A. Frederick Collins

As wonderful in its production of high temperature as liquid air is in its cold producing properties, ranks thermit, the latest invention. This marvellous new compound, to which its inventor, Dr. Hans Gold-schmidt, of Essen, Germany, has given the name "Thermit," is made by combining in the proper proportions two elements most frequently occuring on the earth's surface, namely oxygen, in the form of oxides, and aluminum, the metal found in common clay. When these two substances are combined and then ignited, an enormously high temperature, equal to the intense heat of the electric arc light, is instantly produced.

The exact method of making the compound, the simplest way of obtaining the highest caloric value, and the most practicable manner of utilizing the resultant energy created by this process of combustion, have opened a new field of unlimited application, and thus another science is brought into the realm of those termed exact. While the reducing properties of aluminum were discovered at least fifty years ago, the scientific investigators who studied these phonom-ena overlooked entirely its most essential characteristic. It remained for Dr. Goldschmidt to point and invent a thermit mixture which, when once ignited in a single place, continued its self-combustion throughout its whole mass without any external source of heat. Thus a crusrble filled with a seething mass of thermit hot enough for the production of artificial diamonds or the welding of a crank-shank can be held in the hands with impunity, and many other equally interesting and useful experiments may be performed utilizing a temperature diametrically opposite to that of liquid air and in every way as spectacular.

But, unlike liquid air, the commercial value of thermit has already been proven beyond peradventure of a doubt. Its application in the production of pure metals and the faculty with which gigantic pieces of metal are welded together are in evidence in many cities throughout continental Europe.

The thermit compound is a grayish black powder, very like coarse gunpowder in appearance. When it is desired to obtain molten iron either in its pure state, for the arts, or for welding purposes, the aluminum powder and ferro-oxide, or iron rust, are placed in a crucible made of magnesia or other suitable material having high heat resisting qualities. Graphite or clay cruicibles will not answer the purpose, for the heat is so intense that under its influence they commence to bulge until their distortion causes them to crack.

The thermit is ignited by putting in a small pinch of peroxide of barium, and a fuse is led to this and ignited. A reaction takes place almost immediately, and the solid oxygen contained in the iron oxide combines with the aluminum, forming an aluminum oxide, while the iron contained in the oxide of iron runs to the bottom of the crucible, in virtue of being heavier than the aluminum slag separated from it. The reaction producing this remarkable result takes place in less than one minute, without regard to the quantity of thermit used. The result is an enormous heat, developed with safety, while in other and older experiments of external combustion there have been violent and explosive effects, and therefore only the smallest quantities could be tested. The chemical reaction provides a rapid evolution of heat, which when started from a given point, raises the next nearest portion of the mixture to a temperature sufficiently high to cause another reaction, and this mode of heat propagation continues until finally the entire mixture is ignited.

To find a method for the initial ignition of the thermit was in itself no easy task, and while barium peroxide is now used for the purpose of ignition, a long line of experiments were made before it was definitely ascertained that it offered the best medium that could be found. Second only in its usefulness to the production of pure metals, but capable of a more spectacular demonstration, is the thermit welding process. As a method for welding, thermit begins where the blacksmith's forge ends.

It is not intended to use the new process for welding small pieces of iron or steel, but where broken pieces of metal of great size are to be repaired, especially in situ, it fulfils a place unsupplied by any other method known. Every up to date road may quickly and cheaply have its rails welded together so that a smooth surface may be obtained. It is therefore readily seen what a useful compound it is.