What is the definition of combustion and is combustion possible without oxygen i.e. with other oxidants like chlorine gas?
What is the definition of combustion and is combustion possible without oxygen i.e. with other oxidants like chlorine gas?
Combustion /kəmˈbʌs.tʃən/, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. The tricky thing here is defining what “burning” means. In ordinary, everyday burning, a fuel reacts with the oxygen in the air. So, in ordinary circumstances burning does not occur without oxygen.
Now to expand and generalize our understanding, we need to recognize that substances other than oxygen can be oxidizers. So, if we consider a wider range of possibilities, it is clear that some types of burning certainly can occur without oxygen.
For example, pyrotechnic (and propellant) reactions are nearly always described as “burning.” By definition, pyrotechnic materials are “self contained” systems that react within themselves, and do not require access to the air. Pyrotechnic materials are self contained because they are mixtures of solid fuel with solid oxidizers. The original, quintessential pyrotechnic material: black powder, is a mixture of potassium nitrate (oxidizer,) charcoal, and sulfur (both fuels.)
It could be argued that pyrotechnic reactions are not exempt from requiring oxygen, since most pyrotechnic oxidizers work by decomposing and releasing oxygen during the reaction. However, they don’t need contact with atmospheric oxygen. Furthermore, there are oxidizers that don’t contain any oxygen. For example, sulfur can act as the oxidizer in pyrotechnic reactions with various metal fuels. Mixtures of magnesium/sulfur, aluminum/sulfur/, and zinc/sulfur, are viable pyrotechnic compositions. The zinc/sulfur system has actually been used extensively in the past as a propellant by rocketry hobbyists.
Teflon, which is a fluorocarbon that contains no oxygen, can be a potent pyrotechnic oxidizer. A Teflon/magnesium composition is the basis of infrared decoy flares (used as defense against heat seeking air-to-air missiles.)
If we shift our attention away from pyrotechnics and think about gaseous oxidizers, there are several gases, other than oxygen, that are potent oxidizers. Ozone and fluorine actually more potent oxidizers than oxygen gas itself. Chlorine is also a strong oxidizer. In fact, a candle will burn in a jar filled with chlorine. This makes a very smoky flame, but it burns well. There are YouTube videos (of course!) showing this phenomenon.
The tricky thing here is defining what “burning” means. In ordinary, everyday burning, a fuel reacts with the oxygen in the air. So, in ordinary circumstances burning does not occur without oxygen.
Now to expand and generalize our understanding, we need to recognize that substances other than oxygen can be oxidizers. So, if we consider a wider range of possibilities, it is clear that some types of burning certainly can occur without oxygen.
For example, pyrotechnic (and propellant) reactions are nearly always described as “burning.” By definition, pyrotechnic materials are “self contained” systems that react within themselves, and do not require access to the air. Pyrotechnic materials are self contained because they are mixtures of solid fuel with solid oxidizers. The original, quintessential pyrotechnic material: black powder, is a mixture of potassium nitrate (oxidizer,) charcoal, and sulfur (both fuels.)
It could be argued that pyrotechnic reactions are not exempt from requiring oxygen, since most pyrotechnic oxidizers work by decomposing and releasing oxygen during the reaction. However, they don’t need contact with atmospheric oxygen. Furthermore, there are oxidizers that don’t contain any oxygen. For example, sulfur can act as the oxidizer in pyrotechnic reactions with various metal fuels. Mixtures of magnesium/sulfur, aluminum/sulfur/, and zinc/sulfur, are viable pyrotechnic compositions. The zinc/sulfur system has actually been used extensively in the past as a propellant by rocketry hobbyists.
Teflon, which is a fluorocarbon that contains no oxygen, can be a potent pyrotechnic oxidizer. A Teflon/magnesium composition is the basis of infrared decoy flares (used as defense against heat seeking air-to-air missiles.)
If we shift our attention away from pyrotechnics and think about gaseous oxidizers, there are several gases, other than oxygen, that are potent oxidizers. Ozone and fluorine actually more potent oxidizers than oxygen gas itself. Chlorine is also a strong oxidizer. In fact, a candle will burn in a jar filled with chlorine. This makes a very smoky flame, but it burns well. There are YouTube videos (of course!) showing this phenomenon.
