This section is from the book "Elements Of The Theory And Practice Of Cookery", by Mary E. Williams. Also available from Amazon: Elements Of The Theory And Practice Of Cookery; A Textbook Of Domestic Science For Use In Schools.
Water exists not only in the ocean and in other bodies of water, but in plants, in the bodies of men and animals, and even in rocks and other things that seem quite dry. Air contains water; some fruits consist of little but water and flavoring, with just enough solid matter to give them form; our bodies are about three-fifths water.
Water is called "the universal carrier." It carries soil from place to place, piling in valleys what it washes away from hills; it bears seeds from one shore to plant them on another. It is the water in sap that enables it to flow through plants, carrying material to build them up; it is the water in blood that enables it to do the same for the animal body.
A substance so mixed with a liquid that its particles cannot be seen and do not settle is dissolved, or in solution. Water dissolves more substances than any other liquid To this property it owes much of its carrying power.
A. Put a level teaspoonful of salt into a glass of cold water. When the salt has disappeared taste the water. Put another teaspoonful into hot water. In which does the salt disappear more quickly? Try the same experiment with powdered chalk.
B. Find out which dissolves faster, a whole lump of sugar, or a lump broken into bits; coarse or fine salt.
C. Boil some of the salt solution till the water is all gone; taste the residue, and tell what it is.1
Salt is soluble in water; chalk is insoluble in water. Hot water dissolves salt more quickly than cold water does; that is, it is a better solvent for it. The more finely divided a substance is the more rapidly it dissolves. Why?
Clean water is colorless, odorless, and nearly tasteless. Its slight taste comes from various substances dissolved in it. One of these is air. If a glass of water stands until the air in it appears in bubbles on the glass, it is found to taste "flat." Absolutely pure water has no taste. Such water is not found in nature. That most nearly pure is the rain-water that falls during the latter part of a shower. The first rain to fall carries down with it dust and other impurities from the air. As water flows over or soaks through the ground, it dissolves both organic matter of plant and animal origin and inorganic matter of mineral origin.
Living things, plants or animals, differ from lifeless things, in being able to feed, grow, and reproduce themselves. Organs were once supposed to be necessary for these acts; and, in consequence, things once part of an animal or a plant, as well as things actually alive, were termed organic. Though we now know that some tiny living things have no organs, we still use the words organic and inorganic to distinguish these two kinds of matter. Examples of inorganic matter: water, sand, carbon dioxide. Examples of organic matter : wood, perspiration, leaf-mold, manure.
1 Sugar cannot be recovered from solution by boiling in the open air; it burns before it becomes solid. It may be recovered by crystallization, which we shall learn about in Chapter IX (Sugar And Sweets. Section 1. Sugar - Candies A Study Of Sugar).
Much organic matter in drinking water makes it unwholesome, and may make it dangerous. Most objectionable of organic impurities is sewage, which is likely to contain disease germs. Wells are often dug for convenience near houses. Such a well may be polluted by house and stable waste. Rivers and lakes may be polluted by factory waste and sewage from towns. Neither such water nor ice cut from it is safe to use.
Spring water and water from artesian wells is usually pure. City water, if not from pure sources, should be filtered through sand beds. Filters of charcoal or porcelain for household use must be kept clean, or they soon become filled with impurities, making the water passed through them foul instead of purer. Small filters screwed on faucets remove sediment but not bacteria (p. 30). Drinking water about the purity of which there is any doubt should be boiled.
Water is called hard or soft according to whether it contains much or little of the mineral calcium (lime). Neither dirt nor soap dissolves readily in hard water. Soap forms with it a curdy sub-stance. Some hard water becomes soft if boiled. Boiling makes the calcium insoluble and it is deposited on the inside of the kettle. (See if there is such a deposit on the school-kitchen tea-kettle, or on your kettle at home.) Such water is called temporarily hard water. In permanently hard water the calcium is in a different form. Boiling does not affect it. For cleaning and laundry purposes permanently hard water should be softened by the addition of washing soda or ammonia. A moderate degree of hardness does not injure water for drinking purposes. As a rule soft water is desirable for cooking, especially when the object is to draw out flavor or nourishment from food, as in making soup or tea.