alkali

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

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.

"Alkaline" redirects here. For the power cell, see Alkaline battery. For other uses of the word "alkali" see Alkali (disambiguation). "Alcali" also redirects here, for the place in Azerbaijan, see Alçalı.

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Look up alkali in Wiktionary, the free dictionary.

In chemistry, an alkali (from Arabic: Al-Qaly القلي, القالي ) is a basic, ionic salt of an alkali metal or alkaline earth metal element. Alkalis are best known for being bases that dissolve in water. Bases are compounds with 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. Since Brønsted-Lowry acid-base theory, the term alkali in chemistry is normally restricted to those salts containing alkali and alkaline earth metal elements.

Contents 1 Common properties 2 Confusion between alkali and base 3 Salts 4 Alkaline soil 5 Lakes 6 Etymology 7 References

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 10 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
• Alkalis are commonly found in household cleaners and toothpaste

Confusion between alkali and base

The terms "base" and "alkali" are often used interchangeably, particularly outside of a scientific context, but they do not have the same meaning. While all alkaline solutions are basic, not all bases are alkaline. The following are common mistakes:

• The phrase "measuring the alkalinity of soil" is incorrect since the property measured is actually the pH (base property).
• Calling bases that are not alkalis, such as ammonia, alkaline (ammonia is a base but not an alkali).

Also, not all salts formed by alkali metals are alkaline; this designation applies only to those salts that are basic. And while most electropositive metal oxides are basic, only the soluble alkali metal and alkaline earth metal oxides can be correctly called alkalis.

This definition of an alkali as a basic salt of an alkali metal or alkaline earth metal is the most common, based on dictionary definitions [1][2], however conflicting definitions of the term alkali do exist. These include:

• Any base that is water-soluble and [3][4] In chemistry, this is more accurately called an Arrhenius base.
• The solution of a base in water [5]. This would be an Arrhenius base in solution.

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")
• 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.

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:

• Redberry Lake, Saskatchewan, Canada.
• Tramping Lake, Saskatchewan, Canada.
• Mono lake, California, United States
• Summer Lake, Oregon, United States
• Alkali Lake, British Columbia and the adjoining reserves of the Alkali Lake Indian Band are named for a local Alkali Lake, which got its name from a large patch of alkali on the hillside above the lake, which is not itself alkali,^[1] although there are many in the Cariboo district and adjoining regions of the British Columbia Interior.

Etymology

The word "alkali" is derived from Arabic al qalīy = the calcined ashes, referring to the original source of alkaline substance. Ashes were used in conjunction with animal fat to produce soap, a process known as saponification.

References

1. ^ BCGNIS listing "Alkali Lake (community)"

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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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