Elements of the theory and practice of cookery

You may enjoy reading Dora's Housekeeping, a good story of how a girl kept house while her mother was away ; and " Notable Housekeepers " (one of these being Louisa M. Alcott), an article in the American Kitchen Magazine, February, 1898, Vol. VIII, p. 186. CHAPTER I PREPARATORY LESSONS Section 1. Air in its Relation to Life and to Fire Sunlight, pure air, and pure water are our common birthright, which we often bargain away for so-called comforts. — Ellen H. Richards and S. Maria Elliott. 1. Three things are essential to life, — air, water, and food. Of these, air is the first essential, since we can live without eating or drinking longer than without breathing. How is breathing related to health and life ? We can best answer this question by showing how air is affected by being breathed. AIR IN ITS RELATION TO LIFE 2. Testing air for carbon dioxide. — Experiments. A. Into a clean bottle, pour a little clear lime-water ; cork the bottle, and shake it so that the lime-water may come in contact with the air in the bottle. Do you see any change in the appearance of the lime-water? Now hold a glass tube so that it dips below the sur- face of the lime-water, and blow through it for a minute or two. Is the lime-water changed in appearance ? Do you think that air exhaled from the lungs is just like air in the room? B. Insert a splinter in a cork, light the splinter, and fit the cork into the neck of a bottle. What happens? Pour a little clear lime-water into the bottle and shake. Note the effect on the lime- water. 5 > 6 THEORY AND PRACTICE OF COOKERY Air from the lungs and air in which a splinter has been burned both turn lime-water cloudy. It is known that this cloudiness is produced only by carbon dioxide, an invisible gas. How does this gas get into the air ? 3. Composition of air; formation of carbon dioxide by burning. — Air is a mixture of two invisible gases, oxygen and nitrogen.^ Wood contains carbon. 4. When the splinter is lighted, a part of this carbon unites with the oxygen of the air to form carbon diox- ide, and continues uniting with it as long as any oxygen is left in the bottle. When all this has been used, the fire goes out, because the oxygen has been replaced by carbon dioxide, in which nothing will burn. Part of the carbon remains unburned as charcoal. 5. Formation of carbon dioxide in the body; oxygen necessary to life. — The presence of carbon dioxide in air that has been breathed is similarly caused by a slow kind of burning constantly going on in the body. That the body contains carbon may be shown by burning a piece of meat, which has almost exactly the same com- position as human flesh. It becomes black like the burned splinter. The oxygen of the air taken into the lungs unites with this carbon, produces heat to keep the body warm, and forms carbon dioxide. The walls of the little cells in the lungs are so thin that oxygen passes through them into tiny blood-vessels called eap- 1 Argon, a gas discovered in 1894, is also found in air, but in such small quantities that it may be disregarded here. PREPARATORY LESSONS 7