After a contagious disease, articles may be soaked in water containing a little bleaching powder and a few drops of carbolic acid, followed by thorough rinsing and bleaching in the sun. But as a rule formaline is preferable for disinfecting clothing. It can be used at the rate of about one pound to 100 gallons of water. Bleaching powder, caustic potash or soda, and strong soap are not suitable for cleaning woodwork, because of the action of the alkali on paint and wood; they roughen the surface and discolor the paint. Waters vary so in composition, that a material suitable for softening one may not prove to
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