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27 Apr 15
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Naturally occurring potassium is composed of three isotopes, one of which, 40K, is radioactive. Traces (0.012%) of this isotope are found in all potassium, making 40K the most common radioisotope in the human body and in many biological materials, as well as in common building substances such as concrete.
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18 Aug 14
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The potassium ion is colorless in water and is very difficult to precipitate; possible precipitation methods include reactions with sodium tetraphenylborate, hexachloroplatinic acid, and sodium cobaltinitrite.[12]
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Some of the few poorly soluble potassium salts include potassium tetraphenylborate, potassium hexachloroplatinate, and potassium cobaltinitrite.[12]
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Orthoclase (potassium feldspar) is a common rock-forming mineral. Granite for example contains 5% potassium, which is well above the average in the Earth's crust.
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Several methods are applied to separate the potassium salts from the present sodium and magnesium compounds. The most-used method is to precipitate some compounds relying on the solubility difference of the salts at different temperatures. Electrostatic separation of the ground salt mixture is also used in some mines. The resulting sodium and magnesium waste is either stored underground or piled up in slag heaps. Most of the mined potassium minerals end up as potassium chloride after processing. The mineral industry refers to potassium chloride either as potash, muriate of potash, or simply MOP.[27]
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Pure potassium metal can be isolated by electrolysis of its hydroxide in a process that has changed little since Davy. Although the electrolysis process was developed and used in industrial scale in the 1920s the thermal method by reacting sodium with potassium chloride in a chemical equilibrium reaction became the dominant method in the 1950s. The production of sodium potassium alloys is possible by changing the reaction time and the amount of sodium used in the reaction. The Griesheimer process employing the reaction of potassium fluoride with calcium carbide was also used to produce potassium.[27][47]
- Na + KCl → NaCl + K (Thermal method)
- 2 KF + CaC2 → 2 K + CaF2 + 2 C (Griesheimer process)
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Potassium ions are an essential component of plant nutrition and are found in most soil types.[6] They are used as a fertilizer in agriculture, horticulture, and hydroponic culture in the form of chloride (KCl), sulfate (K
2SO
4), or nitrate (KNO
3). Agricultural fertilizers consume 95% of global potassium chemical production, and about 90% of this potassium is supplied as KCl.[6] The potassium content of most plants range from 0.5% to 2% of the harvested weight of crops, conventionally expressed as amount of K
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Modern high-yield agriculture depends upon fertilizers to replace the potassium lost at harvest. Most agricultural fertilizers contain potassium chloride, while potassium sulfate is used for chloride-sensitive crops or crops needing higher sulfur content. The sulfate is produced mostly by decomposition of the complex minerals kainite (MgSO4·KCl·3H2O) and langbeinite (MgSO4·K2SO4). Only a very few fertilizers contain potassium nitrate.[79] In 2005, about 93% of world potassium production was consumed by the fertilizer industry.[45]
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06 May 14
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Potassium is an extremely active metal
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which reacts violently with oxygen and water in air.
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The reaction of potassium with water is dangerous because of its violent exothermic character and the production of hydrogen gas
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23 Feb 14
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07 Dec 13
gthaberlachBecause of the sensitivity of potassium to water and air, the reactions are possible only in inert atmosphere, such as argon gas using air-free techniques. Potassium does not react with most hydrocarbons, such as mineral oil or kerosene.
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26 Nov 13
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Optimal intake[edit]
Epidemiological studies and studies in animals subject to hypertension indicate that diets high in potassium can reduce the risk of hypertension and possibly stroke (by a mechanism independent of blood pressure), and a potassium deficiency combined with an inadequate thiamine intake has produced heart disease in rats.[73] There is some debate regarding the optimal amount of dietary potassium. For example, the 2004 guidelines of the Institute of Medicine specify a DRI of 4,700 mg of potassium (100 mEq), though most Americans consume only half that amount per day, which would make them formally deficient as regards this particular recommendation.[74][75] Likewise, in the European Union, in particular in Germany and Italy, insufficient potassium intake is somewhat common.[76] Italian researchers reported in a 2011 meta-analysis that a 1.64 g higher daily intake of potassium was associated with a 21% lower risk of stroke.[77]
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Potassium salts are also available in tablets or capsules, which for therapeutic purposes are formulated to allow potassium to leach slowly out of a matrix, as very high concentrations of potassium ion (which might occur next to a solid tablet of potassium chloride) can kill tissue, and cause injury to the gastric or intestinal mucosa. For this reason, non-prescription supplement potassium pills are limited by law in the US to only 99 mg of potassium.
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24 Apr 13
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05 Apr 12
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4,000 mg of potassium
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1.64 g higher daily intake of potassium was associated with a 21% lower risk of stroke.[76]
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25 Oct 11
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08 Sep 11
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31 Mar 09
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Potassium is never found free, as it reacts violently with water, which is abundant in nature.[1] As various compounds, potassium makes up about 2.4% of the weight of the Earth's crust and is the seventh most abundant element.[1] As it is very electropositive, potassium metal is difficult to obtain from its minerals.
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Potassium metal was discovered in 1807 in England by Sir Humphry Davy, who derived it from caustic potash (KOH), by the use of electrolysis of the molten salt with the newly discovered voltaic pile. Before the 18th century, no distinction was made between potassium and sodium. Potassium was the first metal that was isolated by electrolysis. [2] Davy extracted sodium by a similar technique, demonstrating the elements to be different.[3]
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Potassium reacts very violently with water producing hydrogen gas which then usually catches fire. Potassium is usually kept under a hydrocarbon oil such as mineral oil or kerosene to stop the metal from reacting with water vapour present in the air. Unlike lithium and sodium, however, potassium should not be stored under oil indefinitely. If stored longer than 6 months to a year, dangerous shock-sensitive peroxides can form on the metal and under the lid of the container, which can detonate upon opening. It is recommended that potassium, rubidium or caesium not be stored for longer than three months unless stored in an inert (oxygen free) atmosphere, or under vacuum.[29]
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22 May 08
brent ggPotassium in the diet
Adequate intake can generally be guaranteed by eating a variety of foods containing potassium and deficiency is rare in healthy individuals eating a balanced diet. Foods with high sources of potassium include orange juice, potatoes, bananas, avocados, tomatoes, broccoli, soybeans and apricots, although it is also common in most fruits, vegetables and meats. Diets high in potassium can reduce the risk of hypertension and a potassium deficiency combined with an inadequate thiamine intake has produced heart disease in rats.[18] The 2004 guidelines of the Institute of Medicine specify a DRI of 4,000mg of potassium, though most Americans consume only half that amount per day.[19] Similarly, in the European Union, particularly in Germany and Italy, insufficient potassium intake is somewhat common.[20]
Supplements of potassium in medicine are most widely used in conjunction with loop diuretics and thiazides, classes of diuretics which rid the body of sodium and water, but have the side effect of also causing potassium loss in urine. A variety of medical supplements are available. If potassium supplements are used, such as sodium free baking powder and sodium free table salt, inadequate thiamine can cause beriberi.[21][22][citation needed]
Individuals suffering from kidney diseases may suffer adverse health effects from consuming large quantities of dietary potassium. End stage renal failure patients undergoing therapy by renal dialysis must observe strict dietary limits on potassium intake, since the kidneys control potassium excretion, and buildup of blood concentrations of potassium may trigger fatal cardiac arrhythmia. Acute hyperkalemia can be reduced through eating baking soda,[23] or glucose,[24][25] hyperventilation[26] and perspiration.[27]
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