Chemistry and the World's Food.

Progress, Volume I, Issue 12, 1 October 1906, Page 337

Chemistry and the World's Food.

Synopsis. In the previous article on this important subject Professor Duncan enlarged upon the various forms of fixed nitrogen which we have with us, and which we are continuously using up, and must continuously restore. The author showed how we consume fixed nitrogen in the form of animal food or of certain plant products, such as wheaten bread ; but, as pointed out, plants and animals themselves depend upon the soil for every trace of the nitrogen they contain, and the soil is so inadequately charged with this nitrogen that we and the lower animals filch what it contains much faster than it can be restored by natural processes. Meanwhile, the land grows sick and barren and refuses to grow our crops ; consequently, we have to cure the land and mix with it manure or fertiliser. The natural manure of the world is, however, a " mere drop in the bucket of our wants ; " and Professor Duncan goes on to say that m Professor Adolph Frank's wonderful discovery "we see the unwilling nitrogen, fixed by the genius of man into the active and useful form, working not only m the thousands of nitrogenous substances used m our civilisation, but m the soil, m the plant, and causatively in the actions and thoughts and feelings of men, until, freed of its energy, it sinks back into the Nirvana of the empty air."

SECOND PAPER. Now, resting on every seven acres of earth there are 237,000 tons of nitrogen, sufficient, if we could burn it, to replace the 1,500,000 tons of saltpetre consumed last year. That we could burn this amount we know, but how to burn it m the cheapest way has still to be discovered. The whole question of its economic burning bristles with difficulties. Not only is the ignition point above the temperature of its flame, but the temperature of the union of the nitrogen and oxygen of the air is perilously close to the temperature of its dissociation, and there results an awkward equilibrium point at which the nitrogen oxides are decomposed as fast as they are formed under the action of the arc. The prize of burning the air is certain riches, but how to proceed is the present question. Is it wise to employ arcs depending upon great electric intensity and small volume, or great volume and small intensity ? What kind of electrodes should be used — carbon or platinum, or what ? Should the air be compressed,

should oxygen be added to it, or should it be dealt with as it is ; and, moreover, how shall we be rid of the equilibrium point ? Among the race of chemists and chemical engineers, many men have been busy in the attempt to solve this momentous problem. There is the Atmospheric Products Company at Niagara Falls, where, through their earnest and intelligent efforts to solve this problem, Messrs. Bradley and Lovejoy have won high praise and cordial recognition from all the other workers in this field of investigation. The fact of this recognition is significant ; it means that there is room enough for all. These

gentlemen believe in sparks of hign intensity, and they seem to have perfected their method to the limit of its powers. The operation is carried out in a sparking chamber which consists of a large cylindrical metal box lined in the interior with vertical rows of contact points, each one of which is m connection with the positive pole of a dynamo generating a direct current of 8,000 volts. Now, inside the chamber rotates a central shaft provided with a similar set of negative contacts in the form of long rods, and all connected, of course, with the negative pole of the dynamo. But this cylinder is rotating at the rate of 500 revolutions a minute, and as each negative contact comes up to a positive, it strikes an arc which is drawn out and extinguished as the negative contact moves past anu away from the positive. In the illustration we see the cylinder at work at the instant of revolution, and since there are many revolutions and many contacts, there are no less than 400,000 arcs a minute. It is like the inner cylinder of a music- box ringing out sp<±rks instead ot sounds. But air is drawn inrougn these multitudinous sparks, and each spark as it forms burns a small per cent, of tne incoming air into oxide of nitrogen. The result is that some two per cent, of the outgoing air is converted into oxides, which are caught in absorbing towert> of water with the formation ol nitric acid, or of soda with the formation of saltpetre or sodium nitrite. From data based upon the actual running of this plant, nitric acid may thus be produced from air and water at a cost of about one penny a pound, and since the market price is about twopence halfpenny, it ought to De a profitable operation. But this is tor nitric acid, and large as is the market for this substance, it is not limitless, as is the case with saltpetre. Whether the acid may be combined with soda to form artificial nitrate, at a rate capable of competing with the natural product, is still a matter ot doubt ; it depends on the price of soda. Away off on the coast of Norway, where they have cheap water-power and cheap labour, other men are still engaged in the practical elucidation of this same problem. Professor Kr. Birkeland and Dr. S. Eyde, of Chnstiama, have developed a process by which the air is conveyed into a series of ovens. Each one of these ovens contains two metal electrodes, between which plays a highpressure flaming electrical arc. The arc is moved rapidly hither and thither by a powerful magnet, in such a way that the maximum amount of oxidation is obtained. In accordance with data submitted by the company, about 2000 pounds of nitric acid may thus be synthesised with an energy expenditure of only one kilowatt-year. At the present price of nitric acid this means a most respectable profit, and it is not surprising, therefore, to learn that they already employ 2000 horse power for burning the air. E. Rossi, of Italy, proceeds m still another way. He obtains improved results by oxidising the air under heavy pressure. The oxidation is brought about by an incandescent substance similar to the filament of a Nernst lamp, and the equilibrium point is avoided by absorbing the burnt nitrogen oxides with concentrated sulphuric acid flowing constantly through the interaction chamber. Among the Germans the great firm of Siemens and Halske has been intermittently busy ever since 1884, when old Werner Siemens sent a letter to his assistant directing him to experiment on the fixation of nitrogen. Dr. George Erlwein, who has present charge of this investigation, does not hold with the experiments just described. Instead of a multitude of intense little sparks of high-potential flaming arcs, he employs an arc formed by an enormous current at low voltage. He points out, and very truly, that increasing the size of these other plants will not increase their efficiency, while, in his own case, he finds that the greater the size of the arc he can form (the greater the unit in his factory), the greater is the per cent, of the nitrogen burnt. He has also provided against the easy decomposition of the burnt nitrogen into free nitrogen, by mixing the carbon of his huge electrodes with powdered fluor-spar, thus decreasing the temperature of the arc. At present this firm is resting on what they have so far accomplished, and for a most significant reason. They have no more doubt than other people that they can profitably make nitric acid out of air and water, and at a rate concurrent with the present market price, but they are not satisfied with the market thus afforded, immense though it is. They demand the exploitation of the whole saltpetre industry as well, and nothing else will satisfy them. They deny that at present the electric nitre can compete with the natural product ; hence they prefer to wait until a little further advance in pure science brings it within their grasp. Calcium is one of the few elements that have the power to unite directly with nitrogen. It is

a silver-coloured metal, which with comparative ease burns nitrogen, to form a nitride, and this nitride, on being thrown into water, yields ammonia and lime. Hence, if we could obtain calcium cheap enough, we could obtain ammonia cheap enough, and this would solve the problem of nitrogenous manure. Ten years ago this would have been visionary nonsense ; to-day, were there no other means at our disposal, this is the very scheme we should quickly take measures to cheapen and adopt. Two years ago calcium was worth three pounds a thimbleful ; to-day it is worth about five shillings a pound, and its price might be greatly reduced. It is a very common metal, because every bed of limestone contains nearly forty per cent, of it ; in the past it was very rare because of the difficulties of its extraction. To-day, calcium is made by

the ton, by decomposing the melted chloride of calcium by a current of electricity. The metal attaches itself to the cathode, and by slowly lifting the cathode a long " cabbage stalk " of the metal is produced. Fortunately we do not need to worry over the still cheaper production of calcium, for, working m one of its compounds, this same metal has solved our problem in another way and with such success that it has temporarily thrown into secondary importance all the other processes we have so far considered. Everybody has heard of calcium -carbide, and of the bright illuminating gas, acetylene, which it evolves when thrown into the water. The story of the carbide discovery, its manufacture, the fond hopes of the investing public that they could displace by acetylene the ordinary illuminating gas which the manufacturers could afford to sell for nothing, their disappointment, the revivification of the industry, and the latest phase of its usefulness, is a story of high romance and high finance. We are concerned here only with its latest phase. It occurred to Professor Adolph Frank, of Charlottenburg, that the easy manufacture of carbides pointed out a way to the commercial fixation of nitrogen. In order thoroughly to test his schemes, he took refuge under the broad segis of the restless, experimenting, progressing firm of Siemens and Halske, whose means and resources were adequate to every human purpose. At first he had in mind only the manufacture of cyanides, by passing atmospheric nitrogen over the heated carbide of barium and converting the cyanide of barium obtained subsequently into the most valuable of the nitrogen compounds, the cyanides of sodium and potassium. He was entirely successful in this operation ; but, in order to still further improve it, he resolved to make a stubborn attempt to utilise the analogous carbide of calcium instead of barium, for it happens that it is not only cheaper, but much more efficient, weight for weight. His attempt resulted in a complete surprise. He found, as a matter of fact, that atmospheric nitrogen reacted with red hot calcium carbide in accordance with a little equation, which, with apologies to the lay reader, we shall insert : ' CaC2 -(- 2N = CaCN2 -|_ C. The result of the reaction is the complete conversion of the carbide into carbon, and into a substance which, while its name sounds something like the calcium cyanide expected, is wholly diiferent from it — calcium cyanamide. Next he discovered that this calcium cyanamide, on being heated with high-pressure steam, passed easily into limestone and ammonia, and finally he found that, on merely spieading out the material in the moist air, it slowly evolved this same substance, ammonia. This led him to the natural

conclusion that the substance might be used as a fertiliser, and to determine the question he sent large quantities to Herr Geheimrat, Professor Wagner, of Darmstadt, to Dr. Gerlach, of Posen, and subsequently to numerous agricultural stations scattered over the country. The result of this experimentation has established beyond all question the fact that, under certain conditions, calcium cyanamide is a better fertiliser than the sulphate of ammonia from the gasworks, and practically equal to the saltpetre from the mines, weight for weight ol the nitrogen that it contains For the growth of wheat it gives its best results when buried four or five inches below the surface of the soil some eight to fourteen days before the seed is sown. The exact mechanism of its action has still to be determined. It is not unlikely that the calcium cyanamide in the soil breaks down into cyanamide itself which in turn decomposes into ammonia, which oxidises into nitric acid, and that the nitric acid so formed unites with the lime constituent of the compound to form calcium nitrate. Under the name of " Kalkstickstoff," calcium cyanamide is now in the markets of the world. The little experimenting Cyanid-Gesell-schaft, which consisted of Siemens and Halske, the Deutsche Bank, and Professor Frank, has turned over the manufacture of Kalkstickstoff to a large company formed for the purpose, the Societa Generale per la Cianamide, of Rome, and this company m its turn consists of the CyanidGesellschaft, the Societa Itahana per la fabbricazione di prodotti azotati, cdi altre sostange per l'agricoltura, and the Societa Italiana per il carburo di calcio acetilene ed altn gas, of Rome. In manufacturing the substance, they employ the latest results of technical science. The atmospheric nitrogen must be separated from the oxygen with which it is mixed. They, therefore, liquefy the atmosphere and separate the two substances by fractional distillation. The oxygen passes off to be used for other purposes, but the nitrogen passes suddenly from the intense cold of liquid air into the highest heat of the electric furnace where, through contact with a mixture of coke and lime, it is caught and transformed into Kalkstickstoff The action of the, Cyanid-Gesellschaft in turning over the fertiliser phase of Kalkstickstoff to the guardianship of another company, has left their hands free to exploit its other uses. These uses are manifold. The fact that calcium cyanamide, under the action of high-pressure steam, passes over all its nitrogen into the form of ammonia leads to an elegant method of making this substance and other ammonium salts The company has at present a demonstration plant in operation for the production oi 1 500 tons of ammonium sulphate a year. But, mixed with carbonate of soda, or with common salt, and fused, the cyanamide passes over into the form oi C} anide of sodium, and this cyanide is useful for a vast number of processes, from silver-plating to gold extraction. They have a plant for this purpose yielding 500 tons a year, and in Mexico, for mining purposes, they are beginning to manufacture the cyanamide directly at the mouth of the mine. A valuable use of cyanamide has been found m a curious function it has of causing the case-hard-ening of steel, and we find the great firm of Ludwig Loeve and Co., for one, continually using laige quantities of it in the manufacture of tools and of arms for the government. An interesting substance easily produced by the action of acids upon calcium cyanamide (with an apology to the reader for its hard name) is dicyandiamide, a beautiful crystalline body containing sixty-six per cent, of nitrogen. This substance, previously known only as a laboratory curiosity, is now made by the ton, and much of it is sold to the dye industries for a purpose that cannot be imagined by the manufacturers. Still other quantities are sold to manufacturers of explosives, owing to the fact that when mixed w r ith other substances it lowers the temperature in the gun barrel. A very interesting property of cyanamide is the ease with which it may be made to unite with water to form urea — a substance occurring naturally in animal excretions. Tons of this artificial urea are now sold to manufacturers of pharmaceutical preparations, though, again, for purposes of which the manufacturers of the urea have no idea. Guanidme, another product of the animal organism, is also made from it, and, we are informed, tons of it are now being sold to America. Still another reaction, of no practical utility to-day, but impressively significant of a thonsand utilities awaiting the hand of future man to develop, is that by which sarcosin unites with this same cyanamide from atmospheric nitrogen to yield creatine — one of the actual substances of human muscle found in extract of meat. From all these facts it is demonstrated that we may look forward with a very reasonable assurance to the creation of as many factories for the fixation of elemental nitrogen as we have smelting

furnaces for the unfixing of elemental iron. Through all these processes we see the unwilling nitrogen, fixed by the genius of man into the active and useful form, working not only in the thousands of nitrogenous substances used in our civilisation, but in the soil in the plant, and causatively m the actions and thoughts and feelings of men, until, freed of its energy, it sinks back into the Nirvana of the empty air. We see, too, that the disaster of which the world actually stood in imminent deadly peril has been averted, and that if every pound of saltpetre in the mines of Chili were suddenly to dissolve into its elements, the human race would still be able to guard itself against the unhumanity of nature. Though, is there this unhumanity of nature ? Say there be ; Yet nature is made better by no mean. But nature makes that mean ; so, o'er the art Which you say adds to nature, is an art That nature makes. Every atom within us moves in harmony with every atom without, and we that think we move them to suit our needs or our caprice are but the crude instruments of a Purpose unfilled and unimagined, but predestinated from the beginning of all things. The present-day practical lesson of this whole strenuous successful work lies m the little object lesson it affords of the immense importance which technical science is assuming in our daily lives and m all our industrial operations. The substitution of real knowledge and high technical skill for the " rule of thumb " of our ancestors has created a revolution in industry. This revolution took its rise in Germany, and it is spreading rapidly to every corner. It is spreading silently, too, because it does not pay to tell. During the next five years, the small manufacturer who is swept out of existence will often wonder why. He will ascribe it to the economy of large-scale operations, or business intrigues, or what not, never knowing that his disaster was due to the application of pure science that the trust organisations and large manufacturers already are beginning to appreciate.