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By R. B. Yerxa, C. F. Green, H. O. Hofman

MASSACHUSETTS INSTITUTE OF TECHNOLOGY, In refining copper, the metal is melted down in a reverbera tory furnace in a more or less oxidizing atmosphere and then further subjected to an oxidizing smelting in order to eliminate the common impurities, most of which have a stronger affinity for oxygen than has copper. In these operations some of the copper is oxidized to cuprous oxide and dissolved by the metal bath. When the quantity of dissolved cuprous oxide has reached about 6 per cent, the metal is said to have been brought to " set-copper." A button-sample will show a depressed surface and, when broken, a single bubble at the apex of the depression; the fracture will be brick-red and dull. It is essential to carry the oxidation to this point in order to know that the impurities have been oxidized as far as it is possible under the given working-conditions. Nearly all the cuprous oxide of the set-copper is now reduced to the metallic state by poling, when "tough-pitch" copper will be obtained. A button-sample will show a flat surface. Upon breaking, it will be found that the former bubble has disappeared and that the fracture has become rose-colored and shows a silky luster. The quantity of cuprous oxide allowed to remain in the copper will vary with the impurities still present in the metal and with the degree of pitch that it is desired to reach. It is essential for the general physical and the mechanical properties of the resulting copper that such impurities as arsenic, antimony, bismuth, lead shall be present in the oxidized state, as they are

Jan 1, 1904

Jan 1, 1905

By Clarence A. Seyler

The technical difficulties of cutting thin sections of coal for examination by transmitted light have hitherto restricted the investigation of the important subject of the microstructure of coal to the few possessed of the requisite skill and time. Apart from this, the method fails with anthracites and other coals rich in carbon, owing to the opacity of the material. Occasional use of the method of polishing a surface, with or without etching, has been made, but it was not until Winter' published an account of his results that attention was seriously directed to the method. In May, 1923, a specimen of dull anthracite came into my hands; I tried Winter's method on it and the presence of megaspores and other vegetable structures became clearly visible. A preliminary notice was published by me;2 but I soon abandoned the use of Schulze's solution, having found that a mixture of chromic and sulfuric acids gave far better results. In the meantime Turner and Randall, in America, had independently developed the method of flame etching, as applied to anthracite, with great success. I have spent a year studying the method of chromic etching, which gives excellent results with bituminous coals and camels, as well as with anthracite. For anthracites, I have used the chromic method and Turner's method of flame etching, whichever was the more convenient or as a check one on the other. The polishing is done, according to metallurgical practice, by the use of a polishing machine and successively finer emery paper, followed by polishing on cloth moistened with a suspension of levigated green oxide of chromium, and a final rubbing on "selvyt" (a cotton velvet polishing cloth) moistened with alcohol. The polished sample is examined by reflected light with a 2/3 and 1/6 in. objective. Bituminous coals usually show considerable structure, and even anthracites show it faintly in places. The sample is then etched by immersion in a boiling solution made by adding 10 c.c. of concentrated sulfuric acid to 30 C.C. of a saturated solution of chromic acid; enough water is then added to dissolve

Jan 1, 1925

By Oliver Bowles

ALTHOUGH Oliver Bowles retired as chief of the nonmetal economics division of the Bureau of Mines last year, that retirement has not lessened his active interest in the field of nonmetallic minerals, in writing, nor in his hobby, cultivation of African violets. Excellent co-ordination of the timing of a professional meeting and a flower show permitted him on at least one occasion to attend technical sessions and take in the African violet exhibition which happily arrived simultaneously in one city. Dr. Bowles celebrated his seventieth birthday on Jan. 10, 1947, and

Jan 1, 1948

By T. Johnston, B. Cox

The results of oxidation and corrosion experiments on niobium in oxygen and steam at temperatures of 350° to 650°C, and in dilute sulphate solutions at 300°C are presented. The oxidation of niobium in oxygen can be explained in terms of a pre-transition period, which obeys an approximately parabolic rate law, and a post-transition period in which a more rapid linear rate is partially stifled by restriction of the gas flow due to the gvowth of the porous outer film. Due to changes in the porosity of the outer layers the restriction presented by the porous outel. film attains a limiting value. Subsequent oxidation obeys a linear rate law and shows an almost linear dependence of the rate on gas pressure. liltimately a second failure of the protective film may take place leading to a further acceleration in the oxidation rate. In water vapor the oxidation of niobium follows a parabolic rate law and does not show a transition to linear kinetics. The higher oxide, Nba05, was usually absent from the NbO/NbO2 film which was formed. The addition of a small partial pressure of oxygen to the water vapo3, resulted in accelerated oxidation according to the normal kinetics for oxidation in oxygen. The oxygen reacted preferentially with the niobium, and the protective oxide film was reformed when all the oxygen had been consumed. This behavior supports the theory that nucleation of Nb205 on the surface of the protective NbO/NbO2 film is the cause of the accelerated oxidation. After oxidation in steam at high-pressure Nb2Os was found in the protective film. The mode of formation of Nb2O5 under these conditions did not produce a change in kinetics, but was thought to explain the comparatively large dependence on pressure of the oxidation rate. The kinetics of oxidation in oxygenated aqueous solutions at 300°C were similar to those for oxidation in oxygen. A penetrating attack on niobium sheet may be related to the second breakaway observed by some investigators of oxidation in oxygen.

Jan 1, 1963

By AIME AIME

TOTAL shipments of iron ore from the Lake Superior district totalled 21,672,410 long tons in 1933, according to a compilation in Skillings' Mining Review. The producers ranked as follows in order of output shipped:

Jan 1, 1934

By J. R. Stack, H. H. Alexander

Prior to 1915, numerous attempts were made to treat tin concentrates in the United States, but for various reasons they were unsuccessful. Tin ore is said to have been found in nearly every state, but none of the deposits has proved to be of commercial importance. An annual output of a few hundred tons in Alaska is the only domestic production; hence any considerable production of tin in the United States must be from foreign ores. The most promising occurrence of tin was found in the Black Hills, S. Dak.; in the early development stage, it was called the Cornwall of America. Associated with the tin is tungsten The story is told that an exceedingly fine specimen of the Black Hills ore was sent to England to encourage stock promotion; the desired effect was produced until a skeptic chipped off a small piece, which the analysis showed to be wolframite. First Attempts at Smelting One of the first promising attempts at tin smelting in the United States was made by R. T. White at Bayonne, N. J., in 1903. Mr. White, after spending some time in England studying the methods of tin smelting, organized a company called the International Tin Co., and erected a plant to treat tin concentrates from the Straits of Malacca. About the time the plant was completed, the English Government placed an export duty of 40 per cent. ad valorem on tin concentrates exported to other than British smelters, which duty made it impossible to operate this plant so the enterprise was abandoned, As this export duty is still effective, the only source of tin-ore supply for the United States is the Bolivian concentrates. Bolivian Tin Concentrates Unlike the alluvial placer deposits, nearly all Bolivian tin occurs in lode deposits and some of the highest grade ores contain only a small

Jan 1, 1924

By Henry S. Rawdon

The relation between the course, or path, of the fracture of metals and alloys, produced in service or as a result of certain laboratory tests, and the crystalline units of which such materials are composed is of utmost importance. The fracture of normal material is, in general, intracrystalline, i.e., it consists of a break across the grains rather than of a separation between them. An interorystalline fracture indicates either that the metal is of very inferior quality or that the break occurred under very unusual conditions, e.g., at a very high temperature. The usual mechanical tests, when applied to metals of the type that breaks with an intercrystalline fracture, merely measure the coherence of adjacent grains for one another and reveal little as to the real properties of the metal itself. Even such a soft plastic substance as lead, under suitable conditions, may be rendered so weak and brittle that the metal can be easily crumbled into powder by the fingers although the constituent grains have lost none of the intrinsic properties of lead. Various erroneous explanations of this behavior of lead have appeared in the scientific literature, the change being described usually as an allotropic one. The importance, in an industrial sense, of a proper explanation of this type of the corrosion of lead justifies the description of the type of metal deterioration that follows. Corroded Lead Sheathing In Figs. 1 and 2 are shown two typical specimens of corroded lead sheathing selected from materials submitted to the Bureau of Standards for examination. Fig; 1 shows a section of the sheathing of an aerial cable; Fig. 2, that of the lead covering of a subterranean feeder-line of an electric light system. In this case the deterioration had proceeded to a much great'er extent than in the case shown in Fig. 1 so that certain portions of the metal could easily be crumbled into a coarse gray powder by the fingers. This was particularly true of those portions of the sheathing

Jan 1, 1921

By Henry M. Howe

The striking features of American Bessemer practice aré its large output and its low initial silicon and initial temperature. These are interdependent. Large outputs implies short blows and short intervals between blows. Short blows imply low silicon and fast blowing. Low silicon implies short intervals and fast blowing. Our blows are short because we have little silicon to remove, and because we remove it fast by supplying blast rapidly. We get enough heat even with little silicon, because our blows and the intervals between them are so short that relatively little heat escapes from our vessels. Were we to lengthen our intervals, or to blow more slowly, we would have to meet the increased loss of heat from our vessels, either by using more silicon, or by melting hotter, i.e., by burning more coke, in the blast-furnace or in the cupola. Finally, our short intervals imply powerful machinery, efficient organization, and extreme specialization and subdivision of labor, which can be profitable only when the output is large. Let, us now take these points up in more detail, first glancing at some examples of our large outputs, given in Table I., and of the composition of our iron. Output.—On presenting such results to some foreign metallurgists, I have been told, " Oh yes, we quite understand that. You really turn out no more steel than we do. As a matter of personal pride, your manager gets up a tremendous spurt for a day, or even a week, crowds on men wastefully, rushes through great quantities of metal, and then for months afterwards has to recuperate. The machinery has been strained ; the owner's money has been wasted ; the men have been prostrated—all to gratify the manager's vanity. Your average output is no larger than ours." Personal pride has, doubtless, played its part; without it we would still be savages, or apes, or mollusks, if you prefer. These baser motives are the mudsills of progress, the soiled roots of that growth of which civilization is the flower. Great outputs were made

Jan 1, 1891

By A. S. Richardson

THe conditions that make necessary the mechanical ventilation of the Butte mines of the Anaconda Copper Mining Go. are due to a number of causes, all of which are incidental to the depth at which mining operations are now carried on, The main object to be accomplished, of course, is the reduction of the temperature and humidity of the air in the working places. Ventilation fans, both surface and underground, have been used for many years, but increasing depth has made the problem much more difficult. Further improvement in both ventilation equipment and methods, therefore, became necessary; and it is the purpose of this paper to describe the work planned and done under the improvement program. The mines of the district have been frequently described in various technical publications, so a description is unnecessary here. From a mine-ventilation viewpoint, compared with coal-mine ventilation systems, the problem is complicated by the fact that the workings to be ventilated are situated on a large number of steeply dipping veins which frequently intersect and are faulted, and also by the fact that the extent, or existence, of orebodies is not definitely known in advance of actual development work. For these reasons ventilation work cannot be planned in advance of actual operations, nor can such regular systems of ventilation as are used in working the more uniform and continuous bodies of coal be developed. When operations are conducted at a normal rate, about 10,000 miners are employed on two shifts, so that about 5000 men will be underground at one time. But as ventilation is necessary to reduce high temperature and humidity due, mainly, to natural causes, the quantity of air per man per minute is not a governing consideration in determining ventilation requirements. Most important among the numerous sources of heat and humidity in the mines are: heat generated during decay of mine timber; heat and humidity given off by mine rock and water; heat generated by oxidation of sulfide minerals; heat given off by electrical equipment; heat generated by mine fires (in certain localities).

Jan 1, 1923

By A. S. Richardson

THe conditions that make necessary the mechanical ventilation of the Butte mines of the Anaconda Copper Mining Go. are due to a number of causes, all of which are incidental to the depth at which mining operations are now carried on, The main object to be accomplished, of course, is the reduction of the temperature and humidity of the air in the working places. Ventilation fans, both surface and underground, have been used for many years, but increasing depth has made the problem much more difficult. Further improvement in both ventilation equipment and methods, therefore, became necessary; and it is the purpose of this paper to describe the work planned and done under the improvement program. The mines of the district have been frequently described in various technical publications, so a description is unnecessary here. From a mine-ventilation viewpoint, compared with coal-mine ventilation systems, the problem is complicated by the fact that the workings to be ventilated are situated on a large number of steeply dipping veins which frequently intersect and are faulted, and also by the fact that the extent, or existence, of orebodies is not definitely known in advance of actual development work. For these reasons ventilation work cannot be planned in advance of actual operations, nor can such regular systems of ventilation as are used in working the more uniform and continuous bodies of coal be developed. When operations are conducted at a normal rate, about 10,000 miners are employed on two shifts, so that about 5000 men will be underground at one time. But as ventilation is necessary to reduce high temperature and humidity due, mainly, to natural causes, the quantity of air per man per minute is not a governing consideration in determining ventilation requirements. Most important among the numerous sources of heat and humidity in the mines are: heat generated during decay of mine timber; heat and humidity given off by mine rock and water; heat generated by oxidation of sulfide minerals; heat given off by electrical equipment; heat generated by mine fires (in certain localities).

Jan 1, 1923

By W. R. Bean

Probably few, if any, of the many serious problems confronting malleable foundries have been more difficult of solution than the question as to why malleable that is ductile, black in fracture, and normal in all respects before galvanizing should, by that process, be rendered brittle, brilliantly crystalline or "white" in fracture, and of low resistance to shock. So far as we are aware, the technical literature contains no data or discussions on this subject, except two referencesl,2 of a general character. It is apparently a question that every one concerned, producer and consumer alike, has been willing to evade as far as possible. Various theories as to the cause of the deterioration have been given but such checking of these theories as we have done indicates that there was no sound basis for most of them. This work on the galvanizing of malleable was first undertaken in 1916, and has continued until the present time. We now feel that for all practical purposes we have reached a solution and are glad to be able to offer it in a form that can be readily applied to production processes. It is impossible to give here a detailed account of the early work done on this problem. A great number of tests were instituted and an enor-

Jan 1, 1923

By W. R. Bean

Probably few, if any, of the many serious problems confronting malleable foundries have been more difficult of solution than the question as to why malleable that is ductile, black in fracture, and normal in all respects before galvanizing should, by that process, be rendered brittle, brilliantly crystalline or "white" in fracture, and of low resistance to shock. So far as we are aware, the technical literature contains no data or discussions on this subject, except two referencesl,2 of a general character. It is apparently a question that every one concerned, producer and consumer alike, has been willing to evade as far as possible. Various theories as to the cause of the deterioration have been given but such checking of these theories as we have done indicates that there was no sound basis for most of them. This work on the galvanizing of malleable was first undertaken in 1916, and has continued until the present time. We now feel that for all practical purposes we have reached a solution and are glad to be able to offer it in a form that can be readily applied to production processes. It is impossible to give here a detailed account of the early work done on this problem. A great number of tests were instituted and an enor-

Jan 1, 1923

By J. E. Johnson

Discussion of the paper of Mark A. Amnion, presented at the Cleveland meeting October, 1913, and printed in Bulletin No. 70, October, 1913, pp. 1167 to 1 79. J. E. JOHNSON, JR., Ashland, Wis.:-Mr. Amnion's paper is of great value and it is not with any desire to reflect. on it that I wish to make some comments on the use of the scleroscope. We obtained one on trial some months ago and made very extensive tests with it, but without getting very satisfactory results. The readings on good car-wheels and bad ones were just about the same, but the factor in its use most likely to produce erroneous results is a variation in the thickness of the specimen being tested. In order to find out something on this subject we cut a thin disk, about -1,: in. thick, off a brass rod; then one 0.25 in. thick, and another about 1 in. thick, put the surfaces of all in about the same condition and tested them with the scleroscope. The readings varied widely; the resilience of the anvil evidently entered to a very high degree on thin pieces. By putting a soft cushion between such a thin specimen and the anvil, and forcing it up against the tube, the softness of the cushion cut off the resilience of the anvil and the results were more like those of the thick specimens. After a thickness of 1 in. was passed, the specimen seemed to have mass enough so that the resilience of the anvil no longer played an important part, and above that thickness results on different materials would be comparable, even though the thicknesses differed. But in order to get comparable results on thin specimens the thickness of those being tested should be the same. I should like to ask how the variations introduced in this way were overcome, so as to get strictly comparable results. Mr. AMMON :-.I have not had much experience in that, but the scleroscope is simply an indication of the surface harden-

Dec 1, 1912

By R.J. Anderson

Roughly, a crack in a casting may be considered, for the moment, to be due to fracture of the alloy resulting from the stress set up by the contraction in volume on passing from the liquid to the solid state. Cracks may be external or surface, internal or deep-seated, or incipient or so-called strain cracks. Draws may appear as depressions, unevenness, and "pinching in" of the surface of a casting. Roughly, draws are due to contraction in volume and are governed largely by the same factors as cracks. A casting may be cracked, however, without being drawn. Shrinkage is a foundry term and refers to the contractio~l in volume of a metal or alloy on passing from the liquid to the solid state. Patternmaker's shrinkage is the total contraction in volume (including liquid, solidification, and solid shrinkage) that occurs when an alloy is poured into a mold. The contraction in volume of aluminum is one of the principal factors affecting the occurrence of cracks, as will be shown later, and the question of shrinkage and its control requires careful study in any treatment of cracking in castings. In the case of sand and die castings, cracks have been attributed to a number of causes, but in the case of most light aluminum alloys, they are due to the large contraction in volume on freezing and the lack of its regulation or control. The most important factors are: (1) Contraction in volume; (2) composition of alloy; (3) quality of melting charge; (4) design of casting; (5) method of molding; (6) hardness of ramming; (7) method of gating; (8) hardness and characteristics of cores; (9) chills; (10) risers; (11) melting temperatures; (12) furnace used for melting; (13) pouring temperatures; (14) inclusions in alloys; (15) hot shortness of alloys; and (16) physical properties of alloys at high temperatures. Of these, the first, second, third, and eleventh to sixteenth involve ascertainable metallurgical facts; the remainder are largely matters of opinion, judgment, and technical knowledge of men experienced in the production of castings.

Jan 1, 1923

By R. J. Anderson

Roughly, a crack in a casting may be considered, for the moment, to be due to fracture of the alloy resulting from the stress set up by the contraction in volume on passing from the liquid to the solid state. Cracks may be external or surface, internal or deep-seated, or incipient or so-called strain cracks. Draws may appear as depressions, unevenness, and "pinching in" of the surface of a casting. Roughly, draws are due to contraction in volume and are governed largely by the same factors as cracks. A casting may be cracked, however, without being drawn. Shrinkage is a foundry term and refers to the contractio~l in volume of a metal or alloy on passing from the liquid to the solid state. Patternmaker's shrinkage is the total contraction in volume (including liquid, solidification, and solid shrinkage) that occurs when an alloy is poured into a mold. The contraction in volume of aluminum is one of the principal factors affecting the occurrence of cracks, as will be shown later, and the question of shrinkage and its control requires careful study in any treatment of cracking in castings. In the case of sand and die castings, cracks have been attributed to a number of causes, but in the case of most light aluminum alloys, they are due to the large contraction in volume on freezing and the lack of its regulation or control. The most important factors are: (1) Contraction in volume; (2) composition of alloy; (3) quality of melting charge; (4) design of casting; (5) method of molding; (6) hardness of ramming; (7) method of gating; (8) hardness and characteristics of cores; (9) chills; (10) risers; (11) melting temperatures; (12) furnace used for melting; (13) pouring temperatures; (14) inclusions in alloys; (15) hot shortness of alloys; and (16) physical properties of alloys at high temperatures. Of these, the first, second, third, and eleventh to sixteenth involve ascertainable metallurgical facts; the remainder are largely matters of opinion, judgment, and technical knowledge of men experienced in the production of castings.

Jan 1, 1923

By H. S. Rawdon

One of the most vital problems in the manufacture of steel at present is the occurrence of the defects that have been popularly termed "snow flakes," "flakes," or "scabs." Particularly is this the problem of many manufacturers who, during the past 2 yr., have undertaken large-scale production for the first time. A study of the microstructure of such defective material throws considerable light upon the nature of these defects and is essential before measurcs may be taken for the elimination of the defects. Flakes do not appear to be found in the plain carbon steels; they have been found. however, in abundance in some of the simple alloy steels that are being used in such vast quantities; vie., nickel steel of the approximate composition, 0.40 carbon and 3.5 per cent. nickel, and in the chrome-nickel type. The present article summarizes the characteristic features of defective steel of the flaky type as they have been found by laboratory study of numerous specimens, and it aims to show the conditions within the metal that are favorable to the occurrence of this type of defect without entering into the details of mill practice (size of ingot, design of molds, rate of cooling, distribution of cooling stresses, etc.), all of which conditions appear to play a role in the production of these defects. MacrostrUctURe To one familar with flaky steel, the appearance of "snow-flakes" is unmistakable and is not to be confused with other types of defects. Figs. 1 to 6 show the appearance of fractures of steel showing this type of defect; the white silvery area, which always has the appearance of being of a very coarsely crystalline structure, in the specimen stands out in bold contrast to the darker background and readily justifies the use of the term "snow-flakes." Fig. 1 shows the appearance of the faces of the two halves of a nickel-steel forging that has been split to show the interior flakes. Fig. 2 is a nickel-steel bar (carbon 0.40 per cent.,

Jan 1, 1920

By Willard C. Lacy

Rather than attempting to present a summary of the many and highly varied papers that have been presented at this symposium on sampling and grade control, I will attempt to extract the general philosophy of analysis and approach, and attempt to identify the trend of future developments. First, the term "sampling" is used with its broadest connotations. A sample consists of a representative portion of a larger mass, and must represent the mass not only in the grade of contained metals or minerals, but also in all other respects in terms of mineralogy and mineral quality (1, 5), deleterious materials, recoverability of economic components, physical behavior, geophysical response (I), and even archaeological and environmental aspects (7, 11). The sample must be taken from a locality and in such a manner and quantity that it is representative of the larger rock mass. This calls for complete and accurate geological control and an understanding of the nature and distribution of the contained chemical and physical elements and a record of the effectiveness of the different sampling methods. Second, value of a given mass of ore material is based upon its profitability - the difference between recoverable value and costs to achieve recovery, beneficiation and sale. There is a strong movement in mining geology control toward more complete analysis in determining cutoff grades and in grade control, as illustrated by the kriging of metallurgical recovery factors as well as grade at the Mercur Mine (8). To achieve a "profit- ability factor" as a guide for economic mining practice requires further integration of: 1) the value of contained metal or mineral, 2) percentage recovery of values, 3) dilution of ore with waste rock, 4) addition to, or loss of value as a consequence of by-product materials or deleterious components, 5) cost of producing a saleable product plus mini- mum profit to justify the effort (cutoff), and 6) cost of land restoration (7, 11). All these parameters vary with the rock type, rock structure, mineralogy, depth, geometry, mining and metallurgical methods, but they must be sampled and analyzed if sampling and grade control are to reflect profitability. A wide variety of deposits has been presented at this symposium; each deposit with its own problems and special solutions. Deposits containing high unit-value components, e.g. precious metals and diamonds, present special problems in the obtaining of accurate samples and generally require statistical analysis control methods or may disregard or modify occasional high or occasional low values, based upon experience (12 ) Grade control may be accurate for the long term but may vary for the short term. Bulk sampling is always essential. Deposits containing metals or minerals with low unit value are very sensitive to transport costs, and they are often very sensitive to small amounts of deleterious components or differences in physical or chemical behavior. Problems of sampling and grade control change with the genetic type of deposit, with the stage of deposit development and with the size of the information base. Precious metal epithermal deposits (2, 6, 8), because of rapid vertical zonation and erratic lateral distribution of values, have always been difficult to evaluate and maintain grade control and ore reserves. On the other hand, evaluation and grade control are relatively easy in bulk-low- grade deposits (4, 13). However, these deposits generally have a low margin of profit and are sensitive to mining and beneficiaton costs, price fluctuations and political costs. Industrial mineral deposits (5) often must be evaluated on the basis of their behavior, rather than by chemical analysis. Environmental impact generally increases with the scale of the operation, but certain elements or minerals have especially high impact effects (7, 11). In the exploration phase there is no production control of sampling procedures and careful geological observations are particularly essential. The greatest number of problems is related to the oxidized outcrop where the chemical environment of the ore body has changed and the contained values may have been enriched, depleted or values left unchanged (2, 6). Present evidence suggests that gold values may be very mobile under certain conditions (2, 6) and stable under others. Everything must be sampled in detail. Principal values and by-product or deleterious elements may vary dependent upon their position within the soil profile. Such factors as geomorphic position, erosion rate, vegetation, climate, etc., may affect the interpretation (1, 3). During the development phase it is equally easy to overtest, to have "paralysis by analysis," as to undertest (3, 6). Bulk samplng and testing are

Jan 1, 1985

By F. X. Spiegel, D. Bardos, Paul A. Beck

Ti6NileSi7)G is known to be cubic, with 116 atoms in the unit cell. In the present work four new G sili-cides were found with other transition elements and five G germanides. The titanium-group elements are very efficient in forming G phases. The vanadium -group elements are somewhat less efficient, and the chromium-group elements do not form any. Cobalt can replace nickel in most cases, but it is somewhat less efficient. Iron was not found to form any G phases. Germanium is somewhat less efficient than silicon. The (TiNiSi)E phase has been previously identified by Westbrook. However, its crystal structure has not been determined. In the present work the E phase was found to have an orthorhombic unit cell with lattice parameters a. = 7.02, bo = 5.18, co = 11.11A. A large number of other E phases were found at the same stoicheometric ratio in ternary systems of silicon and germanium with transition elements. Lattice parameters similar to those for TiNiSi were measured. The number of atoms per unit cell is estimated at 30 to 36. The vanadium-group elements are somewhat more efficient in forming the E phase than the titanium-group elements. Chromium-group elements were not found to form any E phases. Cobalt is somewhat less efficient than nickel, and iron is less efficient than cobalt. Germanium is not as efficient as silicon. ThE ternary silicide designated as G-phase was first identified by Beattie and versnyder1 and by Beattie and Hagel2 at the approximate composition TiNi2Si. Westbrook et al.' gave the composition as Ti2Ni7Sis. This phase was found to be fcc with a. = 11.201A and 116 atoms per unit cell. Beattie4 and more recently independently Hladishevskii, Kripyakevich, Kuzma, and Teslyuk5 were able to show that this structure is isotypic with MgeSi7CuLe and Th6Mn23. The latter structures had been determined by Florio, Rundle, and snow,' Nagorsen and Witte,7 and Bergman and Waugh.8 According to the crystal structure, Ti8Ni6Si7 may be considered as the ideal composition. The Russian investigators5 identified six additional ternary phases isotypic with Ti6Ni6Si7, in which titanium is replaced by Mn, V, Nb, Ta, Zr, and Hf, and one, namely MneNil6Ge7, in which germanium replaces silicon. They also found that Cr6Ni6Si7, which does not occur as a ternary phase, can be stabilized by replacing 1 at. pct of the Cr by V, Mn, or Ta. Another ternary silicide was found by Westbrook et al.3 at the composition TiNiSi, and it was designated by them as the E phase. The crystal structure of this phase has not been deter-

Jan 1, 1963

By W. M. Mobley

The coal industry in Alabama, centered in Birmingham, has pioneered coal-bene-ficiation practice in the United States. The nature of the coal seams and mining methods employed have necessitated use of equipment and methods best adapted to the local conditions. Although all of the 30 or more coal seams now being mined in the state receive beneficiation, only the three most important producers of coking coals, the Pratt, Mary Lee and Black Creek, are discussed in detail. Nature of the seams, washability characteristics and equipment used are given as examples of the extent of work and progress in this field. The coal seams in Alabama are relatively thin and pitching, making mining difficult and expensive. Most of them are characterized by thin partings of rock or shale in the seam itself, as well as laminations of bone and rash. Mechanical mining methods have increased the occlusions from roof and floor to such an extent that nearly all the coal mined in the state must receive some treatment before it can be put on the market. During the year ending Sept. 30, 1943,' 18,129,792 tons of coal were mined in the state and 14,364,177 tons, or 79.2 per cent, received treatment. Excluding from the total the 1,223,014 tons produced by small wagon mines and the hand-picked lump coal, the amount re- ceiving beneficiation would be more than 90.00 per cent. This is, by far, greater than in any other coal-producing state. The earliest record of coal beneficiation in Alabama was the installation in 1890 of an experimental Lurig washer by Alexander Cunningham, for the Sloss Iron and Steel Co. at its blast furnace in Birmingham.2 In 1894 the Jeffrey Manufacturing Co. introduced the English Robinson washer, a combination of a hydraulic classifier and centrifugal machine. Erskine Ramsay, who has contributed so much to the coal industry, saw its possibilities as well as its mechanical defects and soon had his inventive mind at work. He added a sludge tank of his own design, and many Robinson-Ramsay washers were installed in Alabama and other states. The Stewart jig appeared in 1900, followed by the Montgomery jig in 1910 and both have found extensive use. Increased interest in this field led to new designs, such as the American, Elmore, Burke and Faust. The first Baum-type Norton jig was operated in 1930 and within the last five years six large installations of this type have been made by the McNally-Pitts-burg, Jeffrey and Link-Belt Companies. Wet-washing tables were introduced in 1922 but not extensively used until recently. The two most popular types are the Deister-Overstrom and Deister Plat-O. The coal-cleaning equipment used in Alabama has been relatively simple, yet efficient, but as the amount of impurities in the raw coal has been increased by mechanical mining and labor costs have become higher, much interest has been shown in sand cones, froth flotation and

Jan 1, 1947