Cyanamid Fixation.
—Hot calcium carbide will absorb nitrogen, forming a compound of calcium, carbon, and nitrogen, according to the formula Ca CN2, known as cyanamid. The cyanamid process, based on this reaction, has been extensively developed, far more so than any other of the various processes, as will be seen by referring to [Figure 16] and [Table 66]. Offhand, it looks to be the most adaptable and consequently the most promising of the lot commercially. In this connection, however, it is interesting to examine the several charts of its growth in the warring countries given in [Figure 16]. In none of these is the showing indicative of a strong, healthy development. Worst of all is the case of Germany, with the contrast offered in the Haber and cyanamid charts. Until the war, cyanamid manufacture was unable to obtain a competitive foothold in the United States, although a small plant has been in operation at Niagara Falls in Canada for some years. The problem it has faced is similar to that already chronicled for arc fixation, in that it draws heavily on power in the preparation of the necessary carbide, and the cost of power in this country has been prohibitive. Under the stress of the wartime demand for nitrogen, however, the Government contracted for the erection of three plants—one at Muscle Shoals, Ala., one near Toledo, Ohio, and one near Cincinnati, Ohio, with a total rated capacity amounting to 220,000 tons of ammonium nitrate per year. The work on all three was well under way, but none of the plants had reached the producing stage when the signing of the armistice brought the nitrate activities of the War Department to an end.
Nitride Fixation.
—The only process of any prominence aiming to fix nitrogen in the nitride form is one developed by the Aluminum Company of America. This has for its working principle the fact that a mixture of alumina and carbon, highly heated, will absorb nitrogen by reacting to give aluminum nitride. The nitride when heated with caustic soda gives its end product in the form of pure ammonia. The outstanding difficulty encountered in applying this process commercially seems to be that of providing a furnace capable of standing the temperature requirements. At all events the process has not succeeded in making good industrially.
Bacterial Fixation.
—The artificial attempts at fixation have been directed almost wholly toward employing chemical principles. In view of the difficulties experienced and the uncertain value of the results as a whole, it is interesting and perhaps highly significant to reflect that after all, as indicated in [Figure 15], inorganic chemical principles seemingly have little to do with developing the natural supply, probably because of the activities of nitrifying bacteria. Little attention has been given to the possibilities in this direction. This is only natural so far as commercially actuated research is concerned, since it does not lead in the definite direction of patent rights; but the failure to institute an adequate investigation governmentally can be attributed only to lack of comprehension with reference to the scope of the nitrogen issue as brought out under “General Aspects of Control” on [pages 425] to [433]. The subject has received just enough attention to show that bacterial fixation represents a tremendous field of grossly neglected possibilities.
RECENT DEVELOPMENTS AND CHANGES IN PRACTICE
The whole matter of fixation must be regarded as in process of development. True, it was instituted some fifteen or twenty years ago and has grown to represent the largest producing source of chemical nitrogen, with operations in practically all the important industrial countries in the world and with responsible financial backing. But no one can examine the charts in [Figure 16] without recognizing the premature, mushroom quality of the upgrowth, induced primarily in response to the political conditions leading to and through the war. This is especially true for the American situation. When the war broke out, fixation here was confessedly still in the dependent stage of its development, unable in every effort it had made to stand alone industrially. In the main, the developments that have transpired subsequently have followed along pre-existing lines. In so far as they have done so, little actual economic significance is to be attached to them. For the rest, the new developments, all that can be said at this juncture is that they are disappointingly meager.
Just one wartime achievement, the oxidation of ammonia, stands out as affording a worth that is unmistakably clear. The nitrogen situation, it will be recalled, has two aspects, the military and the agricultural. The military focus is on nitric acid, and the readiest means of insuring a supply; the agricultural focus is on ammonium compounds or their equivalent in neutral nitrogen salts and the most economical means of supply. Here, then, is a parting of the ways to expediency, and it is at this juncture that with military influences to the fore the nitrogen developments of the past few years were led off on an uneconomical tangent of military control. The Bureau of Mines, however, taking up the work of others, has perfected a simple, effective means for oxidizing ammonia to nitric acid. This, beyond question, is the most important contribution of the day. Its significance may perhaps best be brought out graphically in the accompanying sketch.
