Studies on invert soaps. II. Colorimetric determination of benzalkonium chloride using phosphomolybdic acid

A Specific Method of Assay of Strong Solutions of Benzalkonium Chloride and Other Quaternary Ammonium Germicides

A method of assay of quaternary ammonium germicides in strong solutions or concentrated solid form is described. It can be used for solutions down to about 1 per cent in content. A known excess of iodide is added to the sample solution and the quaternary ammonium iodide is removed by shaking with chloroform. The excess iodide is titrated by an iodate method. When the chloroform extraction is made from a slightly alkaline solution only quaternary ammonium compounds are measured; if it is made from a slightly acid solution, non-quaternary cationic amine impurities are also included. The difference between assay results obtained from acid and alkaline extractions represents the non-quaternary amine content.