Rapid dissolution technique for colorimetric determination of nitrogen in coals

✍ Scribed by Glenn A. Norton; Neal S. Adams; Richard Markuszewski; Scott V. Brayton

• Publisher: Elsevier Science
• Year: 1987
• Tongue: English
• Weight: 842 KB
• Volume: 66
• Category: Article
• ISSN: 0016-2361
• DOI: 10.1016/0016-2361(87)90342-5

✦ Synopsis

A simple and rapid method for the calorimetric 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 H,SO, followed by digestion using continuous-flow addition of a mixture of 50% H,O, plus concentrated H,SO,.

Nessler's reagent is added for colour development for the subsequent spectrophotometric determination ofammonia nitrogen. Maximum nitrogen recovery was obtained by using boiling times of 4 min or more during sample carbonization, H,0,:H,S04 ratios of 4:l to 9:1, and digestion reagent volumes of 2&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.