Science Fair Project Encyclopedia
Potassium nitrate
|
General |
|
|---|---|
| Name | Potassium nitrate |
| Chemical formula | KNO3 |
| Appearance | White or dirty gray solid |
|
Physical |
|
| Formula weight | 101.1 amu |
| Melting point | 607 K (334 °C) |
| Boiling point | decomposes at 673 K (400 °C) |
| Density | 2.1 ×103 kg/m3 |
| Crystal structure | Aragonite |
| Solubility | 38 g in 100g water |
|
Thermochemistry |
|
| ΔfH0gas | ? kJ/mol |
| ΔfH0liquid | -483 kJ/mol |
| ΔfH0solid | -495 kJ/mol |
| S0gas, 1 bar | ? J/mol·K |
| S0liquid, 1 bar | ? J/mol·K |
| S0solid | ? J/mol·K |
|
Safety | |
| Ingestion | May cause GI irritation, nausea, vomiting, diarrhea. |
| Inhalation | Irritation, long term exposure may be fatal. |
| Skin | Low hazard. |
| Eyes | Low hazard. |
|
SI units were used where possible. Unless otherwise stated, standard conditions were used. | |
The chemical compound potassium nitrate is a naturally occurring mineral source of nitrogen. It is a nitrate with chemical formula KNO3.
Its common names include saltpetre (from Medieval Latin sal petrae: "stone salt" or possibly "salt of Petra"), American English saltpeter, Chilean saltpetre, Nitrate of potash and nitre. The name saltpeter is also applied to sodium nitrate.
It is the oxidising (oxygen-supplying) component of gunpowder. Prior to the large-scale industrial fixation of nitrogen (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.
Historically, nitre-beds were prepared by mixing manure with either mortar or wood ashes, common earth and organic material 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.
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.
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.
A popular misconception is that potassium nitrate is an anaphrodisiac and was added to food in all-male institutions. In fact potassium nitrate has no such effect in humans. [1]
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