Flame
in chemistry, a shell of incandescent matter surrounding a mass of combustible vapor. To produce flame it is therefore necessary that the burning body should be capable of volatilization just below the temperature at which it undergoes combustion. Charcoal or iron will burn with a steady glow, more or less luminous according to the medium in which they are burnt, neither of these substances being susceptible of volatilization at the temperature at which combustion takes place. A piece of wood or paper, on the contrary, burns with a large luminous flame, in consequence of the combustible matter of which it is composed rising in vapor or becoming converted into mixed gases at the temperature required for kindling the substance. Flame is, in fact, produced whenever a continuous supply of inflammable vapor or gas is made to combine with a supporter of combustion, such as the atmosphere, at a sufficiently elevated temperature to cause ignition. The heating power of a flame is in direct proportion to the energy of the chemical action that takes place, those flames being hottest and least luminous which proceed from gases containing no solid particles, as in the case of a mixture of oxygen FLAME THROWERS in the form of smoke. The flames used for illuminating purposes are all produced by the combustion of compounds containing carbon and hydrogen. Besides the proper proportions of gaseous and solid matter contained in illuminating substances, care must be taken to regulate the supply of air. The ARGAND LAMP (q. v.) and chimney, as applied to gas and camphene, are examples of this.
Flame has three distinct parts: The central or non-luminous part, where there is no combustion, but where the carbon begins to separate from the hydrogen; the second or luminous part, where the carbon is for a moment free and heated to a white heat; and the exterior part, which is the hottest, and where the combustion is complete. It is easy now to understand of what importance is the form of the burner, and how it may be modified accordingly as we desire light or heat. If we wish light the carbon must be protected for some seconds from contact with the air; but not long enough to allow it to pass off unconsumed. If, on the contrary, heat is desired, the carbon must be burned as quickly as possible. The German chemist Bunsen constructed a gas burner after this theory, which is perfectly adapted to the production of heat. Every mixture of gases requires a certain temperature to inflame it; and if the temperature be not reached, the mixture does not take fire; we may thus cool down a flame so much that it goes out by placing over it a small coil of cold copper wire, whereas if the coil be previously heated, the flame will continue to burn.
If a piece of wire gauze be held close over a jet of gas and the gas lit, the gauze may be removed several inches above the jet, and yet the inflammable gas below will not take fire, the flame burning only above the gauze.
SAFETY LAMP.
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