Potassium perchlorate

Potassium perchlorate
Other names Potassium chlorate(VII) Perchloric acid, potassium salt peroidin
Identifiers
CAS number	7778-74-7 Y
PubChem	516900
ChemSpider	22913 Y
UNII	42255P5X4D Y
EC number	231-912-9
UN number	1489
ChEMBL	CHEMBL1200696 N
RTECS number	SC9700000
Jmol-3D images	Image 1
SMILES [K+].[O-]Cl(=O)(=O)=O
InChI InChI=1S/ClHO4.K/c2-1(3,4)5;/h(H,2,3,4,5);/q;+1/p-1 Y Key: YLMGFJXSLBMXHK-UHFFFAOYSA-M Y InChI=1/ClHO4.K/c2-1(3,4)5;/h(H,2,3,4,5);/q;+1/p-1 Key: YLMGFJXSLBMXHK-REWHXWOFAB
Properties
Molecular formula	KClO4
Molar mass	138.55 g/mol
Appearance	Colourless/white crystalline powder
Density	2.5239 g/cm3
Melting point	525 °C
Boiling point	600 °C (decomp.)
Solubility in water	0.75 g/100 mL (0 °C) 1.5 g/100 mL (25 °C)[1] 21.8 g/100 mL (100 °C)
Solubility	negligible in alcohol insoluble in ether
Refractive index (nD)	1.4724
Structure
Crystal structure	rhombohedral
Thermochemistry
Std enthalpy of formation ΔfHo298	−433 kJ·mol−1[2]
Standard molar entropy So298	151 J·mol−1·K−1[2]
Hazards
MSDS	MSDS
EU Index	017-008-00-5
EU classification	Oxidant (O) Harmful (Xn)
R-phrases	R9, R22
S-phrases	(S2), S13, S22, S27
NFPA 704	0 1 1 OX
Related compounds
Other anions	Potassium chloride Potassium chlorate Potassium periodate
Other cations	Ammonium perchlorate Sodium perchlorate
N (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
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 It has been used as a solid rocket propellant, although in that application it has mostly been replaced by the higher performance ammonium perchlorate.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

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).^[3]

Oxidizing properties

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.^[4]

In medicine

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.

References

External links

• WebBook page for KClO₄