THE fixation of atmospheric nitrogen on a commercial scale has already been the subject of articles in NATURE (February 8, 1906; August 30, 1906; July 23, 1908). The method used by Birkeland and Eyde depends upon the well-known fact that an electric arc may be broadened out into a fan shape under the influence of a magnetic field. Through the arc thus formed air is driven. Since, however, only a small portion is raised to the temperature necessary for the reaction, while the greatest part serves for cooling, the gases escaping from the Birkeland furnace at a temperature of from 600° C. to 700° C. do not contain more than from 1 per cent, to 2 per cent, of nitric oxide. For further cooling, the gases are led under boilers or through a distilling apparatus, and, finally, at a temperature of about 50°, into an oxidation chamber, where further oxygen is taken up, forming nitrogen dioxide, which in turn is absorbed by water, and thus converted into nitric acid.