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Sodium hydroxide, also known as
lye A lye is a metal hydroxide traditionally obtained by leaching wood ashes, or a strong alkali In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of at ...
and caustic soda, is an
inorganic compound In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds composed of atoms, m ...
with the formula NaOH. It is a white solid
ionic compound structure of sodium chloride, NaCl, a typical ionic compound. The purple spheres represent sodium cations, Na+, and the green spheres represent chloride anions, Cl−. The yellow stipples show the electrostatic forces. In chemistry, an ionic compo ...
consisting of
sodium Sodium is a with the  Na (from Latin ''natrium'') and  11. It is a soft, silvery-white, highly reactive . Sodium is an , being in of the periodic table. Its only stable is 23Na. The free metal does not occur in nature, and must be ...

sodium
cation An ion () is an atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are u ...
s and
hydroxide Hydroxide is a diatomic anion with chemical formula A chemical formula is a way of presenting information about the chemical proportions of atom An atom is the smallest unit of ordinary matter In classical physics and general che ...
anion An ion () is an atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are u ...
s . Sodium hydroxide is a highly
caustic Caustic most commonly refers to: * Causticity, a property of various corrosive substances ** Sodium hydroxide, sometimes called ''caustic soda'' ** Potassium hydroxide, sometimes called ''caustic potash'' ** Calcium oxide, sometimes called ''caustic ...

caustic
base Base or BASE may refer to: Brands and enterprises * Base (mobile telephony provider), a Belgian mobile telecommunications operator *Base CRM Base CRM (originally Future Simple or PipeJump) is an enterprise software company based in Mountain Vie ...
and
alkali In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds composed of ato ...

alkali
that decomposes
protein Proteins are large s and s that comprise one or more long chains of . Proteins perform a vast array of functions within organisms, including , , , providing and , and from one location to another. Proteins differ from one another primarily ...

protein
s at ordinary ambient
temperature Temperature ( ) is a physical quantity that expresses hot and cold. It is the manifestation of thermal energy Thermal radiation in visible light can be seen on this hot metalwork. Thermal energy refers to several distinct physical concept ...

temperature
s and may cause severe
chemical burn A chemical burn occurs when living tissue is exposed to a corrosive substance (such as a strong acid An acid is a molecule or ion capable of donating a proton (hydrogen ion H+) (a Brønsted–Lowry acid–base theory, Brønsted–Lowry acid ...
s. It is highly soluble in
water Water (chemical formula H2O) is an , transparent, tasteless, odorless, and , which is the main constituent of 's and the s of all known living organisms (in which it acts as a ). It is vital for all known forms of , even though it provide ...

water
, and readily absorbs
moisture 150px, Dew on a spider web Moisture is the presence of a liquid, especially water, often in trace amounts. Small amounts of water may be found, for example, in the air (humidity Humidity is the concentration of water vapor present in the air ...
and
carbon dioxide Carbon dioxide (chemical formula A chemical formula is a way of presenting information about the chemical proportions of atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is ...

carbon dioxide
from the
air File:Atmosphere gas proportions.svg, Composition of Earth's atmosphere by volume, excluding water vapor. Lower pie represents trace gases that together compose about 0.043391% of the atmosphere (0.04402961% at April 2019 concentration ). Number ...

air
. It forms a series of
hydrate In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds composed of atoms, m ...
s NaOH·''n''. The monohydrate NaOH· crystallizes from water solutions between 12.3 and 61.8 °C. The commercially available "sodium hydroxide" is often this monohydrate, and published data may refer to it instead of the
anhydrous A substance is anhydrous if it contains no water Water (chemical formula H2O) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the flui ...
compound. As one of the simplest hydroxides, sodium hydroxide is frequently utilized alongside neutral
water Water (chemical formula H2O) is an , transparent, tasteless, odorless, and , which is the main constituent of 's and the s of all known living organisms (in which it acts as a ). It is vital for all known forms of , even though it provide ...

water
and acidic
hydrochloric acid Hydrochloric acid +(aq) Cl−(aq) or H3O+ Cl− also known as muriatic acid, is an of ( ). It is a colorless solution with a distinctive smell. It is classified as a . It is a component of the in the digestive systems of most animal spec ...

hydrochloric acid
to demonstrate the pH scale to chemistry students. Sodium hydroxide is used in many industries: in the manufacture of pulp and
paper Paper is a thin sheet material Material is a substance Substance may refer to: * Substance (Jainism), a term in Jain ontology to denote the base or owner of attributes * Chemical substance, a material with a definite chemical composition * ...

paper
,
textile A textile is a flexible material made by creating an interlocking bundle of yarn Yarn is a long continuous length of interlocked fibres, suitable for use in the production of textiles, sewing, crocheting, knitting, weaving, embroidery, o ...

textile
s,
drinking water Drinking water, also known as potable water, is that is safe to or use for . The amount of drinking water required to maintain good health varies, and depends on physical activity level, age, health-related issues, and environmental conditions ...

drinking water
,
soap Soap is a of a used in a variety of cleansing and lubricating products. In a domestic setting, soaps are s usually used for , , and other types of . In industrial settings, soaps are used as s, components of some s, and precursors to s. Wh ...

soap
s and
detergent A detergent is a surfactant Surfactants are compounds that lower the surface tension (or interfacial tension) between two liquids, between a gas and a liquid, or between a liquid and a solid. Surfactants may act as detergents, wetting ...
s, and as a
drain cleaner A drain cleaner is a chemical product that unblocks sewer pipes or clogged wastewater drains. The term may also refer to a mechanical device such as a plumber's snake, drain auger, toilet plunger, or similar device. Occasionally, the term is applie ...
. Worldwide production in 2004 was approximately 60 million tons, while demand was 51 million tons.


Properties


Physical properties

Pure sodium hydroxide is a colorless crystalline solid that melts at without decomposition, and with a boiling point of . It is highly soluble in water, with a lower solubility in polar solvents such as
ethanol Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an . It is a simple with the C2H6O. Its formula can be also written as −− or (an linked to a group), and is often as EtOH. Ethanol is a , , ...

ethanol
and
methanol Methanol, also known as methyl alcohol, amongst other names, is a chemical A chemical substance is a form of matter having constant chemical composition and characteristic properties. Some references add that chemical substance cannot be se ...

methanol
. NaOH is insoluble in ether and other non-polar solvents. Similar to the hydration of sulfuric acid,
dissolution Dissolution may refer to: Arts and entertainment Books * Dissolution (Forgotten Realms novel), ''Dissolution'' (''Forgotten Realms'' novel), a 2002 fantasy novel by Richard Lee Byers * Dissolution (Sansom novel), ''Dissolution'' (Sansom novel), a 2 ...
of solid sodium hydroxide in water is a highly
exothermic reaction reaction is famously exothermic. The reduction of iron(III) oxide by aluminium Aluminium (aluminum in American American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the Uni ...
where a large amount of heat is liberated, posing a threat to safety through the possibility of splashing. The resulting solution is usually colorless and odorless. As with other alkaline solutions, it feels slippery with skin contact due to the process of
saponification Saponification is a process that involves the conversion of fat, oil, or lipid, into soap and alcohol by the action of aqueous alkali (e.g. Sodium hydroxide, NaOH). Soaps are salts of fatty acids, which in turn are carboxylic acids with long carbon ...

saponification
that occurs between NaOH and natural skin oils.


Viscosity

Concentrated (50%) aqueous solutions of sodium hydroxide have a characteristic
viscosity The viscosity of a is a measure of its to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, has a higher viscosity than . Viscosity can be conceptualized as quantifying the inter ...

viscosity
, 78 m Pa·s, that is much greater than that of water (1.0 mPa·s) and near that of olive oil (85 mPa·s) at room temperature. The viscosity of aqueous NaOH, as with any liquid chemical, is inversely related to its service temperature, i.e., its viscosity decreases as temperature increases, and vice versa. The viscosity of sodium hydroxide solutions plays a direct role in its application as well as its storage.


Hydrates

Sodium hydroxide can form several hydrates NaOH·''n'', which result in a complex solubility diagram that was described in detail by S. U. Pickering in 1893.Spencer Umfreville Pickering (1893): "LXI.—The hydrates of sodium, potassium, and lithium hydroxides". ''Journal of the Chemical Society, Transactions'', volume 63, pages 890–909. The known hydrates and the approximate ranges of temperature and concentration (mass percent of NaOH) of their saturated water solutions are: * Heptahydrate, NaOH·7: from −28 °C (18.8%) to −24 °C (22.2%). * Pentahydrate, NaOH·5: from −24 °C (22.2%) to −17.7 (24.8%). * Tetrahydrate, NaOH·4, α form: from −17.7 (24.8%) to +5.4 °C (32.5%).S. C. Mraw, W. F. Giauque (1974): "Entropies of the hydrates of sodium hydroxide. III. Low-temperature heat capacities and heats of fusion of the α and β crystalline forms of sodium hydroxide tetrahydrate". ''Journal of Physical Chemistry'', volume 78, issue 17, pages 1701–1709. * Tetrahydrate, NaOH·4, β form: metastable. * Trihemihydrate, NaOH·3.5: from +5.4 °C (32.5%) to +15.38 °C (38.8%) and then to +5.0 °C (45.7%). * Trihydrate, NaOH·3: metastable. * Dihydrate, NaOH·2: from +5.0 °C (45.7%) to +12.3 °C (51%).P. R. Siemens, William F. Giauque (1969): "Entropies of the hydrates of sodium hydroxide. II. Low-temperature heat capacities and heats of fusion of NaOH·2H2O and NaOH·3.5H2O". ''Journal of Physical Chemistry'', volume 73, issue 1, pages 149–157. * Monohydrate, NaOH·: from +12.3 °C (51%) to 65.10 °C (69%) then to 62.63 °C (73.1%).L. E. Murch, W. F. Giauque (1962): "The thermodynamic properties of sodium hydroxide and its monohydrate. Heat capacities to low temperatures. Heats of solution". ''Journal of Physical Chemistry'', volume 66, issue 10, pages 2052–2059. Early reports refer to hydrates with ''n'' = 0.5 or ''n'' = 2/3, but later careful investigations failed to confirm their existence. The only hydrates with stable melting points are NaOH· (65.10 °C) and NaOH·3.5 (15.38 °C). The other hydrates, except the metastable ones NaOH·3 and NaOH·4 (β) can be crystallized from solutions of the proper composition, as listed above. However, solutions of NaOH can be easily supercooled by many degrees, which allows the formation of hydrates (including the metastable ones) from solutions with different concentrations. For example, when a solution of NaOH and water with 1:2 mole ratio (52.6% NaOH by mass) is cooled, the monohydrate normally starts to crystallize (at about 22 °C) before the dihydrate. However, the solution can easily be supercooled down to −15 °C, at which point it may quickly crystallize as the dihydrate. When heated, the solid dihydrate might melt directly into a solution at 13.35 °C; however, once the temperature exceeds 12.58 °C. it often decomposes into solid monohydrate and a liquid solution. Even the ''n'' = 3.5 hydrate is difficult to crystallize, because the solution supercools so much that other hydrates become more stable. A hot water solution containing 73.1% (mass) of NaOH is an eutectic that solidifies at about 62.63 °C as an intimate mix of anhydrous and monohydrate crystals.G. E. Brodale and W. F. Giauque(1962): "The freezing point-solubility curve of aqueous sodium hydroxide in the region near the anhydrous-monohydrate eutectic". ''Journal of Physical Chemistry'', volume 66, issue 10, pages 2051–2051. A second stable eutectic composition is 45.4% (mass) of NaOH, that solidifies at about 4.9 °C into a mixture of crystals of the dihydrate and of the 3.5-hydrate. The third stable eutectic has 18.4% (mass) of NaOH. It solidifies at about −28.7 °C as a mixture of water ice and the heptahydrate NaOH·7.M. Conde Engineering:
Solid-Liquid Equilibrium (SLE) and Vapour-Liquid Equilibrium (VLE) of Aqueous NaOH
. Online report, accessed on 2017-04-29.
When solutions with less than 18.4% NaOH are cooled, water
ice Ice is into a state. Depending on the presence of such as particles of soil or bubbles of air, it can appear transparent or a more or less bluish-white color. In the , ice is abundant and occurs naturally from as close to the Sun as to ...

ice
crystallizes first, leaving the NaOH in solution. The α form of the tetrahydrate has density 1.33 g/cm3. It melts congruously at 7.55 °C into a liquid with 35.7% NaOH and density 1.392 g/cm3, and therefore floats on it like ice on water. However, at about 4.9 °C it may instead melt incongruously into a mixture of solid NaOH·3.5 and a liquid solution. The β form of the tetrahydrate is metastable, and often transforms spontaneously to the α form when cooled below −20 °C. Once initiated, the exothermic transformation is complete in a few minutes, with a 6.5% increase in volume of the solid. The β form can be crystallized from supercooled solutions at −26 °C, and melts partially at −1.83 °C. The "sodium hydroxide" of commerce is often the monohydrate (density 1.829 g/cm3). Physical data in technical literature may refer to this form, rather than the anhydrous compound.


Crystal structure

NaOH and its monohydrate form orthorhombic crystals with the space groups Cmcm ( oS8) and Pbca (oP24), respectively. The monohydrate cell dimensions are a = 1.1825, b = 0.6213, c = 0.6069 nm. The atoms are arranged in a hydrargillite-like layer structure /O Na O O Na O/... Each sodium atom is surrounded by six oxygen atoms, three each from hydroxyl anions and three from water molecules. The hydrogen atoms of the hydroxyls form strong bonds with oxygen atoms within each O layer. Adjacent O layers are held together by
hydrogen bond A hydrogen bond (or H-bond) is a primarily Electrostatics, electrostatic force of attraction between a hydrogen Hydrogen is the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of ...

hydrogen bond
s between water molecules.


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 Hydrochloric acid +(aq) Cl−(aq) or H3O+ Cl− also known as muriatic acid, is an of ( ). It is a colorless solution with a distinctive smell. It is classified as a . It is a component of the in the digestive systems of most animal spec ...

hydrochloric acid
,
sodium chloride Sodium chloride , commonly known as salt (although sea salt also contains other chemical salt (chemistry), salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With Molar mass, molar ...
is formed: : In general, such neutralization reactions are represented by one simple net ionic equation: : This type of reaction with a strong acid releases heat, and hence is
exothermic In thermodynamics Thermodynamics is a branch of physics that deals with heat, Work (thermodynamics), work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these qu ...
. Such
acid–base reaction An acid–base reaction is a chemical reaction A chemical reaction is a process that leads to the IUPAC nomenclature for organic transformations, chemical transformation of one set of chemical substances to another. Classically, chemical react ...
s can also be used for
titration Titration (also known as titrimetry and volumetric analysis) is a common laboratory method of quantitative chemical analysis Analytical chemistry studies and uses instruments and methods used to separate, identify, and quantify matter. In pra ...

titration
s. However, sodium hydroxide is not used as a
primary standard A primary standard in metrology 290px, alt=Man in white standing in front of a large machine, A scientist stands in front of the Microarcsecond Metrology (MAM) testbed. Metrology is the scientific study of measurement ' Measurement is the numb ...
because it is
hygroscopic Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption (chemistry), absorption or adsorption from the surrounding Natural environment, environment, which is usually at normal or room temperature. If water m ...
and absorbs
carbon dioxide Carbon dioxide (chemical formula A chemical formula is a way of presenting information about the chemical proportions of atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is ...

carbon dioxide
from air.


Reaction with acidic oxides

Sodium hydroxide also reacts with
acidic oxides Acidic oxides, or acid anhydride, are oxides that react with water to form an acid, or with a base to form a salt. They are oxides of either nonmetals or of metals in high oxidation states. Their chemistry can be systematically understood by taking ...

acidic oxides
, such as
sulfur dioxide Sulfur dioxide (-recommended spelling) or sulphur dioxide (traditional ) is the with the formula . It is a responsible for the smell of burnt es. It is released naturally by and is produced as a by-product of extraction and the burning of ...
. Such reactions are often used to "
scrub Scrub(s) may refer to: * Scrub, low shrub and grass characteristic of Shrubland, scrubland * Scrubs (clothing), worn by medical staff * Scrubs (TV series), ''Scrubs'' (TV series), an American television program * Scrubs (occupation), also called " ...
" harmful acidic gases (like SO2 and H2S) produced in the burning of coal and thus prevent their release into the atmosphere. For example, :


Reaction with metals and oxides

Glass reacts slowly with aqueous sodium hydroxide solutions at ambient temperatures to form soluble
silicate In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds composed of atoms, ...
s. Because of this, glass joints and
stopcock A stopcock is a form of valve used to control the flow of a liquid A liquid is a nearly incompressible fluid In physics, a fluid is a substance that continually Deformation (mechanics), deforms (flows) under an applied shear stress, or ex ...

stopcock
s exposed to sodium hydroxide have a tendency to "freeze".
Flask Flask may refer to: Container * Hip flask, a small container used to carry a small amount of liquid * Laboratory flask, laboratory glassware for holding larger volumes than simple test tubes ** Erlenmeyer flask, a widely used type of laboratory ...
s and glass-lined
chemical reactor A chemical reactor is an enclosed volume in which a chemical reaction A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Classically, chemical A chemical substance is a fo ...
s are damaged by long exposure to hot sodium hydroxide, which also frosts the glass. Sodium hydroxide does not attack
iron Iron () is a with Fe (from la, ) and 26. It is a that belongs to the and of the . It is, on , right in front of (32.1% and 30.1%, respectively), forming much of Earth's and . It is the fourth most common . In its metallic state, iron ...

iron
at room temperatures, since iron does not have
amphoteric In chemistry, an amphoteric compound is a molecule or ion that can react both as an acid An acid is a molecule or ion An ion () is a particle In the Outline of physical science, physical sciences, a particle (or corpuscule in older ...

amphoteric
properties (i.e., it only dissolves in acid, not base). Nevertheless, at high temperatures (e.g. above 500 °C), iron can react
endothermic In thermochemistry Thermochemistry is the study of the heat energy which is associated with chemical reactions and/or physical transformations. A reaction may release or absorb energy, and a phase change may do the same, such as in melting and bo ...
ally with sodium hydroxide to form
iron(III) oxide Iron(III) oxide or ferric oxide is the inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. However, the distinction is ...
,
sodium Sodium is a with the  Na (from Latin ''natrium'') and  11. It is a soft, silvery-white, highly reactive . Sodium is an , being in of the periodic table. Its only stable is 23Na. The free metal does not occur in nature, and must be ...

sodium
metal, and
hydrogen Hydrogen is the chemical element with the Symbol (chemistry), symbol H and atomic number 1. Hydrogen is the lightest element. At standard temperature and pressure, standard conditions hydrogen is a gas of diatomic molecules having the che ...

hydrogen
gas. This is due to the lower
enthalpy of formationThe standard enthalpy of formation or standard heat of formation of a compound is the change of enthalpy Enthalpy is a property of a thermodynamic system A thermodynamic system is a body of matter and/or radiation, confined in space by walls, wi ...
of iron(III) oxide (−824.2 kJ/mol) compared to sodium hydroxide (-500 kJ/mol) and positive entropy change of reaction, which imply spontaneity at high temperatures (ΔST>ΔH, ΔG<0) and non-spontaneity at low temperatures (ΔST<ΔH, ΔG>0). Consider the following reaction between molten sodium hydroxide and finely divided iron filings: : A few
transition metal In chemistry, the term transition metal (or transition element) has three possible definitions: * The IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations tha ...
s, however, may react vigorously with sodium hydroxide under milder conditions. In 1986, an aluminium road tanker in the UK was mistakenly used to transport 25% sodium hydroxide solution, 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: :


Precipitant

Unlike sodium hydroxide, which is soluble, the hydroxides of most transition metals are insoluble, and therefore sodium hydroxide can be used to
precipitate Precipitation is the process of conversion of a chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All ever ...
transition metal hydroxides. The following colours are observed: * Copper - blue * Iron(II) - green * Iron(III) - yellow / brown Zinc and lead salts dissolve in excess sodium hydroxide to give a clear solution of Na2ZnO2 or Na2PbO2.
Aluminium hydroxide Aluminium hydroxide, Al(OH)3, is found in nature as the mineral gibbsite (also known as hydrargillite) and its three much rarer Polymorphism (materials science), polymorphs: bayerite, doyleite, and nordstrandite. Aluminium hydroxide is Amphoteri ...

Aluminium hydroxide
is used as a gelatinous flocculant to filter out particulate matter in
water treatment Water treatment is any process that improves the quality Quality may refer to: Concepts *Quality (business), the ''non-inferiority'' or ''superiority'' of something *Quality (philosophy), an attribute or a property *Quality (physics), in respo ...

water treatment
. Aluminium hydroxide is prepared at the treatment plant from
aluminium sulfate Aluminium sulfate is a chemical compound with the formula Al2 (SO4)3. It is soluble in water and is mainly used as a coagulating agent (promoting particle collision by neutralizing charge) in the purification of drinking water and wastewater ...

aluminium sulfate
by reacting it with sodium hydroxide or bicarbonate. : :


Saponification

Sodium hydroxide can be used for the base-driven
hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution Substitution may refer to: Arts and media *Chord substitution, in music, swapping one chord for ...

hydrolysis
of
ester An ester is a derived from an (organic or inorganic) in which at least one –OH group is replaced by an –O– () group, as in the substitution reaction of a and an . s are s of ; they are important in biology, being one of the main classe ...

ester
s (as in
saponification Saponification is a process that involves the conversion of fat, oil, or lipid, into soap and alcohol by the action of aqueous alkali (e.g. Sodium hydroxide, NaOH). Soaps are salts of fatty acids, which in turn are carboxylic acids with long carbon ...

saponification
),
amide In organic chemistry, an amide, also known as an organic amide or a carboxamide, is a chemical compound, compound with the general formula RC(=O)NR′R″, where R, R', and R″ represent organic compound, organic functional group, groups or ...

amide
s and
alkyl halide The haloalkanes'' known as halogenoalkanes or alkyl halides) are alkane In , an alkane, or paraffin (a historical that also has ), is an . In other words, an alkane consists of and atoms arranged in a structure in which all the s are . ...
s. However, the limited solubility of sodium hydroxide in organic solvents means that the more
soluble Solubility is the property of a solid, liquid or gaseous chemical substance called ''solution, solute'' to dissolve in a solid, liquid or gaseous solvent. The solubility of a substance fundamentally depends on the Physical property, physical an ...
potassium hydroxide Potassium hydroxide is an inorganic compound In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the ch ...

potassium hydroxide
(KOH) is often preferred. Touching a sodium hydroxide solution with bare hands, while not recommended, produces a slippery feeling. This happens because oils on the skin such as
sebum A sebaceous gland is a microscopic exocrine Exocrine glands are gland In animals, a gland is a group of cells in an animal's body that synthesizes substances (such as hormone A hormone (from the Greek participle , "setting in motion") is a ...

sebum
are converted to soap. Despite solubility in propylene glycol it is unlikely to replace water in saponification due to propylene glycol's primary reaction with fat before reaction between sodium hydroxide and fat.


Production

Sodium hydroxide is industrially produced as a 50% solution by variations of the electrolytic
chloralkali process The chloralkali process (also chlor-alkali and chlor alkali In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ions: their compo ...
.
Chlorine gas Chlorine is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural scien ...
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 A prill is a small aggregate or globule of a material, most often a dry sphere, formed from a melted liquid. Prilled is a term used in mining Mining is the extraction of valuable minerals or other geological materials from the Earth, usually f ...
s, and cast blocks. In 2004, world production was estimated at 60 million dry tonnes of sodium hydroxide, and demand was estimated at 51 million tonnes. In 1998, total world production was around 45 million
tonne The tonne ( or ; symbol: t) is a metric unit of mass equal to 1,000 kilogram The kilogram (also kilogramme) is the base unit of mass Mass is the physical quantity, quantity of ''matter'' in a physical body. It is also a meas ...
s. North America and Asia each contributed around 14 million tonnes, while Europe produced around 10 million tonnes. In the United States, the major producer of sodium hydroxide is Olin, which has annual production around 5.7 million
tonne The tonne ( or ; symbol: t) is a metric unit of mass equal to 1,000 kilogram The kilogram (also kilogramme) is the base unit of mass Mass is the physical quantity, quantity of ''matter'' in a physical body. It is also a meas ...
s from sites at Freeport, Texas, and
Plaquemine Plaquemine is a city in and the parish seat of Iberville Parish, Louisiana, Iberville Parish, Louisiana, United States. The population was 7,119 at the 2010 United States Census, 2010 census. It is part of the Baton Rouge, Louisiana, Baton Rouge B ...

Plaquemine
, Louisiana, St Gabriel, Louisiana, McIntosh, Alabama, Charleston, Tennessee, Niagara Falls, New York, and Becancour, Canada. Other major US producers include Oxychem, Westlake, Shintek and
Formosa , t2 = , s2 = , l2 = beautiful island , bpmf2 = ㄈㄨˊ ㄦˇ ㄇㄛˊ ㄕㄚ , w2 = Fu²-êr³-mo²-sha¹ , p2 = Fúĕrmóshā , tp2 = Fúĕrmósha , mps2 = Fúĕrmóshā , gr2 = Fwu'eelmosha , poj = Tâi-oân , tl = Tâi-uân , h = Thòi-và ...
. All of these companies use the
chloralkali process The chloralkali process (also chlor-alkali and chlor alkali In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ions: their compo ...
.''Kirk-Othmer Encyclopedia of Chemical Technology''
5th edition, John Wiley & Sons.
Historically, sodium hydroxide was produced by treating
sodium carbonate Sodium carbonate, ·10, (also known as Natrium Carbonate, washing soda, soda ash and soda crystals) is the inorganic compound with the formula Na2CO3 and its various hydrates. All forms are white, odourless, water-soluble salts that yield modera ...

sodium carbonate
with
calcium hydroxide Calcium hydroxide (traditionally called slaked lime) is an inorganic compound with the chemical formula calcium, Ca(Hydroxide, OH)2. It is a colorless crystal or white powder and is produced when quicklime (calcium oxide) is mixed or slaking (ge ...

calcium hydroxide
in a
metathesis reaction Metathesis may refer to: Changes of vocal properties * Metathesis (linguistics) Metathesis (; from Greek , from "I put in a different order"; Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic bran ...
which takes advantage of the fact that sodium hydroxide is soluble, while calcium carbonate is not. This process was called causticizing. : This process was superseded by the
Solvay process The Solvay process or ammonia-soda process is the major industrial process for the production of (soda ash, Na2CO3). The ammonia-soda process was developed into its modern form by the Belgian chemist during the 1860s. The ingredients for this are ...

Solvay process
in the late 19th century, which was in turn supplanted by the
chloralkali process The chloralkali process (also chlor-alkali and chlor alkali In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ions: their compo ...
which is in 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. : This reaction is commonly used for demonstrating 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.


Uses

Sodium hydroxide is a popular strong
base Base or BASE may refer to: Brands and enterprises * Base (mobile telephony provider), a Belgian mobile telecommunications operator *Base CRM Base CRM (originally Future Simple or PipeJump) is an enterprise software company based in Mountain Vie ...
used in industry. Sodium hydroxide is used in the manufacture of sodium salts and detergents, pH regulation, and organic synthesis. In bulk, it is most often handled as an
aqueous solution An aqueous solution is a solution Solution may refer to: * Solution (chemistry) Image:SaltInWaterSolutionLiquid.jpg, upMaking a saline water solution by dissolving Salt, table salt (sodium chloride, NaCl) in water. The salt is the solute an ...
, since solutions are cheaper and easier to handle. Sodium hydroxide is used in many scenarios where it is desirable to increase the
alkalinity Alkalinity (from Arabic "''al-qalī''") is the capacity of water to resist acidification. It should not be confused with basicity In chemistry, there are three definitions in common use of the word base, known as Arrhenius bases, Brønste ...
of a mixture, or to neutralize acids. For example, in the petroleum industry, sodium hydroxide is used as an additive in
drilling mud In geotechnical engineering, drilling fluid, also called drilling mud, is used to aid the drilling of boreholes into the earth. Often used while drilling oil well, oil and natural gas wells and on exploration drilling rigs, drilling fluids a ...
to increase
alkalinity Alkalinity (from Arabic "''al-qalī''") is the capacity of water to resist acidification. It should not be confused with basicity In chemistry, there are three definitions in common use of the word base, known as Arrhenius bases, Brønste ...
in
bentonite Bentonite () is an Absorption (chemistry), absorbent swelling clay consisting mostly of montmorillonite. It usually forms from weathering of volcanic ash in seawater, which converts the volcanic glass present in the ash to clay minerals. Benton ...

bentonite
mud systems, to increase the mud
viscosity The viscosity of a is a measure of its to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, has a higher viscosity than . Viscosity can be conceptualized as quantifying the inter ...

viscosity
, and to neutralize any
acid gasAcid gas is a particular typology of natural gas Natural gas (also called fossil gas; sometimes just gas) is a naturally occurring hydrocarbon gas mixture consisting primarily of methane, but commonly including varying amounts of other higher a ...
(such as
hydrogen sulfide Hydrogen sulfide is a chemical compound A chemical compound is a chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by havi ...

hydrogen sulfide
and
carbon dioxide Carbon dioxide (chemical formula A chemical formula is a way of presenting information about the chemical proportions of atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is ...

carbon dioxide
) which may be encountered in the
geological formation A geological formation, or formation, is a body of rock having a consistent set of physical characteristics (lithology) that distinguish it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exposed in a ...
as drilling progresses. Another use is in Salt spray testing where pH needs to be regulated. Sodium hydroxide is used with hydrochloric acid to balance pH. The resultant salt, NaCl, is the corrosive agent used in the standard neutral pH salt spray test. Poor quality
crude oil Petroleum, also known as crude oil and oil, is a naturally occurring, yellowish-black liquid A liquid is a nearly incompressible In fluid mechanics Fluid mechanics is the branch of physics concerned with the mechanics Mech ...
can be treated with sodium hydroxide to remove
sulfur Sulfur (in nontechnical British English: sulphur) is a chemical element In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: th ...

sulfur
ous impurities in a process known as ''caustic washing''. As above, sodium hydroxide reacts with weak acids such as
hydrogen sulfide Hydrogen sulfide is a chemical compound A chemical compound is a chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by havi ...

hydrogen sulfide
and
mercaptans A thiol () or thiol derivative is any organosulfur compound Organosulfur compounds are organic compounds that contain sulfur. They are often associated with foul odors, but many of the sweetest compounds known are organosulfur derivatives, e.g., sa ...
to yield 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 Trafigura Group Pte. Ltd. is a Singaporean multinational commodity trading company founded in 1993 that trades in base metals and energy. It is legally registered and headquartered in Singapore Singapore (), officially the Republic of ...
used the process and then dumped the waste in Ivory Coast. Other common uses of sodium hydroxide include: * It is used for making soaps and detergents. Sodium hydroxide is used for hard bar soap while
potassium hydroxide Potassium hydroxide is an inorganic compound In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the ch ...

potassium hydroxide
is used for liquid soaps.sodium hydroxide is used more often than
potassium hydroxide Potassium hydroxide is an inorganic compound In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the ch ...

potassium hydroxide
because it is cheaper and a smaller quantity is needed. * It is used as drain cleaners that contain sodium hydroxide convert fats and grease that can clog pipes into soap, which dissolves in water. ''(see Sodium hydroxide#Cleaning agent, cleaning agent)'' * It is used for making artificial textile fibres (such as Rayon). * It is used in the manufacture of
paper Paper is a thin sheet material Material is a substance Substance may refer to: * Substance (Jainism), a term in Jain ontology to denote the base or owner of attributes * Chemical substance, a material with a definite chemical composition * ...

paper
. Around 56% of sodium hydroxide produced is used by industry, 25% of which is used in the paper industry. ''(see Sodium hydroxide#Chemical pulping, chemical pulping)'' * It is used in purifying Bauxite, bauxite ore from which Aluminium, aluminium metal is extracted. This is known as Bayer process. ''(see Sodium hydroxide#Dissolving amphoteric metals and compounds, dissolving amphoteric metals and compounds)'' * It is used in de-greasing metals, oil refining, and making Dye, dyes and Bleach, bleaches. *It is used in water treatment plants for pH regulation. *It is used to treat bagels and pretzel dough, giving the distinctive shiny finish.


Chemical pulping

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 fibers 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, 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,Ayres, Chris (27 February 2010
Clean green finish that sends a loved one down the drain
Times Online. Retrieved 2013-02-20.
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
and the only solid that remains are bone hulls, which could be crushed between one's fingertips.Roach, Mary (2004). ''Stiff: The Curious Lives of Human Cadavers'', New York: W.W. Norton & Company. . Sodium hydroxide is frequently used in the process of decomposing roadkill dumped in landfills by animal disposal contractors. Due to its availability and low cost, it has been used by criminals to dispose of corpses. Italian serial killer Leonarda Cianciulli used this chemical to turn dead bodies into soap. In Mexico, a man who worked for drug cartels admitted disposing of over 300 bodies with it. Sodium hydroxide is a dangerous chemical due to its ability to hydrolyze protein. If a dilute solution is spilled on the skin, burns may result if the area is not washed thoroughly and for several minutes with running water. Splashes in the eye can be more serious and can lead to blindness.


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 Hydrogen is the chemical element with the Symbol (chemistry), symbol H and atomic number 1. Hydrogen is the lightest element. At standard temperature and pressure, standard conditions hydrogen is a gas of diatomic molecules having the che ...

hydrogen
gas and sodium aluminate. In this reaction, sodium hydroxide acts as an agent to make the solution alkaline, which aluminium can dissolve in. : Sodium aluminate is an inorganic chemical that is used as an effective source of
Aluminium hydroxide Aluminium hydroxide, Al(OH)3, is found in nature as the mineral gibbsite (also known as hydrargillite) and its three much rarer Polymorphism (materials science), polymorphs: bayerite, doyleite, and nordstrandite. Aluminium hydroxide is Amphoteri ...

Aluminium hydroxide
for many industrial and technical applications. Pure sodium aluminate (anhydrous) is a white crystalline solid having a formula variously given as , (hydrated), , or . Formation of sodium tetrahydroxoaluminate(III) or hydrated sodium aluminate is given by: : 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 In chemistry, an amphoteric compound is a molecule or ion that can react both as an acid An acid is a molecule or ion An ion () is a particle In the Outline of physical science, physical sciences, a particle (or corpuscule in older ...

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. 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 Saponification is a process that involves the conversion of fat, oil, or lipid, into soap and alcohol by the action of aqueous alkali (e.g. Sodium hydroxide, NaOH). Soaps are salts of fatty acids, which in turn are carboxylic acids with long carbon ...

saponification
). 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 A substance is anhydrous if it contains no water Water (chemical formula H2O) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the flui ...
sodium hydroxide, because combined with water the fat would turn into
soap Soap is a of a used in a variety of cleansing and lubricating products. In a domestic setting, soaps are s usually used for , , and other types of . In industrial settings, soaps are used as s, components of some s, and precursors to s. Wh ...

soap
, which would be tainted with
methanol Methanol, also known as methyl alcohol, amongst other names, is a chemical A chemical substance is a form of matter having constant chemical composition and characteristic properties. Some references add that chemical substance cannot be se ...

methanol
. NaOH is used more often than
potassium hydroxide Potassium hydroxide is an inorganic compound In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the ch ...

potassium hydroxide
because it is cheaper and a smaller quantity is needed. Due to production costs, NaOH, which is produced using common salt is cheaper than potassium hydroxide.


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. Olives are often soaked in sodium hydroxide for softening; Pretzels and German lye rolls 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 Sodium carbonate, ·10, (also known as Natrium Carbonate, washing soda, soda ash and soda crystals) is the inorganic compound with the formula Na2CO3 and its various hydrates. All forms are white, odourless, water-soluble salts that yield modera ...

sodium carbonate
is often used in place of sodium hydroxide. It is known as E number E524. Specific foods processed with sodium hydroxide include: *German pretzels are poached in a boiling
sodium carbonate Sodium carbonate, ·10, (also known as Natrium Carbonate, washing soda, soda ash and soda crystals) is the inorganic compound with the formula Na2CO3 and its various hydrates. All forms are white, odourless, water-soluble salts that yield modera ...

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 A lye is a metal hydroxide traditionally obtained by leaching wood ashes, or a strong alkali In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of at ...
-water but are commonly mistaken for containing egg. *One variety of zongzi uses lye water to impart a sweet flavor. *Sodium hydroxide is also the chemical that causes gelling of egg whites in the production of Century eggs. *Some methods of preparing olives involve subjecting them to a lye-based brine. *The Filipino dessert (''kakanin'') called ''kutsinta'' uses a small quantity 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. *The Norway, Norwegian dish known as lutefisk (from ''lutfisk'', "lye fish"). *Bagels are often boiled in a lye solution before baking, contributing to their shiny crust. *Hominy is dried maize (corn) kernels reconstituted by soaking in
lye A lye is a metal hydroxide traditionally obtained by leaching wood ashes, or a strong alkali In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of at ...
-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. Hominy is used to create Masa, a popular flour used in Mexican cuisine to make Corn tortillas and tamales. Nixtamal is similar, but uses
calcium hydroxide Calcium hydroxide (traditionally called slaked lime) is an inorganic compound with the chemical formula calcium, Ca(Hydroxide, OH)2. It is a colorless crystal or white powder and is produced when quicklime (calcium oxide) is mixed or slaking (ge ...

calcium hydroxide
instead of sodium hydroxide.


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, fats and
protein Proteins are large s and s that comprise one or more long chains of . Proteins perform a vast array of functions within organisms, including , , , providing and , and from one location to another. Proteins differ from one another primarily ...

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 A detergent is a surfactant Surfactants are compounds that lower the surface tension (or interfacial tension) between two liquids, between a gas and a liquid, or between a liquid and a solid. Surfactants may act as detergents, wetting ...
s. Parts washer detergents based on sodium hydroxide are some of the most aggressive parts washer cleaning chemicals. The sodium hydroxide-based detergents 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 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. 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 relaxers 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.


Water treatment

Sodium hydroxide is sometimes used during water purification to raise the pH of water supplies. Increased pH makes the water less corrosive to plumbing and reduces the amount of lead, copper and other toxic metals that can dissolve into drinking water.


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. Today, carbon monoxide poisoning can be detected by CO oximetry.


In cement mixes, mortars, concrete, grouts

Sodium hydroxide is used in some cement mix plasticisers. This helps homogenise cement mixes, preventing segregation of sands and cement, decreases the amount of water required in a mix and increases workability of the cement product, be it mortar, render or concrete.


Experimental


Flavonoids

See: Sodium hydroxide test for flavonoids


Summer-winter heat storage

EMPA researchers are experimenting with concentrated sodium hydroxide (NaOH) as the thermal storage or seasonal reservoir medium for domestic HVAC, space-heating. If water is added to solid or concentrated sodium hydroxide (NaOH), heat is released. The dilution is Exothermic process, exothermic – chemical energy is released in the form of heat. Conversely, by applying heat energy into a dilute sodium hydroxide solution the water will evaporate so that the solution becomes more concentrated and thus stores the supplied heat as Endothermic process, latent chemical energy.


Neutron Moderator

Seaborg Technologies is working on a reactor design in which NaOH is used as a neutron moderator.


Safety

Like other corrosive acids and
alkali In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds composed of ato ...

alkali
s, drops of sodium hydroxide solutions can readily decompose proteins and lipids in Tissue (biology), living tissues via Hydrolysis#Esters and amides, amide hydrolysis and ester hydrolysis, which consequently cause
chemical burn A chemical burn occurs when living tissue is exposed to a corrosive substance (such as a strong acid An acid is a molecule or ion capable of donating a proton (hydrogen ion H+) (a Brønsted–Lowry acid–base theory, Brønsted–Lowry acid ...
s and may induce permanent blindness upon contact with eyes. Solid alkali can also express its corrosive nature if there is water, such as water vapor. Thus, protective equipment, like rubber gloves, safety clothing and eye protection, should always be used when handling this chemical or its solutions. 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. 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. Sodium hydroxide is also mildly corrosive to glass, which can cause damage to glazing (window), glazing or cause ground glass joints to bind. Sodium hydroxide is corrosive to several metals, like aluminium which reacts with the alkali to produce flammable
hydrogen Hydrogen is the chemical element with the Symbol (chemistry), symbol H and atomic number 1. Hydrogen is the lightest element. At standard temperature and pressure, standard conditions hydrogen is a gas of diatomic molecules having the che ...

hydrogen
gas on contact: : : :


Storage

Careful storage is needed when handling sodium hydroxide for use, especially bulk volumes. Following proper NaOH storage guidelines and maintaining worker/environment safety is always recommended given the chemical's burn hazard. Sodium hydroxide is often stored in bottles for small-scale laboratory use, within intermediate bulk containers (medium volume containers) for cargo handling and transport, or within large stationary storage tanks with volumes up to 100,000 gallons for manufacturing or waste water plants with extensive NaOH use. Common materials that are compatible with sodium hydroxide and often utilized for NaOH storage include: polyethylene (HDPE, usual, Cross-linked polyethylene, XLPE, less common), carbon steel, polyvinyl chloride (PVC), stainless steel, and fiberglass reinforced plastic (FRP, with a resistant liner). Sodium hydroxide must be stored in airtight containers to preserve its Equivalent concentration, normality as it will absorb water from the atmosphere.


History

Sodium hydroxide was first prepared by soap makers.Thorpe, Thomas Edward, ed., ''A Dictionary of Applied Chemistry'' (London, England: Longmans, Green, and Co., 1913), vol. 5

/ref> A procedure for making sodium hydroxide appeared as part of a recipe for making soap in an Arab book of the late 13th century: (Inventions from the Various Industrial Arts), which was compiled by al-Muzaffar Yusuf ibn 'Umar ibn 'Ali ibn Rasul (d. 1295), a king of Yemen. The recipe called for passing water repeatedly through a mixture of ''
alkali In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds composed of ato ...

alkali
'' (Arabic: , where is ash from Glasswort, saltwort plants, which are rich in sodium; hence ''alkali'' was impure
sodium carbonate Sodium carbonate, ·10, (also known as Natrium Carbonate, washing soda, soda ash and soda crystals) is the inorganic compound with the formula Na2CO3 and its various hydrates. All forms are white, odourless, water-soluble salts that yield modera ...

sodium carbonate
) and quicklime (calcium oxide, CaO), whereby a solution of sodium hydroxide was obtained. European soap makers also followed this recipe. When in 1791 the French chemist and surgeon Nicolas Leblanc (1742–1806) patented a Leblanc process, process for mass-producing sodium carbonate, natural "soda ash" (impure sodium carbonate that was obtained from the ashes of plants that are rich in sodium) was replaced by this artificial version. However, by the 20th century, the Chloralkali process, electrolysis of sodium chloride had become the primary method for producing sodium hydroxide.O'Brien, Thomas F.; Bommaraju, Tilak V. and Hine, Fumio (2005) ''Handbook of Chlor-Alkali Technology'', vol. 1. Berlin, Germany: Springer. Chapter 2: History of the Chlor-Alkali Industry, p. 34.


See also

*pH, Acid and base *HAZMAT Class 8 Corrosive Substances *List of cleaning agents


References


Bibliography

*


External links


International Chemical Safety Card 0360
*Euro Chlor-How is chlorine made
Chlorine OnlineCDC – Sodium Hydroxide – NIOSH Workplace Safety and Health Topic
*Data sheets
Sodium Hydroxide MSDS

Certified Lye MSDS

Hill Brothers MSDS
*[https://web.archive.org/web/20150508191719/http://www.inclusive-science-engineering.com/inorganic-chemical-caustic-soda-production-process-description-and-flowsheet/ Caustic soda production in continuous causticising plant by lime soda process] {{DEFAULTSORT:Sodium Hydroxide Chemical engineering Cleaning products Deliquescent substances Desiccants Household chemicals Hydroxides Inorganic compounds Photographic chemicals Sodium compounds E-number additives Food acidity regulators