n. Symbol K
A soft, silver-white, extremely reactive element that is an alkali metal, is essential to plant and animal cell functions, and occurs in nature only in compounds. It can be obtained by electrolysis of its hydroxide and is found in, or converted to, a wide variety of salts used especially in fertilizers and soaps. Atomic number 19; atomic weight 39.098; melting point 63.5°C; boiling point 759°C; specific gravity 0.86; valence 1. See Periodic Table.
[From earlier potass, potash (from which it was first obtained), from French potasse, from Dutch potas : pot, pot (from Middle Dutch; akin to Old English pott) + as, ash (from Middle Dutch asche; see as- in the Appendix of Indo-European roots).]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
The American Heritage Dictionary Blog
Check out our blog, updated regularly, for new words and revised definitions, interesting images from the 5th edition, discussions of usage, and more.
American Heritage Dictionary Products
The American Heritage Dictionary, 5th Edition
The American Heritage Dictionary of Idioms
The American Heritage Roget's Thesaurus
Curious George's Dictionary
The American Heritage Children's Dictionary
The American Heritage Dictionary of Indo-European Roots
The American Heritage Student Grammar Dictionary
The American Heritage Desk Dictionary + Thesaurus
The American Heritage Science Dictionary
The American Heritage Dictionary of Business Terms
The American Heritage Student Dictionary
The American Heritage Essential Student Thesaurus