PRODUCTS OF THE ELECTRIC FURNACE
The control of man over the materials of nature has been vastly enhanced by the recent extension of the range of temperature at his command. When Fahrenheit stuck the bulb of his thermometer into a mixture of snow and salt he thought he had reached the nadir of temperature, so he scratched a mark on the tube where the mercury stood and called it zero. But we know that absolute zero, the total absence of heat, is 459 of Fahrenheit's degrees lower than his zero point. The modern scientist can get close to that lowest limit by making use of the cooling by the expansion principle. He first liquefies air under pressure and then releasing the pressure allows it to boil off. A tube of hydrogen immersed in the liquid air as it evaporates is cooled down until it can be liquefied. Then the boiling hydrogen is used to liquefy helium, and as this boils off it lowers the temperature to within three or four degrees of absolute zero.
The early metallurgist had no hotter a fire than he could make by blowing charcoal with a bellows. This was barely enough for the smelting of iron. But by the bringing of two carbon rods together, as in the electric arc light, we can get enough heat to volatilize the carbon at the tips, and this means over 7000 degrees Fahrenheit. By putting a pressure of twenty atmospheres onto the arc light we can raise it to perhaps 14,000 degrees, which is 3000 degrees hotter than the sun. This gives the modern man a working range of about 14,500 degrees, so it is no wonder that he can perform miracles.
When a builder wants to make an old house over into a new one he takes it apart brick by brick and stone by stone, then he puts them together in such new fashion as he likes. The electric furnace enables the chemist to take his materials apart in the same way. As the temperature rises the chemical and physical forces that hold a body together gradually weaken. First the solid loosens up and becomes a liquid, then this breaks bonds and becomes a gas. Compounds break up into their elements. The elemental molecules break up into their component atoms and finally these begin to throw off corpuscles of negative electricity eighteen hundred times smaller than the smallest atom. These electrons appear to be the building stones of the universe. No indication of any smaller units has been discovered, although we need not assume that in the electron science has delivered, what has been called, its "ultim-atom." The Greeks called the elemental particles of matter "atoms" because they esteemed them "indivisible," but now in the light of the X-ray we can witness the disintegration of the atom into electrons. All the chemical and physical properties of matter, except perhaps weight, seem to depend upon the number and movement of the negative and positive electrons and by their rearrangement one element may be transformed into another.
So the electric furnace, where the highest attainable temperature is combined with the divisive and directive force of the current, is a magical machine for accomplishment of the metamorphoses desired by the creative chemist. A hundred years ago Davy, by dipping the poles of his battery into melted soda lye, saw forming on one of them a shining globule like quicksilver. It was the metal sodium, never before seen by man. Nowadays this process of electrolysis (electric loosening) is carried out daily by the ton at Niagara.
The reverse process, electro-synthesis (electric combining), is equally simple and even more important. By passing a strong electric current through a mixture of lime and coke the metal calcium disengages itself from the oxygen of the lime and attaches itself to the carbon. Or, to put it briefly,
CaO + 3C → CaC2 + CO
lime coke calcium carbon
carbide monoxide
This reaction is of peculiar importance because it bridges the gulf between the organic and inorganic worlds. It was formerly supposed that the substances found in plants and animals, mostly complex compounds of carbon, hydrogen and oxygen, could only be produced by "vital forces." If this were true it meant that chemistry was limited to the mineral kingdom and to the extraction of such carbon compounds as happened to exist ready formed in the vegetable and animal kingdoms. But fortunately this barrier to human achievement proved purely illusory. The organic field, once man had broken into it, proved easier to work in than the inorganic.
But it must be confessed that man is dreadfully clumsy about it yet. He takes a thousand horsepower engine and an electric furnace at several thousand degrees to get carbon into combination with hydrogen while the little green leaf in the sunshine does it quietly without getting hot about it. Evidently man is working as wastefully as when he used a thousand slaves to drag a stone to the pyramid or burned down a house to roast a pig. Not until his laboratory is as cool and calm and comfortable as the forest and the field can the chemist call himself completely successful.
But in spite of his clumsiness the chemist is actually making things that he wants and cannot get elsewhere. The calcium carbide that he manufactures from inorganic material serves as the raw material for producing all sorts of organic compounds. The electric furnace was first employed on a large scale by the Cowles Electric Smelting and Aluminum Company at Cleveland in 1885. On the dump were found certain lumps of porous gray stone which, dropped into water, gave off a gas that exploded at touch of a match with a splendid bang and flare. This gas was acetylene, and we can represent the reaction thus:
CaC2 + 2 H2O → C2H2 + CaO2H2
calcium carbide added to water gives acetylene and slaked lime
We are all familiar with this reaction now, for it is acetylene that gives the dazzling light of the automobiles and of the automatic signal buoys of the seacoast. When burned with pure oxygen instead of air it gives the hottest of chemical flames, hotter even than the oxy-hydrogen blowpipe. For although a given weight of hydrogen will give off more heat when it burns than carbon will, yet acetylene will give off more heat than either of its elements or both of them when they are separate. This is because acetylene has stored up heat in its formation instead of giving it off as in most reactions, or to put it in chemical language, acetylene is an endothermic compound. It has required energy to bring the H and the C together, therefore it does not require energy to separate them, but, on the contrary, energy is released when they are separated. That is to say, acetylene is explosive not only when mixed with air as coal gas is but by itself. Under a suitable impulse acetylene will break up into its original carbon and hydrogen with great violence. It explodes with twice as much force without air as ordinary coal gas with air. It forms an explosive compound with copper, so it has to be kept out of contact with brass tubes and stopcocks. But compressed in steel cylinders and dissolved in acetone, it is safe and commonly used for welding and melting. It is a marvelous though not an unusual sight on city streets to see a man with blue glasses on cutting down through a steel rail with an oxy-acetylene blowpipe as easily as a carpenter saws off a board. With such a flame he can carve out a pattern in a steel plate in a way that reminds me of the days when I used to make brackets with a scroll saw out of cigar boxes. The torch will travel through a steel plate an inch or two thick at a rate of six to ten inches a minute.
Courtesy of the Carborundum Company, Niagara Falls
MAKING ALOXITE IN THE ELECTRIC FURNACES BY FUSING COKE AND BAUXITE
In the background are the circular furnaces. In the foreground are the fused masses of the product
Courtesy of the Carborundum Co., Niagara Falls A BLOCK OF CARBORUNDUM CRYSTALS
Courtesy of the Carborundum Co., Niagara Falls
MAKING CARBORUNDUM IN THE ELECTRIC FURNACE
At the end may be seen the attachments for the wires carrying the electric current and on the side the flames from the burning carbon.
The temperatures attainable with various fuels in the compound blowpipe are said to be:
| Acetylene with oxygen | 7878° F. |
| Hydrogen with oxygen | 6785° F. |
| Coal gas with oxygen | 6575° F. |
| Gasoline with oxygen | 5788° F. |
If we compare the formula of acetylene, C2H2 with that of ethylene, C2H4, or with ethane, C2H6, we see that acetylene could take on two or four more atoms. It is evidently what the chemists call an "unsaturated" compound, one that has not reached its limit of hydrogenation. It is therefore a very active and energetic compound, ready to pick up on the slightest instigation hydrogen or oxygen or chlorine or any other elements that happen to be handy. This is why it is so useful as a starting point for synthetic chemistry.
To build up from this simple substance, acetylene, the higher compounds of carbon and oxygen it is necessary to call in the aid of that mysterious agency, the catalyst. Acetylene is not always acted upon by water, as we know, for we see it bubbling up through the water when prepared from the carbide. But if to the water be added a little acid and a mercury salt, the acetylene gas will unite with the water forming a new compound, acetaldehyde. We can show the change most simply in this fashion:
C2H2 + H2O → C2H4O
acetylene added to water forms acetaldehyde
Acetaldehyde is not of much importance in itself, but is useful as a transition. If its vapor mixed with hydrogen is passed over finely divided nickel, serving as a catalyst, the two unite and we have alcohol, according to this reaction:
C2H4O + H2 → C2H6O
acetaldehyde added to hydrogen forms alcohol
Alcohol we are all familiar with—some of us too familiar, but the prohibition laws will correct that. The point to be noted is that the alcohol we have made from such unpromising materials as limestone and coal is exactly the same alcohol as is obtained by the fermentation of fruits and grains by the yeast plant as in wine and beer. It is not a substitute or imitation. It is not the wood spirits (methyl alcohol, CH4O), produced by the destructive distillation of wood, equally serviceable as a solvent or fuel, but undrinkable and poisonous.
Now, as we all know, cider and wine when exposed to the air gradually turn into vinegar, that is, by the growth of bacteria the alcohol is oxidized to acetic acid. We can, if we like, dispense with the bacteria and speed up the process by employing a catalyst. Acetaldehyde, which is halfway between alcohol and acid, may also be easily oxidized to acetic acid. The relationship is readily seen by this:
C{2}H6O → CC2H4O → C2H4O3
alcohol acetaldehyde acetic acid
Acetic acid, familiar to us in a diluted and flavored form as vinegar, is when concentrated of great value in industry, especially as a solvent. I have already referred to its use in combination with cellulose as a "dope" for varnishing airplane canvas or making non-inflammable film for motion pictures. Its combination with lime, calcium acetate, when heated gives acetone, which, as may be seen from its formula (C3H6O) is closely related to the other compounds we have been considering, but it is neither an alcohol nor an acid. It is extensively employed as a solvent.
Acetone is not only useful for dissolving solids but it will under pressure dissolve many times its volume of gaseous acetylene. This is a convenient way of transporting and handling acetylene for lighting or welding.
If instead of simply mixing the acetone and acetylene in a solution we combine them chemically we can get isoprene, which is the mother substance of ordinary India rubber. From acetone also is made the "war rubber" of the Germans (methyl rubber), which I have mentioned in a previous chapter. The Germans had been getting about half their supply of acetone from American acetate of lime and this was of course shut off. That which was produced in Germany by the distillation of beech wood was not even enough for the high explosives needed at the front. So the Germans resorted to rotting potatoes—or rather let us say, since it sounds better—to the cultivation of Bacillus macerans. This particular bacillus converts the starch of the potato into two-thirds alcohol and one-third acetone. But soon potatoes got too scarce to be used up in this fashion, so the Germans turned to calcium carbide as a source of acetone and before the war ended they had a factory capable of manufacturing 2000 tons of methyl rubber a year. This shows the advantage of having several strings to a bow.
The reason why acetylene is such an active and acquisitive thing the chemist explains, or rather expresses, by picturing its structure in this shape:
H-C≡C-H
Now the carbon atoms are holding each other's hands because they have nothing else to do. There are no other elements around to hitch on to. But the two carbons of acetylene readily loosen up and keeping the connection between them by a single bond reach out in this fashion with their two disengaged arms and grab whatever alien atoms happen to be in the vicinity:
| |
H-C-C-H
| |
Carbon atoms belong to the quadrumani like the monkeys, so they are peculiarly fitted to forming chains and rings. This accounts for the variety and complexity of the carbon compounds.
So when acetylene gas mixed with other gases is passed over a catalyst, such as a heated mass of iron ore or clay (hydrates or silicates of iron or aluminum), it forms all sorts of curious combinations. In the presence of steam we may get such simple compounds as acetic acid, acetone and the like. But when three acetylene molecules join to form a ring of six carbon atoms we get compounds of the benzene series such as were described in the chapter on the coal-tar colors. If ammonia is mixed with acetylene we may get rings with the nitrogen atom in place of one of the carbons, like the pyridins and quinolins, pungent bases such as are found in opium and tobacco. Or if hydrogen sulfide is mixed with the acetylene we may get thiophenes, which have sulfur in the ring. So, starting with the simple combination of two atoms of carbon with two of hydrogen, we can get directly by this single process some of the most complicated compounds of the organic world, as well as many others not found in nature.
In the development of the electric furnace America played a pioneer part. Provost Smith of the University of Pennsylvania, who is the best authority on the history of chemistry in America, claims for Robert Hare, a Philadelphia chemist born in 1781, the honor of constructing the first electrical furnace. With this crude apparatus and with no greater electromotive force than could be attained from a voltaic pile, he converted charcoal into graphite, volatilized phosphorus from its compounds, isolated metallic calcium and synthesized calcium carbide. It is to Hare also that we owe the invention in 1801 of the oxy-hydrogen blowpipe, which nowadays is used with acetylene as well as hydrogen. With this instrument he was able to fuse strontia and volatilize platinum.
But the electrical furnace could not be used on a commercial scale until the dynamo replaced the battery as a source of electricity. The industrial development of the electrical furnace centered about the search for a cheap method of preparing aluminum. This is the metallic base of clay and therefore is common enough. But clay, as we know from its use in making porcelain, is very infusible and difficult to decompose. Sixty years ago aluminum was priced at $140 a pound, but one would have had difficulty in buying such a large quantity as a pound at any price. At international expositions a small bar of it might be seen in a case labeled "silver from clay." Mechanics were anxious to get the new metal, for it was light and untarnishable, but the metallurgists could not furnish it to them at a low enough price. In order to extract it from clay a more active metal, sodium, was essential. But sodium also was rare and expensive. In those days a professor of chemistry used to keep a little stick of it in a bottle under kerosene and once a year he whittled off a piece the size of a pea and threw it into water to show the class how it sizzled and gave off hydrogen. The way to get cheaper aluminum was, it seemed, to get cheaper sodium and Hamilton Young Castner set himself at this problem. He was a Brooklyn boy, a student of Chandler's at Columbia. You can see the bronze tablet in his honor at the entrance of Havemeyer Hall. In 1886 he produced metallic sodium by mixing caustic soda with iron and charcoal in an iron pot and heating in a gas furnace. Before this experiment sodium sold at $2 a pound; after it sodium sold at twenty cents a pound.
But although Castner had succeeded in his experiment he was defeated in his object. For while he was perfecting the sodium process for making aluminum the electrolytic process for getting aluminum directly was discovered in Oberlin. So the $250,000 plant of the "Aluminium Company Ltd." that Castner had got erected at Birmingham, England, did not make aluminum at all, but produced sodium for other purposes instead. Castner then turned his attention to the electrolytic method of producing sodium by the use of the power of Niagara Falls, electric power. Here in 1894 he succeeded in separating common salt into its component elements, chlorine and sodium, by passing the electric current through brine and collecting the sodium in the mercury floor of the cell. The sodium by the action of water goes into caustic soda. Nowadays sodium and chlorine and their components are made in enormous quantities by the decomposition of salt. The United States Government in 1918 procured nearly 4,000,000 pounds of chlorine for gas warfare.
The discovery of the electrical process of making aluminum that displaced the sodium method was due to Charles M. Hall. He was the son of a Congregational minister and as a boy took a fancy to chemistry through happening upon an old text-book of that science in his father's library. He never knew who the author was, for the cover and title page had been torn off. The obstacle in the way of the electrolytic production of aluminum was, as I have said, because its compounds were so hard to melt that the current could not pass through. In 1886, when Hall was twenty-two, he solved the problem in the laboratory of Oberlin College with no other apparatus than a small crucible, a gasoline burner to heat it with and a galvanic battery to supply the electricity. He found that a Greenland mineral, known as cryolite (a double fluoride of sodium and aluminum), was readily fused and would dissolve alumina (aluminum oxide). When an electric current was passed through the melted mass the metal aluminum would collect at one of the poles.
In working out the process and defending his claims Hall used up all his own money, his brother's and his uncle's, but he won out in the end and Judge Taft held that his patent had priority over the French claim of Hérault. On his death, a few years ago, Hall left his large fortune to his Alma Mater, Oberlin.
Two other young men from Ohio, Alfred and Eugene Cowles, with whom Hall was for a time associated, wore the first to develop the wide possibilities of the electric furnace on a commercial scale. In 1885 they started the Cowles Electric Smelting and Aluminum Company at Lockport, New York, using Niagara power. The various aluminum bronzes made by absorbing the electrolyzed aluminum in copper attracted immediate attention by their beauty and usefulness in electrical work and later the company turned out other products besides aluminum, such as calcium carbide, phosphorus, and carborundum. They got carborundum as early as 1885 but miscalled it "crystallized silicon," so its introduction was left to E.A. Acheson, who was a graduate of Edison's laboratory. In 1891 he packed clay and charcoal into an iron bowl, connected it to a dynamo and stuck into the mixture an electric light carbon connected to the other pole of the dynamo. When he pulled out the rod he found its end encrusted with glittering crystals of an unknown substance. They were blue and black and iridescent, exceedingly hard and very beautiful. He sold them at first by the carat at a rate that would amount to $560 a pound. They were as well worth buying as diamond dust, but those who purchased them must have regretted it, for much finer crystals were soon on sale at ten cents a pound. The mysterious substance turned out to be a compound of carbon and silicon, the simplest possible compound, one atom of each, CSi. Acheson set up a factory at Niagara, where he made it in ten-ton batches. The furnace consisted simply of a brick box fifteen feet long and seven feet wide and deep, with big carbon electrodes at the ends. Between them was packed a mixture of coke to supply the carbon, sand to supply the silicon, sawdust to make the mass porous and salt to make it fusible.
The first American electric furnace, constructed by Robert Hare of Philadelphia. From "Chemistry in America," by Edgar Fahs Smith
The substance thus produced at Niagara Falls is known as "carborundum" south of the American-Canadian boundary and as "crystolon" north of this line, as "carbolon" by another firm, and as "silicon carbide" by chemists the world over. Since it is next to the diamond in hardness it takes off metal faster than emery (aluminum oxide), using less power and wasting less heat in futile fireworks. It is used for grindstones of all sizes, including those the dentist uses on your teeth. It has revolutionized shop-practice, for articles can be ground into shape better and quicker than they can be cut. What is more, the artificial abrasives do not injure the lungs of the operatives like sandstone. The output of artificial abrasives in the United States and Canada for 1917 was:
| Tons | Value | |
| Silicon carbide | 8,323 | $1,074,152 |
| Aluminum oxide | 48,463 | 6,969,387 |
A new use for carborundum was found during the war when Uncle Sam assumed the rôle of Jove as "cloud-compeller." Acting on carborundum with chlorine—also, you remember, a product of electrical dissolution—the chlorine displaces the carbon, forming silicon tetra-chloride (SiCl4), a colorless liquid resembling chloroform. When this comes in contact with moist air it gives off thick, white fumes, for water decomposes it, giving a white powder (silicon hydroxide) and hydrochloric acid. If ammonia is present the acid will unite with it, giving further white fumes of the salt, ammonium chloride. So a mixture of two parts of silicon chloride with one part of dry ammonia was used in the war to produce smoke-screens for the concealment of the movements of troops, batteries and vessels or put in shells so the outlook could see where they burst and so get the range. Titanium tetra-chloride, a similar substance, proved 50 per cent. better than silicon, but phosphorus—which also we get from the electric furnace—was the most effective mistifier of all.
Before the introduction of the artificial abrasives fine grinding was mostly done by emery, which is an impure form of aluminum oxide found in nature. A purer form is made from the mineral bauxite by driving off its combined water. Bauxite is the ore from which is made the pure aluminum oxide used in the electric furnace for the production of metallic aluminum. Formerly we imported a large part of our bauxite from France, but when the war shut off this source we developed our domestic fields in Arkansas, Alabama and Georgia, and these are now producing half a million tons a year. Bauxite simply fused in the electric furnace makes a better abrasive than the natural emery or corundum, and it is sold for this purpose under the name of "aloxite," "alundum," "exolon," "lionite" or "coralox." When the fused bauxite is worked up with a bonding material into crucibles or muffles and baked in a kiln it forms the alundum refractory ware. Since alundum is porous and not attacked by acids it is used for filtering hot and corrosive liquids that would eat up filter-paper. Carborundum or crystolon is also made up into refractory ware for high temperature work. When the fused mass of the carborundum furnace is broken up there is found surrounding the carborundum core a similar substance though not quite so hard and infusible, known as "carborundum sand" or "siloxicon." This is mixed with fireclay and used for furnace linings.
Many new forms of refractories have come into use to meet the demands of the new high temperature work. The essentials are that it should not melt or crumble at high heat and should not expand and contract greatly under changes of temperature (low coefficient of thermal expansion). Whether it is desirable that it should heat through readily or slowly (coefficient of thermal conductivity) depends on whether it is wanted as a crucible or as a furnace lining. Lime (calcium oxide) fuses only at the highest heat of the electric furnace, but it breaks down into dust. Magnesia (magnesium oxide) is better and is most extensively employed. For every ton of steel produced five pounds of magnesite is needed. Formerly we imported 90 per cent. of our supply from Austria, but now we get it from California and Washington. In 1913 the American production of magnesite was only 9600 tons. In 1918 it was 225,000. Zirconia (zirconium oxide) is still more refractory and in spite of its greater cost zirkite is coming into use as a lining for electric furnaces.
Silicon is next to oxygen the commonest element in the world. It forms a quarter of the earth's crust, yet it is unfamiliar to most of us. That is because it is always found combined with oxygen in the form of silica as quartz crystal or sand. This used to be considered too refractory to be blown but is found to be easily manipulable at the high temperatures now at the command of the glass-blower. So the chemist rejoices in flasks that he can heat red hot in the Bunsen burner and then plunge into ice water without breaking, and the cook can bake and serve in a dish of "pyrex," which is 80 per cent. silica.
At the beginning of the twentieth century minute specimens of silicon were sold as laboratory curiosities at the price of $100 an ounce. Two years later it was turned out by the barrelful at Niagara as an accidental by-product and could not find a market at ten cents a pound. Silicon from the electric furnace appears in the form of hard, glittering metallic crystals.
An alloy of iron and silicon, ferro-silicon, made by heating a mixture of iron ore, sand and coke in the electrical furnace, is used as a deoxidizing agent in the manufacture of steel.
Since silicon has been robbed with difficulty of its oxygen it takes it on again with great avidity. This has been made use of in the making of hydrogen. A mixture of silicon (or of the ferro-silicon alloy containing 90 per cent. of silicon) with soda and slaked lime is inert, compact and can be transported to any point where hydrogen is needed, say at a battle front. Then the "hydrogenite," as the mixture is named, is ignited by a hot iron ball and goes off like thermit with the production of great heat and the evolution of a vast volume of hydrogen gas. Or the ferro-silicon may be simply burned in an atmosphere of steam in a closed tank after ignition with a pinch of gunpowder. The iron and the silicon revert to their oxides while the hydrogen of the water is set free. The French "silikol" method consists in treating silicon with a 40 per cent. solution of soda.
Another source of hydrogen originating with the electric furnace is "hydrolith," which consists of calcium hydride. Metallic calcium is prepared from lime in the electric furnace. Then pieces of the calcium are spread out in an oven heated by electricity and a current of dry hydrogen passed through. The gas is absorbed by the metal, forming the hydride (CaH2). This is packed up in cans and when hydrogen is desired it is simply dropped into water, when it gives off the gas just as calcium carbide gives off acetylene.
This last reaction was also used in Germany for filling Zeppelins. For calcium carbide is convenient and portable and acetylene, when it is once started, as by an electric shock, decomposes spontaneously by its own internal heat into hydrogen and carbon. The latter is left as a fine, pure lampblack, suitable for printer's ink.
Napoleon, who was always on the lookout for new inventions that could be utilized for military purposes, seized immediately upon the balloon as an observation station. Within a few years after the first ascent had been made in Paris Napoleon took balloons and apparatus for generating hydrogen with him on his "archeological expedition" to Egypt in which he hoped to conquer Asia. But the British fleet in the Mediterranean put a stop to this experiment by intercepting the ship, and military aviation waited until the Great War for its full development. This caused a sudden demand for immense quantities of hydrogen and all manner of means was taken to get it. Water is easily decomposed into hydrogen and oxygen by passing an electric current through it. In various electrolytical processes hydrogen has been a wasted by-product since the balloon demand was slight and it was more bother than it was worth to collect and purify the hydrogen. Another way of getting hydrogen in quantity is by passing steam over red-hot coke. This produces the blue water-gas, which contains about 50 per cent. hydrogen, 40 per cent. carbon monoxide and the rest nitrogen and carbon dioxide. The last is removed by running the mixed gases through lime. Then the nitrogen and carbon monoxide are frozen out in an air-liquefying apparatus and the hydrogen escapes to the storage tank. The liquefied carbon monoxide, allowed to regain its gaseous form, is used in an internal combustion engine to run the plant.
There are then many ways of producing hydrogen, but it is so light and bulky that it is difficult to get it where it is wanted. The American Government in the war made use of steel cylinders each holding 161 cubic feet of the gas under a pressure of 2000 pounds per square inch. Even the hydrogen used by the troops in France was shipped from America in this form. For field use the ferro-silicon and soda process was adopted. A portable generator of this type was capable of producing 10,000 cubic feet of the gas per hour.
The discovery by a Kansas chemist of natural sources of helium may make it possible to free ballooning of its great danger, for helium is non-inflammable and almost as light as hydrogen.
Other uses of hydrogen besides ballooning have already been referred to in other chapters. It is combined with nitrogen to form synthetic ammonia. It is combined with oxygen in the oxy-hydrogen blowpipe to produce heat. It is combined with vegetable and animal oils to convert them into solid fats. There is also the possibility of using it as a fuel in the internal combustion engine in place of gasoline, but for this purpose we must find some way of getting hydrogen portable or producible in a compact form.
Aluminum, like silicon, sodium and calcium, has been rescued by violence from its attachment to oxygen and like these metals it reverts with readiness to its former affinity. Dr. Goldschmidt made use of this reaction in his thermit process. Powdered aluminum is mixed with iron oxide (rust). If the mixture is heated at any point a furious struggle takes place throughout the whole mass between the iron and the aluminum as to which metal shall get the oxygen, and the aluminum always comes out ahead. The temperature runs up to some 6000 degrees Fahrenheit within thirty seconds and the freed iron, completely liquefied, runs down into the bottom of the crucible, where it may be drawn off by opening a trap door. The newly formed aluminum oxide (alumina) floats as slag on top. The applications of the thermit process are innumerable. If, for instance, it is desired to mend a broken rail or crank shaft without moving it from its place, the two ends are brought together or fixed at the proper distance apart. A crucible filled with the thermit mixture is set up above the joint and the thermit ignited with a priming of aluminum and barium peroxide to start it off. The barium peroxide having a superabundance of oxygen gives it up readily and the aluminum thus encouraged attacks the iron oxide and robs it of its oxygen. As soon as the iron is melted it is run off through the bottom of the crucible and fills the space between the rail ends, being kept from spreading by a mold of refractory material such as magnesite. The two ends of the rail are therefore joined by a section of the same size, shape, substance and strength as themselves. The same process can be used for mending a fracture or supplying a missing fragment of a steel casting of any size, such as a ship's propeller or a cogwheel.
TYPES OF GAS MASK USED BY AMERICA, THE ALLIES, AND GERMANY DURING THE WAR
In the top row are the American masks, chronologically, from left to right: U.S. Navy mask (obsolete), U.S. Navy mask (final type), U.S. Army box respirator (used throughout the war), U.S.R.F.K. respirator, U.S.A.T. respirator (an all-rubber mask), U.S.K.T. respirator (a sewed fabric mask), and U.S. "Model 1919," ready for production when the armistice was signed. In the middle row, left to right, are: British veil (the original emergency mask used in April, 1915), British P.H. helmet (the next emergency mask), British box respirator (standard British army type), French M2 mask (original type), French Tissot artillery mask, and French A.R.S. mask (latest type). In the front row: the latest German mask, the Russian mask, Italian mask, British motor corps mask, U.S. rear area emergency respirator, and U.S. Connell mask
PUMPING MELTED WHITE PHOSPHORUS INTO HAND GRENADES FILLED WITH WATER—EDGEWOOD ARSENAL
FILLING SHELL WITH "MUSTARD GAS"
Empty shells are being placed on small trucks to be run into the filling chamber. The large truck in the foreground contains loaded shell
For smaller work thermit has two rivals, the oxy-acetylene torch and electric welding. The former has been described and the latter is rather out of the range of this volume, although I may mention that in the latter part of 1918 there was launched from a British shipyard the first rivotless steel vessel. In this the steel plates forming the shell, bulkheads and floors are welded instead of being fastened together by rivets. There are three methods of doing this depending upon the thickness of the plates and the sort of strain they are subject to. The plates may be overlapped and tacked together at intervals by pressing the two electrodes on opposite sides of the same point until the spot is sufficiently heated to fuse together the plates here. Or roller electrodes may be drawn slowly along the line of the desired weld, fusing the plates together continuously as they go. Or, thirdly, the plates may be butt-welded by being pushed together edge to edge without overlapping and the electric current being passed from one plate to the other heats up the joint where the conductivity is interrupted.
It will be observed that the thermit process is essentially like the ordinary blast furnace process of smelting iron and other metals except that aluminum is used instead of carbon to take the oxygen away from the metal in the ore. This has an advantage in case carbon-free metals are desired and the process is used for producing manganese, tungsten, titanium, molybdenum, vanadium and their allows with iron and copper.
During the war thermit found a new and terrible employment, as it was used by the airmen for setting buildings on fire and exploding ammunition dumps. The German incendiary bombs consisted of a perforated steel nose-piece, a tail to keep it falling straight and a cylindrical body which contained a tube of thermit packed around with mineral wax containing potassium perchlorate. The fuse was ignited as the missile was released and the thermit, as it heated up, melted the wax and allowed it to flow out together with the liquid iron through the holes in the nose-piece. The American incendiary bombs were of a still more malignant type. They weighed about forty pounds apiece and were charged with oil emulsion, thermit and metallic sodium. Sodium decomposes water so that if any attempt were made to put out with a hose a fire started by one of these bombs the stream of water would be instantaneously changed into a jet of blazing hydrogen.
Besides its use in combining and separating different elements the electric furnace is able to change a single element into its various forms. Carbon, for instance, is found in three very distinct forms: in hard, transparent and colorless crystals as the diamond, in black, opaque, metallic scales as graphite, and in shapeless masses and powder as charcoal, coke, lampblack, and the like. In the intense heat of the electric arc these forms are convertible one into the other according to the conditions. Since the third form is the cheapest the object is to change it into one of the other two. Graphite, plumbago or "blacklead," as it is still sometimes called, is not found in many places and more rarely found pure. The supply was not equal to the demand until Acheson worked out the process of making it by packing powdered anthracite between the electrodes of his furnace. In this way graphite can be cheaply produced in any desired quantity and quality.
Since graphite is infusible and incombustible except at exceedingly high temperatures, it is extensively used for crucibles and electrodes. These electrodes are made in all sizes for the various forms of electric lamps and furnaces from rods one-sixteenth of an inch in diameter to bars a foot thick and six feet long. It is graphite mixed with fine clay to give it the desired degree of hardness that forms the filling of our "lead" pencils. Finely ground and flocculent graphite treated with tannin may be held in suspension in liquids and even pass through filter-paper. The mixture with water is sold under the name of "aquadag," with oil as "oildag" and with grease as "gredag," for lubrication. The smooth, slippery scales of graphite in suspension slide over each other easily and keep the bearings from rubbing against each other.
The other and more difficult metamorphosis of carbon, the transformation of charcoal into diamond, was successfully accomplished by Moissan in 1894. Henri Moissan was a toxicologist, that is to say, a Professor of Poisoning, in the Paris School of Pharmacy, who took to experimenting with the electric furnace in his leisure hours and did more to demonstrate its possibilities than any other man. With it he isolated fluorine, most active of the elements, and he prepared for the first time in their purity many of the rare metals that have since found industrial employment. He also made the carbides of the various metals, including the now common calcium carbide. Among the problems that he undertook and solved was the manufacture of artificial diamonds. He first made pure charcoal by burning sugar. This was packed with iron in the hollow of a block of lime into which extended from opposite sides the carbon rods connected to the dynamo. When the iron had melted and dissolved all the carbon it could, Moissan dumped it into water or better into melted lead or into a hole in a copper block, for this cooled it most rapidly. After a crust was formed it was left to solidify slowly. The sudden cooling of the iron on the outside subjected the carbon, which was held in solution, to intense pressure and when the bit of iron was dissolved in acid some of the carbon was found to be crystallized as diamond, although most of it was graphite. To be sure, the diamonds were hardly big enough to be seen with the naked eye, but since Moissan's aim was to make diamonds, not big diamonds, he ceased his efforts at this point.
To produce large diamonds the carbon would have to be liquefied in considerable quantity and kept in that state while it slowly crystallized. But that could only be accomplished at a temperature and pressure and duration unattainable as yet. Under ordinary atmospheric pressure carbon passes over from the solid to the gaseous phase without passing through the liquid, just as snow on a cold, clear day will evaporate without melting.
Probably some one in the future will take up the problem where Moissan dropped it and find out how to make diamonds of any size. But it is not a question that greatly interests either the scientist or the industrialist because there is not much to be learned from it and not much to be made out of it. If the inventor of a process for making cheap diamonds could keep his electric furnace secretly in his cellar and market his diamonds cautiously he might get rich out of it, but he would not dare to turn out very large stones or too many of them, for if a suspicion got around that he was making them the price would fall to almost nothing even if he did sell another one. For the high price of the diamond is purely fictitious. It is in the first place kept up by limiting the output of the natural stone by the combination of dealers and, further, the diamond is valued not for its usefulness or beauty but by its real or supposed rarity. Chesterton says: "All is gold that glitters, for the glitter is the gold." This is not so true of gold, for if gold were as cheap as nickel it would be very valuable, since we should gold-plate our machinery, our ships, our bridges and our roofs. But if diamonds were cheap they would be good for nothing except grindstones and drills. An imitation diamond made of heavy glass (paste) cannot be distinguished from the genuine gem except by an expert. It sparkles about as brilliantly, for its refractive index is nearly as high. The reason why it is not priced so highly is because the natural stone has presumably been obtained through the toil and sweat of hundreds of negroes searching in the blue ground of the Transvaal for many months. It is valued exclusively by its cost. To wear a diamond necklace is the same as hanging a certified check for $100,000 by a string around the neck.
Real values are enhanced by reduction in the cost of the price of production. Fictitious values are destroyed by it. Aluminum at twenty-five cents a pound is immensely more valuable to the world than when it is a curiosity in the chemist's cabinet and priced at $160 a pound.
So the scope of the electric furnace reaches from the costly but comparatively valueless diamond to the cheap but indispensable steel. As F.J. Tone says, if the automobile manufacturers were deprived of Niagara products, the abrasives, aluminum, acetylene for welding and high-speed tool steel, a factory now turning out five hundred cars a day would be reduced to one hundred. I have here been chiefly concerned with electricity as effecting chemical changes in combining or separating elements, but I must not omit to mention its rapidly extending use as a source of heat, as in the production and casting of steel. In 1908 there were only fifty-five tons of steel produced by the electric furnace in the United States, but by 1918 this had risen to 511,364 tons. And besides ordinary steel the electric furnace has given us alloys of iron with the once "rare metals" that have created a new science of metallurgy.