Potassium chlorate

Potassium chlorate

Names
Other names Potassium chlorate(V), Potcrate
Identifiers
CAS Number	3811-04-9 Y
ChemSpider	18512 Y
EC Number	223-289-7
Jmol 3D model	Interactive image
PubChem	6426889
RTECS number	FO0350000
UNII	H35KS68EE7 Y
UN number	1485
InChI InChI=1S/ClHO3.K/c2-1(3)4;/h(H,2,3,4);/q;+1/p-1 Y Key: VKJKEPKFPUWCAS-UHFFFAOYSA-M Y InChI=1/ClHO3.K/c2-1(3)4;/h(H,2,3,4);/q;+1/p-1 Key: VKJKEPKFPUWCAS-REWHXWOFAC
SMILES [K+].[O-]Cl(=O)=O
Properties
Chemical formula	KClO3
Molar mass	122.55 g mol−1
Appearance	white crystals or powder
Density	2.32 g/cm3
Melting point	356 °C (673 °F; 629 K)
Boiling point	400 °C (752 °F; 673 K) decomposes
Solubility in water	3.13 g/100 mL (0 °C) 4.46 g/100 mL (10 °C) 8.15 g/100 mL (25 °C) 13.21 g/100 mL (40 °C) 53.51 g/100 mL (100 °C) 183 g/100 g (190 °C) 2930 g/100 g (330 °C)
Solubility	soluble in glycerol negliglble in acetone, liquid ammonia
Solubility in glycerol	1 g/100 g (20 °C)
Refractive index (nD)	1.40835
Structure
Crystal structure	monoclinic
Thermochemistry
Specific heat capacity (C)	100.25 J/mol·K
Std molar entropy (So298)	142.97 J/mol·K
Std enthalpy of formation (ΔfHo298)	−391.2 kJ/mol
Gibbs free energy (ΔfG˚)	-289.9 kJ/mol
Vapor pressure	{{{value}}}
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 otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y verify (what is YN ?)
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

• as an oxidizing agent,
• to prepare oxygen,
• as a disinfectant,
• in safety matches,
• in explosives and fireworks,
• in cultivation, forcing the blossoming stage of the Longan tree, causing it to produce fruit in warmer climates.

Production

On the industrial scale, potassium chlorate is produced by the Liebig process: passing chlorine into hot calcium hydroxide, subsequently adding potassium chloride: .

6Ca(OH)₂ + 6Cl₂ -> Ca(ClO₃)₂ + 5CaCl₂ + 6H₂O

Ca(ClO₃)₂ + 2KCl -> 2KClO₃ + CaCl₂

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:

3 NaClO → 2NaCl + NaClO₃

KCl + NaClO₃ → NaCl + KClO₃

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

3 Cl_2(g) + 6 KOH_(aq) → KClO_3(aq) + 5 KCl_(aq) + 3 H₂O_(l)

Uses

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.

Another application of potassium chlorate is as the oxidizer in a smoke composition such as that used in 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.

Potassium chlorate is often used in high school and college laboratories to generate oxygen gas. 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 KClO_3(s) → 3 O_2(g) + 2 KCl_(s)

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

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.

In chemical labs it is used to oxidize HCl and release small amounts of gaseous chlorine.

Insurgents in Afghanistan also use potassium chlorate extensively as a key component in the production of improvised explosive devices. When significant effort was made to reduce the availability of ammonium nitrate fertilizer in Afghanistan, IED makers started using potassium chlorate as a cheap and effective alternative. In 2013, 60% of IEDs in Afghanistan used potassium chlorate, making it the most common ingredient used in IEDs.

Safety

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

• Chloric acid

References

• "Chlorate de potassium. Chlorate de sodium", Fiche toxicol. n° 217, Paris:Institut national de recherche et de sécurité, 2000. 4pp.
• Continuous process for the manufacture of potassium chlorate by coupling with a sodium chlorate production plant