Potassium perchlorate

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Potassium perchlorate
Potassium perchlorate.png
Potassium-perchlorate-unit-cell-3D-balls-perspective.png Potassium-perchlorate-xtal-3D-SF.png
Potassium perchlorate 200g.jpg
Identifiers
CAS number 7778-74-7 YesY
PubChem 516900
ChemSpider 22913 YesY
UNII 42255P5X4D YesY
EC number 231-912-9
UN number 1489
ChEMBL CHEMBL1200696 N
RTECS number SC9700000
Jmol-3D images Image 1
Properties
Molecular formula ClKO4
Molar mass 138.55 g mol−1
Appearance colourless/ white crystalline powder
Density 2.5239 g/cm3
Melting point 610 °C (1,130 °F; 883 K)
decomposes from 400 °C[4][5]
Solubility in water 0.76 g/100 mL (0 °C)
1.5 g/100 mL (25 °C)[1]
4.76 g/100 mL (40 °C)
21.08 g/100 mL (100 °C)[2]
Solubility product, Ksp 1.05·10-2[3]
Solubility negligible in alcohol
insoluble in ether
Solubility in ethanol 47 mg/kg (0 °C)
120 mg/kg (25 °C)[2]
Solubility in acetone 1.6 g/kg[2]
Solubility in ethyl acetate 15 mg/kg[2]
Refractive index (nD) 1.4724
Structure
Crystal structure Rhombohedral
Thermochemistry
Specific
heat capacity
C
111.35 J/mol·K[6]
Std molar
entropy
So298
150.86 J/mol·K[6]
Std enthalpy of
formation
ΔfHo298
-433 kJ/mol[7]
Gibbs free energy ΔG -300.4 kJ/mol[2]
Hazards
MSDS MSDS
GHS pictograms The flame-over-circle pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)The exclamation-mark pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)[5]
GHS signal word Danger
GHS hazard statements H271, H302[5]
GHS precautionary statements P220[5]
EU Index 017-008-00-5
EU classification Oxidizing Agent O Harmful Xn
R-phrases R9, R22
S-phrases (S2), S13, S22, S27
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 1: Exposure would cause irritation but only minor residual injury. E.g., turpentine Reactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g., calcium Special hazard OX: Oxidizer. E.g., potassium perchlorateNFPA 704 four-colored diamond
Related compounds
Other anions Potassium chloride
Potassium chlorate
Potassium periodate
Other cations Ammonium perchlorate
Sodium perchlorate
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N (verify) (what is: YesY/N?)
Infobox references

Potassium perchlorate is the inorganic salt with the chemical formula KClO4. Like other perchlorates, this salt is a strong oxidizer and potentially reacts with many organic substances. This usually obtained as a colorless, crystalline solid is a common oxidizer used in fireworks, ammunition percussion caps, explosive primers, and is used variously in propellants, flash compositions, stars, and sparklers. It has been used as a solid rocket propellant, although in that application it has mostly been replaced by the higher performance ammonium perchlorate. KClO4 has the lowest solubility of the alkali metal perchlorates (1.5 g in 100 mL of water at 25 °C).[1]

Production[edit]

Potassium perchlorate in crystal form

KClO4 is prepared industrially by treating an aqueous solution of sodium perchlorate with KCl. This single precipitation reaction exploits the low solubility of KClO4, which is about 100 times less than the solubility of NaClO4 (209.6 g/100 mL at 25 °C).[8]

Oxidizing properties[edit]

KClO4 is an oxidizer in the sense that it exothermically transfers oxygen to combustible materials, greatly increasing their rate of combustion relative to that in air. Thus, with glucose it gives carbon dioxide:

3 KClO4 + C6H12O6 → 6 H2O + 6 CO2 + 3 KCl

The conversion of solid glucose into hot gaseous CO2 is the basis of the explosive force of this and other such mixtures. Even with cane sugar, KClO4 yields a low explosive, provided the necessary confinement. Otherwise such mixtures simply deflagrate with an intense purple flame characteristic of potassium. Flash compositions used in firecrackers usually consist of fine aluminium powder mixed with potassium perchlorate.

As an oxidizer, potassium perchlorate can be used safely in the presence of sulfur, whereas potassium chlorate cannot. The greater reactivity of chlorate is typical – perchlorates are kinetically poorer oxidants. Chlorate produces chloric acid, which is highly unstable and can lead to premature ignition of the composition. Correspondingly, perchloric acid is quite stable.[9]

In medicine[edit]

Potassium perchlorate can be used as an antithyroid agent used to treat hyperthyroidism, usually in combination with one other medication. This application exploits the similar ionic radii and hydrophilicity of perchlorate and iodide.

Other Uses[edit]

Since 2005, a cartridge with potassium perchlorate mixed with anthracene and sulfur is used for generating the black smoke signalling the failure of reaching a two-thirds majority needed for the election of new pope by a papal conclave.

References[edit]

  1. ^ a b "Potassium Perchlorate MSDS". J.T. Baker. 2007-02-16. Retrieved 2007-12-10. 
  2. ^ a b c d e http://chemister.ru/Database/properties-en.php?dbid=1&id=519
  3. ^ http://www.solubilityofthings.com/water/ions_solubility/ksp_chart.php
  4. ^ Benenson, Walter; Stöcker, Horst. Handbook of Physics. Springer. p. 780. ISBN 0387952691. 
  5. ^ a b c d Sigma-Aldrich Co., Potassium perchlorate. Retrieved on 2014-05-27.
  6. ^ a b Potassium perchlorate in Linstrom, P.J.; Mallard, W.G. (eds.) NIST Chemistry WebBook, NIST Standard Reference Database Number 69. National Institute of Standards and Technology, Gaithersburg MD. http://webbook.nist.gov (retrieved 2014-05-27)
  7. ^ Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. p. A22. ISBN 0-618-94690-X. 
  8. ^ Helmut Vogt, Jan Balej, John E. Bennett, Peter Wintzer, Saeed Akbar Sheikh, Patrizio Gallone “Chlorine Oxides and Chlorine Oxygen Acids” in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH. doi:10.1002/14356007.a06_483
  9. ^ Greenwood, N. N.; Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.), Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4.

External links[edit]