The Breaking of Chimneys.—Chim neys break from misuse. A wrong number may break or melt; if the burner is foul, the glass may break; a gust of cold air on a hot chimney may break it; a gas chimney may break or melt from a hole in the man tle; the hole lets a jet of flame di rectly against the chimney, the explo sion of lighting breaks the mantle, and the broken mantle breaks the chimney.
Whenever the chimney is touched by the flame it melts or breaks. Its shape prevents touching, unless through some misuse. In central-draught lamps the flame is between two draughts—the central and the outer one. When the burner is foul, this outer draught is partly stopped, and the flame gets pushed too near or against the chim ney, and breaks or melts it.
Chimneys cannot be made to resist misuse or accidents.
To Prevent Explosions of Lamps.— One common cause of explosions is the upsetting of a lamp; hence select a lamp which has a broad, solid base rather than one that appears top heavy.
Never fill a lamp while it is burn ing. To avoid this, buy lamps that have no opening but the one made for the wick. While it is a convenience to have a lamp with a special opening for filling, it is not safe, as children and others will sometimes undertake to fill it while burning, which may lead to an explosion. Also, when lamps have a special opening for fill ing, the wick is likely to be neglected until it becomes charred and the burn er gets clogged up and dirty. In this condition the lamp is very apt to explode, because the charred por tion of a wick takes fire, the oil that runs over burns, and heat is generated so low down in the burner that any volatile gases thrown off by the oil may become ignited. The best oil commences to evaporate at about 110° and ignites at NV, and this vapor, like that which rises from gasoline, benzine, or naphtha, is highly inflam mable and explosive. Hence do not let a lamp stand with little oil in it, or light one which has stood partly empty for a long time.
The best lamps have an extinguisher to put out the flame, but if this is lacking, do not blow out the lamp without first turning down the wick, especially if the lamp has been burned for some time and the burner and ad jacent parts are hot. The fact that you may have done this safely many times does not prove that under cer tain conditions a volatile gas from the oil may not meet the flame and cause explosion.
Always turn the lamp low when carrying it about, as movement from place to place in sudden draughts may bring the flame in contact with the gases that form when oil is burning, and that are more or less disturbed by the jar of walking.
Chemistry of Lamps. — The chem istry of burning kerosene is very sim ple. The oil is composed of two inflammable substances, a gas (hydro gen), which burns with a blue flame and a very intense heat, and a solid (carbon), which consists of very mi nute particles in chemical combination with the hydrogen. When the lamp is lit the flame is raised to a temperature that admits of chemical union with the oxygen of the air. The hydrogen first burns, and produces sufficient heat to allow the oxygen to ignite with the carbon. When for any reason there is an excess of oil as when a lamp is turned too high, or when the heat of the flame is reduced as when the lamp is turned too low, the heat of the burning hydrogen is not sufficient to ignite all of the solid carbon, some of which escapes in the form of a finely divided black solid, and we say that the lamp smokes. This solid carbon is what we call soot, or lampblack. Commercial lampblack is thus ob tained.
When we breathe the air, a very similar process takes place in our lungs, the oxygen of the air uniting with the waste substances in the blood and purifying them by a kind of com bustion. Hence every flame in a room robs the air of a certain amount of oxygen that is essential to human life.
This process, both in the lamp and in the lungs, produces a compound of oxygen and carbon called carbon di oxygen, or carbonic-acid gas. Human beings would immediately suffocate in a room quite filled with carbonic-acid gas, as it contains no free oxygen in the form available for human use. When unburned particles of carbon are thrown off in the form of smoke or soot, the finest of them are sus pended in the air and find their way into the lungs. Nothing offers so much resistance to chemical and vital forces as pure carbon; hence these particles are difficult to dislodge and exceed ingly harmful.