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.
