Potash ˈpɒtæʃ is the
common nameA common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
for various mined and manufactured salts that contain
potassiumPotassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...
in water-soluble form. In some rare cases, potash can be formed with traces of organic materials such as plant remains, and this was the major historical source for it before the industrial era. The name derives from "pot ash," which refers to plant ashes soaked in water in a pot.
Today, potash is produced worldwide at amounts exceeding 30 million
tonneThe tonne, known as the metric ton in the US , often put pleonastically as "metric tonne" to avoid confusion with ton, is a metric system unit of mass equal to 1000 kilograms. The tonne is not an International System of Units unit, but is accepted for use with the SI...
s per year, mostly for use in
fertilizerFertilizer is any organic or inorganic material of natural or synthetic origin that is added to a soil to supply one or more plant nutrients essential to the growth of plants. A recent assessment found that about 40 to 60% of crop yields are attributable to commercial fertilizer use...
s. Various types of fertilizer-potash thus comprise the single largest global industrial use of the element potassium. Potassium derives its name from potash, from which it was first derived by
electrolysisIn chemistry and manufacturing, electrolysis is a method of using a direct electric current to drive an otherwise non-spontaneous chemical reaction...
of caustic potash, in 1808.
Terminology
Potash refers to potassium compounds and potassium-bearing materials, the most common being
potassium chlorideThe chemical compound potassium chloride is a metal halide salt composed of potassium and chlorine. In its pure state, it is odorless and has a white or colorless vitreous crystal appearance, with a crystal structure that cleaves easily in three directions. Potassium chloride crystals are...
(KCl). The term "potash" comes from the
Old DutchIn linguistics, Old Dutch denotes the forms of West Franconian spoken and written in the Netherlands and present-day northern Belgium during the Early Middle Ages. It is regarded as the primary stage in the development of a separate Dutch language...
word
potaschen. The old method of making
potassium carbonatePotassium carbonate is a white salt, soluble in water , which forms a strongly alkaline solution. It can be made as the product of potassium hydroxide's absorbent reaction with carbon dioxide. It is deliquescent, often appearing a damp or wet solid...
was by leaching of
wood ashWood ash is the residue powder left after the combustion of wood. Main producers of wood ash are wood industries and power plants.-Composition:...
es and then evaporating the resulting solution in large iron pots, leaving a white residue called "pot ash". Approximately 10% by weight of common wood ash can be recovered as pot ash. Later, "potash" became the term widely applied to naturally occurring potassium salts and the commercial product derived from them.
The following table lists a number of potassium compounds which use the word
potash in their traditional names:
| Common name | Chemical name | Formula |
| Potash fertilizer |
c.1942 potassium carbonate Potassium carbonate is a white salt, soluble in water , which forms a strongly alkaline solution. It can be made as the product of potassium hydroxide's absorbent reaction with carbon dioxide. It is deliquescent, often appearing a damp or wet solid...
; c.1950 any one or more of potassium chlorideThe chemical compound potassium chloride is a metal halide salt composed of potassium and chlorine. In its pure state, it is odorless and has a white or colorless vitreous crystal appearance, with a crystal structure that cleaves easily in three directions. Potassium chloride crystals are...
, potassium sulfatePotassium sulfate is a non-flammable white crystalline salt which is soluble in water...
(K2SO4), potassium magnesium sulfate (KPotassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...
2SSulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
OOxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
4·2MgMagnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
SSulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
OOxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
4), langbeinite (K2Mg2(SO4)3)Langbeinite is a potassium magnesium sulfate mineral with formula: K2Mg23. Langbeinite crystallizes in the isometric - tetartoidal system as transparent colorless or white with pale tints of yellow to green and violet crystalline masses. It has a vitreous luster. The Mohs hardness is 3.5 to 4 and...
or potassium nitratePotassium nitrate is a chemical compound with the formula KNO3. It is an ionic salt of potassium ions K+ and nitrate ions NO3−.It occurs as a mineral niter and is a natural solid source of nitrogen. Its common names include saltpetre , from medieval Latin sal petræ: "stone salt" or possibly "Salt...
. Does not contain potassium oxidePotassium oxide is an ionic compound of potassium and oxygen. This pale yellow solid, the simplest oxide of potassium, is a rarely encountered, highly reactive compound...
, which plants do not take up. |
| Caustic potash or potash lye |
potassium hydroxide Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...
|
KOH |
| Carbonate of potash, salts of tartar, or pearlash |
potassium carbonate Potassium carbonate is a white salt, soluble in water , which forms a strongly alkaline solution. It can be made as the product of potassium hydroxide's absorbent reaction with carbon dioxide. It is deliquescent, often appearing a damp or wet solid...
|
K2CO3 |
| Chlorate of potash |
potassium chloratePotassium chlorate is a compound containing potassium, chlorine and oxygen atoms, with the molecular formula KClO3. In its pure form, it is a white crystalline substance. It is the most common chlorate in industrial use...
|
KClO3 |
| Muriate of potash |
potassium chloride The chemical compound potassium chloride is a metal halide salt composed of potassium and chlorine. In its pure state, it is odorless and has a white or colorless vitreous crystal appearance, with a crystal structure that cleaves easily in three directions. Potassium chloride crystals are...
|
KCl:NaCl (95:5 or higher) |
| Nitrate of potash or saltpeter |
potassium nitrate Potassium nitrate is a chemical compound with the formula KNO3. It is an ionic salt of potassium ions K+ and nitrate ions NO3−.It occurs as a mineral niter and is a natural solid source of nitrogen. Its common names include saltpetre , from medieval Latin sal petræ: "stone salt" or possibly "Salt...
|
KNO3 |
| Sulfate of potash |
potassium sulfate Potassium sulfate is a non-flammable white crystalline salt which is soluble in water...
|
K2SO4 |
| Permanganate of potash |
potassium permanganatePotassium permanganate is an inorganic chemical compound with the formula KMnO4. It is a salt consisting of K+ and MnO4− ions. Formerly known as permanganate of potash or Condy's crystals, it is a strong oxidizing agent. It dissolves in water to give intensely purple solutions, the...
|
KMnO4 |
History of production
Potash (especially potassium carbonate) has been used from the dawn of history in bleaching textiles, making
glassGlass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
, and, from about A.D. 500, in making
soapIn chemistry, soap is a salt of a fatty acid.IUPAC. "" Compendium of Chemical Terminology, 2nd ed. . Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford . XML on-line corrected version: created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN...
. Potash was principally obtained by leaching the ashes of land and sea plants. Beginning in the 14th century potash was mined in
EthiopiaEthiopia , officially known as the Federal Democratic Republic of Ethiopia, is a country located in the Horn of Africa. It is the second-most populous nation in Africa, with over 82 million inhabitants, and the tenth-largest by area, occupying 1,100,000 km2...
. One of the world's largest deposits, 140 to 150 million tons, is located in the
TigrayTigray Region is the northernmost of the nine ethnic regions of Ethiopia containing the homeland of the Tigray people. It was formerly known as Region 1...
's Dallol area. Potash was one of the most important industrial chemicals in
CanadaCanada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
. It was refined from the ashes of broadleaved trees and produced primarily in the forested areas of Europe,
RussiaRussia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
, and
North AmericaNorth America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
. The first
U.S. patentUnited States patent law was established "to promote the Progress of Science and useful Arts, by securing for limited Times to Authors and Inventors the exclusive Right to their respective Writings and Discoveries;" as provided by the United States Constitution. Congress implemented these...
was issued in 1790 to
Samuel HopkinsSamuel Hopkins was an American inventor from Philadelphia, Pennsylvania, and Pittsford, Vermont. On July 31, 1790, he was granted the first U.S. patent, under the new U.S. patent statute just signed into law by President Washington on April 10, 1790...
for an improvement "in the making Pot ash and Pearl ash by a new Apparatus and Process."
As early as 1767, potash from wood ashes was exported from Canada, and exports of potash and pearl ash (potash and lime) reached 43,958 barrels in 1865. There were 519 asheries in operation in 1871. The industry declined in the late 19th century when large-scale production of potash from mineral salts was established in Germany. In 1943, potash was discovered in
SaskatchewanSaskatchewan is a prairie province in Canada, which has an area of . Saskatchewan is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, and on the south by the U.S. states of Montana and North Dakota....
, Canada, in the process of drilling for oil. Active exploration began in 1951. In 1958, the Potash Company of America became the first potash producer in Canada with the commissioning of an underground potash mine at
Patience LakePatience Lake is a lake in central Saskatchewan, Canada east of Saskatoon. The lake is located in the rural municipality of Blucher No. 343. The lake serves as a groundwater discharge region for higher elevations to the east and west....
; however, due to water seepage in its shaft, production stopped late in 1959 and, following extensive grouting and repairs, resumed in 1965. The underground mine was flooded in 1987 and was reactivated for commercial production as a solution mine in 1989.
In the late 18th and early 19th centuries, potash production provided settlers in North America a way to obtain badly-needed cash and credit as they cleared wooded land for crops. To make full use of their land, settlers needed to dispose of excess wood. The easiest way to accomplish this was to burn any wood not needed for fuel or construction. Ashes from
hardwoodHardwood is wood from angiosperm trees . It may also be used for those trees themselves: these are usually broad-leaved; in temperate and boreal latitudes they are mostly deciduous, but in tropics and subtropics mostly evergreen.Hardwood contrasts with softwood...
trees could then be used to make
lyePotassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...
, which could either be used to make soap or boiled down to produce valuable potash. Hardwood could generate ashes at the rate of 60 to 100
bushelA bushel is an imperial and U.S. customary unit of dry volume, equivalent in each of these systems to 4 pecks or 8 gallons. It is used for volumes of dry commodities , most often in agriculture...
s per acre (500 to 900 m
3/km
2). In 1790, ashes could be sold for $3.25 to $6.25 per acre ($800 to $1500/km
2) in rural
New York StateNew York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...
– nearly the same rate as hiring a laborer to clear the same area. Potash making became a major industry in British North America. Great Britain was always the most important market. The American potash industry followed the woodsman's ax across the country. After about 1820, New York replaced New England as the most important source; by 1840 the center was in Ohio. Potash production was always a by-product industry, following from the need to clear land for agriculture.
Most of the world reserves of potassium (K) were deposited as sea water in ancient inland oceans evaporated, and the potassium salts crystallized into beds of potash ore. These are the locations where potash is currently being mined today. The deposits are a naturally-occurring mixture of potassium chloride (KCl) and sodium chloride (NaCl), better known as common table salt. Over time, as the surface of the earth changed, these deposits were covered by thousands of feet of earth.
Most potash mines today are deep shaft mines as much as 4,400 feet (1,400 m) underground. Others are mined as strip mines, having been laid down in horizontal layers as sedimentary rock. In above-ground processing plants, the KCl is separated from the mixture to produce a high analysis natural potassium fertilizer. Other naturally occurring potassium salts can be separated by various procedures, resulting in potassium sulfate and potassium-magnesium sulfate.
Today some of the world's largest known potash deposits are spread all over the world from
SaskatchewanSaskatchewan is a prairie province in Canada, which has an area of . Saskatchewan is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, and on the south by the U.S. states of Montana and North Dakota....
, Canada, to Brazil,
BelarusBelarus , officially the Republic of Belarus, is a landlocked country in Eastern Europe, bordered clockwise by Russia to the northeast, Ukraine to the south, Poland to the west, and Lithuania and Latvia to the northwest. Its capital is Minsk; other major cities include Brest, Grodno , Gomel ,...
, Germany, and more notably the Permian Basin. The Permian basin deposit includes the major mines outside of
CarlsbadCarlsbad is a city in and the county seat of Eddy County, New Mexico, in the United States. As of the 2010 census, the city population was 26,138. Carlsbad is the center of the designated micropolitan area of Carlsbad-Artesia, which has a total population of 55,435...
, New Mexico, to the world's purest potash deposit in Lea County New Mexico (not far from the Carlsbad deposits), which is believed to be roughly 80% pure. Canada is the largest producer, followed by Russia and Belorussia. The most significant reserve of Canada's potash is located in the province of Saskatchewan and controlled by the
Potash Corporation of SaskatchewanThe Potash Corporation of Saskatchewan Inc. , also referred to as PotashCorp, is a Canadian corporation based in Saskatoon, Saskatchewan. The company is the world's largest potash producer and the third largest producers of nitrogen and phosphate, three primary crop nutrients used to produce...
.
In the beginning of the 20th century, potash deposits were found in the
Dallol DepressionDallol was a settlement in northern Ethiopia. Located in Administrative Zone 2 of the Afar Region in the Afar Depression, it has a latitude and longitude of with an elevation of about 130 meters below sea level...
in Musely and Crescent localities near the Ethiopean-Eritrean border. The estimated reserves are 173 and 12 million tonnes for the Musely and Crescent, respectively. The latter is particularly suitable for surface mining; it was explored in the 1960s but the works stopped due to the flood in 1967. Attempts to continue mining in the 1990s were halted by the Eritrean–Ethiopian War and have not resumed by 2009.
Consumption
Production and resources of potash
(2010, in million tonnes)
Country |
Production |
Reserves |
|
9.5 |
4400 |
|
6.8 |
3300 |
|
5.0 |
750 |
|
3.0 |
210 |
|
3.0 |
150 |
|
2.1 |
40 |
|
1.2 |
40 |
|
0.9 |
130 |
|
0.7 |
70 |
|
0.4 |
300 |
|
0.4 |
22 |
|
0.4 |
20 |
| Other countries |
|
50 |
| World total |
33 |
9500 |
Fertilizers
Potassium is the seventh most abundant element in the Earth's crust, and is the third major plant and crop nutrient after
nitrogenNitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
and
phosphorusPhosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...
. It has been used since
antiquityAncient history is the study of the written past from the beginning of recorded human history to the Early Middle Ages. The span of recorded history is roughly 5,000 years, with Cuneiform script, the oldest discovered form of coherent writing, from the protoliterate period around the 30th century BC...
as a
soilSoil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...
fertilizerFertilizer is any organic or inorganic material of natural or synthetic origin that is added to a soil to supply one or more plant nutrients essential to the growth of plants. A recent assessment found that about 40 to 60% of crop yields are attributable to commercial fertilizer use...
(about 90% of current use). Potash is important for agriculture because it improves water retention, yield, nutrient value, taste, colour, texture and disease resistance of food crops. It has wide application to fruit and vegetables, rice, wheat and other grains, sugar, corn, soybeans, palm oil and cotton, all of which benefit from the nutrient’s quality enhancing properties.
Demand for food and animal feed has been on the rise since 2000. The U.S. Department of Agriculture’s Economic Research Service (ERS) attributes the trend to average annual population increases of 75 million people around the world. Geographically, economic growth in Asia and Latin America greatly contributed to the increased use of potash-based fertilizer. Rising incomes in developing countries also was a factor in the growing potash and fertilizer use. With more money in the household budget, consumers added more meat and dairy products to their diets. This shift in eating patterns required more acres to be planted, more fertilizer to be applied and more animals to be fed – all requiring more potash.
After years of trending upward, fertilizer use slowed in 2008. The worldwide economic downturn is the primary reason for the declining fertilizer use, dropping prices and mounting inventories.
The world's largest consumers of potash are China, the United States, Brazil and India. Brazil imports 90% of the potash it needs.
Potash imports and exports are often reported in "K
2O equivalent", although fertilizer never contains potassium oxide, per se, because potassium oxide is caustic and hygroscopic.
Potash prices have soared in recent years. What was once a commodity worth about $200 a tonne is expected to reach $1,500 by 2020; Vancouver prices are US$872.50 per tonne in 2009, which is a record high. As of November 2011 potash prices have dropped to about $470 per metric tonne.
Other uses
In addition to its use as a fertilizer, potassium chloride is important in industrialized economies, where it is used in aluminium recycling, by the chloralkali industry to produce potassium hydroxide, in metal
electroplatingElectroplating is a plating process in which metal ions in a solution are moved by an electric field to coat an electrode. The process uses electrical current to reduce cations of a desired material from a solution and coat a conductive object with a thin layer of the material, such as a metal...
, oil-well
drilling fluidIn geotechnical engineering, drilling fluid is a fluid used to aid the drilling of boreholes into the earth. Often used while drilling oil and natural gas wells and on exploration drilling rigs, drilling fluids are also used for much simpler boreholes, such as water wells. Liquid drilling fluid...
, snow and ice melting, steel heat-treating, and water softening. Potassium hydroxide is used for industrial water treatment and is the precursor of potassium carbonate, several forms of potassium phosphate, many other potassic chemicals, and soap manufacturing. Potassium carbonate is used to produce animal feed supplements, cement, fire extinguishers, food products, photographic chemicals, and textiles. It is also used in brewing beer, pharmaceutical preparations, and as a catalyst for synthetic rubber manufacturing. These nonfertilizer uses have accounted for about 15% of annual potash consumption in the United States.
Potash (potassium carbonate) along with
hartshornAmmonium bicarbonate, a compound with formulaNH4, also called bicarbonate of ammonia, ammonium hydrogen carbonate, hartshorn, AmBic or powdered baking ammonia, is the bicarbonate salt of ammonia....
was also used as a baking aid similar to
baking sodaSodium bicarbonate or sodium hydrogen carbonate is the chemical compound with the formula Na HCO3. Sodium bicarbonate is a white solid that is crystalline but often appears as a fine powder. It has a slightly salty, alkaline taste resembling that of washing soda . The natural mineral form is...
in old German baked goods such as
lebkuchenLebkuchen is a traditional German baked Christmas treat, somewhat resembling gingerbread.Lebkuchen were invented by Medieval monks in Franconia, Germany in the 13th century. Lebkuchen bakers were recorded as early as 1296 in Ulm, and 1395 in Nürnberg...
(ginger bread).
Further reading
External links