Abstract: The residual ammonia in fly ash was measured by Nessler’s reagent spectrophotometry method, neutralization titration method, and ammonia-sensitive electrode method respectively in this paper. The main influence factors and their values were determined and the correlation among results of these three methods were investigated in detail. Results showed that the main influence factors of Nessler’s reagent spectrophotometry method were extraction solvent (best as 0.05 mol/L H₂SO₄), liquid ratio (optimum as 1∶10), and extraction time (optimum as 30 min); the main influence factors of neutralization titration method were absorption solution(best as 0.05mol/L H₂SO₄), sodium hydroxide content (optimum as 0.2 g) and distillation time (optimum as 30 min); the main influence factors of ammonia-sensitive electrode method were extracting solution (best as deionized water) and stirring time (optimum as [10, 25] min). In addition, the results of the three methods are of good correlation.

Key words: fly ash, residual ammonia, measuring method, influence factor, Nessler’s reagent spectrophotometry, neutralization titration method, ammonia-sensitive electrode method, correlation