Potash

Potash (or carbonate of potash) is an impure form of potassium carbonate (K₂CO₃).

Potash has been used since antiquity in the manufacture of glass and soap and as a fertilizer. The name comes from the English words pot and ash, referring to its discovery in the water-soluble fraction of wood ash.

The term has become somewhat ambiguous due to the substitution in fertilizers of cheaper potassium salts, such as potassium chloride (KCl) or potassium oxide (K₂O), to which the same common name is now sometimes also applied. In addition, potassium hydroxide (KOH) is commonly called caustic potash, an additional source of confusion.

The element potassium derives its English name from potash. A number of chemical compounds containing potassium use the word potash in their traditional names:

potash fertilizer	potassium oxide,	K2O
caustic potash or potash lye	potassium hydroxide,	KOH
carbonate of potash, salts of tartar, or pearlash	potassium carbonate,	K2CO3
chlorate of potash	potassium chlorate,	KClO3
muriate of potash	potassium chloride,	KCl
nitrate of potash or saltpeter	potassium nitrate,	KNO3
sulfate of potash	potassium sulfate,	K2SO4

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Potash production and trade

History

Up until the 20th century, potash was one of the most important industrial chemicals in Europe. It was refined from the ashes of broadleaved trees and produced primarily in the forested areas of Europe, Russia, and North America. The first U.S. patent was issued in 1790 to Samuel Hopkins for an improvement "in the making Pot ash and Pearl ash by a new Apparatus and Process."

Potash production provided late-18th and early-19th century settlers in North America a way to obtain badly needed cash and credit as they cleared their wooded land for crops. To make full use of their land, excess wood, including stumps, needed to be disposed. The easiest way to accomplish this was to burn any wood not needed for fuel or construction. Ashes from hardwood trees could then be used to make lye, 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 bushels per acre (500 to 900 m³/km²). In 1790, ashes could be sold for $3.25 to $6.25 per acre ($800 to $1500/km²) in rural New York State – nearly the same rate as hiring a laborer to clear the same area.

To create potash, take an open-bottomed barrel, and place it on a stone base with a groove cut into it, which will direct the resulting liquid into another container. Then place a layer of straw at the bottom, covered by a layer of sticks. This filter layer will prevent the ashes from contaminating the solution. Then fill the barrel with wood-ashes and pour water over it. The water will leach out the potash into the receptacle. This product will be of variable quality. Historically, it was measured by seeing how high an egg would float in the solution. The liquid may be boiled away to give a black, impure potash.

If desired, the potash could be further refined by baking in a kiln to produce a less impure form of potassium carbonate, known as pearlash for its pearly white color. This step was commonly performed at a nearby ashery. The refined potash was in increasing demand in Europe for use in the production of glass and ceramic goods. American hardwoods, besides being more abundant, are said to have provided a higher yield of quality potash than European wood. In some parts, potash receipts became a common form of currency. Some settlers found potash production to be quite lucrative, resulting in faster deforestation than farming alone would have caused.

Potash as baking aid

Potash along with hartshorn is also used as a baking aid similar to baking soda in old German Christmas bakery receipes such as Lebkuchen (ginger bread).

Modern era

  In 2005, Canada was the largest producer of potash with almost one-fourth of the world share followed by Russia and Belarus in Soligorsk, reports the British Geological Survey.

Natural potash deposits can also be mined. The world's largest potash producer is the Potash Corporation of Saskatchewan. Many other areas, however, have the resources for potash production. It should be noted that unlike other producers, Israel's Dead Sea Works and Jordan's Arab Potash Company use solar evaporation pans in the Dead Sea to produce carnallite from which potassium chloride is produced.

• Popular Opposition to proposed potash mining in Udon Thani province, Thailand*
• "Digging for Potash, Mining Companies Encounter An Iron Will" magazine article
• Russia reaps rich harvest with potash