Potassium chlorate

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Potassium chlorate
The structure of the ions in potassium chlorate
The crystal structure of potassium chlorate
Potassium chlorate crystals
Identifiers
CAS number 3811-04-9 YesY
PubChem 6426889
ChemSpider 18512 YesY
UNII H35KS68EE7 YesY
EC number 223-289-7
UN number 1485
RTECS number FO0350000
Jmol-3D images Image 1
Properties
Molecular formula KClO3
Molar mass 122.5495 g/mol
Appearance White crystals or powder
Density 2.34 g/cm3
Melting point 356 °C (673 °F; 629 K)
Boiling point 400 °C (752 °F; 673 K) (decomposes)
Solubility in water 3.25 g/100 mL (0 °C)
7.19 g/100 ml (20 °C)
8.61 g/100 m: (25 °C)
57 g/100 mL (100 °C)
Solubility soluble in glycerol
negliglble in acetone, liquid ammonia
Refractive index (nD) 1.40835
Structure
Crystal structure monoclinic
Thermochemistry
Std molar
entropy
So298
143 J·mol−1·K−1[1]
Std enthalpy of
formation
ΔfHo298
−391 kJ·mol−1[1]
Hazards
MSDS ICSC 0548
EU Index 017-004-00-3
EU classification Oxidising agent O Dangerous for the Environment (Nature) N Harmful Xn
R-phrases R9, R22, R51/53
S-phrases (S2), S13, S16, S27, S61
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform Reactivity code 3: Capable of detonation or explosive decomposition but requires a strong initiating source, must be heated under confinement before initiation, reacts explosively with water, or will detonate if severely shocked. E.g., fluorine Special hazard OX: Oxidizer. E.g., potassium perchlorateNFPA 704 four-colored diamond
Flash point 400 °C (752 °F; 673 K)
LD50 1870 mg/kg (rat, oral)
Related compounds
Other anions Potassium bromate
Potassium iodate
Other cations Ammonium chlorate
Sodium chlorate
Barium chlorate
Related compounds Potassium chloride
Potassium hypochlorite
Potassium chlorite
Potassium perchlorate
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 YesY (verify) (what is: YesY/N?)
Infobox references

Potassium chlorate is a compound containing potassium, chlorine and oxygen atoms, with the molecular formula KClO3. In its pure form, it is a white crystalline substance. It is the most common chlorate in industrial use. It is used

Production[edit]

On the industrial scale, potassium chlorate is produced by passing chlorine into the hot milk of lime, subsequently adding the potassium chloride (Liebig process).[4] The electrolysis of KCl in aqueous solution is also used sometimes, in which the chloride ions formed at the anode react with KOH in situ. The low solubility of KClO3 in water causes the salt to conveniently isolate itself from the reaction mixture by simply precipitating out of solution.

Potassium chlorate can be produced in small amounts by disproportionation in a sodium hypochlorite solution followed by metathesis reaction with potassium chloride:[5]

3 NaClO → 2NaCl + NaClO3
KCl + NaClO3 → NaCl + KClO3

It can also be produced by passing chlorine gas into a hot solution of caustic potash:[6]

3Cl2(g) + 6KOH (aq) → KClO3 (aq) + 5KCl (aq) + 3H2O(l)

Uses[edit]

Potassium chlorate burning sugar

Potassium chlorate was one key ingredient in early firearms percussion caps (primers). It continues in that application, where not supplanted by potassium perchlorate.

Chlorate-based propellants are more efficient than traditional gunpowder and are less susceptible to damage by water. However, they can be extremely unstable in the presence of sulfur or phosphorus and are much more expensive. Chlorate propellants must be used only in equipment designed for them; failure to follow this precaution is a common source of accidents. Potassium chlorate, often in combination with silver fulminate, is used in trick noise-makers known as "crackers", "snappers", "pop-its", or "bang-snaps", a popular type of novelty firework.

When mixed with a suitable fuel, it may form an explosive material, a so-called Sprengel explosive. The hygroscopic and slightly stronger sodium chlorate is sometimes used as a safer and less expensive substitute for potassium chlorate. In World War I, mixes of potassium chlorate with plasticizers (such as wax) were the most common type of plastic explosive used, often filling grenades and other munitions. When used in explosives as an oxidizer, the explosive is low order meaning it burns rapidly rather than explodes. When mixed with a plasticizer, it may become high order, requiring a blasting cap (generally a commercial #8) to detonate properly. Potassium chlorate is rarely used in explosives now, as it is considered too sensitive for most uses.

Another application of potassium chlorate is as the oxidizer in a smoke composition such as used in, e.g., smoke grenades. Since 2005, a cartridge with potassium chlorate mixed with lactose and rosin is used for generating the white smoke signalling the election of new pope by a papal conclave.[7]

Potassium chlorate is often used in high school and college laboratories to generate oxygen gas.[citation needed] It is a far cheaper source than a pressurized or cryogenic oxygen tank. Potassium chlorate readily decomposes if heated while in contact with a catalyst, typically manganese (IV) dioxide (MnO2). Thus, it may be simply placed in a test tube and heated over a burner. If the test tube is equipped with a one-holed stopper and hose, warm oxygen can be drawn off. The reaction is as follows:

2 KClO3(s) → 3 O2(g) + 2KCl(s)

Heating it in the absence of a catalyst converts it into potassium perchlorate:[6]

4 KClO3 → 3 KClO4 + KCl

With further heating, potassium perchlorate decomposes to potassium chloride and oxygen:

KClO4 → KCl + 2 O2

The safe performance of this reaction requires very pure reagents and careful temperature control. Molten potassium chlorate is an extremely powerful oxidizer and spontaneously reacts with many common materials such as sugar. Explosions have resulted from liquid chlorates spattering into the latex or PVC tubes of oxygen generators, as well as from contact between chlorates and hydrocarbon sealing greases. Impurities in potassium chlorate itself can also cause problems. When working with a new batch of potassium chlorate, it is advisable to take a small sample (~1 gram) and heat it strongly on an open glass plate. Contamination may cause this small quantity to explode, indicating that the chlorate should be discarded.

Potassium chlorate is used in chemical oxygen generators (also called chlorate candles or oxygen candles), employed as oxygen-supply systems of e.g. aircraft, space stations, and submarines, and has been responsible for at least one plane crash. A fire on the space station Mir was also traced to this substance. The decomposition of potassium chlorate was also used to provide the oxygen supply for limelights.

Potassium chlorate is used also as a pesticide. In Finland it was sold under trade name Fegabit.

Potassium chlorate can react with sulfuric acid to form a highly reactive solution of chloric acid and potassium sulfate:

2 KClO3 + H2SO4 → 2 HClO3 + K2SO4

The solution so produced is sufficiently reactive that it spontaneously ignites if combustible material (sugar, paper, etc.) is present.

In schools, molten potassium chlorate is used in the dramatic screaming jelly babies demonstration.

Safety[edit]

Potassium chlorate should be handled with care. It reacts vigorously, and in some cases spontaneously ignites or explodes, when mixed with many combustible materials. It burns vigorously in combination with virtually any combustible material, even those normally only slightly flammable (including ordinary dust and lint). Mixtures of potassium chlorate and a fuel can ignite by contact with sulfuric acid, so it should be kept away from this reagent. Sulfur should be avoided in pyrotechnic compositions containing potassium chlorate, as these mixtures are prone to spontaneous deflagration. Most sulfur contains trace quantities of sulfur-containing acids, and these can cause spontaneous ignition - "Flowers of sulfur" or "sublimed sulfur", despite the overall high purity, contains significant amounts of sulfur acids. Also, mixtures of potassium chlorate with any compound with ignition promoting properties (ex. antimony(III) sulfide) are very dangerous to prepare, as they are extremely shock sensitive.

See also[edit]

References[edit]

  1. ^ a b Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. p. A22. ISBN 0-618-94690-X. 
  2. ^ "Afghan bomb makers shifting to new explosives for IEDs". usatoday.com. Retrieved 2013-06-25. 
  3. ^ Manochai, P.; Sruamsiri, P.; Wiriya-alongkorn, W.; Naphrom, D.; Hegele, M.; Bangerth, F. (February 12, 2005). "Year around off season flower induction in longan (Dimocarpus longan, Lour.) trees by KClO3 applications: potentials and problems". Scientia Horticulturae (Department of Horticulture, Maejo University, Chiang Mai, Thailand; Department of Horticulture, Chiang Mai University, Chiang Mai, Thailand; Institute of Special Crops and Crop Physiology, University of Hohenheim, 70593 Stuttgart, Germany) 104 (4): 379–390. Retrieved November 28, 2010. 
  4. ^ Реми, Г. Курс неорганической химиию, т. 1/Перевод с немецкого под ред. А. В. Новосёловой. Москва:Мир, 1972.- с. 770//(translated from:) Heinrich Remy. Lehrbuch der anorganischen Chemie. XI Auflage. Band 1. Leipzig:Geest & Portig K.-G., 1960.
  5. ^ http://chemistry.about.com/od/makechemicalsyourself/a/Potassium-Chlorate-From-Bleach-And-Salt-Substitute.htm
  6. ^ a b Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0-07-049439-8
  7. ^ Daniel J. Wakin and Alan Cowell (March 13, 2013). "New Round of Voting Fails to Name a Pope". The New York Times. Retrieved March 13, 2013.