potassium

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properties
General
Name , symbol , atomic number Potassium, K, 19
Element category Alkali metals
Group , period , block 1 , 4 , p
Appearance silvery white
CAS number 7440-09-7
EC number 231-119-8
ECHA InfoCard 100.028.290
Mass fraction of the earth's envelope 2.41%
Atomic
Atomic mass 39.0983 (1) et al
Atomic radius (calculated) 220 (243) pm
Covalent radius 203 pm
Van der Waals radius 275 pm
Electron configuration [ Ar ] 4 s 1
1. Ionization energy 4th.340 663 69 (9) eV 418.81 kJ / mol
2. Ionization energy 31.62500 (19) eV3 051.35 kJ / mol
3. Ionization energy 45.8031 (17) eV4 419.3 kJ / mol
4. Ionization energy 60.917 (19) eV5 878 kJ / mol
5. Ionization energy 82.66 (16) eV7 975 kJ / mol
Physically
Physical state firmly
Crystal structure body-centered cubic
density 0.856 g / cm 3 (20 ° C )
Mohs hardness 0.4
magnetism paramagnetic ( Χ m = 5.7 10 −6 )
Melting point 336.53 K (63.38 ° C)
boiling point 1047 K (774 ° C)
Molar volume 45.94 · 10 −6 m 3 · mol −1
Heat of evaporation 79.1 kJ / mol
Heat of fusion 2.334 kJ mol −1
Speed ​​of sound 2000 m s −1 at 293.15 K.
Specific heat capacity 757.8 J kg −1 K −1
Work function 2.30 eV
Electric conductivity 14.3 · 10 6 A · V −1 · m −1
Thermal conductivity 100 W m −1 K −1
Chemically
Oxidation states −1, +1
Normal potential −2.931 V (K + + e - → K)
Electronegativity 0.82 ( Pauling scale )
Isotopes
isotope NH t 1/2 ZA ZE (M eV ) ZP
38 K {syn.} 7.636  min β + 2.17 38 ares
39 K 93.26  % Stable
40 K 0.0117% 1.248 x 10 9  a β - 1,311 40 approx
ε 1.505 40 ares
β + 1.505 40 ares
41 K 6.73% Stable
42 K {syn.} 12.36  h β - 3.525 42 approx
43 K {syn.} 22.3  h β - 1,815 43 Approx
For other isotopes see list of isotopes
NMR properties
  Spin
quantum
number I
γ in
rad · T −1 · s −1
E r  ( 1 H) f L at
B = 4.7 T
in MHz
39 K 3/2 0+1.25006 · 10 7 5.1 · 10 −4 009.3508
40 K 4th 0−1.554286 10 7 5.23 · 10 −3 011.626
41 K 3/2 0+0.68607 10 7 8.4 · 10 −5 005.132
safety instructions
GHS hazard labeling from  Regulation (EC) No. 1272/2008 (CLP) , expanded if necessary
02 - Highly / extremely flammable 05 - Corrosive

danger

H and P phrases H: 260-314
EUH: 014
P: 223-231 + 232-280-305 + 351 + 338-370 + 378-422
As far as possible and customary, SI units are used.
Unless otherwise noted, the data given apply to standard conditions .

Potassium ( Latin , from Arabic القلية, DMG al-qalya  'plant ash') is a chemical element with the element symbol K and the atomic number 19. In the periodic table it is in the first main group or the 1st  IUPAC group and is one of the alkali metals .

Potassium is one of the ten most common elements in the earth's shell and occurs in numerous minerals in the earth's crust .

history

Humphry Davy , discoverer of potassium
Potassium under tetrahydrofuran

On November 19, 1807, Humphry Davy reported to the Royal Society in London that he had succeeded in obtaining two different metals by electrolysis of weakly humidified caustic alkalis; One of the metals, first extracted on October 6, 1807, he called potassium (the English and French term for potassium that is still used today) because it can be extracted from potash , while the other, obtained a few days later, is sodium (which is still used today English and French name for sodium ), because it is contained in the various modifications of sodium carbonate (soda). In the German-speaking world, the Sodium Davy is since 1811, as suggested by Berzelius called sodium, while for the Potassium Davy to one of Klaproth introduced in 1796 express potassium (from Arab.القَلْيَة al-qalya = ash, obtainable from plant ash) took over.

Occurrence

In nature, potassium only occurs as a cation in potassium compounds. This is due to the fact that it only has one outer electron and that it gives it up very willingly in order to obtain a stable and low-energy outer electron shell . Covalent potassium compounds are therefore not known. The average concentration in seawater is 399.1 mg K + / kg = 408.4 mg K + / l.

Naturally occurring minerals containing potassium are:

Potassium salts form evaporation deposits on former seabeds , which makes the extraction of potassium salts in these areas economical. Potash salt is mined in Canada, Russia, Belarus, Kazakhstan, Germany, Israel, the United States, Jordan and other locations around the world. The largest deposits ever found are 1,000 meters below the surface in the Canadian province of Saskatchewan. The deposits are located in the Elk Point Group, which formed in the central Devonian . In Saskatchewan , where several large mines had been in operation since the 1960s , the technique of freezing wet sand (the Blairmore Formation) was introduced to drive mine shafts through them. The main potash mining company in Saskatchewan is the Potash Corporation . The Dead Sea water is used as a source of potash by Israel and Jordan, while the concentration in normal oceans is too low for commercial production at current prices.

In 2010, potassium was detected in the atmosphere of exoplanets XO-2b and HD 80606 b .

Extraction and presentation

Metallic potassium can be extracted using several methods. Electrolytic processes such as the Degussa process or a thermal process from IG Farben , Griesheim plant were used. Most of potassium, however, with the in the 1950s by Mine Safety Appliances made introduced MSA method in which at 870 ° C under a protective gas atmosphere with metallic sodium is a reduction of potassium chloride is carried out. The resulting gaseous potassium is deposited in a cold trap by condensation.

Commercially available Na-K alloys are also accessible by varying the distillation parameters.

Elemental potassium can be found in the laboratory via the reduction of chromate or dichromate using zirconium according to:

or the thermal decomposition of potassium azide :

as well as a subsequent distillation under high vacuum are available.

properties

potassium
Potassium in an ampoule under paraffin oil

Phase diagram potassium sodium s l.svg

Similar to the other alkali metals , potassium often reacts very violently with many other elements and compounds , especially with non-metals , and occurs only chemically bound in the natural environment . Potassium has a higher reactivity than sodium and reacts violently with water to form potassium hydroxide and release of hydrogen . High-speed recordings of the reaction of alkali metals with water suggest a Coulomb explosion .

Reaction of potassium with water

Due to the strongly exothermic reaction , the hydrogen ignites when air enters. This can lead to deflagrations and explosions . In dry oxygen , the metal burns with an intense violet flame to form potassium hyperoxide KO 2 and potassium peroxide K 2 O 2 .

or.
Reaction of potassium with oxygen

In moist air it reacts very quickly with water and carbon dioxide to form potassium carbonate with the formation of hydrogen .

Reaction of potassium with water and carbon dioxide

Potassium reacts with alcohols to form alcoholates with the formation of hydrogen .

Reaction of potassium with ethanol

Like all alkali metals , potassium is readily soluble in liquid ammonia , forming a blue-violet solution . With the halogens bromine and iodine in liquid or solid form, potassium is explosively converted to the corresponding halides .

To dispose of potassium, it is usually recommended to carefully introduce small pieces of the metal into a large excess of tert-butyl alcohol , with which it reacts to form the alcoholate and hydrogen . Since this reaction proceeds very slowly, it can happen that small potassium residues remain unnoticed, covered with a crust of potassium tert- butanolate . Therefore, care must be taken to ensure that the reaction is complete. Alternatively, 1-butanol can also be used for small amounts of potassium , which reacts with the potassium more quickly but is still controllable. Under no circumstances should "lower" alcohols ( propanols , ethanol or methanol ) be used, as these react too violently with potassium and are also more flammable .

In the air , the shiny silver-white cut surface of the fresh metal is covered with a bluish shimmering layer of oxide and hydroxide and a little carbonate within seconds . Left to stand in the air, like all alkali metals, it slowly reacts completely to form carbonate . Metallic potassium is therefore used in anhydrous organic liquids , such as. B. stored paraffin oil. In contrast to sodium , potassium can still form crusts of oxides , peroxides and hydroxides after prolonged storage , which coat the metal in the form of reddish-yellow layers and which can explode if touched or pressed . Safe disposal is then no longer possible; the only option here is to burn off the entire container under controlled conditions. Potassium welded into polyethene packaging can also become coated with an explosive crust, so such packaging is not suitable for storage .

Liquid mixtures are formed with sodium in a wide range of concentrations at room temperature , see: NaK (alloy) . The phase diagram shows a compound Na 2 K which melts incongruously at 7 ° C and a eutectic at −12.6 ° C with a sodium content of 23% w .

use

Potassium has been used as a cooling fluid in some fast nuclear reactors in the form of a eutectic Na-K alloy . Otherwise, metallic potassium is of little technical importance because it can be replaced by the cheaper sodium .

In the research laboratory potassium is occasionally for drying of solvents used, especially when the boiling point of the solvent above the melting point of potassium, but below the melting point of sodium is located. Then the potassium is melted in the boiling solvent and its surface does not become encrusted. This means that significantly less alkali metal is required and it can be used up almost entirely in the drying process, so that only very small residues have to be disposed of.

When left standing for a long time, potassium develops crusts of peroxo compounds (K 2 O 2 and KO 2 ), even under protective liquid ( petroleum ), which react very explosively . Even with low pressure , especially when lifting pieces of potassium out with pliers or trying to cut with a knife , these peroxo compounds can trigger explosions . As countermeasures, either melting in glass ampoules or storage under protective liquid and inert gas are recommended . Furthermore, due to the risk of explosion , halogenated solvents must not be dried with potassium. Reactions of potassium in the interplay of solvents, which can easily give off oxygen , are also dangerous .

Other uses:

Biological importance

Importance as a fertilizer

Water-soluble potassium salts are used as fertilizers because plants have difficulty digesting the potassium silicates found in the soil .

The industrial agriculture uses fertilizers to the in the harvest to replace lost potassium. Most agricultural fertilizers contain potassium chloride , while potassium sulfate is used for chloride sensitive crops or crops with higher sulfur content . Few fertilizers contain potassium nitrate . Other fertilizers containing potassium are Kornkali with magnesium oxide , Patentkali, Flory, Nitrophoska and potassium phosphate .

The essential macronutrient potassium has a wide range of effects in plants . In the xylem , it serves as an osmotic which is crucial for building up root pressure. Potassium in the leaf cells increases turgor , which leads to cell elongation and leaf surface growth . By increasing the turgor, it also provides for an opening of the stomata , which promotes carbon dioxide uptake and thus has a direct influence on photosynthesis . If potassium is present in sufficient quantities, it promotes the formation of C3 sugars in a first step , which are processed into starch , cellulose , lignin and proteins in other metabolic processes influenced by potassium . Plants that suffer from a lack of potassium show symptoms mainly on the older leaves . Potassium is retranslocated from them and transported into young leaves via the phloem . Typical symptoms of a potassium deficiency are point, intercostal and leaf margin chlorosis and leaf margin necrosis . There is also a compressed habit and possibly wilting . Strong sunlight can cause photo-oxidation in the leaves. A larger excess causes root burns and a calcium or magnesium deficiency .

Potassium is the antagonist of calcium - both nutritional elements must be present in the right proportion to one another in the plant and in the soil.

Significance for the human body

Potassium is an essential mineral ( bulk element ) for the maintenance of life . As the most important intracellular cation , potassium is involved in the physiological processes in every cell:

Recommended and Actual Potassium Intakes

To maintain all vital physiological processes, it is advised to consume at least 2 g of potassium daily. The Food and Nutrition Board (FNB) of the USA and Canada, however, considers an intake of 4.7 g / day (120 mmol / day) to be appropriate for all adults from a preventive perspective. Based on new findings, this amount of potassium (from food) is necessary to prevent, reduce or delay chronic diseases such as increased blood pressure , salt sensitivity , kidney stones , loss of bone mass or strokes .

According to the National Nutrition Survey II (NVS II), the potassium intake is located in Germany in the median at 3.1 g / day (females) or 3.6 g / day (men). The intake of 4.7 g potassium per day recommended by the FNB is not achieved by 75% of men and 90% of women.

Importance of the sodium / potassium ratio

Top view of a potassium channel , the purple potassium ions pass through the channel

Potassium plays an important role in regulating membrane potential in the body . The intracellular potassium concentration is around 150 mmol / l, extracellularly 4 mmol / l. The intracellular sodium concentration is around 10 mmol / l, extracellular around 140 mmol / l. These differences in concentration are maintained by the Na / K-ATPase and are vital for the function of the cell. A permanent shift in these cellular concentrations can lead to cardiac arrest in systole with increased K + concentration ( hyperkalaemia ), i.e. K + >> 4.5 mmol / l, and to hypokalaemia (K + <3.5 mmol / l) Decrease in the ability of muscles to contract, increased excitement, disruption of the conduction of excitation, extrasystoles of the heart. K + is (besides Na + ) decisive for the osmotic pressure of the cells, i.e. for the water content of the cell. Too low a K + concentration in the blood leads to cardiac arrest in diastole . The normal range in serum is 3.6–4.5 mmol / l, in urine 26–123 mmol / l. That is, K + is constantly being lost, which needs to be replaced with food.

This is particularly a problem today, as the western diet is characterized by the consumption of animal foods. However, the intake of plant-based foods rich in potassium is significantly reduced compared to before. Before the development of agriculture, the potassium intake was 10.5 g / day, compared to the average 3.4 g / day according to NVS II. On the other hand, the sodium intake, which was shifted into the opposite, was previously only 0.8 g / day and has increased to an average of 3.1 g / day (women) and 4.3 g / day (men) due to our high-salt diet. This affects the natural potassium to sodium ratio in the human body.

Potassium is the natural antagonist of sodium , and a balanced ratio of the two minerals is particularly important for the regulation of physiological processes. Excessive sodium intake can lead to potassium depletion. Conversely, potassium has a natriuretic effect. In this respect, the Na / K ratio in the food is more decisive than the concentration of the individual cations on their own. The WHO recommends a molar ratio of the two minerals of 1: 1. The WHO recommendations of less than 2 g sodium per day and at least 3.5 g potassium per day meet this ratio.

Physiological importance

In addition to sodium, potassium is of great importance for regulating blood pressure . Epidemiological studies have shown that increased potassium intake is associated with lowering blood pressure and reduces the risk of stroke. The antihypertensive effect of potassium has also been shown in supplementation attempts.

The so-called DASH (Dietary Approaches to Stop Hypertension) diet (rich in whole grain cereal products, fruit, vegetables, poultry, fish and nuts) could also lower the blood pressure . In contrast to the usual diet, this diet contains less table salt and saturated fats, a relatively large amount of potassium, but also more other nutrients such as magnesium and calcium, which are also held responsible for lowering blood pressure. For this reason, a diet rich in fruits and vegetables (rich in potassium) in combination with a moderate reduction in sodium intake should be recommended, as a sodium to potassium ratio of 1 or less has a beneficial effect on blood pressure. It does not make sense to adjust the potassium intake to a high sodium intake. The European Food Safety Authority (EFSA) also confirms the blood pressure-increasing effect of sodium.

Potassium also has a positive influence on bone metabolism, as a higher potassium intake prevents the increased excretion of calcium, which is caused by a high salt intake. Potassium thus promotes renal calcium retention in the kidneys and prevents calcium breakdown from the bones . In this context, the influence of the accompanying anion, the composition of the food and the age on the acid-base status must also be taken into account. Clinical studies have shown that potassium citrate counteracts calcium loss via the kidneys and calcium breakdown from the bones. A prospective controlled intervention study in 161 postmenopausal women with osteopenia showed that the partial neutralization of diet-induced acid exposure (using 30 mmol potassium citrate per day, equivalent to 1.173 g potassium) over a period of twelve months significantly increases bone density and significantly improves bone structure. Potassium citrate was just as effective as raloxifene , an estrogen receptor modulator used in the treatment and prevention of osteoporosis in postmenopausal women.

Potassium is an important electrolyte . Potassium ions are mainly found inside the cell ( intracellular space ), where they are involved in maintaining the resting potential . Therefore, high potassium losses, such as through heavy sweating , can lead to cramps and states of exhaustion.

Foods rich in potassium have a diuretic / dehydrating effect . In dialysis -dependent patients with impaired renal function , it is important that they avoid strong potassium-containing foods, as this can cause hyperkalemia in life-threatening conditions.

The lethal injection used for executions in the United States contains potassium chloride , which paralyzes the heart muscles and thus leads to death.

For more information on the physical effects of potassium

Potassium levels in foods

Foods rich in potassium include mushrooms, bananas, dates, raisins, beans, chilli, cheese, spinach and potatoes, which contain between 0.2 and 1.0 g of potassium per 100 g of food.

Potassium levels in foods rich in potassium in mg per 100 g; from the USDA National Nutrient Database (2011)

Food 100 g potassium
Soybean (dried) 000000000001800.00000000001,800 mg
Apricots (dried) 000000000001370.00000000001,370 mg
Wheat bran 000000000001350.00000000001,350 mg
pistachio 000000000001020.00000000001,020 mg
Tomato paste 000000000001014.00000000001,014 mg
Beetroot -leaves (cooked) 000000000000909.0000000000909 mg
lenses 000000000000840.0000000000840 mg
Raisins 000000000000749.0000000000749 mg
Almonds 000000000000705.0000000000705 mg
Orange juice concentrate 000000000000674.0000000000674 mg
peanut 000000000000658.0000000000658 mg
Date (Deglet Nour) 000000000000656.0000000000656 mg
soy milk 000000000000638.0000000000638 mg
Sweet chestnuts (roasted) 000000000000592.0000000000592 mg
Buckwheat flour (whole grain) 000000000000577.0000000000577 mg
Cashew 000000000000565.0000000000565 mg
French fries (vegetable oil) 000000000000550.0000000000550 mg
Potatoes (unpeeled, baked) 000000000000535.0000000000535 mg
Soybeans (cooked) 000000000000515.0000000000515 mg
avocado 000000000000485.0000000000485 mg
Grapefruit juice (white) 000000000000484.0000000000484 mg
Spinach (cooked) 000000000000466.0000000000466 mg
Plantains (cooked) 000000000000464.0000000000464 mg
White beans 000000000000454.0000000000454 mg
Tomato puree 000000000000439.0000000000439 mg
Kidney beans (cooked) 000000000000402.0000000000402 mg

Since the potassium salts contained in food are very soluble in water, the potassium content of food can be noticeably reduced by so-called soaking ( soaking in water for about three to five hours). This is especially important for people with kidney and metabolic disorders.

radioactivity

40 K decay diagram

Natural potassium consists of 0.0117 percent of the radioactive isotope 40 K and therefore has a specific activity of 31.6  Becquerel per gram. With 0.17  mSv per year, almost 10 percent of the natural radiation dose in Germany (an average of 2.1  mSv per year) is due to the body's own potassium.

40 K decays through β-decay : with a probability of 89% through β - -decomposition into stable 40 calcium and with 11% probability through β + -decay or electron capture (EC, K-capture) into stable 40 argon . The half-life is 1.248 billion years.

The decay from 40 K to 40 Ar is an essential source of argon in the earth's atmosphere and can also be used to determine the age by means of potassium-argon dating .

Physical peculiarity

The metal potassium may according to a computer simulation under extreme pressure simultaneously fixed and liquid to be because, according to the simulation then though most of atoms in solid bars , however, to arrange some atoms for liquid to be. Under extreme pressure , potassium is a solid block from which liquid potassium leaks out at the same time.

Potassium detection

The flame color of potassium

In addition to the spectroscopic detection based on the color of the flame , potassium ions dissolved in water can be detected and determined potentiometrically with an ion-selective electrode specializing in K + . Most potassium electrodes use the specific complexation of potassium by valinomycin C 54 H 90 N 6 O 18 , which is embedded in a plastic membrane in a concentration of around 0.7%.

A qualitative proof of potassium is possible using perchloric acid . Potassium perchlorate (KClO 4 ) , which is sparingly soluble in water in the cold, forms as a white precipitate . However, other form cations such as rubidium , cesium and ammonium white, heavy in the cold -soluble precipitates .

Potassium can be determined quantitatively with the help of gravimetry . Here, potassium is as potassium tetraphenylborate (K [B (C 6 H 5 ) 4 ]) by adding to the solution with Kalignost precipitated and the resulting precipitate balanced.

Further evidence is possible as precipitations of potassium hexanitrocobaltate (III) , potassium hydrogen tartrate (K A = 3.80 · 10 −4 ) and potassium hexachloroplatinate (IV) .

In routine analysis ( clinical chemistry ( blood ), environmental chemistry , water chemistry ), potassium is determined quantitatively down to the trace level using flame photometry . The limit of quantification mentioned here is 100 µg / l. In atomic absorption spectrometry , 1 µg / l can still be detected with the flame technique , and 0.004 µg / l with the graphite furnace technique.

links

Category: Potassium Compound

In its compounds, potassium occurs only as a monovalent cation with the oxidation state 1.

Oxides

Potassium oxide is a very reactive white solid and has an antifluorite crystal structure in the cubic crystal system in the space group Fm 3 m (space group no. 225) . There the positions of the anions and cations are reversed relative to their positions in fluorite , with potassium ions bound to 4 oxide ions and oxide ions bound to 8 potassium ions. Template: room group / 225

Potassium peroxide is a very reactive fire-promoting solid that is not itself flammable , but reacts violently with flammable substances . It decomposes violently on contact with water . It is used as an oxidizer and bleach, as well as to purify air .

Potassium hyperoxide is a yellow, salty compound . It decomposes in water to form potassium hydroxide , hydrogen peroxide and oxygen .

Halides

Potassium chloride forms colorless, odorless, easily water-soluble crystals . Potassium chloride occurs in nature as sylvine . Other widely used minerals and rocks containing potassium and chloride are carnallite (KCl · MgCl 2 · 6 H 2 O), kainite (KCl · MgSO 4 · 3 H 2 O) and sylvinite (KCl · NaCl). It is used in food technology as a firming agent and flavor enhancer . It is used for the production of potash fertilizers and almost all technically used potassium compounds such as potassium carbonate and potassium hydroxide .

Potassium fluoride is a white, hygroscopic powder that usually occurs as a dihydrate . It is used for the production of glazes , as a cement additive , as an oxide-dissolving component of aluminum welding powders, as a wood preservative and for glass etching .

Potassium bromide is used for the production of silver - emulsions on films and plates for photographic films used. In photographic developers, it counteracts fogging and delays development.

Potassium iodide is used in the laboratory for the production of iodine potassium iodide solution (Lugol's solution). It is also used in the production of silver iodide and in the production of pharmaceuticals and in analytical chemistry for the detection of certain compounds .

All of these potassium compounds have a cubic crystal structure of the sodium chloride type.

More connections

Potassium hydroxide is a white, hygroscopic, odorless solid. In water , it dissolves to form the strong base potassium hydroxide with great heat development . In microsystem technology , it is used for the selective anisotropic etching of monocrystalline silicon . In microbiology it is used to differentiate between gram-positive and gram-negative bacteria in the rapid test method. It is used as an electrolyte in galvanic oxygen sensors. It fulfills the same purpose in the widespread alkali-manganese cells and the historically important nickel-cadmium accumulators . It is used as an acidity regulator in the food industry.

Potassium carbonate is a white, hygroscopic powder. It has a monoclinic crystal structure in the space group P 2 1 / c (space group no. 14) . It is used in the manufacture of glass , paint and photographic developers . Template: room group / 14

Potassium hydrogen carbonate is used as a release agent and acidity regulator in foods and as a raising agent .

Potassium chlorate is a white stable salt that makes a colorless solution in water . The connection has a strong oxidizing and will among other things for the production of matches , primer caps and other pyrotechnic products used.

In its pure form, potassium perchlorate forms rhombic prisms that can be several centimeters in size. The crystal system is orthorhombic in the space group Pnma (space group no. 62) . It is often used in pyrotechnics because of its strong fire-promoting effect and its good shelf life , for example as an oxidizing agent in lightning bolts . It is now rarely used in rocket engines because it has been replaced by ammonium perchlorate . Template: room group / 62

Potassium nitrate is the main component of black powder . It is also used for preservation of food used.

Potassium sulfate is mainly used as a fertilizer .

Potassium phosphate is used as an additive in detergents , as a fertilizer and as an acidity regulator in food .

Potassium dichromate is an orange salt. It has a triclinic crystal structure in the space group P 1 (space group no. 2) . In the laboratory it is used because of its good shelf life and as an oxidizing agent , reagent for the detection of hydrogen peroxide and basic titre substance . In engineering it is used in tannery , electroplating , matches and for the production of chromosulfuric acid . Template: room group / 2

Potassium permanganate is a metallic, shiny , almost black crystalline solid and a strong oxidizing agent .

Potassium hexacyanoferrate (II) forms yellow, monoclinic crystals . By oxidation with hydrogen peroxide or chlorine can be Kaliumhexacyanidoferrat (III) produced. In the food industry it is used as a release agent and stabilizer . However, it may only be used in small quantities in food , as hydrogen cyanide can form when heated or when exposed to acids .

Potassium cyanide (cyanide) is the potassium salt of hydrogen cyanide and is also highly toxic. It is used in industrial manufacturing processes , where it is mainly used for gold extraction ( cyanide leaching ) and in galvanic baths, but also in organic synthetic chemistry for the production of nitriles .

Potassium hydrogen tartrate (tartar) is a salt of tartaric acid . It is produced during the storage of wine or grape juice . It is used to produce tartaric acid and, together with sodium hydrogen carbonate, as a raising agent .

Soaps are sodium or potassium salts of fatty acids . For production , fats are boiled with caustic soda or potassium hydroxide . This process is called soap boiling , the chemical reaction saponification . The fats are broken down into glycerine and the alkali salts of the fatty acids (the actual soaps). Alternatively, soaps can be made directly from free fatty acids by reacting them with alkalis to form their salts . Suitable fatty acids are, for example, lauric acid , myristic acid , palmitic acid , stearic acid , oleic acid and ricinoleic acid .

Individual evidence

  1. a b Harry H. Binder: Lexicon of the chemical elements. S. Hirzel Verlag, Stuttgart 1999, ISBN 3-7776-0736-3 .
  2. The values ​​for the properties (info box) are taken from www.webelements.com (potassium) , unless otherwise stated .
  3. CIAAW, Standard Atomic Weights Revised 2013 .
  4. a b c d e Entry on potassium in Kramida, A., Ralchenko, Yu., Reader, J. and NIST ASD Team (2019): NIST Atomic Spectra Database (ver. 5.7.1) . Ed .: NIST , Gaithersburg, MD. doi : 10.18434 / T4W30F ( https://physics.nist.gov/asd ). Retrieved June 11, 2020.
  5. a b c d e Entry on potassium at WebElements, https://www.webelements.com , accessed on June 11, 2020.
  6. ^ NN Greenwood, A. Earnshaw: Chemistry of the elements. 1st edition. VCH, Weinheim 1988, ISBN 3-527-26169-9 , p. 97.
  7. Robert C. Weast et al. (Ed.): CRC Handbook of Chemistry and Physics . CRC (Chemical Rubber Publishing Company), Boca Raton 1990, ISBN 0-8493-0470-9 , pp. E-129 to E-145. Values ​​there are based on g / mol and given in cgs units. The value specified here is the SI value calculated from it, without a unit of measure.
  8. a b Yiming Zhang, Julian RG Evans, Shoufeng Yang: Corrected Values ​​for Boiling Points and Enthalpies of Vaporization of Elements in Handbooks. In: Journal of Chemical & Engineering Data. 56, 2011, pp. 328-337, doi: 10.1021 / je1011086 .
  9. ^ Ludwig Bergmann, Clemens Schaefer, Rainer Kassing: Solid body. (= Textbook of Experimental Physics . Volume 6). 2nd Edition. De Gruyter, Berlin 2005, ISBN 3-11-017485-5 , p. 361.
  10. David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Electrochemical Series, pp. 8-22.
  11. a b Entry on potassium in the GESTIS substance database of the IFA , accessed on December 16, 2019(JavaScript required) .
  12. Entry on Potassium in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on August 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
  13. ^ A b Potash Statistics and Information . United States Geological Survey.
  14. ^ David J. Wishart: Encyclopedia of the Great Plains . U of Nebraska Press, 2004, ISBN 978-0-8032-4787-1 , p. 433.
  15. ^ New Technique Finds Gaseous Metals in Exoplanet Atmospheres wired.com, August 31, 2010.
  16. Astronomers Find Potassium in Giant Planet's Atmosphere sciencedaily.com, September 1, 2010, (accessed September 20, 2010).
  17. ^ AE van Arkel, P. Assmann, G. Borelius, G. Chaudron, EJ Daniels, R. Gadeau, W. Geibel, W. Graßmann, CR Hayward, G. Jantsch, W. Kroll, K. Lins: Reine Metals: Production Properties Use , publisher AE van Arkel, Verlag Springer-Verlag, 2013, ISBN 9783642996955 .
  18. Georg Brauer: Free alkali metals . In: Handbook of Preparative Inorganic Chemistry . Ferdinand Enke Verlag, Stuttgart 1954, p. 724 ff .
  19. PE Mason, F. Uhlig, V. Vaněk, T. Buttersack, S. Bauerecker, P. Jungwirth: Coulomb explosion during the early stages of the reaction of alkali metals with water. In: Nature chemistry. Volume 7, number 3, March 2015, pp. 250-254, doi: 10.1038 / nchem.2161 , PMID 25698335 .
  20. Freie Universität Berlin , Institute for Chemistry and Biochemistry Disposal of Potassium ( Memento from December 13, 2013 in the web archive archive.today )
  21. J. Evers, TM Klapötke, G. Oehlinger: Dangerous Potassium Hydroxide Monohydrate Crust. In: Chemical & Engineering News , 80 (37), pp. 2, 4.
  22. GLCM van Rossen, H. van Bleiswijk: About the state diagram of the potassium-sodium alloys. In: Z. anorg. allg. Chem. , 1912, 74, pp. 152-156. doi: 10.1002 / zaac.19120740115 .
  23. Konrad Mengel: Nutrition and metabolism of the plant. 7th edition. Fischer, Jena 1991, ISBN 3-334-00310-8 , pp. 335-346.
  24. Shieh et al: Potassium channels: molecular defects, diseases, and therapeutic opportunities. In: Pharmacol Rev . 52 (4), Dec 2000, pp. 557-594, PMID 11121510 .
  25. ^ Tamargo et al.: Pharmacology of cardiac potassium channels. In: Cardiovasc Res . 62 (1), Apr 1, 2004, pp. 9-33, PMID 15023549 .
  26. Niemeyer et al: Modulation of the two-pore domain acid-sensitive K + channel TASK-2 (KCNK5) by changes in cell volume. In: J Biol Chem . 276 (46), Nov 16, 2001, pp. 43166-43174, PMID 11560934 .
  27. Shen et al: The KCl cotransporter isoform KCC3 can play an important role in cell growth regulation. In: Proc Natl Acad Sci USA . 98 (25), 4 Dec 2001, pp. 14714-14719, PMID 11724933 .
  28. Young et al.: Determinants of cardiac fibrosis in experimental hypermineralocorticoid states In: Am J Physiol-Endocrinol Metab . 269 ​​(4 Pt 1), Oct 1995, pp. E657-E662, PMID 7485478 .
  29. ^ Young & Ma: Vascular protective effects of potassium. In: Semin Nephrol. 19, 1999, pp. 477-486, PMID 10511387 .
  30. Krishna: Effect of potassium intake on blood pressure. In: J Am Soc Nephrol . 1 (1), Jul 1990, pp. 43-52, PMID 2104250 .
  31. ^ Suter: Potassium and hypertension. In: Nutr Rev. 56 (5 Pt 1), May 1998, pp. 151-153, PMID 9624886 .
  32. Young et al .: Potassium's cardiovascular protective mechanisms. In: Am J Physiol-Regul Integr Comp Physiol . 268 (4 Pt 2), Apr 1995, pp. R825-R837, PMID 7733391 .
  33. ^ Tannen: The influence of potassium on blood pressure. In: Kidney Int Suppl . 22, 1987, pp. S242-S248, PMID 3323616 .
  34. Frassetto et al .: Diet, evolution and aging - the pathophysiologic effects of the post-agricultural inversion of the potassium-to-sodium and base-to-chloride ratios in the human diet. In: Eur J Nutr. 40 (5), Oct 2001, pp. 200-213, PMID 11842945 .
  35. Frassetto et al .: Estimation of net endogenous noncarbonic acid production in humans from diet potassium and protein contents. In: Am J Clin Nutr. 68 (3), Sep 1998, pp. 576-583, PMID 9734733 .
  36. Frassetto et al .: Potassium bicarbonate reduces urinary nitrogen excretion in postmenopausal women. In: J Clin Endocrinol Metab . 82 (1), Jan 1997, pp. 254-259, PMID 8989270 .
  37. Manz et al .: Factors affecting renal hydrogen ion excretion capacity in healthy children. In: Pediatr Nephrol . 16 (5), May 2001, pp. 443-445, PMID 11405120 .
  38. Remer et al.: Dietary potential renal acid load and renal net acid excretion in healthy, free-living children and adolescents. In: Am J Clin Nutr. 77 (5), May 2003, pp. 1255-1260, PMID 12716680 .
  39. ^ Remer: Influence of diet on acid-base balance. In: Semin Dial. 13 (4), Jul-Aug 2000, pp. 221-226, PMID 10923348 .
  40. Tannen: Effect of potassium on renal acidification and acid-base homeostasis. In: Semin Nephrol. 7 (3), Sep 1987, pp. 263-273, PMID 2825318 .
  41. European Food Safety Authority : EFSA Journal. 8 (2), 2010, p. 1469.
  42. Federal Institute for Risk Assessment : Use of Minerals in Food: Toxicological and Physiological Aspects .
  43. Curhan et al .: Comparison of dietary calcium with supplemental calcium and other nutrients as factors affecting the risk for kidney stones in women. In: Ann Intern Med . 126 (7), Apr 1, 1997, pp. 497-504. PMID 9092314 .
  44. Hirvonen et al.: Nutrient intake and use of beverages and the risk of kidney stones among male smokers. In: Am J Epidemiol. 150 (2), Jul 15, 1999, pp. 187-194. PMID 10412964 .
  45. Keßler & Hesse: Cross-over study of the influence of bicarbonate-rich mineral water on urinary composition in comparison with sodium potassium citrate in healthy male subjects. In: Br J Nutr. 84 (6), Dec 2000, pp. 865-871. PMID 11177203 .
  46. Macdonald et al .: Nutritional associations with bone loss during the menopausal transition: evidence of a beneficial effect of calcium, alcohol, and fruit and vegetable nutrients and of a detrimental effect of fatty acids. In: Am J Clin Nutr. 79 (1), Jan 2004, pp. 155-165. PMID 14684412 .
  47. Morris et al.: Differing effects of supplemental KCl and KHCO3: pathophysiological and clinical implications. In: Semin Nephrol. 19 (5), Sep 1999, pp. 487-493. PMID 10511388 .
  48. Sellmeyer et al: Potassium citrate prevents increased urine calcium excretion and bone resorption induced by a high sodium chloride diet. In: J Clin Endocrinol Metab. 87 (5), May 2002, pp. 2008-2012. PMID 11994333 .
  49. a b Suter: The effects of potassium, magnesium, calcium, and fiber on risk of stroke. In: Nutr Rev. 57 (3), Mar 1999, pp. 84-88. PMID 10101922 .
  50. ^ A b Max Rubner Institute, Federal Research Institute for Nutrition and Food (2008) National Consumption Study II. Results report part 2. The nationwide survey on the nutrition of adolescents and adults. ( Memento of the original from December 28, 2013 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 3.3 MB). @1@ 2Template: Webachiv / IABot / www.mri.bund.de
  51. a b Eaton et al .: Paleolithic nutrition revisited: a twelve-year retrospective on its nature and implications. In: Eur J Clin Nutr. 51 (4), 1997, pp. 207-216. PMID 9104571 .
  52. ^ P. Elliott, I. Brown: Sodium intakes around the world. Background document prepared for the Forum and Technical meeting on Reducing Salt Intake in Populations (Paris 5-7th October 2006) . (PDF; 2.2 MB).
  53. a b World Health Organization: Guideline: Potassium intake for adults and children. Geneva 2012. (PDF; 564 kB).
  54. ^ World Health Organization: Global Strategy on Diet, Physical Activity and Health. Population sodium reduction strategies . Retrieved December 13, 2013.
  55. Suter et al.: Nutritional factors in the control of blood pressure and hypertension. In: Nutr Clin Care. 5 (1), Jan-Feb 2002, pp. 9-19, PMID 12134718 .
  56. Tobian: Dietary sodium chloride and potassium have effects on the pathophysiology of hypertension in humans and animals. In: Am J Clin Nutr. 65 (2 Suppl), Feb 1997, pp. 606S-611S, PMID 9022555 .
  57. Bazzano et al: Dietary potassium intake and risk of stroke in US men and women: National Health and Nutrition Examination Survey I epidemiologic follow-up study. In: Stroke. 32 (7), Jul 2001, pp. 1473-1480, PMID 11441188 .
  58. Ascherio et al .: Intake of potassium, magnesium, calcium, and fiber and risk of stroke among US men. In: Circulation. 98 (12), 22 Sep 1998, pp. 1198-1204, PMID 9743511 .
  59. ^ Barri & Wingo: The effects of potassium depletion and supplementation on blood pressure: a clinical review. In: Am J Med Sci. 314 (1), Jul 1997, pp. 37-40, PMID 9216439 .
  60. Geleijnse et al .: Electrolytes are associated with blood pressure at old age: the Rotterdam Study. In: J Hum Hypertens. 11 (7), Jul 1997, pp. 421-423, PMID 9283057 .
  61. Khaw & Barrett-Connor: Dietary potassium and blood pressure in a population. In: Am J Clin Nutr. 39 (6), Jun 1984, pp. 963-968, PMID 6720624 .
  62. Khaw & Barrett-Connor: Dietary fiber and reduced ischemic heart disease mortality rates in men and women: a 12-year prospective study. In: Am J Epidemiol. 126 (6), Dec 1987, pp. 1093-1102, PMID 2825519 .
  63. Siani et al .: Controlled trial of long term oral potassium supplements in patients with mild hypertension. In: Br Med J (Clin Res Ed). 294 (6585), Jun 6, 1987, pp. 1453-1456, PMID 3300841 .
  64. Svetkey include: Double-blind, placebo-controlled trial of potassium chloride in the treatment of mild hypertension. In: Hypertension. 9 (5), May 1987, pp. 444-450, PMID 3570421 .
  65. Sacks et al .: Effects on blood pressure of reduced dietary sodium and the Dietary Approaches to Stop Hypertension (DASH) diet. DASH-Sodium Collaborative Research Group. In: N Engl J Med . 344 (1), Jan 4, 2001, pp. 3-10, PMID 11136953 .
  66. Vollmer et al .: New insights into the effects on blood pressure of diets low in salt and high in fruits and vegetables and low-fat dairy products. In: Curr Control Trials Cardiovasc Med. 2 (2), 2001, pp. 71-74, PMID 11806776 .
  67. Zemel: Dietary pattern and hypertension: the DASH study. Dietary Approaches to Stop Hypertension. In: Nutr Rev. 55 (8), Aug 1997, pp. 303-305, PMID 9287480 .
  68. Federal Institute for Risk Assessment: Use of Minerals in Food.
  69. European Food Safety Authority: EFSA Journal. 8 (2), 2010, p. 1469.
  70. Harrington, Cashman: High salt intake appears to increase bone resorption in postmenopausal women but high potassium intake ameliorates this adverse effect. In: Nutr Rev. 61 (5 Pt 1), May 2003, pp. 179-183, PMID 12822707 .
  71. Lemann et al .: Potassium administration reduces and potassium deprivation increases urinary calcium excretion in healthy adults. In: Kidney Int. 39 (5), May 1991, pp. 973-983, PMID 1648646 .
  72. New et al .: Lower estimates of net endogenous non-carbonic acid production are positively associated with indexes of bone health in premenopausal and perimenopausal women. In: Am J Clin Nutr. 79 (1), Jan 2004, pp. 131-138. PMID 14684409 .
  73. Barzel: The skeleton as an ion exchange system: implications for the role of acid-base imbalance in the genesis of osteoporosis. In: J Bone Miner Res . 10 (10), Oct 1995, pp. 1431-1436, PMID 8686497 .
  74. ^ Frassetto et al .: Effect of age on blood acid-base composition in adult humans: role of age-related renal functional decline. In: Am J Physiol. 271 (6 Pt 2), Dec 1996, pp. F1114-F1122, PMID 8997384 .
  75. Lemann: Relationship between urinary calcium and net acid excretion as determined by dietary protein and potassium: a review. In: Nephron. 81 Suppl 1, 1999, pp. 18-25, PMID 9873210 .
  76. ^ Massey: Dietary animal and plant protein and human bone health: a whole foods approach. In: J Nutr. 133 (3), Mar 2003, pp. 862S-865S, PMID 12612170 .
  77. Morris et al.: Differing effects of supplemental KCl and KHCO 3 : pathophysiological and clinical implications. In: Semin Nephrol. 19 (5), Sep 1999, pp. 487-493, PMID 10511388 .
  78. ^ Remer and Manz: Don't forget the acid base status when studying metabolic and clinical effects of dietary potassium depletion. In: J Clin Endocrinol Metab. 86 (12), Dec 2001, pp. 5996-5997, PMID 11739479 .
  79. ^ Remer: Influence of diet on acid-base balance. In: Semin Dial. 13 (4), Jul-Aug 2000, pp. 221-226, PMID 10923348 .
  80. a b S. Jehle et al .: Partial neutralization of the acidogenic western diet with potassium citrate increases bone mass in postmenopausal women with osteopenia. In: J Am Soc Nephrol. 17, 2006, pp. 3213-3222, PMID 17035614 .
  81. M. Marangella et al .: Effects of potassium citrate supplementation on bone metabolism. In: Calcif Tissue Int. 74, 2004, pp. 330-335, PMID 15255069 .
  82. DE Sellmeyer et al .: Potassium citrate prevents increased urine calcium excretion and bone resorption induced by a high sodium chloride diet. In: J Clin Endocrinol Metab. 87, 2002, pp. 2008-2012, PMID 11994333 .
  83. USDA National Nutrient Database for Standard Reference, Release 24 Content of Selected Foods per Common Measure, Potassium, K (mg) sorted by nutrient content ( Memento of April 5, 2013 in the Internet Archive ) (PDF; 150 kB).
  84. dried apricot . Website of the German Nutrition Advice and Information Network. Retrieved October 21, 2012.
  85. Low-Potassium Diet - Practical Tips .
  86. Federal Office for Radiation Protection: Which radionuclides are found in food? Retrieved August 19, 2014.
  87. ^ C. Michael Lederer, Jack M. Hollander, Isadore Perlman : Table of isotopes, John Wiley & Sons , New York, 1967.
  88. Potassium-40 - with a half-life of 1.28 billion years, long-lived and radioecologically relevant
  89. Live Chart - Table of nuclides - Nuclear structure and decay data. Retrieved February 11, 2020 .
  90. Table of nuclides. Retrieved February 11, 2020 .
  91. ^ Andreas Hermann: Elements can be solid and liquid at the same time. In: News - University of Edinburgh . April 9, 2019, accessed April 10, 2019 .
  92. ^ A b Karl Cammann (ed.): Instrumental analytical chemistry. Spektrum, Heidelberg 2001, ISBN 3-8274-0057-0 , pp. 4-60.
  93. ^ AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 102nd edition. Walter de Gruyter, Berlin 2007, ISBN 978-3-11-017770-1 , p. 1286.
  94. ^ A b A. F. Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 101st edition. Walter de Gruyter, Berlin 1995, ISBN 3-11-012641-9 , p. 1176.
  95. Entry on potassium chloride in the GESTIS substance database of the IFA , accessed on December 17, 2019(JavaScript required) .
  96. S.-P. Ballstaedt, P. Reinhard, M. Rentschler, E. Rottländer, AA Bodenstedt, D. Briesen, A. Bruckhaus, J. Büschenfeld, A. Hauptmann, DA Hiller: Change of soils through anthropogenic influences: An interdisciplinary study book , Verlag Springer Berlin Heidelberg, 1997, ISBN 3-540-61556-3
  97. ^ AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 101st edition. Walter de Gruyter, Berlin 1995, ISBN 3-11-012641-9 , p. 1170.
  98. Entry on potassium hydroxide in the GESTIS substance database of the IFA , accessed on December 17, 2019(JavaScript required) .
  99. Y. Idemoto, JW Richardson, N. Koura, S. Kohara, CK Loong: Crystal structure of (Li x K 1-x ) 2 CO 3 (x = 0,0.43,0.5,0.62,1) by neutron powder diffraction analysis. In: Journal of Physics and Chemistry of Solids , 59, 1998, pp. 363-376, doi: 10.1016 / S0022-3697 (97) 00209-6 .
  100. JK Brandon, ID Brown: An accurate determination of the crystal structure of triclinic potassium dichromate, K 2 Cr 2 O 7 . In: Canadian Journal of Chemistry . tape 46 , no. 6 , March 15, 1968, p. 933-941 , doi : 10.1139 / v68-155 ( PDF ).
  101. Axel Trautmann, Jörg Kleine-Tebbe: Allergology in Clinic and Practice Allergens - Diagnostics - Therapy . Georg Thieme Verlag, 2013, ISBN 978-3-13-159352-8 , p. 227 ( limited preview in Google Book search).
  102. Hans-Dieter Jakubke, Ruth Karcher (Ed.): Lexicon of Chemistry , Spectrum Academic Publishing House, Heidelberg, 2001.

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