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Quaternary Ammonium

An organic chemical group of cationic surface active compounds that tend to take up and hold on to surfaces of other substances; the group consists of ammonium (NH4) compounds in which one or more of the hydrogen atoms attached to the nitrogen are substituted by organic radicals.

Quaternary ammonium compounds are strong bases, and their salts (formed by reaction with acids) provide the exchange sites on certain anion exchange resins.

Quaternary ammonium salts in which the "active" ingredient is sufficiently high in activity and concentration can be used in water treatment as microbiocides (microbe killers) and surfactants. Cationic quaternary ammonium compounds adsorb the cell membranes of the microbes and react chemically with the negative charges carried by the cell walls to inactivate and kill the microorganism.