PATENTS.
PATENTS.
In this analysis the intention is to set forth the flotation patents as they appeared from time to time, from 1860 to 1912, and to paraphrase and explain the meaning of them in language somewhat simpler than the legal phraseology of the patent. As the development of these processes has taken place mainly in Great Britain and the Colonies, the records of the English Patent Office have been followed as to dates, although those of the United States and other countries present some exception to strict chronology.
A careful search of the records of the patent offices of Great Britain and the United States reveals nothing prior to the year 1860 that in any way bears upon the subject of concentration by flotation.
EXPIRED PATENTS.
WILLIAM HAYNES, in British patent No. 488, February 23, 1860, described a process for separating mineral sulphides from the gangue or rocky constituent of an ore by the use of oily, gummy, or bituminous matter. This was not a flotation process, but must be considered the pioneer movement in that direction. The process described in the patent is as follows :
1. The ore is ground to the requisite fineness.
2. An agent, which may be a fat or an oil, alone or in combination with other things, is added to the crushed ore in the proportion of one part of agent to five or nine of ore.
3. The agent and ore are mixed or agitated in a proper machine.
4. Sufficient water, preferably warm, to cover the whole is added to the agitated and mixed mass.
5. The water and mixed mass of ore and agent are passed through a proper triturating machine, by which operation the combined sulphides and agent alone remain in union, while the earthy matter or gangue of the ore sinks to the bottom of the water.
The central idea of this invention is the separation in a triturating machine of sulphides from gangue by means of the selective adhesion of oils for sulphides.
JOHN TUNBRIDGE, in United States patent No. 228,004, Nov. 4, 1879, described a process for recovering finely comminuted metal held in suspension in water by the use of soap or a saponaceous compound. This patent is just nearly enough related to the subject matter of this discussion to be mentioned for the sake of completeness.
HEZEKIAH BRADFORD, in United States patent No. 345,951, June 22, 1885, described a process for separating sulphides from gangue by what is clearly the first well defined surface-tension flotation process.
For the treatment of wet tailing from tables, vanners, and jigs, one method is described, but for the treatment of dry crushed ore it is specified that the dry ore is to be sprinkled on the surface of water with as little concussion as possible, and from this point the treatment is obviously the same as with wet tailing. In its simplest form the apparatus prescribed takes the tailing, mixed with water from some previous operation, at a point say b (Fig. i), which may be a moving portion of a shaking table. By means of an adjustable lip &', the pulp is transferred to an inclined plane a, in passing over which the sulphide particles become exposed to the air, and the force of the surface tension of the liquid acting on these sulphide particles causes them to float on the surface of the liquid in the receptacle D, while the gangue, which remains wetted throughout the operation, sinks in receptacle D, and is removed at K. The sulphides, on the other hand, which are floating at the surface of receptacle D, float across the receptacle to the lip /, and plunge into the liquid contained in receptacle L. The baffles / arrest the fall of the sulphides and assist them to become wetted, so that the force of surface tension no longer acts on them, and they sink quietly to the bottom of receptacle M and are removed at 20, while the superfluous water passes over the lip N.
The central idea of this invention is the separation of sulphides from gangue by flotation of the sulphides at the surface of a freely flowing ore-pulp through the action of the force of surface tension of the liquid.
CARRIE J. EVERSON, in United States patent No. 348,157, Aug. 29, 1885, described a process for separating the sulphides in an ore from the gangue. The patent describes two distinct processes, the first of which is analogous to that of Haynes. The main improvement made by this first Everson process over that of Haynes is the discovery that acids increase the selective adhesion of oils for sulphide particles.
The second method Everson described is a flotation process pure and simple, and is of interest :
(1). The oil should desirably be first mixed with the ore.
(2) . Water containing a suitable amount of free acid in quantity ample for the operation to follow is added to the mixed ore and oil.
(3). Thorough agitation of the mass.
(4). Removal of the concentrate by flotation and a constant overflow of water from the washing-out vessel.
(5). The gangue being heavier, the inventor says, than the mixed oil and sulphides, sinks to the bottom of the washing-out vessel and can be removed there.
The central idea of this invention is the separation of sulphides from gangue by flotation of the sulphides at the surface of the liquid in a vessel, this flotation being accomplished through the agency of the forces brought to bear on the ore-pulp by the addition of oil and acid, and by thorough agitation.
EDWARD DODE, in British patent No. 14,357, Sept. u, 1889, described a process that refers to the separation of metallic gold, silver, etc., from other metals by first dissolving them in acid solution and then treating them with oily substances. The patent is just nearly enough related to the subject matter of this discussion to be mentioned for the sake of completeness.
HEBRON & EVERSON, in United States patent No. 471,174, Sept. i, 1891, described a process wherein they mixed a buoystock with the ore. This process is in the main similar to Everson's, and has some remarkable affinities with Bradford's, but there is some radical departure from previous patents.
The essential feature of the invention consists in submitting the ore and the buoy-stock to a rubbing movement so that the particles of buoyant material are pressed into the cavities and pores of the mineral and made to adhere to the rough and irregular surfaces thereof, so that the joined mineral and buoyant material are of less specific gravity than the rock particles of the ore.
CHARLES B. HEBRON, in United States patent No. 474,829, July 22, 1891, describes an improvement to the Hebron & Everson invention, which consists in subjecting the mixed ore and buoy-stock to a vacuum and heat, thus greatly increasing the efficiency of the buoy-stock. This patent is built upon the foregoing one, but emphasizes two important points :
(1). The buoyant material is more advantageously added to the ore hot, in a vacuum, as in that case the buoyant material comes into closer union and is more intimately joined to the metallic or sulphide particles.
(2). After the buoyant material has been mixed with the ore in a vacuum, the ore must be thoroughly aerated by blowing air through the mass.
The prepared ore was then submitted to a notation treatment, substantially the same as that described in Hebron & Everson, where the addition of air to the operation and effervescence of the liquid are recommended.
EDGAR A. HOCKLEY, in United States patent No. 466,753, Jan. 5, 1892, described an invention whereby particles of metal or mineral may be recovered by flotation aided by the introduction of air.
ALBION M. ROUSE, in United States patent No. 469,599, Feb. 23, 1892, described a method of creating a froth or foam of matter foreign to water and the recovery thereof.
MALECZEK,in New South Wales patent No. 3823, of the year 1892, described a frothing process, wherein as a result of treating the ore with salt solution in hot oil the sulphides were floated to the surface, presumably through the agency of air or other bubbles, and floated as a froth.
JOSEPH WILLIAM SUTTON, in British patent No. 24,144, Dec. 31, 1892, described a process for recovering gold from its solution by means of flotation with oils in an acidified liquor. This patent is just nearly enough related to the subject matter of this discussion to be mentioned for the sake of completeness. JOSEPH WILLIAM SUTTON, in United States patent No. 521,899, Dec. 28, 1892, duplicated his British patent No. 24,144, Dec 31, 1892.
HENRY LIVINGSTONE SULMAN, in British patent No. 24,939, Dec. 28, 1893, described a process for preventing the loss of float gold in milling operations, by adding certain substances that cause it to sink by diminishing the surface-tension of the liquid. This patent is just nearly enough related to the subject matter of this discussion to be mentioned for the sake of completeness.
ROBSON & CROWDER, in British patent No. 427, Jan. 8, 1894, described a process for separating sulphides from gangue. This invention made use of the idea that oils have a selective adhesion for sulphides, but it differs from the previous inventions in that no acid and no air was used in the operation.
(1). The crushed ore, if not already in a proper state, was first moistened with water.
(2). The moistened ore was then mixed with a large volume of oil with constant stirring and the continuous addition of oil.
(3). The sulphide particles were thereby floated away over the lip of the vessel by the constant overflow of oil.
This process does not seem to be much of an advance in the art. There have been some recent patents of a similar kind describing processes for separating mixed sulphides, but they are of doubtful utility. As this patent departs from the progressive line of development indicated by previous patents, and also because the line it takes has come to no commercial application, it is not necessary to consider it further, but it is here mentioned for the sake of completeness.
JOHN HENRY McCoY, in United States patent No. 577,825, Feb. n, 1895, described an invention for introducing air into a pointed box, for the purpose of separating particles. This is not a flotation process, but is mentioned for the sake of completeness.
UNEXPIRED PATENTS | HENRY A. ALLEN | AUGUSTE JOSEPH FRANCOIS DE BAVAY | JACOB DAVID WOLF
