Treatment of substances with boiling HI results in no loss of N on subsequent oxidation of hydrazino-, nitro-, nitroso-, and azo-compounds. Those which are volatile, or form volatile decomposition products (cyanogen compounds), or contain N in the ring such as anti-pyrine must be treated in a closed tube. Diazo compounds can be analyzed by this method if transformed into the stable azo form by phenol. This method permits microkjeldahl determinations on all compounds with organically bound N; it does not accurately analyze alkali nitrates.