Heat ; Kindling Temperature. — That fuels must be heated before they will burn is evident when one stops to think. There are fuel substances everywhere, — paper, cloth, wood, etc. These materials do not burn unless heated ; even gas does not burn by simply turning on the stopcock. But if a piece of paper is placed in contact with glowing iron, the paper burns. It burns because it is heated. If the blazing paper is placed in contact with kindling wood and coal, the kindling wood soon begins to burn because it is heated by the burning paper. The coal burns when it is heated by the burning wood. When one thinks of the ease with which paper " catches fire" and of the difficulty of making hard coal burn, it becomes evident that some substances require only a small amount of heat before they will burn, while others require 7 8 THE COOKING OF FOODS much heat. Different materials, then, require different degrees of heat to burn. The sulphur, phosphorus, and other substances on the tip of a match ignite readily. The heat that is developed by rubbing the tip over some surface is sufficient to make them burn. The burning sulphur and phosphorus heat the match stick to the temperature at which it begins to burn ; the burning match stick applied to paper heats the latter to the temperature at which it burns. The temperature to which a substance must be heated in order to burn is called the kindling temperature of that substance. Oxygen ; Draft. — If a blanket is thrown upon a burning stick of wood, the wood soon ceases to burn. The wood stops burning because the oxygen of the air is excluded from it. The act of burning, i.e. combustion, is the union of any substance with oxygen, with the result that heat and light are produced. We have learned that a fuel cannot unite with oxygen until heated to a certain temperature. And, no matter how hot it is, the fuel will not burn unless it unites with oxygen. Oxygen, then, is the third requisite for com- bustion. The necessity for a draft, i.e. a continuous supply of fresh air which furnishes oxygen, is shown by the following experiments : Experiment 1 : Lack of Draft. — Place a short candle on a pan. Light the candle and put a tall slender lamp chimney over it. Does the candle continue to burn ? Why ? * Experiment 2 : Lack of Draft. — Again light the candle and replace the chimney, but this time support it on two sticks of wood or on the handles of a knife and fork so that it will not rest directly on the pan. Place a saucer or a piece of cardboard over the top of the chimney. Does the candle continue to burn ? Why ? 1 The pnpil should record each experiment in a notebook in a methodical way, giving (a) the process, (b) the result, and (c) the conclusion or practical application. COAL AND GAS RANGES 9 Experiment 3 : Presence of Draft. — Remove the cover from the top of tUe chimney, and again light the candle. Does it burn ? Why ? Name the three requisites for combustion. Which has the higher kindling temperature, — wood or coal ? Ex- plain your answer. LESSON II Coal and Gas Ranges Examination of a Coal Range. — Remove the lids from the coal range. Note the location of the fire box. What is its Fig. I. — Coal range showing c> 10 THE COOKING OP FOODS purpose? How is the floor of the fire box constructed? Where is the check damper ? What is its purpose ? Where is the ash pan ? Where is the front damper ? What is its purpose? Note the place where the stovepipe joins the range. What is the purpose of the stovepipe ? Note the damper in the stovepipe. What is its purpose ? Note the location of the oven. By what is the oven surrounded? Find the oven damper. Open it. In what direction do the hot gases pass out when the oven damper is open ? What part of the range is heated when the oven damper is open? An open oven damper permits a direct draft to pass through the range. (See Fig. 1.)

AI-modernized reading of the original text

Heat ; Kindling Temperature. — That fuels must be heated before they will burn is evident when one stops to think. There are fuel substances everywhere, — paper, cloth, wood, etc. These materials do not burn unless heated ; even gas does not burn by simply turning on the stopcock. But if a piece of paper is placed in contact with glowing iron, the paper burns. It burns because it is heated. If the blazing paper is placed in contact with kindling wood and coal, the kindling wood soon begins to burn because it is heated by the burning paper. The coal burns when it is heated by the burning wood. When one thinks of the ease with which paper " catches fire" and of the difficulty of making hard coal burn, it becomes evident that some substances require only a small amount of heat before they will burn, while others require much heat. Different materials, then, require different degrees of heat to burn. The sulphur, phosphorus, and other substances on the tip of a match ignite readily. The heat that is developed by rubbing the tip over some surface is sufficient to make them burn. The burning sulphur and phosphorus heat the match stick to the temperature at which it begins to burn ; the burning match stick applied to paper heats the latter to the temperature at which it burns. The temperature to which a substance must be heated in order to burn is called the kindling temperature of that substance. Oxygen ; Draft. — If a blanket is thrown upon a burning stick of wood, the wood soon ceases to burn. The wood stops burning because the oxygen of the air is excluded from it. The act of burning, i.e. combustion, is the union of any substance with oxygen, with the result that heat and light are produced. We have learned that a fuel cannot unite with oxygen until heated to a certain temperature. And, no matter how hot it is, the fuel will not burn unless it unites with oxygen. Oxygen, then, is the third requisite for combustion. The necessity for a draft, i.e. a continuous supply of fresh air which furnishes oxygen, is shown by the following experiments : Experiment 1 : Lack of Draft. — Place a short candle on a pan. Light the candle and put a tall slender lamp chimney over it. Does the candle continue to burn ? Why ? * Experiment 2 : Lack of Draft. — Again light the candle and replace the chimney, but this time support it on two sticks of wood or on the handles of a knife and fork so that it will not rest directly on the pan. Place a saucer or a piece of cardboard over the top of the chimney. Does the candle continue to burn ? Why ? 1 The pupil should record each experiment in a notebook in a methodical way, giving (a) the process, (b) the result, and (c) the conclusion or practical application. COAL AND GAS RANGES 9 Experiment 3 : Presence of Draft. — Remove the cover from the top of tUe chimney, and again light the candle. Does it burn ? Why ? Name the three requisites for combustion. Which has the higher kindling temperature, — wood or coal ? Explain your answer. LESSON II Coal and Gas Ranges Examination of a Coal Range. — Remove the lids from the coal range. Note the location of the fire box. What is its Fig. I. — Coal range showing c> purpose? How is the floor of the fire box constructed? Where is the check damper ? What is its purpose ? Where is the ash pan ? Where is the front damper ? What is its purpose? Note the place where the stovepipe joins the range. What is the purpose of the stovepipe ? Note the damper in the stovepipe. What is its purpose ? Note the location of the oven. By what is the oven surrounded? Find the oven damper. Open it. In what direction do the hot gases pass out when the oven damper is open ? What part of the range is heated when the oven damper is open? An open oven damper permits a direct draft to pass through the range. (See Fig. 1.)

A text-book of cooking