any of a class of salts derived from ammonium in which the nitrogen atom is attached to four organic groups, as in benzalkonium chloride; the salts are cationic surface-active compounds used as antiseptics and disinfectants.
- Also called quaternary ammonium salt .
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British Dictionary definitions for quaternary ammonium compound
a type of ionic compound that can be regarded as derived from ammonium compounds by replacing the hydrogen atoms with organic groups
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