Amazing Stories/Volume 08/Number 02/Aluminum
By T. O’Conor Sloane, Ph.D.
THE metal aluminium, which has the better termination, although the word aluminum is very common, ranks as the third commonest element on the surface of the earth. Any number of rocks contain it with various other constituents. It forms the basis of clay, so that every one of our dinner plates or tea cups represents the compound of this metal with oxygen and sometimes with another element or elements in small proportion. The commonest pottery, such as a flower pot, is based upon the use of clay, which is the use of aluminium oxide. It is here that we meet with one of the curious variations in chemistry. Nothing can seem cheaper than a flower pot, but the identical aluminium oxide, crystalized and colored, it may be by chromium or some other element, gives us the ruby, the oriental emerald, the sapphire and other jewels, the ruby being practically at the head of the list in value.
It is a strange transition from a flower pot to a ruby; the latter weight for weight often exceeds the value of a diamond of corresponding size.
The color of the perfect ruby is expressed by the words “pigeon’s blood.” Artificial rubies are made by a fusion process and are colored by a very little chromic acid. Artificial sapphires made in the same way are colored by a trace of titanic oxide.
The Romans and other nations at the beginning of the Christian era collected salts from the surface of the ground in the volcanic regions, and among them aluminium sulphate. This gave them a mordant of great power for fixing the famous purple of Tyre upon the fabrics which they wove.
The women of antiquity were kept busy weaving fabrics. It is a strange thought that when man wanted to make a cover for his body, he started with thin threads and to effect the dying of the fabrics aluminium and iron salts came into play, and in this way the world drifted along for centuries. When beautiful rubies were brought from Burmah it never occurred to the monarchs, whose crowns were adorned with such jewels, that the composition of these beautiful rubies differed very little from the material of the commonest earthenware.
IT was not until the eighteenth century that chemists awoke to the idea that what we call chemical compounds were additive. They had formulated the absurd theory before this period, that when a metal was oxidized, and of course gave an oxide weighing more than the original, a mysterious thing called phlogiston had been removed from it, thereby increasing its weight so that actually this theory, which was upheld for some time in all its absurdity, reminds us of the stories of negative gravity, which have been written by such writers as H. G. Wells.
Lavoisier, the great French chemist discarding the absurd idea of phlogiston following along with the Englishman, Priestley, who had come to America, developed the additive theory of chemistry. Thus alumina or clay or rubies are formed by the addition of oxygen to the metal aluminium.
It was in the early days of the nineteenth century that the great English chemist, Sir Humphrey Davy, was using the primary electric battery to attack and decompose oxides. At one of the poles of his battery he had a globule of mercury, having a very correct idea that this would amalgamate as we now call it, so that an amalgam or “alloy” of mercury and of the metal would be produced by the current, and the mercury would act as a sort of collector of metal. It was by processes such as this that Davy produced sodium and potassium, but he could not produce unalloyed aluminium. That metal evaded him, but he did get alloys of it, or at least an alloy. Sir Humphrey Davy’s work in those days, excited the greatest public interest, comparable to that which the theorizing of Einstein and the work of such men as Millikan and Compton and of the investigators of the General Electric Company in Schenectady occasion now. For his operations he needed a powerful electric battery, and the primary batteries of those days were the only source they had for generating electric power of any considerable amount. A great number of jars were required for real power, and it was a long and tedious affair to set them up and fill them with solutions. From the moment the solution entered them, the zinc plates began to deteriorate, the copper or other negative plate would begin to polarize, as it is called, so that to get anything like power, even as much as every automobile uses in its starting, a very large battery would be required, and to get the good out of it there should not have been the least delay in starting work with it, because of this automatic and rapid deterioration in power.
To express appreciation for the work done by Sir Humphrey Davy with the battery, which included the production of the electric arc, we are told that the present of a great battery was made to Davy. But he had not yet obtained pure aluminium.
THIS was produced some ten years after his time—first as a gray powder and then as little pellets. The French chemist, Sainte-Claire Deville, followed up the work of preceding investigators and by using sodium as the reducing agent, where the far more expensive potassium formerly had been employed, approached what might be called, a manufacturing process. Deville’s experiments led to the establishment of a metallurgical plant in France under the auspices of Napoleon the Third, who was then Emperor.
The metal was exhibited at the different World’s Fairs and used to be called the “silver of clay.” It was quite the thing to give a piece of aluminium to someone to hold, so that they would realize its lightness, about a third that of iron, and great astonishment was excited by this feature. When first exhibited at a World’s Fair in 1855, it was very expensive. A pound of it was worth $90.00. This is not far from one-quarter the price of gold at the present day. Fifteen years later it had got down to $12.00 a pound and kept going down. In 1889 it was $2.00 a pound, in 1904 33c a pound and in 1911 the average price was 22c a pound. Clay gave up its “silver” at quite a low price.
Aluminium has increased enormously in the amount produced. In 1886 only one and one-half tons were reduced. Five years later the production was seventy-five tons and now it bids fair to attain the production of one hundred thousand tons.
Its lightness and strength suggest naturally its use for dirigibles or lighter than air ships. Its alloys have most interesting properties. In the Duren district, Germany, an alloy of the metal with copper, manganese and magnesium was produced which had such good qualities, that it is replacing other aluminium alloys, especially for the frames of dirigibles. The name duralumin is familiar to everybody, it is so frequently spoken of in the daily press. It is fair to say that very little unalloyed aluminium is used in a practical way; it is almost always alloyed with some other metal.
In reference to the modern kitchen, if we ask what are the great changes in the utensils of the chef, it would appear that they are pyrex, the glass which stands heat so well, and aluminium. The old time iron kettles were heavy and the tin kettles rusted. The aluminium ones which are substituted for them, are very light.
SOME of the more or less old-fashioned housewives were very proud of their copper pans and kettles. If these were neglected they would corrode and there would be danger of poisoning the food prepared in them, something which aluminium, except in exorbitant quantities of its compounds, will not do.
Following in the steps of Sir Humphrey Davy, and we strongly suspect in the steps of Faraday, most aluminium is now produced by electric power, by the electrolysis of one of its compounds called bauxite. This is dissolved or melted up with another compound of aluminium, sodium and fluorine, called cryolite. When a current of electricity is passed through the melted mixture, the aluminium very obligingly separates out from the bauxite, the cryolite being only slightly affected; although it contains aluminium it is but little decomposed, almost all the aluminum coming from the bauxite. There are great quantities of cryolite in Greenland and it used to be shipped from there by the cargo, but now it is produced artificially on the manufacturing scale.
If we go right down the line, aluminium will impress us as a very wonderful substance. It does all sorts of things according to the temperature and other conditions. The metal, when it approaches its temperature of fusion, is very brittle and can be easily reduced to powder. This powder mixed with a varnish-like vehicle constitutes aluminum bronze paint. It can also be beaten out until it is almost as thin as gold leaf. And now we come to a mechanical operation based on its affinity for oxygen.
If powdered aluminium is mixed intimately with chromium oxide, manganese oxide or iron oxide, the application of high heat to any portion of it, which may be very minute, will start a violent combustion of the aluminium and a reduction of the other metal, which reaction will automatically go through the mass, producing a very high temperature. It has been estimated that it will go as high as 5,000 degrees F. The oxide of chromium or of manganese or of iron as the case may be, is reduced to the metal, the aluminum taking up the oxygen and floating on top as a slag. This slag has the composition of the ruby or sapphire, but it certainly doesn’t look a bit like either. It floats upon the surface of the melted metal, chromium, manganese or iron, which is as liquid as water owing to the heat. The metal may be cast in molds; it may be poured upon iron objects which are to be welded together, and it can be used to repair broken parts of the frames of vessels, melting them together by its enormous heat where they are broken.
This is the famous thermit process. It can be done on a small scale and is so interesting and strange, that it has been used on the vaudeville stage as an exhibition. There are many deposits of magnetic oxide or iron in nature which are almost chemically pure. By applying the thermit process to this, it may be as little as a pound or two mixed with powdered aluminum in a crucible and starting the ignition, the metal oxide will be reduced and made liquid, so that it can be cast in a mold, and you can have a piece of almost chemically pure iron, so soft, because of its purity, that, as the metallurgist says, it can be cut with a knife—but if you will believe the writer, it cannot be cut to any considerable depth.
THE rapid increase in the tonnage produced indicated a rapid extension of uses for this “silver of clay.” With all its interesting properties, one is impressed by the definite limitations to which it is subject. Its soldering is not very impressive; it is done with considerable difficulty and is apt to be imperfect, but two or three workmen can go out on a railroad and using the thermit reaction can weld the joints of the heavy rails into a solid mass, carrying all the required material in a wheelbarrow.
The thermit reaction has been used on icebergs with considerable success. The enormous heat produced by the process, when a good quantity is used, operates to destroy or break up the menacing berg.
The use of the metal is spreading rapidly—the year 1942 has been “ear-marked” as the beginning of the age of aluminium, when thirty billion kilowatt hours, or a third of all the power generated on earth will be electrical, and a great proportion of it will be used for producing aluminium. For most purposes it will probably be alloyed with some other metal—an eight per cent addition of copper gives a standard casting alloy.
It is said that the world’s copper will be exhausted inside of fifty years—apparently aluminium will have to take its place. It is a good conductor of electricity, but it is so light that it has to be about double the diameter of copper wire of the same resistance.
And apropos to our subject, a most interesting lecture has recently been given at the annual Winter Convention of the American Institute of Electrical Engineers. Professor Colin G. Fink, of Columbia University, was the speaker. He made a prophecy that radical changes are indicated in our basic industries and that they will come in the next ten years from the use of this metal. There is plenty of room for such changes and it is fair to say that even the last ten years have witnessed radical changes.
AS the basis of these changes, Professor Fink accepted aluminium as one of the principal, or rather as the principal, element. The reduction of price of aluminium, putting this very light metal within the reach of large mechanical structures, gives a cause for very radical changes, but one which has required some seventy years to reach its present development and which is still increasing very fast in varied uses. Enormously tall structures such as we have in this city in their perfection would be impossible except for the use of steel instead of masonry in their construction. If such a building as the Empire State were constructed of masonry, the walls of the lower stories would be so thick, in order to resist the crushing strain, that there would be hardly any room for occupants and the very object of the height would be lost. By using steel the walls are kept so thin that the lower stories are as open to use and of as good an area as the upper ones.
Aluminum has already played a part in the manufacture of steel. The metal from the open hearth or Bessemer converter is liable to contain oxides or oxygen gas. By adding aluminium to the melted metal, it takes up most or all of the oxygen forming iluminium oxide which goes off with the slag.
It seems a little uncertain whether it can be used for the main structure of buildings in place of steel, but it is merely a question of price which determines whether it can be used for many of the details. Iron, as we know, perishes by rust, if pure. Cast iron, which contains a quantity of carbon, is almost exempt from destruction by oxidation, but the so-called steel as used in the past is subject to relatively quick destruction. Chromium goes far to prevent this, but aluminum is subject only to superficial oxidation. The oxidizing of the surface protects the interior. Our metallurgists have produced rustless steel by alloying it with chromium as one constituent. The futility of attempting to lighten it is of course perfectly obvious. But the common clay of mother earth gives us this metal which does not perish by oxidation, which is very strong, very light and a good conductor of electricity, so that the lecturer we have alluded to very happily predicted the age of aluminum as due within ten years.