Oxyhydrogen#Oxyhydrogen torch
{{short description|Explosive mixture of hydrogen and oxygen gases}}
{{Redirect|Knallgas|bacteria which oxidize hydrogen|Knallgas-bacteria}}
{{Use mdy dates|date=November 2019}}
Image:Electrolyser 1884.png for producing oxyhydrogen]]
Oxyhydrogen is a mixture of hydrogen (H2) and oxygen (O2) gases. This gaseous mixture is used for torches to process refractory materials and was the first
{{citation
|author = Howard Monroe Raymond
|title = Modern Shop Practice volume 1
|chapter = Oxy-Hydrogen Welding
|publisher = American Technical Society
|year = 1916
|chapter-url = http://chestofbooks.com/crafts/machinery/Shop-Practice-V1/Oxy-Hydrogen-Welding.html
|url-status = live
|archive-url = https://web.archive.org/web/20110306125405/http://chestofbooks.com/crafts/machinery/Shop-Practice-V1/Oxy-Hydrogen-Welding.html
|archive-date = March 6, 2011
|author-link = Howard Monroe Raymond
}}
gaseous mixture used for welding. Theoretically, a ratio of 2:1 hydrogen:oxygen is enough to achieve maximum efficiency; in practice a ratio 4:1 or 5:1 is needed to avoid an oxidizing flame.
{{Cite book
|last = Viall
|first = Ethan
|title = Gas Torch and Thermite Welding
|publisher = McGraw-Hill
|year = 1921
|page = [https://archive.org/details/gastorchthermitw00vialrich/page/10 10]
|url = https://archive.org/details/gastorchthermitw00vialrich
|url-status = live
|archive-url = https://web.archive.org/web/20160803205751/https://archive.org/details/gastorchthermitw00vialrich
|archive-date = August 3, 2016
}}
This mixture may also be referred to as {{lang|de|Knallgas}} (Scandinavian and German {{linktext|Knallgas}}; {{literal|bang-gas}}), although some authors define knallgas to be a generic term for the mixture of fuel with the precise amount of oxygen required for complete combustion, thus 2:1 oxyhydrogen would be called "hydrogen-knallgas".W. Dittmar, "Exercises in quantitative chemical analysis", 1887, [https://archive.org/details/exercisesinquan00dittgoog/page/n207 p. 189] {{webarchive|url=https://web.archive.org/web/20140627184941/http://books.google.com/books?id=ayFDAAAAIAAJ&pg=PA189 |date=June 27, 2014 }}
"Brown's gas" and HHO are terms for oxyhydrogen originating in pseudoscience, although {{chem2|x H2 + y O2}} is preferred due to {{chem2|HHO}} meaning {{chem2|H2O}}.
Properties
Oxyhydrogen will combust when brought to its autoignition temperature. For the stoichiometric mixture in air, at normal atmospheric pressure, autoignition occurs at about 570 °C (1065 °F). The minimum energy required to ignite such a mixture, at lower temperatures, with a spark is about 20 microjoules. At standard temperature and pressure, oxyhydrogen can burn when it is between about 4% and 95% hydrogen by volume.{{cite journal |last1=Moyle |first1=Morton |last2=Morrison |first2=Richard |last3=Churchill |first3=Stuart |title=Detonation Characteristics of Hydrogen Oxygen Mixtures |journal=AIChE Journal |date=March 1960 |volume=6 |issue=1 |pages=92–96 |doi=10.1002/aic.690060118 |bibcode=1960AIChE...6...92M |hdl=2027.42/37308 |url=https://deepblue.lib.umich.edu/bitstream/handle/2027.42/37308/690060118_ftp.pdf?sequence=1&isAllowed=y|hdl-access=free }}
{{Cite book
|last = O'Connor
|first = Ken
|title = NASA Glenn Research Center Glenn Safety Manual
|chapter = Hydrogen
|chapter-url = http://www.nfpa.org/assets/files/pdf/codesstandards/hcgnasahydrogench06.pdf
|url-status = dead
|archive-url = https://web.archive.org/web/20130202184446/http://www.nfpa.org/assets/files/pdf/codesstandards/hcgnasahydrogench06.pdf
|archive-date = February 2, 2013
}}
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 {{chem2|H2}} burned. The amount of heat energy released is independent of the mode of combustion, but the temperature of the flame varies.{{cite EB1911 |wstitle=Oxyhydrogen Flame |volume=20 |page=424}} The maximum temperature of about {{convert|2800|°C|°F|-2}} is achieved with an exact stoichiometric mixture, about {{convert|700|C-change|F-change|-2}} hotter than a hydrogen flame in air.
{{Cite web
|last = Calvert
|first = James B.
|title = Hydrogen
|publisher = University of Denver
|date = April 21, 2008
|access-date = April 23, 2009
|url = http://mysite.du.edu/~jcalvert/phys/hydrogen.htm
|quote = An air-hydrogen torch flame reaches 2045 °C, while an oxyhydrogen flame reaches 2660 °C.
|url-status = live
|archive-url = https://web.archive.org/web/20090418033147/http://mysite.du.edu/~jcalvert/phys/hydrogen.htm
|archive-date = April 18, 2009
}}
{{Cite web
|title = Adiabatic Flame Temperature
|work = The Engineering Toolbox
|access-date = April 23, 2009
|url = http://www.engineeringtoolbox.com/adiabatic-flame-temperature-d_996.html
|url-status = live
|archive-url = https://web.archive.org/web/20080128053804/http://www.engineeringtoolbox.com/adiabatic-flame-temperature-d_996.html
|archive-date = January 28, 2008
}}
"Oxygen as Oxidizer: 3473 K, Air as Oxidizer: 2483 K"
{{Cite web
|title = Temperature of a Blue Flame
|access-date = April 5, 2008
|url = http://hypertextbook.com/facts/1998/JamesDanyluk.shtml
|url-status = live
|archive-url = https://web.archive.org/web/20080316074504/http://hypertextbook.com/facts/1998/JamesDanyluk.shtml
|archive-date = March 16, 2008
}}
"Hydrogen in air: 2,400 K, Hydrogen in Oxygen: 3,080 K"
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, reducing flame temperature.
Oxyhydrogen is explosive and can detonate when ignited, releasing a large amount of energy. This is often demonstrated in classroom environments in which teachers fill a balloon with the gas, due to the easy access of hydrogen and oxygen.{{cite thesis |last= Vernon|first= Julia|date= August 2011|title= Acoustical Characterization of Exploding Hydrogen-Oxygen Balloons|url= https://physics.byu.edu/docs/thesis/288|degree= |chapter= |publisher= |docket= |oclc= |access-date=August 15, 2024}}
Production by electrolysis
A precisely stoichiometric mixture may be obtained by water electrolysis, which uses an electric current to dissociate the water molecules:
: Electrolysis: {{chem2|2 H2O -> 2 H2 + O2}}
: Combustion: {{chem2|2 H2 + O2 -> 2 H2O}}
William Nicholson was the first to decompose water in this manner in 1800. In theory, the input energy of a closed system always equals the output energy, as the first law of thermodynamics states. However, in practice no systems are perfectly closed, and the energy required to generate the oxyhydrogen always exceeds the energy released by combusting it, even at maximum practical efficiency, as the second law of thermodynamics implies (see Electrolysis of water#Efficiency).
Applications
Image:Limelight diagram.svgs used an oxyhydrogen flame as a high-temperature heat source]]
= Lighting =
Many forms of oxyhydrogen lamps have been described, such as the limelight, which used an oxyhydrogen flame to heat a piece of quicklime to white hot incandescence. Because of the explosiveness of the oxyhydrogen, limelights have been replaced by electric lighting.
=Oxyhydrogen blowpipe=
Image:Blowpipe - circa 1827.jpg]] The foundations of the oxy-hydrogen blowpipe were laid down by Carl Wilhelm Scheele and Joseph Priestley around the last quarter of the eighteenth century. The oxy-hydrogen blowpipe itself was developed by the Frenchman Bochard-de-Saron, the English mineralogist Edward Daniel Clarke and the American chemist Robert Hare in the late 18th and early 19th centuries.{{Cite journal| publisher = Manufacturing chemists| title = Report on the Development of the Chemical Arts During the Last Ten Years| journal=Chemical News |date = 1875|last=Hofmann |first=A. W. |url=https://books.google.com/books?id=v2sfCwFk28AC&pg=RA1-PA153}} 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.{{cite book | last = Griffin | first = John Joseph | title = A Practical Treatise on the Use of the Blowpipe in Chemical and Mineral Analysis | publisher = R. Griffin & co.| year = 1827 | location = Glasgow | url = https://archive.org/details/apracticaltreat00grifgoog }} It is used in the Verneuil process to produce synthetic corundum.{{cite encyclopedia|encyclopedia= Encyclopaedia Britannica|title= Verneuil process |url= https://www.britannica.com/topic/Verneuil-process|access-date=July 11, 2018 |language= en|date= October 22, 2013}}
=Oxyhydrogen torch=
{{See also|Thermal lance|Gas burner}}
An oxyhydrogen torch (also known as hydrogen torch) is an oxy-gas torch that burns hydrogen (the fuel) with oxygen (the oxidizer). It is used for cutting and welding{{citation |chapter= 24.4 Oxyhydrogen welding |title= Manufacturing technology: foundry, forming and welding |author= P. N. Rao |edition= 2 |publisher= Tata McGraw-Hill Education |year= 2001 |isbn= 978-0-07-463180-5 |pages= 373–374 |chapter-url= https://books.google.com/books?id=I4RZQaxCRP8C&q=oxyhydrogen+welding&pg=PA373 |url-status= live |archive-url= https://web.archive.org/web/20140627193730/http://books.google.com/books?id=I4RZQaxCRP8C&pg=PA373&dq=oxyhydrogen+welding&hl=en&ei=RP5eTdDhGtLB4gb0k7GVCg&sa=X&oi=book_result&ct=result&resnum=3&ved=0CDYQ6AEwAg |archive-date= June 27, 2014 }} metals, glasses, and thermoplastics.{{cite book |title=Chemical Discovery and Invention in the Twentieth Century |first=William Augustus |last=Tilden |publisher=Adamant Media Corporation |isbn=978-0-543-91646-4|url=https://books.google.com/books?id=Qu-fYeT8UKoC&q=Oxyhydrogen&pg=PP133 |page=80 |year=1926}}
Due to competition from arc welding and other oxy-fuel torches such as the acetylene-fueled cutting torch, the oxyhydrogen torch is seldom used today, but it remains the preferred cutting tool in some niche applications.
Oxyhydrogen was once used in working platinum, because at the time, only it could burn hot enough to melt the metal {{convert|1768.3|°C|°F}}. These techniques have been superseded by the electric arc furnace.
Pseudoscientific claims
{{anchor|HHO gas}} {{anchor|Brown's gas}}
Oxyhydrogen is associated with various exaggerated claims.{{Cite web|url=http://www.eagle-research.com/browngas/myth/myth.php|title=Eagle Research Institute - Brown's Gas - Myth-conceptions|archive-url=https://web.archive.org/web/20190418000551/http://www.eagle-research.com/browngas/myth/myth.php|access-date=July 11, 2018|archive-date=April 18, 2019}}{{cite journal | last=Ball | first=Philip | title=Burning water and other myths | journal=News@nature | publisher=Springer Nature | date=September 10, 2007 | issn=1744-7933 | doi=10.1038/news070910-13 | s2cid=129704116 | doi-access=free }}{{cite journal|last=Ball|first=Philip|year=2006|title=Nuclear waste gets star attention|journal=News@nature|issn=1744-7933|doi=10.1038/news060731-13|s2cid=121246705}} It is often called "Brown's gas" or "HHO gas", a term popularized by fringe physicist{{cite news|last=Weimar|first=Carrie|title=Snubbed By Mainstream, Scientist Sues|url=https://news.google.com/newspapers?id=BYtIAAAAIBAJ&pg=1570,2000590&dq=ruggero-santilli+fringe&hl=en|access-date=February 3, 2011|newspaper=St. Petersburg Times|date=May 7, 2007}} Ruggero Santilli, who claimed that his HHO gas, produced by a special apparatus, is "a new form of water", with new properties, based on his fringe theory of "magnecules".
Many other pseudoscientific claims have been made about oxyhydrogen, like an ability to neutralize radioactive waste, help plants to germinate, and more.
Oxyhydrogen is often mentioned in conjunction with vehicles that claim to use water as a fuel. The most common and decisive counter-argument against producing this gas on board to use as a fuel or fuel additive is that more energy is always needed to split water molecules than is recouped by burning the resulting gas.{{cite book | last=Schadewald | first=R.J. | title=Worlds of Their Own: A Brief History of Misguided Ideas: Creationism, Flat-Earthism, Energy Scams, and the Velikovsky Affair | publisher=Xlibris US | year=2008 | isbn=978-1-4628-1003-1 | url=https://books.google.com/books?id=m9BM6DzFGGwC | access-date=July 11, 2018 }} Additionally, the volume of gas that can be produced for on-demand consumption through electrolysis is very small in comparison to the volume consumed by an internal combustion engine.{{cite news|last=Simpson|first=Bruce|title=The proof that HHO is a scam|url=http://www.aardvark.co.nz/hho_scam.shtml|access-date=February 12, 2012|newspaper=Aardvark Daily|date=May 2008|url-status=live|archive-url=https://web.archive.org/web/20120211215854/http://www.aardvark.co.nz/hho_scam.shtml|archive-date=February 11, 2012}}
An article in Popular Mechanics in 2008 reported that oxyhydrogen does not increase the fuel economy in automobiles.[http://www.popularmechanics.com/cars/a3499/4276846/ Water-Powered Cars: Hydrogen Electrolyzer Mod Can't Up MPGs] {{webarchive|url=https://web.archive.org/web/20150320180153/http://www.popularmechanics.com/cars/a3499/4276846/ |date=March 20, 2015 }}, Mike Allen, August 7, 2008, Popularmechanics.com
"Water-fueled" cars should not be confused with hydrogen-fueled cars, where the hydrogen is produced elsewhere and used as fuel or where it is used as fuel enhancement.