Nitrogen Compounds (e33b9731-2e23-4a0d-b05e-78358a11166f)

Nitrogen, and its compounds, unique among the materials described in this volume, is absolutely essential to the existence of the human race. Almost all minerals are important and the absence of any one of them would be sorely felt; but nitrogen is an integral part of the cycle of life itself. Man cannot live without nitrogen which, as an inert gas, composes the major part of the air he breathes; as compounds, nourishes the vegetation which he eats; and, as protein, forms a part of his very flesh and blood. Nature originally provided man with a vast reserve of usable nitrogen compounds in the form of fertile soil. She constantly replenishes the supply by "fixing" nitrogen in the air at the estimated rate of 400,000,000 tons per year (an insignificant 6 lb per acre) during electrical storms. She has also placed certain microorganisms in the soil which are able to "fix" nitrogen and convert it into forms which plants can use. Legumes like cow peas, soy beans, clover, and alfalfa have extraordinary roots which serve as stimulating hosts to these bacteria which, in turn, nourish the plant. By plowing in all or part of such crops, their above-average nitrogen content can be returned to the soil for other more useful crops. The mechanism for this recycle is supplied by "denitrifying" bacteria which attack the dead plant tissue and liberate nitrogen and ammonia. However, since one crop of grain, sugar beets, potatoes, tomatoes, etc., takes out a major portion of the nitrogen which a plowed-in legume crop can supply, this method of fertilization is obviously inadequate. Drastic intervention by man has become necessary to support the ever-growing population of the world.9,15,20 Old civilizations with a high population density, such as the Chinese, were able to exist for centuries by carefully tilling the soil, rotating crops, and returning to the soil all the nitrogen in vegetable wastes plus human and animal excreta. But the lack of a means for augmenting their supply of nitrogen placed a ceiling on further development and kept the mass of the population in a chronic state of undernourishment, frequently punctuated by famine. Nitrogen plays another important role in the life of mankind. In the form of explosives, nitrogen helps to wrest from the earth many materials needed for our material well-being. Also, in the form of explosives and propellants, nitrogen increased the destructiveness of wars to a point only exceeded by the fantastic power of atomic energy. Man's first really effective efforts to improve his position with respect to nitrogen began in the 18th Century with the mining of sodium nitrate. By the late 1880's this had become a big industry serving a large part of the world. In the late 1890's nitrogen, in the form of ammonia, was being recovered from coke-oven operations. In 1900 nitrogen, in the form of nitric oxide, was being obtained from the air by an electric-arc process. About 1904 another "fixation" process based on the reaction of nitrogen with calcium carbide to form cyanamide was commercialized. By 1913 the Haber-Bosch process of "fixing" atmospheric nitrogen by reacting it with hydrogen to produce synthetic ammonia was successfully applied on a large scale, first in Germany and then throughout the industrial areas of the world.9 All the above methods of obtaining nitrogen compounds are still in use and, between them, they assure mankind of adequate supplies for all time. While this fortunate situation is not unique amongst industrial raw materials, all too few of man's needs are so well in hand.