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Oxyhydrogen is a mixture of
hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...
(H2) and
oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...
(O2) gases. This gaseous mixture is used for torches to process
refractory In materials science, a refractory material or refractory is a material that is resistant to decomposition by heat, pressure, or chemical attack, and retains strength and form at high temperatures. Refractories are polycrystalline, polyphase, ...
materials and was the first gaseous mixture used for
welding Welding is a fabrication process that joins materials, usually metals or thermoplastics, by using high heat to melt the parts together and allowing them to cool, causing fusion. Welding is distinct from lower temperature techniques such as bra ...
. 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. This mixture may also be referred to as ' (Scandinavian and German Knallgas: "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". "Brown's gas" and HHO are terms for oxyhydrogen mainly encountered in
fringe science Fringe science refers to ideas whose attributes include being highly speculative or relying on premises already refuted. Fringe science theories are often advanced by persons who have no traditional academic science background, or by researchers ...
.


Properties

Oxyhydrogen will
combust Combust can refer to: * Combust (astrological aspect), the obscuring of the unassisted viewing of a planet by the Sun's light * Combustion Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the r ...
when brought to its autoignition temperature. For the
stoichiometric Stoichiometry refers to the relationship between the quantities of reactants and products before, during, and following chemical reactions. Stoichiometry is founded on the law of conservation of mass where the total mass of the reactants equ ...
mixture, 2:1 hydrogen:oxygen, at normal
atmospheric pressure Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1013.25 millibars, ...
, 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. When ignited, the gas mixture converts to
water vapor (99.9839 °C) , - , Boiling point , , - , specific gas constant , 461.5 J/( kg·K) , - , Heat of vaporization , 2.27 MJ/kg , - , Heat capacity , 1.864 kJ/(kg·K) Water vapor, water vapour or aqueous vapor is the gaseous p ...
and releases energy, which sustains the reaction: 241.8 kJ of energy ( LHV) for every
mole Mole (or Molé) may refer to: Animals * Mole (animal) or "true mole", mammals in the family Talpidae, found in Eurasia and North America * Golden moles, southern African mammals in the family Chrysochloridae, similar to but unrelated to Talpida ...
of burned. The amount of heat energy released is independent of the mode of combustion, but the temperature of the flame varies. The maximum temperature of about is achieved with an exact
stoichiometric Stoichiometry refers to the relationship between the quantities of reactants and products before, during, and following chemical reactions. Stoichiometry is founded on the law of conservation of mass where the total mass of the reactants equ ...
mixture, about hotter than a hydrogen flame in air. When either of the gases are mixed in excess of this ratio, or when mixed with an
inert gas An inert gas is a gas that does not readily undergo chemical reactions with other chemical substances and therefore does not readily form chemical compounds. The noble gases often do not react with many substances and were historically referred to ...
like nitrogen, the heat must spread throughout a greater quantity of matter and the flame temperature will be lower.


Production by electrolysis

A pure stoichiometric mixture may be obtained by
water electrolysis Electrolysis of water, also known as electrochemical water splitting, is the process of using electricity to decompose water into oxygen and hydrogen gas by electrolysis. Hydrogen gas released in this way can be used as hydrogen fuel, or remi ...
, which uses an electric current to dissociate the water molecules: : Electrolysis: : Combustion: 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 The first law of thermodynamics is a formulation of the law of conservation of energy, adapted for thermodynamic processes. It distinguishes in principle two forms of energy transfer, heat and thermodynamic work for a system of a constant amou ...
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 The second law of thermodynamics is a physical law based on universal experience concerning heat and energy interconversions. One simple statement of the law is that heat always moves from hotter objects to colder objects (or "downhill"), unles ...
implies (see Electrolysis of water#Efficiency).


Applications


Lighting

Many forms of oxyhydrogen
lamp Lamp, Lamps or LAMP may refer to: Lighting * Oil lamp, using an oil-based fuel source * Kerosene lamp, using kerosene as a fuel * Electric lamp, or light bulb, a replaceable component that produces light from electricity * Light fixture, or li ...
s have been described, such as the limelight, which used an oxyhydrogen flame to heat a piece of
lime Lime commonly refers to: * Lime (fruit), a green citrus fruit * Lime (material), inorganic materials containing calcium, usually calcium oxide or calcium hydroxide * Lime (color), a color between yellow and green Lime may also refer to: Botany ...
to
white hot The white hot is a variation on the hot dog found primarily in the Rochester, NY area, as well as other parts of Western New York and Central New York. It is composed of a combination of uncured and unsmoked pork, beef, and veal; the lack of smo ...
incandescence. Because of the explosiveness of the oxyhydrogen, limelights have been replaced by electric lighting.


Oxyhydrogen blowpipe

The foundations of the oxy-hydrogen blowpipe were laid down by
Carl Wilhelm Scheele Carl Wilhelm Scheele (, ; 9 December 1742 – 21 May 1786) was a Swedish German pharmaceutical chemist. Scheele discovered oxygen (although Joseph Priestley published his findings first), and identified molybdenum, tungsten, barium, hyd ...
and
Joseph Priestley Joseph Priestley (; 24 March 1733 – 6 February 1804) was an English chemist, natural philosopher, separatist theologian, grammarian, multi-subject educator, and liberal political theorist. He published over 150 works, and conducted exp ...
around the last quarter of the eighteenth century. The oxy-hydrogen blowpipe itself was developed by the
Frenchman The French people (french: Français) are an ethnic group and nation primarily located in Western Europe that share a common French culture, history, and language, identified with the country of France. The French people, especially th ...
Bochard-de-Saron, the
English English usually refers to: * English language * English people English may also refer to: Peoples, culture, and language * ''English'', an adjective for something of, from, or related to England ** English national ide ...
mineralogist Mineralogy is a subject of geology specializing in the scientific study of the chemistry, crystal structure, and physical (including optical) properties of minerals and mineralized artifacts. Specific studies within mineralogy include the proce ...
Edward Daniel Clarke Edward Daniel Clarke (5 June 17699 March 1822) was an English clergyman, naturalist, mineralogist, and traveller. Life Edward Daniel Clarke was born at Willingdon, Sussex, and educated first at Uckfield School"Anthony Saunders, D.D." in Ma ...
and the American
chemist A chemist (from Greek ''chēm(ía)'' alchemy; replacing ''chymist'' from Medieval Latin ''alchemist'') is a scientist trained in the study of chemistry. Chemists study the composition of matter and its properties. Chemists carefully describe t ...
Robert Hare in the late eighteenth and early nineteenth centuries. It produced a flame hot enough to melt such
refractory In materials science, a refractory material or refractory is a material that is resistant to decomposition by heat, pressure, or chemical attack, and retains strength and form at high temperatures. Refractories are polycrystalline, polyphase, ...
materials as
platinum Platinum is a chemical element with the symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Its name originates from Spanish , a diminutive of "silver". Pla ...
,
porcelain Porcelain () is a ceramic material made by heating substances, generally including materials such as kaolinite, in a kiln to temperatures between . The strength and translucence of porcelain, relative to other types of pottery, arises main ...
,
fire brick A fire brick, firebrick, or refractory is a block of ceramic material used in lining furnaces, kilns, fireboxes, and fireplaces. A refractory brick is built primarily to withstand high temperature, but will also usually have a low thermal con ...
, and corundum, and was a valuable tool in several fields of science. It is used in the
Verneuil process The Verneuil method (or Verneuil process or Verneuil technique), also called flame fusion, was the first commercially successful method of manufacturing synthetic gemstones, developed in the late 1883 by the French chemist Auguste Verneuil. It ...
to produce synthetic corundum.


Oxyhydrogen torch

An ''oxyhydrogen torch'' (also known as ''hydrogen torch'') is an oxy-gas torch that burns hydrogen (the fuel) with oxygen (the
oxidizer An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxid ...
). It is used for cutting and
welding Welding is a fabrication process that joins materials, usually metals or thermoplastics, by using high heat to melt the parts together and allowing them to cool, causing fusion. Welding is distinct from lower temperature techniques such as bra ...
metal A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typicall ...
s,
glass Glass is a non-crystalline, often transparent, amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling ( quenching ...
es, and
thermoplastic A thermoplastic, or thermosoft plastic, is any plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling. Most thermoplastics have a high molecular weight. The polymer chains associate ...
s. 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 Platinum is a chemical element with the symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Its name originates from Spanish , a diminutive of "silver". Pla ...
, because at the time, only it could burn hot enough to melt the metal . These techniques have been superseded by the
electric arc furnace An electric arc furnace (EAF) is a furnace that heats material by means of an electric arc. Industrial arc furnaces range in size from small units of approximately one-tonne capacity (used in foundries for producing cast iron products) up to ...
.


Pseudoscientific claims

Oxyhydrogen is associated with various exaggerated claims. It is often called "Brown's gas" or "HHO gas", a term popularized by fringe physicist
Ruggero Santilli Ruggero Maria Santilli (born September 8, 1935) is an Italo-American nuclear physicist. Mainstream scientists dismiss his theories as fringe science. Biography Ruggero Maria Santilli was born September 8, 1935) in Capracotta. He studied physics ...
, 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 A fringe theory is an idea or a viewpoint which differs from the accepted scholarship of the time within its field. Fringe theories include the models and proposals of fringe science, as well as similar ideas in other areas of scholarship, such a ...
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. 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. An article in ''
Popular Mechanics ''Popular Mechanics'' (sometimes PM or PopMech) is a magazine of popular science and technology, featuring automotive, home, outdoor, electronics, science, do-it-yourself, and technology topics. Military topics, aviation and transportation o ...
'' in 2008 reported that Oxyhydrogen does not increase the fuel economy in automobiles.Water-Powered Cars: Hydrogen Electrolyzer Mod Can't Up MPGs
, 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.


References

{{Authority control Fire Chemical mixtures Electrolysis Oxygen Hydrogen technologies Hydrogen production Fuels Water fuel Industrial gases