Benzalkonium Chloride is a viscous, aqueous solution of quaternary ammonium compounds. Benzalkonium Chloride is a very efficient germicide that is active against most common micro-organisms, such as bacteria, fungi, and algae. Benzalkonium Chloride is widely used in pharmaceuticals as the active ingredient (API) due to its anti-microbial effect and as an excipient due to its preserving properties.