Potassium nitrate
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 (American English saltpeter), Chilean saltpetre, and nitre.
The name "saltpeter" is also applied to sodium Nitrate.
It is the oxidising component of gunpowder. Prior to the large-scale industrial fixation of nitrogen (the Haber process), a major source of saltpetre was the deposits crystallising from the drainings of dung-heaps; thereby making dung-heaps a valuable military resource.
An urban legend holds that soldiers, sailors, and other young men in institutional situations are secretly administered saltpetre in their food, especially during bootcamp, to suppress their sexual urges. It is conjectured that the troops were employing a folk etymology and replacing "salt" with "soft". The reduction in sexual urges does in fact occur, but is caused by physical exhaustion related to intense training.
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.
More info
Hazardous Chemical Database (http://ull.chemistry.uakron.edu/erd/chemicals/7/6965.html)
SI units were used where possible. Unless otherwise stated, standard conditions were used.