Potash (or carbonate of potash) is an impure form of potassium carbonate (K2CO3) mixed with other potassium salts. 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.
It is today principally produced by mining suitable deposits which are found throughout the world.
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 | 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
Potash Production and Trade
Until the 20th century, potash was one of the most important industrial chemicals in Europe. It was produced primarily in the forested areas of Europe, in Russia and in North America, refined from the ashes of broadleaved trees.
Potash production provided late 18th and early 19th century settlers in North America a way to obtain badly needed cash and credit while they were in the process of clearing their wooded land for crops. To make full use of their land, excess wood, including stumps needed to be disposed of. 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 generatate ashes at the rate of 60 to 100 bushels per acre (500 to 900 mÂ³/kmÂ²). In 1790 an ashes could be sold for $3.25 to $6.25 per acre ($800 to $1500/kmÂ²) in rural New York State, nearly the going rate for hiring a laborer to clear that same area.
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 postash 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.
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.”
Today, only 12 countries produce the world’s supply of potash. The main producers are North America, the Middle East, Russia and Belarus. Many other areas, however, have the resources for potash production.