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 the
range 0.5-9.0 g ml and the Sandell's sensitivity for 0.001 absorbance unit is 16.7
ng cm . The method is simple, rapid and free from interferences of several cations
and anions which are usually present with NH ion in real samples