It is a alkaline Métal soft, of metal aspect Blanc (slightly bluish) that one finds naturally related to other elements in sea water and many minerals. It oxidizes quickly in contact with the Air and reacts violently with the Eau. It resembles the Sodium chemically.
HistoryPotassium was discovered in 1807 by sir Humphry Davy, who obtains it by electrolysis hydroxide of potassium, and forges the word starting from English potash , potass “potash” and of the suffix - ium .
Potassium was the first metal isolated by electrolysis.
CharacteristicsPotassium is the lighter second, most reactive, more electropositive of metals. It is a soft solid which is easily cut using a knife. Coldly cut surfaces have a metal aspect. It oxidizes quickly with the air and must thus be preserved in oil.
Like other alkaline metals, water breaks up with its contact with hydrogen formation. When it is plunged in water, it reacts violently by producing hydrogen which can ignite, even explode, in the presence of oxygen and of a point to high temperature.
Its salts emit a color violet when they are exposed to a flame.
One knows the existence of 24 isotopes of potassium:
the marked values of one # are values of prediction.
values of spin to weak certainty as well as uncertainties
for the last figures is indicated in brackets.
The natural shape of potassium is composed of the 3 isotopes 39K (93,26%), 40K (0,01167%) and 41K (6,73%).
The 40K disintegrates:
- by orbital electron capture and emission ß+ in 40 Ar;
- by emission ß- in 40 Ca
The method of Datation to potassium-argon (couple of isotopes 40K - 40Ar) is commonly used for the dating of the rocks.
The ion potassiumIt is a large cation (~140 pm) little coordinant and thus difficult to precipitate in aqueous solution. It forms complexes with the ethers crowns what makes it possible to solubilize some of its salts in organic solution.
LayersThis element accounts for approximately 2,58% of the total weight of the Earth's crust, of which it is one of the 7 most abundant elements.
Potassium is not in a native state in nature. It is obtained mainly by electrolysis of the potassium hydroxide by a process which changed very little since Davy.
Minerals such as the Carnallite KMgCl3·6H2O, the Langbeinite K2Mg2 (SO4) 3, the Polyhalite K2Ca2Mg (SO4) 4·2H2O, and the Sylvite KCl, which one finds at the bottom of the old lakes and seas are important potassium ores, and allow its economic exploitation.
The oceans constitute an important potassium reserve, but its concentration is weaker there than that of sodium (cf Sea water).
synthesis of potassiumPotassium is produced by liquid reduction of KCl by sodium vapor with 870°C then distillation.
Use of potassium
Applications of metal potassium
- metal potassium is used as reagent in many reactions of fine chemistry and pharmacy, where one uses it in particular for his properties of powerful Réducteur (action similar to that of the metal Sodium).
- the NAK is a Alliage of Sodium and potassium used in the transfers of heat.
Composed of potassiumPotassium is an essential component for the growth of the plants; one finds it (in the form of made up) in the majority of the grounds. Potassium is vital for the operation of the animal cells (see pump NAK).
Its principal compounds:
- the Hydroxide of more known potassium under the name of potash caustic or Potash , and used for the manufacture of products Detergent S;
- the Chlorure of potassium is used like substitute of the food Sel, and also to stop the Cœur in the executions by lethal injection;
- the nitrate of potassium is the Salpêtre or niter, used in the Gunpowder;
- the Carbonate of potassium is used in the manufacture of glass, and is the principal one constituting potash (fertilizer);
- other important potassium salts:
- the Potassium bromide,
- the Iodide of potassium,
- the Phosphate of potassium,
- the Sulfate of potassium.
PrecautionsPotassium in the form of metal reacts violently with water. Potassium can also react violently with its own oxide; for example a shock on an oxidized potassium casting can cause an explosion. This metal must thus be preserved safe from water and any atmosphere oxidizing or responsible for moisture. It generally is preserved immersed in oil or surrounded by grease.
Nutrition and medicinePotassium is a Micronutriment essential with the human consumption. 2004 guidelines off the Institute off Medicine specify year GDR off 4,700 Mg off potassium. However, it is thought that most Americans consumes only half that amount per day (). Similarly, in the European Union, particularly in Germany and Italy, insufficient potassium intake is widespread ().
Supplements off potassium in medicine are most widely used in conjunction with the most powerful classes off diuretics, which rid the body off sodium and toilets, goal cuts the side effect off also causing potassium loss in urine. With variety off medical supplements are available.
Summon people with broad Kidney disease are advised to avoid off quantities dietary potassium. End renal training course failure patient undergoing therapy by Renal dialysis must observes strict dietary limits one potassium intake, since the kidneys control potassium excretion, and buildup off blood concentrations off fatal potassium may trigger heart dysrhythmias. -->
Potassium in its form of Cation K+ is the intracellular main thing Ion of the organization. There exists a gradient of concentration in favor of the exit of the ion since the intracellular compartment towards the extracellular compartment. This gradient is maintained by pumps located in the cellular membranes, in particular the Pompe sodium/potassium is responsible for the existence of a Potentiel of rest negative present in all the alive cells.
The plasmatic concentration of K+ (or Kaliémie) is very finely controlled, in particular on the level of the Rein, so that this rate remains in a precise fork from 3 to 4,5 mmol/l. The pathological variations of the kaliemy (Hypokaliémie and especially Hyperkaliémie) are severe disorders likely to involve cardiac anomalies fatal.
A varied food constitutes the best means of having a good potassium rate in the organization. Orange juice, Potato be, Banana S, Avocado S, Parsnip S and Turnip S, although many other Fruit S, Vegetable S, and meatuses contain potassium. --> Of research highlighted that a mode rich in potassium can reduce the risks of Hypertension.
One finds good quantities of potassium in the Pruneau (732 mg/100g), the Châtaigne S (600mg/100g), the lawyer (485 mg/100g), the spinach S (466 mg/100g), the Potato (379 mg/100g) and the Tubercule S in general (the Céleri-rave, the Navet), the Banane (358 mg/100g), the Carotte (320 mg/100g) and the Jus of orange (200 mg/100g).
Radioactivity in the human body due to the 40K
Knowing ( has ) the quantié total one of potassium in an human body, ( B ) the Abondance natural of 40K present in the Biosphère and ( C ) the radioactive Half-life of this one, it is easy to calculate the number of disintegrations a second (Bq) which take place there.
(A) total Quantity of potassium in an human body. This one is on average of 4216 ± 473 mmol (165 ± 18 G) for a man and of 4172 ± 540 mmol (163 ± 31 G) for a woman, but considering other parameters such as the age or the IMC can affect these values, a formula which takes account of these factors was developed as follows:
For a man:
KCT = (98.3 - 0.1594 X age + 0.1431 X weight - 0.1848 X cut) X MNG
For a woman:
KCT = (94.39 - 0.1735 X age + 0.1169 X weight - 0.1567 X cut) X MNG
Where KCT is total body potassium (in mmol), the age is in years, the weight in kg, the size in cm and MNG is the mass non fat substance (for example, for a body of 80 kg made up to 20% of grease, the MNG is worth 0.8 X 80 = 64 kg)
(b) the natural abondace of the 40K of 0,01167%, such as is indicated higher.
(c) the radioactive Half-life of the 40K (1,277×109 years) makes it possible to calculate for a given quantity of the Isotope (a mmol, is 6.022 X 1020 atoms), the number of disintegrations per unit of time (in Bq). In fact, a mmol of 40K will produce:
(6.022 X 1020 × ln2/(1,277×109 × 365.25 × 24 × 60 × 60) = 1,036 × 104 Bq
Finally, it is enough to multiply KCT × 0,0001167 × 1,036 ×104 to obtain the number of Bq produced by the 40K in an human body, which on average (values minimal and maximum of the KCT indicated higher) thus gives between 4390 and 5670 disintegrations a second (Bq). These values are to be compared with those given in example in the page of the Becquerel, where the values indicated for the human being hold account in a similar way of the others Isotopes naturally present in the body.
It should be noted that it is useless to want to measure this Radioactivité using a Geiger counter: the beta radiations less of the 40K cross only very little the matter such as that which constitutes the body liquids or the skin and are thus absorbed by the atoms of the surrounding molecules, which can then undergo ionizations. This measurement must thus be made by other methods such as by the Homogénéisation of the biological sample followed by detection of sound beta activity less by counting of scintillation. In the cells, the ionization of certain atoms due to the radioactivity of the 40K can cause the rupture of chemical bonds and lead to the free formation of Radicaux, which are generally detoxified by a variety of specialized enzymes. If ionization intervenes on atoms which constitute DNA Chromosomes, this can sometimes cause changes with the more or less serious consequences for the cell or the individual.
- Ferricyanide of potassium
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