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By Myrick N. Bolles

The concentration of gold and silver in mattes low in copper, and the subsequent separation and recovery of either or both of these metals, is a question the satisfactory solution of which has long vexed metallurgists. It covers a broad and important department of metallurgical science and brings in its train a series of attendant problems continuing from the initial operations of concentration to the final recovery of " values."

Jan 1, 1905

By C. A. Zapffe

BOTH the foundryman and the theoretical metallurgist are now generally agreed that the anomalous "rising" or "bleeding" of certain ferrous castings of killed metal is primarily attributable to hydrogen. How and why the phenomenon occurs, however, have not been made clear. The following discussion is intended to harmonize foundry experience with metallurgical theory so that the foundryman may possibly improve his ability to prognosticate whether a certain casting may bleed or not. BLEEDING, RISING, AND PIPING The "rising" to be discussed here is not to be confused with the action in rimming ingots as a result of the carbon-oxygen reaction, although a conclusion will be drawn that may apply to the art of controlling the rimming action. Only killed metal is considered, which includes both steels and irons. In Fig. I, three killed, chill-cast ingots are shown: a porous ingot whose evolution of gas during late stages of solidification has ejected metal through the top; an ingot in which moderate gas evolution during solidification has lifted the mushy central metal, i.e., it has "risen"; and, third, a sound ingot with good piping characteristics. The first type is referred to as "bleeding," and generally infers that a solid skin had first formed through which the liquid metal later erupted. There is no fundamental distinction between bleeding and rising in reference to killed metal.* POROSITY Hydrogen appears as a cause of bleeding because the gas evolution simultaneously leaves a porosity of a type traceable to hydrogen. Twenty years ago, Melmoth1 noted that killed steel that rose unexpectedly in the mold, if returned while liquid to the furnace and heated further under a reducing lime slag, would again rise in the mold; but that if the ingot were allowed to solidify and was then remelted no rising occurred. A critical quantity of the responsible gas is therefore removed by the rising action. Melmoth associated rising with high silicon (0.7 to 0.9 per cent) and concluded that silicon increased gas absorption. Because silicon is a strong deoxidizer, oxygen must, therefore, be eliminated from consideration of the three common gases in steel-oxygen, nitrogen, and hydrogen. Butterworth2 later decided that pinhole porosity was caused by gases dissolved in the metal and that hydrogen was obtained from steam in the mold. Allen's classical work on copper castings,3 soon followed by

Jan 1, 1942

THIS chapter and the one following deal with the heat quantities involved in open-hearth steelmaking, including the thermal efficiency of the furnace as a generator of high-temperature heat, the heat storage in the steel and slag produced and in the furnace walls, and the heats of the various chemical reactions involved in combustion, in the formation of slag, and the refining of steel. The fundamental laws to be considered are the simplification of the first two ' laws of thermodynamics as applied to problems involving sensible and potential (or latent) heat only 1. Heat input equals heat outflow plus storage. 2. Heat may be transferred only from a hotter body to a colder one. The first of these laws relates to the various heat quantities or the "heat balance" of the process. No one has as yet made an open-hearth heat balance that came out almost exactly balanced, and we assume that the cause lies in the difficulties of accurate temperature and flow-rate measurements at the high temperatures involved and the inherent complexities of flow distribution, air leakage, etc., present in any real, open-hearth furnace system. Some idea of the magnitude of the heat quantities involved can be obtained- by a brief, crude outline of the heat balance of a 90-ton heat of steel. We will assume a 60 to 70 per cent hot-metal charge in a fairly fast working and only moderately efficient furnace, burning fuel oil, with a fuel consumption of around 4 million B.t.u. per net ton. of ingots produced. The time from start of charge to tap is 9 hr. During this period, the oil burned represents 360 million B.t.u., and the sensible heat in the preheated air at the port ends is 117 million B.t.u. so that the total heat input at the ports is 477 million B.t.u. Heat stored in the steel and slag at the end of the heat, plus the various amounts absorbed by certain bath reactions, amounts to a total of 195 million B.t.u., but 120 million of this is supplied by the heat in the hot metal and by various heat--evolving reactions in the bath, so that only 75 million B.t.u. need be supplied to the bath by the flame.

Jan 1, 1944

Jan 1, 1947

By R. B. Muter, W. C. Grady, T. D. Wheelock, D. G. Chedgy

INTRODUCTION Topics of special interest, such as preparation plant flowsheets and noise pollution, are described in this chapter along with a discussion of non- state-of-the-art processes such as chemical cleaning, high intensity magnetic separation, and bacterial oxidation. PREPARATION PLANT FLOWSHEETS by RICHARD B. Muter In determining the layout or combination of unit operations to be utilized in a modern preparation plant several factors must be taken into account.

Jan 1, 1979

By W. F. Boericke

INTRODUCTION THE Wisconsin zinc district, or the Upper Mississippi lead. and zinc district as it is also termed, lies in the southwestern corner of Wisconsin, and embraces adjacent portions of Illinois and Iowa. It includes Iowa, Grant, and Lafayette counties in Wisconsin, and Jo Davies county in Illinois. In Iowa, Dubuque formerly produced considerable lead, but there has been little mining there in recent years. The map, Fig. 1, shows the entire district, with roads, railways, streams, and the various towns, or "camps," around Which the mines. are clustered. The hatchwork indicates the areas iii which lead and zinc have been mined. The district is about 60 mi. (96 km.) north and south and about 40 mi. (64 km.) east and west. Not all of the territory is mineral bearing, and there are considerable areas that are believed to be barren. The grouping of the mines is patchy and irregular, though certain broad zones of mineralization extend almost the full width of the district, as from Mineral Point west through Mifflin and Livingston, and from Shullsburg west through New Diggings and Hazel Green. It is worth noting that the best mines of the district have, to date, been found within 10 mi. east or west of the fourth principal meridian line, thus lying within a long, narrow, north-and-south belt extending the length of the district. In a field as large as the Wisconsin, which has only within com-paratively recent time been worked intensively for zinc, the. chances are good for, opening new and important orebodies in parts of the district not yet, or insufficiently, prospected. However, the prospecting has been most successful around, or adjacent to, the old lead diggings of nearly a century ago, and the camps that were well known then are still centers of activity. In their order of importance they are: New Diggings, Benton, Mifflin-Livingston, Galena, Linden, Hazel Green, Shullsburg, and Highland.

Jan 8, 1919

By Francis Freeland

An examination of accessible English literature shows that but small space has been allotted to the determination of faults ; most suggestions being confined to Schmidt's rule of the downthrow on the hanging-wall of the fault, or the coal-miner's rule of the obtuse angle. Von Carnall's modification of Schmidt's rule is sometimes given without the important exception, and Zimmermann's rule is

Jan 1, 1893

By Samuel B. Christy

Jan 1, 1889

Jan 1, 1897

Jan 1, 1924

NORTH AMERICA Number Members Alaska 36 Canada 323 Mexico 184 Newfoundland 3 United States Alabama 40 Arizona 111 Arkansas 8 California 646 Colorado 171 Connecticut 90 Delaware 21 District of Columbia 136 Florida 16 Georgia 7 Idaho 66 Illinois 208 Indiana 66 Iowa 11 Kansas 24 Kentucky 32

Jan 1, 1934

By T. Egleston

ALTHOUGH the success of metallurgical operations depends so largely on the possibility of finding proper refractory materials, which enter so prominently into the cost of their operations, it can hardly be said that our knowledge of them is in a very satisfactory condition, or even that we know very much about them, beyond a few facts which have been gathered through their use. Experience, as a general thing, is an excellent master, but the requirements of * This article was written at the suggestion of the Committee of the Institute on Refractory Materials, with a view of calling attention to the anomalies and difficulties of the subject. It was hoped that its discussion would eventually lead to the appointment of a Commission, by the great metallurgical interests of the United States, to investigate the whole subject, since it is believed that a better and cheaper artificial product can be made than any now in use, and that many other important incidental results would be accomplished by such an investigation.

Jan 1, 1876

By E. S. Greiner

Germanium and silicon have been plastically deformed in torsion at elevated temperatures. Slip took place on the four {Ill} planes. Dislocations, revealed by etch pits on a (111) face, occurred in rows that were traces of operative slip planes. THE plastic deformation of germanium and silicon by bending and tension at elevated temperatures has been reported by Gallagher.&apos; Transla-tional slip during plastic flow in these materials, according to Gallagher&apos; and Treuting,&apos; occurs on (111) planes. Recent work by Treuting&apos; indicates the direction of slip to be <1l0>. The present paper describes the plastic flow characteristics of germanium and silicon deformed by torsion. Torsional deformation was accomplished by twisting 1/4x1/4x2 in. specimens held in molybdenum grips and contained in an atmosphere of helium in a transparent quartz tube and heated by an external resistance furnace. The angular displacements were measured on a graduated circle with a pointer attached to the movable grip. Temperatures were measured with a chromel-alumel couple; the hot junction was within the quartz tube and in close proximity to the specimen. Photographs of samples of germanium and silicon twisted at 850" and 1180°C, respectively, are shown in Fig. 1. The germanium was twisted 230" per in. and the silicon 80" per in. These deformations are larger than those used in experiments to be described later and are presented only to emphasize the extensive plasticity of these materials. Germanium A single crystal specimen of germanium (n-type, 7 ohm-cm resistivity) with a (111) plane normal within 3" of the torsion axis, Fig. 2, was chemically polished with CP-4 solution" and then twisted 9" during the twisting of these specimens of germanium, the slip lines from the (lli) plane should have appeared in the four lateral faces instead of in only two. Perhaps the absence of rotational slip is brought about by the square cross-section. A cylindrical specimen would have a more uniform stress distribution in torsion than one with a square cross-section, and may deform by rotational slip. A specimen of germanium (n-type, 5 ohm-cm resistivity) twisted less than 8" per in. at 550°C, was cut to expose the (111) face 19" 28&apos; from the torsion axis, Fig. 4a. This face, after metallographic

Jan 1, 1956

By O. D. A. Pease, C. D. Young, C. H. Strand

In an effort to employ cast steel of a stronger structure than that found in the annealed steel casting, the possibilities of heat treatment which will increase the strength without materially decreasing the ductulity may be resorted to.

Jan 1, 1915

By B. M. Larsen

Jan 1, 1965

By H. N. Wolcott

AMONG the many cases of replacement of one mineral by another, that of quartz or silicates by pyrite, or even other sulphides, is not uncommon, but the reverse of this process does not appear to have been recorded, even if it has been observed. It, therefore, seemed to the writer that the case described below was worthy of record. FIG. I.-GROUND MASS OF CHALCOPYRITE (C) CONTAINING ROUNDED GRAINS OF PYRITE (P) SHOWING DIFFERENT DEGREES OF REPLACEMENT BY QUARTZ (Q), AND ALSO QUARTZ VEINLETS CUTTING THROUGH THE PYRITE. (PHOTOGRAPHED BY REFLECTED LIGHT.) The specimens described in this paper were obtained by R. B. Morton of Idaho Springs, Colo., from the Old Town Mine, in Russell Gulch, and are in the collection of Cornell University, where the writer studied them. In the rough, the specimens appeared to consist largely of chalcopy- rite, with some grains of tetrahedrite. The polished surface of some of

Jan 6, 1917

ALABAMA Alabama City.-Eddy, L. Altoona.-Cain, J. America.-Foreman, J. T. Anniston.-Foster, R. N. Ashland.-Sturdevant, J. C. Bessemer.-Ball, E. M. Calhoun, F. W. Maschmeyer, W. L. McKenzle, W. C., Jr. Birmingham.-Abbott, C. E. Aldrich, T. H. Aldrich, T. H, Jr. Ashton, J J.

Jan 1, 1923

By Owen F. Devereux

Two discrete types of microstructure me seen in cermets formed by the reaction: 4Al (liquid) + 3SiO2 (glass) — 2A12O3(a) + 3Si (solid) Relatively coarse-grained macroscopically isotropic specimens resulted from reaction with aluminum containing appreciable silicon, while macroscopically anisotropic fine-grained specimens were formed by reaction with aluminum low in silicon. Optical microscopy, electron microscopy, and X-ray diffraction suggest that the anisotropic material contains gross areas in which submicroscopic grains of a A12O3 are oriented along radial lines drawn from the specimen surface. These lines are presumed to originate at defects in an otherwise protecting surface layer. A unique cermet is formed by the reduction of high-silica glass by molten aluminum according to the reaction: 4A1 (liquid) + 3SiO2 (glass) — 2A12O3 (a) + 3Si (solid) The free-energy change accompanying this reaction is -150 kcal at 800°C; the volume change (volume of A12O3 and silicon minus volume of SiO2) is +6 pct. The reaction product, however, contains aluminum metal as well as Al2O3 and silicon because some of the product silicon is dissolved in the aluminum bath and is replaced by aluminum in the structure. The product is a hard gray solid that retains the external dimensions of the original silica article. The system has been studied in the past, the investigations culminating in patents to George1, 2 and Saw-chuk., The former emphasize that this reaction is but one of a relatively broad class of such systems, while the latter demonstrates that a marked improvement in the gross physical properties of the cermet can be obtained by dissolving appreciable quantities of silicon in the aluminum reactant. The system has also been studied by workers at Rolls Royce Ltd.,4-6 who have patented the addition of small quantities of arsenic, antimony, bismuth, or phosphorus to the reactant bath to SO impede the reaction that glass fibers may be metal-coated by immersion in molten aluminum.

Jan 1, 1969

By Richard A. Sheppard

Zeolites-crystalline hydrated aluminosilicates of the alkalis and alkaline earths-are important rock-forming constituents in sedimentary rocks and are potentially valuable industrial minerals. They have a framework structure that encloses interconnected cavities occupied by the relatively large cations and water molecules. The cations, chiefly sodium, potassium, and calcium, and the water have considerable freedom of movement within the structure and give the zeolite their cation- exchange and reversible-dehydration properties. Some zeolites have essential contents of barium, strontium, or magnesium. The basic structure

Jan 1, 1975

By P. Somasundaran, G. E. Agar

The role of calcium, phosphate, and fluoride species in determining the zeta potential of apatite in aqueous solutions was investigated in this study. The zeta potential of apatite was determined by streaming potential measurements over a wide range of concentrations of potassium nitrate, calcium nitrate, potassium dihydrogen phosphate, and potassium fluoride solutions at various pH values. While the addition of phosphate made the apatite surface more negative at all pH values, calcium caused a significant increase of the zeta potential only when the zeta potential was negative. Fluoride addition had only a minor effect on the zeta potential, but both negative and positive values were increased.

Jan 1, 1973