Anthracite coal is next in heating power. Owing to its density it kindles slowly, but when once thoroughly ignited it burns with an intense heat, without flame, smoke, or soot, and for a long time. Bituminous coal ignites readily, burns with much flame and smoke, but yields less heat than anthracite. Soft woods kindle quickly, burn with much flame, produce intense heat, go out quickly, and leave but few coals. Hard woods kindle and burn slowly, with less flame, but afford a large mass of coals, which retain the heat a long time. It has been estimated that 1000 ft. of gas equals from 50 to 60 lbs. of coal or about 4J gallons of kerosene. (A common coal hod holds nearly 30 lbs.) Half a ton of coal equals a cord of wood. CHAPTER IX FIRES The carbon and hydro-carbons in fuel will not burn or unite with oxygen and produce rapid combustion except at a very high temperature, — that is, when made very hot. The temperature at which this union takes place is called the burning-point. This varies in different substances, and kindling means must be employed to produce it. Some substances, like the phosphorus on matches, will burn very easily when heated by friction. The phos- phorus ignites the sulphur, and the burning sulphur makes the wood hot enough to burn, and thus we have a little fire. The match burns with a bright flame because the wood has first been decomposed by the heat, gases are formed and the burning of these gases and not of the solid wood produces the flame. Any fuel that burns with a flame must be at that moment in a gaseous state. In burning gas we simply apply a lighted match, — it in- stantly heats the gas to its kindling point and we have a bright flame. We light the wick in a candle and at first it burns slowly, the wax or tallow in the candle must first melt, be absorbed by the wick, change to a vapor and when the vapor is heated to its kindling point it burns with a clear flame. If we hold the burning match near large pieces of hard wood or coal it will not make them burn, because the match will bum out before they are hot enough to take fire. But if we place paper or shavings and a pile of small pieces of soft wood under the hard wood, and apply the lighted match to the paper, we soon have a bright flame. The burning shav- 40 SCHOOL KITCHEN TEXTBOOK ings heat and kindle the soft wood ; this in turn kindles the hard wood and coal and in this way we make our fires. Hard coal is made up almost entirely of solid carbon, which no furnace heat can change into gas. As there are no gases first made by the heat, so there can be no flame pro- duced in the burning. Hard coal burns with a steady glow without flame, provided there is plenty of air to burn the carbon ; but when the coal is densely packed in the grate and the supply of air is insufficient, a poisonous gas is formed which burns with a blue flame. It disappears when the coal burns freely. This gas is known as monoxide.

AI-modernized reading of the original text

Anthracite coal is next in heating power. Owing to its density it kindles slowly, but when once thoroughly ignited it burns with an intense heat, without flame, smoke, or soot, and for a long time. Bituminous coal ignites readily, burns with much flame and smoke, but yields less heat than anthracite. Soft woods kindle quickly, burn with much flame, produce intense heat, go out quickly, and leave but few coals. Hard woods kindle and burn slowly, with less flame, but afford a large mass of coals, which retain the heat a long time. It has been estimated that 1000 ft. of gas equals from 50 to 60 lbs. of coal or about 4J gallons of kerosene. (A common coal hod holds nearly 30 lbs.) Half a ton of coal equals a cord of wood. CHAPTER IX FIRES The carbon and hydro-carbons in fuel will not burn or unite with oxygen and produce rapid combustion except at a very high temperature, — that is, when made very hot. The temperature at which this union takes place is called the burning-point. This varies in different substances, and kindling means must be employed to produce it. Some substances, like the phosphorus on matches, will burn very easily when heated by friction. The phosphorus ignites the sulphur, and the burning sulphur makes the wood hot enough to burn, and thus we have a little fire. The match burns with a bright flame because the wood has first been decomposed by the heat, gases are formed and the burning of these gases and not of the solid wood produces the flame. Any fuel that burns with a flame must be at that moment in a gaseous state. In burning gas we simply apply a lighted match, — it instantly heats the gas to its kindling point and we have a bright flame. We light the wick in a candle and at first it burns slowly, the wax or tallow in the candle must first melt, be absorbed by the wick, change to a vapor and when the vapor is heated to its kindling point it burns with a clear flame. If we hold the burning match near large pieces of hard wood or coal it will not make them burn, because the match will bum out before they are hot enough to take fire. But if we place paper or shavings and a pile of small pieces of soft wood under the hard wood, and apply the lighted match to the paper, we soon have a bright flame. The burning shav- ings heat and kindle the soft wood ; this in turn kindles the hard wood and coal and in this way we make our fires. Hard coal is made up almost entirely of solid carbon, which no furnace heat can change into gas. As there are no gases first made by the heat, so there can be no flame produced in the burning. Hard coal burns with a steady glow without flame, provided there is plenty of air to burn the carbon ; but when the coal is densely packed in the grate and the supply of air is insufficient, a poisonous gas is formed which burns with a blue flame. It disappears when the coal burns freely. This gas is known as monoxide.

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