Editing Urea (section)

==Uses==

===Agriculture===
[[File:Urea process plant UFFL 01.jpg|left|thumb|A plant in [[Bangladesh]] that produces urea fertilizer.]]
More than 90% of world industrial production of urea is destined for use as a nitrogen-release [[fertilizer]].<ref name="Meessen 2012" /> Urea has the highest nitrogen content of all solid nitrogenous fertilizers in common use. Therefore, it has a low transportation cost per unit of [[Plant nutrition#Nitrogen|nitrogen nutrient]]. The most common impurity of synthetic urea is [[biuret]], which impairs plant growth. Urea breaks down in the soil to give [[Ammonium|ammonium ions]] ({{chem2|NH4+}}). The ammonium is taken up by the plant through its roots. In some soils, the ammonium is oxidized by bacteria to give [[nitrate]] ({{chem2|NO3-}}), which is also a nitrogen-rich plant nutrient. The loss of nitrogenous compounds to the atmosphere and runoff is wasteful and environmentally damaging so urea is sometimes modified to enhance the efficiency of its agricultural use. Techniques to make [[controlled-release fertilizer]]s that slow the release of nitrogen include the encapsulation of urea in an inert sealant, and conversion of urea into derivatives such as [[urea-formaldehyde]] compounds, which degrade into ammonia at a pace matching plants' nutritional requirements.

===Resins===
Urea is a raw material for the manufacture of [[urea-formaldehyde resin|formaldehyde based resin]]s, such as UF, MUF, and MUPF, used mainly in wood-based panels, for instance, [[particleboard]], [[fiberboard]], OSB, and [[plywood]].<ref>{{cite journal | last1=Mantanis | first1=George I. | last2=Athanassiadou | first2=Eleftheria Th. | last3=Barbu | first3=Marius C. | last4=Wijnendaele | first4=Kris |title=Adhesive systems used in the European particleboard, MDF and OSB industries | journal=Wood Material Science & Engineering | volume=13 | issue=2 | date=2018-03-15 | issn=1748-0272 | doi=10.1080/17480272.2017.1396622 | pages=104–116 | author1-link=George Mantanis }}</ref>

=== Explosives ===
Urea can be used in a reaction with [[nitric acid]] to make [[urea nitrate]], a [[Explosive material#High explosives|high explosive]] that is used industrially and as part of some [[improvised explosive device]]s.

===Automobile systems===
Urea is used in [[selective non-catalytic reduction|Selective Non-Catalytic Reduction (SNCR)]] and [[selective catalytic reduction|Selective Catalytic Reduction (SCR)]] reactions to reduce the [[nitrogen oxide|{{chem2|NO_{''x''}|}}]] [[pollutant]]s in [[exhaust gas]]es from [[combustion]] from [[Diesel fuel|diesel]], dual fuel, and lean-burn [[natural gas]] engines. The [[BlueTec]] system, for example, injects a water-based urea solution into the exhaust system. Ammonia ({{chem2|NH3}}) produced by the [[hydrolysis]] of urea reacts with nitrogen oxides ({{chem2|NO_{''x''}|}}) and is converted into nitrogen gas ({{chem2|N2}}) and water within the catalytic converter. The conversion of noxious {{chem2|NO_{''x''}|}} to innocuous {{chem2|N2}} is described by the following simplified global equation:<ref>Duo et al., (1992). Can. J. Chem. Eng, '''70''', 1014–1020.</ref>
{{block indent |left=1.5 |text={{chem2|4 NO + 4 NH3 + O2 → 4 N2 + 6 H2O}}}}
When urea is used, a pre-reaction (hydrolysis) occurs to first convert it to ammonia:
{{block indent |left=1.5 |text={{chem2|CO(NH2)2 + H2O → 2 NH3 + CO2}}}}
Being a solid highly [[solubility|soluble]] in water (545 g/L at 25&nbsp;°C),<ref name="Solubility" /> urea is much easier and safer to handle and store than the more [[irritation|irritant]], [[corrosive substance|caustic]] and hazardous [[ammonia]] ({{chem2|NH3}}), so it is the reactant of choice. Trucks and cars using these catalytic converters need to carry a supply of [[diesel exhaust fluid]], also sold as [[AdBlue]], a solution of urea in water.

===Laboratory uses===
Urea in concentrations up to 10&nbsp;[[molar concentration#Units|M]] is a powerful [[protein]] [[denaturation (biochemistry)|denaturant]] as it disrupts the noncovalent bonds in the proteins. This property can be exploited to increase the solubility of some proteins. A mixture of urea and [[choline chloride]] is used as a [[deep eutectic solvent]] (DES), a substance similar to [[ionic liquid]]. When used in a deep eutectic solvent, urea gradually denatures the proteins that are solubilized.<ref>{{cite journal | first1 = Erwann | last1 = Durand | first2 = Jérôme | last2 = Lecomte | first3 = Bruno | last3 =Baréa | first4 = Georges | last4 = Piombo | first5 = Éric | last5 = Dubreucq | first6 = Pierre | last6 = Villeneuve | title = Evaluation of deep eutectic solvents as new media for ''Candida antarctica'' B lipase catalyzed reactions | journal = Process Biochemistry | publisher = [[Elsevier]] | volume = 47 | issue = 12 | date = 2012-12-01 | pages = 2081–2089 | doi = 10.1016/j.procbio.2012.07.027 | issn = 1359-5113 | df = dmy-all}}.</ref>

Urea in concentrations up to 8&nbsp;M can be used to make fixed brain tissue transparent to visible light while still preserving fluorescent signals from labeled cells. This allows for much deeper imaging of neuronal processes than previously obtainable using conventional one photon or two photon confocal microscopes.<ref>{{cite journal | vauthors = Hama H, Kurokawa H, Kawano H, Ando R, Shimogori T, Noda H, Fukami K, Sakaue-Sawano A, Miyawaki A | title = Scale: a chemical approach for fluorescence imaging and reconstruction of transparent mouse brain | journal = Nature Neuroscience | volume = 14 | issue = 11 | pages = 1481–8 | date = August 2011 | pmid = 21878933 | doi = 10.1038/nn.2928 | s2cid = 28281721 }}</ref>

===Medical use===
[[Urea-containing cream]]s are used as topical [[dermatology|dermatological]] products to promote [[Fluid replacement|rehydration]] of the [[skin]]. Urea 40% is indicated for [[psoriasis]], [[xerosis]], [[onychomycosis]], [[ichthyosis]], [[eczema]], [[keratosis]], [[keratoderma]], corns, and [[calluses]]. If covered by an [[occlusive dressing]], 40% urea preparations may also be used for nonsurgical [[debridement]] of [[nail (anatomy)|nails]]. Urea 40% "dissolves the intercellular matrix"<ref>{{cite web|url=http://www.odanlab.com/urisec/winter/|title=UriSec 40 How it Works|date=January 2009|publisher=Odan Laboratories|access-date=February 15, 2011|archive-date=2 February 2011|archive-url=https://web.archive.org/web/20110202150107/http://www.odanlab.com/urisec/winter/|url-status=dead}}</ref><ref name="Urea40">{{cite web |url=https://odanlab.com/product/urisec-40/ |title=UriSec 40% Cream |publisher=Odan Laboratories |access-date=August 20, 2021}}</ref> of the nail plate. Only diseased or dystrophic nails are removed, as there is no effect on healthy portions of the nail.<ref>{{Cite book |last=Habif |first=Thomas P. |url=https://books.google.com/books?id=kDWlWR5UbqQC&dq=Urea+removed+dystrophic+nails&pg=PA961 |title=Clinical Dermatology E-Book |date=2009-11-25 |publisher=Elsevier Health Sciences |isbn=978-0-323-08037-8 |language=en}}</ref> This drug (as [[carbamide peroxide]]) is also used as an earwax removal aid.<ref name="WebMD-eardrops">{{cite web |title=Carbamide Peroxide Drops GENERIC NAME(S): CARBAMIDE PEROXIDE |url=https://www.webmd.com/drugs/2/drug-3616/carbamide-peroxide-otic-ear/details |publisher=WebMD |access-date=August 19, 2021}}</ref>

Urea has also been studied as a [[diuretic]]. It was first used by Dr. W. Friedrich in 1892.<ref>{{cite journal | vauthors = Crawford JH, McIntosh JF | title = The use of urea as a diuretic in advanced heart failure | journal = [[JAMA Internal Medicine|Archives of Internal Medicine]] | volume = 36 | issue = 4 | pages = 530–541 | location = New York | date = 1925 | doi = 10.1001/archinte.1925.00120160088004 }}
</ref> In a 2010 study of ICU patients, urea was used to treat [[Euvolemia|euvolemic]] [[hyponatremia]] and was found safe, inexpensive, and simple.<ref>{{cite journal | vauthors = Decaux G, Andres C, Gankam Kengne F, Soupart A | title = Treatment of euvolemic hyponatremia in the intensive care unit by urea | journal = Critical Care | volume = 14 | issue = 5 | pages = R184 | date = 14 October 2010 | pmid = 20946646 | pmc = 3219290 | doi = 10.1186/cc9292 | doi-access = free }}</ref>

Like [[Saline (medicine)|saline]], urea has been injected into the [[uterus]] to induce [[abortion]], although [[Instillation abortion|this method]] is no longer in widespread use.<ref>{{cite journal | vauthors = Diggory PL | title = Induction of therapeutic abortion by intra-amniotic injection of urea | journal = British Medical Journal | volume = 1 | issue = 5739 | pages = 28–9 | date = January 1971 | pmid = 5539139 | pmc = 1794772 | doi = 10.1136/bmj.1.5739.28 }}</ref>

The [[blood urea nitrogen]] (BUN) test is a measure of the amount of nitrogen in the blood that comes from urea. It is used as a marker of [[renal function]], though it is inferior to other markers such as [[creatinine]] because blood urea levels are influenced by other factors such as diet, dehydration,<ref>{{cite journal | vauthors = Traynor J, Mactier R, Geddes CC, Fox JG | title = How to measure renal function in clinical practice | journal = BMJ | volume = 333 | issue = 7571 | pages = 733–7 | date = October 2006 | pmid = 17023465 | pmc = 1592388 | doi = 10.1136/bmj.38975.390370.7c }}</ref> and liver function.

Urea has also been studied as an excipient in drug-coated balloon (DCB) coating formulations to enhance local drug delivery to stenotic blood vessels.<ref>{{Cite journal|last1=Werk Michael|last2=Albrecht Thomas|last3=Meyer Dirk-Roelfs|last4=Ahmed Mohammed Nabil|last5=Behne Andrea|last6=Dietz Ulrich|last7=Eschenbach Götz|last8=Hartmann Holger|last9=Lange Christian|date=2012-12-01|title=Paclitaxel-Coated Balloons Reduce Restenosis After Femoro-Popliteal Angioplasty|journal=Circulation: Cardiovascular Interventions|volume=5|issue=6|pages=831–840|doi=10.1161/CIRCINTERVENTIONS.112.971630|pmid=23192918|doi-access=free}}</ref><ref>{{Cite journal|last=Wöhrle|first=Jochen|date=2012-10-01|title=Drug-Coated Balloons for Coronary and Peripheral Interventional Procedures|journal=Current Cardiology Reports|volume=14|issue=5|pages=635–641|doi=10.1007/s11886-012-0290-x|pmid=22825918|s2cid=8879713}}</ref> Urea, when used as an [[excipient]] in small doses (~3 μg/mm<sup>2</sup>) to coat DCB surface was found to form crystals that increase drug transfer without adverse toxic effects on vascular [[endothelial cells]].<ref>{{Cite journal|last1=Kolachalama|first1=Vijaya B.|last2=Shazly|first2=Tarek|last3=Vipul C. Chitalia|last4=Lyle|first4=Chimera|last5=Azar|first5=Dara A.|last6=Chang|first6=Gary H.|date=2019-05-02|title=Intrinsic coating morphology modulates acute drug transfer in drug-coated balloon therapy|journal=Scientific Reports|volume=9|issue=1|pages=6839|doi=10.1038/s41598-019-43095-9|pmid=31048704|pmc=6497887|bibcode=2019NatSR...9.6839C}}</ref>

Urea labeled with [[carbon-14]] or [[carbon-13]] is used in the [[urea breath test]], which is used to detect the presence of the bacterium ''[[Helicobacter pylori]]'' (''H. pylori'') in the [[stomach]] and [[duodenum]] of humans, associated with [[peptic ulcer]]s. The test detects the characteristic enzyme [[urease]], produced by ''H. pylori'', by a reaction that produces ammonia from urea. This increases the pH (reduces the acidity) of the stomach environment around the bacteria. Similar bacteria species to ''H. pylori'' can be identified by the same test in animals such as [[ape]]s, [[dog]]s, and [[cat]]s (including [[big cat]]s).

===Miscellaneous uses===
* An ingredient in [[diesel exhaust fluid]] (DEF), which is 32.5% urea and 67.5% de-ionized water. DEF is sprayed into the exhaust stream of diesel vehicles to break down dangerous {{chem2|NO_{''x''}|}} [[Emission standard|emissions]] into harmless [[nitrogen]] and [[water]].
* A component of [[compound feed|animal feed]], providing a relatively cheap source of [[non-protein Nitrogen|nitrogen]] to promote growth
* A non-corroding alternative to [[rock salt]] for road [[deicing|de-icing]].<ref>{{cite book|title=Heavy Duty Truck Systems|date=2015|publisher=Cengage Learning|isbn=9781305073623|page=1117|url=https://books.google.com/books?id=bxrDCgAAQBAJ&pg=PA1117}}</ref> It is often the main ingredient of pet friendly salt substitutes although it is less effective than traditional rock salt or calcium chloride.<ref>{{cite book|title=Chlorides—Advances in Research and Application: 2013 Edition|date=2013|publisher=ScholarlyEditions|isbn=9781481674331|page=77|url=https://books.google.com/books?id=hydgJr0zayAC&pg=PA77}}</ref>
* A main ingredient in hair removers such as [[Nair (hair removal)|Nair]] and [[Veet]]
* A browning agent in factory-produced [[pretzel]]s
* An ingredient in some [[Cream (pharmaceutical)|skin cream]],<ref>{{cite web|url=http://www.dooyoo.co.uk/skin-care/lacura-multi-intensive-serum/1264192/ |title=Lacura Multi Intensive Serum – Review – Excellent value for money – Lacura Multi Intensive Serum "Aqua complete" |publisher=Dooyoo.co.uk |date=2009-06-19 |access-date=2010-12-28}}</ref> [[moisturizer]]s, [[hair conditioner]]s, and [[shampoo]]s
* A [[cloud seeding]] agent, along with other salts<ref>{{cite journal |last1=Knollenberg |first1=Robert G. |title=Urea as an Ice Nucleant for Supercooled Clouds |journal=American Meteorological Society |date=March 1966 |volume=23 |issue=2 |page=197 |doi=10.1175/1520-0469(1966)023<0197:UAAINF>2.0.CO;2 |bibcode=1966JAtS...23..197K |doi-access=free }}</ref>
* A [[flame-proofing agent]], commonly used in dry chemical [[fire extinguisher]] charges such as the urea-[[potassium bicarbonate]] mixture
* An ingredient in many [[tooth whitening]] products
* An ingredient in [[dish soap]]
* Along with [[diammonium phosphate]], as a [[yeast nutrient]], for fermentation of [[sugar]]s into [[ethanol]]
* A nutrient used by [[plankton]] in [[ocean nourishment]] experiments for [[climate engineering|geoengineering]] purposes
* As an additive to extend the working temperature and open time of [[hide glue]]
* As a solubility-enhancing and moisture-retaining additive to [[dye]] baths for textile dyeing or printing<ref>{{cite web |last1=Burch |first1=Paula E. |title=Dyeing FAQ: What is urea for, in dyeing? Is it necessary? |url=http://www.pburch.net/dyeing/FAQ/urea.shtml |website=All About Hand Dyeing |date= 13 November 1999|access-date=24 August 2020}}</ref>
* As an optical parametric oscillator in nonlinear optics<ref>{{cite web|url=https://patents.google.com/patent/US4639923A/en |title=Optical parametric oscillator using urea crystal
 |publisher=Google Patents}}</ref><ref>{{cite journal|title=Urea optical parametric oscillator |journal=Applied Physics Letters |volume=44 |issue=1 |pages=25–27 |publisher=AIP Publishing|doi=10.1063/1.94590 |year=1984 |last1=Donaldson |first1=William R. |last2=Tang |first2=C. L. |bibcode=1984ApPhL..44...25D }}</ref>
* To help prepare a [[alpine skiing]] course by hardening the snow into a icier surface to maintain the integrity of the course.