METALS, OLD AND NEW
The primitive metallurgist could only make use of such metals as he found free in nature, that is, such as had not been attacked and corroded by the ubiquitous oxygen. These were primarily gold or copper, though possibly some original genius may have happened upon a bit of meteoric iron and pounded it out into a sword. But when man found that the red ocher he had hitherto used only as a cosmetic could be made to yield iron by melting it with charcoal he opened a new era in civilization, though doubtless the ocher artists of that day denounced him as a utilitarian and deplored the decadence of the times.
Iron is one of the most timid of metals. It has a great disinclination to be alone. It is also one of the most altruistic of the elements. It likes almost every other element better than itself. It has an especial affection for oxygen, and, since this is in both air and water, and these are everywhere, iron is not long without a mate. The result of this union goes by various names in the mineralogical and chemical worlds, but in common language, which is quite good enough for our purpose, it is called iron rust.
By courtesy Mineral Foote-Notes.
From Agricola's "De Re Metallica 1550." Primitive furnace for smelting iron ore.
Not many of us have ever seen iron, the pure metal, soft, ductile and white like silver. As soon as it is exposed to the air it veils itself with a thin film of rust and becomes black and then red. For that reason there is practically no iron in the world except what man has made. It is rarer than gold, than diamonds; we find in the earth no nuggets or crystals of it the size of the fist as we find of these. But occasionally there fall down upon us out of the clear sky great chunks of it weighing tons. These meteorites are the mavericks of the universe. We do not know where they come from or what sun or planet they belonged to. They are our only visitors from space, and if all the other spheres are like these fragments we know we are alone in the universe. For they contain rustless iron, and where iron does not rust man cannot live, nor can any other animal or any plant.
Iron rusts for the same reason that a stone rolls down hill, because it gets rid of its energy that way. All things in the universe are constantly trying to get rid of energy except man, who is always trying to get more of it. Or, on second thought, we see that man is the greatest spendthrift of all, for he wants to expend so much more energy than he has that he borrows from the winds, the streams and the coal in the rocks. He robs minerals and plants of the energy which they have stored up to spend for their own purposes, just as he robs the bee of its honey and the silk worm of its cocoon.
Man's chief business is in reversing the processes of nature. That is the way he gets his living. And one of his greatest triumphs was when he discovered how to undo iron rust and get the metal out of it. In the four thousand years since he first did this he has accomplished more than in the millions of years before. Without knowing the value of iron rust man could attain only to the culture of the Aztecs and Incas, the ancient Egyptians and Assyrians.
The prosperity of modern states is dependent on the amount of iron rust which they possess and utilize. England, United States, Germany, all nations are competing to see which can dig the most iron rust out of the ground and make out of it railroads, bridges, buildings, machinery, battleships and such other tools and toys and then let them relapse into rust again. Civilization can be measured by the amount of iron rusted per capita, or better, by the amount rescued from rust.
But we are devoting so much space to the consideration of the material aspects of iron that we are like to neglect its esthetic and ethical uses. The beauty of nature is very largely dependent upon the fact that iron rust and, in fact, all the common compounds of iron are colored. Few elements can assume so many tints. Look at the paint pot cañons of the Yellowstone. Cheap glass bottles turn out brown, green, blue, yellow or black, according to the amount and kind of iron they contain. We build a house of cream-colored brick, varied with speckled brick and adorned with terra cotta ornaments of red, yellow and green, all due to iron. Iron rusts, therefore it must be painted; but what is there better to paint it with than iron rust itself? It is cheap and durable, for it cannot rust any more than a dead man can die. And what is also of importance, it is a good, strong, clean looking, endurable color. Whenever we take a trip on the railroad and see the miles of cars, the acres of roofing and wall, the towns full of brick buildings, we rejoice that iron rust is red, not white or some leas satisfying color.
We do not know why it is so. Zinc and aluminum are metals very much like iron in chemical properties, but all their salts are colorless. Why is it that the most useful of the metals forms the most beautiful compounds? Some say, Providence; some say, chance; some say nothing. But if it had not been so we would have lost most of the beauty of rocks and trees and human beings. For the leaves and the flowers would all be white, and all the men and women would look like walking corpses. Without color in the flower what would the bees and painters do? If all the grass and trees were white, it would be like winter all the year round. If we had white blood in our veins like some of the insects it would be hard lines for our poets. And what would become of our morality if we could not blush?
"As for me, I thrill to see
The bloom a velvet cheek discloses!
Made of dust! I well believe it,
So are lilies, so are roses."
An etiolated earth would be hardly worth living in.
The chlorophyll of the leaves and the hemoglobin of the blood are similar in constitution. Chlorophyll contains magnesium in place of iron but iron is necessary to its formation. We all know how pale a plant gets if its soil is short of iron. It is the iron in the leaves that enables the plants to store up the energy of the sunshine for their own use and ours. It is the iron in our blood that enables us to get the iron out of iron rust and make it into machines to supplement our feeble hands. Iron is for us internally the carrier of energy, just as in the form of a trolley wire or of a third rail it conveys power to the electric car. Withdraw the iron from the blood as indicated by the pallor of the cheeks, and we become weak, faint and finally die. If the amount of iron in the blood gets too small the disease germs that are always attacking us are no longer destroyed, but multiply without check and conquer us. When the iron ceases to work efficiently we are killed by the poison we ourselves generate.
Counting the number of iron-bearing corpuscles in the blood is now a common method of determining disease. It might also be useful in moral diagnosis. A microscopical and chemical laboratory attached to the courtroom would give information of more value than some of the evidence now obtained. For the anemic and the florid vices need very different treatment. An excess or a deficiency of iron in the body is liable to result in criminality. A chemical system of morals might be developed on this basis. Among the ferruginous sins would be placed murder, violence and licentiousness. Among the non-ferruginous, cowardice, sloth and lying. The former would be mostly sins of commission, the latter, sins of omission. The virtues could, of course, be similarly classified; the ferruginous virtues would include courage, self-reliance and hopefulness; the non-ferruginous, peaceableness, meekness and chastity. According to this ethical criterion the moral man would be defined as one whose conduct is better than we should expect from the per cent. of iron in his blood.
The reason why iron is able to serve this unique purpose of conveying life-giving air to all parts of the body is because it rusts so readily. Oxidation and de-oxidation proceed so quietly that the tenderest cells are fed without injury. The blood changes from red to blue and vice versa with greater ease and rapidity than in the corresponding alternations of social status in a democracy. It is because iron is so rustable that it is so useful. The factories with big scrap-heaps of rusting machinery are making the most money. The pyramids are the most enduring structures raised by the hand of man, but they have not sheltered so many people in their forty centuries as our skyscrapers that are already rusting.
We have to carry on this eternal conflict against rust because oxygen is the most ubiquitous of the elements and iron can only escape its ardent embraces by hiding away in the center of the earth. The united elements, known to the chemist as iron oxide and to the outside world as rust, are among the commonest of compounds and their colors, yellow and red like the Spanish flag, are displayed on every mountainside. From the time of Tubal Cain man has ceaselessly labored to divorce these elements and, having once separated them, to keep them apart so that the iron may be retained in his service. But here, as usual, man is fighting against nature and his gains, as always, are only temporary. Sooner or later his vigilance is circumvented and the metal that he has extricated by the fiery furnace returns to its natural affinity. The flint arrowheads, the bronze spearpoints, the gold ornaments, the wooden idols of prehistoric man are still to be seen in our museums, but his earliest steel swords have long since crumbled into dust.
Every year the blast furnaces of the world release 72,000,000 tons of iron from its oxides and every year a large part, said to be a quarter of that amount, reverts to its primeval forms. If so, then man after five thousand years of metallurgical industry has barely got three years ahead of nature, and should he cease his efforts for a generation there would be little left to show that man had ever learned to extract iron from its ores. The old question, "What becomes of all the pins?" may be as well asked of rails, pipes and threshing machines. The end of all iron is the same. However many may be its metamorphoses while in the service of man it relapses at last into its original state of oxidation. To save a pound of iron from corrosion is then as much a benefit to the world as to produce another pound from the ore. In fact it is of much greater benefit, for it takes four pounds of coal to produce one pound of steel, so whenever a piece of iron is allowed to oxidize it means that four times as much coal must be oxidized in order to replace it. And the beds of coal will be exhausted before the beds of iron ore.
If we are ever to get ahead, if we are to gain any respite from this enormous waste of labor and natural resources, we must find ways of preventing the iron which we have obtained and fashioned into useful tools from being lost through oxidation. Now there is only one way of keeping iron and oxygen from uniting and that is to keep them apart. A very thin dividing wall will serve for the purpose, for instance, a film of oil. But ordinary oil will rub off, so it is better to cover the surface with an oil-like linseed which oxidizes to a hard elastic and adhesive coating. If with linseed oil we mix iron oxide or some other pigment we have a paint that will protect iron perfectly so long as it is unbroken. But let the paint wear off or crack so that air can get at the iron, then rust will form and spread underneath the paint on all sides. The same is true of the porcelain-like enamel with which our kitchen iron ware is nowadays coated. So long as the enamel holds it is all right but once it is broken through at any point it begins to scale off and gets into our food.
Obviously it would be better for some purposes if we could coat our iron with another and less easily oxidized metal than with such dissimilar substances as paint or porcelain. Now the nearest relative to iron is nickel, and a layer of this of any desired thickness may be easily deposited by electricity upon any surface however irregular. Nickel takes a bright polish and keeps it well, so nickel plating has become the favorite method of protection for small objects where the expense is not prohibitive. Copper plating is used for fine wires. A sheet of iron dipped in melted tin comes out coated with a thin adhesive layer of the latter metal. Such tinned plate commonly known as "tin" has become the favorite material for pans and cans. But if the tin is scratched the iron beneath rusts more rapidly than if the tin were not there, for an electrolytic action is set up and the iron, being the negative element of the couple, suffers at the expense of the tin.
With zinc it is quite the opposite. Zinc is negative toward iron, so when the two are in contact and exposed to the weather the zinc is oxidized first. A zinc plating affords the protection of a Swiss Guard, it holds out as long as possible and when broken it perishes to the last atom before it lets the oxygen get at the iron. The zinc may be applied in four different ways. (1) It may be deposited by electrolysis as in nickel plating, but the zinc coating is more apt to be porous. (2) The sheets or articles may be dipped in a bath of melted zinc. This gives us the familiar "galvanized iron," the most useful and when well done the most effective of rust preventives. Besides these older methods of applying zinc there are now two new ones. (3) One is the Schoop process by which a wire of zinc or other metal is fed into an oxy-hydrogen air blast of such heat and power that it is projected as a spray of minute drops with the speed of bullets and any object subjected to the bombardment of this metallic mist receives a coating as thick as desired. The zinc spray is so fine and cool that it may be received on cloth, lace, or the bare hand. The Schoop metallizing process has recently been improved by the use of the electric current instead of the blowpipe for melting the metal. Two zinc wires connected with any electric system, preferably the direct, are fed into the "pistol." Where the wires meet an electric arc is set up and the melted zinc is sprayed out by a jet of compressed air. (4) In the Sherardizing process the articles are put into a tight drum with zinc dust and heated to 800° F. The zinc at this temperature attacks the iron and forms a series of alloys ranging from pure zinc on the top to pure iron at the bottom of the coating. Even if this cracks in part the iron is more or less protected from corrosion so long as any zinc remains. Aluminum is used similarly in the calorizing process for coating iron, copper or brass. First a surface alloy is formed by heating the metal with aluminum powder. Then the temperature is raised to a high degree so as to cause the aluminum on the surface to diffuse into the metal and afterwards it is again baked in contact with aluminum dust which puts upon it a protective plating of the pure aluminum which does not oxidize.
PHOTOMICROGRAPHS SHOWING THE STRUCTURE OF STEEL MADE BY PROFESSOR E.G. MARTIN OF PURDUE UNIVERSITY
1. Cold-worked steel showing ferrite and sorbite (enlarged 500 times)
2. Steel showing pearlite crystals (enlarged 500 times)
3. Structure characteristic of air-cooled steel (enlarged 50 times)
4. The triangular structure characteristic of cast steel showing ferrite and pearlite (enlarged 50 times)
Courtesy of E.G. Mahin
THE MICROSCOPIC STRUCTURE OF METALS
1. Malleabilized casting; temper carbon in ferrite (enlarged 50 times)
2. Type metal; lead-antimony alloy in matrix of lead (enlarged 100 times)
3. Gray cast iron; carbon as graphite (enlarged 500 times)
4. Steel composed of cementite (white) and pearlite (black) (enlarged 50 times)
Another way of protecting iron ware from rusting is to rust it. This is a sort of prophylactic method like that adopted by modern medicine where inoculation with a mild culture prevents a serious attack of the disease. The action of air and water on iron forms a series of compounds and mixtures of them. Those that contain least oxygen are hard, black and magnetic like iron itself. Those that have most oxygen are red and yellow powders. By putting on a tight coating of the black oxide we can prevent or hinder the oxidation from going on into the pulverulent stage. This is done in several ways. In the Bower-Barff process the articles to be treated are put into a closed retort and a current of superheated steam passed through for twenty minutes followed by a current of producer gas (carbon monoxide), to reduce any higher oxides that may have been formed. In the Gesner process a current of gasoline vapor is used as the reducing agent. The blueing of watch hands, buckles and the like may be done by dipping them into an oxidizing bath such as melted saltpeter. But in order to afford complete protection the layer of black oxide must be thickened by repeating the process which adds to the time and expense. This causes a slight enlargement and the high temperature often warps the ware so it is not suitable for nicely adjusted parts of machinery and of course tools would lose their temper by the heat.
A new method of rust proofing which is free from these disadvantages is the phosphate process invented by Thomas Watts Coslett, an English chemist, in 1907, and developed in America by the Parker Company of Detroit. This consists simply in dipping the sheet iron or articles into a tank filled with a dilute solution of iron phosphate heated nearly to the boiling point by steam pipes. Bubbles of hydrogen stream off rapidly at first, then slower, and at the end of half an hour or longer the action ceases, and the process is complete. What has happened is that the iron has been converted into a basic iron phosphate to a depth depending upon the density of articles processed. Any one who has studied elementary qualitative analysis will remember that when he added ammonia to his "unknown" solution, iron and phosphoric acid, if present, were precipitated together, or in other words, iron phosphate is insoluble except in acids. Therefore a superficial film of such phosphate will protect the iron underneath except from acids. This film is not a coating added on the outside like paint and enamel or tin and nickel plate. It is therefore not apt to scale off and it does not increase the size of the article. No high heat is required as in the Sherardizing and Bower-Barff processes, so steel tools can be treated without losing their temper or edge.
The deposit consisting of ferrous and ferric phosphates mixed with black iron oxide may be varied in composition, texture and color. It is ordinarily a dull gray and oiling gives a soft mat black more in accordance with modern taste than the shiny nickel plating that delighted our fathers. Even the military nowadays show more quiet taste than formerly and have abandoned their glittering accoutrements.
The phosphate bath is not expensive and can be used continuously for months by adding more of the concentrated solution to keep up the strength and removing the sludge that is precipitated. Besides the iron the solution contains the phosphates of other metals such as calcium or strontium, manganese, molybdenum, or tungsten, according to the particular purpose. Since the phosphating solution does not act on nickel it may be used on articles that have been partly nickel-plated so there may be produced, for instance, a bright raised design against a dull black background. Then, too, the surface left by the Parker process is finely etched so it affords a good attachment for paint or enamel if further protection is needed. Even if the enamel does crack, the iron beneath is not so apt to rust and scale off the coating.
These, then, are some of the methods which are now being used to combat our eternal enemy, the rust that doth corrupt. All of them are useful in their several ways. No one of them is best for all purposes. The claim of "rust-proof" is no more to be taken seriously than "fire-proof." We should rather, if we were finical, have to speak of "rust-resisting" coatings as we do of "slow-burning" buildings. Nature is insidious and unceasing in her efforts to bring to ruin the achievements of mankind and we need all the weapons we can find to frustrate her destructive determination.
But it is not enough for us to make iron superficially resistant to rust from the atmosphere. We should like also to make it so that it would withstand corrosion by acids, then it could be used in place of the large and expensive platinum or porcelain evaporating pans and similar utensils employed in chemical works. This requirement also has been met in the non-corrosive forms of iron, which have come into use within the last five years. One of these, "tantiron," invented by a British metallurgist, Robert N. Lennox, in 1912, contains 15 per cent. of silicon. Similar products are known as "duriron" and "Buflokast" in America, "metilure" in France, "ileanite" in Italy and "neutraleisen" in Germany. It is a silvery-white close-grained iron, very hard and rather brittle, somewhat like cast iron but with silicon as the main additional ingredient in place of carbon. It is difficult to cut or drill but may be ground into shape by the new abrasives. It is rustproof and is not attacked by sulfuric, nitric or acetic acid, hot or cold, diluted or concentrated. It does not resist so well hydrochloric acid or sulfur dioxide or alkalies.
The value of iron lies in its versatility. It is a dozen metals in one. It can be made hard or soft, brittle or malleable, tough or weak, resistant or flexible, elastic or pliant, magnetic or non-magnetic, more or less conductive to electricity, by slight changes of composition or mere differences of treatment. No wonder that the medieval mind ascribed these mysterious transformations to witchcraft. But the modern micrometallurgist, by etching the surface of steel and photographing it, shows it up as composite as a block of granite. He is then able to pick out its component minerals, ferrite, austenite, martensite, pearlite, graphite, cementite, and to show how their abundance, shape and arrangement contribute to the strength or weakness of the specimen. The last of these constituents, cementite, is a definite chemical compound, an iron carbide, Fe3C, containing 6.6 per cent. of carbon, so hard as to scratch glass, very brittle, and imparting these properties to hardened steel and cast iron.
With this knowledge at his disposal the iron-maker can work with his eyes open and so regulate his melt as to cause these various constituents to crystallize out as he wants them to. Besides, he is no longer confined to the alloys of iron and carbon. He has ransacked the chemical dictionary to find new elements to add to his alloys, and some of these rarities have proved to possess great practical value. Vanadium, for instance, used to be put into a fine print paragraph in the back of the chemistry book, where the class did not get to it until the term closed. Yet if it had not been for vanadium steel we should have no Ford cars. Tungsten, too, was relegated to the rear, and if the student remembered it at all it was because it bothered him to understand why its symbol should be W instead of T. But the student of today studies his lesson in the light of a tungsten wire and relieves his mind by listening to a phonograph record played with a "tungs-tone" stylus. When I was assistant in chemistry an "analysis" of steel consisted merely in the determination of its percentage of carbon, and I used to take Saturday for it so I could have time enough to complete the combustion. Now the chemists of a steel works' laboratory may have to determine also the tungsten, chromium, vanadium, titanium, nickel, cobalt, phosphorus, molybdenum, manganese, silicon and sulfur, any or all of them, and be spry about it, because if they do not get the report out within fifteen minutes while the steel is melting in the electrical furnace the whole batch of 75 tons may go wrong. I'm glad I quit the laboratory before they got to speeding up chemists so.
The quality of the steel depends upon the presence and the relative proportions of these ingredients, and a variation of a tenth of 1 per cent. in certain of them will make a different metal out of it. For instance, the steel becomes stronger and tougher as the proportion of nicked is increased up to about 15 per cent. Raising the percentage to 25 we get an alloy that does not rust or corrode and is non-magnetic, although both its component metals, iron and nickel, are by themselves attracted by the magnet. With 36 per cent. nickel and 5 per cent. manganese we get the alloy known as "invar," because it expands and contracts very little with changes of temperature. A bar of the best form of invar will expand less than one-millionth part of its length for a rise of one degree Centigrade at ordinary atmospheric temperature. For this reason it is used in watches and measuring instruments. The alloy of iron with 46 per cent. nickel is called "platinite" because its rate of expansion and contraction is the same as platinum and glass, and so it can be used to replace the platinum wire passing through the glass of an electric light bulb.
A manganese steel of 11 to 14 per cent. is too hard to be machined. It has to be cast or ground into shape and is used for burglar-proof safes and armor plate. Chrome steel is also hard and tough and finds use in files, ball bearings and projectiles. Titanium, which the iron-maker used to regard as his implacable enemy, has been drafted into service as a deoxidizer, increasing the strength and elasticity of the steel. It is reported from France that the addition of three-tenths of 1 per cent. of zirconium to nickel steel has made it more resistant to the German perforating bullets than any steel hitherto known. The new "stainless" cutlery contains 12 to 14 per cent. of chromium.
With the introduction of harder steels came the need of tougher tools to work them. Now the virtue of a good tool steel is the same as of a good man. It must be able to get hot without losing its temper. Steel of the old-fashioned sort, as everybody knows, gets its temper by being heated to redness and suddenly cooled by quenching or plunging it into water or oil. But when the point gets heated up again, as it does by friction in a lathe, it softens and loses its cutting edge. So the necessity of keeping the tool cool limited the speed of the machine.
But about 1868 a Sheffield metallurgist, Robert F. Mushet, found that a piece of steel he was working with did not require quenching to harden it. He had it analyzed to discover the meaning of this peculiarity and learned that it contained tungsten, a rare metal unrecognized in the metallurgy of that day. Further investigation showed that steel to which tungsten and manganese or chromium had been added was tougher and retained its temper at high temperature better than ordinary carbon steel. Tools made from it could be worked up to a white heat without losing their cutting power. The new tools of this type invented by "Efficiency" Taylor at the Bethlehem Steel Works in the nineties have revolutionized shop practice the world over. A tool of the old sort could not cut at a rate faster than thirty feet a minute without overheating, but the new tungsten tools will plow through steel ten times as fast and can cut away a ton of the material in an hour. By means of these high-speed tools the United States was able to turn out five times the munitions that it could otherwise have done in the same time. On the other hand, if Germany alone had possessed the secret of the modern steels no power could have withstood her. A slight superiority in metallurgy has been the deciding factor in many a battle. Those of my readers who have had the advantages of Sunday school training will recall the case described in I Samuel 13:19-22.
By means of these new metals armor plate has been made invulnerable—except to projectiles pointed with similar material. Flying has been made possible through engines weighing no more than two pounds per horse power. The cylinders of combustion engines and the casing of cannon have been made to withstand the unprecedented pressure and corrosive action of the fiery gases evolved within. Castings are made so hard that they cannot be cut—save with tools of the same sort. In the high-speed tools now used 20 or 30 per cent, of the iron is displaced by other ingredients; for example, tungsten from 14 to 25 per cent., chromium from 2 to 7 per cent., vanadium from 1/2 to 1-1/2 per cent., carbon from 6 to 8 per cent., with perhaps cobalt up to 4 per cent. Molybdenum or uranium may replace part of the tungsten.
Some of the newer alloys for high-speed tools contain no iron at all. That which bears the poetic name of star-stone, stellite, is composed of chromium, cobalt and tungsten in varying proportions. Stellite keeps a hard cutting edge and gets tougher as it gets hotter. It is very hard and as good for jewelry as platinum except that it is not so expensive. Cooperite, its rival, is an alloy of nickel and zirconium, stronger, lighter and cheaper than stellite.
Before the war nearly half of the world's supply of tungsten ore (wolframite) came from Burma. But although Burma had belonged to the British for a hundred years they had not developed its mineral resources and the tungsten trade was monopolized by the Germans. All the ore was shipped to Germany and the British Admiralty was content to buy from the Germans what tungsten was needed for armor plate and heavy guns. When the war broke out the British had the ore supply, but were unable at first to work it because they were not familiar with the processes. Germany, being short of tungsten, had to sneak over a little from Baltimore in the submarine Deutschland. In the United States before the war tungsten ore was selling at $6.50 a unit, but by the beginning of 1916 it had jumped to $85 a unit. A unit is 1 per cent. of tungsten trioxide to the ton, that is, twenty pounds. Boulder County, Colorado, and San Bernardino, California, then had mining booms, reminding one of older times. Between May and December, 1918, there was manufactured in the United States more than 45,500,000 pounds of tungsten steel containing some 8,000,000 pounds of tungsten.
If tungsten ores were more abundant and the metal more easily manipulated, it would displace steel for many purposes. It is harder than steel or even quartz. It never rusts and is insoluble in acids. Its expansion by heat is one-third that of iron. It is more than twice as heavy as iron and its melting point is twice as high. Its electrical resistance is half that of iron and its tensile strength is a third greater than the strongest steel. It can be worked into wire .0002 of an inch in diameter, almost too thin to be seen, but as strong as copper wire ten times the size.
The tungsten wires in the electric lamps are about .03 of an inch in diameter, and they give three times the light for the same consumption of electricity as the old carbon filament. The American manufacturers of the tungsten bulb have very appropriately named their lamp "Mazda" after the light god of the Zoroastrians. To get the tungsten into wire form was a problem that long baffled the inventors of the world, for it was too refractory to be melted in mass and too brittle to be drawn. Dr. W.D. Coolidge succeeded in accomplishing the feat in 1912 by reducing the tungstic acid by hydrogen and molding the metallic powder into a bar by pressure. This is raised to a white heat in the electric furnace, taken out and rolled down, and the process repeated some fifty times, until the wire is small enough so it can be drawn at a red heat through diamond dies of successively smaller apertures.
The German method of making the lamp filaments is to squirt a mixture of tungsten powder and thorium oxide through a perforated diamond of the desired diameter. The filament so produced is drawn through a chamber heated to 2500° C. at a velocity of eight feet an hour, which crystallizes the tungsten into a continuous thread.
The first metallic filament used in the electric light on a commercial scale was made of tantalum, the metal of Tantalus. In the period 1905-1911 over 100,000,000 tantalus lamps were sold, but tungsten displaced them as soon as that metal could be drawn into wire.
A recent rival of tungsten both as a filament for lamps and hardener for steel is molybdenum. One pound of this metal will impart more resiliency to steel than three or four pounds of tungsten. The molybdenum steel, because it does not easily crack, is said to be serviceable for armor-piercing shells, gun linings, air-plane struts, automobile axles and propeller shafts. In combination with its rival as a tungsten-molybdenum alloy it is capable of taking the place of the intolerably expensive platinum, for it resists corrosion when used for spark plugs and tooth plugs. European steel men have taken to molybdenum more than Americans. The salts of this metal can be used in dyeing and photography.
Calcium, magnesium and aluminum, common enough in their compounds, have only come into use as metals since the invention of the electric furnace. Now the photographer uses magnesium powder for his flashlight when he wants to take a picture of his friends inside the house, and the aviator uses it when he wants to take a picture of his enemies on the open field. The flares prepared by our Government for the war consist of a sheet iron cylinder, four feet long and six inches thick, containing a stick of magnesium attached to a tightly rolled silk parachute twenty feet in diameter when expanded. The whole weighed 32 pounds. On being dropped from the plane by pressing a button, the rush of air set spinning a pinwheel at the bottom which ignited the magnesium stick and detonated a charge of black powder sufficient to throw off the case and release the parachute. The burning flare gave off a light of 320,000 candle power lasting for ten minutes as the parachute slowly descended. This illuminated the ground on the darkest night sufficiently for the airman to aim his bombs or to take photographs.
The addition of 5 or 10 per cent. of magnesium to aluminum gives an alloy (magnalium) that is almost as light as aluminum and almost as strong as steel. An alloy of 90 per cent. aluminum and 10 per cent. calcium is lighter and harder than aluminum and more resistant to corrosion. The latest German airplane, the "Junker," was made entirely of duralumin. Even the wings were formed of corrugated sheets of this alloy instead of the usual doped cotton-cloth. Duralumin is composed of about 85 per cent. of aluminum, 5 per cent. of copper, 5 per cent. of zinc and 2 per cent. of tin.
When platinum was first discovered it was so cheap that ingots of it were gilded and sold as gold bricks to unwary purchasers. The Russian Government used it as we use nickel, for making small coins. But this is an exception to the rule that the demand creates the supply. Platinum is really a "rare metal," not merely an unfamiliar one. Nowhere except in the Urals is it found in quantity, and since it seems indispensable in chemical and electrical appliances, the price has continually gone up. Russia collapsed into chaos just when the war work made the heaviest demand for platinum, so the governments had to put a stop to its use for jewelry and photography. The "gold brick" scheme would now have to be reversed, for gold is used as a cheaper metal to "adulterate" platinum. All the members of the platinum family, formerly ignored, were pressed into service, palladium, rhodium, osmium, iridium, and these, alloyed with gold or silver, were employed more or less satisfactorily by the dentist, chemist and electrician as substitutes for the platinum of which they had been deprived. One of these alloys, composed of 20 per cent. palladium and 80 per cent. gold, and bearing the telescoped name of "palau" (palladium au-rum) makes very acceptable crucibles for the laboratory and only costs half as much as platinum. "Rhotanium" is a similar alloy recently introduced. The points of our gold pens are tipped with an osmium-iridium alloy. It is a pity that this family of noble metals is so restricted, for they are unsurpassed in tenacity and incorruptibility. They could be of great service to the world in war and peace. As the "Bad Child" says in his "Book of Beasts":
I shoot the hippopotamus with bullets made of platinum,
Because if I use leaden ones, his hide is sure to flatten 'em.
Along in the latter half of the last century chemists had begun to perceive certain regularities and relationships among the various elements, so they conceived the idea that some sort of a pigeon-hole scheme might be devised in which the elements could be filed away in the order of their atomic weights so that one could see just how a certain element, known or unknown, would behave from merely observing its position in the series. Mendeléef, a Russian chemist, devised the most ingenious of such systems called the "periodic law" and gave proof that there was something in his theory by predicting the properties of three metallic elements, then unknown but for which his arrangement showed three empty pigeon-holes. Sixteen years later all three of these predicted elements had been discovered, one by a Frenchman, one by a German and one by a Scandinavian, and named from patriotic impulse, gallium, germanium and scandium. This was a triumph of scientific prescience as striking as the mathematical proof of the existence of the planet Neptune by Leverrier before it had been found by the telescope.
But although Mendeléef's law told "the truth," it gradually became evident that it did not tell "the whole truth and nothing but the truth," as the lawyers put it. As usually happens in the history of science the hypothesis was found not to explain things so simply and completely as was at first assumed. The anomalies in the arrangement did not disappear on closer study, but stuck out more conspicuously. Though Mendeléef had pointed out three missing links, he had failed to make provision for a whole group of elements since discovered, the inert gases of the helium-argon group. As we now know, the scheme was built upon the false assumptions that the elements are immutable and that their atomic weights are invariable.
The elements that the chemists had most difficulty in sorting out and identifying were the heavy metals found in the "rare earths." There were about twenty of them so mixed up together and so much alike as to baffle all ordinary means of separating them. For a hundred years chemists worked over them and quarreled over them before they discovered that they had a commercial value. It was a problem as remote from practicality as any that could be conceived. The man in the street did not see why chemists should care whether there were two didymiums any more than why theologians should care whether there were two Isaiahs. But all of a sudden, in 1885, the chemical puzzle became a business proposition. The rare earths became household utensils and it made a big difference with our monthly gas bills whether the ceria and the thoria in the burner mantles were absolutely pure or contained traces of some of the other elements that were so difficult to separate.
This sudden change of venue from pure to applied science came about through a Viennese chemist, Dr. Carl Auer, later and in consequence known as Baron Auer von Welsbach. He was trying to sort out the rare earths by means of the spectroscopic method, which consists ordinarily in dipping a platinum wire into a solution of the unknown substance and holding it in a colorless gas flame. As it burns off, each element gives a characteristic color to the flame, which is seen as a series of lines when looked at through the spectroscope. But the flash of the flame from the platinum wire was too brief to be studied, so Dr. Auer hit upon the plan of soaking a thread in the liquid and putting this in the gas jet. The cotton of course burned off at once, but the earths held together and when heated gave off a brilliant white light, very much like the calcium or limelight which is produced by heating a stick of quicklime in the oxy-hydrogen flame. But these rare earths do not require any such intense heat as that, for they will glow in an ordinary gas jet.
So the Welsbach mantle burner came into use everywhere and rescued the coal gas business from the destruction threatened by the electric light. It was no longer necessary to enrich the gas with oil to make its flame luminous, for a cheaper fuel gas such as is used for a gas stove will give, with a mantle, a fine white light of much higher candle power than the ordinary gas jet. The mantles are knit in narrow cylinders on machines, cut off at suitable lengths, soaked in a solution of the salts of the rare earths and dried. Artificial silk (viscose) has been found better than cotton thread for the mantles, for it is solid, not hollow, more uniform in quality and continuous instead of being broken up into one-inch fibers. There is a great deal of difference in the quality of these mantles, as every one who has used them knows. Some that give a bright glow at first with the gas-cock only half open will soon break up or grow dull and require more gas to get any kind of a light out of them. Others will last long and grow better to the last. Slight impurities in the earths or the gas will speedily spoil the light. The best results are obtained from a mixture of 99 parts thoria and 1 part ceria. It is the ceria that gives the light, yet a little more of it will lower the luminosity.
The non-chemical reader is apt to be confused by the strange names and their varied terminations, but he need not be when he learns that the new metals are given names ending in -um, such as sodium, cerium, thorium, and that their oxides (compounds with oxygen, the earths) are given the termination -a, like soda, ceria, thoria. So when he sees a name ending in -um let him picture to himself a metal, any metal since they mostly look alike, lead or silver, for example. And when he comes across a name ending in -a he may imagine a white powder like lime. Thorium, for instance, is, as its name implies, a metal named after the thunder god Thor, to whom we dedicate one day in each week, Thursday. Cerium gets its name from the Roman goddess of agriculture by way of the asteroid.
The chief sources of the material for the Welsbach burners is monazite, a glittering yellow sand composed of phosphate of cerium with some 5 per cent. of thorium. In 1916 the United States imported 2,500,000 pounds of monazite from Brazil and India, most of which used to go to Germany. In 1895 we got over a million and a half pounds from the Carolinas, but the foreign sand is richer and cheaper. The price of the salts of the rare metals fluctuates wildly. In 1895 thorium nitrate sold at $200 a pound; in 1913 it fell to $2.60, and in 1916 it rose to $8.
Since the monazite contains more cerium than thorium and the mantles made from it contain more thorium than cerium, there is a superfluity of cerium. The manufacturers give away a pound of cerium salts with every purchase of a hundred pounds of thorium salts. It annoyed Welsbach to see the cerium residues thrown away and accumulating around his mantle factory, so he set out to find some use for it. He reduced the mixed earths to a metallic form and found that it gave off a shower of sparks when scratched. An alloy of cerium with 30 or 35 per cent. of iron proved the best and was put on the market in the form of automatic lighters. A big business was soon built up in Austria on the basis of this obscure chemical element rescued from the dump-heap. The sale of the cerite lighters in France threatened to upset the finances of the republic, which derived large revenue from its monopoly of match-making, so the French Government imposed a tax upon every man who carried one. American tourists who bought these lighters in Germany used to be much annoyed at being held up on the French frontier and compelled to take out a license. During the war the cerium sparklers were much used in the trenches for lighting cigarettes, but—as those who have seen "The Better 'Ole" will know—they sometimes fail to strike fire. Auer-metal or cerium-iron alloy was used in munitions to ignite hand grenades and to blazon the flight of trailer shells. There are many other pyrophoric (light-producing) alloys, including steel, which our ancestors used with flint before matches and percussion caps were invented.
There are more than fifty metals known and not half of them have come into common use, so there is still plenty of room for the expansion of the science of metallurgy. If the reader has not forgotten his arithmetic of permutations he can calculate how many different alloys may be formed by varying the combinations and proportions of these fifty. We have seen how quickly elements formerly known only to chemists—and to some of them known only by name—have become indispensable in our daily life. Any one of those still unutilized may be found to have peculiar properties that fit it for filling a long unfelt want in modern civilization.
Who, for instance, will find a use for gallium, the metal of France? It was described in 1869 by Mendeléef in advance of its advent and has been known in person since 1875, but has not yet been set to work. It is such a remarkable metal that it must be good for something. If you saw it in a museum case on a cold day you might take it to be a piece of aluminum, but if the curator let you hold it in your hand—which he won't—it would melt and run over the floor like mercury. The melting point is 87° Fahr. It might be used in thermometers for measuring temperatures above the boiling point of mercury were it not for the peculiar fact that gallium wets glass so it sticks to the side of the tube instead of forming a clear convex curve on top like mercury.
Then there is columbium, the American metal. It is strange that an element named after Columbia should prove so impractical. Columbium is a metal closely resembling tantalum and tantalum found a use as electric light filaments. A columbium lamp should appeal to our patriotism.
The so-called "rare elements" are really abundant enough considering the earth's crust as a whole, though they are so thinly scattered that they are usually overlooked and hard to extract. But whenever one of them is found valuable it is soon found available. A systematic search generally reveals it somewhere in sufficient quantity to be worked. Who, then, will be the first to discover a use for indium, germanium, terbium, thulium, lanthanum, neodymium, scandium, samarium and others as unknown to us as tungsten was to our fathers?
As evidence of the statement that it does not matter how rare an element may be it will come into common use if it is found to be commonly useful, we may refer to radium. A good rich specimen of radium ore, pitchblende, may contain as much, as one part in 4,000,000. Madame Curie, the brilliant Polish Parisian, had to work for years before she could prove to the world that such an element existed and for years afterwards before she could get the metal out. Yet now we can all afford a bit of radium to light up our watch dials in the dark. The amount needed for this is infinitesimal. If it were more it would scorch our skins, for radium is an element in eruption. The atom throws off corpuscles at intervals as a Roman candle throws off blazing balls. Some of these particles, the alpha rays, are atoms of another element, helium, charged with positive electricity and are ejected with a velocity of 18,000 miles a second. Some of them, the beta rays, are negative electrons, only about one seven-thousandth the size of the others, but are ejected with almost the speed of light, 186,000 miles a second. If one of the alpha projectiles strikes a slice of zinc sulfide it makes a splash of light big enough to be seen with a microscope, so we can now follow the flight of a single atom. The luminous watch dials consist of a coating of zinc sulfide under continual bombardment by the radium projectiles. Sir William Crookes invented this radium light apparatus and called it a "spinthariscope," which is Greek for "spark-seer."
Evidently if radium is so wasteful of its substance it cannot last forever nor could it have forever existed. The elements then ate not necessarily eternal and immutable, as used to be supposed. They have a natural length of life; they are born and die and propagate, at least some of them do. Radium, for instance, is the offspring of ionium, which is the great-great-grandson of uranium, the heaviest of known elements. Putting this chemical genealogy into biblical language we might say: Uranium lived 5,000,000,000 years and begot Uranium X1, which lived 24.6 days and begot Uranium X2, which lived 69 seconds and begot Uranium 2, which lived 2,000,000 years and begot Ionium, which lived 200,000 years and begot Radium, which lived 1850 years and begot Niton, which lived 3.85 days and begot Radium A, which lived 3 minutes and begot Radium B, which lived 26.8 minutes and begot Radium C, which lived 19.5 minutes and begot Radium D, which lived 12 years and begot Radium E, which lived 5 days and begot Polonium, which lived 136 days and begot Lead.
The figures I have given are the times when half the parent substance has gone over into the next generation. It will be seen that the chemist is even more liberal in his allowance of longevity than was Moses with the patriarchs. It appears from the above that half of the radium in any given specimen will be transformed in about 2000 years. Half of what is left will disappear in the next 2000 years, half of that in the next 2000 and so on. The reader can figure out for himself when it will all be gone. He will then have the answer to the old Eleatic conundrum of when Achilles will overtake the tortoise. But we may say that after 100,000 years there would not be left any radium worth mentioning, or in other words practically all the radium now in existence is younger than the human race. The lead that is found in uranium and has presumably descended from uranium, behaves like other lead but is lighter. Its atomic weight is only 206, while ordinary lead weighs 207. It appears then that the same chemical element may have different atomic weights according to its ancestry, while on the other hand different chemical elements may have the same atomic weight. This would have seemed shocking heresy to the chemists of the last century, who prided themselves on the immutability of the elements and did not take into consideration their past life or heredity. The study of these radioactive elements has led to a new atomic theory. I suppose most of us in our youth used to imagine the atom as a little round hard ball, but now it is conceived as a sort of solar system with an electropositive nucleus acting as the sun and negative electrons revolving around it like the planets. The number of free positive electrons in the nucleus varies from one in hydrogen to 92 in uranium. This leaves room for 92 possible elements and of these all but six are more or less certainly known and definitely placed in the scheme. The atom of uranium, weighing 238 times the atom of hydrogen, is the heaviest known and therefore the ultimate limit of the elements, though it is possible that elements may be found beyond it just as the planet Neptune was discovered outside the orbit of Uranus. Considering the position of uranium and its numerous progeny as mentioned above, it is quite appropriate that this element should bear the name of the father of all the gods.
In these radioactive elements we have come upon sources of energy such as was never dreamed of in our philosophy. The most striking peculiarity of radium is that it is always a little warmer than its surroundings, no matter how warm these may be. Slowly, spontaneously and continuously, it decomposes and we know no way of hastening or of checking it. Whether it is cooled in liquefied air or heated to its melting point the change goes on just the same. An ounce of radium salt will give out enough heat in one hour to melt an ounce of ice and in the next hour will raise this water to the boiling point, and so on again and again without cessation for years, a fire without fuel, a realization of the philosopher's lamp that the alchemists sought in vain. The total energy so emitted is millions of times greater than that produced by any chemical combination such as the union of oxygen and hydrogen to form water. From the heavy white salt there is continually rising a faint fire-mist like the will-o'-the-wisp over a swamp. This gas is known as the emanation or niton, "the shining one." A pound of niton would give off energy at the rate of 23,000 horsepower; fine stuff to run a steamer, one would think, but we must remember that it does not last. By the sixth day the power would have fallen off by half. Besides, no one would dare to serve as engineer, for the radiation will rot away the flesh of a living man who comes near it, causing gnawing ulcers or curing them. It will not only break down the complex and delicate molecules of organic matter but will attack the atom itself, changing, it is believed, one element into another, again the fulfilment of a dream of the alchemists. And its rays, unseen and unfelt by us, are yet strong enough to penetrate an armorplate and photograph what is behind it.
But radium is not the most mysterious of the elements but the least so. It is giving out the secret that the other elements have kept. It suggests to us that all the other elements in proportion to their weight have concealed within them similar stores of energy. Astronomers have long dazzled our imaginations by calculating the horsepower of the world, making us feel cheap in talking about our steam engines and dynamos when a minutest fraction of the waste dynamic energy of the solar system would make us all as rich as millionaires. But the heavenly bodies are too big for us to utilize in this practical fashion.
And now the chemists have become as exasperating as the astronomers, for they give us a glimpse of incalculable wealth in the meanest substance. For wealth is measured by the available energy of the world, and if a few ounces of anything would drive an engine or manufacture nitrogenous fertilizer from the air all our troubles would be over. Kipling in his sketch, "With the Night Mail," and Wells in his novel, "The World Set Free," stretched their imaginations in trying to tell us what it would mean to have command of this power, but they are a little hazy in their descriptions of the machinery by which it is utilized. The atom is as much beyond our reach as the moon. We cannot rob its vault of the treasure.
READING REFERENCES
The foregoing pages will not have achieved their aim unless their readers have become sufficiently interested in the developments of industrial chemistry to desire to pursue the subject further in some of its branches. Assuming such interest has been aroused, I am giving below a few references to books and articles which may serve to set the reader upon the right track for additional information. To follow the rapid progress of applied science it is necessary to read continuously such periodicals as the Journal of Industrial and Engineering Chemistry (New York), Metallurgical and Chemical Engineering (New York), Journal of the Society of Chemical Industry (London), Chemical Abstracts (published by the American Chemical Society, Easton, Pa.), and the various journals devoted to special trades. The reader may need to be reminded that the United States Government publishes for free distribution or at low price annual volumes or special reports dealing with science and industry. Among these may be mentioned "Yearbook of the Department of Agriculture"; "Mineral Resources of the United States," published by the United States Geological Survey in two annual volumes, Vol. I on the metals and Vol. II on the non-metals; the "Annual Report of the Smithsonian Institution," containing selected articles on pure and applied science; the daily "Commerce Reports" and special bulletins of Department of Commerce. Write for lists of publications of these departments.
The following books on industrial chemistry in general are recommended for reading and reference: "The Chemistry of Commerce" and "Some Chemical Problems of To-Day" by Robert Kennedy Duncan (Harpers, N.Y.), "Modern Chemistry and Its Wonders" by Martin (Van Nostrand), "Chemical Discovery and Invention in the Twentieth Century" by Sir William A. Tilden (Dutton, N.Y.), "Discoveries and Inventions of the Twentieth Century" by Edward Cressy (Dutton), "Industrial Chemistry" by Allen Rogers (Van Nostrand).
"Everyman's Chemistry" by Ellwood Hendrick (Harpers, Modern Science Series) is written in a lively style and assumes no previous knowledge of chemistry from the reader. The chapters on cellulose, gums, sugars and oils are particularly interesting. "Chemistry of Familiar Things" by S.S. Sadtler (Lippincott) is both comprehensive and comprehensible.
The following are intended for young readers but are not to be despised by their elders who may wish to start in on an easy up-grade: "Chemistry of Common Things" (Allyn & Bacon, Boston) is a popular high school text-book but differing from most text-books in being readable and attractive. Its descriptions of industrial processes are brief but clear. The "Achievements of Chemical Science" by James C. Philip (Macmillan) is a handy little book, easy reading for pupils. "Introduction to the Study of Science" by W.P. Smith and E.G. Jewett (Macmillan) touches upon chemical topics in a simple way.
On the history of commerce and the effect of inventions on society the following titles may be suggested: "Outlines of Industrial History" by E. Cressy (Macmillan); "The Origin of Invention," a study of primitive industry, by O.T. Mason (Scribner); "The Romance of Commerce" by Gordon Selbridge (Lane); "Industrial and Commercial Geography" or "Commerce and Industry" by J. Russell Smith (Holt); "Handbook of Commercial Geography" by G.G. Chisholm (Longmans).
The newer theories of chemistry and the constitution of the atom are explained in "The Realities of Modern Science" by John Mills (Macmillan), and "The Electron" by R.A. Millikan (University of Chicago Press), but both require a knowledge of mathematics. The little book on "Matter and Energy" by Frederick Soddy (Holt) is better adapted to the general reader. The most recent text-book is the "Introduction to General Chemistry" by H.N. McCoy and E.M. Terry. (Chicago, 1919.)