Kalium (K)

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Kalium 19K39.098

1807 von Sir Humphry Davy in London, UK, entdeckt.

[English, potash; Lateinisch, kalium]

French: potassium
English: potassium
Italian: potassio
Spanish: potasio


Beschreibung: Weiches, weißes Metall, Schnittflächen silbern, reagiert aber schnell mit Sauerstoff und heftig mit Wasser. Man erhält es aus Na + KCl bei 1100 K. Verwendet in Düngemittel.

  

Further Materials properties

 

Crystal structure:

(cell dimensions/pm), space group, 
b.c.c. (a=533.4), Im3m
X-ray diffractions mass absorption coefficients: CuKa 143 (µ/r) / cm2g-1
MoKa 15.8 (µ/r) / cm2g-1
Neutron scattering length: 0.367 b/10-12 cm
Thermal neutron capture cross-section: 2.1 sa / barns
Density: 862 kg/m-3 [293 K]; 828 [liquid at m.p.]
Melting point: 63.65°C / 336.8°K
Boiling point: 773.85°C / 1047°K
Molar volume: 45.36 cm3
Thermal conductivity: 102.4 [300 K] W m-1K-1
Coefficient of linear thermal expansion: 83 x 10-6 K-1
Electrical resistivity: 6.15 x 10-8 [273 K] Ωm
Mass magnetic susceptibility: +6.15 x 10-8(s) kg-1m3
Radi: K+ 133; atomic 227; covalent 203; van der Waals 231
Electronegativity: 0.82 (Pauling); 0.91 (Allred); 2.42 eV (absolute)
Effective nuclear charge: 2.20 (Slater); 3.50 (Clementi); 4.58 (Froese-Fischer)
Number of Isotopes (incl. nuclear isomers): 18
Isotope mass range: 35-> 51

 

 

Biological data

 

Biological role: Essential to all living things.
Toxicity
Toxic intake: KCl = c. 4g
Lethal intake: LD50 (chloride, oral, rat) = 2600 mg Kg-1
Hazards: The toxicity of potassium compounds is almost always that of the anion, not of the K+. However, although KCl is often used as a nutrient or dietary supplement, there are rare cases of excess ingestion by humans proving fatal.
Level in humans
Blood: 16020 mg dm-3
Bone: 2100 ppm
Liver: 16 000 ppm
Muscle: 16 000 ppm
Daily dietary intake: 1400 - 7400 mg
Total mass of element in average
[70 kg] person:		 140 g

 

Geological data

 

Minerals:Potassium occurs in many minerals.
MineralFormulaDensityHardnessCrystal apperance
Alunite KAl3(SO4)2(OH)6 2.69  3.5 - 4  rhom., vit. white/grey
Carnallite KCl.MgCl2.6H2O 1.602  2.5  orth., greasy colourless-red
Orthoclase* KAlSi3O8 2.563  6 - 6.5  mon., vit. colourless/ white
Sylvite KCl 1.993  2  cub., vit. colourless/white

* Mined on a large scale for porcelain, ceramics and glass

Chief ores: sylvite, carnallite, alunite
World production: 200 (potassium metal); 51 x 106 (potassium salts) tonnes/year
Producing areas: Germany, Spain, Canada, USA, Italy
Reserves: vast, > 1 x 1010 tonnes
Specimen: available as chunks (in mineral oil) or ingots (in ampoules). Warning!

 

Abundances  
Sun: 1.45 x 105  (relative to H = 1 x 1012)
Earth's crust: 21 000 ppm
Residence time: 5 x 106 years
Classification: accumulating
Oxidation state: I

  Source: Emsley, J. (1998) The Elements (3rd Edition)

Other sizes and specifications on request


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