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In
chemistry Chemistry is the scientific Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity or awareness, of someone or something, such as facts A fact is an occurrence in the real world. T ...

chemistry
, an alkali (; from ar, القلوي ''al-qaly'' "ashes of the
saltwortSaltwort is a common name for various genera of flowering plants that thrive in salty environments, typically in coastal salt marshes and seashores. Including various matter such as: :*'' Salsola'' and related genera within subfamily '' Salsoloidea ...
") is a
basic BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming language In computer science Computer science deals with the theoretical foundations of information, algorithms and the ar ...
,
ionic Ionic or Ionian may refer to: Arts and entertainment * Ionic meter, a poetic metre in ancient Greek and Latin poetry * Ionian mode, a musical mode or a diatonic scale Places and peoples * Ionian, of or from Ionia, an ancient region in western An ...
salt Salt is a mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure fo ...
of an
alkali metal The alkali metals consist of the 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: their composition, structur ...
or an
alkaline earth metal The alkaline earth metals are six 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 n ...
. An alkali can also be defined as a base that dissolves in
water Water (chemical formula H2O) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known li ...

water
. A solution of a soluble base has a
pH
pH
greater than 7.0. The
adjective In linguistics Linguistics is the scientific study of language A language is a structured system of communication used by humans, including speech (spoken language), gestures (Signed language, sign language) and writing. Most langu ...
alkaline is commonly, and alkalescent less often, used in
English English usually refers to: * English language English is a West Germanic languages, West Germanic language first spoken in History of Anglo-Saxon England, early medieval England, which has eventually become the World language, leading lan ...

English
as a
synonym A synonym is a word, morpheme A morpheme is the smallest meaningful lexical item in a language. A morpheme is not a word. The difference between a morpheme and a word is that a morpheme bound and free morphemes, sometimes does not stand alone ...
for basic, especially for bases soluble in water. This broad use of the term is likely to have come about because alkalis were the first bases known to obey the Arrhenius definition of a base, and they are still among the most common bases.


Etymology

The word "alkali" is derived from Arabic ''al qalīy'' (or ''alkali''), meaning ''the calcined ashes'' (see
calcination Calcination refers to heating a solid to high temperatures in absence of air or oxygen, generally for the purpose of removing impurities or volatile substances. However, calcination is also used to mean a thermal treatment Thermal treatment is any ...
), referring to the original source of alkaline substances. A water-extract of burned plant ashes, called
potash Potash () includes various mined and manufactured salts 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: their composition, structu ...
and composed mostly of potassium carbonate, was mildly basic. After heating this substance 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
(''slaked lime''), a far more strongly basic substance known as ''caustic potash'' (
potassium hydroxide Potassium hydroxide is an inorganic compound 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: their composition, structure, properties, ...

potassium hydroxide
) was produced. Caustic potash was traditionally used in conjunction with animal fats to produce soft
soap Soap is a salt (chemistry), salt of a fatty acid used in a variety of cleansing and lubricating products. In a domestic setting, soaps are surfactants usually used for washing, bathing, and other types of housekeeping. In industrial settings, ...

soap
s, one of the caustic processes that rendered soaps from fats in 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
, one known since antiquity. Plant potash lent the name to the element
potassium Potassium 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: their composition, structure, properties, b ...

potassium
, which was first derived from caustic potash, and also gave potassium its chemical symbol K (from the German name Kalium), which ultimately derived from alkali.


Common properties of alkalis and bases

Alkalis are all Arrhenius bases, ones which form hydroxide ions (OH) when dissolved in water. Common properties of alkaline aqueous
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 and the water the solvent. In chemistry ...
s include: * Moderately concentrated solutions (over 10−3 M) have a pH of 7.1 or greater. This means that they will turn
phenolphthalein Phenolphthalein is a chemical compound with the chemical formula, formula carbon, C20hydrogen, H14oxygen, O4 and is often written as "HIn" or "phph" in shorthand notation. Phenolphthalein is often used as an indicator in acid–base titrations. For ...

phenolphthalein
from colorless to pink. * Concentrated solutions are
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 ...
(causing chemical burns). * Alkaline solutions are slippery or soapy to the touch, due to the
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
of the fatty substances on the surface of the skin. * Alkalis are normally
water-soluble In chemistry, solubility is ability of a chemical substance, substance, the solute, to form a solution (chemistry), solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a ...

water-soluble
, although some like
barium carbonate Barium carbonate 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 not clearly defin ...

barium carbonate
are only soluble when reacting with an acidic aqueous solution.


Difference between alkali and base

The terms "base" and "alkali" are often used interchangeably, particularly outside the context of
chemistry Chemistry is the scientific Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity or awareness, of someone or something, such as facts A fact is an occurrence in the real world. T ...

chemistry
and
chemical engineering Chemical engineering is a certain type of engineering Engineering is the use of scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, vehicles, and buildings. The discipline ...
. There are various more specific definitions for the concept of an alkali. Alkalis are usually defined as a subset of the bases. One of two subsets is commonly chosen. * A basic salt of an alkali metal or alkaline earth metal (This includes Mg(OH)2 but excludes NH3.) * Any base that is soluble in water and forms hydroxide ions or the solution of a base in water. (This includes Mg(OH)2 and NH3.) The second subset of bases is also called an " Arrhenius base".


Alkali salts

Alkali salts are soluble hydroxides of
alkali metals The alkali metals consist of the 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 ...
and
alkaline earth metals The alkaline earth metals are six 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: their composition, structure ...
, of which common examples are: *
Sodium hydroxide 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 chem ...

Sodium hydroxide
(NaOH) – often called "caustic soda" *
Potassium hydroxide Potassium hydroxide is an inorganic compound 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: their composition, structure, properties, ...

Potassium hydroxide
(KOH) – commonly called "caustic potash" *
Lye A lye is a metal hydroxideMetal hydroxides are hydroxides of metals. They are often strong base (chemistry), bases. They consist of hydroxide anions and metallic cations. Some metal hydroxides, such as alkali metal hydroxides, ionize completel ...
– generic term for either of two previous salts or their mixture *
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
(Ca(OH)2) – saturated solution known as "
limewater Limewater is the common name for a saturated aqueous solution of 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 ...

limewater
" *
Magnesium hydroxide Magnesium hydroxide is the inorganic compound with the chemical formula Mg(OH)2. It occurs in nature as the mineral brucite. It is a white solid with low solubility in water (). Magnesium hydroxide is a common component of antacids, such as milk ...
(Mg(OH)2) – an atypical alkali since it has low solubility in water (although the dissolved portion is considered a strong base due to complete dissociation of its ions)


Alkaline soil

Soils with pH values that are higher than 7.3 are usually defined as being alkaline. These soils can occur naturally, due to the presence of alkali salts. Although many plants do prefer slightly basic soil (including vegetables like
cabbage Cabbage, comprising several cultivars of ''Brassica oleracea ''Brassica oleracea'' is a plant species that includes many common foods as cultivars, including cabbage, broccoli, cauliflower, kale, Brussels sprouts, collard greens, Savoy cabba ...

cabbage
and fodder like buffalo grass), most plants prefer a mildly acidic soil (with pHs between 6.0 and 6.8), and
alkaline soil 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 ...
s can cause problems.


Alkali lakes

In alkali lakes (also called ''soda lakes''), evaporation concentrates the naturally occurring carbonate salts, giving rise to an alkalic and often saline lake. Examples of alkali lakes: * Alkali Lake,
Lake County, Oregon Lake County is one of the Oregon counties, 36 counties in the U.S. state of Oregon. As of the 2010 United States Census, 2010 census, the population was 7,895. Its county seat is Lakeview, Oregon, Lakeview. The county is named after the many lake ...
* Baldwin Lake,
San Bernardino County, California San Bernardino County, officially the County of San Bernardino, is a county A county is a geographical region of a country used for administrative or other purposesChambers Dictionary, L. Brookes (ed.), 2005, Chambers Harrap Publishers Ltd, ...
* Bear LakeDavis, Jim and Milligan, Mark (2011)
Why is Bear Lake so blue?
Public Information Series 96. Utah Geological Survey, Department of Natural Resources
on the Utah–Idaho border *
Lake Magadi Lake Magadi is the southernmost lake in the Kenyan Rift Valley The Great Rift Valley is part of an intra-continental ridge system that runs through Kenya from north to south. It is part of the Gregory Rift, the eastern branch of the East Afri ...

Lake Magadi
in Kenya *
Lake Turkana Lake Turkana (), formerly known as Lake Rudolf, is a lake in the Great Rift Valley, Kenya, Kenyan Rift Valley, in northern Kenya, with its far northern end crossing into Ethiopia. It is the world's largest permanent desert lake and the world's ...

Lake Turkana
in
Kenya ) , national_anthem = "Ee Mungu Nguvu Yetu "Ee Mungu Nguvu Yetu" (, ) is the national anthem of Kenya. History "Ee Mungu Nguvu Yetu"'s lyrics were originally written in Swahili language, Kiswahili, the national language of Kenya ...

Kenya
*
Mono Lake Mono Lake ( ) is a saline soda lake in Mono County, California, formed at least 760,000 years ago as a terminal lake in an endorheic basin. The lack of an outlet causes Hypersaline lake, high levels of salts to accumulate in the lake and make ...

Mono Lake
, near
Owens Valley Owens Valley (Numic Numic is a branch of the Uto-Aztecan languages, Uto-Aztecan language family. It includes seven languages spoken by Native Americans in the United States, Native American peoples traditionally living in the Great Basin, Colo ...
in
California California is a state State may refer to: Arts, entertainment, and media Literature * ''State Magazine'', a monthly magazine published by the U.S. Department of State * The State (newspaper), ''The State'' (newspaper), a daily newspaper i ...

California
* Redberry Lake, Saskatchewan *,
Lake County, Oregon Lake County is one of the Oregon counties, 36 counties in the U.S. state of Oregon. As of the 2010 United States Census, 2010 census, the population was 7,895. Its county seat is Lakeview, Oregon, Lakeview. The county is named after the many lake ...
* Tramping Lake, Saskatchewan


See also

*
Alkali metals The alkali metals consist of the 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 ...
*
Alkaline earth metals The alkaline earth metals are six 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: their composition, structure ...
*
Base (chemistry) In chemistry, there are three definitions in common use of the word base, known as Arrhenius bases, Brønsted bases and Lewis bases. All definitions agree that bases are substances which react with s as originally proposed by in the mid-18th ...


References

{{Authority control Inorganic chemistry