Nitrogen determination in coal and coke with an ammonia electrode

The selective-electrode procedure described for determining 0.2-2.5% of nitrogen in coal and coke offers significant advantages over Kjeldahl distillation and titration. The Kjeldahl digest is diluted, neutralized, cooled, diluted to volume, adjusted to a standard temperature and rendered alkaline prior to measurement with an ammonia-selective electrode. Accuracy and precision of 1% relative are demonstrated by comparative analyses of a range of samples. Important experimental aspects discussed include the role as neutralization indicator played by vanadium derived from the catalyst, precision of the mV-meter, the influence of solution temperature and concentration, the repeatability of the readings, and interferences.