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Potassium nitrate

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Potassium nitrate
Potassium nitrate Atomic Structure of Potassium Nitrate.png
Systematic name Potassium Nitrate
Other names Nitrate of potash - Saltpetre
Molecular formula KNO3
Molar mass 101.1032 g/mol101.103 amu
Appearance White Solid
CAS number 7757-79-1
Density and phase 2.11 g/cm32.11 g/ml, Solid
Solubility in water 35.7 g/100 ml (25°C)
Melting point 334°C607.15 K
633.2 °F
1,092.87 °R
Boiling point 400°C673.15 K
752 °F
1,211.67 °R
Crystal structure Orthorhombic, Aragonite
MSDS External MSDS Data
NFPA 704

NFPA 704 svg.png

Related compounds
Other anions Potassium nitrite
Other cations

Lithium nitrate
Sodium nitrate
Rubidium nitrate
Caesium nitrate

Potassium nitrate is a naturally occurring compound that has been used for ages, primarily used for gunpowder. In today's society, it is still used for gunpowder, but it has also spread to other uses, primarily fertilizers and fireworks.

The common name for potassium nitrate is saltpetre, which comes from the Latin words "sal petrae", which means "stone salt".



Potassium nitrate is a compound composed of potassium, nitrogen and oxygen in the ratio KNO3. At room temperature potassium nitrate either a colorless, transparent crystal or a white powder, depending on how it was formed. It is readily soluble in water, but it dissolves much faster in hot water, rather than cold water.

When it decomposes due to heating it slowly releases oxygen. Because of this it is a strong oxidizer.


Potassium Nitrate does occur naturally in the world, but in very small quantities. In today's society the most common way for it to be obtained is to create it from sodium nitrate. Sodium nitrate is quite common, very inexpensive, and comes in very large pockets found in the Chilean Deserts. Historically, it had to be produced locally since shipping it was impossible. This was done by mixing potassium nitrate, manure from livestock, and ashes along with other common earth substances such as grasses or straw to give it volume and make it porous. This was made into a long bed and placed in a box that was then covered to protect it from the rain. This was then slowly moistened with various liquids and turned to speed up the decomposition process. After about one year they distilled the mass in water and removed all of the solid mass. The liquid that remained then was added to wood ashes which then crystallized into potassium nitrate. From this point the potassium nitrate went through various steps to become different forms of gunpowder, which was its only real use in history.

Today potassium nitrate is made by purifying, treating and refining sodium nitrate, which as stated above is found in large deposits in South America.


Potassium nitrate is used extensively in use for plants, mainly for its nutrition purposes. It is, however, also used in tree stump remover. Besides from that though, the most common use of potassium nitrate is in fertilizers since it is a main component of the nutrition that plants require. The NPK rating of potassium nitrate is 13-0-44, which indicates that the percentage of potassium nitrate is 13%, 0%, and 44% of nitrogen, phosphorus, and potassium, which are the three elements that plants need.

Since potassium nitrate is combustible, it is also used in fireworks, fuel, and gunpowder. When used in gunpowder the potassium nitrate is mixed with charcoal and sulfur and is then turned into blackpowder. For use in fireworks, it is made for smoke bombs, because when potassium nitrate is combined with sucrose and burned, it produces smoke equal to 600 times its own mass. Also it is used to produce a orange and pink flame.

Also potassium nitrate is used in the production of food preservatives. It is used normally to package and preserve meats, although the use of it is slowly declining due to health issues. It is, however, still readily used in hot dogs.

Another interesting use for potassium nitrate is the use of it in toothpaste. For people with sensitive teeth, a special kind of toothpaste is created using potassium nitrate which can drastically improve the health of one's teeth.

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