METHODS OF MICROANALYSIS. IV. STATISTICAL EVALUATION OF THE DUMAS NITROGEN DETERMINATION

Research was undertaken to determine the reliability of the method developed for the microanalytical determination of N by a modified Dumas procedure. Realistic estimates of the precision obtained by using the modified tube filling and an 800 C combustion were established by statistically analyzing measurements made on standard reference compounds on different days by three analysts using two sets of apparatus. Use of the Ni oxide-Cu-Cu oxide tube filling with a 900 C pyrolysis temperature has provided a method that is relatively simple and uses conventional laboratory equipment of moderate cost and lowmaintenance requirements. This modified method has excellent precision and gives accurate results on both tractable and refractory compounds. The standard deviation of the differences between theoretical and observed values for 90 compounds of established purity and known nitrogen content is 0.091. Author