Boys' Second Book of Inventions

On reaching Niagara Falls, I called on Mr. E. G. Acheson, whose name stands with that of Moissan as a pioneer in the investigation of high temperatures. Mr. Acheson is still a young man – not more than forty-five at most – and clean-cut, clear-eyed, and genial, with something of the studious air of a college professor. He is pre-eminently a self-made man. At twenty-four he found a place in Edison's laboratory – "Edison's college of inventions," he calls it – and, at twenty-five, he was one of the seven pioneers in electricity who (in 1881-82) introduced the incandescent lamp in Europe. He installed the first electric-light plants in the cities of Milan, Genoa, Venice, and Amsterdam, and during this time was one of Edison's representatives in Paris.

"I think the possibility of manufacturing genuine diamonds," he said to me, "has dazzled more than one young experimenter. My first efforts in this direction were made in 1880. It was before we had command of the tremendous electric energy now furnished by the modern dynamo, and when the highest heat attainable for practical purposes was obtained by the oxy-hydrogen flame. Even this was at the service of only a few experimenters, and certainly not at mine. My first experiments were made in what I might term the 'wet way'; that is, by the process of chemical decomposition by means of an electric current. Very interesting results were obtained, which even now give promise of value; but the diamond did not materialise.

"I did not take up the subject again until the dynamo had attained high perfection and I was able to procure currents of great power. Calling in the aid of the 6,500 degrees Fahrenheit or more of temperature produced by these electric currents, I once more set myself to the solution of the problem. I now had, however, two distinct objects in view: first, the making of a diamond; and, second, the production of a hard substance for abrasive purposes. My experiments in 1880 had resulted in producing a substance of extreme hardness, hard enough, indeed, to scratch the sapphire – the next hardest thing to the diamond – and I saw that such a material, cheaply made, would have great value.

"My first experiment in this new series was of a kind that would have been denounced as absurd by any of the old-school book-chemists, and had I had a similar training, the probability is that I should not have made such an investigation. But 'fools rush in where angels fear to tread,' and the experiment was made."

This experiment by Mr. Acheson, extremely simple in execution, was the first act in rolling the stone from the entrance to a veritable Aladdin's cave, into which a multitude of experimenters have passed in their search for nature's secrets; for, while the use of the electrical furnace in the reduction of metals – in the breaking down of nature's compounds – was not new, its use for synthetic chemistry – for the putting together, the building up, the formation of compounds – was entirely new. It has enabled the chemist not only to reproduce the compounds of nature, but to go further and produce valuable compounds that are wholly new and were heretofore unknown to man. Mr. Acheson conjectured that carbon, if made to combine with clay, would produce an extremely hard substance; and that, having been combined with the clay, if it should in the cooling separate again from the clay, it would issue out of the operation as diamond. He therefore mixed a little clay and coke dust together, placed them in a crucible, inserted the ends of two electric-light carbons into the mixture, and connected the carbons with a dynamo. The fierce heat generated at the points of the carbons fused the clay, and caused portions of the carbon to dissolve. After cooling, a careful examination was made of the mass, and a few small purple crystals were found. They sparkled with something of the brightness of diamonds, and were so hard that they scratched glass. Mr. Acheson decided at once that they could not be diamonds; but he thought they might be rubies or sapphires. A little later, though, when he had made similar crystals of a larger size, he found that they were harder than rubies, even scratching the diamond itself. He showed them to a number of expert jewellers, chemists, and geologists. They had so much the appearance of natural gems that many experts to whom they were submitted without explanation decided that they must certainly be of natural production. Even so eminent an authority as Geikie, the Scotch geologist, on being told, after he had examined them, that the crystals were manufactured in America, responded testily: "These Americans! What won't they claim next? Why, man, those crystals have been in the earth a million years."

Mr. Acheson decided at first that his crystals were a combination of carbon and aluminium, and gave them the name carborundum. He at once set to work to manufacture them in large quantities for use in making abrasive wheels, whetstones, and sandpaper, and for other purposes for which emery and corundum were formerly used. He soon found by chemical analysis, however, that carborundum was not composed of carbon and aluminium, but of carbon and silica, or sand, and that he had, in fact, created a new substance; so far as human knowledge now extends, no such combination occurs anywhere in nature. And it was made possible only by the electrical furnace, with its power of producing heat of untold intensity.

In order to get a clear understanding of the actual workings of the electrical furnace, I visited the plant where Mr. Acheson makes carborundum. The furnace-room is a great, dingy brick building, open at the sides like a shed. It is located only a few hundred yards from the banks of the Niagara River and well within the sound of the great falls. Just below it, and nearer the city, stands the handsome building of the Power Company, in which the mightiest dynamos in the world whir ceaselessly, day and night, while the waters of Niagara churn in the water-wheel pits below. Heavy copper wires carrying a current of 2,200 volts lead from the power-house to Mr. Acheson's furnaces, where the electrical energy is transformed into heat.

There are ten furnaces in all, built loosely of fire-brick, and fitted at each end with electrical connections. And strange they look to one who is familiar with the ordinary fuel furnace, for they have no chimneys, no doors, no drafts, no ash-pits, no blinding glow of heat and light. The room in which they stand is comfortably cool. Each time a furnace is charged it is built up anew; for the heat produced is so fierce that it frequently melts the bricks together, and new ones must be supplied. There were furnaces in many stages of development. One had been in full blast for nearly thirty hours, and a weird sight it was. The top gave one the instant impression of the seamy side of a volcano. The heaped coke was cracked in every direction, and from out of the crevices and depressions and from between the joints of the loosely built brick walls gushed flames of pale green and blue, rising upward, and burning now high, now low, but without noise beyond a certain low humming. Within the furnace – which was oblong in shape, about the height of a man, and sixteen feet long by six wide – there was a channel, or core, of white-hot carbon in a nearly vaporised state. It represented graphically in its seething activity what the burning surface of the sun might be – and it was almost as hot. Yet the heat was scarcely manifest a dozen feet from the furnace, and but for the blue flames rising from the cracks in the envelope, or wall, one might have laid his hand almost anywhere on the bricks without danger of burning it.

In the best modern blast-furnaces, in which the coal is supplied with special artificial draft to make it burn the more fiercely, the heat may reach 3,000 degrees Fahrenheit. This is less than half of that produced in the electrical furnace. In porcelain kilns, the potters, after hours of firing, have been able to produce a cumulative temperature of as much as 3,300 degrees Fahrenheit; and this, with the oxy-hydrogen flame (in which hydrogen gas is spurred to greater heat by an excess of oxygen), is the very extreme of heat obtainable by any artificial means except by the electrical furnace. Thus the electrical furnace has fully doubled the practical possibilities in the artificial production of heat.

Mr. Fitzgerald, the chemist of the Acheson Company, pointed out to me a curious glassy cavity in one of the half-dismantled furnaces. "Here the heat was only a fraction of that in the core," he said. But still the fire-brick – and they were the most refractory produced in this country – had been melted down like butter. The floors under the furnace were all made of fire-brick, and yet the brick had run together until they were one solid mass of glassy stone. "We once tried putting a fire-brick in the centre of the core," said Mr. Fitzgerald, "just to test the heat. Later, when we came to open the furnace, we couldn't find a vestige of it. The fire had totally consumed it, actually driving it all off in vapour."

Indeed, so hot is the core that there is really no accurate means of measuring its temperature, although science has been enabled by various curious devices to form a fairly correct estimate. The furnace has a provoking way of burning up all of the thermometers and heat-measuring devices which are applied to it. A number of years ago a clever German, named Segar, invented a series of little cones composed of various infusible earths like clay and feldspar. He so fashioned them that one in the series would melt at 1,620 degrees Fahrenheit, another at 1,800 degrees, and so on up. If the cones are placed in a pottery kiln, the potter can tell just what degree of temperature he has reached by the melting of the cones one after another. But in Mr. Acheson's electrical furnaces all the cones would burn up and disappear in two minutes. The method employed for coming at the heat of the electrical furnace, in some measure, is this: a thin filament of platinum is heated red hot – 1,800 degrees Fahrenheit – by a certain current of electricity. A delicate thermometer is set three feet away, and the reading is taken. Then, by a stronger current, the filament is made white hot – 3,400 degrees Fahrenheit – and the thermometer moved away until it reads the same as it read before. Two points in a distance-scale are thus obtained as a basis of calculation. The thermometer is then tried by an electrical furnace. To be kept at the same marking it must be placed much farther away than in either of the other instances. A simple computation of the comparative distances with relation to the two well-ascertained temperatures gives approximately, at least, the temperature of the electrical furnace. Some other methods are also employed. None is regarded as perfectly exact; but they are near enough to have yielded some very interesting and valuable statistics regarding the power of various temperatures. For instance, it has been found that aluminium becomes a limpid liquid at from 4,050 to 4,320 degrees Fahrenheit, and that lime melts at from 4,940 to 5,400 degrees, and magnesia at 4,680 degrees.

There are two kinds of electrical furnaces, as there are two kinds of electric lights – arc and incandescent. Moissan has used the arc furnace in all of his experiments, but Mr. Acheson's furnaces follow rather the principle of the incandescent lamp. "The incandescent light," said Mr. Fitzgerald, "is produced by the resistance of a platinum wire or a carbon filament to the passage of a current of electricity. Both light and heat are given off. In our furnace, the heat is produced by the resistance of a solid cylinder or core of pulverised coke to the passage of a strong current of electricity. When the core becomes white hot it causes the materials surrounding it to unite chemically, producing the carborundum crystals."

The materials used are of the commonest – pure white sand, coke, sawdust, and salt. The sand and coke are mixed in the proportions of sixty to forty, the sawdust is added to keep the mixture loose and open, and the salt to assist the chemical combination of the ingredients. The furnace is half filled with this mixture, and then the core of coke, twenty-one inches in diameter, is carefully moulded in place. This core is sixteen feet long, reaching the length of the furnace, and connecting at each end with an immense carbon terminal, consisting of no fewer than twenty-five rods of carbon, each four inches square and nearly three feet long. These terminals carry the current into the core from huge insulated copper bars connected from above. When the core is complete, more of the carborundum mixture is shovelled in and tramped down until the furnace is heaping full.

Everything is now ready for the electric current. The wires from the Niagara Falls power-plant come through an adjoining building, where one is confronted, upon entering, with this suggestive sign:

Tesla produces immensely higher voltages than this for laboratory experiments, but there are few more powerful currents in use in this country for practical purposes. Only about 2,000 volts are required for executing criminals under the electric method employed in New York; 400 volts will run a trolley-car. It is hardly comfortable to know that a single touch of one of the wires or switches in this room means almost certain death. Mr. Fitzgerald gave me a vivid demonstration of the terrific destructive force of the Niagara Falls current. He showed me how the circuit was broken. For ordinary currents, the breaking of a circuit simply means a twist of the wrist and the opening of a brass switch. Here, however, the current is carried into a huge iron tank full of salt water. The attendant, pulling on a rope, lifts an iron plate from the tank. The moment it leaves the water, there follow a rumbling crash like a thunder-clap, a blinding burst of flame, and thick clouds of steam and spray. The sight and sound of it make you feel delicate about interfering with a 2,200-volt current.

This current is, indeed, too strong in voltage for the furnaces, and it is cut down, by means of what were until recently the largest transformers in the world, to about 100 volts, or one-fourth the pressure used on the average trolley line. It is now, however, a current of great intensity – 7,500 ampères, as compared with the one-half ampère used in an incandescent lamp; and it requires eight square inches of copper and 400 square inches of carbon to carry it.

Within the furnace, when the current is turned on, a thousand horse-power of energy is continuously transformed into heat. Think of it! Is it any wonder that the temperature goes up? And this is continued for thirty-six hours steadily, until 36,000 "horse-power hours" are used up and 7,000 pounds of the crystals have been formed. Remembering that 36,000 horse-power hours, when converted into heat, will raise 72,000 gallons of water to the boiling point, or will bring 350 tons of iron up to a red heat, one can at least have a sort of idea of the heat evolved in a carborundum furnace.

When the coke core glows white, chemical action begins in the mixture around it. The top of the furnace now slowly settles, and cracks in long, irregular fissures, sending out a pungent gas which, when lighted, burns lambent blue. This gas is carbon monoxide, and during the process nearly six tons of it are thrown off and wasted. It seems, indeed, a somewhat extravagant process, for fifty-six pounds of gas are produced for every forty of carborundum.

"It is very distinctly a geological condition," said Mr. Fitzgerald; "crystals are not only formed exactly as they are in the earth, but we have our own little earthquakes and volcanoes." Not infrequently gas collects, forming a miniature mountain, with a crater at its summit, and blowing a magnificent fountain of flame, lava, and dense white vapour high into the air, and roaring all the while in a most terrifying manner. The workmen call it "blowing off."

At the end of thirty-six hours the current is cut off, and the furnace is allowed to cool, the workmen pulling down the brick as rapidly as they dare. At the centre of the furnace, surrounding the core, there remains a solid mass of carborundum as large in diameter as a hogshead. Portions of this mass are sometimes found to be composed of pure, beautifully crystalline graphite. This in itself is a surprising and significant product, and it has opened the way directly to graphite-making on a large scale. An important and interesting feature of the new graphite industry is the utilisation it has effected of a product from the coke regions of Pennsylvania which was formerly absolute waste.

To return to carborundum: when the furnace has been cooled and the walls torn away, the core of carborundum is broken open, and the beautiful purple and blue crystals are laid bare, still hot. The sand and the coke have united in a compound nearly as hard as the diamond and even more indestructible, being less inflammable and wholly indissoluble in even the strongest acids. After being taken out, the crystals are crushed to powder and combined in various forms convenient for the various uses for which it is designed.

I asked Mr. Acheson if he could make diamonds in his furnaces. "Possibly," he answered, "with certain modifications." Diamonds, as he explained, are formed by great heat and great pressure. The great heat is now easily obtained, but science has not yet learned nature's secret of great pressure. Moissan's method of making diamonds is to dissolve coke dust in molten iron, using a carbon crucible into which the electrodes are inserted. When the whole mass is fluid, the crucible and its contents are suddenly dashed into cold water or melted lead. This instantaneous cooling of the iron produces enormous pressure, so that the carbon is crystallised in the form of diamond.

But whatever it may or may not yet be able to do in the matter of diamond-making, there can be no doubt that the possibilities of the electrical furnace are beyond all present conjecture. With American inventors busy in its further development, and with electricity as cheap as the mighty power of Niagara can make it, there is no telling what new and wonderful products, now perhaps wholly unthought-of by the human race, it may become possible to manufacture, and manufacture cheaply.