Flash Fuel Value The measure of safety of kerosene is the temperature at which it will give off an inflammable gas. This is called the flash point and is determined by heating the oil slowly and observing the temperature at which a flash can be produced by applying a lighted taper to the surface of the oil. Below the flash point, there is no danger of explosion from oil. Most states in the United States have a legal flash point, or a fire test, below which standard kerosene cannot be sold. The flash point of good kerosene is 120° F. The fire test is the temperature at which the oil will take fire and burn when a light is applied. This is about 30° F higher than the flash point. The ordinary temperature of the room is above the flash point of gasoline, naphtha, benzine, etc. In other words, these substances are constantly giving out an inflammable vapor. A comparison of the heating value of the various fuels will be of interest. Practical tests of the amount of steam produced in a steam boiler have shown that one cord of ordinary wood is approximately equal to one-half ton of coal; a gallon of oil (or gasoline) is equal to about twelve pounds of coal; 1,000 cubic feet of coal gas is equal to 50 or 60 pounds of coal, or about four and one-half gallons of oil. Hard coal has a little higher fuel value than soft coal, because the combustion is commonly more perfect. Coke is nearly equal to hard coal by weight, but is much more bulky. It is usually sold by measure. A bushel of coke weighs 40 pounds, of anthracite 67 pounds, and of soft T coal 76 pounds. Damp wood is a much poorer fuel than dry wood, because so much heat is absorbed and wasted in changing the water into steam. The heat given off by a fuel is not the only point to be considered. In the cook stove, but a small portion of the heat given off by the solid fuel can be used for cooking, as most of it is radiated into the room or carried up the chimney. In the gas or oil stove, the flame may be applied exactly where it is wanted, so that the proportion of heat which can be used is much greater. Moreover, the flame can be shut off instantly when wanted no longer and all expense stopped. On the other hand, the range usually serves to heat the water of the hot water system, incinerate garbage, and in winter helps to heat the house. FOOD Having the fire well under way the housekeeper turns her attention to the breakfast. A great variety of chemical actions may here be considered. In the first place, why must we "eat to live?" Wherever there is life, there is chemical change; and as a rule a certain degree of heat is necessary. in order that chemical change may occur. Vegetation does not begin in the colder climates until the air becomes warmed by the heat of the spring. When the cold of winter comes upon the land vegetation ceases. Since many animals live in temperatures in which plants would die, it is evident that they must have some Why We Must Eat Combustion in the Body Vital Temperature Air as Food source of heat in themselves. This is found in the union of the oxygen of the air breathed with carbonaceous matter eaten as food and the formation of carbon dioxide and water, just as in the combustion of wood or coal. Only instead of this union taking place in one spot and so rapidly as to be accompanied by light, as in the case of fire, it takes place slowly and continuously in each living cell. Nevertheless, the chemical reaction seems to be identical. The heat of the human body must be maintained at 98.5° F the vital temperature-the temperature necessary for the best performance of the normal functions. Any continued variation from this degree of heat indicates disease. Especially important is it that there be no considerable lowering of this temperature, for a fall of one degree is dangerous, since in that case the chemical changes necessary to the body cannot be carried out. The slow combustion or oxidation of the carbon and hydrogen of food cannot take place without an abundance of oxygen; hence the diet of the animal must include fresh air-a point not always considered. The amount of oxygen taken in by the body daily is equal to the sum of all the other food elements. Except water, two-thirds of these foods consists of some form of starch or sugar-the socalled carbohydrates, in which the hydrogen and oxygen are found in the same proportion as in water. The power to do mechanical work comes from the combustion of fuel. The body is a living machine capable of doing work, raising weights, pulling loads, and the like. The animal body also requires fuel in order to do such work as thinking, talking, even worrying. For the present, then, we will say that food is necessary, (1) to preserve the vital temperature and (2) to enable the body-machine to do its work. Suppose we begin our breakfast with fruit, say, an orange or a banana. Fruits are especially rich in sugars and these are composed of carbon, hydrogen, and oxygen. If sugar is placed upon a stove, it will melt and steam (water) will pass off into the air, leaving the black charcoal (carbon) on the stove. Moreover, sugars burn easily and fiercely. We shall get both heat and energy from our fruit. Within the body it will be changed into water and carbon dioxide. Fruits contain a large percentage of water; but the banana is capable of giving more energy and heat than the orange, because it has much less water and more sugar. Fruit loses in drying a large portion of its water, so that dried fruits contain a larger percentage of food materials than fresh fruits. For instance, raisins are 60 per cent grape sugar. Fruits consist of a loose net-work of a woody material holding the soft pulp and this woody fibre, called cellulose, is practically indigestible. Cooking softens this, making cooked fruits easier to digest. The Body a Machine Fruit Cellulosa Cane Sugar SUGARS AND STARCHES. At breakfast some sugar from the sugar bowl may be added to the fruit. Many people add sugar to the oatmeal or other cereal eaten, although it is often held by teachers of dietetics that this is not a good place to use it, for proper cooking and thorough mastication of the cereal will bring out a rich sweetness due to changes explained later. Country boys know how sweet a morsel is made by chewing raw grains, especially wheat. Possibly a glass of milk is taken at breakfast and this contains another kind of sugar-milk sugar— in about 5 per cent. Coffee and tea are usually sweetened, so that a considerable part of the breakfast may be of this class of foods-a quickly burning material giving heat and energy. There are several different sugars recognized by chemists; these are cane sugar or sucrose, grape sugar or glucose, milk sugar or lactose, and fruit sugar or levulose. Cane sugar is obtained from the juices of many plants, notably sugar beets, sugar cane, the palm, and as maple sugar from the rock-maple trees. Molasses and brown sugar are obtained during the manufacture of white sugar from sugar cane. Cane sugar is composed of carbon, hydrogen, and oxygen in the proportion of twelve parts of carbon to eleven parts of water. When sugar is heated it is chemically changed, more or less, according to the degree of heat and the rapidity with which it parts with its water. |