Attempts to determine nitrogen in shale oil or its fractions by the Dumas micromethod generally resulted in high and variable results. The mass spectrometer was used to analyze the gases in the nitrometer. The presence of hydrocarbons and nitric oxide indicated that proper techniques were not being used in the combustion. The ability to detect extraneous gases and to identify them provides a tool by which the effectiveness of the procedures may be tested. Revision of the procedure until only nitrogen is collected in the nitrometer results in good analyses. In some instances corrections may be applied to nitrometer readings containing extraneous gases, so that acceptable results are obtained.