arrangement of continents by plate tectonics influences the long term evolution of the atmosphere by transferring carbon dioxide to and from large continental carbonate stores Free oxygen did not exist in the atmosphere until about billion years ago during the Great Oxygenation Event and its appearance is indicated by the end of the banded iron formations Before this time, any oxygen produced by photosynthesis was consumed by oxidation of reduced materials, notably iron Molecules of free oxygen did not start to accumulate in the atmosphere until the rate of production of oxygen began to exceed the availability of reducing materials This point signifies a shift from a reducing atmosphere to an oxidizing atmosphere O showed major variations until reaching a steady state of more than % by the end of the Precambrian The following time span was the Phanerozoic eon, during which oxygen breathing metazoan life forms began to appear The amount of oxygen in the atmosphere has fluctuated over the last million years, reaching a peak of about % around million years ago, significantly higher than today's % Two main processes govern changes in the atmosphere Plants use carbon dioxide from the atmosphere, releasing oxygen Breakdown of pyrite and volcanic eruptions release sulfur into the atmosphere, which oxidizes and hence reduces the amount of oxygen in the atmosphere However, volcanic eruptions also release carbon dioxide, which plants can convert to oxygen The exact cause of the variation of the amount of oxygen in the atmosphere is not known Periods with much oxygen in the atmosphere are associated with rapid development of animals Today's atmosphere contains % oxygen, which is high enough for this rapid development of animals Currently, anthropogenic greenhouse gases are accumulating in the atmosphere, which is the main cause of global warming Climate during geological ages edit See also Timeline of glaciation Timeline of glaciations, shown in blue The Huronian glaciation, is the first known glaciation in Earth's history, and lasted from million years ago The Cryogenian glaciation lasted from million years ago The Andean Saharan glaciation lasted from – million years ago The Karoo glaciation lasted from – million years ago The Quaternary glaciation is the current glaciation period and begun million years ago Precambrian climate edit Main article Precambrian The climate of the late Precambrian showed some major glaciation events spreading over much of the earth At this time the continents were bunched up in the Rodinia supercontinent Massive deposits of tillites are found and anomalous isotopic signatures are found, which gave rise to the Snowball Earth hypothesis As the Proterozoic Eon drew to a close, the Earth started to warm up By the dawn of the Cambrian and the Phanerozoic, life forms were abundant in the Cambrian explosion with average global temperatures of about °C Phanerozoic climate edit Main article Phanerozoic million years of climate change Major drivers for the preindustrial ages have been variations of

the sun, volcanic ashes and exhalations, relative movements of the earth towards the sun and tectonically induced effects as for major sea currents, watersheds and ocean oscillations In the early Phanerozoic, increased atmospheric carbon dioxide concentrations have been linked to driving or amplifying increased global temperatures Royer et al found a climate sensitivity for the rest of the Phanerozoic which was calculated to be similar to today's modern range of values The difference in global mean temperatures between a fully glacial Earth and an ice free Earth is estimated at approximately °C, though far larger changes would be observed at high latitudes and smaller ones at low latitudes citation needed One requirement for the development of large scale ice sheets seems to be the arrangement of continental land masses at or near the poles The constant rearrangement of continents by plate tectonics can also shape long term climate evolution However, the presence or absence of land masses at the poles is not sufficient to guarantee glaciations or exclude polar ice caps Evidence exists of past warm periods in Earth's climate when polar land masses similar to Antarctica were home to deciduous forests rather than ice sheets The relatively warm local minimum between Jurassic and Cretaceous goes along with an increase of subduction and mid ocean ridge volcanism due to the breakup of the Pangea supercontinent Superimposed on the long term evolution between hot and cold climates have been many short term fluctuations in climate similar to, and sometimes more severe than, the varying glacial and interglacial states of the present ice age Some of the most severe fluctuations, such as the Paleocene Eocene Thermal Maximum, may be related to rapid climate changes due to sudden collapses of natural methane clathrate reservoirs in the oceans citation needed A similar, single event of induced severe climate change after a meteorite impact has been proposed as reason for the Cretaceous–Paleogene extinction event Other major thresholds are the Permian Triassic, and Ordovician Silurian extinction events with various reasons suggested Quaternary climate edit Main article Quaternary See also List of large scale temperature reconstructions of the last , years Ice core data for the past , years Note length of glacial cycles averages ~ , years Blue curve is temperature, green curve is CO , and red curve is windblown glacial dust loess Today's date is on the left side of the graph The Quaternary sub era includes the current climate There has been a cycle of ice ages for the past – million years starting before the Quaternary in the late Neogene Period Note in the graphic on the right the strong , year periodicity of the cycles, and the striking asymmetry of the curves This asymmetry is believed to result from complex interactions of feedback mechanisms It has been observed that ice ages deepen by progressive steps, but the recovery to interglacial conditions occurs in one big step The graph below shows the temperature change over the past years, from various sources The thick black curve is an average Holocene Temperature Variations Climate forcings edit Radiative forcings, IPCC Main article Climate change § Causes The climate forcing is the difference of radiant energy sunlight received by the Earth and the outgoing longwave radiation back to space The radiative forcing is quantified based on the CO amount in the tropopause, in units of watts per square meter to the Earth's surface Dependent on the radiative balance of incoming and outgoing energy, the Earth either warms up or cools down Earth radiative balance originates from changes in solar insolation and the concentrations of greenhouse gases and aerosols Climate change may be due to internal processes in Earth sphere's and or following external forcings Internal processes and forcings edit The Earth's climate system involves the study of the atmosphere, biosphere, cryosphere, hydrosphere, and lithosphere, and the sum of these processes from Earth sphere's is considered the processes affecting the climate Greenhouse gases act as the internal forcing of the climate system Particular interests in climate science and paleoclimatology focuses on the study of Earth climate sensitivity, in response to the sum of forcings Examples Thermohaline circulation Hydrosphere Life Biosphere External forcings edit The Milankovitch cycles determine Earth distance and position to the Sun The solar insolation, is the total amount of solar radiation received by Earth Volcanic eruptions, are considered an external forcing Human changes of the composition of the atmosphere or land use Dendroclimatology is the science of determining past climates from trees primarily properties of the annual tree rings Tree rings are wider when conditions favor growth, narrower when times are difficult Other properties of the annual rings, such as maximum latewood density MXD have been shown to be better proxies than simple ring width Using tree rings, scientists have estimated many local climates for hundreds to thousands of years previous By combining multiple tree ring studies sometimes with other climate proxy records , scientists have estimated past regional and global climates see Temperature record of the past years Contents hide Advantages Limitations Confounding factors Climate factors Non climate factors Non linear effects Botanical inferences to correct for confounding factors Divergence problem Geographic coverage Annular resolution Collection difficulties Other measurements Notes See also References External links Advantages edit Tree rings are especially useful as climate proxies in that they can be well dated via matching of the rings from sample to sample, i e dendrochronology This allows extension backwards in time using deceased tree samples, even using samples from buildings or from archeological digs Another advantage of tree rings is that they are clearly demarked in annual increments, as opposed to other proxy methods such as boreholes Furthermore, tree rings respond to multiple climatic effects temperature, moisture, cloudiness , so that various aspects of climate not just temperature can be studied However, this can be a double edged sword as discussed in Climate factors Limitations edit Along with the advantages of dendroclimatology are some limitations confounding factors, geographic coverage, annular resolution, and collection difficulties The field has developed various methods to partially adjust for these challenges Confounding factors edit There are multiple climate and non climate factors as well as nonlinear effects that impact tree ring width Methods to isolate single factors of interest include botanical studies to calibrate growth influences and sampling of limiting stands those expected to respond mostly to the variable of interest Climate factors edit Climate factors that affect trees include temperature, precipitation, sunlight, and wind To differentiate among these factors, scientists collect information from limiting stands An example of a limiting stand is the upper elevation treeline here, trees are expected to be more affected by temperature variation which is limited than precipitation variation which is in excess Conversely, lower elevation treelines are expected to be more affected by precipitation changes than temperature variation This is not a perfect work around as multiple factors still impact trees even at the limiting stand , but it helps In theory, collection of samples from nearby limiting stands of different types e g upper and lower treelines on the same mountain should allow mathematical solution for multiple climate factors However, this method is rarely used Non climate factors edit Non climate factors include soil, tree age, fire, tree to tree competition, genetic differences, logging or other Carbon , C, or radiocarbon, is a radioactive isotope of carbon with a nucleus containing protons and neutrons Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and colleagues to date archaeological, geological and hydrogeological samples Carbon was discovered on February , by Martin Kamen and Sam Ruben at the University of California Radiation Laboratory in Berkeley Its existence had been suggested by Franz Kurie in There are three naturally occurring isotopes of carbon on Earth % of the carbon is carbon , % is carbon , and carbon occurs in trace amounts, i e , making up about or atoms per atoms of the carbon in the atmosphere The half life of carbon is , ± years Carbon decays into nitrogen through beta decay A gram of carbon containing atom of carbon per atoms will emit citation needed beta rays per second The primary natural source of carbon on Earth is cosmic ray action on nitrogen in the atmosphere, and it is therefore a cosmogenic nuclide However, open air nuclear testing between – contributed to this pool The different isotopes of carbon do not differ appreciably in their chemical properties This is used in chemical and biological research, in a technique called carbon labeling carbon atoms can be used to replace nonradioactive carbon, in order to trace chemical and biochemical reactions involving carbon atoms from any given organic compound Contents hide Radioactive decay and detection Radiocarbon dating Origin Natural production in the atmosphere Other carbon sources Formation during nuclear tests Occurrence Dispersion in the environment Total inventory In fossil fuels In the human body See also References Further reading External links Radioactive decay and detection edit Carbon goes through radioactive beta decay mathrm{~^{ }_{ }C} rightarrow mathrm{~^{ }_{ }N}+ e^ + bar{ nu}_e By emitting an electron and an electron antineutrino, one of the neutrons in the carbon atom decays to a proton and the carbon half life of years decays into the stable non radioactive isotope nitrogen The emitted beta particles have a maximum energy of keV, while their average clarification needed energy is keV These are relatively low energies the maximum distance traveled is estimated to be cm in air and mm in body tissue The fraction of the radiation transmitted through the dead skin layer is estimated to be Small amounts of carbon are not easily detected by typical Geiger–Müller G M detectors it is estimated that G M detectors will not normally detect contamination of less than about disintegration per minute µCi Liquid scintillation counting is the preferred method The G M counting efficiency is estimated to be % The half distance layer in water is mm Radiocarbon dating edit Main article Radiocarbon dating Radiocarbon dating is a radiometric dating method that uses C to determine the age of carbonaceous materials up to about , years old The technique was developed by Willard Libby and his colleagues in during his tenure as a professor at the University of Chicago Libby estimated that the radioactivity of exchangeable carbon would be about disintegrations per minute dpm per gram of pure carbon, and this is still used as the activity of the modern radiocarbon standard In , Libby was awarded the Nobel Prize in chemistry for this work One of the frequent uses of the technique is to date organic remains from archaeological sites Plants fix atmospheric carbon during photosynthesis, so the level of C in plants and animals when they die approximately equals the level of C in the atmosphere at that time However, it decreases thereafter from radioactive decay, allowing the date of death or fixation to be estimated The initial C level for the calculation can either be estimated, or else directly compared with known year by year data from tree ring data dendrochronology up to , years ago using overlapping data from live and dead trees in a given area , or else from cave deposits speleothems , back to about , years before the present A calculation or more accurately a direct comparison of carbon levels in a sample, with tree ring or cave deposit carbon levels of a known age, then gives the wood or animal sample age since formation Origin edit Natural production in the atmosphere edit Formation of carbon Decay of carbon The equal equation is for living organisms, and the unequal one is for dead organisms, in which the C then decays See Carbon is produced in the upper layers of the troposphere and the stratosphere by thermal neutrons absorbed by nitrogen atoms When cosmic rays enter the atmosphere, they undergo various transformations, including the production of neutrons The resulting neutrons n participate in the following reaction n + N ? C + p The highest rate


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lise-pinson little-oral-annie liza-dwyer liza-harper lizzy-borden logan-labrent lois-ayres lola-cait long-jean-silver loni-bunny loni-sanders loona-luxx lorelei-lee lorelei-rand lorena-sanchez lori-alexia lori-blue lorrie-lovett luci-diamond lucie-doll lucie-theodorova lucy-van-dam lydia-baum lynn-franciss lynn-lemay lynn-ray lynn-stevens lynx-canon lysa-thatcher madelina-ray madison-parker magdalena-lynn maggie-randall mai-lin mandi-wine mandy-bright mandy-malone mandy-may mandy-mistery mandy-starr marcia-minor maren margit-ojetz margitta-hofer margo-stevens margot-mahler mariah-cherry marianne-aubert maria-tortuga marie-anne marie-christine-chireix marie-christine-veroda marie-claude-moreau marie-dominique-cabannes marie-france-morel marie-luise-lusewitz marie-sharp marilyn-chambers marilyne-leroy marilyn-gee marilyn-jess marilyn-martyn marilyn-star marina-hedman marion-webb marita-ekberg marita-kemper marlena marlene-willoughby marry-queen martine-grimaud martine-schultz maryanne-fisher mary-hubay mary-ramunno mary-stuart mascha-mouton maud-kennedy mauvais-denoir maxine-tyler maya-black maya-france megan-leigh megan-martinez megan-reece mei-ling melanie-hotlips melanie-scott melba-cruz melinda-russell melissa-bonsardo melissa-del-prado melissa-golden melissa-martinez melissa-melendez melissa-monet mercedes-dragon mercedes-lynn merle-michaels mesha-lynn mia-beck mia-lina mia-smiles michele-raven michelle-aston michelle-ferrari michelle-greco michelle-maren michelle-maylene michelle-monroe micki-lynn mika-barthel mika-tan mikki-taylor mimi-morgan mindy-rae ming-toy miranda-stevens miss-bunny miss-meadow miss-pomodoro missy missy-graham missy-stone missy-vega misti-jane mistress-candice misty-anderson misty-dawn misty-rain misty-regan mona-lisa mona-page moni monica-baal monica-swinn monika-peta monika-sandmayr monika-unco monique-bruno monique-cardin monique-charell monique-demoan monique-gabrielle monique-la-belle morgan-fairlane morrigan-hel moxxie-maddron mulani-rivera mysti-may nadege-arnaud nadia-styles nadine-bronx nadine-proutnal nadine-roussial nadi-phuket nanci-suiter nancy-hoffman nancy-vee natacha-delyro natalia-wood natalli-diangelo natascha-throat natasha-skyler naudia-nyce nessa-devil nessy-grant nesty nicki-hunter nicky-reed nicole-berg nicole-bernard nicole-black nicole-grey nicole-london nicole-parks nicole-scott nicole-taylor nicolette-fauludi nicole-west nika-blond nika-mamic niki-cole nikita-love nikita-rush nikki-charm nikki-grand nikki-king nikki-knight nikki-randall nikki-rhodes nikki-santana nikki-steele nikki-wilde niko nina-cherry nina-deponca nina-hartley nina-preta oana-efria obaya-roberts olesja-derevko olga-cabaeva olga-conti olga-pechova olga-petrova olivia-alize olivia-del-rio olivia-flores olivia-la-roche olivia-outre ophelia-tozzi orchidea-keresztes orsolya-blonde paige-turner paisley-hunter pamela-bocchi pamela-jennings pamela-mann pamela-stanford pamela-stealt pandora paola-albini pascale-vital pat-manning pat-rhea patricia-dale patricia-diamond patricia-kennedy patricia-rhomberg patrizia-predan patti-cakes patti-petite paula-brasile paula-harlow paula-morton paula-price paula-winters pauline-teutscher penelope-pumpkins penelope-valentin petra-hermanova petra-lamas peyton-lafferty phaedra-grant pia-snow piper-fawn pipi-anderson porsche-lynn porsha-carrera precious-silver priscillia-lenn purple-passion queeny-love rachel-ashley rachel-love rachel-luv rachel-roxxx rachel-ryan rachel-ryder racquel-darrian rane-revere raven reagan-maddux rebecca-bardoux regan-anthony regine-bardot regula-mertens reina-leone reka-gabor renae-cruz renee-foxx renee-lovins renee-morgan renee-perez renee-summers renee-tiffany rhonda-jo-petty rikki-blake riley-ray rio-mariah rita-ricardo roberta-gemma roberta-pedon robin-byrd robin-cannes robin-everett robin-sane rochell-starr rosa-lee-kimball rosemarie roxanne-blaze roxanne-hall roxanne-rollan ruby-richards sabina-k sabre sabrina-chimaera sabrina-dawn sabrina-jade sabrina-johnson sabrina-love-cox sabrina-mastrolorenzi sabrina-rose sabrina-scott sabrina-summers sacha-davril sahara sahara-sands sai-tai-tiger samantha-fox samantha-ryan samantha-sterlyng samantha-strong samueline-de-la-rosa sandra-cardinale sandra-de-marco sandra-kalermen sandra-russo sandy-lee sandy-pinney sandy-reed sandy-samuel sandy-style sandy-summers sara-brandy-canyon sara-faye sarah-bernard sarah-cabrera sarah-hevyn sarah-mills sarah-shine sara-sloane sasha sasha-hollander sasha-ligaya sasha-rose satine-phoenix satin-summer savannah-stern savanna-jane scarlet-scarleau scarlet-windsor seka selena serena serena-south severine-amoux shana-evans shanna-mccullough shannon-kelly shannon-rush shantell-day sharon-da-vale sharon-kane sharon-mitchell shaun-michelle shawna-sexton shawnee-cates shay-hendrix shayne-ryder sheena-horne sheer-delight shelby-star shelby-stevens shelly-berlin shelly-lyons sheri-st-clair sheyla-cats shonna-lynn shyla-foxxx shy-love sierra-sinn sierra-skye sigrun-theil silver-starr silvia-bella silvia-saint silvie-de-lux silvy-taylor simone-west sindee-coxx sindy-lange sindy-shy siobhan-hunter skylar-knight skylar-price skyler-dupree smokie-flame smoking-mary-jane solange-shannon sonya-summers sophia-santi sophie-call sophie-duflot sophie-evans sophie-guers stacey-donovan stacy-lords stacy-moran stacy-nichols stacy-silver stacy-thorn starla-fox starr-wood stefania-bruni stella-virgin stephanie-duvalle stephanie-rage stephanie-renee stevie-taylor summer-knight summer-rose sunny-day sunset-thomas sunshine-seiber susan-hart susanne-brend susan-nero susi-hotkiss suzanne-mcbain suzan-nielsen suzie-bartlett suzie-carina suzi-sparks sweet-nice sweety-pie sybille-rossani sylvia-benedict sylvia-bourdon sylvia-brand sylvia-engelmann syreeta-taylor syren-de-mer syvette szabina-black szilvia-lauren tai-ellis taija-rae taisa-banx talia-james tamara-lee tamara-longley tamara-n-joy tamara-west tami-white tammy tammy-lee tammy-reynolds tania-lorenzo tantala-ray tanya-danielle tanya-fox tanya-foxx tanya-lawson tanya-valis tara-aire tasha-voux tatjana-belousova tatjana-skomorokhova tawnee-lee tawny-pearl tayla-rox taylor-wane teddi-austin teddi-barrett tera-bond tera-heart tera-joy teresa-may teresa-orlowski teri-diver teri-weigel terri-dolan terri-hall tess-ferre tess-newheart thais-vieira tia-cherry tianna tiara tiffany-blake tiffany-clark tiffany-duponte tiffany-rayne tiffany-rousso tiffany-storm tiffany-towers tiffany-tyler tiger-lily tigr timea-vagvoelgyi tina-blair tina-burner tina-evil tina-gabriel tina-loren tina-marie tina-russell tish-ambrose tommi-rose tonisha-mills topsy-curvey tori-secrets tori-sinclair tori-welles tracey-adams traci-lords traci-topps traci-winn tracy-duzit tracy-love tracy-williams tricia-devereaux tricia-yen trinity-loren trisha-rey trista-post trixie-tyler ultramax ursula-gaussmann ursula-moore uschi-karnat valentina valerie-leveau valery-hilton vanessa-chase vanessa-del-rio vanessa-michaels vanessa-ozdanic vanilla-deville velvet-summers veri-knotty veronica-dol veronica-hart veronica-hill veronica-rayne veronica-sage veronika-vanoza via-paxton vicky-lindsay vicky-vicci victoria-evans victoria-gold victoria-knight victoria-luna victoria-paris victoria-slick victoria-zdrok viper virginie-caprice vivian-valentine vivien-martines wendi-white wendy-divine whitney-banks whitney-fears whitney-wonders wonder-tracey wow-nikki xanthia-berstein yasmine-fitzgerald yelena-shieffer yvonne-green zara-whites zsanett-egerhazi zuzie-boobies

of carbon production takes place at altitudes of to km , to , ft and at high geomagnetic latitudes As of , the rate of C production was poorly known – while the reaction can be modelled and the results agree with the global carbon budget that can be used to backtrack, attempts to directly measure the production rate had not agreed with these models very well Production rates vary because of changes to the cosmic ray flux incident, such as supernovae, and due to variations in the Earth's magnetic field The latter can create significant variations in C production rates, although the changes of the carbon cycle can make these effects difficult to tease out The natural atmospheric yield of C has been estimated to be about atoms C per meter square of the surface of the earth per second, resulting in the global production rate of about PBq a Another estimate of the average production rate gives a value of atoms m- s- More recent work, however, suggests that the use of outdated cosmic ray spectra has led to an overestimation of C yield and revised the estimate down to between to atoms C per meter square Occasional spikes are possible for example, there is evidence for an unusual fold increase of the production rate in AD – Other carbon sources edit Carbon can also be produced by other neutron reactions, including in particular C n,gamma C and O n,alpha C with thermal neutrons, and N n,d C and O n, He C with fast neutrons The most notable routes for C production by thermal neutron irradiation of targets e g , in a nuclear reactor are summarized in the table Carbon may also be radiogenic cluster decay of Ra, Ra, Ra However, this origin is extremely rare C production routes Parent isotope Natural abundance, % Cross section for thermal neutron capture, b Reaction N N n,p C C C n,? C O O n,a C Formation during nuclear tests edit Atmospheric C, New Zealand and Austria The New Zealand curve is representative for the Southern Hemisphere, the Austrian curve is representative for the Northern Hemisphere Atmospheric nuclear weapon tests almost doubled the concentration of C in the Northern Hemisphere The above ground nuclear tests that occurred in several countries between and see nuclear test list dramatically increased the amount of carbon in the atmosphere and subsequently in the biosphere after the tests ended, the atmospheric concentration of the isotope began to decrease One side effect of the change in atmospheric carbon is that this has enabled some options e g bomb pulse dating for determining the birth year of an individual, in particular, the amount of carbon in tooth enamel, or the carbon concentration in the lens of the eye Occurrence edit Dispersion in the environment edit After production in the upper atmosphere, the carbon atoms react rapidly to form mostly about % CO carbon monoxide , which subsequently oxidizes at a slower rate to form CO , radioactive carbon dioxide The gas mixes rapidly and becomes evenly distributed throughout the atmosphere the mixing timescale in the order of weeks Carbon dioxide also dissolves in water and thus permeates the oceans, but at a slower rate The atmospheric half life for removal of CO has been estimated to be roughly to years in the northern hemisphere The transfer between the ocean shallow layer and the large reservoir of bicarbonates in the ocean depths occurs at a limited rate In the activity of C was Bq per kg carbon of fresh terrestrial biomatter, close to the values before atmospheric nuclear testing Bq kg C Total inventory edit The inventory of carbon in Earth's biosphere is about megacuries EBq , of which most is in the oceans The following inventory of carbon has been given Global inventory ~ PBq about t Ammonia or azane is a compound of nitrogen and hydrogen with the formula NH It is a colourless gas with a characteristic pungent smell Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers Ammonia, either directly or indirectly, is also a building block for the synthesis of many pharmaceuticals and is used in many commercial cleaning products Although common in nature and in wide use, ammonia is both caustic and hazardous in its concentrated form The global industrial production of ammonia for was anticipated to be , , tonnes , , long tons , , short tons , a % increase over the estimated global output of , , tonnes , , long tons , , short tons NH boils at - °C - °F at a pressure of one atmosphere, so the liquid must be stored under pressure or at low temperature Household ammonia or ammonium hydroxide is a solution of NH in water The concentration of such solutions is measured in units of the Baumé scale density , with degrees baumé about % by weight ammonia at °C or °F being the typical high concentration commercial product Contents hide Natural occurrence Properties Structure Amphotericity Self dissociation Combustion Formation of other compounds Ammonia as a ligand Detection and determination Ammonia in solution Gaseous ammonia Ammoniacal nitrogen NH N History Uses Fertilizer Precursor to nitrogenous compounds Cleaner Fermentation Antimicrobial agent for food products Minor and emerging uses Refrigeration – R For remediation of gaseous emissions As a fuel As a stimulant Textile Lifting gas Woodworking Safety precautions Toxicity Aquaculture Storage information Household use Laboratory use of ammonia solutions Laboratory use of anhydrous ammonia gas or liquid Synthesis and production Liquid ammonia as a solvent Solubility of salts Solutions of metals Redox properties of liquid ammonia Ammonia's role in biological systems and human disease Biosynthesis In physiology Excretion In astronomy Interstellar space Interstellar formation mechanisms Interstellar destruction mechanisms Single antenna detections Interferometric studies Infrared detections Observations of nearby dark clouds UC HII regions Extragalactic detection See also Notes References Further reading External links Natural occurrence edit Ammonia is found in trace quantities in the atmosphere, being produced from the putrefaction decay process of nitrogenous animal and vegetable matter Ammonia and ammonium salts are also found in small quantities in rainwater, whereas ammonium chloride sal ammoniac , and ammonium sulfate are found in volcanic districts crystals of ammonium bicarbonate have been found in Patagonian guano The kidneys secrete ammonia to neutralize excess acid Ammonium salts are found distributed through fertile soil and in seawater Ammonia is also found throughout the Solar System on Pluto, Mars, Jupiter, Saturn, Uranus, and Neptune Substances containing ammonia, or those that are similar to it, are called ammoniacal Properties edit Ammonia is a colourless gas with a characteristic pungent smell It is lighter than air, its density being times that of air It is easily liquefied due to the strong hydrogen bonding between molecules the liquid boils at - °C - °F , and freezes at - °C - °F to white crystals Ammonia may be conveniently deodorized by reacting it with either sodium bicarbonate or acetic acid Both of these reactions form an odourless ammonium salt Solid The crystal symmetry is cubic, Pearson symbol cP , space group P No , lattice constant nm Liquid Liquid ammonia possesses strong ionising powers reflecting its high e of Liquid ammonia has a very high standard enthalpy change of vaporization kJ mol, cf water kJ mol, methane kJ mol, phosphine kJ mol and can therefore be used in laboratories in uninsulated vessels without additional refrigeration See liquid ammonia as a solvent Solvent properties Ammonia is miscible with water In an aqueous solution, it can be expelled by boiling The aqueous solution of ammonia is basic The maximum concentration of ammonia in water a saturated solution has a density of g cm and is often known as ' ammonia' Ammonia does not burn readily or sustain combustion, except under narrow fuel to air mixtures of – % air Combustion When mixed with oxygen, it burns with a pale yellowish green flame At high temperature and in the presence of a suitable catalyst, ammonia is decomposed into its constituent elements Ignition occurs when chlorine is passed into ammonia, forming nitrogen and hydrogen chloride if chlorine is present in excess, then the highly explosive nitrogen trichloride NCl is also formed Structure edit The ammonia molecule has a trigonal pyramidal shape as predicted by the valence shell electron pair repulsion theory VSEPR theory with an experimentally determined bond angle of ° The central nitrogen atom has five outer electrons with an additional electron from each hydrogen atom This gives a total of eight electrons, or four electron pairs that are arranged tetrahedrally Three of these electron pairs are used as bond pairs, which leaves one lone pair of electrons The lone pair of electrons repel more strongly than bond pairs, therefore the bond angle is not °, as expected for a regular tetrahedral arrangement, but ° The nitrogen atom in the molecule has a lone electron pair, which makes ammonia a base, a proton acceptor This shape gives the molecule a dipole moment and makes it polar The molecule's polarity and, especially, its ability to form hydrogen bonds, makes ammonia highly miscible with water Ammonia is moderately basic, a M aqueous solution has a pH of and if a strong acid is added to such a solution until the solution is neutral pH , % of the ammonia molecules are protonated Temperature and salinity also affect the proportion of NH + The latter has the shape of a regular tetrahedron and is isoelectronic with methane The ammonia molecule readily undergoes nitrogen inversion at room temperature a useful analogy is an umbrella turning itself inside out in a strong wind The energy barrier to this inversion is kJ mol, and the resonance frequency is GHz, corresponding to microwave radiation of a wavelength of cm The absorption at this frequency was the first microwave spectrum to be observed Amphotericity edit One of the most characteristic properties of ammonia is its basicity Ammonia is considered to be a weak base It combines with acids to form salts thus with hydrochloric acid it forms ammonium chloride sal ammoniac with nitric acid, ammonium nitrate, etc Perfectly dry ammonia will not combine with perfectly dry hydrogen chloride moisture is necessary to bring about the reaction As a demonstration experiment, opened bottles of concentrated ammonia and hydrochloric acid produce clouds of ammonium chloride, which seem to appear out of nothing as the salt forms where the two diffusing clouds of molecules meet, somewhere between the two bottles NH + HCl ? NH Cl The salts produced by the action of ammonia on acids are known as the ammonium salts and all contain the ammonium ion NH + Although ammonia is well known as a weak base, it can also act as an extremely weak acid It is a protic substance and is capable of formation of amides which contain the NH - ion For example, lithium dissolves in liquid ammonia to give a solution of lithium amide Li + NH ? LiNH + H Self dissociation edit Like water, ammonia undergoes molecular autoionisation to form its acid and base conjugates NH aq is in equilibrium with NH+ aq + NH- aq At standard pressure and temperature, K NH+ NH- - Combustion edit The combustion of ammonia to nitrogen and water is exothermic NH + O ? N + H O g ?H°r - kJ mol The standard enthalpy change of combustion, ?H°c, expressed per mole of ammonia and with condensation of the water formed, is - kJ mol Dinitrogen is the thermodynamic product of combustion all nitrogen oxides are unstable with respect to N and O , which is the principle behind the catalytic converter Nitrogen oxides can be formed as kinetic products in the presence of appropriate catalysts, a reaction of great industrial importance in the production of nitric acid NH + O ? NO + H O A subsequent reaction leads to NO NO + O ? NO The combustion of ammonia in air is very difficult in the absence of a catalyst such as platinum gauze , because the temperature of the flame is usually lower than the ignition temperature of the ammonia–air mixture The flammable range of ammonia in air is – % Formation of other compounds edit In organic chemistry, ammonia can act as a nucleophile in substitution reactions Amines can be formed by the reaction of ammonia with alkyl halides, although the resulting NH group is also nucleophilic and secondary and tertiary amines are often formed as byproducts An excess of ammonia helps minimise multiple substitution, and neutralises the hydrogen halide formed Methylamine is prepared commercially by the reaction of ammonia with chloromethane, and the reaction of ammonia with bromopropanoic acid has been used to prepare racemic alanine in % yield Ethanolamine is prepared by a ring opening reaction with ethylene oxide the reaction is sometimes allowed to go further to produce diethanolamine and triethanolamine Amides can be prepared by the reaction of ammonia with carboxylic acid derivatives Acyl chlorides are the most reactive, but the ammonia must be present in at least a twofold excess to neutralise the hydrogen chloride formed Esters and anhydrides also react with ammonia to form amides Ammonium salts of carboxylic acids can be dehydrated to amides so long as there are no thermally sensitive groups present temperatures of – °C are required The hydrogen in ammonia is capable of replacement by metals, thus magnesium burns in the gas with the formation of magnesium nitride Mg N , and when the gas is passed over heated sodium or potassium, sodamide, NaNH , and potassamide, KNH , are formed Where necessary in substitutive nomenclature, IUPAC recommendations prefer the name azane to ammonia hence chloramine would be named chloroazane in substitutive nomenclature, not chloroammonia Pentavalent ammonia is known as ? amine, or more commonly, ammonium hydride This crystalline solid is only stable under high pressure, and decomposes back into trivalent ammonia and hydrogen gas at normal conditions This substance was once investigated as a possible solid rocket fuel in Ammonia as a ligand edit Main article Metal ammine complex Ball and stick model of the tetraamminediaquacopper II cation, Cu NH H O + Ammonia can act as a ligand in transition metal complexes It is a pure s donor, in the middle of the spectrochemical series, and shows intermediate hard soft behaviour For historical reasons, ammonia is named ammine in the nomenclature of coordination compounds Some notable ammine complexes include tetraamminediaquacopper II Cu NH H O + , a dark blue complex formed by adding ammonia to a solution of copper II salts Tetraamminediaquacopper II hydroxide is known as Schweizer's reagent, and has the remarkable ability to dissolve cellulose Diamminesilver I Ag NH + is the active species in Tollens' reagent Formation of this complex can also help to distinguish between precipitates of the different silver halides silver chloride AgCl is soluble in dilute M ammonia solution, silver bromide AgBr is only soluble in concentrated ammonia solution, whereas silver iodide AgI is insoluble in aqueous ammonia Ammine complexes of chromium III were known in the late th century, and formed the basis of Alfred Werner's revolutionary theory on the structure of coordination compounds Werner noted only two isomers fac and mer of the complex CrCl NH could be formed, and concluded the ligands must be arranged around the metal ion at the vertices of an octahedron This proposal has since been confirmed by X ray crystallography An ammine ligand bound to a metal ion is markedly more acidic than a free ammonia molecule, although deprotonation in aqueous solution is still rare One example is the Calomel reaction, where the resulting amidomercury II compound is highly insoluble Hg Cl + NH ? Hg + HgCl NH + NH + + Cl- Detection and determination edit This section is about detection in the laboratory For detection in astronomy, see chapter In astronomy Ammonia in solution edit Ammonia and ammonium salts can be readily detected, in very minute traces, by the addition of Nessler's solution, which gives a distinct yellow colouration in the presence of the least trace of ammonia or ammonium salts The amount of ammonia in ammonium salts can be estimated quantitatively by distillation of the salts with sodium or potassium hydroxide, the ammonia evolved being absorbed in a known volume of standard sulfuric acid and the excess of acid then determined volumetrically or the ammonia may be absorbed in hydrochloric acid and the ammonium chloride so formed precipitated as ammonium hexachloroplatinate, NH PtCl Gaseous ammonia edit Sulfur sticks are burnt to detect small leaks in industrial ammonia refrigeration systems Larger quantities can be detected by warming the salts with a caustic alkali or with quicklime, when the characteristic smell of ammonia will be at once apparent Ammonia is an irritant and irritation increases with concentration the Permissible Exposure Limit is ppm, and lethal above ppm Higher concentrations are hardly detected by conventional detectors, the type of detector is chosen according to the sensitivity required e g semiconductor, catalytic, electrochemical Holographic sensors have been proposed for detecting concentrations up to % in volume Ammoniacal nitrogen NH N edit Ammoniacal nitrogen NH N is a measure commonly used for testing the quantity of ammonium ions, derived naturally from ammonia, and returned to ammonia via organic processes, in water or waste liquids It is a measure used mainly for quantifying values in waste treatment and water purification systems, as well as a measure of the health of natural and man made water reserves It is measured in units of mg L milligram per litre History edit This high pressure reactor was built in by BASF in Ludwigshafen and was re erected on the premises of the University of Karlsruhe in Germany The Romans gave the name sal ammoniacus salt of Amun to the ammonium chloride deposits that they collected near the Temple of Amun Greek ?µµ?? Ammon in ancient Libya Salts of ammonia have been known from very early times thus the term Hammoniacus sal appears in the writings of Pliny, although it is not known whether the term is identical with the more modern sal ammoniac ammonium chloride In the form of sal ammoniac ?????, nushadir ammonia was important to the Muslim alchemists as early as the th century, first mentioned by the Persian chemist Jabir ibn Hayyan, and to the European alchemists since the th century, being mentioned by Albertus Magnus It was also used by dyers in the Middle Ages in the form of fermented urine to alter the colour of vegetable dyes In the th century, Basilius Valentinus showed that ammonia could be obtained by the action of alkalis on sal ammoniac At a later period, when sal ammoniac was obtained by distilling the hooves and horns of oxen and neutralizing the resulting carbonate with hydrochloric acid, the name spirit of hartshorn was applied to ammonia Gaseous ammonia was first isolated by Joseph Priestley in and was termed by him alkaline air Eleven years later in , Claude Louis Berthollet ascertained its composition The Haber–Bosch process to produce ammonia from the nitrogen in the air was developed by Fritz Haber and Carl Bosch in and patented in It was first used on an industrial scale in Germany during World War I, following the allied blockade that cut off the supply of nitrates from Chile The ammonia was used to produce explosives to sustain war efforts Prior to the availability of natural gas, hydrogen as a precursor to ammonia production was produced via the electrolysis of water or using the chloralkali process Uses edit Fertilizer edit Approximately % as of of ammonia is used as fertilizers either as its salts, solutions or anhydrously When applied to soil, it helps provide increased yields of crops such as maize and wheat citation needed % of agricultural nitrogen applied in the USA is in the form of anhydrous ammonia and worldwide million tonnes are applied each year Precursor to nitrogenous compounds edit Ammonia is directly or indirectly the precursor to most nitrogen containing compounds Virtually all synthetic nitrogen compounds are derived from ammonia An important derivative is nitric acid This key material is generated via the Ostwald process by oxidation of ammonia with air over a platinum catalyst at – °C , – , °F , ~ atm Nitric oxide is an intermediate in this conversion NH + O ? HNO + H O Nitric acid is used for the production of fertilizers, explosives, and many organonitrogen compounds Ammonia is also used to make the following compounds Hydrazine, in the Olin Raschig process and the peroxide process Hydrogen cyanide, in the BMA process and the Andrussow process Hydroxylamine and ammonium carbonate, in the Raschig process Phenol, in the Raschig–Hooker process Urea, in the Bosch–Meiser urea process and in Wöhler synthesis Amino acids, using Strecker amino acid synthesis Acrylonitrile, in the Sohio process Ammonia can also be used to make compounds in reactions which are not specifically named Examples of such compounds include ammonium perchlorate, ammonium nitrate, formamide, dinitrogen tetroxide, alprazolam, ethanolamine, ethyl carbamate, hexamethylenetetramine, and ammonium bicarbonate Cleaner edit Household ammonia is a solution of NH in water i e , ammonium hydroxide used as a general purpose cleaner for many surfaces Because ammonia results in a relatively streak free shine, one of its most common uses is to clean glass, porcelain and stainless steel It is also frequently used for cleaning ovens and soaking items to loosen baked on grime Household ammonia ranges in concentration by weight from to % ammonia Fermentation edit Solutions of ammonia ranging from % to % are used in the fermentation industry as a source of nitrogen for microorganisms and to adjust pH during fermentation Antimicrobial agent for food products edit As early as in , it was known that ammonia was strongly antiseptic it requires grams per litre to preserve beef tea In one study, anhydrous ammonia destroyed % of zoonotic bacteria in types of animal feed, but not silage non primary source needed Anhydrous ammonia is currently used commercially to reduce or eliminate microbial contamination of beef Pink slime or lean finely textured beef in the beef industry is made from fatty beef trimmings about – % fat by removing the fat using heat and centrifugation, then treating it with ammonia to kill E coli The process was deemed effective and safe by the US Department of Agriculture based on a study funded by a producer of pink slime that found that the treatment reduces E coli to undetectable levels There have been safety concerns about the process as well as consumer complaints about the taste and smell of beef treated at optimal levels of ammonia The level of ammonia in any final product has not come close to toxic levels to humans Minor and emerging uses edit Refrigeration – R edit Because of ammonia's vaporization properties, it is a useful refrigerant It was commonly used prior to the popularisation of chlorofluorocarbons Freons Anhydrous ammonia is widely used in industrial refrigeration applications and hockey rinks because of its high energy efficiency and low cost It suffers from the disadvantage of toxicity, which restricts its domestic and small scale use Along with its use in modern vapor compression refrigeration it was used in a mixture along with hydrogen and water in absorption refrigerators The Kalina cycle, which is of growing importance to geothermal power plants, depends on the wide boiling range of the ammonia–water mixture For remediation of gaseous emissions edit Ammonia is used to scrub SO from the burning of fossil fuels, and the resulting product is converted to ammonium sulfate for use as fertilizer Ammonia neutralizes the nitrogen oxides NOx pollutants emitted by diesel engines This technology, called SCR selective catalytic reduction , relies on a vanadia based catalyst Ammonia may be used to mitigate gaseous spills of phosgene As a fuel edit Gnome searchtool svg This section's factual accuracy is disputed October This article contains wording that promotes the subject in a subjective manner without imparting real information Please remove or replace such wording and instead of making proclamations about a subject's importance, use facts and attribution to demonstrate that importance October Ammoniacal Gas Engine Streetcar in New Orleans drawn by Alfred Waud in The X aircraft used ammonia as one component fuel of its rocket engine Ammonia was used during World War II to power buses in Belgium, and in engine and solar energy applications prior to Liquid ammonia also fuelled the Reaction Motors XLR rocket engine that powered the X hypersonic research aircraft Although not as powerful as other fuels, it left no soot in the reusable rocket engine and its density approximately matches the density of the oxidizer, liquid oxygen, which simplified the aircraft's design Ammonia has been proposed as a practical alternative to fossil fuel for internal combustion engines The calorific value of ammonia is MJ kg BTU lb , which is about half that of diesel In a normal engine, in which the water vapour is not condensed, the calorific value of ammonia will be about % less than this figure Ammonia cannot be easily or efficiently used in existing Otto cycle engines because of its very low octane rating, although with only minor modifications to carburettors injectors and a drastic reduction in compression ratio, which would require new pistons, a gasoline engine could be made to work exclusively with ammonia, at a low fraction of its power output before conversion and much higher fuel consumption citation needed An automobile fuel tank could store ammonia as a liquid as long as the tank was pressurized appropriately, depending on the temperature Ammonia's thermodynamic properties are such that at °C, the tank pressure would only have to be psi, about the same as a car tire At °C °F the pressure in the tank would need to be psi to keep the ammonia liquid If tank pressure was released, the liquid ammonia would turn gaseous and raise the pressure again to that level Common pneumatic tool air compressors operate at this pressure, so fuel tank pressure is not a barrier to adoption of automobile fuel usage There are other barriers to widespread automobile usage In terms of raw ammonia supplies, plants would have to be built to increase production levels, requiring significant capital and energy sources Although it is the second most produced chemical, the scale of ammonia production is a small fraction of world petroleum usage It could be manufactured from renewable energy sources, as well as coal or nuclear power The MW Rjukan dam in Telemark, Norway produced ammonia via electrolysis of water for many years from producing fertilizer for much of Europe If produced from coal, the CO could be sequestered, but carbon capture and storage from coal power plants is not yet beyond prototype stages In , a Canadian company converted a Chevrolet Impala to operate using ammonia as fuel In , a University of Michigan pickup powered by ammonia drove from Detroit to San Francisco as part of a demonstration, requiring only one fill up in Wyoming Ammonia engines or ammonia motors, using ammonia as a working fluid, have been proposed and occasionally used The principle is similar to that used in a fireless locomotive, but with ammonia as the working fluid, instead of steam or compressed air Ammonia engines were used experimentally in the th century by Goldsworthy Gurney in the UK and in streetcars in New Orleans As a stimulant edit Anti meth sign on tank of anhydrous ammonia, Otley, Iowa Anhydrous ammonia is a common farm fertilizer that is also a critical ingredient in making methamphetamine In , Iowa state used grant money to give out thousands of locks to prevent criminals from getting into the tanks Ammonia, as the vapor released by smelling salts, has found significant use as a respiratory stimulant Ammonia is commonly used in the illegal manufacture of methamphetamine through a Birch reduction The Birch method of making methamphetamine is dangerous because the alkali metal and liquid ammonia are both extremely reactive, and the temperature of liquid ammonia makes it susceptible to explosive boiling when reactants are added citation needed Textile edit Liquid ammonia is used for treatment of cotton materials, giving properties like mercerisation, using alkalis In particular, it is used for prewashing of wool Lifting gas edit At standard temperature and pressure, ammonia is less dense than atmosphere, and has approximately % of the lifting power of hydrogen or helium Ammonia has sometimes been used to fill weather balloons as a lifting gas Because of its relatively high boiling point compared to helium and hydrogen , ammonia could potentially be refrigerated and liquefied aboard an airship to reduce lift and add ballast and returned to a gas to add lift and reduce ballast Woodworking edit See also Ammonia fuming Ammonia has been used to darken quartersawn white oak in Arts & Crafts and Mission style furniture Ammonia fumes react with the natural tannins in the wood and cause it to change colours Safety precautions edit The world's longest ammonia pipeline, running from the TogliattiAzot plant in Russia to Odessa in Ukraine The U S Occupational Safety and Health Administration OSHA has set a minute exposure limit for gaseous ammonia of ppm by volume in the environmental air and an hour exposure limit of ppm by volume NIOSH recently reduced the IDLH from to based on recent more conservative interpretations of original research in IDLH Immediately Dangerous to Life and Health is the level to which a healthy worker can be exposed for minutes without suffering irreversible health effects Other organizations have varying exposure levels U S Navy Standards U S Bureau of Ships maximum allowable concentrations MACs continuous exposure days ppm hour ppm Ammonia vapour has a sharp, irritating, pungent odour that acts as a warning of potentially dangerous exposure The average odour threshold is ppm, well below any danger or damage Exposure to very high concentrations of gaseous ammonia can result in lung damage and death Although ammonia is regulated in the United States as a non flammable gas, it still meets the definition of a material that is toxic by inhalation and requires a hazardous safety permit when transported in quantities greater than , L , gallons Toxicity edit The toxicity of ammonia solutions does not usually cause problems for humans and other mammals, as a specific mechanism exists to prevent its build up in the bloodstream Ammonia is converted to carbamoyl phosphate by the enzyme carbamoyl phosphate synthetase, and then enters the urea cycle to be either incorporated into amino acids or excreted in the urine citation needed Fish and amphibians lack this mechanism, as they can usually eliminate ammonia from their bodies by direct excretion Ammonia even at dilute concentrations is highly toxic to aquatic animals, and for this reason it is classified as dangerous for the environment Aquaculture edit Ammonia toxicity is believed to be a cause of otherwise unexplained losses in fish hatcheries Excess ammonia may accumulate and cause alteration of metabolism or increases in the body pH of the exposed organism Tolerance varies among fish species At lower concentrations, around mg L, un ionised ammonia is harmful to fish species and can result in poor growth and feed conversion rates, reduced fecundity and fertility and increase stress and susceptibility to bacterial infections and diseases Exposed to excess ammonia, fish may suffer loss of equilibrium, hyper excitability, increased respiratory activity and oxygen uptake and increased heart rate At concentrations exceeding mg L, ammonia causes gill and tissue damage, extreme lethargy, convulsions, coma, and death Experiments have shown that the lethal concentration for a variety of fish species ranges from to mg l During winter, when reduced feeds are administered to aquaculture stock, ammonia levels can be higher Lower ambient temperatures reduce the rate of algal photosynthesis so less ammonia is removed by any algae present Within an aquaculture environment, especially at large scale, there is no fast acting remedy to elevated ammonia levels Prevention rather than correction is recommended to reduce harm to farmed fish and in open water systems, the surrounding environment Storage information edit Similar to propane, anhydrous ammonia boils below room temperature when at atmospheric pressure A storage vessel capable of psi MPa is suitable to contain the liquid Ammonium compounds should never be allowed to come in contact with bases unless in an intended and contained reaction , as dangerous quantities of ammonia gas could be released Household use edit Solutions of ammonia – % by weight are used as household cleaners, particularly for glass These solutions are irritating to the eyes and mucous membranes respiratory and digestive tracts , and to a lesser extent the skin Caution should be used that the chemical is never mixed into any liquid containing bleach, as a poisonous gas may result Mixing with chlorine containing products or strong oxidants, such as household bleach, can lead to hazardous compounds such as chloramines Laboratory use of ammonia solutions edit Hydrochloric acid sample releasing HCl fumes, which are reacting with ammonia fumes to produce a white smoke of ammonium chloride The hazards of ammonia solutions depend on the concentration dilute ammonia solutions are usually – % by weight < mol L concentrated solutions are usually prepared at > % by weight A % by weight solution has a density of g cm , and a solution that has a lower density will be more concentrated The European Union classification of ammonia solutions is given in the table Concentration by weight w w Molarity Concentration mass volume w v Classification R Phrases – % – mol L – g L Irritant Xi R – % – mol L – g L Corrosive C R > % > mol L > g L Corrosive C Dangerous for the environment N R , R S Phrases S , S , S , S , S The ammonia vapour from concentrated ammonia solutions is severely irritating to the eyes and the respiratory tract, and these solutions should only be handled in a fume hood Saturated solutions can develop a significant pressure inside a closed bottle in warm weather, and the bottle should be opened with care this is not usually a problem for % solutions Ammonia solutions should not be mixed with halogens, as toxic and or explosive products are formed Prolonged contact of ammonia solutions with silver, mercury or iodide salts can also lead to explosive products such mixtures are often formed in qualitative inorganic analysis, and should be lightly acidified but not concentrated < % w v before disposal once the test is completed Laboratory use of anhydrous ammonia gas or liquid edit Anhydrous ammonia is classified as toxic T and dangerous for the environment N The gas is flammable autoignition temperature °C and can form explosive mixtures with air – % The permissible exposure limit PEL in the United States is ppm mg m , while the IDLH concentration is estimated at ppm Repeated exposure to ammonia lowers the sensitivity to the smell of the gas normally the odour is detectable at concentrations of less than ppm, but desensitised individuals may not detect it even at concentrations of ppm Anhydrous ammonia corrodes copper and zinc containing alloys, and so brass fittings should not be used for handling the gas Liquid ammonia can also attack rubber and certain plastics Ammonia reacts violently with the halogens Nitrogen triiodide, a primary high explosive, is formed when ammonia comes in contact with iodine Ammonia causes the explosive polymerisation of ethylene oxide It also forms explosive fulminating compounds with compounds of gold, silver, mercury, germanium or tellurium, and with stibine Violent reactions have also been reported with acetaldehyde, hypochlorite solutions, potassium ferricyanide and peroxides Synthesis and production edit See also Haber process This section is about industrial synthesis For synthesis in certain organisms, see section §?Biosynthesis below Production trend of ammonia between and Because of its many uses, ammonia is one of the most highly produced inorganic chemicals Dozens of chemical plants worldwide produce ammonia Consuming more than % of all man made power, ammonia production is a significant component of the world energy budget Market research reports total ammonia production in is million tonnes and is predicted to increase by about million tonnes by China produced % of the worldwide production increasingly from coal as part of urea synthesis followed by India with %, Russia with %, and the United States with % About % or more of the ammonia produced is used for fertilizing agricultural crops Before the start of World War I, most ammonia was obtained by the dry distillation of nitrogenous vegetable and animal waste products, including camel dung, where it was distilled by the reduction of nitrous acid and nitrites with hydrogen in addition, it was produced by the distillation of coal, and also by the decomposition of ammonium salts by alkaline hydroxides such as quicklime, the salt most generally used being the chloride sal ammoniac thus NH Cl + CaO ? CaCl + Ca OH + NH Hydrogen for ammonia synthesis could also be produced economically by using the water gas reaction followed by the water gas shift reaction, produced by passing steam through red hot coke, to give a mixture of hydrogen and carbon dioxide gases, followed by removal of the carbon dioxide washing the gas mixture with water under pressure standard atmospheres , kPa or by using other sources like coal or coke gasification Modern ammonia producing plants depend on industrial hydrogen production to react with atmospheric nitrogen using a magnetite catalyst or over a promoted Fe catalyst under high pressure standard atmospheres , kPa and temperature °C to form anhydrous liquid ammonia This step is known as the ammonia synthesis loop also referred to as the Haber–Bosch process H + N ? NH Hydrogen required for ammonia synthesis could also be produced economically using other sources like coal or coke gasification or less economically from the electrolysis of water into oxygen + hydrogen and other alternatives that are presently impractical for large scale At one time, most of Europe's ammonia was produced from the Hydro plant at Vemork, via the electrolysis route Various renewable energy electricity sources are also potentially applicable As a sustainable alternative to the relatively inefficient electrolysis, hydrogen can be generated from organic wastes such as biomass or food industry waste , using catalytic reforming This releases hydrogen from carbonaceous substances at only % of energy used by electrolysis and may lead to hydrogen being produced from municipal wastes at below zero cost allowing for the tipping fees and efficient catalytic reforming, such as cold plasma Catalytic thermal reforming is possible in small, distributed even mobile plants, to take advantage of low value, stranded biomass biowaste or natural gas deposits Conversion of such wastes into ammonia solves the problem of hydrogen storage, as hydrogen can be released economically from ammonia on demand, without the need for high pressure or cryogenic storage It is also easier to store ammonia on board vehicles than to store hydrogen, as ammonia is less flammable than petrol or LPG Liquid ammonia as a solvent edit See also Inorganic nonaqueous solvent Liquid ammonia is the best known and most widely studied nonaqueous ionising solvent Its most conspicuous property is its ability to dissolve alkali metals to form highly coloured, electrically conductive solutions containing solvated electrons Apart from these remarkable solutions, much of the chemistry in liquid ammonia can be classified by analogy with related reactions in aqueous solutions Comparison of the physical properties of NH with those of water shows NH has the lower melting point, boiling point, density, viscosity, dielectric constant and electrical conductivity this is due at least in part to the weaker hydrogen bonding in NH and because such bonding cannot form cross linked networks, since each NH molecule has only one lone pair of electrons compared with two for each H O molecule The ionic self dissociation constant of liquid NH at - °C is about - mol •l- Solubility of salts edit Solubility g of salt per g liquid NH Ammonium acetate Ammonium nitrate Lithium nitrate Sodium nitrate Potassium nitrate Sodium fluoride Sodium chloride Sodium bromide Sodium iodide Sodium thiocyanate Liquid ammonia is an ionising solvent, although less so than water, and dissolves a range of ionic compounds, including many nitrates, nitrites, cyanides and thiocyanates Most ammonium salts are soluble and act as acids in liquid ammonia solutions The solubility of halide salts increases from fluoride to iodide A saturated solution of ammonium nitrate contains mol solute per mole of ammonia and has a vapour pressure of less than bar even at °C °F Solutions of metals edit See also Solvated electron Liquid ammonia will dissolve the alkali metals and other electropositive metals such as magnesium, calcium, strontium, barium, europium and ytterbium At low concentrations < mol l , deep blue solutions are formed these contain metal cations and solvated electrons, free electrons that are surrounded by a cage of ammonia molecules These solutions are very useful as strong reducing agents At higher concentrations, the solutions are metallic in appearance and in electrical conductivity At low temperatures, the two types of solution can coexist as immiscible phases Redox properties of liquid ammonia edit See also Redox E° V, ammonia E° V, water Li+ + e- ? Li - - K+ + e- ? K - - Na+ + e- ? Na - - Zn + + e- ? Zn - - NH + + e- ? ½ H + NH — Cu + + e- ? Cu + + Ag+ + e- ? Ag + + The range of thermodynamic stability of liquid ammonia solutions is very narrow, as the potential for oxidation to dinitrogen, E° N + NH + + e- ? NH , is only + V In practice, both oxidation to dinitrogen and reduction to dihydrogen are slow This is particularly true of reducing solutions the solutions of the alkali metals mentioned above are

stable for several days, slowly decomposing to the metal amide and dihydrogen Most studies involving liquid ammonia solutions are done in reducing conditions although oxidation of liquid ammonia is usually slow, there is still a risk of explosion, particularly if transition metal ions are present as possible catalysts Ammonia's role in biological systems and human disease edit Main symptoms of hyperammonemia ammonia reaching toxic concentrations Ammonia is both a metabolic waste and a metabolic input throughout the biosphere It is an important source of nitrogen for living systems Although atmospheric nitrogen abounds more than % , few living creatures are capable of using this atmospheric nitrogen in its diatomic form, N gas Therefore, nitrogen fixation is required for the synthesis of amino acids, which are the building blocks of protein Some plants rely on ammonia and other nitrogenous wastes incorporated into the soil by decaying matter Others, such as nitrogen fixing legumes, benefit from symbiotic relationships with rhizobia that create ammonia from atmospheric nitrogen Biosynthesis edit In certain organisms, ammonia is produced from atmospheric nitrogen by enzymes called nitrogenases The overall process is called nitrogen fixation Although it is unlikely that biomimetic methods that are competitive with the Haber process will be developed, citation needed intense effort has been directed toward understanding the mechanism of biological nitrogen fixation The scientific interest in this problem is motivated by the unusual structure of the active site of the enzyme, which consists of an Fe MoS ensemble Ammonia is also a metabolic product of amino acid deamination catalyzed by enzymes such as glutamate dehydrogenase Ammonia excretion is common in aquatic animals In humans, it is quickly converted to urea, which is much less toxic, particularly less basic This urea is a major component of the dry weight of urine Most reptiles, birds, insects, and snails excrete uric acid solely as nitrogenous waste In physiology edit Ammonia also plays a role in both normal and abnormal animal physiology It is biosynthesised through normal amino acid metabolism and is toxic in high concentrations The liver converts ammonia to urea through a series of reactions known as the urea cycle Liver dysfunction, such as that seen in cirrhosis, may lead to elevated amounts of ammonia in the blood hyperammonemia Likewise, defects in the enzymes responsible for the urea cycle, such as ornithine transcarbamylase, lead to hyperammonemia Hyperammonemia contributes to the confusion and coma of hepatic encephalopathy, as well as the neurologic disease common in people with urea cycle defects and organic acidurias Ammonia is important for normal animal acid base balance After formation of ammonium from glutamine, a ketoglutarate may be degraded to produce two molecules of bicarbonate, which are then available as buffers for dietary acids Ammonium is excreted in the urine, resulting in net acid loss Ammonia may itself diffuse across the renal tubules, combine with a hydrogen ion, and thus allow for further acid excretion Excretion edit Main article Excretion Ammonium ions are a toxic waste product of metabolism in animals In fish and aquatic invertebrates, it is excreted directly into the water In mammals, sharks, and amphibians, it is converted in the urea cycle to urea, because it is less toxic and can be stored more efficiently In birds, reptiles, and terrestrial snails, metabolic ammonium is converted into uric acid, which is solid, and can therefore be excreted with minimal water loss Reference ranges for blood tests, comparing blood content of ammonia shown in yellow near middle with other constituents In astronomy edit Ammonia occurs in the atmospheres of the outer gas planets such as Jupiter % ammonia and Saturn % ammonia Ammonia has been detected in the atmospheres of the gas giant planets, including Jupiter, along with other gases like methane, hydrogen, and helium The interior of Saturn may include frozen crystals of ammonia It is naturally found on Deimos and Phobos – the two moons of Mars Interstellar space edit Ammonia was first detected in interstellar space in , based on microwave emissions from the direction of the galactic core This was the first polyatomic molecule to be so detected The sensitivity of the molecule to a broad range of excitations and the ease with which it can be observed in a number of regions has made ammonia one of the most important molecules for studies of molecular clouds The relative intensity of the ammonia lines can be used to measure the temperature of the emitting medium The following isotopic species of ammonia have been detected NH , NH , NH D, NHD , and ND The detection of triply deuterated ammonia was considered a surprise as deuterium is relatively scarce It is thought that the low temperature conditions allow this molecule to survive and accumulate Since its interstellar discovery, NH has proved to be an invaluable spectroscopic tool in the study of the interstellar medium With a large number of transitions sensitive to a wide range of excitation conditions, NH has been widely astronomically detected – its detection has been reported in hundreds of journal articles Listed below is a sample of journal articles that highlights the range of detectors that have been used to identify ammonia The study of interstellar ammonia has been important to a number of areas of research in the last few decades Some of these are delineated below and primarily involve using ammonia as an interstellar thermometer Interstellar formation mechanisms edit Ball and stick model of the diamminesilver I cation, Ag NH + The interstellar abundance for ammonia has been measured for a variety of environments The NH H ratio has been estimated to range from - in small dark clouds up to - in the dense core of the Orion Molecular Cloud Complex Although a total of total production routes have been proposed, the principal formation mechanism for interstellar NH is the reaction NH + + e- ? NH + H• The rate constant, k, of this reaction depends on the temperature of the environment, with a value of × - at K The rate constant was calculated from the formula k a T B For the primary formation reaction, a × - and B - Assuming an NH + abundance of × - and an electron abundance of - typical of molecular clouds, the formation will proceed at a rate of × - cm- s- in a molecular cloud of total density cm- All other proposed formation reactions have rate constants of between and orders of magnitude smaller, making their contribution to the abundance of ammonia relatively insignificant As an example of the minor contribution other formation reactions play, the reaction H + NH ? NH + H has a rate constant of × - Assuming H densities of and NH H ratio of - , this reaction proceeds at a rate of × - , more than orders of magnitude slower than the primary reaction above Some of the other possible formation reactions are H- + NH + ? NH + H PNH + + e- ? P + NH Interstellar destruction mechanisms edit There are total proposed reactions leading to the destruction of NH Of these, were tabulated in extensive tables of the chemistry among C, N, and O compounds A review of interstellar ammonia cites the following reactions as the principal dissociation mechanisms NH + H + ? NH + + H NH + HCO+ ? NH + + CO with rate constants of × - and × - , respectively The above equations , run at a rate of × - and × - , respectively These calculations assumed the given rate constants and abundances of NH H - , H + H × - , HCO+ H × - , and total densities of n , typical of cold, dense, molecular clouds Clearly, between these two primary reactions, equation is the dominant destruction reaction, with a rate ~ , times faster than equation This is due to the relatively Because of its many uses, ammonia is one of the most highly produced inorganic chemicals There are numerous large scale ammonia production plants worldwide, producing a total of million tonnes of nitrogen equivalent to million tonnes of ammonia in China produced % of the worldwide production, followed by India with %, Russia with %, and the United States with % % or more of the ammonia produced is used for fertilizing agricultural crops Ammonia is also used for the production of plastics, fibers, explosives, nitric acid via the Ostwald process and intermediates for dyes and pharmaceuticals Contents hide History Modern ammonia producing plants Sustainable ammonia production See also References External links History edit Before the start of World War I, most ammonia was obtained by the dry distillation of nitrogenous vegetable and animal products by the reduction of nitrous acid and nitrites with hydrogen and also by the decomposition of ammonium salts by alkaline hydroxides or by quicklime, the salt most generally used being the chloride sal ammoniac Today, most ammonia is produced on a large scale by the Haber process with capacities of up to , metric tons per day Ammonia is manufactured on a large scale by Haber's process In this process,N and H gases are allowed to react at high pressure of bar a Modern ammonia producing plants edit Block flow diagram of the ammonia synthesis process A typical modern ammonia producing plant first converts natural gas i e , methane or LPG liquefied petroleum gases such as propane and butane or petroleum naphtha into gaseous hydrogen The method for producing hydrogen from hydrocarbons is referred to as Steam Reforming The hydrogen is then combined with nitrogen to produce ammonia via the Haber Bosch process Starting with a natural gas feedstock, the processes used in producing the hydrogen are The first step in the process is to remove sulfur compounds from the feedstock because sulfur deactivates the catalysts used in subsequent steps Sulfur removal requires catalytic hydrogenation to convert sulfur compounds in the feedstocks to gaseous hydrogen sulfide H + RSH ? RH + H S gas The gaseous hydrogen sulfide is then adsorbed and removed by passing it through beds of zinc oxide where it is converted to solid zinc sulfide H S + ZnO ? ZnS + H O Catalytic steam reforming of the sulfur free feedstock is then used to form hydrogen plus carbon monoxide CH + H O ? CO + H The next step then uses catalytic shift conversion to convert the carbon monoxide to carbon dioxide and more hydrogen CO + H O ? CO + H The carbon dioxide is then removed either by absorption in aqueous ethanolamine solutions or by adsorption in pressure swing adsorbers PSA using proprietary solid adsorption media The final step in producing the hydrogen is to use catalytic methanation to remove any small residual amounts of carbon monoxide or carbon dioxide from the hydrogen CO + H ? CH + H O CO + H ? CH + H O To produce the desired end product ammonia, the hydrogen is then catalytically reacted with nitrogen derived from process air to form anhydrous liquid ammonia This step is known as the ammonia synthesis loop also referred to as the Haber Bosch process H + N ? NH Due to the nature of the typically multi promoted magnetite catalyst used in the ammonia synthesis reaction, only very low levels of oxygen containing especially CO, CO and H O compounds can be tolerated in the synthesis hydrogen and nitrogen mixture gas Relatively pure nitrogen can be obtained by Air separation, but additional oxygen removal may be required Hydrogen storage From Wikipedia, the free encyclopedia Utility scale underground liquid hydrogen storage Methods of hydrogen storage for subsequent use span many approaches, including high pressures, cryogenics, and chemical compounds that reversibly release H upon heating Underground hydrogen storage is useful to provide grid energy storage for intermittent energy sources, like wind power, as well as providing fuel for transportation, particularly for ships and airplanes Most research into hydrogen storage is focused on storing hydrogen as a lightweight, compact energy carrier for mobile applications Liquid hydrogen or slush hydrogen may be used, as in the Space Shuttle However liquid hydrogen requires cryogenic storage and boils around K - °C or - °F Hence, its liquefaction imposes a large energy loss as energy is needed to cool it down to that temperature The tanks must also be well insulated to prevent boil off but adding insulation increases cost Liquid hydrogen has less energy density by volume than hydrocarbon fuels such as gasoline by approximately a factor of four This highlights the density problem for pure hydrogen there is actually about % more hydrogen in a liter of gasoline grams hydrogen than there is in a liter of pure liquid hydrogen grams hydrogen The carbon in the gasoline also contributes to the energy of combustion Compressed hydrogen, by comparison, is stored quite differently Hydrogen gas has good energy density by weight, but poor energy density by volume versus hydrocarbons, hence it requires a larger tank to store A large hydrogen tank will be heavier than the small hydrocarbon tank used to store the same amount of energy, all other factors remaining equal Increasing gas pressure would improve the energy density by volume, making for smaller, but not lighter container tanks see hydrogen tank Compressed hydrogen costs % of the energy content to power the compressor Higher compression without energy recovery will mean more energy lost to the compression step Compressed hydrogen storage can exhibit very low permeation Contents hide Automotive Onboard hydrogen storage Established technologies Compressed hydrogen Liquid hydrogen Proposals and research Chemical storage Metal hydrides Non metal hydrides Carbohydrates Synthesized hydrocarbons Liquid organic hydrogen carriers LOHC Ammonia Amine borane complexes Imidazolium ionic liquids Phosphonium borate Carbonite substances Metal organic frameworks Encapsulation Physical storage Cryo compressed Carbon nanotubes Clathrate hydrates Glass capillary arrays Glass microspheres Stationary hydrogen storage Underground hydrogen storage Power to gas See also References External links Automotive Onboard hydrogen storage edit Timeline Targets assume a kg hydrogen storage system Targets were set by the FreedomCAR Partnership in January between the United States Council for Automotive Research USCAR and U S DOE Targets assume a kg H storage system The targets were not reached in The targets were revised in to reflect new data on system efficiencies obtained from fleets of test cars The ultimate goal for volumetric storage is still above the theoretical density of liquid hydrogen It is important to note that these targets are for the hydrogen storage system, not the hydrogen storage material System densities are often around half those of the working material, thus while a material may store wt% H , a working system using that material may only achieve wt% when the weight of tanks, temperature and pressure control equipment, etc , is considered In , only two storage technologies were identified as being susceptible to meet DOE targets MOF exceeds target for volumetric capacity, while cryo compressed H exceeds more restrictive targets for both gravimetric and volumetric capacity see slide in Established technologies edit net storage density of hydrogen Compressed hydrogen edit Compressed hydrogen is the gaseous state of the element hydrogen which is kept under pressure Compressed hydrogen in hydrogen tanks at bar , psi and bar , psi is used for hydrogen tank systems in vehicles, based on type IV carbon composite technology Car manufacturers have been developing this solution, such as Honda or Nissan Liquid hydrogen edit BMW has been working on liquid tank for cars, producing for example the BMW Hydrogen Proposals and research edit Hydrogen storage technologies can be divided into physical storage, where hydrogen molecules are stored including pure hydrogen storage via compression and liquefication , and chemical storage, where hydrides are stored Chemical storage edit Chemical storage could offer high storage performance due to the strong interaction However, the regeneration of storage material is still an issue A large number of chemical storage systems are under investigation, which involve hydrolysis reactions, hydrogenation dehydrogenation reactions, ammonia borane and other boron hydrides, ammonia, and alane etc Metal hydrides edit Metal hydride hydrogen storage Metal hydrides, such as MgH , NaAlH , LiAlH , LiH, LaNi H , TiFeH and palladium hydride, with varying degrees of efficiency, can be used as a storage medium for hydrogen, often reversibly Some are easy to fuel liquids at ambient temperature and pressure, others are solids which could be turned into pellets These materials have good energy density by volume, although their energy density by weight is often worse than the leading hydrocarbon fuels Most metal hydrides bind with hydrogen very strongly As a result, high temperatures around °C °F – °C °F are required to release their hydrogen content This energy cost can be reduced by using alloys which consists of a strong hydride former and a weak one such as in LiNH , LiBH and NaBH These are able to form weaker bonds, thereby requiring less input to release stored hydrogen However, if the interaction is too weak, the pressure needed for rehydriding is high, thereby eliminating any energy savings The target for onboard hydrogen fuel systems is roughly < °C for release and < bar for recharge – kJ mol H An alternative method for reducing dissociation temperatures is doping with activators This has been successfully used for aluminium hydride but its complex synthesis makes it undesirable for most applications as it is not easily recharged with hydrogen Currently the only hydrides which are capable of achieving the wt % gravimetric goal for see chart above are limited to lithium, boron and aluminium based compounds at least one of the first row elements or Al must be added Research is being done to determine new compounds which can be used to meet these requirements Proposed hydrides for use in a hydrogen economy include simple hydrides of magnesium or transition metals and complex metal hydrides, typically containing sodium, lithium, or calcium and aluminium or boron Hydrides chosen for storage applications provide low reactivity high safety and high hydrogen storage densities Leading candidates are lithium hydride, sodium borohydride, lithium aluminium hydride and ammonia borane A French company McPhy Energy is developing the first industrial product, based on magnesium hydride, already sold to some major clients such as Iwatani and ENEL New Scientist stated that Arizona State University is investigating using a borohydride solution to store hydrogen, which is released when the solution flows over a catalyst made of ruthenium Researchers at University of Pittsburgh and Georgia Tech performed extensive benchmarking simulations on mixtures of several light metal hydrides to predict possible reaction thermodynamics for hydrogen storage Beyond research, Fuel Cell Company Intelligent Energy has released a small Fuel Cell portable power product 'UPP' which uses metal hydride as the storage media See http www beupp com technical specification Non metal hydrides edit The Italian catalyst manufacturer Acta has proposed using hydrazine as an alternative to hydrogen in fuel cells As the hydrazine fuel is liquid at room temperature, it can be handled and stored more easily than hydrogen By storing it in a tank full of a double bonded carbon oxygen carbonyl, it reacts and forms a safe solid called hydrazone By then flushing the tank with warm water, the liquid hydrazine hydrate is released Hydrazine breaks down in the cell to form nitrogen and hydrogen which bonds with oxygen, releasing water Carbohydrates edit Carbohydrates polymeric C H O releases H in a bioreformer mediated by the enzyme cocktail—cell free synthetic pathway biotransformation Carbohydrate provides high hydrogen storage densities as a liquid with mild pressurization and cryogenic constraints It can also be stored as a solid powder Carbohydrate is the most abundant renewable bioresource in the world In May biochemical engineers from the Virginia Polytechnic Institute and State University and biologists and chemists from the Oak Ridge National Laboratory announced a method of producing high yield pure hydrogen from starch and water In , they demonstrated to produce nearly moles of hydrogen per glucose unit from cellulosic materials and water Thanks to complete conversion and modest reaction conditions, they propose to use carbohydrate as a high energy density hydrogen carrier with a density of wt% Synthesized hydrocarbons edit An alternative to hydrides is to use regular hydrocarbon fuels as the hydrogen carrier Then a small hydrogen reformer would extract the hydrogen as needed by the fuel cell However, these reformers are slow to react to changes in demand and add a large incremental cost to the vehicle powertrain Direct methanol fuel cells do not require a reformer, but provide a lower energy density compared to conventional fuel cells, although this could be counterbalanced with the much better energy densities of ethanol and methanol over hydrogen Alcohol fuel is a renewable resource Solid oxide fuel cells can operate on light hydrocarbons such as propane and methane without a reformer, or can run on higher hydrocarbons with only partial reforming, but the high temperature and slow startup time of these fuel cells are problematic for automotive applications Liquid organic hydrogen carriers LOHC edit Reversible hydrogenation of N Ethylcarbazole Unsaturated organic compounds can store huge amounts of hydrogen These Liquid Organic Hydrogen Carriers LOHC are hydrogenated for storage and dehydrogenated again when the energy hydrogen is needed Researches on LOHC was