potash

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of several compounds containing potassium, especially soluble compounds such as potassium oxide, potassium chloride, and various potassium sulfates, used chiefly in fertilizers.

from The Century Dictionary.

• noun A substance obtained by leaching wood-ashes, evaporating the solution obtained, and calcining the residuum; one of the fixed alkalis; the so-called vegetable alkali; more or less impure or crude potassium carbonate, or carbonate of potash as formerly generally (and still very frequently) designated; any combination of which potassium forms the base, whether containing oxygen or not.

from the GNU version of the Collaborative International Dictionary of English.

• noun The hydroxide of potassium hydrate, a hard white brittle substance, KOH, having strong caustic and alkaline properties; -- hence called also caustic potash.
• noun The impure potassium carbonate obtained by leaching wood ashes, either as a strong solution (lye), or as a white crystalline (pearlash).

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun the water-soluble part of the ash formed by burning plant material; used for making soap, glass and as a fertilizer
• noun chemistry an impure form of potassium carbonate (K2CO3) mixed with other potassium salts
• noun chemistry, archaic in the names of compounds of the form "... of potash", potassium (for example, "permanganate of potash" = potassium permanganate)

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a potassium compound often used in agriculture and industry