Terminology
Potash refers to potassium compounds and potassium-bearing materials, the most common being potassium chloride (KCl). The term "potash" comes from the Old Dutch word potaschen. The old method of making potassium carbonate (K2CO3) was by leaching of wood ashes 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; c.1950 any one or more of potassium chloride, potassium sulfate (K2SO4), potassium magnesium sulfate (K2SO4ยท2MgSO4), langbeinite (K2Mg2(SO4)3) or potassium nitrate. Does not contain potassium oxide, which plants do not take up. | |
| 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:NaCl (95:5 or higher) |
| Nitrate of potash or saltpeter | potassium nitrate | KNO3 |
| Sulfate of potash | potassium sulfate | K2SO4 |
| Permanganate of potash | potassium permanganate | KMnO4 |
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