Potassium Chlorate - Uses

Uses

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 weaker 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.

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 will readily decompose if heated 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:

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 will spontaneously react 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 will spontaneously ignite if combustible material (sugar, paper, etc.) is present.