An extraction-spectrophotometric method for the determination of trace amounts of ammonium ion is described. Ammonium ion is effectively extracted as a neutral ternary complex NH . DB 18C6. calmagite at pH 3.0 into chloroform, followed by spectrophotometric determination at =48 5 nm. Molar absorptivity of the ternary complex at this wavelength is 1.08 10 mol cm . Beer's law is obeyed over...