GOYDER & LAUGHTON.

Goyder & Laughton, in 1903, invented a machine which employed Potter's idea of adding the ore to an acid solution. They were the first to disclose the principle governing Potter's and Delprat's acid-flotation processes, namely, that the action of the acid on the ore generated gas-bubbles to which the sulphide particles attached themselves and were floated to the surface. One of the difficulties of the acid-flotation process was that the bubbles broke on reaching the surface, and the mineral particles sank again, that is, the surface tension was not strong enough to hold them up under the conditions to which the particles were exposed for flotation. This invention not only seeks to obviate a bad feature of the acid-flotation process, but in a measure takes advantage of it. The machine was tried in several plants at Broken Hill, but is not now in use.

WOLF.

Jacob D. Wolf, in 1903, invented a method of applying the principles of flotation. He used sulpho-chlorinated oil, or any other oil, and aimed to secure a high degree of mineral extraction with a low grade of concentrate in the first step, and by washing the concentrate with hot water in a suitable vessel to increase the grade of concentrate in the second step. As another feature in his process, air or steam was blown into the tailing, which raised to the surface globules of lost oil, with sulphides adhering thereto, thus increasing the percentage of extraction. This patent contains several ingenious devices, but no practical application of the invention has so far been made.

ELMORE (NEW VACUUM PROCESS).

In 1904, Francis E. Elmore took out a patent for an apparatus and process wherein he secured notation in the form of a mineral froth by the addition of a small quantity of oil, and" by the liberation of the air in the pulp in a fine state of subdivision, the liberation of the air being accomplished by subjecting the freely flowing pulp to a vacuum, and by heating, whereupon the air which is dissolved in the pulp, amounting to 2.2% by volume, at normal temperature and pressure, is released and attaches itself to the slightly oiled mineral particles, raising them to the surface. This process is performed in a machine of rather complicated design, having a capacity of 20 to 50 tons per day, depending on the nature of the ore. A battery of these is operated with comparative ease after the men have become accustomed to the different adjustments. This process had its most noted application at Sulitelma in Norway, and also at the Zinc Corporation's plant at Broken Hill, where it proved a decided success. This last-mentioned plant had 16 units in operation, producing 75,000 tons of concentrate per year. The concentrate was retreated by burning off the oil and then passing it over Wilfley tables to remove some of the lead. This process has been replaced by the Minerals Separation process. f The British Broken Hill Proprietary mine has a battery of 10 vacuum machines in operation.

The Elmore vacuum process has also been installed at Dolcoath, Ramsley, and Dolgelly, in Great Britain, J at the Garpensberg, Traag, Hadeland, Sulitelma, Telemarken, and Saxberget mines in Scandinavia, and at the Edmundian mine in Africa. It has been installed, but it is not working at the present time, at the Pinnacles mine and the Cobar gold mines in New South Wales, the Namaqua copper mine in South Africa, the Caucasus copper mine in Russia, at the Avino mine in Mexico, and elsewhere.

DE BAVAY.

Auguste J. F. De Bavay, in 1904, invented a flotation process in which a thin film of freely- flowing pulp was brought to the surface of a vessel of water where advantage was taken of the surface tension of the liquid, and the sulphide floated. He further points out that if the surface of the sulphide particles is coated with a film of carbonate from weathering, this is detrimental to the process, and should be removed by soaking the ore in a weak solution of carbonate of ammonia, or by passing carbonic acid gas through the pulverized wet ore, or by friction. His process was installed at the Broken Hill North mine in 1905, and was there a success. His plant and methods have undergone many changes, and he is now using a small quantity of oil to enhance the extraction. He first washes the tailing free from slime, and then adds a small amount of oil to the clean sand, with agitation, and separates the scum or film of mineral sulphides in a spitzkasten. A new mill having a capacity of i,600 tons per day was started in 1910 on the dumps from the Block 10 mine, combined with the current slime-free tailing of the North and South mines. This is the largest flotation-concentration plant. The venture was brought out as the Amalgamated Zinc (De Bavay's) Ltd!, which corporation also owned the exclusive right to use this process at Broken Hill, the patent rights for the rest of the world being retained by the De Bavay Treatment Co. These companies have not published any comprehensible statements of cost and treatment, and little is known about the methods they use.

GILLIES.

In 1906, James H. Gillies' patents were applied on a commercial scale at the Block 10 mine, Broken Hill, N.S.W. Gillies' apparatus seems to be unique ; his processes were based on the principles of Potter and Delprat, but later he made use of the principles described in the Minerals Separation patents. The plant was a failure economically, and has been abandoned.

MACQUISTEN.

Arthur P. S. Macquisten, in 1904, invented a process and a tube apparatus therefor which made use of the surface tension of liquids for separating minerals, whereby some floated and others sank. His apparatus is new and important, but works on the old and well known principle of surface tension. In 1906 this was applied on a working scale in the Adelaide Reduction Works, at Golconda, Nevada. The process, like all the flotation processes except the Minerals Separation and Potter-Delprat, has difficulty in handling slime.* The plant consists of 100 tubes, and the capacity is 125 tons per day. The latest development of this idea is the introduction of oil to the process, thus bringing it pretty much on a par with all the others as to the principles involved.

In 1911, the Federal Mining & Smelting Co. installed 119 of these tubes at the Morning mill at Mullen, Idaho, for the treatment of a middling product containing blende, galena, siderite, and quartz, but the results are not entirely satisfactory. The capacity is about 150 tons per day.

MUREX.

Lockwood & Samuel, in 1908, invented a process for making sulphide particles more magnetic by utilizing the selective action of oil, and in 1909 described a method of increasing the selective action of oil by treating it with various soluble salts ; also a process where magnetic or magnetizable substances are added to an ore-pulp, the whole being then treated with an oil to cause the sulphides and the magnetic particles to adhere together, and then removing them from the pulp by means of a magnet. Although this is not a flotation process, it makes use of some of the principles involved, and is in some respects similar. Two units have been installed and are successfully working at Cordoba, in Spain. A plant erected at Broken Hill on the Block 14 mine has, however, had many vicissitudes ; it has been closed down as unadapted for the work, and moved recently to the Amalgamated Zinc works.

Plants have been sent to Bolivia to a mine belonging to Aramayo, Francke, & Co., and to the Malines mine in France.

ZINC CORPORATION.

This is a company organized in 1905 to work the accumulation of zinky tailing in the Broken Hill district. The company purchased in all more than 4.000,000 tons of tailing and slime from different mines in the district.

The company did not own any process, but the history of the company has been so closely allied to the development of this branch of the art that it is quite proper to give a brief sketch of it. The company first tried the Potter process. A plant was built in 1905 at the British Broken Hill Proprietary mine, and was intended to have a capacity of 400 tons per day. After extended trials and expensive alterations, the Potter idea was abandoned as not practical.

In 1907 this plant was entirely re-modelled to install the Minerals Separation process. This process had been used for some time satisfactorily on the Central mine near by, but in the Zinc Corporation plant this process was also abandoned as not satisfactory.

Extended trials had been made in the meantime, under the management of D. P. Mitchell, with the new Elmore vacuumconcentration process. These trials had been most successful. It was decided, therefore, to move the scene of operations and build a new mill where better crushing facilities could be provided. This mill was built in 1907 and 1908 near the southern end of the Broken Hill district, and 16 Elmore units were installed. This process was a success, and ran for two years at a handsome profit. Then, in 1910, owing to improvements in the apparatus for the Minerals Separation process, and owing also to the depletion of supplies of material suitable to the Elmore process, the Minerals Separation process was again adopted. The Elmore units were taken out and the Minerals Separation process has now been operating on both sand and slime at a good profit for nearly two years.

The most recent step in the history of the Zinc Corporation is the amalgamation of that corporation with the Broken Hill South Blocks, Ltd., which gives the combined business, besides the excellent equipment of the Zinc Corporation and the enormous tonnage of purchased tailing, the advantage of the continuous supply of ore from the South Blocks mine.

HYDE.

In 1911 James M. Hyde invented and patented a flotation process in which a small amount of sulphuric acid, with or without the use of copperas (iron sulphate), is used to give the slimy portion of the ore a preliminary coagulation before bringing it to the flotation machine, and in which the sulphides, after agitation, are floated off rapidly and as completely as possible, with a considerable overflow of freelyflowing water, thereby producing an impure concentrate which is re-treated in a second machine, from which only high-grade concentrate is taken off, with no freely-flowing water. The process has been adopted by the Butte & Superior Copper Company of Butte, Montana, in their new 50o-ton zinc mill which is shortly to be increased to a capacity of 1,000 tons per day. The process is giving highly satisfactory results. This is the first attempt to use a flotation process on a large scale in the United States.

The recent amalgamation of the patent interests of the Amalgamated Zinc, Ltd., and the Minerals Separation, Ltd., in Australia, is a step in the right direction, as it will stop litigation already begun, and prevent more that was threatened. The De Bavay patent rights for the rest of the world are now owned by Minerals Separation, Ltd. The patents now included under the one group are those of Froment, Potter, Delprat, Cattermole, Sulman, Picard, Ballot, De Bavay, Goyder, Laughton, Higgins, Greenway, Chapman, Lavers, Nutter, and Hoover.

A much clearer idea of the evolution of the processes can be secured from a summary of the patents in chronological order, which is given in the next chapter. Some repetition will be necessary, but the history of metallurgical devices is largely a recital of alterations and experiments.