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The Marvels of Water
W HEN the world was in the making there were terrific lightning storms and these great electrical discharges, together with the heat generated by the mighty upheavals of primordial matter, caused the hydrogen and the oxygen to combine chemically as water vapor in the atmosphere. This vapor finally fell as liquid water and blanketed the earth and this was the origin of the lakes, seas, and rivers. What Water Is.—Different from the air, which is a mere mechanical mixture of its two constituent gases, water is formed of free oxygen and free hydrogen in the proportion of one part of the former and two parts of the latter by volume, that is by bulk. Now, these gases will not combine at ordinary temperatures, neither will they burn when they are combined. This, obviously, is a very wise provision, for so inflammable are each of these gases separately that a mere spark would suffice to ignite them, and so fire the whole world. When oxygen and hydrogen are merely mixed together, like the nitrogen and oxygen of the air, they are very explosive, and when they explode they combine chemically, the resultant product of which is the liquid we call water. If a jet of hydrogen is burned in a jet of oxygen they will not explode provided the correct proportions of each gas are maintained. Under these conditions the flame thus produced is, with the exception of the electric arc, the hottest that we know how to make. To obtain the oxy-hydrogen flame a special nozzle is used, and when the flame is directed on a piece of lime it heats it to incandescence and this makes a dazzling light. This oxy-hydrogen light, as it is called, was used for years in stereopticons and for spot-lights in theatres before the electric light displaced it. There are two laboratory experiments you can make which prove that water is really formed of oxygen and hydrogen. One of these is to decompose it with a current of electricity, and the other is to combine the two gases by igniting them with an electric spark. To decompose water is easy, for you need only to invert two test-tubes filled with water in a tumbler of water and bring one end of one of the wires of an electric battery under and into one test-tube, and the other wire from the battery under and into the other test-tube. (See Chapter XIII.) Water that is ordinarily pure will not conduct an electric current, and to make it do so you must put a few drops of sulphuric acid into it. This done, switch on the current and you will see a lot of little bubbles form on each of the ends of the wires, or electrodes, and, presently, you will also observe that the water in the upper ends of the tubes is falling, and, moreover, that it falls twice as fast in one tube as it does in the other. This is because the spaces in the tubes are being filled with gases which displace the water as it is formed and that twice as much hydrogen is being formed as oxygen. As these gases have no color you cannot see them and so to know they are actually there and to tell them apart you must make some kind of a test. This you can do by removing the tube, closed end up, in which there is the least water and holding a lighted match to the mouth of it. There will be a miniature explosion, which is the proof that it contains hydrogen gas and it will burn with a flame that is just about the color of air. To test the other tube for oxygen, remove the tube, closed end up, light a match and blow out the flame of it so that only a kindling spark remains; push it into the tube when it will instantly burst into a flame again, and this proves that it contains oxygen. Further tests will show that the sulphuric acid added to the water to make it a conductor remains after the water has been electrolyzed, as it is called. While the above experiment proves that oxygen and hydrogen have been separated out from the water it does not prove that water is formed of them and nothing else. To show this conclusively you need a laboratory apparatus called a eudiometer; this consists of a graduated tube so that two volumes of hydrogen and one volume of oxygen can be passed into it. In the upper end of the tube, which is closed, a pair of platinum wires is sealed in so that a small spark-gap is formed. Now as long as the hydrogen and the oxygen in the tube are not subjected to heat they will remain merely mixed, but the instant that an electric spark is made to jump across the spark-gap the two gases will explode and chemically combine when a minute drop of water will be produced. Since it takes more than 2,000 volumes of the mixed gases to make one volume of water it is easy to see why the resultant amount of the latter is so very small. How Water Behaves.—Water in its pure state has neither taste nor odor. If you will hold a glass of it between your eyes and a source of light it will appear to be without color, but if you look at a large quantity of it as, for instance, a lake, it takes on a blue color. This is often supposed to be due to the reflection of the sky, but, as a matter of fact, it is the natural color of the water itself when it is pure or nearly so. There are three states that water can take on and these are (1) liquid, (2) steam, and (3) ice. At all temperatures between 212 degrees above zero and 32 degrees above zero, using a Fahrenheit thermometer, water remains a liquid. When it is heated to 212 degrees it boils at sea-level, and oppositely when it is cooled to 32 degrees it freezes. When water boils it is converted into true steam, and this is a vapor that cannot be seen. When this vapor passes into the colder air it condenses into minute drops of water. An easy experiment to show that true steam cannot be seen is to take a flask, such as chemists use, partly fill it with water and heat it over the flame of an alcohol lamp or a Bunsen burner. When it boils you will know that steam is being generated and yet you cannot see it in the space above the water. The moment you uncork the flask, though, you will see the so-called steam rising from it in the air. It is well known that all metals, except certain alloys, and many other solid substances, when heated and which are then allowed to cool, contract; that is they shrink a little. Water, when cooled, likewise shrinks until it reaches a temperature of plus 39 degrees, Fahrenheit, which is seven degrees above its freezing-point. Water is then the heavier. As the temperature falls from 39° to 32° it expands, and the colder water (32°) is at the top of the vessel, as it begins to solidify, that is, to change into ice. Since the density of ice is less than water it weighs proportionately less, and this is the reason why ice forms on the surface of water as well as floats on top of it. If water continued to shrink as it became ice it would sink and choke up the waterways and besides it might never melt. The mighty force set up by water when it begins to freeze is a phenomenon that you are probably well acquainted with, for it is then that it bursts water-pipes, cracks milk bottles and plays havoc in general. At the end of this chapter we shall tell you how artificial ice is manufactured. Kinds and Uses of Water.—There is, of course, only one kind of water chemically, but physically there are many different kinds depending on whether it is impure or pure, that is, contains foreign substances or not. Pure water, as you have seen, consists of hydrogen and oxygen and contains nothing else, and this may be obtained in quantities by distilling ordinary water. Rain water is, generally speaking, as free from impurities as is ever found in nature, but as it always contains other substances, it cannot be really called pure. Well and spring water that look so clear and sparkling contain mineral substances of various kinds, while surface water fairly teems with germs, some of which are harmless, while others produce virulent diseases. Water is the natural drink of man, but as he grew in curiosity and knowledge he experimented with its effect on other substances and so found among other things, that certain herbs, fruit and grains when steeped, boiled and distilled with water produced drinks that were pleasing to the taste and stimulating to the system. Water, however, is necessary to the well-being of all living things, since they themselves, whether plants or animals, are formed of three-fourths part of it. Hence the matter of providing a supply that is free from harmful substances is a vital one to the human race. And this is also true in the arts and industries, for many kinds of water contain substances which make them unsuitable for certain purposes and, what is more to the point, they are actually injurious, as you will presently see. About Drinking Water.—Drinking water, or potable water as it is called, plays a large part in determining the state of the health, and, consequently, it is important that it should be of the right kind. Now, as already stated, water from springs and deep wells is generally free from germs, but it always contains more or less mineral matter. As the water soaks through the soil the germs in it become attached to the particles of the latter and are not carried down with it; on the other hand, as the water comes in contact with the minerals of the soil it dissolves some of them and carries them along in solution. If a well is dug, a pump is driven, or the stream finds its way to the surface, as a spring, the water will be pure and wholesome because the disease germs have been filtered out of it. Should the underground stream reach the sea, it carries the mineral substances with it, and when the sea water evaporates, only pure water goes up and, this comes down again as rain. You can easily find out the amount of foreign matter there is in any kind of water, for all you need to do is to fill a porcelain dish with some of it and heat it over an alcohol, or a Bunsen, flame until it has all evaporated, when the solid matter will remain behind. Where the water seeps through soil containing granite rock very little of the latter will be dissolved away, but where the water comes in contact with limestone large amounts of the latter will be dissolved. Soft and Hard Water.—Rain water and other kinds of water that contain very little mineral matter are called soft water, while, oppositely, water that contains limestone and other mineral substances is called hard water. As a matter of fact, water of any kind that contains enough mineral matter to make soap curdle is hard water. Where there are more than twenty-five parts of mineral matter in a million parts of water it does not affect it to the extent of making it hard, but where there are more than fifty parts of mineral matter in a million parts of water it makes it quite hard. There are two kinds of hard water, and these are: (1) temporary hard water, and (2) permanent hard water. The difference between them is that you can get rid of the hardness of the first kind by boiling it, since it contains limestone, and this is precipitated, that is, it is thrown down, and deposited on the inside of the kettle. But boiling will not remove the hardness of the second kind for the reason that it contains gypsum, or, rather, calcium sulphate, which cannot be precipitated in this way. You can, however, soften permanent hard water to some extent by adding sal soda to it, as this tends to precipitate the gypsum when sodium sulphate is left in solution. How Soap Acts on Water.—When you put soap into soft water it makes it lather or suds, because there is little or no mineral matter in it. But when you put soap into hard water it combines with the mineral substances chemically and forms a compound that cannot be dissolved. If, however, you precipitate the limestone that is in hard water by boiling, or the gypsum by adding sal soda to it as described above, the soap and water will then lather or suds freely. Where hard water is the only kind available for use in the home it becomes quite an item of expense for it wastes the soap in proportion to its hardness. Not only this, but where it is very hard, the mineral substances get into the pores of the skin and the soap will have very little effect in getting them out. So, too, they lodge between the meshes of goods that are washed and in the same way and for the same reason it is quite impossible to get them clean. Nearly all laundry soaps and washing powders have an excess of soda in them to soften hard water and this has a very bad effect on the goods. Boiler Water and Boiler Scale.—If you will look into a teakettle you will see, if you use well water in it, that the inside of it is incrusted, or has fur on it, as it is sometimes called. This is, of course, the precipitate of the mineral matter caused by boiling the water. Where hard water is used for running engines and steam plants the same action takes place, though on a larger scale and with a more destructive effect. That is to say, the inside of the boiler and tubes becomes coated with the mineral matter and this prevents the heat from passing through them and wastes the coal. There are other disadvantages in using hard water in boilers, and among them are: (1) the boiler scale and boiler plate, of which the boiler is made, expand at different rates and this often leads to weakening the seams; (2) the scale may cause the tubes to get red-hot and this not only shortens the life of the boiler but may cause it to explode; (3) it pits the tubes of the boiler, and (4) it causes the water to foam. The easiest and cheapest method of keeping a boiler from scaling and pitting and the water from foaming is to use soft water, but this is not always practical. The next best thing is to get rid of the hardness of the water if hard water must be used. If the hardness is temporary the water can be boiled before it is used in the boiler or it can be treated by adding milk of lime which is made by stirring slaked lime in water. To soften boiler water whose hardness is permanent, lime water is added to it, but the amount used must be according to the amount of mineral matter there is in it. Where boiler water has both limestone and gypsum in it so that it has both temporary and permanent hardness, both can be removed by adding a solution of crude caustic soda to it. What is called the permutit process is also widely used for softening boiler water. Permutit is a coarse kind of sand, and when the water to be used is filtered through it the mineral substances react with the sand, and the sodium, which is in the sand, replaces the calcium in the water. The sodium compound goes into the boiler with the water but has no action except to clean it. Purifying Water on a Big Scale.—To provide water in sufficient quantities to supply cities has been one of the great problems of civilized mankind, but it is only during the last fifty years or so that the necessity for purifying water for drinking purposes has been fully taken into account. Now there are several ways by which water can be purified and among the more important are by: (1) boiling, (2) aeration, (3) chemical processes, (4) the ozone process, (5) biological processes, (6) the coagulation method, and (7) mechanical separation. For purifying water on a small scale, as for home use, boiling is the simplest and best method. But for purifying water on a large scale the last-named six methods given above are employed either separately or in combination. Aerating the water is done either by throwing it into the air or else letting it fall over a steep hill of rocks. In either case when the water comes into contact with the air some of the oxygen of the latter is dissolved out of it. While this treatment improves the water it does not purify it to any great extent. One of the chemical processes consists of adding bleaching powder to the water, when chlorine is liberated and this gas kills off all the harmful germs. Ozone, which is a vigorous form of oxygen, is produced by electric discharges in the air and this when introduced into the water also kills off the germs. Ozone is far better than chlorine for this purpose, as an excess of the former in the water cannot be detected, whereas any excess of the latter gives the water a bad taste. The most curious of all methods for purifying water is that of putting germs that are harmless to the human system into the water and these kill off the harmful germs. This is known as a biological process. Another curious way of ridding water of germs is by the coagulation process. In this process a harmless glue-like substance is put into the water, and the germs and other impurities stick to it. The mass is then separated out from the water when the latter is left comparatively pure. In the sedimentation method much of the impurities, including the germs, falls to the bottom, but it does not get rid of all of them. Usually after sedimentation the water is passed through mechanical or sand filters which remove the rest of the germs and other impurities.
The apparatus used for the manufacture of ice by the ammonia process consists of a compressor driven by an engine or other source of power, a water-cooled series of pipes, and a cooling-tank. Ammonia gas is passed into the compression cylinder where it is compressed and liquefied, then it is passed through a series of pipes on which cold water drips. It is next allowed to expand into a gas, and as it does so it flows through another series of pipes immersed in a tank of brine, that is a solution of salt and water, which will not freeze at the temperature of ordinary water. As the ammonia flows through these pipes it absorbs the heat of the brine until the temperature of the latter drops to below plus 32 degrees Fahrenheit, which is the freezing-point of ordinary water. Sheet-steel cans filled with distilled water are immersed in the brine, and thus the water in them is frozen. |
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