alkali

(ăl'kə-lī')

1. A carbonate or hydroxide of an alkali metal, the aqueous solution of which is bitter, slippery, caustic, and characteristically basic in reactions.
2. Any of various soluble mineral salts found in natural water and arid soils.
3. Alkali metal.
4. A substance having highly basic properties; a strong base.

[Middle English, alkaline substance from calcined plant ashes, from Medieval Latin, from Arabic al-qily, the ashes, lye, potash : al-, the + qily, ashes (from qalā, to fry, roast).]

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Any compound having highly basic properties, strong acrid taste, and ability to neutralize acids. Aqueous solutions of alkalies are high in hydroxyl ions, have a pH above 7, and turn litmus paper from red to blue. Caustic alkalies include sodium hydroxide (caustic soda), the sixth-largest-volume chemical produced in the United States, and potassium hydroxide. They are extremely destructive to human tissue; external burns should be washed with large amounts of water. The milder alkalies are the carbonates of the alkali metals; these include the industrially important sodium carbonate (soda ash) and potassium carbonate (potash), as well as the carbonates of lithium, rubidium, and cesium, and the volatile ammonium hydroxide. Sodium bicarbonate is a still milder alkaline material. See also Acid and base; pH.

About 50% of the caustic soda produced goes into making many chemical products, about 16% into pulp and paper, 6.5% each into aluminum, petroleum, and textiles (including rayon), with smaller percentages into soap and synthetic detergents, and cellophane. For soda ash, about 50% goes to react mainly with sand in making glass, 25% to making miscellaneous chemicals, 6.5% each to alkaline cleaners and pulp and paper, and a few percent to water treatment and other uses. See also Alkali metals; Electrochemical process; Hydroxide; Soap.

A compound that takes up hydrogen ions and so raises the pH of a solution; see also acid; buffers; salt.

An alkali is a substance that has a high pH when in solution and tends to neutralize acids. The amount of alkali available in the body to act as a buffer, moderating changes in pH, is called the alkali reserve or standard bicarbonate (because most of the alkali is in the form of bicarbonate ions). A high alkali reserve is particularly important for those involved in high-intensity activities lasting up to three minutes (e.g. 800 metre run). The bicarbonate ions help to neutralize lactic acid produced during anaerobic respiration. Some athletes boost their alkali reserve artificially by ingesting extra amounts of sodium bicarbonate. This can enhance performance for maximal effort activities of 1-7 minutes duration. When used in this way, sodium bicarbonate is called an alkalinizer. Alkalinizers have also been used by some athletes to avoid drug detection. By raising the pH, they reduce the excretion of metabolic by-products of some stimulant drugs, thereby masking them.

Although a high alkali reserve is beneficial, an abnormally high pH in the blood or tissue fluids (a condition called alkalosis) can be harmful. The excess alkali can make muscles overreact, causing them to go into cramp-like spasms. There are two forms of alkalosis. Respiratory alkalosis usually results from hyperventilation (heavy breathing) which reduces carbon dioxide levels in the body fluids. It can also occur at high altitudes where the air is thin and oxygen levels are low. Metabolic alkalosis often results from ingesting excessive amounts of alkalinizers, or from losing large amounts of acid (for example, by vomiting the acidic stomach contents). Compare acidosis.

[AL-kah-li] Alkalis counterbalance and neutralize acids. In cooking, the most common alkali used is bicarbonate of soda, commonly known as baking soda.

A substance which neutralizes, or is neutralized by, acid. Alkalis are generally oxides, hydroxides, or compounds such as ammonia which dissolve in water to form hydroxide ions. Alkalis have a pH of more than 7.

Any of the various chemically active bases such as the soluble salts of metals, e.g., the water-soluble salts of sodium and potassium which occur in constituents of concrete and mortar that may result in deleterious expansion.

A substance that has a high pH (pH > 7) when in solution and that tends to neutralize acids.

A bitter, caustic mineral often found in large beds in the desert. Alkalis are bases; two common examples are lye and ammonia.

Any one of a class of compounds such as sodium hydroxide that form salts with acids and soaps with fats; a base, or substance capable of neutralizing acids. Other properties include a bitter taste and the ability to turn litmus paper from red to blue. Alkalis play a vital role in maintaining the normal functioning of the body chemistry. See also acid–base balance, alkaline, base.

• a. disease — see selenium poisoning.
• a. reserve — the ability of the combined buffer systems of the blood to neutralize acid. The pH of the blood normally is slightly on the alkaline side, between 7.35 and 7.45. Since the principal buffer in the blood is bicarbonate, the alkali reserve is essentially represented by the plasma bicarbonate concentration. However, hemoglobin, phosphates and other bases also act as buffers. A lowered alkali reserve means a state of acidosis; increased reserve indicates alkalosis. Alkali reserve is measured by the combining power of carbon dioxide, which is the amount of carbon dioxide that can be bound as bicarbonate by the blood.

A strong water-soluble base. A chemical substance that, in aqueous solution, undergoes dissociation, resulting in the formation of hydroxyl (OH) ions.

• Substances, Particles, and Atomic Architecture - alkali: base that dissolves in water to give hydroxyl ions; soluble substance with pH over 7.0 that can neutralize acids

For other uses of the word "alkalis" see Alkali (disambiguation). "Alcali" also redirects here, for the place in Azerbaijan, see Alçalı.

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (June 2008)

In chemistry, an alkali ( /ˈælkəlaɪ/; from Arabic: al-qaly القلي, القالي ) is a basic, ionic salt of an alkali metal or alkaline earth metal element. Some authors also define an alkali as a base that dissolves in water. A solution of a soluble base has a pH greater than 7. The adjective alkaline is commonly used in English as a synonym for base, especially for soluble bases. 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 are still among the more common bases.

Contents 1 Etymology 2 Common properties 3 Difference between alkali and base 4 Salts 5 Alkaline soil 6 Alkali lakes 7 References

Etymology

The word "alkali" is derived from Arabic al qalīy (or al kali),^[1] meaning the calcined ashes (see calcination), referring to the original source of alkaline substances. A water-extract of burned plant ashes, called potash and composed mostly of potassium carbonate, was mildly basic. After heating this substance with calcium hydroxide (slaked lime), a far more strongly basic substance known as caustic potash (potassium hydroxide) was produced. Caustic potash was traditionally used in conjunction with animal fats to produce soft soaps, one of the caustic processes that rendered soaps from fats in the process of saponification, known since antiquity. Plant potash lent the name to the element potassium, which was first derived from caustic potash, and also gave potassium its chemical symbol K (cf German Kalium), which ultimately derives from alkali.

Common properties

Alkalis are all Arrhenius bases, which form hydroxide ions (OH^-) when dissolved in water. Common properties of alkaline aqueous solutions include:

• Moderately concentrated solutions (over 10⁻³ M) have a pH of 7.1 or greater. This means that they will turn phenolphthalein from colorless to pink.
• Concentrated solutions are caustic (causing chemical burns).
• Alkaline solutions are slippery or soapy to the touch, due to the saponification of the fatty acids on the surface of the skin.
• Alkalis are normally water soluble, although some like barium carbonate are only soluble when reacting with an acidic aqueous solution.
• Acids and alkalis are measured on a pH scale
• Turns Universal Indicator Blue-Dark Purple.

Difference between alkali and base

The terms "base" and "alkali" are often used interchangeably, particularly outside of a scientific context.

There are various definitions for alkali. Alkali is often defined as a subset of base. However, two subsets are commonly chosen.

• A basic salt of an alkali metal or alkaline earth metal^[2] (This includes Mg(OH)₂ but excludes NH₃.)
• Any base that is water-soluble and forms hydroxide ions^[3][4][5] or the solution of a base in water.^[6] (This excludes Mg(OH)₂ but includes NH₃.)

The second subset of base is also called an Arrhenius base.

Salts

Most basic salts are alkali salts, of which common examples are:

• sodium hydroxide (often called "caustic soda")
• potassium hydroxide (commonly called "caustic potash")
• lye (generic term, for either of the previous two, or even for a mixture)
• calcium carbonate (sometimes called "free lime" or "limewater")
• magnesium hydroxide is an example of 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

Soil with a pH value higher than 7.3 is normally referred to as alkaline. This soil property can occur naturally, due to the presence of alkali salts. Although some plants do prefer slightly basic soil (including vegetables like cabbage and fodder like buffalograss), most plants prefer a mildly acidic soil (pH between 6.0 and 6.8), and alkaline soils can cause problems.

Alkali lakes

In alkali lakes (a type of salt lake), evaporation concentrates the naturally occurring alkali salts, often forming a crust of mildly basic salt across a large area.

Examples of alkali lakes:

• Alkali Lake, British Columbia, Canada Referenced in feature movies X-Men II and III
• Alkali Lake (Oregon), Oregon, United States
• Baldwin Lake (San Bernardino County, California)
• Mono lake, California, United States
• Redberry Lake, Saskatchewan, Canada
• Summer Lake, Oregon, United States
• Tramping Lake, Saskatchewan, Canada
• Lake Magadi, Kenya
• Lake Turkana, Kenya (the largest alkali lake in the world)

References

1. ^ Chambers's encyclopaedia: a dictionary of universal knowledge, Volume 1. J.B. Lippincott & Co. 1888. p. 148. 
2. ^ http://dictionary.reference.com/search?q=alkali
3. ^ http://www.tiscali.co.uk/reference/encyclopaedia/hutchinson/m0029936.html
4. ^ http://www.thefreedictionary.com/alkali
5. ^ http://www.wahyan.edu.hk/paulsir/handout/form4/4-05_Characteriscs_of_alkali.pdf
6. ^ http://www.krysstal.com/acidbase.html

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Dansk (Danish)
n. - alkali, base

Nederlands (Dutch)
alkali (loogzout)

Français (French)
n. - alcali

Deutsch (German)
n. - Alkali

Ελληνική (Greek)
n. - (χημ.) άλκαλι, αλκάλιο

Italiano (Italian)
alcali

Português (Portuguese)
n. - álcali (m) (Quím.)

Русский (Russian)
щелочь

Español (Spanish)
n. - álcali

Svenska (Swedish)
n. - alkali

中文（简体）(Chinese (Simplified))
碱, 碱金属, 强碱, 可溶性无机盐

中文（繁體）(Chinese (Traditional))
n. - 鹼, 鹼金屬, 強鹼, 可溶性無機鹽

한국어 (Korean)
n. - 알칼리

日本語 (Japanese)
n. - アルカリ

العربيه (Arabic)
‏(الاسم) قلوي, فلزي‏

עברית (Hebrew)
n. - ‮חומר בסיסי המתחבר עם חומצות ליצירת מלחים, כל מלח מסיס המצוי בקרקע בכמות גדולה, בסיס, אלקלי‬

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