The construction of a rapid automatic micronitrogen analyzer is described. Analyses can be completed in 6 to 15 minutes. The errors involved in the use of such equipment and how to minimize them are discussed.The importance of rapid procedures for the determination of nitrogen is evident from the numerous publications (S, 6, 7, 9, 11) on this subject and the references cited therein. A significant advance was made with the successful introduction (2) of a commercial automatic nitrogen analyzer, and this led us to investigate the possibilities of constructing a similar unit from combustion equipment already existing in our laboratory. It was decided, at the outset, to automate the Shelberg (10) procedure for the analysis of nitrogen since its efficacy as a rapid method is well documented (3, 6, 7). This paper, to a large degree, will be limited to a description of the apparatus and its operation. APPARATUSInstrumentation. The Shelberg (10) micro Dumas nitrogen procedure and its modifications lend themselves easily to automation (3). In principle, two combustion tubes separated by a threeway stopcock are used. The sample is burned in the one containing copper oxide, and the nitrogen oxides are reduced in the second tube containing copper and copper oxide. The stopcock permits the sample tube to be flushed free of air with carbon dioxide without