Potassium nitrate

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The chemical compound potassium nitrate is a naturally occurring mineral source of nitrogen. It is a nitrate with chemical formula K N O₃. When it burns, it burns a bright pink to purple color.

Its common names include saltpetre (from Medieval Latin sal petrae: "stone salt" or possibly "Salt of Petra"), American English saltpeter, Nitrate of potash and nitre. The name saltpeter is also applied to sodium nitrate.

1 Description
2 Manufacture
3 Applications
4 See also
5 External links

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Description

Potassium nitrate is the oxidizing (oxygen-supplying) component of black powder. Prior to the large-scale industrial fixation of nitrogen through the Haber process, a major source of Potassium nitrate was the deposits crystallising from cave walls or the drainings of decomposing organic material. Dung-heaps were a particularly common source: ammonia from the decomposition of urea and other nitrogenous materials would undergo bacterial oxidation to produce nitrate. It was and is also used as a component in some fertilizers. When used by itself as a fertilizer, it has an NPK rating of 13-0-44.

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Manufacture

Historically, nitre-beds were prepared by mixing manure with either mortar or wood ashes, common earth and organic materials such as straw to give porosity to a compost pile typically 1.5 metres high by 2 metres wide by 5 metres long. The heap was usually under a cover from the rain, kept moist with urine, turned often to accelerate the decomposition and leached with water after approximately one year. The liquid containing various nitrates was then converted with wood ashes to potassium nitrates, crystallized and refined for use in gunpowder.

In England, the privilege of manufacturing explosives had been in the hands of the family of John Evelyn, the celebrated diarist, as a crown monopoly since before 1588.

Today, most potassium nitrate comes from the vast deposits of sodium nitrate (NaNO₃, nitratine) in the Chilean deserts. The sodium nitrate is purified and then reacted in solution with potassium chloride (KCl, sylvite), from which the less-soluble potassium nitrate is precipitated out.

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Applications

One of the most useful applications of potassium nitrate is in the production of nitric acid, by adding concentrated sulfuric acid to an aqueous solution of potassium nitrate, yielding nitric acid and potassium sulfate which are separated through fractional distillation.

Potassium nitrate is also used as a fertilizer, as a model rocket propellant, and in several fireworks such as smoke bombs, in which a mixture with sugar produces a smoke cloud of 600 times their own volume. In the process of food preservation, potassium nitrate is a common ingredient of salted meat, but heart patients need take care with it. Potassium Nitrate is also a main component in stump remover; it accelerates the natural decomposition of the stump. It has also been used in the manufacture of ice cream and can be found in some toothpastes for sensitive teeth.

A popular misconception is that potassium nitrate is an antaphrodisiac and was added to food in all-male institutions. In fact potassium nitrate has no such effect in humans. [1]

Recently, the use of potassium nitrate in toothpastes for sensitive teeth has increased dramatically, despite the fact that it has not been shown to actually help dental hypersensitivity. [2]

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