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By D. W. Jessup

ONLY during the past few years, have the old-fashioned methods for treating ores and byproducts progressed to any marked degree. The advent of multiple-hearth roasting, blast roasting, the baghouse, and the Cottrell plant indicate this change. It is the ability to roast and smelt sulfide ores and concentrates that gave this later advance. Further investigations that will solve the problem of efficient handling of flotation concentrates and their attendant ills are of the utmost importance. With future developments, the metallurgist will be able to smelt more economically and to treat still more refractory ores, making the early methods appear small by comparison. GROWTH OF SMELTING Well within the memory of pioneer smeltermen, the ore was charged directly into the blast furnace as it came from the mine;, only the richer, ores were smelted, the lower grade and sulfide ores were undesirable. Matte was, at first, thrown away and only two products) were desired-slag and lead bullion. Scores of the early smelting companies failed because of improper reduction of ores, high costs, short- furnace campaigns, inability to treat sulfide ores, and ores containing-zinc. With the failure of weaker companies, consolidation eliminated many others, until today the field is dominated by a comparatively few organizations, each strong financially. Formerly, a few thousand dollars would erect a small plant, whereas the modern smelter costs over a million dollars. Ore and products to which formerly no attention was paid are now treated with comparative ease and at a good profit. Mechanical improvements have modernized smelting, furnace tonnages show an increase, and metal recoveries have made enormous strides. Even though costs have decreased, they have not dropped in proportion to the improvements, because of the higher wages, greater costs of fluxes and coke, more undesirable ores smelted, etc.

Jan 8, 1925

By J. G. Bartram

Jan 1, 1934

By A. W. McReynolds

E. OROWAN*—I observed the phenomenon of jerky yielding many years ago with zinc25 and cadmium single crystals. A significant point was that the jerks occurred not only when the stress was raised but also (sometimes, after a pause of many minutes during which no trace of creep was observable) at constant stress. The phenomenon may be closely linked with the inertia of the testing machine and of the specimen, although the inertia alone cannot account for it. If, during the test, the resistance of the material to plastic deformation suddenly diminishes while the applied force remains constant, a sudden deformation follows until the yield stress has risen, by strain hardening, to the level of the applied stress (= the value of the previous "upper yield point."). When this is reached, the rate of deformation has attained a maximum value because, up to this moment, the applied force was higher than the plastic resistance of the specimen, and the difference was used for accelerating the moving parts of machine and specimen. The kinetic energy accumulated is now transformed into plastic work by further deformation; that is. the deformation overshoots the point at which the plastic resistance equals the applied static force. When the kinetic energy has been used up, therefore, we are left with a specimen the yield stress of which is higher than the applied stress, and no further deformation can occur (apart from a little creep) until either the applied stress has been raised to the new yield stress level, or the yield stress has fallen by thermal recovery to the level of the applied stress. While this occurs, a new upper yield point can develop, for example, by precipitation.26

Jan 1, 1950

Boundary and general corrosio~z rates for higkpurity alutninum were ~rzeasured irz 16 pct HC1 at sJmllow penetrations (< 25 p). The rates for several high-angle random tilt boundaries, several [001] synzmetrical tilt boundaries, a 54-deg [010] twist, and a 15-deg randorn tw~st boundary were one-fourth to one-third higher than that of the (001) surface used as reference. Boundary attack was slower for 23 and 37-deg [001] tilt boundaries and a 16-deg [010] twist boundary. The corrosion rate for a (111) surface was roughly om-third higher than for (001) and was thus about as high as the corrosion rate of the fastest boundaries. The boundary attack did ?lot appear to parallel the variatiorz of boundavy energy. The signvicance of the anisotropy of corrosion was discussed.

Jan 1, 1966

By L. L. French

Jan 1, 1977

NORTH AMERICA Number of Members Page States of the United States Alabama 138 376 Arizona 304 376 Arkansas 41 377 California 1,484 378 Colorado 354 383 Connecticut 149 385 Delaware 33 385 District of Columbia 288 386 Florida 57 387 Georgia 21 387 Idaho 130 387 Illinois 565 388 Indiana 153 390 Iowa 11 390

Jan 1, 1952

By Gordon R. Haworth, J. Terry Aimone

The capital-short mining industry, faced with weak metal markets, will need to devise new and novel methods to finance future expansions.

Jan 9, 1977

By David S. Butts

The high cost of energy has made many solution mining corporations turn from fuel consuming evaporators to solar energy and solar ponds. The generally held concept of a solar pond is an area enclosed by dikes into which brine is pumped, water evaporated by the sun, and the resulting salts scraped from the bottom of the pond. This paper will show that solar ponding is not simple. It is a science involving six main areas. These areas are (1) land conditions, (2) meteorology, (3) fresh water, (4) accessibility, (5) manpower and (6) mineral resources. Each area is discussed to identify important parameters that must be investigated before the viability of a solar pond complex can be established as a mineral recovery step.

Jan 1, 1985

By S. R. Krogh, T. O. Olsen

Analytical expressions for the breakage rate as functions of mill charge, mill speed, particle size, ball diameter, and ball load are derived, using idealized models for probability of breakage (Gaudin and Meloy), energy distribution (Mempel), and arithmetic mean of effective ball energy (Langemanns). Computational results using the theoretical equations are compared to experiments. The equations enable simulation of ball mill grinding at different grinding conditions.

Jan 1, 1973

By Kenneth A. Grace

Jan 1, 1985

By Lynn B. Hales

The software systems which support the Pinto Valley Supervisory Control System are divided into three general categories. These are defined as the real-time operating system; a process data acquisition, reduction, and communication system; and a set of process-oriented systems which interface the operators and engineering staff to the process. The role of each of these three classes is reviewed. The software systems which provide reports, status displays, and trend graphs are discussed.

Jan 1, 1978

By Harrison R. Cooper

Measurement of process material composition with on-line instrumentation has commanded attention of metallurgical plant management as a logical extension of the sampling operation, making possible immediate determination of essential data needed to maintain efficiencies at the highest possible level. The current status of methods employed for online composition analysis of slurries and solid materials is reviewed.

Jan 1, 1984

By Hadyn W. J. Wren

The practical experience obtained from designing and commissioning of fully controlled coal preparation plants, using centralised mini computers is discussed. The importance of defining a workable operating philosophy is highlighted with particular reference to the problems associated with trying to achieve a total &apos;hands off&apos; concept. These experiences with a centralised computer controlled system have led to a deeper understanding of the interaction between the operation and the control system and the role of local control and management information within the overall control philosophy of a highly automated process plant. The utilisation of an extensive fully distributed microprocessor control system with over 6500 digital and analogue signals split into six autonomous areas with a supervisory system to provide operator interface is described. The important aspects of project definition and design needs are outlined with particular regard for achieving maximum efficiency with minimum complexity. Views of future trends are offered, based on the experience of both centralised computer and distributed processor systems.

Jan 1, 1984

By L. W. McKeehan

Jan 1, 1934

NORTH AMERICA ALASKA Anchorage.-Ames, M. B. Culver, H. W. Fiedler, H. L. Geehan, R. V. Langneas, O. O. Layfield, R. A. Parent, A. Saarela, L. H. Strandberg, H. Candle.-Robbins, J. S. Chichagof.-Russell, J. C. College.-Fox, E. F. Joesting, H. R. Lyman, R. F. Smith, M. C. -Wilcox, H. G. Douglas.-Cahill, W. E. Fairbanks.-Adams, J. M. CANADA Canadian Army Overseas.¬Ball, H. D. Bridges, O. Butterill, H. J. M. Lane, H. C. Millar, W. A.

Jan 1, 1942

NORTH AMERICA ALASKA Anchorage,-Ames, M. B. Culver, H. W. Fiedler, H. L. Fox, E. F. Gallemore, W. A. Kreitlow, E. J. Layfield, R. A. Saarela, L. H. Strandberg. H. Candle,-Bobbins, J. S. College.-Fackler, W. C. Joesting, H. R. Swift. R. E. "Wilcox, H. G.. Crooked Creek-Lyman. R. F. Fairbanks.-Beistline, E. H. CANADA Canadian Army Overseas,¬ Ball, H. D. Brides, C. Butterill. H. J. M. Ladner, F. E. Lane, H. C. Millar, R&apos;. A. Murchison, R. G. Passow, F. M. ALBERTA Calgary-Allen, R. E. de Hart. J. B. Dingman, C. W. Furnical. G. H. Gray, J. G.

Jan 1, 1943

By R. F. Mehl

Jan 1, 1936

By C. A. Stetefeldt

In May and June, 1885, I was engaged in examining the goldores of Las Minas, in the State of Vera Cruz, Mexico, with a view of finding a cheap and efficient method for extracting the gold. The following minerals could be plainly seen in the ore : magnetite, pyrites of iron, pyrites of&apos; copper, quartz, and garnet. Neither galena nor zinc-hlende mere visible, but the ore contained a trace of lead, and in some samples of ore from the Muertos mine, 1.19 per cent. of zinc mas found. Antimony and arsenic were not present. Native gold could scarcely be seen in specimens of&apos; the ore, and it only appeared—mainly in extremely fine particles—after pulverizing and washing. Magnetite was in every instance the most prominent mineral, its quantity varying between 43 and 67 per cent. Determinations of copper and sulphur showed that from 3.5 to 7 per cent. pyrites of copper, and from 3 to 22 per cent. pyrites of iron were present. The gold-value of the ore varied between 0.3 oz. and 0.8 oz. per ton. I do not speak of specimens, but of average samples of large quantities of ore put through the battery. In ore that had been crushed through a No. 40 screen, the gold appeared, in part, as free gold, the rest being thoroughly mixed with the magnetite and pyrites, both minerals containing about the same percentage of gold. If this free gold was brought in contact with pure quicksilver it (lid not amalgamate readily, even if the quicksilver was charged with sodium amalgam.

Jan 1, 1886

By J. H. Hamilton, J. R. Lewis, J. C. Nixon, C. L. Graverson

Recently there has been much speculation concerning the advantages of using oxygen enriched air or pure oxygen in pyrometallurgical processes. The advantage of using oxygen in the iron blast furnace and elsewhere in ferrous production metallurgy has been given careful consideration and, as a result, several experiments have been tried and a number of papers have recently appeared on this subject.1,2 The use of oxygen in nonferrous smelting likewise poses interesting problems, therefore any experimental data obtained in this area should likewise be of general interest.3 Ashcroft4 in 1933 claimed to have obtained improved results when copper concentrates were roasted in pure oxygen. However, his paper gives neither data nor experimental details. A few years ago a research program was started in this laboratory which had for its objective the determination of the mechanism of oxidation of metallic sulphides under varying conditions. To date we have studied the oxidation of galena,5 sphalerite, and chalcocite. It is a well known fact that copper sul-phde minerals are oxidized slowly by weathering agents, so that the sulphides of copper which find their way into a tailing pond are gradually changed into water-soluble and acid-soluble compounds. Commercially, the oxidation of copper sulphide minerals is accomplished by roasting them at elevated temperatures in air using a suitable (usually multiple hearth) roaster. Most copper smelters are equipped with such roasters. In this phase of the study we were especially interested in determining the effect of temperature on: (I) the air oxidation of chalcocite and (2) the oxidation of chalcocite using commercial oxygen. The amount of sulphur removed as sulphur dioxide, the percentages of water-soluble copper, and of acid-soluble copper were determined for the air oxidation tests. In the tests using commercial oxygen, the percentages of sulphur dioxide, water-soluble copper, acid-soluble copper, water-soluble sulphur and acid-soluble sulphur were determined. For these experiments the temperature was varied from 250 to 700°C. Experimental Preparalion of Chalcocite (Cu2S) Natural chalcocite is not pure, Minerals such as bornite, covellite, and chalcopy-rite may be present. It was decided, therefore, to prepare some chalcocite in our own laboratory. An intimate mixture of sulphur and hool divided metallic copper in the ratio of 4 g of copper to I g of sulphur was prepared. TO this was added a slight excess of

Jan 1, 1949

By S. D. Brady

In Monongalia County, West Virginia, the Pittsburgh and Sewickley beds lie west of the Monongahela River and underlie practically all the western end of the county. The average thickness of the Pittsburgh bed is 8 ft., where it is being mined at present, sometimes running up to 9 ft. The Sewickley bed is 4½ to 6 ft. thick and lies 90 to 100 ft. above the Pittsburgh bed. As the Pittsburgh bed had a known value, a large part of it was bought up without consideration of the Sewickley bed. When the Monongahela Railway was built up the west side of the Monongahela River, other interests bought up the Sewickley bed, as it was found to be equal in quality to the Pittsburgh, with slight local exceptions. The two beds, therefore, were owned by different people, and naturally each owner opened his mine and ran it without regard to the working of the other bed. Consequently, considerable portions of the upper bed were seriously affected for economical mining, especially on Scotts Run. In recent years there has been a tendency, influenced by the decision of the West Virginia Supreme Court, on the part of the operators in Monongalia County to try to coordinate their projections in the layout of their mines. A typical geologic section, according to the report of the West Virginia State Geological Survey on Monongalia County, agrees with Fig. 1. It is apparent that the rock above the Sewickley bed and between the Sewickley and Pittsburgh beds is of a rather friable ~lature, therefore it is easily broken in pillaring. About the only difference between this section and the geologic section in the Lowsville district is that in the latter district the rock between the coals is a denser sandstone and contains little shale and limestone and no evidence of Redstone coal. It is a laminated sandstone, and although it makes a harder mass, it is easily broken. While working in the Lowsville district, the author had an opportunity to examine a neighboring mine in the Sewickley bed, which was over a section being pillared in the Pittsburgh bed. The two mines belong to dif-

Jan 1, 1931