Transcriber's notes:

Underscores before and after words denote italics.

Underscore and {} denote subscripts.

Footnotes moved to end of book.

The book starts using the word "CHAPTER" only after its chapter number XI. I have left it the same in this text.



The Century Books of Useful Science

CREATIVE CHEMISTRY

Descriptive of Recent Achievements in the Chemical Industries

by

EDWIN E. SLOSSON, M.S., PH.D.

Literary Editor of The Independent, Associate in Columbia School of Journalism

Author of "Great American Universities," "Major Prophets of Today," "Six Major Prophets," "On Acylhalogenamine Derivatives and the Beckmann Rearrangement," "Composition of Wyoming Petroleum," etc.

With Many Illustrations



New York The Century Co. Copyright, 1919, by The Century Co. Copyright, 1917, 1918, 1919, by The Independent Corporation Published, October, 1919



TO MY FIRST TEACHER

PROFESSOR E.H.S. BAILEY OF THE UNIVERSITY OF KANSAS

AND MY LAST TEACHER

PROFESSOR JULIUS STIEGLITZ OF THE UNIVERSITY OF CHICAGO

THIS VOLUME IS GRATEFULLY DEDICATED



CONTENTS

I THREE PERIODS OF PROGRESS 3

II NITROGEN 14

III FEEDING THE SOIL 37

IV COAL-TAR COLORS 60

V SYNTHETIC PERFUMES AND FLAVORS 93

VI CELLULOSE 110

VII SYNTHETIC PLASTICS 128

VIII THE RACE FOR RUBBER 145

IX THE RIVAL SUGARS 164

X WHAT COMES FROM CORN 181

XI SOLIDIFIED SUNSHINE 196

XII FIGHTING WITH FUMES 218

XIII PRODUCTS OF THE ELECTRIC FURNACE 236

XIV METALS, OLD AND NEW 263

READING REFERENCES 297

INDEX 309



A CARD OF THANKS

This book originated in a series of articles prepared for The Independent in 1917-18 for the purpose of interesting the general reader in the recent achievements of industrial chemistry and providing supplementary reading for students of chemistry in colleges and high schools. I am indebted to Hamilton Holt, editor of The Independent, and to Karl V.S. Howland, its publisher, for stimulus and opportunity to undertake the writing of these pages and for the privilege of reprinting them in this form.

In gathering the material for this volume I have received the kindly aid of so many companies and individuals that it is impossible to thank them all but I must at least mention as those to whom I am especially grateful for information, advice and criticism: Thomas H. Norton of the Department of Commerce; Dr. Bernhard C. Hesse; H.S. Bailey of the Department of Agriculture; Professor Julius Stieglitz of the University of Chicago; L.E. Edgar of the Du Pont de Nemours Company; Milton Whitney of the U.S. Bureau of Soils; Dr. H.N. McCoy; K.F. Kellerman of the Bureau of Plant Industry.

E.E.S.



LIST OF ILLUSTRATIONS

The production of new and stronger forms of steel is one of the greatest triumphs of modern chemistry Frontispiece

FACING PAGE

The hand grenades contain potential chemical energy capable of causing a vast amount of destruction when released 16

Women in a munition plant engaged in the manufacture of tri-nitro-toluol 17

A chemical reaction on a large scale 32

Burning air in a Birkeland-Eyde furnace at the DuPont plant 33

A battery of Birkeland-Eyde furnaces for the fixation of nitrogen at the DuPont plant 33

Fixing nitrogen by calcium carbide 40

A barrow full of potash salts extracted from six tons of green kelp by the government chemists 41

Nature's silent method of nitrogen fixation 41

In order to secure a new supply of potash salts the United States Government set up an experimental plant at Sutherland, California, for utilization of kelp 52

Overhead suction at the San Diego wharf pumping kelp from the barge to the digestion tanks 53

The kelp harvester gathering the seaweed from the Pacific Ocean 53

A battery of Koppers by-product coke-ovens at the plant of the Bethlehem Steel Company, Sparrows Point, Maryland 60

In these mixing vats at the Buffalo Works, aniline dyes are prepared 61

A paper mill in action 120

Cellulose from wood pulp is now made into a large variety of useful articles of which a few examples are here pictured 121

Plantation rubber 160

Forest rubber 160

In making garden hose the rubber is formed into a tube by the machine on the right and coiled on the table to the left 161

The rival sugars 176

Interior of a sugar mill showing the machinery for crushing cane to extract the juice 177

Vacuum pans of the American Sugar Refinery Company 177

Cotton seed oil as it is squeezed from the seed by the presses 200

Cotton seed oil as it comes from the compressors flowing out of the faucets 201

Splitting coconuts on the island of Tahiti 216

The electric current passing through salt water in these cells decomposes the salt into caustic soda and chlorine gas 217

Germans starting a gas attack on the Russian lines 224

Filling the cannisters of gas masks with charcoal made from fruit pits—Long Island City 225

The chlorpicrin plant at the Bdgewood Arsenal 234

Repairing the broken stern post of the U.S.S. Northern Pacific, the biggest marine weld in the world 235

Making aloxite in the electric furnaces by fusing coke and bauxite 240

A block of carborundum crystals 241

Making carborundum in the electric furnace 241

Types of gas mask used by America, the Allies and Germany during the war 256

Pumping melted white phosphorus into hand grenades filled with water—Edgewood Arsenal 257

Filling shell with "mustard gas" 257

Photomicrographs showing the structure of steel made by Professor E.G. Mahin of Purdue University 272

The microscopic structure of metals 273



INTRODUCTION

BY JULIUS STIEGLITZ

Formerly President of the American Chemical Society, Professor of Chemistry in The University of Chicago

The recent war as never before in the history of the world brought to the nations of the earth a realization of the vital place which the science of chemistry holds in the development of the resources of a nation. Some of the most picturesque features of this awakening reached the great public through the press. Thus, the adventurous trips of the Deutschland with its cargoes of concentrated aniline dyes, valued at millions of dollars, emphasized as no other incident our former dependence upon Germany for these products of her chemical industries.

The public read, too, that her chemists saved Germany from an early disastrous defeat, both in the field of military operations and in the matter of economic supplies: unquestionably, without the tremendous expansion of her plants for the production of nitrates and ammonia from the air by the processes of Haber, Ostwald and others of her great chemists, the war would have ended in 1915, or early in 1916, from exhaustion of Germany's supplies of nitrate explosives, if not indeed from exhaustion of her food supplies as a consequence of the lack of nitrate and ammonia fertilizer for her fields. Inventions of substitutes for cotton, copper, rubber, wool and many other basic needs have been reported.

These feats of chemistry, performed under the stress of dire necessity, have, no doubt, excited the wonder and interest of our public. It is far more important at this time, however, when both for war and for peace needs, the resources of our country are strained to the utmost, that the public should awaken to a clear realization of what this science of chemistry really means for mankind, to the realization that its wizardry permeates the whole life of the nation as a vitalizing, protective and constructive agent very much in the same way as our blood, coursing through our veins and arteries, carries the constructive, defensive and life-bringing materials to every organ in the body.

If the layman will but understand that chemistry is the fundamental science of the transformation of matter, he will readily accept the validity of this sweeping assertion: he will realize, for instance, why exactly the same fundamental laws of the science apply to, and make possible scientific control of, such widely divergent national industries as agriculture and steel manufacturing. It governs the transformation of the salts, minerals and humus of our fields and the components of the air into corn, wheat, cotton and the innumerable other products of the soil; it governs no less the transformation of crude ores into steel and alloys, which, with the cunning born of chemical knowledge, may be given practically any conceivable quality of hardness, elasticity, toughness or strength. And exactly the same thing may be said of the hundreds of national activities that lie between the two extremes of agriculture and steel manufacture!

Moreover, the domain of the science of the transformation of matter includes even life itself as its loftiest phase: from our birth to our return to dust the laws of chemistry are the controlling laws of life, health, disease and death, and the ever clearer recognition of this relation is the strongest force that is raising medicine from the uncertain realm of an art to the safer sphere of an exact science. To many scientific minds it has even become evident that those most wonderful facts of life, heredity and character, must find their final explanation in the chemical composition of the components of life producing, germinal protoplasm: mere form and shape are no longer supreme but are relegated to their proper place as the housing only of the living matter which functions chemically.

It must be quite obvious now why thoughtful men are insisting that the public should be awakened to a broad realization of the significance of the science of chemistry for its national life.

It is a difficult science in its details, because it has found that it can best interpret the visible phenomena of the material world on the basis of the conception of invisible minute material atoms and molecules, each a world in itself, whose properties may be nevertheless accurately deduced by a rigorous logic controlling the highest type of scientific imagination. But a layman is interested in the wonders of great bridges and of monumental buildings without feeling the need of inquiring into the painfully minute and extended calculations of the engineer and architect of the strains and stresses to which every pin and every bar of the great bridge and every bit of stone, every foot of arch in a monumental edifice, will be exposed. So the public may understand and appreciate with the keenest interest the results of chemical effort without the need of instruction in the intricacies of our logic, of our dealings with our minute, invisible particles.

The whole nation's welfare demands, indeed, that our public be enlightened in the matter of the relation of chemistry to our national life. Thus, if our commerce and our industries are to survive the terrific competition that must follow the reestablishment of peace, our public must insist that its representatives in Congress preserve that independence in chemical manufacturing which the war has forced upon us in the matter of dyes, of numberless invaluable remedies to cure and relieve suffering; in the matter, too, of hundreds of chemicals, which our industries need for their successful existence.

Unless we are independent in these fields, how easily might an unscrupulous competing nation do us untold harm by the mere device, for instance, of delaying supplies, or by sending inferior materials to this country or by underselling our chemical manufacturers and, after the destruction of our chemical independence, handicapping our industries as they were in the first year or two of the great war! This is not a mere possibility created by the imagination, for our economic history contains instance after instance of the purposeful undermining and destruction of our industries in finer chemicals, dyes and drugs by foreign interests bent on preserving their monopoly. If one recalls that through control, for instance, of dyes by a competing nation, control is in fact also established over products, valued in the hundreds of millions of dollars, in which dyes enter as an essential factor, one may realize indeed the tremendous industrial and commercial power which is controlled by the single lever—chemical dyes. Of even more vital moment is chemistry in the domain of health: the pitiful calls of our hospitals for local anesthetics to alleviate suffering on the operating table, the frantic appeals for the hypnotic that soothes the epileptic and staves off his seizure, the almost furious demands for remedy after remedy, that came in the early years of the war, are still ringing in the hearts of many of us. No wonder that our small army of chemists is grimly determined not to give up the independence in chemistry which war has achieved for us! Only a widely enlightened public, however, can insure the permanence of what farseeing men have started to accomplish in developing the power of chemistry through research in every domain which chemistry touches.

The general public should realize that in the support of great chemical research laboratories of universities and technical schools it will be sustaining important centers from which the science which improves products, abolishes waste, establishes new industries and preserves life, may reach out helpfully into all the activities of our great nation, that are dependent on the transformation of matter.

The public is to be congratulated upon the fact that the writer of the present volume is better qualified than any other man in the country to bring home to his readers some of the great results of modern chemical activity as well as some of the big problems which must continue to engage the attention of our chemists. Dr. Slosson has indeed the unique quality of combining an exact and intimate knowledge of chemistry with the exquisite clarity and pointedness of expression of a born writer.

We have here an exposition by a master mind, an exposition shorn of the terrifying and obscuring technicalities of the lecture room, that will be as absorbing reading as any thrilling romance. For the story of scientific achievement is the greatest epic the world has ever known, and like the great national epics of bygone ages, should quicken the life of the nation by a realization of its powers and a picture of its possibilities.



CREATIVE CHEMISTRY

La Chimie possede cette faculte creatrice a un degre plus eminent que les autres sciences, parce qu'elle penetre plus profondement et atteint jusqu'aux elements naturels des etres.

—Berthelot.



I

THREE PERIODS OF PROGRESS

The story of Robinson Crusoe is an allegory of human history. Man is a castaway upon a desert planet, isolated from other inhabited worlds—if there be any such—by millions of miles of untraversable space. He is absolutely dependent upon his own exertions, for this world of his, as Wells says, has no imports except meteorites and no exports of any kind. Man has no wrecked ship from a former civilization to draw upon for tools and weapons, but must utilize as best he may such raw materials as he can find. In this conquest of nature by man there are three stages distinguishable:

1. The Appropriative Period 2. The Adaptive Period 3. The Creative Period

These eras overlap, and the human race, or rather its vanguard, civilized man, may be passing into the third stage in one field of human endeavor while still lingering in the second or first in some other respect. But in any particular line this sequence is followed. The primitive man picks up whatever he can find available for his use. His successor in the next stage of culture shapes and develops this crude instrument until it becomes more suitable for his purpose. But in the course of time man often finds that he can make something new which is better than anything in nature or naturally produced. The savage discovers. The barbarian improves. The civilized man invents. The first finds. The second fashions. The third fabricates.

The primitive man was a troglodyte. He sought shelter in any cave or crevice that he could find. Later he dug it out to make it more roomy and piled up stones at the entrance to keep out the wild beasts. This artificial barricade, this false facade, was gradually extended and solidified until finally man could build a cave for himself anywhere in the open field from stones he quarried out of the hill. But man was not content with such materials and now puts up a building which may be composed of steel, brick, terra cotta, glass, concrete and plaster, none of which materials are to be found in nature.

The untutored savage might cross a stream astride a floating tree trunk. By and by it occurred to him to sit inside the log instead of on it, so he hollowed it out with fire or flint. Later, much later, he constructed an ocean liner.

Cain, or whoever it was first slew his brother man, made use of a stone or stick. Afterward it was found a better weapon could be made by tying the stone to the end of the stick, and as murder developed into a fine art the stick was converted into the bow and this into the catapult and finally into the cannon, while the stone was developed into the high explosive projectile. The first music to soothe the savage breast was the soughing of the wind through the trees. Then strings were stretched across a crevice for the wind to play upon and there was the AEolian harp. The second stage was entered when Hermes strung the tortoise shell and plucked it with his fingers and when Athena, raising the wind from her own lungs, forced it through a hollow reed. From these beginnings we have the organ and the orchestra, producing such sounds as nothing in nature can equal.

The first idol was doubtless a meteorite fallen from heaven or a fulgurite or concretion picked up from the sand, bearing some slight resemblance to a human being. Later man made gods in his own image, and so sculpture and painting grew until now the creations of futuristic art could be worshiped—if one wanted to—without violation of the second commandment, for they are not the likeness of anything that is in heaven above or that is in the earth beneath or that is in the water under the earth.

In the textile industry the same development is observable. The primitive man used the skins of animals he had slain to protect his own skin. In the course of time he—or more probably his wife, for it is to the women rather than to the men that we owe the early steps in the arts and sciences—fastened leaves together or pounded out bark to make garments. Later fibers were plucked from the sheepskin, the cocoon and the cotton-ball, twisted together and woven into cloth. Nowadays it is possible to make a complete suit of clothes, from hat to shoes, of any desirable texture, form and color, and not include any substance to be found in nature. The first metals available were those found free in nature such as gold and copper. In a later age it was found possible to extract iron from its ores and today we have artificial alloys made of multifarious combinations of rare metals. The medicine man dosed his patients with decoctions of such roots and herbs as had a bad taste or queer look. The pharmacist discovered how to extract from these their medicinal principle such as morphine, quinine and cocaine, and the creative chemist has discovered how to make innumerable drugs adapted to specific diseases and individual idiosyncrasies.

In the later or creative stages we enter the domain of chemistry, for it is the chemist alone who possesses the power of reducing a substance to its constituent atoms and from them producing substances entirely new. But the chemist has been slow to realize his unique power and the world has been still slower to utilize his invaluable services. Until recently indeed the leaders of chemical science expressly disclaimed what should have been their proudest boast. The French chemist Lavoisier in 1793 defined chemistry as "the science of analysis." The German chemist Gerhardt in 1844 said: "I have demonstrated that the chemist works in opposition to living nature, that he burns, destroys, analyzes, that the vital force alone operates by synthesis, that it reconstructs the edifice torn down by the chemical forces."

It is quite true that chemists up to the middle of the last century were so absorbed in the destructive side of their science that they were blind to the constructive side of it. In this respect they were less prescient than their contemned predecessors, the alchemists, who, foolish and pretentious as they were, aspired at least to the formation of something new.

It was, I think, the French chemist Berthelot who first clearly perceived the double aspect of chemistry, for he defined it as "the science of analysis and synthesis," of taking apart and of putting together. The motto of chemistry, as of all the empirical sciences, is savoir c'est pouvoir, to know in order to do. This is the pragmatic test of all useful knowledge. Berthelot goes on to say:

Chemistry creates its object. This creative faculty, comparable to that of art itself, distinguishes it essentially from the natural and historical sciences.... These sciences do not control their object. Thus they are too often condemned to an eternal impotence in the search for truth of which they must content themselves with possessing some few and often uncertain fragments. On the contrary, the experimental sciences have the power to realize their conjectures.... What they dream of that they can manifest in actuality....

Chemistry possesses this creative faculty to a more eminent degree than the other sciences because it penetrates more profoundly and attains even to the natural elements of existences.

Since Berthelot's time, that is, within the last fifty years, chemistry has won its chief triumphs in the field of synthesis. Organic chemistry, that is, the chemistry of the carbon compounds, so called because it was formerly assumed, as Gerhardt says, that they could only be formed by "vital force" of organized plants and animals, has taken a development far overshadowing inorganic chemistry, or the chemistry of mineral substances. Chemists have prepared or know how to prepare hundreds of thousands of such "organic compounds," few of which occur in the natural world.

But this conception of chemistry is yet far from having been accepted by the world at large. This was brought forcibly to my attention during the publication of these chapters in "The Independent" by various letters, raising such objections as the following:

When you say in your article on "What Comes from Coal Tar" that "Art can go ahead of nature in the dyestuff business" you have doubtless for the moment allowed your enthusiasm to sweep you away from the moorings of reason. Shakespeare, anticipating you and your "Creative Chemistry," has shown the utter untenableness of your position:

Nature is made better by no mean, But nature makes that mean: so o'er that art, Which, you say, adds to nature, is an art That nature makes.

How can you say that art surpasses nature when you know very well that nothing man is able to make can in any way equal the perfection of all nature's products?

It is blasphemous of you to claim that man can improve the works of God as they appear in nature. Only the Creator can create. Man only imitates, destroys or defiles God's handiwork.

No, it was not in momentary absence of mind that I claimed that man could improve upon nature in the making of dyes. I not only said it, but I proved it. I not only proved it, but I can back it up. I will give a million dollars to anybody finding in nature dyestuffs as numerous, varied, brilliant, pure and cheap as those that are manufactured in the laboratory. I haven't that amount of money with me at the moment, but the dyers would be glad to put it up for the discovery of a satisfactory natural source for their tinctorial materials. This is not an opinion of mine but a matter of fact, not to be decided by Shakespeare, who was not acquainted with the aniline products.

Shakespeare in the passage quoted is indulging in his favorite amusement of a play upon words. There is a possible and a proper sense of the word "nature" that makes it include everything except the supernatural. Therefore man and all his works belong to the realm of nature. A tenement house in this sense is as "natural" as a bird's nest, a peapod or a crystal.

But such a wide extension of the term destroys its distinctive value. It is more convenient and quite as correct to use "nature" as I have used it, in contradistinction to "art," meaning by the former the products of the mineral, vegetable and animal kingdoms, excluding the designs, inventions and constructions of man which we call "art."

We cannot, in a general and abstract fashion, say which is superior, art or nature, because it all depends on the point of view. The worm loves a rotten log into which he can bore. Man prefers a steel cabinet into which the worm cannot bore. If man cannot improve Upon nature he has no motive for making anything. Artificial products are therefore superior to natural products as measured by man's convenience, otherwise they would have no reason for existence.

Science and Christianity are at one in abhorring the natural man and calling upon the civilized man to fight and subdue him. The conquest of nature, not the imitation of nature, is the whole duty of man. Metchnikoff and St. Paul unite in criticizing the body we were born with. St. Augustine and Huxley are in agreement as to the eternal conflict between man and nature. In his Romanes lecture on "Evolution and Ethics" Huxley said: "The ethical progress of society depends, not on imitating the cosmic process, still less on running away from it, but on combating it," and again: "The history of civilization details the steps by which man has succeeded in building up an artificial world within the cosmos."

There speaks the true evolutionist, whose one desire is to get away from nature as fast and far as possible. Imitate Nature? Yes, when we cannot improve upon her. Admire Nature? Possibly, but be not blinded to her defects. Learn from Nature? We should sit humbly at her feet until we can stand erect and go our own way. Love Nature? Never! She is our treacherous and unsleeping foe, ever to be feared and watched and circumvented, for at any moment and in spite of all our vigilance she may wipe out the human race by famine, pestilence or earthquake and within a few centuries obliterate every trace of its achievement. The wild beasts that man has kept at bay for a few centuries will in the end invade his palaces: the moss will envelop his walls and the lichen disrupt them. The clam may survive man by as many millennia as it preceded him. In the ultimate devolution of the world animal life will disappear before vegetable, the higher plants will be killed off before the lower, and finally the three kingdoms of nature will be reduced to one, the mineral. Civilized man, enthroned in his citadel and defended by all the forces of nature that he has brought under his control, is after all in the same situation as a savage, shivering in the darkness beside his fire, listening to the pad of predatory feet, the rustle of serpents and the cry of birds of prey, knowing that only the fire keeps his enemies off, but knowing too that every stick he lays on the fire lessens his fuel supply and hastens the inevitable time when the beasts of the jungle will make their fatal rush.

Chaos is the "natural" state of the universe. Cosmos is the rare and temporary exception. Of all the million spheres this is apparently the only one habitable and of this only a small part—the reader may draw the boundaries to suit himself—can be called civilized. Anarchy is the natural state of the human race. It prevailed exclusively all over the world up to some five thousand years ago, since which a few peoples have for a time succeeded in establishing a certain degree of peace and order. This, however, can be maintained only by strenuous and persistent efforts, for society tends naturally to sink into the chaos out of which it has arisen.

It is only by overcoming nature that man can rise. The sole salvation for the human race lies in the removal of the primal curse, the sentence of hard labor for life that was imposed on man as he left Paradise. Some folks are trying to elevate the laboring classes; some are trying to keep them down. The scientist has a more radical remedy; he wants to annihilate the laboring classes by abolishing labor. There is no longer any need for human labor in the sense of personal toil, for the physical energy necessary to accomplish all kinds of work may be obtained from external sources and it can be directed and controlled without extreme exertion. Man's first effort in this direction was to throw part of his burden upon the horse and ox or upon other men. But within the last century it has been discovered that neither human nor animal servitude is necessary to give man leisure for the higher life, for by means of the machine he can do the work of giants without exhaustion. But the introduction of machines, like every other step of human progress, met with the most violent opposition from those it was to benefit. "Smash 'em!" cried the workingman. "Smash 'em!" cried the poet. "Smash 'em!" cried the artist. "Smash 'em!" cried the theologian. "Smash 'em!" cried the magistrate. This opposition yet lingers and every new invention, especially in chemistry, is greeted with general distrust and often with legislative prohibition.

Man is the tool-using animal, and the machine, that is, the power-driven tool, is his peculiar achievement. It is purely a creation of the human mind. The wheel, its essential feature, does not exist in nature. The lever, with its to-and-fro motion, we find in the limbs of all animals, but the continuous and revolving lever, the wheel, cannot be formed of bone and flesh. Man as a motive power is a poor thing. He can only convert three or four thousand calories of energy a day and he does that very inefficiently. But he can make an engine that will handle a hundred thousand times that, twice as efficiently and three times as long. In this way only can he get rid of pain and toil and gain the wealth he wants.

Gradually then he will substitute for the natural world an artificial world, molded nearer to his heart's desire. Man the Artifex will ultimately master Nature and reign supreme over his own creation until chaos shall come again. In the ancient drama it was deus ex machina that came in at the end to solve the problems of the play. It is to the same supernatural agency, the divinity in machinery, that we must look for the salvation of society. It is by means of applied science that the earth can be made habitable and a decent human life made possible. Creative evolution is at last becoming conscious.



II

NITROGEN

PRESERVER AND DESTROYER OF LIFE

In the eyes of the chemist the Great War was essentially a series of explosive reactions resulting in the liberation of nitrogen. Nothing like it has been seen in any previous wars. The first battles were fought with cellulose, mostly in the form of clubs. The next were fought with silica, mostly in the form of flint arrowheads and spear-points. Then came the metals, bronze to begin with and later iron. The nitrogenous era in warfare began when Friar Roger Bacon or Friar Schwartz—whichever it was—ground together in his mortar saltpeter, charcoal and sulfur. The Chinese, to be sure, had invented gunpowder long before, but they—poor innocents—did not know of anything worse to do with it than to make it into fire-crackers. With the introduction of "villainous saltpeter" war ceased to be the vocation of the nobleman and since the nobleman had no other vocation he began to become extinct. A bullet fired from a mile away is no respecter of persons. It is just as likely to kill a knight as a peasant, and a brave man as a coward. You cannot fence with a cannon ball nor overawe it with a plumed hat. The only thing you can do is to hide and shoot back. Now you cannot hide if you send up a column of smoke by day and a pillar of fire by night—the most conspicuous of signals—every time you shoot. So the next step was the invention of a smokeless powder. In this the oxygen necessary for the combustion is already in such close combination with its fuel, the carbon and hydrogen, that no black particles of carbon can get away unburnt. In the old-fashioned gunpowder the oxygen necessary for the combustion of the carbon and sulfur was in a separate package, in the molecule of potassium nitrate, and however finely the mixture was ground, some of the atoms, in the excitement of the explosion, failed to find their proper partners at the moment of dispersal. The new gunpowder besides being smokeless is ashless. There is no black sticky mass of potassium salts left to foul the gun barrel.

The gunpowder period of warfare was actively initiated at the battle of Cressy, in which, as a contemporary historian says, "The English guns made noise like thunder and caused much loss in men and horses." Smokeless powder as invented by Paul Vieille was adopted by the French Government in 1887. This, then, might be called the beginning of the guncotton or nitrocellulose period—or, perhaps in deference to the caveman's club, the second cellulose period of human warfare. Better, doubtless, to call it the "high explosive period," for various other nitro-compounds besides guncotton are being used.

The important thing to note is that all the explosives from gunpowder down contain nitrogen as the essential element. It is customary to call nitrogen "an inert element" because it was hard to get it into combination with other elements. It might, on the other hand, be looked upon as an active element because it acts so energetically in getting out of its compounds. We can dodge the question by saying that nitrogen is a most unreliable and unsociable element. Like Kipling's cat it walks by its wild lone.

It is not so bad as Argon the Lazy and the other celibate gases of that family, where each individual atom goes off by itself and absolutely refuses to unite even temporarily with any other atom. The nitrogen atoms will pair off with each other and stick together, but they are reluctant to associate with other elements and when they do the combination is likely to break up any moment. You all know people like that, good enough when by themselves but sure to break up any club, church or society they get into. Now, the value of nitrogen in warfare is due to the fact that all the atoms desert in a body on the field of battle. Millions of them may be lying packed in a gun cartridge, as quiet as you please, but let a little disturbance start in the neighborhood—say a grain of mercury fulminate flares up—and all the nitrogen atoms get to trembling so violently that they cannot be restrained. The shock spreads rapidly through the whole mass. The hydrogen and carbon atoms catch up the oxygen and in an instant they are off on a stampede, crowding in every direction to find an exit, and getting more heated up all the time. The only movable side is the cannon ball in front, so they all pound against that and give it such a shove that it goes ten miles before it stops. The external bombardment by the cannon ball is, therefore, preceded by an internal bombardment on the cannon ball by the molecules of the hot gases, whose speed is about as great as the speed of the projectile that they propel.



The active agent in all these explosives is the nitrogen atom in combination with two oxygen atoms, which the chemist calls the "nitro group" and which he represents by NO_{2}. This group was, as I have said, originally used in the form of saltpeter or potassium nitrate, but since the chemist did not want the potassium part of it—for it fouled his guns—he took the nitro group out of the nitrate by means of sulfuric acid and by the same means hooked it on to some compound of carbon and hydrogen that would burn without leaving any residue, and give nothing but gases. One of the simplest of these hydrocarbon derivatives is glycerin, the same as you use for sunburn. This mixed with nitric and sulfuric acids gives nitroglycerin, an easy thing to make, though I should not advise anybody to try making it unless he has his life insured. But nitroglycerin is uncertain stuff to keep and being a liquid is awkward to handle. So it was mixed with sawdust or porous earth or something else that would soak it up. This molded into sticks is our ordinary dynamite.

If instead of glycerin we take cellulose in the form of wood pulp or cotton and treat this with nitric acid in the presence of sulfuric we get nitrocellulose or guncotton, which is the chief ingredient of smokeless powder.

Now guncotton looks like common cotton. It is too light and loose to pack well into a gun. So it is dissolved with ether and alcohol or acetone to make a plastic mass that can be molded into rods and cut into grains of suitable shape and size to burn at the proper speed.

Here, then, we have a liquid explosive, nitroglycerin, that has to be soaked up in some porous solid, and a porous solid, guncotton, that has to soak up some liquid. Why not solve both difficulties together by dissolving the guncotton in the nitroglycerin and so get a double explosive? This is a simple idea. Any of us can see the sense of it—once it is suggested to us. But Alfred Nobel, the Swedish chemist, who thought it out first in 1878, made millions out of it. Then, apparently alarmed at the possible consequences of his invention, he bequeathed the fortune he had made by it to found international prizes for medical, chemical and physical discoveries, idealistic literature and the promotion of peace. But his posthumous efforts for the advancement of civilization and the abolition of war did not amount to much and his high explosives were later employed to blow into pieces the doctors, chemists, authors and pacifists he wished to reward.

Nobel's invention, "cordite," is composed of nitroglycerin and nitrocellulose with a little mineral jelly or vaseline. Besides cordite and similar mixtures of nitroglycerin and nitrocellulose there are two other classes of high explosives in common use.

One is made from carbolic acid, which is familiar to us all by its use as a disinfectant. If this is treated with nitric and sulfuric acids we get from it picric acid, a yellow crystalline solid. Every government has its own secret formula for this type of explosive. The British call theirs "lyddite," the French "melinite" and the Japanese "shimose."

The third kind of high explosives uses as its base toluol. This is not so familiar to us as glycerin, cotton or carbolic acid. It is one of the coal tar products, an inflammable liquid, resembling benzene. When treated with nitric acid in the usual way it takes up like the others three nitro groups and so becomes tri-nitro-toluol. Realizing that people could not be expected to use such a mouthful of a word, the chemists have suggested various pretty nicknames, trotyl, tritol, trinol, tolite and trilit, but the public, with the wilfulness it always shows in the matter of names, persists in calling it TNT, as though it were an author like G.B.S., or G.K.C, or F.P.A. TNT is the latest of these high explosives and in some ways the best of them. Picric acid has the bad habit of attacking the metals with which it rests in contact forming sensitive picrates that are easily set off, but TNT is inert toward metals and keeps well. TNT melts far below the boiling point of water so can be readily liquefied and poured into shells. It is insensitive to ordinary shocks. A rifle bullet can be fired through a case of it without setting it off, and if lighted with a match it burns quietly. The amazing thing about these modern explosives, the organic nitrates, is the way they will stand banging about and burning, yet the terrific violence with which they blow up when shaken by an explosive wave of a particular velocity like that of a fulminating cap. Like picric acid, TNT stains the skin yellow and causes soreness and sometimes serious cases of poisoning among the employees, mostly girls, in the munition factories. On the other hand, the girls working with cordite get to using it as chewing gum; a harmful habit, not because of any danger of being blown up by it, but because nitroglycerin is a heart stimulant and they do not need that.



TNT is by no means smokeless. The German shells that exploded with a cloud of black smoke and which British soldiers called "Black Marias," "coal-boxes" or "Jack Johnsons" were loaded with it. But it is an advantage to have a shell show where it strikes, although a disadvantage to have it show where it starts.

It is these high explosives that have revolutionized warfare. As soon as the first German shell packed with these new nitrates burst inside the Gruson cupola at Liege and tore out its steel and concrete by the roots the world knew that the day of the fixed fortress was gone. The armies deserted their expensively prepared fortifications and took to the trenches. The British troops in France found their weapons futile and sent across the Channel the cry of "Send us high explosives or we perish!" The home Government was slow to heed the appeal, but no progress was made against the Germans until the Allies had the means to blast them out of their entrenchments by shells loaded with five hundred pounds of TNT.

All these explosives are made from nitric acid and this used to be made from nitrates such as potassium nitrate or saltpeter. But nitrates are rarely found in large quantities. Napoleon and Lee had a hard time to scrape up enough saltpeter from the compost heaps, cellars and caves for their gunpowder, and they did not use as much nitrogen in a whole campaign as was freed in a few days' cannonading on the Somme. Now there is one place in the world—and so far as we know one only—where nitrates are to be found abundantly. This is in a desert on the western slope of the Andes where ancient guano deposits have decomposed and there was not enough rain to wash away their salts. Here is a bed two miles wide, two hundred miles long and five feet deep yielding some twenty to fifty per cent. of sodium nitrate. The deposit originally belonged to Peru, but Chile fought her for it and got it in 1881. Here all countries came to get their nitrates for agriculture and powder making. Germany was the largest customer and imported 750,000 tons of Chilean nitrate in 1913, besides using 100,000 tons of other nitrogen salts. By this means her old, wornout fields were made to yield greater harvests than our fresh land. Germany and England were like two duelists buying powder at the same shop. The Chilean Government, pocketing an export duty that aggregated half a billion dollars, permitted the saltpeter to be shoveled impartially into British and German ships, and so two nitrogen atoms, torn from their Pacific home and parted, like Evangeline and Gabriel, by transportation oversea, may have found themselves flung into each other's arms from the mouths of opposing howitzers in the air of Flanders. Goethe could write a romance on such a theme.

Now the moment war broke out this source of supply was shut off to both parties, for they blockaded each other. The British fleet closed up the German ports while the German cruisers in the Pacific took up a position off the coast of Chile in order to intercept the ships carrying nitrates to England and France. The Panama Canal, designed to afford relief in such an emergency, caved in most inopportunely. The British sent a fleet to the Pacific to clear the nitrate route, but it was outranged and defeated on November 1, 1914. Then a stronger British fleet was sent out and smashed the Germans off the Falkland Islands on December 8. But for seven weeks the nitrate route had been closed while the chemical reactions on the Marne and Yser were decomposing nitrogen-compounds at an unheard of rate.

England was now free to get nitrates for her munition factories, but Germany was still bottled up. She had stored up Chilean nitrates in anticipation of the war and as soon as it was seen to be coming she bought all she could get in Europe. But this supply was altogether inadequate and the war would have come to an end in the first winter if German chemists had not provided for such a contingency in advance by working out methods of getting nitrogen from the air. Long ago it was said that the British ruled the sea and the French the land so that left nothing to the German but the air. The Germans seem to have taken this jibe seriously and to have set themselves to make the most of the aerial realm in order to challenge the British and French in the fields they had appropriated. They had succeeded so far that the Kaiser when he declared war might well have considered himself the Prince of the Power of the Air. He had a fleet of Zeppelins and he had means for the fixation of nitrogen such as no other nation possessed. The Zeppelins burst like wind bags, but the nitrogen plants worked and made Germany independent of Chile not only during the war, but in the time of peace.

Germany during the war used 200,000 tons of nitric acid a year in explosives, yet her supply of nitrogen is exhaustless.



Nitrogen is free as air. That is the trouble; it is too free. It is fixed nitrogen that we want and that we are willing to pay for; nitrogen in combination with some other elements in the form of food or fertilizer so we can make use of it as we set it free. Fixed nitrogen in its cheapest form, Chile saltpeter, rose to $250 during the war. Free nitrogen costs nothing and is good for nothing. If a land-owner has a right to an expanding pyramid of air above him to the limits of the atmosphere—as, I believe, the courts have decided in the eaves-dropping cases—then for every square foot of his ground he owns as much nitrogen as he could buy for $2500. The air is four-fifths free nitrogen and if we could absorb it in our lungs as we do the oxygen of the other fifth a few minutes breathing would give us a full meal. But we let this free nitrogen all out again through our noses and then go and pay 35 cents a pound for steak or 60 cents a dozen for eggs in order to get enough combined nitrogen to live on. Though man is immersed in an ocean of nitrogen, yet he cannot make use of it. He is like Coleridge's "Ancient Mariner" with "water, water, everywhere, nor any drop to drink."

Nitrogen is, as Hood said not so truly about gold, "hard to get and hard to hold." The bacteria that form the nodules on the roots of peas and beans have the power that man has not of utilizing free nitrogen. Instead of this quiet inconspicuous process man has to call upon the lightning when he wants to fix nitrogen. The air contains the oxygen and nitrogen which it is desired to combine to form nitrates but the atoms are paired, like to like. Passing an electric spark through the air breaks up some of these pairs and in the confusion of the shock the lonely atoms seize on their nearest neighbor and so may get partners of the other sort. I have seen this same thing happen in a square dance where somebody made a blunder. It is easy to understand the reaction if we represent the atoms of oxygen and nitrogen by the initials of their names in this fashion:

NN + OO —> NO + NO nitrogen oxygen nitric oxide

The —> represents Jove's thunderbolt, a stroke of artificial lightning. We see on the left the molecules of oxygen and nitrogen, before taking the electric treatment, as separate elemental pairs, and then to the right of the arrow we find them as compound molecules of nitric oxide. This takes up another atom of oxygen from the air and becomes NOO, or using a subscript figure to indicate the number of atoms and so avoid repeating the letter, NO_{2} which is the familiar nitro group of nitric acid (HO—NO_{2}) and of its salts, the nitrates, and of its organic compounds, the high explosives. The NO_{2} is a brown and evil-smelling gas which when dissolved in water (HOH) and further oxidized is completely converted into nitric acid.

The apparatus which effects this transformation is essentially a gigantic arc light in a chimney through which a current of hot air is blown. The more thoroughly the air comes under the action of the electric arc the more molecules of nitrogen and oxygen will be broken up and rearranged, but on the other hand if the mixture of gases remains in the path of the discharge the NO molecules are also broken up and go back into their original form of NN and OO. So the object is to spread out the electric arc as widely as possible and then run the air through it rapidly. In the Schoenherr process the electric arc is a spiral flame twenty-three feet long through which the air streams with a vortex motion. In the Birkeland-Eyde furnace there is a series of semi-circular arcs spread out by the repellent force of a powerful electric magnet in a flaming disc seven feet in diameter with a temperature of 6300 deg. F. In the Pauling furnace the electrodes between which the current strikes are two cast iron tubes curving upward and outward like the horns of a Texas steer and cooled by a stream of water passing through them. These electric furnaces produce two or three ounces of nitric acid for each kilowatt-hour of current consumed. Whether they can compete with the natural nitrates and the products of other processes depends upon how cheaply they can get their electricity. Before the war there were several large installations in Norway and elsewhere where abundant water power was available and now the Norwegians are using half a million horse power continuously in the fixation of nitrogen and the rest of the world as much again. The Germans had invested largely in these foreign oxidation plants, but shortly before the war they had sold out and turned their attention to other processes not requiring so much electrical energy, for their country is poorly provided with water power. The Haber process, that they made most of, is based upon as simple a reaction as that we have been considering, for it consists in uniting two elemental gases to make a compound, but the elements in this case are not nitrogen and oxygen, but nitrogen and hydrogen. This gives ammonia instead of nitric acid, but ammonia is useful for its own purposes and it can be converted into nitric acid if this is desired. The reaction is:

NN + HH + HH + HH —> NHHH + NHHH Nitrogen hydrogen ammonia

The animals go in two by two, but they come out four by four. Four molecules of the mixed elements are turned into two molecules and so the gas shrinks to half its volume. At the same time it acquires an odor—familiar to us when we are curing a cold—that neither of the original gases had. The agent that effects the transformation in this case is not the electric spark—for this would tend to work the reaction backwards—but uranium, a rare metal, which has the peculiar property of helping along a reaction while seeming to take no part in it. Such a substance is called a catalyst. The action of a catalyst is rather mysterious and whenever we have a mystery we need an analogy. We may, then, compare the catalyst to what is known as "a good mixer" in society. You know the sort of man I mean. He may not be brilliant or especially talkative, but somehow there is always "something doing" at a picnic or house-party when he is along. The tactful hostess, the salon leader, is a social catalyst. The trouble with catalysts, either human or metallic, is that they are rare and that sometimes they get sulky and won't work if the ingredients they are supposed to mix are unsuitable.

But the uranium, osmium, platinum or whatever metal is used as a catalyzing agent is expensive and although it is not used up it is easily "poisoned," as the chemists say, by impurities in the gases. The nitrogen and the hydrogen for the Haber process must then be prepared and purified before trying to combine them into ammonia. The nitrogen is obtained by liquefying air by cold and pressure and then boiling off the nitrogen at 194 deg. C. The oxygen left is useful for other purposes. The hydrogen needed is extracted by a similar process of fractional distillation from "water-gas," the blue-flame burning gas used for heating. Then the nitrogen and hydrogen, mixed in the proportion of one to three, as shown in the reaction given above, are compressed to two hundred atmospheres, heated to 1300 deg. F. and passed over the finely divided uranium. The stream of gas that comes out contains about four per cent. of ammonia, which is condensed to a liquid by cooling and the uncombined hydrogen and nitrogen passed again through the apparatus.

The ammonia can be employed in refrigeration and other ways but if it is desired to get the nitrogen into the form of nitric acid it has to be oxidized by the so-called Ostwald process. This is the reaction:

NH_{3} + 4O —> HNO_{3} + H_{2}O ammonia oxygen nitric acid water

The catalyst used to effect this combination is the metal platinum in the form of fine wire gauze, since the action takes place only on the surface. The ammonia gas is mixed with air which supplies the oxygen and the heated mixture run through the platinum gauze at the rate of several yards a second. Although the gases come in contact with the platinum only a five-hundredth part of a second yet eighty-five per cent. is converted into nitric acid.

The Haber process for the making of ammonia by direct synthesis from its constituent elements and the supplemental Ostwald process for the conversion of the ammonia into nitric acid were the salvation of Germany. As soon as the Germans saw that their dash toward Paris had been stopped at the Marne they knew that they were in for a long war and at once made plans for a supply of fixed nitrogen. The chief German dye factories, the Badische Anilin and Soda-Fabrik, promptly put $100,000,000 into enlarging its plant and raised its production of ammonium sulfate from 30,000 to 300,000 tons. One German electrical firm with aid from the city of Berlin contracted to provide 66,000,000 pounds of fixed nitrogen a year at a cost of three cents a pound for the next twenty-five years. The 750,000 tons of Chilean nitrate imported annually by Germany contained about 116,000 tons of the essential element nitrogen. The fourteen large plants erected during the war can fix in the form of nitrates 500,000 tons of nitrogen a year, which is more than twice the amount needed for internal consumption. So Germany is now not only independent of the outside world but will have a surplus of nitrogen products which could be sold even in America at about half what the farmer has been paying for South American saltpeter.

Besides the Haber or direct process there are other methods of making ammonia which are, at least outside of Germany, of more importance. Most prominent of these is the cyanamid process. This requires electrical power since it starts with a product of the electrical furnace, calcium carbide, familiar to us all as a source of acetylene gas.

If a stream of nitrogen is passed over hot calcium carbide it is taken up by the carbide according to the following equation:

CaC_{2} + N_{2} —> CaCN_{2} + C calcium carbide nitrogen calcium cyanamid carbon

Calcium cyanamid was discovered in 1895 by Caro and Franke when they were trying to work out a new process for making cyanide to use in extracting gold. It looks like stone and, under the name of lime-nitrogen, or Kalkstickstoff, or nitrolim, is sold as a fertilizer. If it is desired to get ammonia, it is treated with superheated steam. The reaction produces heat and pressure, so it is necessary to carry it on in stout autoclaves or enclosed kettles. The cyanamid is completely and quickly converted into pure ammonia and calcium carbonate, which is the same as the limestone from which carbide was made. The reaction is:

CaCN{2} + 3H{2}O —> CaCO{3} + 2NH{3} calcium cyanamid water calcium carbonate ammonia

Another electrical furnace method, the Serpek process, uses aluminum instead of calcium for the fixation of nitrogen. Bauxite, or impure aluminum oxide, the ordinary mineral used in the manufacture of metallic aluminum, is mixed with coal and heated in a revolving electrical furnace through which nitrogen is passing. The equation is:

Al_{2}O_{3} + 3C + N_{2} —> 2AlN + 3CO aluminum carbon nitrogen aluminum carbon oxide nitride monoxide

Then the aluminum nitride is treated with steam under pressure, which produces ammonia and gives back the original aluminum oxide, but in a purer form than the mineral from which was made

2AlN + 3H{2}O —> 2NH{3} + Al{2}O{3} Aluminum water ammonia aluminum oxide nitride

The Serpek process is employed to some extent in France in connection with the aluminum industry. These are the principal processes for the fixation of nitrogen now in use, but they by no means exhaust the possibilities. For instance, Professor John C. Bucher, of Brown University, created a sensation in 1917 by announcing a new process which he had worked out with admirable completeness and which has some very attractive features. It needs no electric power or high pressure retorts or liquid air apparatus. He simply fills a twenty-foot tube with briquets made out of soda ash, iron and coke and passes producer gas through the heated tube. Producer gas contains nitrogen since it is made by passing air over hot coal. The reaction is:

2Na_{2}CO_{3} + 4C + N_{2} = 2NaCN + 3CO sodium carbon nitrogen sodium carbon carbonate cyanide monoxide

The iron here acts as the catalyst and converts two harmless substances, sodium carbonate, which is common washing soda, and carbon, into two of the most deadly compounds known to man, cyanide and carbon monoxide, which is what kills you when you blow out the gas. Sodium cyanide is a salt of hydrocyanic acid, which for, some curious reason is called "Prussic acid." It is so violent a poison that, as the freshman said in a chemistry recitation, "a single drop of it placed on the tongue of a dog will kill a man."

But sodium cyanide is not only useful in itself, for the extraction of gold and cleaning of silver, but can be converted into ammonia, and a variety of other compounds such as urea and oxamid, which are good fertilizers; sodium ferrocyanide, that makes Prussian blue; and oxalic acid used in dyeing. Professor Bucher claimed that his furnace could be set up in a day at a cost of less than $100 and could turn out 150 pounds of sodium cyanide in twenty-four hours. This process was placed freely at the disposal of the United States Government for the war and a 10-ton plant was built at Saltville, Va., by the Ordnance Department. But the armistice put a stop to its operations and left the future of the process undetermined.



[Illustration: Courtesy of E.I. du Pont de Nemours Co.

BURNING AIR IN A BIRKELAND-EYDE FURNACE AT THE DU PONT PLANT

An electric arc consuming about 4000 horse-power of energy is passing between the U-shaped electrodes which are made of copper tube cooled by an internal current of water. On the sides of the chamber are seen the openings through which the air passes impinging directly on both sides of the surface of the disk of flame. This flame is approximately seven feet in diameter and appears to be continuous although an alternating current of fifty cycles a second is used. The electric arc is spread into this disk flame by the repellent power of an electro-magnet the pointed pole of which is seen at bottom of the picture. Under this intense heat a part of the nitrogen and oxygen of the air combine to form oxides of nitrogen which when dissolved in water form the nitric acid used in explosives.]



We might have expected that the fixation of nitrogen by passing an electrical spark through hot air would have been an American invention, since it was Franklin who snatched the lightning from the heavens as well as the scepter from the tyrant and since our output of hot air is unequaled by any other nation. But little attention was paid to the nitrogen problem until 1916 when it became evident that we should soon be drawn into a war "with a first class power." On June 3, 1916, Congress placed $20,000,000 at the disposal of the president for investigation of "the best, cheapest and most available means for the production of nitrate and other products for munitions of war and useful in the manufacture of fertilizers and other useful products by water power or any other power." But by the time war was declared on April 6, 1917, no definite program had been approved and by the time the armistice was signed on November 11, 1918, no plants were in active operation. But five plants had been started and two of them were nearly ready to begin work when they were closed by the ending of the war. United States Nitrate Plant No. 1 was located at Sheffield, Alabama, and was designed for the production of ammonia by "direct action" from nitrogen and hydrogen according to the plans of the American Chemical Company. Its capacity was calculated at 60,000 pounds of anhydrous ammonia a day, half of which was to be oxidized to nitric acid. Plant No. 2 was erected at Muscle Shoals, Alabama, to use the process of the American Cyanamid Company. This was contracted to produce 110,000 tons of ammonium nitrate a year and later two other cyanamid plants of half that capacity were started at Toledo and Ancor, Ohio.

At Muscle Shoals a mushroom city of 20,000 sprang up on an Alabama cotton field in six months. The raw material, air, was as abundant there as anywhere and the power, water, could be obtained from the Government hydro-electric plant on the Tennessee River, but this was not available during the war, so steam was employed instead. The heat of the coal was used to cool the air down to the liquefying point. The principle of this process is simple. Everybody knows that heat expands and cold contracts, but not everybody has realized the converse of this rule, that expansion cools and compression heats. If air is forced into smaller space, as in a tire pump, it heats up and if allowed to expand to ordinary pressure it cools off again. But if the air while compressed is cooled and then allowed to expand it must get still colder and the process can go on till it becomes cold enough to congeal. That is, by expanding a great deal of air, a little of it can be reduced to the liquefying point. At Muscle Shoals the plant for liquefying air, in order to get the nitrogen out of it, consisted of two dozen towers each capable of producing 1765 cubic feet of pure nitrogen per hour. The air was drawn in through two pipes, a yard across, and passed through scrubbing towers to remove impurities. The air was then compressed to 600 pounds per square inch. Nine tenths of the air was permitted to expand to 50 pounds and this expansion cooled down the other tenth, still under high pressure, to the liquefying point. Rectifying towers 24 feet high were stacked with trays of liquid air from which the nitrogen was continually bubbling off since its boiling point is twelve degrees centigrade lower than that of oxygen. Pure nitrogen gas collected at the top of the tower and the residual liquid air, now about half oxygen, was allowed to escape at the bottom.

The nitrogen was then run through pipes into the lime-nitrogen ovens. There were 1536 of these about four feet square and each holding 1600 pounds of pulverized calcium carbide. This is at first heated by an electrical current to start the reaction which afterwards produces enough heat to keep it going. As the stream of nitrogen gas passes over the finely divided carbide it is absorbed to form calcium cyanamid as described on a previous page. This product is cooled, powdered and wet to destroy any quicklime or carbide left unchanged. Then it is charged into autoclaves and steam at high temperature and pressure is admitted. The steam acting on the cyanamid sets free ammonia gas which is carried to towers down which cold water is sprayed, giving the ammonia water, familiar to the kitchen and the bathroom.

But since nitric acid rather than ammonia was needed for munitions, the oxygen of the air had to be called into play. This process, as already explained, is carried on by aid of a catalyzer, in this case platinum wire. At Muscle Shoals there were 696 of these catalyzer boxes. The ammonia gas, mixed with air to provide the necessary oxygen, was admitted at the top and passed down through a sheet of platinum gauze of 80 mesh to the inch, heated to incandescence by electricity. In contact with this the ammonia is converted into gaseous oxides of nitrogen (the familiar red fumes of the laboratory) which, carried off in pipes, cooled and dissolved in water, form nitric acid.

But since none of the national plants could be got into action during the war, the United States was compelled to draw upon South America for its supply. The imports of Chilean saltpeter rose from half a million tons in 1914 to a million and a half in 1917. After peace was made the Department of War turned over to the Department of Agriculture its surplus of saltpeter, 150,000 tons, and it was sold to American farmers at cost, $81 a ton.

For nitrogen plays a double role in human economy. It appears like Brahma in two aspects, Vishnu the Preserver and Siva the Destroyer. Here I have been considering nitrogen in its maleficent aspect, its use in war. We now turn to its beneficent aspect, its use in peace.



III

FEEDING THE SOIL

The Great War not only starved people: it starved the land. Enough nitrogen was thrown away in some indecisive battle on the Aisne to save India from a famine. The population of Europe as a whole has not been lessened by the war, but the soil has been robbed of its power to support the population. A plant requires certain chemical elements for its growth and all of these must be within reach of its rootlets, for it will accept no substitutes. A wheat stalk in France before the war had placed at its feet nitrates from Chile, phosphates from Florida and potash from Germany. All these were shut off by the firing line and the shortage of shipping.

Out of the eighty elements only thirteen are necessary for crops. Four of these are gases: hydrogen, oxygen, nitrogen and chlorine. Five are metals: potassium, magnesium, calcium, iron and sodium. Four are non-metallic solids: carbon, sulfur, phosphorus and silicon. Three of these, hydrogen, oxygen and carbon, making up the bulk of the plant, are obtainable ad libitum from the air and water. The other ten in the form of salts are dissolved in the water that is sucked up from the soil. The quantity needed by the plant is so small and the quantity contained in the soil is so great that ordinarily we need not bother about the supply except in case of three of them. They are nitrogen, potassium and phosphorus. These would be useless or fatal to plant life in the elemental form, but fixed in neutral salt they are essential plant foods. A ton of wheat takes away from the soil about 47 pounds of nitrogen, 18 pounds of phosphoric acid and 12 pounds of potash. If then the farmer does not restore this much to his field every year he is drawing upon his capital and this must lead to bankruptcy in the long run.

So much is easy to see, but actually the question is extremely complicated. When the German chemist, Justus von Liebig, pointed out in 1840 the possibility of maintaining soil fertility by the application of chemicals it seemed at first as though the question were practically solved. Chemists assumed that all they had to do was to analyze the soil and analyze the crop and from this figure out, as easily as balancing a bank book, just how much of each ingredient would have to be restored to the soil every year. But somehow it did not work out that way and the practical agriculturist, finding that the formulas did not fit his farm, sneered at the professors and whenever they cited Liebig to him he irreverently transposed the syllables of the name. The chemist when he went deeper into the subject saw that he had to deal with the colloids, damp, unpleasant, gummy bodies that he had hitherto fought shy of because they would not crystallize or filter. So the chemist called to his aid the physicist on the one hand and the biologist on the other and then they both had their hands full. The physicist found that he had to deal with a polyvariant system of solids, liquids and gases mutually miscible in phases too numerous to be handled by Gibbs's Rule. The biologist found that he had to deal with the invisible flora and fauna of a new world.

Plants obey the injunction of Tennyson and rise on the stepping stones of their dead selves to higher things. Each successive generation lives on what is left of the last in the soil plus what it adds from the air and sunshine. As soon as a leaf or tree trunk falls to the ground it is taken in charge by a wrecking crew composed of a myriad of microscopic organisms who proceed to break it up into its component parts so these can be used for building a new edifice. The process is called "rotting" and the product, the black, gummy stuff of a fertile soil, is called "humus." The plants, that is, the higher plants, are not able to live on their own proteids as the animals are. But there are lower plants, certain kinds of bacteria, that can break up the big complicated proteid molecules into their component parts and reduce the nitrogen in them to ammonia or ammonia-like compounds. Having done this they stop and turn over the job to another set of bacteria to be carried through the next step. For you must know that soil society is as complex and specialized as that above ground and the tiniest bacterium would die rather than violate the union rules. The second set of bacteria change the ammonia over to nitrites and then a third set, the Amalgamated Union of Nitrate Workers, steps in and completes the process of oxidation with an efficiency that Ostwald might envy, for ninety-six per cent. of the ammonia of the soil is converted into nitrates. But if the conditions are not just right, if the food is insufficient or unwholesome or if the air that circulates through the soil is contaminated with poison gases, the bacteria go on a strike. The farmer, not seeing the thing from the standpoint of the bacteria, says the soil is "sick" and he proceeds to doctor it according to his own notion of what ails it. First perhaps he tries running in strike breakers. He goes to one of the firms that makes a business of supplying nitrogen-fixing bacteria from the scabs or nodules of the clover roots and scatters these colonies over the field. But if the living conditions remain bad the newcomers will soon quit work too and the farmer loses his money. If he is wise, then, he will remedy the conditions, putting a better ventilation system in his soil perhaps or neutralizing the sourness by means of lime or killing off the ameboid banditti that prey upon the peaceful bacteria engaged in the nitrogen industry. It is not an easy job that the farmer has in keeping billions of billions of subterranean servants contented and working together, but if he does not succeed at this he wastes his seed and labor.

The layman regards the soil as a platform or anchoring place on which to set plants. He measures its value by its superficial area without considering its contents, which is as absurd as to estimate a man's wealth by the size of his safe. The difference in point of view is well illustrated by the old story of the city chap who was showing his farmer uncle the sights of New York. When he took him to Central Park he tried to astonish him by saying "This land is worth $500,000 an acre." The old farmer dug his toe into the ground, kicked out a clod, broke it open, looked at it, spit on it and squeezed it in his hand and then said, "Don't you believe it; 'tain't worth ten dollars an acre. Mighty poor soil I call it." Both were right.



The modern agriculturist realizes that the soil is a laboratory for the production of plant food and he ordinarily takes more pains to provide a balanced ration for it than he does for his family. Of course the necessity of feeding the soil has been known ever since man began to settle down and the ancient methods of maintaining its fertility, though discovered accidentally and followed blindly, were sound and efficacious. Virgil, who like Liberty Hyde Bailey was fond of publishing agricultural bulletins in poetry, wrote two thousand years ago:

But sweet vicissitudes of rest and toil Make easy labor and renew the soil Yet sprinkle sordid ashes all around And load with fatt'ning dung thy fallow soil.

The ashes supplied the potash and the dung the nitrate and phosphate. Long before the discovery of the nitrogen-fixing bacteria, the custom prevailed of sowing pea-like plants every third year and then plowing them under to enrich the soil. But such local supplies were always inadequate and as soon as deposits of fertilizers were discovered anywhere in the world they were drawn upon. The richest of these was the Chincha Islands off the coast of Peru, where millions of penguins and pelicans had lived in a most untidy manner for untold centuries. The guano composed of the excrement of the birds mixed with the remains of dead birds and the fishes they fed upon was piled up to a depth of 120 feet. From this Isle of Penguins—which is not that described by Anatole France—a billion dollars' worth of guano was taken and the deposit was soon exhausted.

Then the attention of the world was directed to the mainland of Peru and Chile, where similar guano deposits had been accumulated and, not being washed away on account of the lack of rain, had been deposited as sodium nitrate, or "saltpeter." These beds were discovered by a German, Taddeo Haenke, in 1809, but it was not until the last quarter of the century that the nitrates came into common use as a fertilizer. Since then more than 53,000,000 tons have been taken out of these beds and the exportation has risen to a rate of 2,500,000 to 3,000,000 tons a year. How much longer they will last is a matter of opinion and opinion is largely influenced by whether you have your money invested in Chilean nitrate stock or in one of the new synthetic processes for making nitrates. The United States Department of Agriculture says the nitrate beds will be exhausted in a few years. On the other hand the Chilean Inspector General of Nitrate Deposits in his latest official report says that they will last for two hundred years at the present rate and that then there are incalculable areas of low grade deposits, containing less than eleven per cent., to be drawn upon.

Anyhow, the South American beds cannot long supply the world's need of nitrates and we shall some time be starving unless creative chemistry comes to the rescue. In 1898 Sir William Crookes—the discoverer of the "Crookes tubes," the radiometer and radiant matter—startled the British Association for the Advancement of Science by declaring that the world was nearing the limit of wheat production and that by 1931 the bread-eaters, the Caucasians, would have to turn to other grains or restrict their population while the rice and millet eaters of Asia would continue to increase. Sir William was laughed at then as a sensationalist. He was, but his sensations were apt to prove true and it is already evident that he was too near right for comfort. Before we were half way to the date he set we had two wheatless days a week, though that was because we persisted in shooting nitrates into the air. The area producing wheat was by decades:[1]

THE WHEAT FIELDS OF THE WORLD

Acres

1881-90 192,000,000 1890-1900 211,000,000 1900-10 242,000,000 Probable limit 300,000,000

If 300,000,000 acres can be brought under cultivation for wheat and the average yield raised to twenty bushels to the acre, that will give enough to feed a billion people if they eat six bushels a year as do the English. Whether this maximum is correct or not there is evidently some limit to the area which has suitable soil and climate for growing wheat, so we are ultimately thrown back upon Crookes's solution of the problem; that is, we must increase the yield per acre and this can only be done by the use of fertilizers and especially by the fixation of atmospheric nitrogen. Crookes estimated the average yield of wheat at 12.7 bushels to the acre, which is more than it is in the new lands of the United States, Australia and Russia, but less than in Europe, where the soil is well fed. What can be done to increase the yield may be seen from these figures:

GAIN IN THE YIELD OF WHEAT IN BUSHELS PER ACRE

1889-90 1913

Germany 19 35 Belgium 30 35 France 17 20 United Kingdom 28 32 United States 12 15

The greatest gain was made in Germany and we see a reason for it in the fact that the German importation of Chilean saltpeter was 55,000 tons in 1880 and 747,000 tons in 1913. In potatoes, too, Germany gets twice as big a crop from the same ground as we do, 223 bushels per acre instead of our 113 bushels. But the United States uses on the average only 28 pounds of fertilizer per acre, while Europe uses 200.

It is clear that we cannot rely upon Chile, but make nitrates for ourselves as Germany had to in war time. In the first chapter we considered the new methods of fixing the free nitrogen from the air. But the fixation of nitrogen is a new business in this country and our chief reliance so far has been the coke ovens. When coal is heated in retorts or ovens for making coke or gas a lot of ammonia comes off with the other products of decomposition and is caught in the sulfuric acid used to wash the gas as ammonium sulfate. Our American coke-makers have been in the habit of letting this escape into the air and consequently we have been losing some 700,000 tons of ammonium salts every year, enough to keep our land rich and give us all the explosives we should need. But now they are reforming and putting in ovens that save the by-products such as ammonia and coal tar, so in 1916 we got from this source 325,000 tons a year.



Germany had a natural monopoly of potash as Chile had a natural monopoly of nitrates. The agriculture of Europe and America has been virtually dependent upon these two sources of plant foods. Now when the world was cleft in twain by the shock of August, 1914, the Allied Powers had the nitrates and the Central Powers had the potash. If Germany had not had up her sleeve a new process for making nitrates she could not long have carried on a war and doubtless would not have ventured upon it. But the outside world had no such substitute for the German potash salts and has not yet discovered one. Consequently the price of potash in the United States jumped from $40 to $400 and the cost of food went up with it. Even under the stimulus of prices ten times the normal and with chemists searching furnace crannies and bad lands the United States was able to scrape up less than 10,000 tons of potash in 1916, and this was barely enough to satisfy our needs for two weeks!



Yet potash compounds are as cheap as dirt. Pick up a handful of gravel and you will be able to find much of it feldspar or other mineral containing some ten per cent. of potash. Unfortunately it is in combination with silica, which is harder to break up than a trust.

But "constant washing wears away stones" and the potash that the metallurgist finds too hard to extract in his hottest furnace is washed out in the course of time through the dropping of the gentle rain from heaven. "All rivers run to the sea" and so the sea gets salt, all sorts of salts, principally sodium chloride (our table salt) and next magnesium, calcium and potassium chlorides or sulfates in this order of abundance. But if we evaporate sea-water down to dryness all these are left in a mix together and it is hard to sort them out. Only patient Nature has time for it and she only did on a large scale in one place, that is at Stassfurt, Germany. It seems that in the days when northwestern Prussia was undetermined whether it should be sea or land it was flooded annually by sea-water. As this slowly evaporated the dissolved salts crystallized out at the critical points, leaving beds of various combinations. Each year there would be deposited three to five inches of salts with a thin layer of calcium sulfate or gypsum on top. Counting these annual layers, like the rings on a stump, we find that the Stassfurt beds were ten thousand years in the making. They were first worked for their salt, common salt, alone, but in 1837 the Prussian Government began prospecting for new and deeper deposits and found, not the clean rock salt that they wanted, but bittern, largely magnesium sulfate or Epsom salt, which is not at all nice for table use. This stuff was first thrown away until it was realized that it was much more valuable for the potash it contains than was the rock salt they were after. Then the Germans began to purify the Stassfurt salts and market them throughout the world. They contain from fifteen to twenty-five per cent. of magnesium chloride mixed with magnesium chloride in "carnallite," with magnesium sulfate in "kainite" and sodium chloride in "sylvinite." More than thirty thousand miners and workmen are employed in the Stassfurt works. There are some seventy distinct establishments engaged in the business, but they are in combination. In fact they are compelled to be, for the German Government is as anxious to promote trusts as the American Government is to prevent them. Once the Stassfurt firms had a falling out and began a cutthroat competition. But the German Government objects to its people cutting each other's throats. American dealers were getting unheard of bargains when the German Government stepped in and compelled the competing corporations to recombine under threat of putting on an export duty that would eat up their profits.

The advantages of such business cooeperation are specially shown in opening up a new market for an unknown product as in the case of the introduction of the Stassfurt salts into American agriculture. The farmer in any country is apt to be set in his ways and when it comes to inducing him to spend his hard-earned money for chemicals that he never heard of and could not pronounce he—quite rightly—has to be shown. Well, he was shown. It was, if I remember right, early in the nineties that the German Kali Syndikat began operations in America and the United States Government became its chief advertising agent. In every state there was an agricultural experiment station and these were provided liberally with illustrated literature on Stassfurt salts with colored wall charts and sets of samples and free sacks of salts for field experiments. The station men, finding that they could rely upon the scientific accuracy of the information supplied by Kali and that the experiments worked out well, became enthusiastic advocates of potash fertilizers. The station bulletins—which Uncle Sam was kind enough to carry free to all the farmers of the state—sometimes were worded so like the Kali Company advertising that the company might have raised a complaint of plagiarizing, but they never did. The Chilean nitrates, which are under British control, were later introduced by similar methods through the agency of the state agricultural experiment stations.

As a result of all this missionary work, which cost the Kali Company $50,000 a year, the attention of a large proportion of American farmers was turned toward intensive farming and they began to realize the necessity of feeding the soil that was feeding them. They grew dependent upon these two foreign and widely separated sources of supply. In the year before the war the United States imported a million tons of Stassfurt salts, for which the farmers paid more than $20,000,000. Then a declaration of American independence—the German embargo of 1915—cut us off from Stassfurt and for five years we had to rely upon our own resources. We have seen how Germany—shut off from Chile—solved the nitrogen problem for her fields and munition plants. It was not so easy for us—shut off from Germany—to solve the potash problem.

There is no more lack of potash in the rocks than there is of nitrogen in the air, but the nitrogen is free and has only to be caught and combined, while the potash is shut up in a granite prison from which it is hard to get it free. It is not the percentage in the soil but the percentage in the soil water that counts. A farmer with his potash locked up in silicates is like the merchant who has left the key of his safe at home in his other trousers. He may be solvent, but he cannot meet a sight draft. It is only solvent potash that passes current.