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Support this channel on Patreon [ Ссылка ] Check out my store front [ Ссылка ] For the stoichiometric mixture, 2:1 hydrogen:oxygen, at normal atmospheric pressure, autoignition
occurs at about 570 °C (1065 °F).[5] The minimum energy required to ignite such a mixture with a spark is about 20 microjoules.[5]
At standard temperature and pressure, oxyhydrogen can burn when it is between about 4% and 95% hydrogen by volume.[5]
When ignited, the gas mixture converts to water vapor and releases energy, which sustains the reaction: 241.8 kJ of energy
(LHV) for every mole of H2 burned. The amount of heat energy released is independent of the mode of combustion, but the
temperature of the flame varies.[6] The maximum temperature of about 2,800 °C (5,070 °F) is achieved with an exact stoichiometric
mixture, about 700 °C (1,292 °F) hotter than a hydrogen flame in air.[7][8][9] When either of the gases are mixed in excess of this
ratio, or when mixed with an inert gas like nitrogen, the heat must spread throughout a greater quantity of matter and the
temperature will be lower.[6]Production[edit]A pure stoichiometric mixture may be obtained by water electrolysis, which uses an
electric current to dissociate the water molecules:electrolysis: 2 H2O ? 2 H2 + O2 combustion: 2 H2 + O2 ? 2 H2O
William Nicholson was the first to decompose water in this manner in 1800. The energy required to generate the oxyhydrogen always
exceeds the energy released by combusting it, even at maximum efficiency, the input energy of a closed system will always equal
the output energy, as the first law of thermodynamics states. (See Electrolysis of water#Efficiency).Applications[edit]Limelights
used an oxyhydrogen flame as a high-temperature heat source Lighting[edit] Many forms of oxyhydrogen lamps have been described,
such as the limelight, which used an oxyhydrogen flame to heat a piece of lime to white hot incandescence.[10] Because of the
explosiveness of the oxyhydrogen, limelights have been replaced by electric lighting.Oxyhydrogen blowpipe[edit] Nineteenth
century bellows-operated oxy-hydrogen blowpipe, including two different types of flashback arrestor
The oxy-hydrogen blowpipe was developed by English mineralogist Edward Daniel Clarke and American chemist Robert Hare in the
early nineteenth century. It produced a flame hot enough to melt such refractory materials as platinum, porcelain, fire brick,
and corundum, and was a valuable tool in several fields of science.[11] It is used in the Verneuil process to produce synthetic
corundum.[citation needed]Oxyhydrogen torch[edit]An oxyhydrogen torch is an oxy-gas torch, which burns hydrogen (the fuel) with
oxygen (the oxidizer). It is used for cutting and welding,[12] metals, glass, and thermoplastics.[10]Due to competition from the
acetylene-fueled cutting torch and from arc welding, the oxyhydrogen torch is seldom used today, but it remains the preferred
cutting tool in some niche applications—see oxy-fuel welding and cutting.
Oxyhydrogen was once used in working platinum because at the time such a torch was the only device that could attain the temperature
required to melt the metal 1,768.3 °C (3,214.9 °F).[6] These techniques have been superseded by the electric arc furnace.
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