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ID: 1692086
Article: Sodium hydroxide
(Replaced content with ''''{{Chembox | poda')
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| poda
| Watchedfields = changed
| verifiedrevid = 477162765
| ImageFile1 = SodiumHy jetation needed|date = October 2011}}
| OtherNames = Caustic soda<br/>
Lye <ref name="msd"/><ref name="msd2"/><br/>
White caustic<br/>
Sodium hydrate<ref name="PubChem"/>
| Section1 = {{Chembox Identifiers
| CASNo = 1310-73-2
| CASNo_Ref = {{cascite|correct|CAS}}
| PubChem = 14798
| PubChem_Ref = {{Pubchemcite|correct|Pubchem}}
| ChemSpiderID = 14114
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| UNII = 55X04QC32I
| UNII_Ref = {{fdacite|correct|FDA}}
| EINECS = 215-185-5
| UNNumber = 1823
| KEGG = D01169
| KEGG_Ref = {{keggcite|correct|kegg}}
| MeSHName = Sodium+Hydroxide
| ChEBI = 32145
| ChEBI_Ref = {{ebicite|correct|EBI}}
| RTECS = WB4900000
| Gmelin = 68430
| SMILES = O[Na]
| StdInChI = 1S/Na.H2O/h;1H2/q+1;/p-1
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| InChI = 1/Na.H2O/h;1H2/q+1;/p-1
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| Section2 = {{Chembox Properties
| Formula = {{Chem|NaOH}}
| MolarMass = 39.9971 g mol<sup>−1</sup>
| ExactMass = 39.992509329 g mol<sup>−1</sup>
| Appearance = White, waxy, opaque crystals
| Odor = odorless
| Density = 2.13 g/cm<sup>3</sup>
| MeltingPtC = 318
| BoilingPtC = 1388
| Solubility = 111 g/100 mL (at 20 °C)
| Solvent1 = methanol
| Solubility1 = 23.8 g/100 mL
| Solvent2 = ethanol
| Solubility2 = <<13.9 g/100 mL
| VaporPressure = <2.4 kPa (at 20 °C)
| pKa = 13
| RefractIndex = 1.3576
| Section4 = {{Chembox Thermochemistry
| DeltaHf = −427&nbsp;kJ·mol<sup>−1</sup><ref name=b1>{{cite book| author = Zumdahl, Steven S.|title =Chemical Principles 6th Ed.| publisher = Houghton Mifflin Company| year = 2009| isbn = 0-618-94690-X|page=A23}}</ref>
| Entropy = 64&nbsp;J·mol<sup>−1</sup>·K<sup>−1</sup><ref name=b1/>
| Section4 = {{Chembox Hazards
| ExternalMSDS = [ External MSDS]
| GHSPictograms = {{GHS corrosion}}
| EUIndex = 011-002-00-6
| EUClass = {{Hazchem C}}
| RPhrases = {{R35}}
| SPhrases = {{S1/2}}, {{S26}}, {{S37/39}}, {{S45}}
| NFPA-H = 3
| NFPA-F = 0
| NFPA-R = 1
| Section5 = {{Chembox Related
| OtherAnions = [[Sodium hydrosulfide]]
| OtherCations = [[Caesium hydroxide]]<br />
[[Lithium hydroxide]]<br />
[[Potassium hydroxide]]<br />
[[Rubidium hydroxide]]
'''Sodium hydroxide''', also known as '''caustic soda''',<ref name="msd">{{cite web|title=Material Safety Datasheet|url=}}</ref><ref name="msd2">{{cite web|title=Material Safety Datasheet 2|url=}}</ref> or [[lye]], is an [[inorganic compound]] with the [[chemical formula]] NaOH. It is a white solid and highly [[corrosive|caustic]] metallic [[Base (chemistry)|base]] and [[alkali]] [[Salt (chemistry)|salt]] which is available in pellets, flakes, granules, and as prepared solutions at a number of different concentrations.<ref></ref> Sodium hydroxide forms an approximately 50% (by weight) [[saturated solution]] with water.<ref></ref>
Sodium hydroxide is soluble in [[water]], [[ethanol]] and [[methanol]]. This [[alkali]] is [[deliquescent]] and readily absorbs [[moisture]] and [[carbon dioxide]] in [[air]].
Sodium hydroxide is used in many industries, mostly as a strong [[chemical compound|chemical]] [[pH|base]] in the manufacture of [[wood pulp|pulp]] and [[paper]], [[textile]]s, [[drinking water]], [[soap]]s and [[detergent]]s and as a [[drain cleaner]]. Worldwide production in 2004 was approximately 60&nbsp;million [[tonne]]s, while demand was 51&nbsp;million tonnes.<ref name = Ullmann/>
===Physical properties===
Pure sodium hydroxide is a whitish solid, sold in pellets, flakes, and granular form, as well as in solution. It is highly soluble in water, with a lower solubility in ethanol and methanol, but is insoluble in ether and other non-polar solvents.
Similar to the hydration of sulfuric acid, [[Dissolution (chemistry)|dissolution]] of solid sodium hydroxide in water is a highly exothermic reaction in which a large amount of heat is liberated, posing a threat to safety through the possibility of splashing. The resulting solution is usually colourless and odorless with slippery feeling upon contact in common with other alkalis.
===Chemical properties===
====Reaction with acids====
Sodium hydroxide reacts with protic acids to produce water and the corresponding salts. For example, when sodium hydroxide reacts with [[hydrochloric acid]], [[sodium chloride]] is formed:
:NaOH([[Aqueous|aq]]) + [[Hydrochloric acid|HCl]](aq) → [[Sodium chloride|NaCl]](aq) + [[Water (molecule)|H<sub>2</sub>O]]([[Liquid|l]])
In general, such [[neutralization (chemistry)|neutralization]] reactions are represented by one simple net ionic equation:
:[[Hydroxide|OH<sup>−</sup>]](aq) + [[Proton|H<sup>+</sup>]](aq) → [[Water|H<sub>2</sub>O]](l)
This type of reaction with a strong acid releases heat, and hence is [[exothermic reaction|exothermic]]. Such [[acid-base reaction]]s can also be used for [[titration]]s. However, sodium hydroxide is not used as a [[primary standard]] because it is [[hygroscopic]] and absorbs carbon dioxide from air.
====Reaction with acidic oxides====
Sodium hydroxide also reacts with [[acid anhydride|acidic oxides]], such as [[sulfur dioxide]]. Such reactions are often used to "[[Scrubber|scrub]]" harmful acidic gases (like SO<sub>2</sub> and H<sub>2</sub>S) produced in the burning of coal and thus prevent their release into the atmosphere. For example,
:2 NaOH + [[Carbon dioxide|CO<sub>2</sub>]] → [[Sodium carbonate|Na<sub>2</sub>CO<sub>3</sub>]] + H<sub>2</sub>O
====Reaction with amphoteric metals and oxides====
Glass reacts slowly with aqueous sodium hydroxide solutions at ambient temperatures to form soluble [[silicate]]s. Because of this, glass joints and [[stopcock]]s exposed to sodium hydroxide have a tendency to "freeze". [[Laboratory flask|Flask]]s and glass-lined [[chemical reactor]]s are damaged by long exposure to hot sodium hydroxide, which also frosts the glass. Sodium hydroxide does not attack [[iron]] since iron does not have [[amphoteric]] properties (i.e., it only dissolves in acid, not base). A few [[transition metal]]s, however, may react vigorously with sodium hydroxide.
In 1986, an aluminium [[tank truck|road tanker]] in the UK was mistakenly used to transport 25% sodium hydroxide solution,<ref>{{Citation
| last = Stamell
| first = Jim
| title = EXCEL HSC Chemistry
| pages = 199
| publisher = Pascal Press
| publication-date = 2001
| isbn = 978-1-74125-299-6
}}</ref> causing pressurization of the contents and damage to the tanker. The pressurization was due to the hydrogen gas which is produced in the reaction between sodium hydroxide and aluminium:
: 2 Al + 2 NaOH + 6 H<sub>2</sub>O → 2 Na[Al(OH)<sub>4</sub>] + 3 H<sub>2</sub>
Unlike sodium hydroxide, the hydroxides of most transition metals are insoluble, and therefore sodium hydroxide can be used to [[precipitate]] transition metal hydroxides. The following colours are observed: Blue-copper, Green-Iron(II), Yellow/Brown-Iron(III). Zinc and Lead salts dissolve in excess sodium hydroxide to give a clear solution of Na<sub>2</sub>ZnO<sub>2</sub> or Na<sub>2</sub>PbO<sub>2</sub>.
[[Aluminium hydroxide]] is used as a gelatinous [[Flocculation#Flocculants|flocculant]] to filter out particulate matter in [[water treatment]]. Aluminium hydroxide is prepared at the treatment plant from [[aluminium sulfate]] by reacting it with sodium hydroxide.
:Al<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub> + 6 NaOH → 2 Al(OH)<sub>3</sub> + 3 Na<sub>2</sub>SO<sub>4</sub>
Sodium hydroxide can be used for the base-driven [[hydrolysis]] of [[ester]]s (as in [[saponification]]), [[amide]]s and [[alkyl halide]]s. However, the limited solubility of sodium hydroxide in organic solvents means that the more [[soluble]] [[potassium hydroxide]] (KOH) is often preferred.
Sodium hydroxide is industrially produced as a 50% solution by variations of the electrolytic [[chloralkali process]]. [[Chlorine gas]] is also produced in this process. Solid sodium hydroxide is obtained from this solution by the evaporation of water. Solid sodium hydroxide is most commonly sold as flakes, [[prill]]s, and cast blocks.<ref name = Ullmann/>
In 2004, world production was estimated at 60 million dry metric tonnes of sodium hydroxide, and demand was estimated at 51 million tonnes.<ref name = Ullmann>{{Ullmann | doi = 10.1002/14356007.a24_345.pub2 | title = Sodium Hydroxide | author = Cetin Kurt, Jürgen Bittner | }}</ref> In 1998, total world production was around 45&nbsp;million [[tonne]]s. North America and Asia collectively contributed around 14&nbsp;million tonnes, while Europe produced around 10&nbsp;million tonnes. In the United States, the major producer of sodium hydroxide is the [[Dow Chemical Company]], which has annual production around 3.7&nbsp;million [[tonne]]s from sites at [[Freeport, Texas|Freeport]], Texas, and [[Plaquemine, Louisiana|Plaquemine]], Louisiana. Other major US producers include [[Oxychem|OxyChem]], [[PPG Industries|PPG]], [[Olin Corporation|Olin]], Pioneer Companies, Inc. (PIONA, which was purchased by Olin), and [[Formosa Plastics Group|Formosa]]. All of these companies use the [[chloralkali process]].<ref name="Kirk">Kirk-Othmer Encyclopedia of Chemical Technology 5th edition ([ online], account needed), John Wiley & Sons. Accessed November 21, 2005.</ref>
Historically sodium hydroxide is produced by treating [[sodium carbonate]] with [[calcium hydroxide]] in a [[metathesis reaction]]. (Sodium hydroxide is soluble while calcium carbonate is not.) This process was called causticizing.<ref>{{cite book |last1= Deming|first1=Horace G. |title=General Chemistry: An Elementary Survey Emphasizing Industrial Applications of Fundamental Principles |edition=2nd |year=1925 |publisher=John Wiley & Sons, Inc. |location=New York |page=452 }}</ref>
:Ca(OH)<sub>2</sub>(aq) + Na<sub>2</sub>CO<sub>3</sub>(s) &rarr; CaCO<sub>3</sub>&darr; + 2 NaOH(aq)
This process was superseded by the [[Solvay process]] in the late 19th century, which was in turn supplanted by the [[chloralkali process]] which we use today.
Sodium hydroxide is also produced by combining pure sodium metal with water. The byproducts are hydrogen gas and heat, often resulting in a flame, making this a common demonstration of the reactivity of alkali metals in academic environments; however, it is not commercially viable, as the isolation of sodium metal is typically performed by reduction or electrolysis of sodium compounds including sodium hydroxide.
[[File:Lye.jpg|thumb|Canister of sodium hydroxide.]]
Sodium hydroxide is the principal strong [[base (chemistry)|base]] used in the chemical industry. In bulk it is most often handled as an [[aqueous]] [[solution]], since solutions are cheaper and easier to handle. Sodium hydroxide, a strong base, is responsible for most of these applications. Another strong base such as [[potassium hydroxide]] is likely to yield positive results as well.
Overall 56% of sodium hydroxide produced is used by the chemical industry, with 25% of the same total used by the paper industry. Sodium hydroxide is also used for the manufacture of sodium salts and detergents, for pH regulation, and for organic synthesis. It is used in the [[Bayer process]] of [[aluminium]] production.<ref name = Ullmann/>
Sodium hydroxide is used in many scenarios where it is desirable to increase the alkalinity of a mixture, or to neutralize acids.
For example, sodium hydroxide is used as an additive in [[drilling mud]] to increase [[alkalinity]] in [[bentonite]] mud systems, to increase the mud [[viscosity]], and to neutralise any [[acid gas]] (such as [[hydrogen sulfide]] and [[carbon dioxide]]) which may be encountered in the [[geological formation]] as drilling progresses.
In the same industry, poor quality [[crude oil]] can be treated with sodium hydroxide to remove [[sulfur]]ous impurities in a process known as ''caustic washing''. As above, sodium hydroxide reacts with weak acids such as hydrogen sulfide and mercaptans to give the non-volatile sodium salts which can be removed. The waste which is formed is toxic and difficult to deal with, and the process is banned in many countries because of this. In 2006, [[Trafigura]] used the process and then [[2006 Côte d'Ivoire toxic waste dump|dumped the waste in Africa]].<ref name="Guardian">{{cite news|url=|title=Trafigura case: toxic slop left behind by caustic washing|last=Sample|first=Ian|date=16 September 2009 |publisher=The Guardian|accessdate=2009-09-17}}</ref><ref name="bbc">{{cite news|url=|title=Trafigura knew of waste dangers|date=16 September 2009|publisher=BBC Newsnight|accessdate=2009-09-17}}</ref> {{see also|hydrodesulfurization}}
===Chemical pulping===
{{main|Pulp (paper)}}
Sodium hydroxide is also widely used in pulping of wood for making paper or regenerated fibers. Along with [[sodium sulfide]], sodium hydroxide is a key component of the white liquor solution used to separate [[lignin]] from [[cellulose]] [[fiber]]s in the [[kraft process]]. It also plays a key role in several later stages of the process of [[Bleaching of wood pulp|bleaching the brown pulp]] resulting from the pulping process. These stages include [[oxygen]] delignification, [[oxidation|oxidative]] extraction, and simple extraction, all of which require a strong alkaline environment with a pH > 10.5 at the end of the stages.
===Tissue digestion===
In a similar fashion, sodium hydroxide is used to digest tissues, such as in a process that was used with farm animals at one time. This process involved placing a carcass into a sealed chamber, then adding a mixture of sodium hydroxide and water (which breaks the chemical bonds that keep the flesh intact). This eventually turns the body into a liquid with coffee-like appearance,<ref name="Ayres">Ayres, Chris (27 February 2010) [ Clean green finish that sends a loved one down the drain] Times Online. Retrieved 2013-02-20.</ref><ref name="carcassdisposal">Thacker, H. Leon; Kastner, Justin (August 2004). [ ''Carcass Disposal: A Comprehensive Review. Chapter 6'']. National Agricultural Biosecurity Center, Kansas State University, 2004. Retrieved 2010-03-08</ref> and the only solid that remains are bone hulls, which could be crushed between one's fingertips.<ref name="Roach">Roach, Mary (2004). ''Stiff: The Curious Lives of Human Cadavers'', New York: W.W. Norton & Company. ISBN 0-393-32482-6.</ref> Sodium hydroxide is frequently used in the process of decomposing [[roadkill]] dumped in landfills by animal disposal contractors.<ref name="carcassdisposal"/> Due to its low cost and availability, it has been used to dispose of corpses by criminals. In Mexico, a man who worked for drug cartels admitted disposing over 300 bodies with it.<ref>{{cite web | url = | author = William Booth | title = 'Stewmaker' Stirs Horror in Mexico | publisher = ''[[Washington Post]]'' | date = January 27, 2009}}</ref>
===Dissolving amphoteric metals and compounds===
Strong bases attack [[aluminium]]. Sodium hydroxide reacts with aluminium and water to release hydrogen gas. The aluminium takes the oxygen atom from sodium hydroxide, which in turn takes the oxygen atom from the water, and releases the two hydrogen atoms, The reaction thus produces [[hydrogen]] gas and [[sodium aluminate]]. In this reaction, sodium hydroxide acts as an agent to make the solution alkaline, which aluminium can dissolve in. This reaction can be useful in etching, removing anodizing, or converting a polished surface to a satin-like finish, but without further [[Passivation (chemistry)|passivation]] such as [[anodizing]] or [[alodining]] the surface may become degraded, either under normal use or in severe atmospheric conditions.
In the [[Bayer process]], sodium hydroxide is used in the refining of [[alumina]] containing ores ([[bauxite]]) to produce alumina (aluminium oxide) which is the raw material used to produce [[aluminium]] metal via the [[electrolysis|electrolytic]] [[Hall-Héroult process]]. Since the alumina is [[amphoteric]], it dissolves in the sodium hydroxide, leaving impurities less soluble at high pH such as [[iron oxides]] behind in the form of a highly alkaline [[red mud]]. {{see also | Ajka alumina plant accident}}
Other amphoteric metals are zinc and lead which dissolve in concentrated sodium hydroxide solutions to give [[sodium zincate]] and sodium plumbate respectively.
===Esterification and transesterification reagent===
Sodium hydroxide is traditionally used in soap making ([[cold process]] soap, [[saponification]]).<ref name="Morfit">{{cite book|title =A treatise on chemistry applied to the manufacture of soap and candles|first= Campbell|last=Morfit|authorlink=Campbell Morfit|publisher=Parry and McMillan|year = 1856|url =}}</ref> It was made in the nineteenth century for a hard surface rather than liquid product because it was easier to store and transport.
For the manufacture of [[biodiesel]], sodium hydroxide is used as a [[catalyst]] for the [[transesterification]] of methanol and triglycerides. This only works with [[anhydrous]] sodium hydroxide, because combined with water the fat would turn into [[soap]], which would be tainted with [[methanol]]. It is used more often than [[potassium hydroxide]] because it is cheaper and a smaller quantity is needed.
Sodium hydroxide is also being used experimentally in a new technology to create synthetic [[gasoline]].<ref>{{cite web
| url =
| title = British engineers produce amazing 'petrol from air' technology
| author = Andrew Hough
| date = 18 October 2012
| publisher = The Telegraph
| accessdate = 21 October 2012
===Food preparation===
Food uses of sodium hydroxide include washing or chemical peeling of [[fruits]] and [[vegetables]], [[chocolate]] and [[Cocoa mass|cocoa]] processing, [[caramel coloring]] production, [[poultry]] scalding, [[soft drink]] processing, and thickening [[ice cream]]. [[Olive]]s are often soaked in sodium hydroxide for softening; [[Pretzel]]s and [[Germany|German]] [[lye roll]]s are glazed with a sodium hydroxide solution before baking to make them crisp. Owing to the difficulty in obtaining food grade sodium hydroxide in small quantities for home use, [[sodium carbonate]] is often used in place of sodium hydroxide.<ref name="Hominy">{{cite web|url=| title=Hominy without Lye| publisher=National Center for Home Food Preservation}}</ref>
Specific foods processed with sodium hydroxide include:
*The [[Scandinavia]]n delicacy known as [[lutefisk]] (from ''lutfisk'', "lye fish").
*[[Hominy]] is dried [[maize]] (corn) kernels reconstituted by soaking in [[lye]]-water. These expand considerably in size and may be further processed by frying to make [[corn nuts]] or by drying and grinding to make [[grits]]. [[Nixtamal]] is similar, but uses [[calcium hydroxide]] instead of sodium hydroxide.
*Sodium hydroxide is also the chemical that causes gelling of egg whites in the production of [[Century egg]]s.
*German [[pretzel]]s are poached in a boiling [[sodium carbonate]] solution or cold sodium hydroxide solution before baking, which contributes to their unique crust.
*Lye-water is an essential ingredient in the crust of the traditional baked Chinese moon cakes.
*Most yellow coloured [[Chinese noodles]] are made with [[lye]]-water but are commonly mistaken for containing egg.
*Some methods of preparing olives involve subjecting them to a lye-based brine.<ref>{{cite web |url= |title=Olives: Safe Methods for Home Pickling (application/pdf Object) | |year=2010 |accessdate=January 22, 2012}}</ref>
*The Filipino dessert (''kakanin'') called ''kutsinta'' uses a bit of lye water to help give the rice flour batter a jelly like consistency. A similar process is also used in the kakanin known as ''pitsi-pitsi'' or ''pichi-pichi'' except that the mixture uses grated [[cassava]] instead of rice flour.
===Cleaning agent===
{{Main|Cleaning agent}}
Sodium hydroxide is frequently used as an industrial [[cleaning agent]] where it is often called "caustic". It is added to water, heated, and then used to clean process equipment, storage tanks, etc. It can dissolve [[grease (lubricant)|grease]], [[oils]], [[fat]]s and [[protein]] based deposits. It is also used for cleaning waste discharge pipes under sinks and drains in domestic properties. [[Surfactants]] can be added to the sodium hydroxide solution in order to stabilize dissolved substances and thus prevent redeposition. A sodium hydroxide soak solution is used as a powerful degreaser on [[stainless steel]] and glass bakeware. It is also a common ingredient in oven cleaners.
A common use of sodium hydroxide is in the production of [[parts washer]] [[detergent]]s. Parts washer detergents based on sodium hydroxide are some of the most aggressive parts washer cleaning chemicals. The sodium hydroxide based detergent include surfactants, rust inhibitors and defoamers. A parts washer heats water and the detergent in a closed cabinet and then sprays the heated sodium hydroxide and hot water at pressure against dirty parts for degreasing applications. Sodium hydroxide used in this manner replaced many solvent based systems in the early 1990s{{Citation needed|date=May 2010}} when [[1,1,1-Trichloroethane|trichloroethane]] was outlawed by the [[Montreal Protocol]]. Water and sodium hydroxide detergent based parts washers are considered to be an environmental improvement over the solvent based cleaning methods.
[[File:NaOH - drain-cleaner.jpg|thumb|left|upright|[[Hardware store]]s grade sodium hydroxide to be used as a type of [[drain cleaner#Alkaline drain openers|drain cleaner]]s.]]
[[File:Paint stripping with caustic soda.jpg|thumb|upright|Paint stripping with caustic soda]]
Sodium hydroxide is used in the home as a type of [[drain cleaner#Alkaline drain openers|drain opener]] to unblock clogged drains, usually in the form of a dry crystal or as a thick liquid gel. The alkali dissolves [[fat|greases]] to produce [[water soluble]] [[product (chemistry)|products]]. It also [[hydrolysis|hydrolyzes]] the [[proteins]] such as those found in [[hair]] which may block water pipes. These reactions are sped by the [[exothermic|heat generated]] when sodium hydroxide and the other chemical components of the cleaner dissolve in water. Such [[drain cleaner#Alkaline drain openers|alkaline drain cleaners]] and their [[drain cleaner#Acidic drain openers|acidic versions]] are highly [[corrosive]] and should be handled with great caution.
Sodium hydroxide is used in some [[relaxer]]s to [[straighten hair]]. However, because of the high incidence and intensity of chemical burns, manufacturers of chemical relaxers use other alkaline chemicals in preparations available to average consumers. Sodium hydroxide relaxers are still available, but they are used mostly by professionals.
A solution of sodium hydroxide in water was traditionally used as the most common paint stripper on wooden objects. Its use has become less common, because it can damage the wood surface, raising the grain and staining the colour.
===Historical uses===
Sodium hydroxide has been used for detection of [[carbon monoxide poisoning]], with blood samples of such patients turning to a [[vermilion]] color upon the addition of a few drops of sodium hydroxide.<ref>[ Page 168] in: ''The Detection of poisons and strong drugs''.
Author: Wilhelm Autenrieth.
Publisher: P. Blakiston's son & Company, 1909.</ref> Today, carbon monoxide poisoning can be detected by [[CO oximetry]].
=== Experimental ===
* [[Sodium hydroxide test]] for flavonoids
[[File:Sodium hydroxide burn.png|thumb|right|[[Chemical burn]]s caused by sodium hydroxide solution photographed 44 hours after exposure.]]
Like other [[corrosive]] [[acid]]s and [[alkali]]s, drops of sodium hydroxide solutions can decompose [[proteins]] and [[lipids]] in [[skin]], [[eye]]s or other [[Tissue (biology)|living tissues]] via [[amide hydrolysis]] and [[ester hydrolysis]], which consequently causes [[chemical burn]]s and may induce permanent [[blindness]] if it contacts eyes.<ref name="msd"/><ref name="msd2"/> Solid alkali may also express its corrosive nature if there is water so [[protective equipment]] such as [[rubber gloves]], [[safety clothing]] and [[eye protection]] should always be used when handling the material or its solutions.
Moreover, [[solvation|dissolution]] of sodium hydroxide is highly [[exothermic]], and the resulting heat may cause heat burns or ignite flammables. It also produces heat when reacted with acids.
The standard first aid measures for alkali spills on the skin is, as for other corrosives, irrigation with large quantities of water. Washing is continued for at least ten to fifteen minutes.
Sodium hydroxide is corrosive to several metals, like [[aluminium]] which reacts with the alkali to produce flammable [[hydrogen]] gas on contact:<ref>{{cite web |url= |title=aluminium_water_hydrogen.pdf (application/pdf Object) | |year=2008 |accessdate=January 15, 2013}}</ref>
:2 Al + 2 NaOH + 2 H<sub>2</sub>O → 3 H<sub>2</sub> + 2 NaAlO<sub>'''2'''</sub>
:2 Al + 6 NaOH + x H<sub>2</sub>O → 3 H<sub>2</sub> + 2 Na<sub>3</sub>AlO<sub>'''3'''</sub> + x H<sub>2</sub>O
:2 Al + 2 NaOH + 6 H<sub>2</sub>O → 3 H<sub>2</sub> + 2 NaAl(OH)<sub>'''4'''</sub>
Sodium hydroxide is also mildly corrosive to [[glass]], which can cause damage to [[glazing (window)|glazing]] or freezing of [[ground glass joint]]s. Careful storage is needed.
<br clear = left/>
==See also==
*[[HAZMAT Class 8 Corrosive Substances]]
*[[Common chemicals]]
*[[List of elemental cleaning agents]]
*Euro Chlor-How is chlorine made? [ Chlorine Online]
*Heaton, A. (1996) ''An Introduction to Industrial Chemistry'', 3rd edition, New York:Blackie. ISBN 0-7514-0272-9.
==External links==
{{Commons category}}
*[ International Chemical Safety Card 0360]
*[ NIOSH Pocket Guide to Chemical Hazards]
*[ CDC - Sodium Hydroxide - NIOSH Workplace Safety and Health Topic]
*[ European Union Risk Assessment Report]
*[ Production by brine electrolysis]
*[ Titration of acids with sodium hydroxide; freeware for data analysis, simulation of curves and pH calculation]
*[ Caustic soda production in continuous causticising plant by lime soda process]
{{Sodium compounds}}
{{DEFAULTSORT:Sodium Hydroxide}}
[[Category:Chemical engineering]]
[[Category:Cleaning products]]
[[Category:Household chemicals]]
[[Category:Sodium compounds]]
[[Category:Inorganic compounds]]
[[Category:Deliquescent substances]]
[[Category:Photographic chemicals]]
Reason: ANN scored at 0.974961
Reporter Information
Reporter: JimmiXzS (anonymous)
Date: Thursday, the 13th of October 2016 at 02:38:42 PM
Status: Reported
Friday, the 7th of August 2015 at 09:11:45 PM #100441
Bradley (anonymous)


Thursday, the 13th of October 2016 at 02:38:42 PM #106418
JimmiXzS (anonymous)