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J. E. JOHNSON, JR., New York, N. Y. (communication to the Secretary*).-The discussion of Mr. Henrich's paper took place at a meeting from which I had the misfortune to be absent, and has just come to my attention. I do not wish to let the subject pass without contributing to it a little information which has come into my possession. In 1912, I published a brief note in the Transactions on The Effect of Alumina in Blast-Furnace Slags, giving in tabular form three typical slags used in iron blast-furnace practice, one of them the high alumina slag of, which Professor Richards speaks. That table is reproduced herewith. TABLE 1.-Composition of Slays. 1 3 3 4 5 6 7 CaO by Neutral Ratio Ratio Ratio Al2z03, SiO2, Differ- Substan- Cat Ca0 a A1203 Ratio Per Per ence, ces, CaO Cent. Cent. Per Per Al2O3 + Sioz Sit: SiO2 Cecil_ Cent. Virginia practice 6.5 36.0 54.0 3.5 1.27 1.6S 1.50 Lake-ore practice 13.5 33.0 50.0 3.5 1.08 1.92 1.51 Special experiment... 36.0 24.7 36.8 3.5 0.59 2.90 1.44 It supplies what seems to me convincing evidence that, for the purposes of the iron blast furnace, alumina can be regarded only as a neutral substance, dissolving in the slag and materially altering its viscosity, but not affecting its chemical activity. In subsequent experience with charcoal furnaces, I found the same rule to hold; that the chemical effect of alumina could be disregarded, providing the ratio of the lime and magnesia to the silica were kept constant. This is exactly the experience which Messrs. Dwight and Mathewson had in copper- and' lead-smelting furnaces. I have never seen any evidence or argument adequate to support the contention of Professor Richards-that the alumina acted as a base in the charcoal iron furnace and as an acid in the coke furnace, and that the function of alumina in iron-furnace slags is inherently different from that in copper- and lead-furnace slags-and I am compelled to differ absolutely with his conclusions in that respect.

Jan 9, 1917

By Nelson Severinghaus

Mineral fillers have been defined as inert materials that are included in a composition for some useful purpose. Because this definition and the scope of this review are not specific- indeed, exceptions abound-accurate total statistics are unavailable. One source estimates the total production in the United States in 1971 at 5 million tons valued at $200 million, averaging $40.00 per ton. Included are a broad group of minerals-asbestos, barite, bentonite, calcium carbonate, clays, diatomite, feldspar, micas, silica, talc. Additional references will be made to synthetic mineral-derived fillers such as aluminum hydrate, precipitated calcium carbonate, and pyrogenic and precipitated silicas and silicates. A section on related uses at the end of this chapter covers absorbents and filters. Mineral fillers can be included in compounds to accomplish a variety of final results. Hardness, brittleness, impact strength, compressive strength, softening point, fire resistance, surface smoothness, electrical conductivity, and a host of other physical characteristics may be modified by the inclusion of fillers. These effects are the result of properties of the fillers, including chemical activity, hardness, particle size, shape and distribution, surface structure, color, density, and refractive index. To facilitate an overview of the mineral filler industry, this chapter will review the general usage of fillers, the inherent characteristics that intensify their utilization, and similarly their manufactured characteristics. Major using industries will then be examined in detail. Specific information on deposits and processing for industrial minerals will be found in the appropriate commodity chapter. The chart in Table 1, updated from the 3rd edition of Industrial Rocks and Minerals, illustrates the major mineral fillers (both natural and manufactured) and their more important end uses.

Jan 1, 1975

By Charles Hart

In this paper it is the author's intention to show the extent and character of foreign ores now known to be available; these deposits may be in active production or held in reserve until economic conditions may make them active. He hopes to show the relation existing between these ores and the American supply, and which of the former are now producing or will in turn come into production when our better ores have been exhausted. This phase of this discussion must of necessity include some data as to the present rate of consumption and a study of the changes we may expect here and abroad in the general steel trade and its sources of supply in raw materials. It is obvious that the occurrence of coal, ore and limestone in relation to one another and the proximity of a market are the elements in control of this feature of the problem. If the foregoing situation is favorable, all the other questions may be solved, for it is clear that with proper basic conditions finance, labor and operations will fall in line. We present a short outline of the present methods of carrying on the foreign iron ore trade, believing that it is of general interest in comparison with our own highly specialized methods, and that with the exhaustion of our better ores we will be compelled to seek a part of our supply abroad. A partial list of iron ores, with incomplete analyses (Table I), is added, to give a better understanding of the general situation and explain to some extent the reason for things being as they are in the iron and steel trade of the world and to help in bringing this paper to an informing conclusion. The question of the world supply of iron ores has been a subject for study on the part of geologists and engineers for many years, and found its best results in the Eleventh International Geological Congress, appropriately held at Stockholm, Sweden, in 1910. The proceedings are published in two volumes and are undoubtedly the best records available on this subject at the date of publication. It should be borne in mind, however, that much has happened in the 20 years since these figures were assembled. There is just as much known ore at present as at that time, minus the quantity consumed, plus newly discovered reserves. The World War had great effect upon this situation; during that time explorations were greatly reduced and the settlements after the

Jan 1, 1929

By F. D. Richardson

STAFF: Editor, Gerhard Derge Carnegie lnstitute of Technology Schenley Park Pittsburgh, Pa. 15213 Editorial Assistant, M. A. Redmerski Production Editor, Otto T. Johnson THE METALLURGICAL SOCIETY: Jack H. Scoff, President; Richard C. Cole, Past-President; Harold 0. Emerick, President-Elect; Ralph L. Hennebach, Treasurer; Robert W. Shearman, Secretary; Donald A. Parks, Assistant Secretary; Leslie S. Wilcoxson, Assistant Secretary. PUBLICATIONS COMMITTEE OF THE METALLURGICAL SOCIETY: R. E. Lund, Chairman; T. E. Dancy, H. O. Emerick, P. R. Gouwens, R. E. Grace, J. H. Jackson, H. H. Johnson, A. E. Lee, Jr., R. R. Nosh, R. D. Pehlke, and Paul Queneau. Review and selection of manuscripts is under the supervision of the following Publications Committees: Extroctive Metallurgy Division: R. E. Grace, Choirmon; G. M. Bell, D. W. Bridges, J. M. Cigon, G. W. Heoly, T. A. Henrie, R. D. (Holli-doy, C. E. O'Neill, C. S. Somis, A. W. Schlech-ten, and Charles Shull. Iron and Steel Division: R. D. Pehlke, Choirmon; T. P. Floridis, Arnulf Muon, G. R. St. Pierre, E. T. Turkdogan, L. H.Von Vlock, and J. M. Uys. lnstitute of Metals Division: H. H. Johnson, Jr., Chairman; J. B. Clark, Vice Choirmon; M. R. Achter, G. F. Bolling. J. O. Brittoin, G. P. Conard, II, R. S. Davis, L. A. Girifolco, G. T. Hohn, J. P. Hirth, L. Himmel, G.T.horn, George Krauss, J. D. Livingston, R. D. Manning, H. M. Otte, S. V. Rodcliffe, R. E. Reed-Hill, H. C. Rogers, E. ScaIa, O. Sherby, M. T. Simnad, G. R. Speich, E. A. Steigerwald, R. A. Swolin, W. A. Tiller, W. R. Upthegrove, J. B. Wagner, Jr., Derek Wolton, H. W. Weart, W. W. Webb, and D. Published seven times yearly in February, March, April, June, August, October, and December by the American lnstitute of Mining, Metallurgical, and Petroleum Engineers, Inc., 345 East 47th Street New York, N. Y. 10017. Telephone PLAZA 2 -6800. Subscription $30 per year for non-AtME members m United States and North, South, and Central America; $32, foreign; $7.50 for AlME members Single copies, $6.00, single copier foreign, $6.50. The AiME is not responsible for any statement made or opinion expressed in its publications . . . Copyright 1964 by the American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. . . . Registered cable address, AiME New York Indexed in Engineering Index, Industrial Arts Index, and Chemical Abstracts. Second dost postaas poid ot New York, N. Y.,ond Ann Arbor, Mich. Volume 230, Number 6.

Jan 1, 1964

Four years of intensive exploration effort by Newmont Mining Corp. came to a climax May 27 in Carlin, Nevada, when local, state and federal officials joined with company officers at a dedication ceremony saluting the start-up of the firm's wholly- owned subsidiary, Carlin Gold Mining Co. Before an invited audience at the plant site, Newmont's President Plato Malozemoff and Nevada's Senator Howard D. Cannon pushed a lever and watched the new melting furnace rotate until a brilliant orange-red stream of molten gold poured forth from its mouth. Two 1200-oz bricks of bullion were poured that day, and they are the first of many that will lift this mine into the number two slot among U.S. gold producers and fourth among all gold mines on the North American continent. Although Newmont Mining first entered the gold mining business in 1929 in Grass Valley, California, the Company had operated no gold producers since the well-known Government directive L208, issued in 1942, closed down U.S. gold mines for the duration of World War 11. Now it is back in the business in a big way-a $10 million mine and plant capable of producing 200,000 oz. per year. All the gold from the Carlin operations is earmarked for the U.S. Mint in San Francisco.

Jan 7, 1965

By Charles D. Hoyt

T IME studies and cost accounting were combined to increase the efficiency of the overall mining method and thereby reduce costs at the Titania mine of the National Lead Co. in southern Norway about 70 miles southeast of Stavanger. From these studies a more effective drilling system was developed, standards were adopted for setting base pay rates, shrinkage stoping was abandoned for open stoping, a new mechanical loading chute was adopted, and the loading and haulage system was changed. Ore minerals at the Titania mine are ilmenite and magnetite; gangue minerals are plagioclase and hyperstene with accessory minerals of biotite, pyrite, chalcopyrite, and spinel. The average content of the ore is 17 pct TiO2 and from 20 to 25 pct iron. The ilmenite crystals contain microscopic lamels of hematite, making it impossible to obtain a high TiO2 content in the concentrate. An ilmenite concentrate with 44 pct TiO2 and 36 pct Fe, and a magnetite concen-

Jan 9, 1950

By Charles T. Holland, David A. Olsen

Considerable work has resulted in the development of a formula by which the strength of coal pillars for an L to T ratio of up to 12 may be estimated. One of the factors involved in this formula is the coefficient of friction between the coal pillar and the adjacent rock with which it is in contact. This paper presents the results of studies on sandstone, limestone, shale and coal and the coefficient of friction between coal and the other three under wet and dry conditions. With the coefficients of friction thus determined and the use of results obtained earlier by Meikle and Holland, it seems probable that coal pillar strength may be more closely estimated. Several investigators1-3 have found that the com-pressive strength of cubical coal specimens can be correlated by an equation such as

Jan 1, 1969

By A. O. Dady

PRODUCERS of both bituminous and anthracite coal have for many years been worrying about the gradually decreasing consumption of their product in the United States. Twenty years ago production had climbed to a peak of 569,000,000 tons of bituminous and around 90,000,000 tons of anthracite. In 1939 it was about 393,000,000 tons of bituminous and 51,000,000 tons of anthracite. This does not mean that the country is using less polver than it did twenty years ago, or that we are living in colder buildings. As a matter of fact, about three times as much electric power is now being consumed as in 1920. In general two factors are responsible for the drop in coal consumption: (1) greater efficiency in the use of coal, and (2) increased competition from hydro power, internal-combustion engines, and substitution of oil and gas for coal in conventional furnaces. As to the first factor, it took 3 Ib. of coal to generate a kilowatt-hour of electricity in central stations in 1920 and it takes 1.4 Ib. now; it took about 175 Ib. of coal in railroad locomotives to haul 1000 long tons a mile in 1920 where it talces about 120 lb. now: and marked economies have also been made in the use of coal in steel plants: in by-product coke ovens, and in other large uses. As to the second factor, three times as much electricity is produced from water power now as was produced in 1920; three times as much oil is being consumed in various ways; and likewise, the consumption of natural gas has tripled- whereas coal consumption in the same period has dropped by 40 per cent

Jan 1, 1941

C. R. CORNING, Chairman. ADOLPHE E. BORIE, First Vice-Chairman. THOMAS T. READ, Secretary, Woolworth Bldg., New York, N. Y. Vie-Chairmen. JOHN H. ALLEN, GEORGE M. COLVOCORESSES, RICHARD M. ATWATER, JR., ROBERT PEELE, GEORGE D. BARRON, CHARLES P. PERIN, A. CHESTER BEATTY, JOSEPH A. VAN MATER, J. PARKE CHANNING, ARTHUR L. WALKER. D. C. Bard, Howard Eckfeldt. Philip N. Moore, W. de L. Benedict, R. C. Gemmell, T. H. O'Brien, John C. Branner, F. Louis Grammer, James J. Ormsbee. Palmer Carter, Ernest A. Hersam, Edward W. Parker, Allen J. Clark, Edwin C. Holden, John B. Porter, F. Crabtree, William L. Honnold, R. DI. Raymond, George G. Crawford, Reginald E. Hore, Robert H. Richards, O. C. Davidson, C. Colcock Jones, LeRoy Slash, E. V. D'Invilliers, Eugene P. Kennedy, Frederick H. Sexton, James S. Douglas, Chester F. Lee, Henry L. Smyth, Walter Douglas, Richard S. McCaffery, F. W. Traphagen, Howard N. Eavenson, James F. McClelland, Elton W. Walker. Milton H. McLean, The Chairman of the Committee on the eve of his departure frog -,he country for an extended stay, addressed the following letter t ,he President of the Institute NEW YORK, N. Y., APRIL 19, 1913.

Jan 5, 1913

By F. G. Loper

Simulation as a mathematical technique is not new. However, recent increases in digital computer speeds and the ease of programming with languages such as Fortran have centered a good deal of attention around simulation in the last few years. By ignoring all but the relevant characteristics of a process, a mathematical simulator may be constructed which, when fed operating data, should react as the process would. The output becomes numbers, instead of tons, however. Thus, a trial-and-error operation of such a simulator will permit management to study a major system change at little cost.

Jan 1, 1967

Discussion of the paper of MANUEL EISSLER, presented at the New York meeting, February, 1915, and printed in Bulletin. No. 9.5, November, 1914, pp. 3661 to 2703. J. W. RICHARDS, So. Bethlehem, Pa.-I do not see in the paper a description of the Mabuki hearth as used for ore smelting. I noticed it described for concentrating matte, but I believe the older Japanese process was to use it for-smelting directly, by a pyritic smelting and Bessemerizing all in one operation, in the same simple hearth apparatus. There is a monograph published in German, on Copper-Ore Smelting in the Mabuki Hearth. At Ashio the practice of injecting bituminous coal at the, tuyères is noteworthy. It is very interesting to see two men load little cartridges on the end. of an iron rod with bituminous coal, and push them into the furnace tuyères, and with a piston inject 2 or 3 lb.. of bituminous

Jan 5, 1915

Separates of all the Technical Publications published in 1930 are available at Institute headquarters. All the papers are on file in public, university and technical libraries, and when so indicated in the list, may be found in the TRANSACTIONS. Copies of these papers have been mailed to those members of the Institute who are registered in Classes A-Mining Methods; B-Milling and Concentration; C-Iron and Steel Division; D-Non-ferrous Metallurgy; E-Institute of Metals Division; F-Coal Division; G-Petroleum Division; H-Non-metallic Minerals; I-Mining Geology; K-Mining Administration; L-Geophysical Prospecting, respectively. Other members may obtain copies by writing to the Secretary. Additional copies are sold at the rate of 1 cent per page; minimum charge, 25 cents. METAL MINING TECH¬ NICAL PUBLI- TITLE AUTHOR MEETING TRANS CATION VOLUME No. AND PAGE* 264-A.29. Quicksilver Industry in 1929. Im- L. H. Duschak San Francisco T30, 283, 312 provements in the Metallurgy of C. G. Maier and Oct., 1929 Quicksilver and Symposium on The others Present Status of the Quicksilver Industry (With Discussion) (37) 271-A.30 Observation on Ground Movement R. E. Palmer New York T30,168 and Subsidences at Rio Tinto Feb., 1930 Mines, Spain (20) 274-A.31 Development and Installation of the C. L. Berrien New York T30, 139, 166 Hawkesworth Detachable Bit (29) . Feb., 1930 276-A.32 Protective Measures Against Gas O. A. Glaeser New York T30, 129, 187 Hazards at United Verde Mine (11) Feb., 1930 287-A.33 Use and Cost of Compressed Air (12) R. S. Lewis New York Feb., 1930 314-A.34 Miami Copper Company Method of F. W. Maclennan New York T30, 39, 80 Mining Low-grade Orebody (44) Feb., 1930 319-A.35 How Human Beings Respond to W. J. McConnell New York Changing Atmospheric Conditions Feb., 1930 (9)

Jan 1, 1930

ALABAMA Anniston.-Bretz, J A Carnngton, F G Gerber, A B Ashland -Barton J Sturdevant, J C Bessemer -Abbott, C E Ball, T L Ferguson, V Salmon, H S Schaber, C F Thompson, N E Whatley, W J Birmingham.-Adams, J H -Aldrich, T H Aldrich, T H , Jr ALASKA Anchorage -Dyer, B W. Parker, H C Smith, S S Chichagof.-Baumann, H N , Jr Copper River.-Douglass, W C Cordova.-Hazelet, G C Fairbanks -Davis, J A Hyder -Pitt, D L Juneau -Jackson, G. T Murphy, R E R..11 ti At i

Jan 1, 1923

By L. S. Darken

Measurements of the electrical conductivity, the thermal electromotive force, and the deviation from stoichiometry by thermogravimetry were made on ferrous oxide (wüstite) single crystals as well as on poly-crystalline samples in the temperature range of -900" to 1330°C. In the region defined by T 2 1000°C and 1.05 5 O/Fe 5 1.10 the electrical conductivity was shown to be proportional to the sixth root of- the oxygen partial pressure and to be linearly dependent on the deviation from stoichiometry. The absolute Seebeck coefficient of single and polycrystalline wüstite was shown to be independent of temperature in the above region and a p to n transition of the Seebeck coefficient was observed at O/Fe = 1.09 in polycrystalline wüstite. Analysis of the results showed that the predominant defects in wüstite in the above region were doubly ionized cation vacancies. The analysis also ruled out the existence of complexes of the type postulated by Roth, except that below 1000°C there is some evidence of 'association of defects. Of the three oxides of iron (FeO, Fe3O4, Fe2O3) only FeO (wüstite) can exist within a wide range of the ratio O/Fe. This has been shown by several investigations of the phase diagram using for instance chemical analysis of quenched samples'-4 or thermogravimetric measurements. 5,8 Darken and Gurry's1 data for example in the temper- ature range 1100o to 1400°C show that the lowest O/Fe ratio obtainable for FeOl +. is about 1.045 and that the existence range extends to O/Fe = 1.20 at 1400oC. On the basis of detailed analysis of thermogravimetric measurements made by Vallet and Raccah6 the existence of three varieties of wüstite at elevated temperatures was suggested by these authors and by Kleman. It is well-established that wüstite has a NaCl structure with vacant cation sites.3, 8 From a neutron-diffraction study of wüstite samples quenched to room temperature Roth9 concluded that defects in wüstite are mostly complexes composed of two cation vacancies and one interstitial cation in a tetrahedral site. The atomic arrangement in the vicinity of such a defect is similar to that in magnetite, where each occupied tetrahedral site is surrounded by four vacant octahedral positions disposed at the corners of a tetrahedron, so arranged that each vacancy is shared by two tetrahedral cations. Thus there is an average of two vacancies per interstitial. Recent X-ray diffraction measurements made by Smuts10 on quenched wüstite samples confirmed the results of Roth's neutron-diffraction experiments. Roth's model of defects in FeO can be regarded as a solid solution of Fe3O4 in FeO; salmon1' used this defect model to calculate the activity of Fe3O1 in FeO at high temperature and claimed good agreement with the results obtained experimentally by Darken and Gurry.' Each missing cation in wüstite is accompanied by two trivalent cations, thus preserving charge neutrality. The "holes" which differentiate between the Fe 2+ and Fe3' states of the ions in octahedral positions can overcome the attractive field of the cation vacancies, and are then free to move through the crystal as charge carriers. A similar picture holds for COO, NiO, andMnO.l2, 13 Localization of the charge carriers in transition

Jan 1, 1968

By D. S. Tannhauser, I. Bransky

Measurements of the electrical conductivity, the thermal electromotive force, and the deviation from stoichiometry by thermogravimetry were made on ferrous oxide (wüstite) single crystals as well as on poly-crystalline samples in the temperature range of -900" to 1330°C. In the region defined by T 2 1000°C and 1.05 5 O/Fe 5 1.10 the electrical conductivity was shown to be proportional to the sixth root of- the oxygen partial pressure and to be linearly dependent on the deviation from stoichiometry. The absolute Seebeck coefficient of single and polycrystalline wüstite was shown to be independent of temperature in the above region and a p to n transition of the Seebeck coefficient was observed at O/Fe = 1.09 in polycrystalline wüstite. Analysis of the results showed that the predominant defects in wüstite in the above region were doubly ionized cation vacancies. The analysis also ruled out the existence of complexes of the type postulated by Roth, except that below 1000°C there is some evidence of 'association of defects. Of the three oxides of iron (FeO, Fe3O4, Fe2O3) only FeO (wüstite) can exist within a wide range of the ratio O/Fe. This has been shown by several investigations of the phase diagram using for instance chemical analysis of quenched samples'-4 or thermogravimetric measurements. 5,8 Darken and Gurry's1 data for example in the temper- ature range 1100o to 1400°C show that the lowest O/Fe ratio obtainable for FeOl +. is about 1.045 and that the existence range extends to O/Fe = 1.20 at 1400oC. On the basis of detailed analysis of thermogravimetric measurements made by Vallet and Raccah6 the existence of three varieties of wüstite at elevated temperatures was suggested by these authors and by Kleman. It is well-established that wüstite has a NaCl structure with vacant cation sites.3, 8 From a neutron-diffraction study of wüstite samples quenched to room temperature Roth9 concluded that defects in wüstite are mostly complexes composed of two cation vacancies and one interstitial cation in a tetrahedral site. The atomic arrangement in the vicinity of such a defect is similar to that in magnetite, where each occupied tetrahedral site is surrounded by four vacant octahedral positions disposed at the corners of a tetrahedron, so arranged that each vacancy is shared by two tetrahedral cations. Thus there is an average of two vacancies per interstitial. Recent X-ray diffraction measurements made by Smuts10 on quenched wüstite samples confirmed the results of Roth's neutron-diffraction experiments. Roth's model of defects in FeO can be regarded as a solid solution of Fe3O4 in FeO; salmon1' used this defect model to calculate the activity of Fe3O1 in FeO at high temperature and claimed good agreement with the results obtained experimentally by Darken and Gurry.' Each missing cation in wüstite is accompanied by two trivalent cations, thus preserving charge neutrality. The "holes" which differentiate between the Fe 2+ and Fe3' states of the ions in octahedral positions can overcome the attractive field of the cation vacancies, and are then free to move through the crystal as charge carriers. A similar picture holds for COO, NiO, andMnO.l2, 13 Localization of the charge carriers in transition

Jan 1, 1968

By R. N. Zitter

PRESENT work was done in connection with a program for obtaining a low energy gap semiconductor suitable for photodetection. The inter-metallic compound InSb, which is now being in-

Jan 1, 1959

By Richard J. Fruehan

ThE thermodynamic activities of nickel and chromium in liquid Ni-Cr alloys have not been previously reported. There have been several investigations on the solid alloys.1-3 In the present investigation the activity of chromium in liquid Ni-Cr alloys at 1600° C was determined by the use of the following galvanic cell, The use of galvanic cells employing solid oxide electrolytes for determining the activity of metals in solid alloys was first demonstrated by Rapp and Maak4 on Cu-Ni alloys between 700° and 1000°C. Recently Schwerdtfeger5 tested the performance of the ZrO2(CaO) electrolyte at 1600°C and found it satisfactory for oxygen pressures as low as 10"12 atm. He also demonstrated the use of solid oxide electrolytes for determining the activities in liquid metal systems in measuring the activity of manganese in Fe-Mn alloys at 1500°C. Extensive investigations have been carried out in this laboratory, exploring the oxygen partial pressure lower limit at which ZrO2(CaO) electrolyte can be used satisfactorily in oxygen galvanic cells at 1600°C. In a paper to be published at a later date,9 it is demonstrated conclusively that ZrO2(CaO) exhibits insignificant electronic conductivity at oxygen pressures down to about 3 x 10"13 atm which is lower than the oxygen partial pressure in equilibrium with Cr-Cr2O3 at 1600°C. Therefore, the activity of chromium can be related to the measured reversible electromotive force of the cell in the present investigation since no electronic short circulating will occur. Fig. 1 is a schematic diagram of the cell used. The Cr-Cr2O3 electrode was made of equal weights of chromium and Cr2O3 powders which were mixed and packed into a recrystallized alumina crucible. A Pt-wire lead was embedded into the Cr-Cr2O3 compact to insure good contact. A ZrO2(CaO) crucible, supplied by the Zirconium Corp. of America, contained the Ni-Cr melt equilibrated with solid Cr2O3. The ZrO2(CaO) crucible was placed on the Cr-Cr2O3 electrode and additional Cr-Cr2O3 mixture was packed around it. Contact with the Ni-Cr alloy was made with a Cr2O3 tube, which is a weak electronic conductor. A platinum wire lead was attached to the Cr2O3 tube. The galvanic cell was lowered slowly into the hot zone of the furnace tube in order to avoid too large a thermal shock which could break the ZrO2 (CaO) crucible. The furnace was con- tinuously flushed with purified argon during the experiment. The temperature was measured with a Pt-Pt/10 pet Rh thermocouple and maintained at 1600° ± 5°C. The electromotive force was measured with a recording potentiometer. The furnace was turned off when measurements were being made in order to avoid induction effects and the reversibility of the cell was demonstrated in the usual manner. The electromotive force was measured several times over a period of approximately 1 hr. During that period the electromotive force remained constant within ± 3 pet and did not continuously drift in any one direction. After the experiment the alloys were analyzed for chromium in the usual manner. The measured electromotive forces of the cell at 1600°C, (2912°F), are listed in Table I. The activity of chromium, with solid pure chromium as the reference state, (a), was calculated using Eq. [l], , n F E I, n lna RT- U] where E is the measured electromotive force, F is the Faraday constant, and n is equal to 3, the number of equivalents per mole, (nF/RT = 18.59 volts'1 at 1600°C). The resulting activities are listed in Table I. The activity of chromium relative to pure liquid chromium was also calculated. The free energy of fusion of chromium at 1600° C was calculated using

Jan 1, 1969

By J. B. Morrow, D. H. Davis

THERE are two general approaches to the problem of increasing profits from an operation. One is to lower expense; the other is to raise income. Mechanical preparation of coal may be used for either purpose but a prudent consideration of many details must precede any decision lest the results be negative instead of positive. It is quite possible that any net gain will result from a combination of the two. Since mechanically prepared coal invariably is a better product qualitatively than a hand-picked coal from the same mine, it is a reasonable expectation that the customer will be willing to increase the producer's income by paying a higher price. Or there may be the possibility that a combination of mechanical mining plus mechanical cleaning will give a lower over-all production cost for the coal in the railroad car. More likely, there will be found a combination of these two factors. From the customer's point of view, the competitive delivered cost per B.t.u. considered in relation to such incidental factors as dust nuisance, handling properties, ash disposal, and ash fusibility determines what he will pay. In-a bulk tonnage such as coal, freight is a very considerable part of the delivered fuel cost, and obviously freight paid on incombustible ash has no economic attractions. INCENTIVE FOR CLEANING Coal is prepared in four major ways: l (1) by screening or sizing, (2) by mixing or blending, (3) by cleaning, including hand picking and mechanical cleaning, (4) by dustless treatment. By a combination of any or all of these methods, coal can be prepared to standard specifications. It is easily possible to have good cleaning and still get a poor final product because of faulty screening or mixing, while it is possible to produce a very acceptable product from mediocre cleaning if the coal is well screened and mixed.

Jan 1, 1950

By E. J. Ripling, M. W. Toaz

Tensile tests were conducted on pure magnesium and on four commercial alloys over a variety of temperatures and strain rates. The high positive slope of the ductility vs testing temperature curves that is found over a short range of testing temperatures for these materaturerials was shown to result from the fact that the microstructure was not stable at these testing temperatures. Pure magnesium did not display a transition temperature, although its sub-room temperature ductility was low. This poor ductility resulted from a grain boundary weakness. The aluminum-bearing commercial magnesium alloys had a higher ductility than the pure magnesium. ness.Thealuminum-bearingcommercialThese alloys did exhibit a transition temperature and grain boundaries that were stronger than the grain material. Both pure magnesium and the commercial alloys began initiating cracks at strains equal to one half of their fracture strain. MAGNESIUM base alloys' enormous potential as structural materials lies in their high strength to weight ratios. At present, the high strength magnesium base alloys such as AZ-80, which will be discussed later, have about as high a tensile strength to specific gravity ratio as the highest strength wrought aluminum alloy, 75s-T6, and, of course, a much higher strength to weight ratio than structural steel. Further, since the magnesium base alloys develop their high strength to weight ratios with moderate strengths and extremely light weights, the ratio of load carrying capacity to the weight of many structures is relatively higher for the magnesium base alloys than their strength to weight ratios would indicate. This results because judicious increases in section size, such as increasing the depth of bending members or adding reinforcing ribs, can frequently increase the weight of a structure linearly while the strength and stiffness increase as the second or third power of the added weight. Strength and rigidity must be designed into lightweight structures by those techniques which establish multiaxial stress states. Consequently, strong, lightweight structures frequently also possess a greater propensity toward brittle failures. In order to insure against these catastrophic failures, an extra premium must be placed on ductility and toughness in light alloys. Current knowledge of the ductility and toughness behaviors—notched behaviors—of magnesium base alloys is limited.* Most of the magnesium base alloys * The state of present knowledge regarding the effect of testing temperature on mechanical properties has recently been summar-ized by Pritchard.' crystallize in the hexagonal system, so that they are expected to exhibit a tough and ductile to brittle transition temperature. Actually, a transition temperature behavior has been reported for commercially pure magnesium in the literature, but the characteristics of this transition temperatureh uggest that it may not be a transition in the usual meaning, but simply the onset of some thermal softening, a performance much like that which face-centered-cubic lead might exhibit slightly below room temperature. If transition temperatures do exist, such important questions as the manner in which they are affected by internal variables such as chemical composition and grain size, or the effect of external variables such as rate of straining or notch severity have never been investigated. The investigation reported upon herein was undertaken in order to define some of the mechanical behaviors of the magnesium base alloys better, to gain a better understanding of the influence of some of the above listed variables, and particularly to understand their effect on ductility and toughness better. Material and Procedure Material-—Pure magnesium and four commercial alloys were used in this investigation. The alloys were selected so that chemically they made up a series with approximately the same minor alloying

Jan 1, 1957

Question 1—1s Structural Deformation of Some Character Always Necessary for the Migration of Mineralizing Solutions. Especially in Limestone or Other Dense Rocks Discussion by: A. M. Bateman.........120 S. F. Kelly........... 125 C. H. Behre. Jr........118.123 G. B. Langford......... 123 T. M. Broderick.........121 H. E. McKinstry......... 116 R. H. Clarke.......... 123 D. H. McLaughlin........ 118 J. D. Forrester for M. H. Gidel . . 11.4 W. H. Newhouse......... 123 G. M. Fowler......112. 116. 121 R. H. Sales.......... 116 L. C. Graton..........121 Edward Sampson......... 122 R. D. Hoffman.........120 J. 8. Stevenson.......... 117 I. B. Joralemon.........121 L.B.Wright........... 112 Question 2—What Are Some of the Chemical and Physical Characteristics in Certain Beds within a Limestone Formation that Determine Their Favorable or Unfavorable Aspects as Reservoirs for Ore and Other Introduced Minerals? Drscussion by: G. W. Bain....... 127 G. M. Fowler....... 131 C. H. Behre, Jr. ..... 131 L. C. Graton....... 128 J. S. Brown. ...... 126 G.. F. Loughlin...... 128 E. L. Bruce ....... 129 R. H. Sales........ 129 R. H. Clarke...... 130 A. K. Snelgrove....... 130 Question 3—Are There Any Criteria by Which One Can Determine When Mining Operations Have Reached the Roots of an Ore Deposit? Discussion by: J. M. Boutwell...... 139 G. B. Langford..... 139 T. M. Broderick..... 138 . G. F. Loughlin...... 135 E. Y. Dougherty..... 137 R. H. Sales...... . 134 G. M. Fowler....... 132 F. A. Thomson..... 136 I. B. Joralcmon...... 132 Edward Wisser:..... 140 General s. F. Kelly................. . ...........145 References...............................146

Jan 1, 1941