Etymology and Common properties of alkalis and bases
– The word alkali is derived from Arabic al qalīy (or alkali) meaning the calcined ashes.
– Potash, a water-extract of burned plant ashes, was mildly basic and composed mostly of potassium carbonate.
– Heating potash with calcium hydroxide produced caustic potash (potassium hydroxide), a strongly basic substance.
– Caustic potash was traditionally used with animal fats to produce soft soaps.
– Plant potash lent its name to the element potassium and gave it the chemical symbol K.
– Moderately concentrated alkaline solutions have a pH of 10 or greater.
– Concentrated alkaline solutions are caustic and can cause chemical burns.
– Alkaline solutions feel slippery or soapy to the touch due to the saponification of fatty substances on the skin.
– Alkalis are usually water-soluble, but some like barium carbonate require an acidic solution for solubility.
– Alkaline aqueous solutions turn phenolphthalein from colorless to pink.
Difference between alkali and base
– Alkalis are a subset of bases, usually defined as a basic salt of an alkali metal or alkaline earth metal.
– Alkalis can also be defined as any base that is soluble in water and forms hydroxide ions.
– The term alkali excludes ammonia, while the broader definition of a base includes ammonia.
– The second subset of bases is also known as an Arrhenius base.
Alkali salts
– Alkali salts are soluble hydroxides of alkali metals and alkaline earth metals.
– Examples of alkali salts include sodium hydroxide (caustic soda) and potassium hydroxide (caustic potash).
– Lye is a generic term for either of these salts or their mixture.
– Calcium hydroxide, also known as limewater, is another alkali salt.
– Magnesium hydroxide is an atypical alkali with low solubility in water but considered a strong base when dissolved.
Alkaline soil
– Soils with pH values higher than 7.3 are considered alkaline.
– Alkaline soils can occur naturally due to the presence of alkali salts.
– While some plants prefer slightly basic soil, most prefer mildly acidic soil.
– Alkaline soils can cause problems for many plants.
– Examples of plants that prefer slightly basic soil include cabbage and buffalo grass.
Alkali lakes
– Alkali lakes, also known as soda lakes, contain concentrated carbonate salts due to evaporation.
– These lakes are often alkaline and saline.
– Alkali lakes have been mentioned in historical literature.
– Evaporation in alkali lakes leads to the concentration of naturally occurring carbonate salts.
– J.B. Lippincott & Co. (1888) provides information on alkali lakes. Source: https://en.wikipedia.org/wiki/Alkali
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In chemistry, an alkali (/ˈælkəlaɪ/; from Arabic: القلوي, romanized: al-qaly, lit. 'ashes of the saltwort') is a basic, ionic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a soluble base has a pH greater than 7.0. The adjective alkaline, and less often, alkalescent, is commonly used in English as a synonym 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.