Potash
Potash is a term used for potassium-bearing chemical compounds, primarily known for its critical role as a key nutrient in fertilizers for plants. It is derived mainly from potassium oxide (K₂O) and is essential for the growth of all plants and animals, with no viable substitutes. Economically exploitable potash deposits are primarily found in regions such as Canada, the United States, Germany, Russia, and the Middle East, particularly from the brines of the Dead Sea. Canada is the largest producer and holds the most significant reserves, especially in Saskatchewan. In the U.S., major production areas include New Mexico and Utah, with historical roots dating back to colonial times when potash was initially used in soap and glass production. Today, around 95% of potash is utilized for fertilizers, with the remainder used in various industries, including chemicals, soap manufacturing, and ceramics. The extraction of potash can occur through various methods, including solution mining from subterranean brines and evaporation processes from saline lakes.
Potash
Where Found
Economically exploitable accumulations of potassium-bearing minerals occur in bedded deposits in the southwestern United States as well as in Germany, Canada, France, and Russia. Some potash is also produced from the brines of the Dead Sea by Israel and Jordan.
Primary Uses
Potassium is one of the essential plant nutrients, and its principal use is in inorganic fertilizers. Potash is also used in glass and soap.
Technical Definition
“Potash” is a commercial name applied to potassium-bearing chemical compounds. More specifically, it refers to the potassium (K2O) equivalent in such materials. Potassium is one of the three primary plant nutrients (along with nitrogen and phosphorus), and there is no substitute for it as an essential in all animals and plants. The element potassium is found in a wide variety of minerals in the Earth’s crust, but these minerals are difficult to process for their potassium. Of greater economic importance is the potassium that occurs as chlorides and sulfates, including the minerals sylvite, KCl (muriate of potash); carnallite, KCl·6H2O; kainite, 4KCl·4MgSO4·11H2O; langbeinite, K2SO4·2MgSO4; and polyhalite, K2MgCa2(SO4)4·2H2O.
Description, Distribution, and Forms
Potash is the commercial name applied to a number of potassium-bearing materials. The element potassium (K) is a soft, silver-white metal. Because of its high reactivity, potassium does not exist uncombined in nature but oxidizes when exposed to air. It also occurs in a number of minerals.
Potash is widely distributed in nature, but the number of commercially exploitable deposits is relatively small. In the United States, the area around Carlsbad, New Mexico, remains the largest commercial producer. Other important deposits are in southeastern Utah, southern Michigan, the Williston basin of Montana and North Dakota, Searles Lake, and the Great Salt Lake. Canada, the world’s largest producer of potash, possesses the world’s largest reserves, with thick deposits centered on the province of Saskatchewan. Other important potash producers are Russia, Belarus, and Germany (notably around the city of Stassfurt). Israel and Jordan in the Middle East have developed potash industries based on the solar evaporation of Dead Sea brines.
The United States imports a high percentage of its potash requirements, with Canada the largest supplier. The United States has historically exported potash to countries in Latin America, where, because of shorter transport distances, it has had an economic advantage over that of the other major producers.
History
Potash, obtained by wood ashes in hot water, was first used in the United States in soap and glass during colonial times. By the early 1800s, Germans had developed the practice of using potash as a plant supplement, and through the nineteenth century, the United States became a progressively larger importer of potash from Germany. Disagreements with Germany concerning trade contracts (and their eventual cancellation) spurred potash exploration in the United States in the early 1900s.
In 1916, significant production of potash in the United States began from the brines of Searles Lake in California. Searles Lake remained the principal domestic source of potash until the development of extensive deposits around Carlsbad, New Mexico, in the early 1930s. After that time, the Carlsbad mines dominated the domestic potash industry, at times accounting for 90 percent of production. In the late 1950s, production began in southeastern Utah, initially from underground mines and later by solution mining. In the latter technique, old mines are flooded with water, which, over time, dissolves the potash. The water is then pumped to the surface, where the dissolved salts are precipitated by solar evaporation. Potash is also produced from the brines of the Great Salt Lake in Utah.
Obtaining Potash
Potash occurs in, and is derived from, several sources: brines, saline lakes, lake deposits in arid regions, and, most important, layered marine (salt) deposits. Whereas modern analogs for the formation of marine evaporites are difficult to find, such deposits abound in the geologic record.
The precipitation of evaporite deposits must occur from an evaporating shallow sea in a region of high temperatures and low precipitation. Even complete evaporation of such a sea, however, would not be enough to account for the thickness of evaporites, which may be thousands of meters. The physical setting must include a barrier (reef or bar) that partially isolates the shallow sea from the main body of the ocean. The barrier prevents the movement of significant amounts of water from the site of evaporation but allows an inflow that will constantly replenish the supply of dissolved salts. During evaporite precipitation, there is a particular order of appearance of salts, beginning with carbonates, (mostly dolomite). The carbonates are followed by gypsum, halite, and finally the highly soluble “bitter” salts of potassium and magnesium.
There are few marine localities with the conditions necessary for evaporite formation; they include the Red Sea and the Persian Gulf. On the continents, Searles Lake, the Great Salt Lake, the Dead Sea, and the Caspian Sea in southern Russia contain brines rich in potassium. In fact, salt concentrations are high enough in the Gulf of Kara-Bogaz, in the eastern part of the Caspian Sea, that sodium and magnesium salts are precipitated there.
Uses of Potash
Approximately 95 percent of the potash produced (mostly sylvite) goes into fertilizers. Langbeinite, because of its beneficial magnesium content, is used for the fertilization of citrus crops. The remaining 5 percent of potash production goes to the chemical industry. Because potash is a strong base, it is used in soaps, detergents, dyes, and disinfectants. Other uses include medicines, explosives, photography, ceramics, glass, and blue pigments in printing.
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