“PYROGALLOL AS A REAGENT FOR SPECTROPHOTOMETRIC DETERMINATION OF AMMONIUM-NITROGEN (NH -N) IN AQUEOUS SOLUTION: ”. (2003) Biological Sciences - PJSIR, 46(2), pp. 141–144. Available at: https://www.v2.pjsir.org/index.php/biological-sciences/article/view/1612 (Accessed: 10 March 2026).