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N o w AND TEACHERS' COLLEGE ESSAYS
FIXATION OF NITROGEN* RAEPH D. SPEARS, STATE T&AcRERs' COLLEGE, SLIPPERY ROCK.PENNSYLVANIA Ye rigid Ploughman. Bear in mind Your labor is for future years. Advance1 Spare not; nor look behind. Plow deep and straight with all your powers
Ever since the race of man began, food bas been the vital question. The early cave men who were the seeds of civilization existed only because they were able to overcome the disintegrating forces of nature, disease, wild animals, and their weaker fellowmen in their quest for food. As man advanced, his food problem became more complex until he finally turned to the cultivation of the soil in order to produce plants that would help sustain him. Plants became the food of the entire animal kmgdom. It is an established fact that all living things, whether of flesh or fiber, must have food in order to promote growth and support life. Plants, as the source of that food, must receive nourishment, too, in order that they may not only meet the constant demand, but go even beyond that to provide for future use. There must be certain chemical elements within reach of the roots of the plant for its own sustenance. More than fifteen elements are necessary but, ordinarily, the supply is great enough for the plant's demands, except in the RALPHD. SPEARS case of nitrogen, potassium, and phos phoms. These elements are fatal to plants in elementary form; and in order that they may be absorbed, they must be fixed in neutral salts. For the last three hundred years, the American people have been reaping their harvests from virgin soil, but now that all our land is occupied, we must learn, as others before us have learned, how to keep up the supply of plant food which was so plentiful in the new soil. Not until this deficiency in the soil has been heeded, will America be able to keep her place with other agricultural countries of the world. Just as food is essential in man's existence, nitrogen is indispensable in the life of a plant. The necessity for it has long been known. Early * Prize-winning normal-xhaol and teachers' college essay, 192829.
chemists knew it to be a part of most animal and vegetable matter and to be necessary for life. It was discovered in 1772, hut until 1900, very little use had been made of the discovery. Nitrogen is found abundantly in the air, but it will scarcely ever unite with other elements, and very few plants are able to use free nitrogen. As time went on, cultivated plant life so depleted the supply of nitrogen in the soil, that its restoration became a vital problem for the agriculturist. But why should the soil be so impoverished for nitrogen, when the earth is being constantly bathed in an atmosphere four-fifths of which is composed of nitrogen. It is estimated that there are 20,000,000 tons to the square mile of nitrogen pressing down upon the earth. It might seem impossible that there should be a shortage of nitrogen in the earth's crust. The difficulty is that it will not combine readily with other elements. All growing plants use nitrogen and when the plant is grown and used for food, the amount of nitrogen removed from the soil is enormous. A good wheat crop removes nearly 50 pounds per acre. It would require 200,000,000 tons of ordinary mixed fertilizer to replace the amount extracted from all the land cultivated in the United States each year. After many vain attempts to comb'me nitrogen with other elements, Sir William Crookes, a well-known British chemist, made the following statement before the British Association for the Advancement of Science, in 1898: "The fixation of nitrogen is vital to the progress of civilized humanity. The fixation of nitrogen i s a question of the not far-distant future. Unless we can class it among cepainties to come, the Caucasian race will cease to he the foremost in the world, and will be squeezed out of existence by races to whom wheaten bread is not the staff of life." The years of plenty were passing. The supply of wheat, which is the staple foodstuff of the Western people, would soon be insufficient to provide for the needs of a growing population. Unless the yield of the soil could be greatly increased by intensive cultivation, famine would literally stare us in the face, and intensive cultivation would exhaust all the known sources of nitrogen in a few years. Sir William Crookes' warning was timely, for nothing was being done to increase the supply of nitrogen, and famine of the soil was inevitable. Nitrogen is used, not only to enrich the soil, but, also, in the manufacture of dynamite, gunpowder, dyes, and other products. Enough nitrogen was thrown away in one decisive battle of the World War to save India from famine. The population was not lessened to any great extent, but the soil was robbed of its power to support the population. "Plants rise on the stepping stones of their dead selves to higher things." Each new plant lives on the humus made by the old plant and what it is able to add from the air and sunshine. As soon as a tree or leaf falls, myriads of bacteria and fungi break it up into its component parts called
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NOXMAL AND TEACHERS' COLLEGE ESSAYS
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humus. Other bacteria change the nitrogen in the humus to ammonia; still others to nitrites; and a final group converts nitrites to nitrates. These phenomena help to replace the amount of nitrogen extracted hut do not increase the supply. The methods of agriculture used by early man were sound and productive. He learned to sow pea-like plants every third year and to plow them under to increase the productivity of the soil. Animal manure has been used for ages as a fertilizer. It contains nitrogen, phosphorus, and potash, and is a means of returning part of the nitrogen taken from the soil by the plant. The fertilizers known to early farmers were not sufficient, though, to replace and increase the supply of food derived from the soil. The Indian, long before the white man came to Ameri.ca, found that he could enrich the soil around his corn plant by putting a fish in with the seed. He knew that it would increase his corn yield. The early settlers soon acquired the same method and, later, learned to use other material as the nitrogen-giving element. Fixation of nitrogen is the process of converting free nitrogen into nitrogen compounds. Certain bacteria which are able to fix nitrogen have made agriculture and all plant life possible. Nitrogen can be obtained through leguminous crops but it is not believed to he much cheaper to secure it thus than to nse commercial fertilizer. However, the fact remains that some day the farmer may be able to control the bacterial life of his soil so as to insure an abundant supply of nitrogen. When fertilizer was discovered, nitrogen waS one of its constituents. One source of supply was found in the rich deposits of guano on the Chmcho Islands off the coast of Peru. Here, millions of penguins and pelicans had lived for centuries, piling up their excrements, dead birds, and fish to the depth of 120 feet. This deposit was rich in nitrogen but the supply was soon exhausted by the removal of a billion dollars worth of the guano. In the mainland of Peru and Chile, there were similar accumulations of guano, deposited as sodium nitrate. The origin of these beds is not known, but they occur in patches four to twelve feet deep. This Chilean nitrate has been used as a source of nitrogen for soil purposes for nearly one hundred years. In 1830, only a few thousand tons were shipped, but in 1913, two million tons were exported.' Altogether, 35,000,000 tons have been taken from this source in the last twenty-five years. Germany nearly doubled her yield of wheat per acre by using Chilean saltpeter. The chief drawback has been that this product is rather expensive. However, other successful methods of obtaining nitrogen are now setting up rivalry which will result in a lowering in price of the Chilean saltpeter. There has been a lot of discussion as to how long this supply will last. The promoters claim that it will last a thousand years, hut govcrnment inspectors,
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JOURNAL OF CHEMICAL EDUCATION
OCTOBBR, 1929
not nearly so optimistic as the promoters, assure us that the supply will not be exhausted, a t least, for one hundred years. The amount of nitrogen received from coal, peat, silt, and lignite is very important. When coal is heated in ovens for making coke, a large amount of ammonia comes off. It is caught in sulfuric acid and used as ammonium sulfate. For years this product had been escaping into the air, and we were losing 700,000 tons of ammonium salts per year. The ovens have been changed now, and in 1919, 1,466,000 tons of ammonium sulfate were secured from the distillation of coal. There are peat moors in New England and in Asia which supply a large amount of nitrogen. There are also 12,000 tons furnished by blast furnaces every year. While this supply is valuable, it is inadequate for the demand. Two smaller sources of this valuable element are waste products and precipitation. There is nitrogen in such waste products as cotton seed meal, meat packers' scraps, fish scraps, dried blood, and tobacco stems. These are called organic ammoniates. However, at this time, many of them are being used in stock feed rather than for soil purposes. The second source of a small supply is the amount received by precipitation. About five pounds per acre of fixed nitrogen is carried into the soil every year by rain and snow. Nature has provided to some extent for the soil's need with a nitrogen cycle. (I) Free nitrogen enters into combination by the aid of bacteria or by electric discharges. (2) Thiscompound, then, enters into the plant as nitrate. (3) The nitrates changed into proteins are transferred from plant to animal. (4) They either remain in the soil in accumulations, or are returned to the air as free nitrogen. It would seem that the supply of nitrogen from the sources already mentioned should be sufficient; but when we consider that, after taking account of the amount returned by manures, leguminous crops, precipitation, and commercial fertilizer, the loss of nitrogen from all lands cultivated in the United States is nearly 4,000,000 tons, we are impressed, then, with the need of a much greater supply. Our population is increasing; therefore, the production must increase. The area of our country is limited; so the solution must come from a greater production per acre. Beside the loss of nitrogen in plant life, there is constant loss in cultivation through leaching and oxidation. Experience has shown that the world's total consumption of nitrogen compounds, in the last few decades, has doubled every ten years. For thirty years, the atmosphere has been recognized as the only source capable of meeting the demand. Many investigations have been made along this line. At the beginning of the World War, the United States felt the need of more nitrogen and Congress made $20,000,000 available, in 1926, for investigation of various methods for the production of nitrate to be used
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for munitions of war and in the manufacture of fertilizers. Germany, alone, knew the latest and cheapest process of fixing nitrogen. It is doubtful if they would have attempted the war without this nitrogen-fixing secret; and it is certain that, without it, they would not have been able to have carried it on as long as they did. Previous to this time, chemists used two methods in fixing nitrogen. The arc process consists of passing air through an electric arc and dissolving in water the small amounts of nitric oxide thus formed to produce nitric acid. This process made use of raw material-air and water; the labor cost was low but the power was very expensive. For this reason, there are very few arc plants in the world a t this time. Norway is the only place where the system is used to any great extent. In 1927, there were only seven arc plants in the world, with a capacity of 46,200 tons of nitric acid. The second process, known to us before the war, is the cyanamide method. I t consists of heating calcium carbide with nitrogen in an electric furnace. The cyanamide is applied directly to the land as fertilizer, and upon exposure to water a t ordinary temperature, it evolves ammonia which, under the action of nitrifying bacteria, is converted into compounds of nitrogen, which are readily absorbed by growing plants. The objection to the cyanamide process was that the power was too expensive. This method is not used in the United States at all now. In 1927, there were 28 cyanamide plants in the world, with a capacity of 313,500 tons. The method for fixing atmospheric nitrogen, which Germany employed during the war, has since been carried out in the United States on a large scale. It is known as the Haber process by which nitrogen and hydrogen are used and the result is ammonia. The agent used is some rare metal, such as platinum, uranium, or osmium, which acts catalytically to decompose the elemental molecules and recombine the atoms in anew form. The ammonia produced is changed into nitric acid. This method is by far the most important because of the ease of manipulation and the relative cheapness of the necessary materials. It is one of the processes originally designed for use a t Muscle Shoals, Alabama, where the plant erected during the war is the largest undertaking of this kind. Great influence is being used now to reopen this plant for soil fertilization purposes. A cheap source of nitrogen would go a long way in solving some of the farmer's economic problems and would enable him to reduce his cost of production greatly. When nitrogen is purchased in commercial fertilizer, it is the most expensive plant food present, and its use is frequently prevented because the value of the increased crop is not sufficientto pay the cost of the fertilizer and also yield a profit to the farmer. In the last analysis, probably all of the nitrogen from the various sources came from the air, for it is an element which easily escapes from chemical
combinations. Once free, it is only with difficulty that it can be made to combine with anything else. The problem, then, of fixing nitrogen has required much research and investigation, but a knowledge of its value to the soil and the liberal use of it will repay all time and effort spent upon the project. "It has been truly said that in the present state of civilization, a nation lacking an adequate supply of nitrogen can be neither great in peace nor in war." Bibliography Slosson. E.%*.,"Creative Chemistry," The Century Co., New York City, 1919. Chamberlain, Jos. S., Editor, "Chemistry in Agriculture," The Chemical Foundation, Inc., New York City, 1926. Willaman, John J , "Vacational Chemistry," J. B. Lippincott Co., Philadelphia, Pa., 1921. Stewart, R., "Problems of Muscle Shoals." Current Hisfor?, August, 1928. Davis, R. 0.E., "Muscle Shoals, Nitrogen and Farm Fertilizer," The Annals, Vol. CXXXV, Jan., 1928.
