Wikipedia: Historically KOH was made by boiling a solution of potassium carbonate (potash) with calcium hydroxide (slaked lime), leading to a metathesis reaction which caused calcium carbonate to precipitate, leaving potassium hydroxide in solution: Ca(OH)2 + K2CO3 → CaCO3 + 2 KOH
Filtering off the precipitated calcium carbonate and boiling down the solution gives potassium hydroxide (calcinated or caustic potash). This method used potash extracted from wood ashes using slaked lime. It was the most important method of producing potassium hydroxide until the late 19th century.
How to make potassium carbonate: http://fryingcolors.com/k2co3.html
How to make potassium nitrate: http://docsouth.unc.edu/imls/lecontesalt/leconte.html
Lime and Lye (caveman chemistry): http://www.cavemanchemistry.com/oldcave/projects/lime/
Chemistry of Potash: http://www.cavemanchemistry.com/oldcave/projects/potash/
Manganese dioxide from batteries: http://www.youtube.com/watch?v=knc1lSupAwQ
|A little pot of decidedly impure manganese dioxide...but it came from the rubbish dump!|