ON THE APPLICATION OF THE DUMAS TECHNIQUE FOR THE DETERMINATION OF NITROGEN IN REFRACTORY NITRIDES

The classical Dumas apparatus has been modified. The generally recommended oxidants CuO and V2O5 were found to give relatively high blank values and were therefore replaced by Cu2O. The preparation of the Cu2O is described. It is an exceptionally suitable oxidant for the Dumas analysis of the Group Va nitrides as well as manganese nitrides and molybdenum nitrides because it does not release oxygen into the gas phase. The reaction of the Group IVa nitrides as well as of CrN with CuO and Cu2O is, however, not completely quantitative at 1000-1150-degrees in reasonable reaction times. The results of the Dumas analysis of a Group IVa nitride should be corrected by measuring the nitrogen content of the residue (e.g., by hot extraction). The relative standard deviations do not exceed 0.38%. The nitrogen contents (% w/w) of the residues range from < 0.001% for Mo2N + MoN to 0.54% for Cr2N + CrN. BN, Si3N4 and AlN could not be decomposed with copper oxides under the conditions used. AlN could be analysed by adding V2O5, but the rsd was 0.55% and the nitrogen content in the residue was 0.52% w/w. Neither BN nor Si3N4 could be analysed by addition of V2O5.