Caution. — Causes of iron rust should be carefully avoided. A loose screw lying in the laundry tub, hooks on wash gar- ments, etc., are liable to make much trouble. Lemon juice and salt tend to rot material to which they are applied. Hence it is wise to avoid stains which call for their use. Digitized by Google COMBUSTION 17 Combustion Experiment 1. — Light a candle. Place a bottle over it. What happens? Experiment 2. — Light a candle, place a bottle over it, and just before the light goes out, lift the bottle. What happens? Experiment 3. — Light a candle, place a chimney over it, and put a piece of paper over the top of the chimney. What happens? Rehght the candle, and raise the chimney a little at the bottom. What happens? What is necessary to make the candle bum and to keep it burning? Experiment 4. — Light a taper and put it into a bottle. Cover the bottle. After the Ught has gone out, pour a Uttle limewater into the bottle. What happens to the limewater? We have produced a gas in the bottle which turns limewater milky. It is composed of carbon and oxygen, and is called carbon dioxide. Limewater is the test for carbon dioxide. Experiment 5. — Breathe into a bottle. Pour a little lime- water into the bottle. We have the same gas, carbon diox- ide, in our breath. Experiment 6. — Light a taper and put it into a bottle. Does any water collect on the sides of the bottle ? Water is composed of hydrogen and oxygen. Air. — From experiments 1, 2, 3, and 4 we may conclude that air is necessary to keep the candle burning. Air is a mixture of nitrogen and oxygen. It is the oxygen which is the active element. Oxidation. — Oxygen has a great tendency to unite with other elements. When they unite slowly, we do not notice any rise in temperature. This gradual process is called oxi-- dation. Combustion. — When fire is applied to fuels, the oxidation Digitized by Google 18 FIRST YEAR takes place rapidly. Noticeable heat and light are produced. This process is called combustion. Kindling Point. — Fuels differ as to the temperature at which they will bum or unite with oxygen. The tempera- ture at which a substance will begin to bum is called the kindling point. Make a list of fuels, beginning with those that have the lowest kindling point. Composition of Fuels. — From experiments 4 and 5 we may conclude that fuels contain carbon. From experiment 6 we may conclude that fuels also contain hydrogen. Products of Combustion. — The chief products of combus- tion of fuels are the gases which rise from the fire. They are carbon dioxide and carbon monoxide and usually steam. Carbon monoxide is the gas that bums near the fuel with a bluish flame. It is the product of incomplete combustion. Carbon dioxide is the product of complete combustion and is invisible. Much of the fuel is wasted in the process of combustion. Smoke and soot are a loss. Smoke is composed of the little pieces of fuel which have been partly bumed, and escape with the vapor in the draft up the chimney. When wood and soft coal are bumed, parts of the oily com- pounds are combined with the imconsumed bits of fuel Mid stick to the chimney flues. This is called soot. Chinmeys have to be kept free from soot, for it sometimes collects in large quantities and ignites in the chimney and bums. Ashes are the mineral substances in the fuels which will not bum. Digitized by Google THE KITCHEN FIRE 19 Kerosene Lamps I. Cleaning. Occasionally take oflf th^ burners, la3ring them on several folds of newspaper; take out the wicks, boil the burners in soda water in the proportion of one (1) teaspoonful of washing soda to one (1) quart of water. At all times keep the air holes free from dust and lamp dirt. II. Filling. Fill the lamp to within one inch of the top. Trim the wick with care ; see that it is perfectly even,

AI-modernized reading of the original text

Caution. — Causes of iron rust should be carefully avoided. A loose screw lying in the laundry tub, hooks on wash garments, etc., are liable to make much trouble. Lemon juice and salt tend to rot material to which they are applied. Hence it is wise to avoid stains which call for their use. Digitized by Google COMBUSTION 17 Combustion Experiment 1. — Light a candle. Place a bottle over it. What happens? Experiment 2. — Light a candle, place a bottle over it, and just before the light goes out, lift the bottle. What happens? Experiment 3. — Light a candle, place a chimney over it, and put a piece of paper over the top of the chimney. What happens? Relight the candle, and raise the chimney a little at the bottom. What happens? What is necessary to make the candle bum and to keep it burning? Experiment 4. — Light a taper and put it into a bottle. Cover the bottle. After the light has gone out, pour a little limewater into the bottle. What happens to the limewater? We have produced a gas in the bottle which turns limewater milky. It is composed of carbon and oxygen, and is called carbon dioxide. Limewater is the test for carbon dioxide. Experiment 5. — Breathe into a bottle. Pour a little limewater into the bottle. We have the same gas, carbon dioxide, in our breath. Experiment 6. — Light a taper and put it into a bottle. Does any water collect on the sides of the bottle ? Water is composed of hydrogen and oxygen. Air. — From experiments 1, 2, 3, and 4 we may conclude that air is necessary to keep the candle burning. Air is a mixture of nitrogen and oxygen. It is the oxygen which is the active element. Oxidation. — Oxygen has a great tendency to unite with other elements. When they unite slowly, we do not notice any rise in temperature. This gradual process is called oxidation. Combustion. — When fire is applied to fuels, the oxidation Digitized by Google takes place rapidly. Noticeable heat and light are produced. This process is called combustion. Kindling Point. — Fuels differ as to the temperature at which they will bum or unite with oxygen. The temperature at which a substance will begin to bum is called the kindling point. Make a list of fuels, beginning with those that have the lowest kindling point. Composition of Fuels. — From experiments 4 and 5 we may conclude that fuels contain carbon. From experiment 6 we may conclude that fuels also contain hydrogen. Products of Combustion. — The chief products of combustion of fuels are the gases which rise from the fire. They are carbon dioxide and carbon monoxide and usually steam. Carbon monoxide is the gas that bums near the fuel with a bluish flame. It is the product of incomplete combustion. Carbon dioxide is the product of complete combustion and is invisible. Much of the fuel is wasted in the process of combustion. Smoke and soot are a loss. Smoke is composed of the little pieces of fuel which have been partly bumed, and escape with the vapor in the draft up the chimney. When wood and soft coal are burned, parts of the oily compounds are combined with the unconsumed bits of fuel and stick to the chimney flues. This is called soot. Chinmeys have to be kept free from soot, for it sometimes collects in large quantities and ignites in the chimney and bums. Ashes are the mineral substances in the fuels which will not bum. Digitized by Google THE KITCHEN FIRE 19 Kerosene Lamps I. Cleaning. Occasionally take oflf th^ burners, la3ring them on several folds of newspaper; take out the wicks, boil the burners in soda water in the proportion of one (1) teaspoonful of washing soda to one (1) quart of water. At all times keep the air holes free from dust and lamp dirt. II. Filling. Fill the lamp to within one inch of the top. Trim the wick with care ; see that it is perfectly even,

Household science and arts