Potassium Nitrate

OVERVIEW

Potassium nitrate (poe-TAS-ee-yum NYE-trate) is transparent, colorless, or white, and may be crystalline or powdery solid. It is odorless with a sharp, cool, salty taste. It is slightly hygroscopic, that is, having a tendency to absorb moisture from the air. Potassium nitrate, more commonly known as saltpeter or niter, has been used by humans for many centuries. Going back as far as ancient Chinese civilizations, the compound was used as an ingredient in fireworks, to preserve foods, to make incense burn more evenly, to increase the male sex drive, and for magic potions.

HOW IT IS MADE

Potassium nitrate is made commercially by reacting potassium chloride (KCl) with nitric acid (HNO₃) at high temperatures: 3KCl + 4HNO₃ → 3KNO₃ + Cl₂ + NOCl + 2H₂O.

KEY FACTS

OTHER NAMES:

Niter; saltpeter; nitrate of potash

FORMULA:

KNO₃

ELEMENTS:

Potassium, nitrogen, oxygen

COMPOUND TYPE:

Salt (inorganic)

STATE:

Solid

MOLECULAR WEIGHT:

101.10 g/mol

MELTING POINT:

337°C (639°F)

BOILING POINT:

Not applicable; decomposes above 400°C (750°F)

SOLUBILITY:

Soluble in water and glycerol; slightly soluble in ethyl alcohol

The compound can also be obtained for use from natural sources. It occurs as a thin, whitish, glassy crust on rocks in sheltered areas, such as caves. In warm climates, potassium nitrate forms when bacteria decompose animal feces and other organic matter. The compound usually appears as a white powder on the surface of soil. These sources of potassium nitrate are of use on a small scale basis and have no commercial value.

COMMON USES AND POTENTIAL HAZARDS

The primary use of potassium nitrate is in explosives, blasting powders, gunpowder, fireworks, and matches. The compound is used as an oxidizing agent in such preparations. An oxidizing agent is a substance that provides oxygen for the combustion of some other material. For example, gunpowder, the oldest known explosive, is a mixture of potassium nitrate, charcoal (nearly pure carbon), and sulfur. When the mixture is ignited, the carbon and sulfur burn very rapidly to produce carbon dioxide (CO) and sulfur dioxide (SO₂. At the same time, the potassium nitrate decomposes to produce a variety of products, one of which is nitric oxide (NO). The rapid formation of very hot gases is responsible for the shock wave produced in the explosion.

Some other uses of potassium nitrate include:

• As a meat preservative that helps meats retain their bright red color;
• As a flux for soldering;
• In fertilizers, especially for use with crops such as tomatoes, potatoes, tobacco, leafy vegetables, citrus fruits, and peaches;
• In the manufacture of glasses and ceramics;
• As an additive for tobacco products that helps the tobacco burn more cleanly and smoothly;
• As an oxidizing agent in rocket propulsion systems;
• As a diuretic, a substance that increases the flow of urine from the body; and
• As a raw material in the manufacture of other potassium compounds.

Interesting Facts

• At one time, potassium nitrate was prepared by mixing manure with mortar or wood ash, soil, and an organic material, such as straw. The bed was kept moist with urine and turned often to speed decomposition of the organic matter. After a year, the bed was thoroughly watered, dissolving the potassium nitrate that had accumulated. It was then recrystallized and purified.
• In 1862, leaders of the Confederate Army ordered a chemistry professor at South Carolina College to teach farmers how to make potassium nitrate to ensure an adequate supply of the compound for use in making gunpowder.
• Gunpowder was probably first used as early as the eleventh century. The English natural philosopher Roger Bacon (1214–1294) described a method for making gunpowder in 1242.

Exposure to moderate amounts of potassium nitrate dust and fumes can result in irritation of the skin, eyes, and respiratory system. Symptoms may include sneezing, coughing, dizziness, drowsiness, and headache. Ingestion of the compound may result in nausea, vomiting, and severe abdominal pain. Exposure to large quantities of the compound may have more serious consequences because it interferes with the blood's ability to transport oxygen. In such cases, a person may experience shortness of breath, bluish skin, serious damage to the kidneys, unconsciousness, and even death. People who work directly with potassium nitrate are at greatest risk for such health problems.

Words to Know

FLUX

A material that lowers the melting point of another substance or mixture of substances or that is used in cleaning a metal.

FOR FURTHER INFORMATION

"Material Safety Data Sheet: Potassium Nitrate." Department of Chemistry, Iowa State University. http://avogadro.chem.iastate.edu/MSDS/KNO3.htm (accessed on November 3, 2005).

Multhauf, Robert P., and Christine M. Roane. "Nitrates." In Dictionary of American History. Edited by Stanley I. Kutler. 3rd ed., vol. 6. New York: Charles Scribner's Sons, 2003.

"Potassium Nitrate." Hazardous Substances Data Bank. http://toxnet.nlm.nih.gov/cgi-bin/sis/search/r?dbs+hsdb:@term+@na+Potassium+Nitrate (accessed on November 3, 2005).

"Potassium Nitrate." International Chemical Safety Cards. http://www.inchem.org/documents/icsc/icsc/eics0184.htm (accessed on November 3, 2005).

"Potassium Nitrate." Skylighter. http://www.skylighter.com/potassium-nitrate.html (accessed on November 3, 2005).

Potassium Nitrate

Potassium nitrate, also known as saltpeter or niter, is a chemical compound consisting of potassium, nitrogen, and oxygen. While it has many applications, including use as a fertilizer, its most important usage historically has been as a component of gunpowder. Over time its use as an explosive has been made nearly obsolete by dynamite and TNT, but it is still used today in artillery-shell primers, hand-grenade fuses, and fireworks.

Potassium nitrate consists of three basic chemical elements: potassium a soft, light, silver white metal; nitrogen a colorless, odorless gas; and oxygen, another common gas. When these three elements are reacted in the proper proportions they form a whitish compound known as nitre, or saltpeter, which has the chemical formula KNO₃. This naturally occurring compound, which forms thin whitish glassy crusts on rocks, can be found in sheltered areas such as caves and particularly on soils rich in organic matter. Until the first World War the United States imported most of its potassium nitrate from Europe where it was mined from ancient sea beds. When these sources became unavailable during the war, the brines lakes in California became the principal supplier of nitre.

Since it is rich in potassium, an element which is vital for plant growth, large quantities of potassium nitrate are used annually as fertilizer. It also has utility as a food preservative, and although never proven, it is claimed that when ingested saltpeter has an aphrodisiac, or sexual-desire-reducing effect. However, the most renowned use for this whitish powder was discovered over 2,200 years ago by the Chinese. When 75% potassium nitrate is mixed appropriately with 15% carbon (charcoal), and 10% sulfur, the resultant black powder has explosive properties. This mixture (which throughout history has enjoyed such colorful nicknames as “Chinese Snow” and “the Devil’s Distillate”) eventually became known as gunpowder. As early as AD 1000, it was used by its inventors in explosive grenades and bombs. By the thirteenth century, the use of gunpowder had spread throughout the western world: in 1242 the English philosopher Roger Bacon described his own preparation of this material. By the early fourteenth century, black powder and guns were being manufactured in Europe. Although the early firearms were awkward and inefficient, they were rapidly improved. Their use led to significant social changes, including the end of the European feudal system. In fact, it is arguable that exploitation of the properties of gunpowder has been responsible for many of the major social and cultural changes in history.

Originally, potassium nitrate and the other components of gunpowder were carefully hand mixed and broken into small particles using wooden stamps. Later, water power mechanized the stamping stage, and metal stamps replaced the wooden ones. In modern production, charcoal and sulfur are mixed by the tumbling action of steel balls in a rotating hollow cylinder. The potassium nitrate is pulverized separately, and the ingredients are then mixed and ground. After further crushing the gunpowder is pressed into cakes; these are then rebroken and separated into grains of specific size. Finally, the grains are tumbled in wooden cylinders to wear off rough edges. During this process graphite is introduced, a coating powder which provides a friction-reducing, moisture-resistant film.

By 1900 black powder had been virtually replaced as the standard firearms propellant. Although it had served for centuries, it had many drawbacks. It produced a large cloud of white smoke when ignited, built up a bore-obstructing residue after relatively few shots, and absorbed moisture easily. Its replacement, nitrocellulose based smokeless powders (known as guncotton), eliminated most of these disadvantages. Gunpowder had already been largely replaced as a primary blasting explosive by dynamite and TNT but it is still widely used today in artillery-shell primers, hand-grenade fuses, and fireworks.

Potassium nitrate

Potassium nitrate, also known as saltpeter or niter, is a chemical compound consisting of potassium, nitrogen , and oxygen . While it has many applications, including use as a fertilizer, its most important usage historically has been as a component of gunpowder. Over time its use as an explosive has been made nearly obsolete by dynamite and TNT, but it is still used today in artilleryshell primers, hand-grenade fuses, and fireworks.

Potassium nitrate consists of three basic chemical elements: potassium a soft, light, silver white metal ; nitrogen a colorless, odorless gas; and oxygen, another common gas. When these three elements are reacted in the proper proportions they form a whitish compound known as nitre, or saltpeter, which has the chemical formula KNO3. This naturally occurring compound, which forms thin whitish glassy crusts on rocks , can be found in sheltered areas such as caves and particularly on soils rich in organic matter. Until the first World War the United States imported most of its potassium nitrate from Europe where it was mined from ancient sea beds. When these sources became unavailable during the war, the brines lakes in California became the principal supplier of nitre.

Since it is rich in potassium, an element which is vital for plant growth, large quantities of potassium nitrate are used annually as fertilizer. It also has utility as a food preservative, and although never proven, it is claimed that when ingested saltpeter has an aphrodisiac, or sexual-desire-reducing effect. However, the most renowned use for this whitish powder was discovered over 2,200 years ago by the Chinese. When 75% potassium nitrate is mixed appropriately with 15% carbon (charcoal) and 10% sulfur , the resultant black powder has explosive properties. This mixture (which throughout history has enjoyed such colorful nicknames as "Chinese Snow" and "the Devil's Distillate") eventually became known as gunpowder. As early as a.d. 1000, it was used by its inventors in explosive grenades and bombs. By the thirteenth century, the use of gunpowder had spread throughout the western world: in 1242 the English philosopher Roger Bacon described his own preparation of this material. By the early fourteenth century, black powder and guns were being manufactured in Europe. Although the early firearms were awkward and inefficient, they were rapidly improved. Their use led to significant social changes, including the end of the European feudal system. In fact, it is arguable that exploitation of the properties of gunpowder has been responsible for many of the major social and cultural changes in history.

Originally, potassium nitrate and the other components of gunpowder were carefully hand mixed and broken into small particles using wooden stamps. Later, water power mechanized the stamping stage, and metal stamps replaced the wooden ones. In modern production, charcoal and sulfur are mixed by the tumbling action of steel balls in a rotating hollow cylinder. The potassium nitrate is pulverized separately, and the ingredients are then mixed and ground. After further crushing the gunpowder is pressed into cakes; these are then rebroken and separated into grains of specific size. Finally, the grains are tumbled in wooden cylinders to wear off rough edges. During this process graphite is introduced, a coating powder which provides a friction-reducing, moisture-resistant film.

By 1900 black powder had been virtually replaced as the standard firearms propellant. Although it had served for centuries, it had many drawbacks. It produced a large cloud of white smoke when ignited, built up a bore-obstructing residue after relatively few shots, and absorbed moisture easily. Its replacement, nitrocellulose based smokeless powders (known as guncotton), eliminated most of these disadvantages. Gunpowder had already been largely replaced as a primary blasting explosive by dynamite and TNT but it is still widely used today in artillery-shell primers, hand-grenade fuses, and fireworks.

saltpetre potassium nitrate, nitre. XVI. alt., by assim. to SALT, of †salpetre (XIV) — (O)F. salpètre — medL. salpetra, prob. for *sāl petræ ‘salt of rock’ (the substance being so named because it occurs as an incrustation on stones).

potassium nitrate See nitrates; saltpetre.