Rapid Dissolution Technique for Colorimetric Determination of Nitrogen in Coals.
Norton-GA; Adams-NS; Markuszewski-R; Brayton-SV
Fuel 1987 Jul; 66:996-1001
A simple and rapid method for the colorimetric determination of total nitrogen in coal has been tested on several coals digested under various conditions. The method consists of initial carbonization of the coal sample with h2so4, followed by digestion using continuous-flow addition of a mixture of 50 pct h2o2 plus concentrated h2so4. Nessler's reagent is added for color development for the subsequent spectrophotometric determination of ammonia nitrogen. Maximum nitrogen recovery was obtained by using boiling times of 4 min or more during sample carbonization, h2o2:h2so4 ratios of 4:1 to 9:1, and digestion reagent volumes of 20 to 40 cm3. Altering the heat setting on the digestion apparatus substantially changed digestion times but did not significantly affect nitrogen values obtained. Using the optimum digestion conditions, results for nitrogen in seven different coal samples were comparable with those obtained by conventional determinations using an instrumental chn analyser. The precision of this rapid dissolution technique was good and appeared to be better than that of the instrumental analyser for many of the coals studied.
OP; Final Contract Report;
Fuel, V. 66, July 1987, PP. 996-1001
Iowa State University