An alternative method is to test for the production of ammonia from urea by means of Nessler's reagent (1) and/or to detect NH3 production due to L-arginine, Nessler reagent (K2HgI4) is a solution prepared by combining sodium hydroxide and potassium iodide with mercuric chloride or mercury iodide. When reacted with gaseous ammonia, it produces brown fumes. When passed through a solution of ammonia, it produces a dirty brown precipitate
