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The claims of the patentee are as follows: "(1) The method of generating heat for metallurgical operations herein described, which consists in passing an electric current through a body of broken or pulverized resistance material that forms a continuous part of the electric circuit, the ore to be treated by the process being brought into contact with the broken or pulverized resistance material, whereby the heat is generated by the resistance of the broken or pulverized body throughout its mass, and the operation can be performed solely by means of electrical energy. (2) The method of smelting or reducing ores or metalliferous compounds herein described, which consists in subjecting the ore, in the presence of carbon, to the action of heat generated by passing an electric current through a body of broken or pulverized resistance material that forms a continuous part of the electric circuit, the ore being in contact with the broken or pulverized resistance material, whereby the ore is reduced by the combined action of the carbon and of the heat generated solely by the resistance of the broken or pulverized body throughout its mass. (3) The method of smelting or reducing ores or metalliferous compounds herein described, which consists in pulverizing the ore, and mixing with it pulverized or broken carbon or like material, then introducing the mixed ore and carbon within an electric circuit, of which it forms a continuous part, the said circuit being established through the carbon constituents of the mass, whereby the heat is generated by the electrical resistance of the carbon throughout the mass, and the operation can be performed entirely by means of the carbon reagent and the electrical energy. (4) The method of smelting or reducing ores or metalliferous compounds herein described, which consists in subjecting the ore, in the presence of a reducing agent, to the action of heat generated by passing an electric current through a body of broken or pulverized resistance material that forms a continuous part of the electric circuit, the ore being in contact with the broken or pulverized resistance material, whereby the ore is reduced by the combined action of the reducing agent, and of the heat generated solely by the resistance of the broken or pulverized body throughout its mass." Patent No. 319,915, to the same patentees, dated June 9, 1885, is a patent for the apparatus by which the process just described was carried on. In the specifications it is said that "there is no deposit made on either plate of the decomposed constituents of the material reduced.” The plates referred to are those which formed the anode and the cathode. Again it is said: “The reduced metal is found, at the close of the operation, filling the interstices between the particles of carbon mixed with it and plated, as it were, onto the same; and, when the carbon is very coarse, it works down through it, and collects in the bottom of the charge on the charcoal floor."
In patent No. 321,658, also issued to the Cowles brothers, a process is described of smelting ore for the production of alloys, bronzes, and metallic compounds. Patentees say: "In a prior application we have described an important process of smelting ores and reducing tbe salts of refractory metals by means of electricity, which consists, briefly, in the use of a body of broken or pulverized carbon made incandescent by the passage of an electric current through the same; and in carrying out our present invention we preferably use said process as being best adapted for the purpose. This invention consists in mixing or imbedding in the body of broken carbon pieces of the metal which is to constitute the base of the alloy, whereby it is melted by the incandescent carbon, and takes up the other metal, whatever it may be, that is being smelted or reduced. This produces an alloy rich in the rare metal, sometimes to the point of saturation, and the alloy is afterwards brought down to the proper percentage by the remelting of the alloy and the addition of the necessary amount of base metal, by any ordinary process."
The patentee describes the application of the invention to the Siemens electric arc thus: "For example, in that we would either mix the ores or metals to be reduced together or alloyed in the arc furnace or crucible, or we would use an electrode of copper, tin, nickel, iron, or other metal, as the case might be, depending on the heat and force of the current at the arc to smelt and carry over, to the mixture of ore, carbon, or metals, the metal of the electrode, and thus incorporating the same together into an alloy, carbide, silicide, or boride, as desired, the operation being performed entirely by electrical energy and the reducing effect of carbon; and we further assert that results in
alloying and compounding may be obtained that cannot be otherwise per formed, on account of the intensity of the temperature attainable by this means, and above all by the intermixing, incorporating, and merging power of the current. * * * We are aware that alloys have been produced by electrolysis, the current being made to pass through plates of platinum and carbon placed in contact with a base metal and with the compound to be reduced, and therefore we do not claim the same broadly."
The claims of the patentee are as follows: "(1) The process of producing alloys, which consists in passing an electric current through a mixture of broken resistance material,-ore to be reduced and pieces of the base metal of the alloy,-so that said mixture is rendered incandescent, and the alloy formed, substantially as hereinbefore described and set forth. (2) The process of producing alloys, which consists in passing an electric current through a mixture of broken resistance material and ore to be reduced, into which wires or rods of the base metal of the alloy have been inserted transversely to the path of the current, substantially as and for the purpose set forth. (3) The process of producing alloys hereinbefore described, which consists in mixing together ore of one of the metals of the alloy, broken or pulverized carbon, inserting wires or rods of the other metal of the alloy into the said mixture, and then passing an electric current through the mixture in a transverse direction to the wires or rods, so that the said mixture is rendered incandescent, and an alloy formed, substantially as set forth."
Patent No. 335,058, to Alfred H. Cowles, is a patent for an electric furnace and method of operating the same. “This invention,” says the patentee, "consists in the improved method of operating incandescent electric furnaces here in described, and in the combination, with a furnace containing a charge of electrical resistance material, of two movable electrodes situated at opposite ends of the furnace, and projecting into the body of the charge contained within it, so that the said electrodes may, when the resistance runs down, be drawn apart, thereby increasing the amount of the charge between the electrodes, and consequently increasing the resistance, and thus preserving a uniform resistance within the furnace.
*" After describing the furnace, the patentee goes on: “This invention relates to electrical smelting furnaces operating on the incandescent principle, in which metallurgical operations requiring an intense heat are carried on, with electricity as the heat-producing agent. D is the charge. This consists, ordinarily, of electrical resistance material, such as electric light carbon and the ore to be reduced. Both of these are previously pulverized and intimately mixed together before being placed in the furnace; but in some cases puiverized ore alone is used when it is a sufficient conductor of electricity. The first and second claims of this patent are as follows: "The method of smelting ores and other substances by the incandescence of an electrical resistance material contained in said substances or mixed therewith, which consists in first bringing a limited quantity of the material to be treated between a pair of electrodes, and then gradually increasing the quantity of such material by causing the electrodes to recede from each other, substantially as herein set forth. (2) In the art of smelting ores and other substances by the direct heating action of the electric current, the method of obtaining a uniform action of said electric current upon the mass or charge to be treated, berein described, which consists in introducing into the charge electrodes which are normally in proximity to each other, and then gradually causing said electrodes to recede from each other, the contact with the charge still being preserved until the mass of the charge is contained between the said electrodes, substantially as set forth."
* The current of electricity flows from the sides and ends of the said electrodes through the charge, and causes the electrical resistance material in the charge to become incandescent. The intense heat of the said incandescent material reduces the ore. When the furnace is employed for the reduction of ore, the metal is found at the close of the operation filling the interstices between the particles of carbon, mixed with it, and at the bottom of the furnace, where it collects upon the charcoal floor after having worked down through the charge. When the furnace is started, the electrodes are near together in the positions indicated by dotted lines, the resistance at the start being very great. After the furnace has been running for a while, and this portion of the charge between the electrodes has become heated, the re sistance falls, and the electrodes are then drawn out a little, increasing the length of the charge between them, and bringing into the active part of the electrical field additional parts of the charge. In this manner, by successive withdrawings of the electrodes, a uniform resistance is preserved until the entire charge is brought into action. * * * I am aware that it is not new to make the electrodes of an electric furnace automatically adjustable, so that, as the resistance diminishes, they are drawn apart, and I do not claim the same broadly; but all such attempts and experiments have relation to furnaces in which the electric arc is employed, and, the electrodes being subject to rapid, wear, the loss must be compensated for. * * * A continuous body of material is preserved between the electrodes, and the distance between them varies, gradually widening from the beginning of the operation until the whole of the charge is brought into action."
Patent No. 324,659, issued to Cowles, Mabery, and Cowles, is for a process of obtaining aluminium. In this patent the patentees refer to the fact that aluminium can be produced under the patents Nos. 319,945 and 317,795, already described, and continues: “Ores are reduced in said furnace by mixing them with broken or granular carbon, and passing an electric current through a charge of the mixed ore and carbon; but the product thereby obtained, when an ore of aluminium is reduced, contains a considerable percentage of carbon, which is taken up both chemically and mechanically by the aluminium; and the object of the present invention is to provide a process whereby the aluminium can be obtained free from carbon and in a pure metallic state. This we accomplish by reducing the ore of aluminium, in company with tin, copper, manganese, or other metal which will alloy with the aluminium, and then subsequently separating the alloying metal from the aluminium by amalgamation, lixiviation, or equivalent process, leaving the residue aluminium in the form of an amorphous powder or state, which can be melted down into an ingot. When aluminum is alloyed with either of the metals above named, it takes up very little, if any, of the carbon; whereas the pure aluminium will, as above stated, absorb a very considerable percentage of carbon, more even than iron or any of the other metals. * * * We are aware that it has been heretofore proposed to reduce aluminium ores by smelting them with zinc ores, and then separating the two metals, and that the alkaline earths have been reduced by electrolysis in contact with an alloying metal and plates of carbon or platinum, and the alloyed metals thus produced subsequently separated. We do not, therefore, claim the same broadly, but what we do claim as our invention, and desire to secure by letters patent, is: (1) The method of producing aluminium which consists in reducing an ore or compound of aluminium, in company with an amalgamating metal, by means of electricity and in the presence of carbon, substantially as described, and then separating the two metals of the alloy by amalgamation. (2) The method of producing aluminium which consists of mixing the aluminium ore with carbon and with a metal, reducing the said ore by means of electricity, so that the aluminium forms an alloy with the said metal, and finally separating the two metals of the alloy, substantially as set forth. (3) The method of producing aluminium which consists of mixing the aluminium ore with broken.carbon and with a metal, reducing the said ore by means of electricity, so that the aluminium forms an alloy with the metal, and finally separating the aluminium from the alloy by amalgamating the said metal, substantially as set forth."
As already stated, three patents were issued to Bradley on his original application, No. 85,957, of February 23, 1883. One was for heating by a blow pipe, and has no relation to this controversy. The main patent was No. 468,148. His invention is described in his specifications as follows: "Wy invention relates to a process of effecting by the electric current the separation or disassociation of aluminium from its ores or compounds, or the decomposition in a similar manner of other like highly refractory metallic compounds, of which aluminium may be considered a type, and which have been classed together by reason of the great difficulty in their reduction. Hitherto this process has been carried on by subjecting the fused ore to the action of the current in a crucible or other refractory vessel placed in a heating furnace. where the temperature is sufficiently high to keep the ore in a melted condition ; but the greatest difficulty is encountered in preventing the destruction of the crucible with this mode of working the process, for it has been found that, in the case of cryolite especially, which is a double fluoride of aluminium and sodium, the fused ore unites or fluxes with the crucible itself, and that the gas liberated in the process of reduction (fluorine gas) attacks the material of which the crucible is composed, and the consequence is that the crucible is quickly destroyed. This destructive fluxing action takes place to a greater or less extent in treating almost any material, and is greatly aggravated by the fact that the crucible is subjected to heat from without; but, even in the case of materials which do not exert a fluxing action, the mere mechanical action of the external heat is sufficient to make it almost impossible to prevent the cracking of the crucibles. The main object of my invention, therefore, is to dispense with the external application of heat to the ore in order to keep it fused. In order to accomplish this object, I employ an electric current of greater strength or intensity than what would be required to produce the electrolytic decomposition alone, and I maintain the ore or other substance in a state of fusion by the heat developed by the passage of the current through the melted mass, so that by my invention the electric current is employed to perform two distinct functions, one of these being to keep the ore melted by having a portion of its electrical energy converted into heat, by the electrical resistance offered by the fused ore, and the other being to effect the desired electrolytic decomposition, by which means the heat, being produced in the ore itself, is concentrated at exactly the point where it is required to keep the ore in a state of fusion. Another feature of my invention consists in dispensing with the crucible for holding the ore, and in employing a body or heap of the ore itself to constitute the vessel or cell in which the reduction takes place, which is not destroyed by the chemical action of the fused ore and the gas liberated, and which, therefore, admits of the process being perfectly continuous, nothing being required but the charging of fresh ore as fast as the reduction goes on, either from without or from the sides or walls of the heap itself.”
The process he describes is as follows: "Upon a hearth of brick or other suitable material is piled a heap or body of the ore, more or less pulverized, in the shape of a truncated cone, and a cavity or basin is excavated in the top of the heap to contain the fused portion of the ore which is to be treated electrolytically. In order to fuse the ore at the start, I take two electrodes of a suitable material, such as already used in like processes where fusion has been effected by an external furnace, and connected, respectively, to the two poles of a dynamo-electric machine or other source of current, bring the said electrodes into contact, separate them sufficiently to produce an electric arc, and then thrust them into the ore lying at the bottom of the cavity or basin, where the ore soon fuses by the heat of the arc, and becomes a conducting electrolyte, through which the current from the electrodes continues to flow. The arc of course ceases to exist as soon as there is a conducting liquid-the fused ore-between the electrodes, and the passage of the current then takes place through the fused ore by conduction, and the heat is produced as it is in an incandescent lamp. The arc is merely used to melt the ore in the beginning, and the ore is kept melted by incandescence, so to speak; the metallic aluminium being gradually deposited at the cathode, and the fluorine gas being set free at the anode, so long as the ore is maintained in a state of fusion. As soon as the action is properly started, the electrodes should be moved a little further apart, in order that the metals set free at the cathode shall not form a short circuit between the electrodes, or be attacked by the fluorine set free at the anode. I have found that, by using an electric current twice as strong as would be employed to perform a given amount of electrolytic work in the ordinary way in externally heated crucibles, I am enabled to keep the ore fused according to my invention, without the application of any external heat whatever. * * I have described my process as preferably carried on by employing a body of the ore itself to form the basin or receptacle in which the electrodes are situated, between which the current flows through the ore for heating and electrolyzing the same. That specific invention, however, is not claimed herein, since it forms the subject-matter of Patent No. 161,933, dated December 8, 1891. My present invention is not limited to the specific character of the receptacle nor the spe
cific arrangements of the electrodes. What I claim as my invention is as fol. lows: (1) The process of separating or dissociating metals from their highly refractory ores or compounds, nonconductors in an unfused state, of which the ores and compounds of aluminium are a type, which consists in fusing the refractory ore or compound progressively by a source of heat concentrated directly upon it, rather than by an external furnace, and as it becomes fused, effecting electrolysis by passing an electric current therethrough between terminals which are maintained in circuit with the fused bath, whereby the process is rendered continuous, substantially as set forth. (2) The continuous process of separating or dissociating metals from aluminous or like highly refractory ores or compounds, nonconductors in an unfused state, which consists in progressively fusing the refractory ore or compound, and as it becomes fused electrolyzing it by passing an electric current therethrough of sufficient volume to continue and maintain the fusion and effect electrolysis, and adding fresh metal from time to time to preserve the bath constant, as set forth. (3) The process of reducing metals from that class of highly refractory ores and compounds, nonconductors in an unfused state, of which the ores and compounds of aluminium are a type, which consists in fusing a portion of the refractory or compound to be treated, in establishing an electric current through said fused portion, and by such current producing simultaneously progressive fusion of such ore or compound, and continuous electrolysis of the same as fused. (4) The process of separating or dissociating aluminium from its ores or compounds, consisting in fusing and maintaining the fusion, and electrolytically decomposing the ore or compound by the passage of the electric current therethrough, substantially as set forth. (5) The continuous process of separating or dissociating aluminium from its ores or compounds, consisting in fusing and maintaining the fusion, and electrolytically decomposing the ore or compound by the passage of the electric current therethrough, and charging the bath as the reduction proceeds, substantially as set forth. (6) The process of separating or dissociating aluminium from its ores or compounds, consisting in fusing and maintaining the fusion, and electrolytically decomposing the ore or compound by the passage of the electric current therethrough, and regulating the strength of said current in accordance with the requirements of the fused mass, substantially as set forth."
A reference to the file wrapper and contents shows that from 1883 until 1890 the claims of the patent were a number of times rejected by the examiners of the patent office on the ground that the use of an electric current for the combined purpose of heating and electrolyzing a metallic compound was shown by the published reports of Sir Humphrey Davy's experiments in, the electrolysis of soda and potash, as far back as 1807. Among the claims contained in the first application was this: (4) “In the electrolysis of materials, or other chemical compounds, in the fused state, the method of maintaining them in a fused state by the heating effect of the electrolytic current itself.” The case was appealed to the board of examiners in chief at a time when, among the claims, were the following: (1) “The process of obtaining metals from their ores or compounds consisting in maintaining the ore or compound in a fused or molten condition by the direct passage of an electric current therethrough, simultaneously electrolytically decomposing the ore or compound, and regulating the strength of the said current in accordance with the requirements of the fused mass, substantially as set forth.” (2) “The process of obtaining aluminium from its ore or compounds consisting in maintaining the aluminium ore or compound in a fused or molten condition by the direct passage of an electric current therethrough, simultaneously electrolytically decomposing the aluminium ore or compound, and regulating the strength of said current, in accordance with the requirements of the fused mass, substantially as set forth."
The result of the appeal and subsequent proceedings was the issuance of the patent and allowance of claims above stated. Patent No. 464,933, issued to Bradley, referred to in the specifications of his main patent, was, shortly stated, a patent for the method of fusing and electrolyzing ore by the use of a pile of the unfused ore as the basin or receptacle in which the fused ore was to be contained.