Search Documents

By Donald H. McLauqhlin

ITEM expressed in billions of dollars have become so commonplace these day- that a mere statement of the latest figures for the country s gold reserve scarcely conveys m adequate sense of the immensity of the commitment the nation has made in building up its huge stock, two-thirds of which is now stored at Fort Knox. Kentucky. Only by measuring it against quantities that mean something tangible to a particular group can an adequate comprehension of its magnitude he rained; consequently, to mining engineers, a comparison with the value of output from well-known mining districts might best serve to give some degree of reality to the astronomical figure at which the country gold is now valued.

Jan 1, 1941

By M. E. Nicholson

The solubility of carbon in Ni-Cu alloys was determined at 1000°C. The factors which limit solid solubility are discussed with particular reference to the influence of electronic factors. The results indicate the extent of solid solubility is a function of the density of states at the Fermi surface. THE solid solubility of an interstitial element is primarily limited according to Seybolt and Fullman1 and Speiser and Spretnak2 by (a) the strain energy produced when the solute atom takes its interstitial position, and (b) the partial molal free energies of the solid solution and the coexisting phases. In several binary systems of a transition and a noble metal, where there are no abrupt changes in strain energy or free energies of coexisting phases, the solid solubility of an interstitial third element drops abruptly to a negligible value at a composition corresponding to a complete filling of the "d-band." Such a decrease occurs in the case of hydrogen in the Pd-Ag system at 60 pct Ag.3,4 The solubility of carbon in Ni-Cu alloys seems to vary in a similar manner as indicated by the embrittling effect of carbon on these alloys. These al- loys are embrittled by slow cooling due to the precipitation of graphite. This embrittlement can be removed by heat treatment if the carbon content is less than the solid solubility limit at the heat-treating temperature. If the carbon content of the alloy exceeds the solid solubility at the heat-treating given temperxture, the embrittlement cannot be eliminated by solution heat treatment.' Since pure nickel has a carbon solubility of 0.25 wt pct6 at 1000°C, embrittlement is easily removed from commercial nickel and nickel-rich alloys, which may contain of the order of 0.10 wt pct C. Embrittlement due to carbon cannot be removed from Ni-Cu alloys containing 70 to 80 wt pct Cu by annealing unless: the carbon content is of the order of 0.04 wt pct CL or less."' Thus, it appears that the

Jan 1, 1962

By R. P. Smith

In 1937 the employees of the Hollinger Consolidated Gold Mines Ltd.. at Timmins. Ont., Canada, approached organized medicine for a plan to provide themselves and their families with a complete medical service including hospitalization. This approach was made because of two conditions: (1) the necessity for some organization whereby contributions could be made in instalments to offset the sudden and large expense connected with illness for which the average employee is not prepared, and (2) the need for a more cohesive quality of service to replace a contract practice then in vogue, which did not take care of the employee's family or dependents. In different parts of the United States and Canada similar plans were in force, not only for employed groups but for numbers of people in circumscribed areas. In Europe different countries had adopted various forms of health insurance plans. It then was no surprise that these employees as a group should ask for some similar plan. With the cooperation of the management, a plan was instituted. The plan has one object only—the provision of medical services, including the accessory services such as hospitaliza-tion, X-rays, nursing, and necessary drugs and medicines. It is not concerned with cash benefits, sickness and accident payments, or any form of monetary return as the result of illness, but is simply an organization to provide medical services and pay for them from a central fund. It is a nonprofit organization and the only shareholders are the employees and their families who contribute and who in turn receive services. The Hollinger plan is limited to the employees of the Hollinger mine, who live in Timmins and the immediate vicinity. At first, the membership was voluntary. In the third year, it was made a condition of employment, with the proviso that at the end of any Association financial year an employee may withdraw if he wishes to do so. After withdrawal, he cannot again become a member until the end of the next Association year, and then only by the payment of the back dues. This step was taken to ensure continuity, and to prevent employees from withdrawing when well and reentering when faced with impending illness or operations. The employee himself is subject to medical examination on application for employment, and if accepted is subject to further examination by a specialist in chest diseases under the Workmen's Compensation Board of Ontario. Thus it is possible to exclude those who have heart disease, tuberculosis, or other disabling conditions when first employed. Wives and families of employees are not subject to medical examination but other dependents of an employee—mother, father, or other relative—who are declared by the employee to be wholly dependent upon him must be examined. The employee

Jan 1, 1946

By M. L. Hammond, G. M. Bowers

Silicon dioxide films have been prepared on silicon wafers by the oxidation of SiH, near 400°C. Results previously reported by Goldsmith and Kern7 have been qualitatively corrobovated using a system of different geometry, and significantly greater deposition rates have been achieved. The deposition rate is independent of thickness and nearly independent of the O2/SiH, ratio over a wide range; however, the rate is strongly temperature-dependent. The structure of the deposit depends upon the cleanliness of the substrate, and the electrical field strength of the deposited oxide depends upon the nature of the electrodes. MULTILEVEL interconnects in integrated circuits using aluminum metallization require an insulator that can be deposited at low temperature. Because the A1-Si eutectic is only 577°C, the maximum deposition temperature must be below about 500°C to prevent reaction of the aluminum with the silicon and with other materials in the integrated circuit. Many methods of depositing insulating films of SiO, and other dielectrics have been reported'-6 but the technique described by Goldsmith and Kern7 offers the simplest method of preparing SiO, films. The technique involves the reaction of SiH, and 0, to form SiO, films in the 300" to 500°C temperature range. Previous work using this gas system has been reported8 and the initial development work at Philco Microelectronics was done at the East Coast R&D Laboratories. 9 This paper corroborates some of the results of Goldsmith and Kern,7 shows that much higher deposition rates can be obtained than previously reported, and presents some observations on the structure of deposited SiO, films. EXPERIMENTAL CONDITIONS Fig. 1 is a schematic drawing of the apparatus used in this study. It differs from that of Goldsmith and Kern in that 1) the gases are mixed before they enter the reaction chamber, 2) there is no fritted glass diffuser, and 3) the wafers are stationary during deposition. The control thermocouple was in a well located 0.06-in. from the substrate, and three gas supplies were used: 1 pct SiH4 in N 2, O 2, and N 2. Water vapor must be excluded from the plumbing to prevent the formation of colloidal SiO, and the SiH4 must be diluted with an inert gas because SiH4-0, mixtures are extremely flammable above about 4 pct SiH The wafer temperature was determined by attaching a thermocouple to a test wafer and the temperature was maintained to +5 C. The conditions used in this investigation are listed in Table I. The temperature range was chosen for compatibility with the A1-Si system. The volume ratio of 0, to SiH4 is the actual volume of 0, delivered to that of SiH4, taking into account the initial dilution of the SiH4. This ratio, which was used by Goldsmith and Kern,7 is a useful indicator of the experimental conditions. The active/inactive ratio is the ratio of the volume of active gases, SiH4 and O2, delivered to the volume of dilution gas. The active/inactive ratio is an important parameter to specify for deposition rate determinations since it determines the amounts of reactants that arrive at the sample per unit time. Fairly high dilution ratios were necessary to achieve uniform deposits of SiO,. Most of the process characterizations were performed on the polished (111) face of 3 to 5 ohm-cm, n-type silicon wafers which were 0.009 in. thick; but the data approximately apply to deposition of SiO, on thin films of aluminum. It is difficult to obtain accurate deposition rate data over aluminum films because of coarsening the aluminum surface during exposure to 300" to 400°C. The deposited SiO, film fol-

Jan 1, 1969

Established as a Division December 15, 1948 Clayton G Ball, Chairman Louis C Raymond, Vice-Chairman Sheldon P Wimpfen, Vice-Chairman Henry T Mudd, Vice-Chairman A H Lindley, Jr, Secretary-Treasurer Division of Foreign Activities U S Bureau of Mines Washington, D C

Jan 1, 1956

By F. R. Hutto Jr., F. L. Kady Jr., L. E. Weymouth

The behavior of particulate non-metallic materials in moving contact with smooth surfaces is of interest and concern to manufacturers and users of abrasives, of fillers, and of pigments alike. The theoretical aspects of the subject have been treated to considerable extent in the literature, and correlatic,ns are available that attempt to relate various methods of hardness determination." 2 The particle size and friability are characteristics of the abrasive that are not related to the smooth surface. The hardness, on the other hand, may be visualized as relative to that of the smooth surface. In a study of abrasive action, the role that hardness, per se, plays is a complicated one. For it is necessary to compare the "hardness" of the abrasive, usually a non-metallic, with that of the smooth surface, generally a metal. Hardness of non-metallics is defined as resistance to scratch and is almost universally described with respect to the Mohs scale.3 Minerals have been rated by Mohs numerically from the softest (talc = 1) to the hardest (diamond = 10). By definition, a mineral has a designated hardness when it is scratched by the standard that is numerically just above it on the scale; and conversely, when it scratches the standard that is just below it. Hardness of metals. however.. implies resistance to indentation, a property that has been measured by a number of methods. In fact, the indentation hardnesses of the standard minerals on the hlohs scale have been determined by the Rockwell tester. Reproduced below are two versions of this correlation. 'A conversion chart, prepared by Wilson Mechanical Instruments Division of American Chain and Cable Co., merely gives the conversion from Rockwell to Knoop hardness. The relation between Knoop indentation hardness and Mohs scale has been reported by G. S. Smith — A New Scale of Hardness, The Engineer, Aug. 26. 1949. G. F. Kinney in Engineerin Properties and Aplications of Plastics reports the Rockwell hardness of the minerals directly in the Mohs scale. The question immediately arises as to whether this relation is valid when applied in reverse; namely,

Jan 1, 1961

By H. H. Otto

COMPARED with 1939, the year 1940 has seen no material change in the production of anthracite. Many factors seem to indicate a stabilized anthracite production of approximately 50 million tons per year. The present war has stimulated demand in the Cana¬dian and New England markets, which were formerly furnished with a portion of their needs from Great Britain and other European countries. Neither has there been any material change in the "bootleg coal" situation. This problem is more serious in the Southern anthracite field than in the Hazleton, Wilkes-Barre, and Scranton areas. One reason for this is the nearness of the Southern field to the large anthracite markets in Philadelphia, Washington, Baltimore, and Harrisburg. During the past year no new large

Jan 1, 1941

By Gieskieng, D. H.

Published tables of jaw crusher capacities are compiled for the most part from field performance data, interspersed with interpolations, extrapolations, various safety factors, and other modifications. Such a table attempts to balance and equalize field data from widely different materials, with differences of crushability, efficiency of feeding, sizing of the feed, and so on. The tests described in this paper were undertaken with the objectives of checking previously reported capacities; of studying the effects of various factors upon the capacity, including jaw plate curvature; and, if possible, of deriving a general capacity equation. Such an equation has been derived from the data obtained in these tests. It is given together with factors for its use. While more accuracy than is usually required may be obtained by careful application of the equation, it is of simple form and provides a convenient reference plane upon which the potential capacity of various crushers may be compared, and with which operating adjustments may be made on existing installations. The principal deviation in these tests from the usual approach consists of a laboratory technique which has been developed for the production of selected

Jan 1, 1949

By S. Shapiro, G. Krauss

RECENT investigations1 3 of the products of marten-sitic transformation in Fe-Ni and Fe-Ni-C alloys have made use of light microscopy to describe mar-tensitic fine structure. The application of conventional metallographic techniques to this problem was possible because of the similarity of distributions of parallel striations developed by etching polished surfaces to distributions of transformation twins which are positively identified in thin films by transmission electron microscopy. The surface striations frequently are not well-defined, and could also be due to, for example, rows of etch pits which are not resolved by the light microscope. This note describes the etching effects revealed by examination of surface replicas of mar-tensite in the electron microscope. The application of a replica technique both extends the observations of fine structure made with the light microscope and allows the results of conventional metallography to be used with more confidence. Samples of an Fe-33 wt pct Ni alloy were used for this study because of the detailed knowledge of the fine structure of martensite which has been developed'-4 for alloys of about this composition. Samples transformed to martensite at -120°C, and transformed samples heated to 340°C to effect a small amount of reversal of martensite to austenite, were examined. Surfaces were first prepared for replication by elec-tropolishing in a chromium oxide-acetic acid electrolyte at a current density of 0.1 amp per sq cm and a temperature of 15°C or a perchloric acid-acetic acid electrolyte at a current density of approximately 2 amps per sq cm and a temperature of 15°C. The polished surfaces were then etched for 4 to 7 sec by immersion in a solution of equal parts HC1, HNO,, and H20. Application of the etchant for this period of time produced discrete attack of certain features without loss of resolution due to overlapping of areas most susceptible to etching. The etched surfaces were replicated by 1) preshadowing with Pt-Pd alloy at an angle of 20 to 30 deg, 2) depositing a thin carbon film, and 3) stripping the film and shadowing material by immersion in a 5 pct nital solution. Two types of etching effects were observed by examination of the surface replicas in the electron microscope: l) continuous striations centered at the bottom of long grooves or the tops of pyramidal elevations on the sample surface, and 2) high densities of fine etch pits. Examples of both types of features are shown in Figs. 1 to 4. The striations are in each case continuous and have the same characteristic configurations as do transformation twins in martensite. Fig. 1 shows that the density of grooves decreases toward the edge of a martensite plate and Fig. 2 shows a region where the striations are of varying length. Similar examples of transformation twin arrangements determined by transmission electron microscopy of thinned foils of martensite have been shown in the literature,'~ and, based on these similarities, the striations and their associated grooves or mounds are considered to be evidence for the presence of transformation twins. The transf~rmation twins in martensite are on the order of l00 A thick, much too fine for resolution by the light microscope. It appears that orientation-dependent etching of the matrix martensite about the twins results in grooves or surface elevations which

Jan 1, 1967

[A Aall, Christian H., M49 A Dir, Smelt & Ref, Am. Metal Climax, Inc., 1270 Ave. of the Americas, New York 20, N. Y. Aaroe, S. L., A54 A VP, W. S. Tyler Co. of Canada Ltd., P. O. Box 100, St. Catharines, Ont., Canada Abalos, Teodulo Q., J57 A Prod Frmn, Lepanto Cons. Mining Co., Lepanto, Mt. Province, Philippines Abbitt, James M., A54 770 Sole Blvd., Bartow, Fla. Abdullah, M. Y., J53 Dept. of Mines Res. Div., P. O. Box 1016 Tiger Lane,-Ipoh Peram, Malaya Abel, John F., Jr., J53 F Mine Engr, Thompson Creek Coal & Coke, Carbondale, Colo. Abell, Leo M., M31 B Const Supt, Phelps Dodge Corp., Morenci, Ariz. Abendroth, H. E., A57 Mangore Australia Pty. Ltd., 901 Hay St., Perth, W. Aust.,, Australia Abenius, Hakan V., M52 Falun, Sweden]

Jan 1, 1961

By H. A. Guess

For a number of years I have used for the commercial wet assay of lead generally the ammonium molydate, and occa-sionally the ferrocyanide method. These well-known methods need no detailed description here. In the ore-selling and ore-buying establiahments of the West, 90 per cent. of all wet lead-assays are made by one or the other, and at least nine-tenths of this proportion by the molybdate method. A procedure so well-established must have merit; and, in

Jan 1, 1905

Using 5-p Ni powder and 0.018 ,u A1203, oxide dispersion strengthened nickel alloys were prepared by mechanical mixing of powders, followed by compaction, sintering and extrusion. Processing variables such as cooling of the powder during mixing, electrostatic discharging, mixing time, amount of oxide, and so forth, were studied to determine the effects on room-temperature tensile and high-temperature creep-rupture properties and on the reproducibility of alloys. MECHANICAL mixing of metal and metal oxide powders provides one of the simplest and most inexpensive methods for preparing dispersion strengthened metal-metal oxide alloys;" however, because of large differences in specific gravity, powder particle diameters and other variables, difficulties have been encountered in reproducing alloys and alloy properties. Using 5-p Ni powder and 0.018 p A1203, the following variables were investigated: a) Blending techniques b) Blending time c) Volume fraction of oxide for the selected pow- ders d) Sintering of compacts before extrusion Cooling of Powders During Blending— Cremens and Grant had indicated that dry ball milling of the powder mixture gave superior results over other procedures. When ultra-fine metal and oxide powders became available and comminution was unnecessary or offered little gain, the use of dry mixing in a Waring Blendor gave optimum results.' In the current study, observations of the powder mixtures indicated that considerable heat was generated due to the high speed of the Waring Blendor (15,000 rpm). This heating appeared to produce some degree of clustering and pelletizing. To minimize such agglomeration, a Pyrex cooling coil was installed in the mixing vessel. A double coil, water cooled, proved to be quite satisfactory, providing a fair degree of cooling along with good erosion resistance. Discharge of Electrostatic Charge—Electron-microscopy showed that agglomeration was minimized by the cooling procedure but was not entirely eliminated. It appeared that some of the ag- glomeration had to be explained on the basis of an electrostatic attraction due to the high-speed blending operation. These charges had the effect of promoting the growth of alumina clusters. At the end of the blending procedure such clusters had an effective size which was as much as 50 times that of the individual powder particles and were very tightly bunched. Several methods were utilized to try to discharge the electrostatic forces to minimize the clustering. One successful method, utilized in alloy 17, involved continuous exposure during blending to a radium source of 50 millicuries at a distance of 1.5 ft from the container. A number of other methods were noted to work equally well. Fig. 1 shows the more open oxide structure which results from such a treatment, permitting the matrix metal to penetrate into the cluster more effectively. The combination of powder cooling and discharging led to noticeably improved structures. Fig. 2 shows a cross and a longitudinal section in alloy M-17, one of the best alloys, illustrating the marked decrease

Jan 1, 1961

By J. N. Ong

The oxidation of tantalum is assumed to occur by four simultaneous first-order chain reactions; solution of oxygen in the metal, nucleation and growth of a suboxide phase at the metal surface and two phase boundary processes which give rise to two different modifications of Ta2O5. A rate equation is then formulated which accounts for all principal details of oxidation behavior, unifies and correlatss the results of the principal investigations, and expresses the rate as a function of pressure, temperature, and time. For purposes of practical application, the expressions: may be used below and above 700T respectively to determine the regression rate of tantalum in cm per hr, where T is to be expressed in "K and P in atmospheres pressure of oxygm. The equations will reproduce within a factor of two all reported experimental rates in the temperature range 475" to 1400°C and pressure range 0.000026 to 40.8 atm 0. 1 HE oxidation kinetics of tantalum have been investigated thoroughly in the temperature range 50" to 1400 and pressure range 1.32 x l0-' to 40.8 atm pressure of 0,and as a result, the principal features of the oxidation of tantalum are known and have been described in considerable detail. The exposition of the characteristics of the behavior of tantalum in oxygen has been largely descriptive, with considerable attention being devoted to elucidating the structure, composition, and morphology of the resulting oxide products. The weight change vs time results have usually been reported graphically. With the exception of the linear rate below 700 C and the process of diffusion of interstitial oxygen into the metal,6'9 no effort has been made to characterize the reaction rates in functional form. It is the purpose of this paper to demonstrate that when the fundamental principles of chemical kinetics are rigorously followed, the results of the principal investigations will be correlated and unified and the oxidation rale may be expressed as an analytic function of pressure, temperature, and time. In addition to accounting for the temperature and pressure dependency of the oxidation rate, the following minor features will be accounted for as a result of the basic analysis: the initial period of nonline-arity in rate at low temperatures, which decreases with increasing temperature;3'5'7 the rate vs temperature cusps obtained at constant pressure"5 the concentration gradient of oxygen interstitially dissolved in the metal.5'7 The analysis will also be consistent with the overall chemistry of reaction and with all visual, microscopic, and X-ray observations. DEVELOPMENT OF RATE EQUATION As a fundamental basis for the treatment of metal-oxygen reaction kinetics, it will be regarded that the rate of reaction is determined by the concentration and not the activity or chemical potential. It is further assumed that all metal-oxygen reactions are first order complex chain reactions" whose rate is dependent on the concentration of an intermediate species which is a complex function of the oxygen concentration, or oxygen pressure, only. The basic rate equation is therefore: is the weight of oxygen consumed by the reaction, A is that portion of the area of the metal over which the reaction is occurring (cm2), t the time (sec), kf the rate constant for forward reaction, C the intermediate species concentration and f '([Oz]) and f (Po,) are complex functions of oxygen concentration and Oxygen pressure respectively. Reverse reactions may usually be neglected in metal-oxygen systems since a large negative free energy generally accompanies these reactions. Eq. [I] takes different forms when the rate of reaction is controlled by diffusion into or through a phase or at a phase boundary. For diffusion into the metal phase, the rate is given by1' Di is the diffusion coefficient of species diffusing into the metal phase (cm2/sec), and Q is the corre-

Jan 1, 1962

By HAROLD VINTON COES

THE motive for merging or consolidation today is conspicuously different from that actuating business men in the late eighties and early nine- ties. Then they combined to secure added productive capacity and to monopolize their respective industries with a view to exploiting the consumer. So flagrant were some of these cases that they brought about their own correctives via retaliation on the part of the public and the subsequent restrictive legislation and legal curbs. The objective of the present-day merger, writes W. R. Hill in Printers' Ink, December, 1927, is summarized as follows : "In the golden days when an industry was being cut to pieces, the prevailing cure was to combine. The reason for such trusts was to strangle competition and by creating a monopoly, dominate the market, raise prices, regardless of economic business methods, and simply force larger profits.

Jan 1, 1930

By Wayne L. Worrell

Thermodynamic data for the stable carbides and oxides of chromium, molybdenum, and tungsten have been critically eualuuted and are used to determine the stable condensed phases at 1 atm total pressure in each metal-carbon-oxygen system. Pourbaix-Ellingham diagrams have been constructed and are used to estimate the minimum temperatures neces.see)*y to oblain these metals by corbolhermic redlrction under reduced pressures. USING recently reported data for the carbides and oxides of chromium, molybdenum, and tungsten, the stable phases in the Group VI metal-carbon-oxygen systems at specific temperatures and pressures can be determined. The thermodynamically stable regions in each metal-carbon-oxygen system can be completely pictured using a Pourbaix-Ellingham diagram in which the two coordinates are oxygen potential (-RT In Po2) and temperature. Worrell and chipman' have described and constructed such diagrams for the metal-carbon-oxygen systems of vanadium, columbium, and tantalum. Downing2 has used similar diagrams to provide a description of the reactions in submerged arc furnaces. One of the examples which he cited was the Cr-C-O system; however, an improved diagram is presented in this paper using recently obtained data for the carbides of chromium. Although some of the oxides and carbides of the Group VI metals exist over slight ranges of composition,3 all solid phases are represented as stoi-chiometric compounds in the subsequent diagrams. Any error introduced into the calculated equilibria by neglecting the compositional variation of these phases is less than the uncertainty in the thermodynamic data. In a Pourbaix-Ellingham diagram for a three-component system, the phase rule requires that at equilibrium four condensed phases specify a point, three condensed phases determine a line, and two condensed phases define an area. To obtain a well-defined area at high oxygen potentials and teniperatures, the initial carbon to oxygen mole ratio is specified to be more than sufficient to reduce the oxide but not enough to convert all the metal to carbide. Thus, the lowest regions in the subse- quent Pourbaix-Ellingham diagrams represent areas in which the metal and its carbide are the stable condensed phases. Cr-C-O SYSTEM A) Thermodynamic Data. To simplify the subsequent calculations, all thermodynamic data are presented in the form of linear Gibbs-energy-of-formation* equations which were derived for the temperature range 505° to 2000°K and are reasonably accurate over the entire temperature ranges of the diagrams. The thermodynamic data for the compounds occurring in the Cr-C-O system are summarized in Table I. Several volatile chromium oxides have been reported,4 but their influence is negligible in the Cr-C-O system. Thermodynamic data for CO and CO2 were taken from the compilation of Coughlin.5 The only solid chromium oxide sufficiently stable to exist below 1800°K in the Cr-C-O system is Cr2Os.11 The Gibbs-energy-of-formation equation for Cr2O3 was obtained by revising the data tabulated in Coughlin,5 using the heat of formation of ah' and the high-temperature thermal data for chromium.7 In 1953 Richardson8 re-evaluated the original work of Kelley and coworkers,9 who measured the thermodynamic properties of the chromium carbides. However, the high-temperature equilibrium results of Boericke9 yield values for ?G°f of Cr2O3 which are 2 kcal more positive than the accepted data. His results for the chromium carbides are based on the same questionable equilibria. Gleiser10 recently determined the Gibbs energy of formation of Cr3C2 and the equation in Table I was calculated from her data and the thermal data of Kelley and coworkers.9 Thermodynamic data for the Cr7C3 and Cr23C6 carbides were obtained by combining the Cr3C2 data

Jan 1, 1965

Boiler-Room Economy "Establishing and Maintaining Boiler-room Economy" is the title of a paper presented before the Ohio Society of Mechanical Electrical and Steam Engineers by Geo. H. Gibson, of which the following is an excerpt: Boiler-room economy depends less upon equipment than upon operation, i.e., it depends largely upon the condition in which the apparatus is maintained and how it is used. A given boiler may operate this week with an efficiency of 78 per cent., and next week with an efficiency of 65 per cent., while using the same fuel and developing the same rating. If there are variations ii; character of fuel and in load and other factors, the falling-off may be even greater, possibly to less than 60 per cent. The steam produced may cost twice as much per 1,000 lb. at one time as at another. Most steam plant managers know from their own experience that these statements are not exaggerated. It does not take much of a plant to run up a coal bill of $5,000 per year, many "spend $10,000 for coal, and fuel bills of $50,000, $100,000, or $200,000 per annum are not uncommon. As it call be shown in the majority of these plants that 10 per cent. of this amount may be saved, and in large numbers of them 25 per cent., while in some the expenditure can be cut in half, there is no disputing that we have here a subject worthy of attention. In the production of steam the greatest variable is the human factor. Before we can pass judgment, however, we must first have standards. This implies accurate quantitative knowledge of fuel consumption and steam production. We must measure the output and know how much the steam costs per thousand pounds, and how many pounds of steam are obtained from a pound of coal. We can then begin to analyze the problem, and find where and how methods and conditions can be improved, and how much. Many favor buying coal on a B. t. u. basis. This is advisable where the amount purchased warrants the considerable expense involved in systematically gathering samples that: are. truly representative and in having analyses made, of every carload. Coal analyses, combined with. an honest endeavor on the part of the miner to ship good coal, should insure the receipt of the heat units paid for. , It often happens, however, that the coal which is cheapest on a B.t.u. basis is not the cheapest or most suitable for producing steam, because of peculiarities of the plant in which it is to be burned, or conversely, the fuel which furnishes cheap B.t.u. may require special methods or equipment for its economic utilization.

Jan 2, 1916

By H. Rush Spedden, A. M. Gaudin

IN the belief that a critical study of its operating problems might be a sound investment, the Cuban American Manganese Corporation initiated an ore-treatment research in cooperation with the Massachusetts Institute of Technology. One of the early objectives of this research naturally became the relationship of the microscopy of the Cuban ores of the Corporation to their flotation treatment. The operations in Cuba have already been described by F. S. Norcross, Jr.7 and the laboratory study of manganese oxide flotation goes back a number of years .4 Broadly speaking, the difficulties encountered in the flotation of manganese ores are that the consumption of reagents is extremely high, the concentrate contains more silica than is desirable and the tailing losses are relatively high. An appreciable betterment on any of these scores would achieve a definite betterment in costs, quantity of minable ores, and quality of product. The microscope study discussed in this paper was made on samples from the Quinto mine, from the Ponupo mine, and from mill products at various stages of passage of the ore through the mill. The writers have had access to Company records and in particular to the petro¬graphic studies made on thin sections of ore by the late Professors R. J. Colony and Philip Krieger, of Columbia University. They acknowledge their debt to both of these men for the help derived from the reports. Manganese oxides are black, friable, smudging. It is, therefore, very difficult to judge operations by inspection. The mineralogy of manganese compounds seems to be confused, and the authors believe that many more minerals have been described than actually exist. Much of this difficulty is due to the prevalence of the structural conditions that will be discussed further in this paper; namely, the porosity and the friability of the ores, and the extremely intimate association of minute manganiferous mineral crystals with impurities of various sorts. By all odds the most important manganese mineral in Cuba is the one that in this paper is called "psilomelane." The name "psilomelane" has been used in so many different ways that the choice of it for this ore may not be approved by all. However, it seems to be the best under the circumstances. This mineral accounts for about 97 per cent of the manganese in the ores of the Quinto and Ponupo mines and in the mill feed. The remaining odd 3 per cent consists mostly of pyrolusite together with minor amounts of other manganese oxide minerals. DESCRIPTION OF PSILOMELANE Aggregate Structure In grains or lumps, psilomelane has a characteristic fibrous appearance and seems

Jan 1, 1942

[Aamot, Clav Crone, (Member '29) Met., Det Norske Aktieselskab for Elektrokemisk, Industri, Inc., Oslo, Norway. Aamot, 0, Crone, (Member '29) c/o Elektrokemisk, Radhusgaten 23, Oslo, Norway. Aase, Glenn D., (Junior Member '40) Jr. Met., American Smelt. & Refin. Co., Selby, Calif. Abadie, Henry G., (Junior Member '43) Div. Petr. Engr., Union Pacific R.R. Co., 422 W. 6th St., Los Angeles 14, Calif. Abbott, Clarence E., (Member '04) Civil Engr., V.P., Tennessee Coal, Iron & R.R. Co., 1542 Brown Marx Bldg., Birmingham, Ala. Abbott, Fred E., Jr., (Member '44) Petr. Engr., c/o Arabian American Oil Co., A.P.O. 816, c/o Postmaster, New York, N. Y. Abel, Raymond L., (Member '28) Chem. Engr., 0. 0., Pittsburgh Chem. Warfare Procurement Dist., American Bank Bldg., Pittsburgh, Pa.]

Jan 1, 1946

By A. J. Williams

THE province of Saskatchewan, situated in the center of the Great Plains region of Canada, has, like most prairie areas, an essentially agricultural economy. Most of its population of about 860,000 is located in the southern half of the province in the farming and ranching areas. To the north of the prairie is a broad forested belt supporting a considerable timbering industry, and the northern one third of the province is glaciated pre-Cambrian rock formation. This latter area is relatively barren of vegetation, but the presence within it of a considerable variety of radioactive, noble and base metals, and industrial minerals has been shown by prospecting in recent years.' Glacial Geology The Keewatin ice sheet, considered to have accumulated in the country to the west of Hudson Bay in Pleistocene time, covered at its maximum advancement almost all of Saskatchewan and extended south of the international boundary. Only in the Cypress Hills in the southwest and around Wood Mountain in the south central portion of the province did the preglacial formations escape the action for this glacial period. The bedrock of the plains and forest areas therefore is overlain by moraines and modified glacial drift, which vary in thickness from a few feet to 400 or 500 ft.' Glacial action in the pre-Cambrian area of the province was largely erosional, most of the more recent formations and some of the pre-Cambrian rock being transported out of the area to the south and west. It has been estimated that about 13 pct of this area is composed of lakes and rivers not too adaptable to rail or water transportation, so that until the use of aviation for exploration purposes became general, development of the area was slow. To the south, the heavy mantle of glacial drift has to some extent deterred the discovery of industrial minerals in the bedrock underlying the forest and prairie regions3 At the same time, this drift contains numerous deposits of those most elementary and necessary industrial minerals, sand and gravel. Sedimentary Basin The major feature of the sedimentary deposits underlying the plains regions is the basinal structure known as the Moose Jaw syncline, which runs from the southeast corner of the province in a northwesterly direction. To the west of this syncline the formations curve upward, then have been faulted and further upthrust to appear at the surface in the foothills of the Rockies in Alberta; to the east and north they curve upward into Manitoba and northern Saskatchewan, but the surface contacts are covered mostly with glacial drift.238 The axis of the syncline dips to the southeast, so that there is also an upward trend of the formations along the axis to the northwest. In illustration of the regional structure underlying the province, the pre-Cambrian basement has been logged in drillholes at the following depths in several locations: Ogema (south central), 9390 ft; Gronlid (northeast), 2599 ft; Vera (northwest), 4422 ft; Big River (north northwest), 2348 ft. Fig. 1 indicates the general surface geology of the province, ignoring such glacial overburden as may overlie many of the bedrock formations. Also indicated is the approximate location of the axis of the Moose Jaw syncline.' Industrial Minerals Clays: The province is fortunate in possessing a widespread distribution of clays of ceramic value, ranging from those used for heavy structural products to the high grade pottery and china clays. Shales suitable for brick and tile production are found in the Upper Cretaceous and Tertiary formations across the south of the province where the glacial drift is thin or nonexistent. Many deposits of glacial lake clays suitable for such wares are found scattered over the rest of the province south of the pre-Cambrian area. The Whitemud formation of the Upper Cretaceous is a narrow sedimentary band of secondary clays found intermittently at points across the south of the province where glacial action did not disturb or remove them.' In the southwest corner of the province, around Eastend in the Frenchman River valley, the refractory clays of this formation are contaminated somewhat with iron compounds or other alteration products of basaltic rocks. This eliminates the use of those clays in true whitewares, as they fire to creamy buff shades at the lower temperatures and to a blue-specked grey at cone 8 to 12, (2280°F to 2390°F), the range commonly used in firing whiteware. However, for use in the production of colored artware, caneware, stoneware or crockery, and sewerpipe, this type of clay makes an excellent body that requires little or no addition of flint, feldspar, or other fluxing materials such as are required in the higher class of ware.' It is not a grade of clay that can be shipped great distances to the manufacturing centers, but a market for considerable tonnages has developed at nearby Medicine Hat, where cheap natural gas is available for the firing of the ware. Farther east in the south central portion of the province, the clays of the Whitemud formation are generally more refractory and white burning. The formation is divided into three zones, consisting of white clays, brown shale, and white sandy clays.

Jan 1, 1953

By Lyman H. Hart

Some of the significant facts that will affect the supply and demand for metals during the next few decades are given in this presentation. This is important because the only hope for intelligent guidance of the national destiny depends upon presenting a consistent and accurate picture of basic problems. The metals problems now fomenting are only slightly less important than those precipitating the energy crisis. Admittedly, it is difficult to generate serious thinking on this subject when the world is enjoying easy access to all metals at modest prices. This is possible because of the current world capacity to over-produce, and United States credit standing, at least up to now, has permitted buying freely on world markets. Although both these vital conditions are subject to change, there is little doubt that if the U.S. financial house is kept in order, we can muddle along for a while on a generally expanding, metal-based economy. But should our credit standing be permitted to collapse, or should there be a tightening of world supplies of metals, the nation would immediately find itself in trouble. Unfortunately, clear signals indicate that both of these conditions are threatening. The metal age started many centuries ago, and with the exception of the noble metals, barely a dent was made in world reserves until the present century. Then, as a result of the pioneering ideas of D. C. Jackling and Paul Gemmel, and the willingness of the McNeals, Penroses and Guggenheims to back ideas with money, a virtual explosion of metal production was propagated throughout the world. It is important to examine the causes of this expansion to determine whether it is a trend that may be sustained or whether it is anomalous and therefore attributable to circumstances not likely to be repeated or continued. This period of plenty is a once only phenomenon. Vast metal resources have been sitting around here for eons, while the world was unaware of or unconcerned with their existence. But when population began to grow exponentially, and ways were discovered to use metals to develop machines to do the work of men and animals, the exploitation of raw materials increased at a staggering rate. And now the realization is dawning that minerals are a wasting asset and are beginning to present supply problems that should begin to be of concern. Two main factors have caused this condition; One is the population growth, and the other is the expanding demand for irreplaceable raw materials as nations become more developed. A group of systems analysts, at Massachusetts Institute of Technology in a book Limits of Growth, has warned that at present rates of population growth and resource consumption together with environmental constraints, a point will be reached within 100 years when the world population will become totally incapable of supporting itself. The authors conclude that this end result could be avoided if a planned equilibrium could be established at a lower rate of population growth and resource consumption. Fortunately, there is evidence that the population problem is moderating. The growth rate in the U.S. has decreased from 2.3% per year in 1900 to 1.1% in 1970. But, even at the lower rate, population will double in 70 years. The world rate is greater, and if it continues, world population will rise from 3.5 billion to nearly 10 billion in 50 years. All of these projections are questionable because the dangers of growing population are now being recognized. A marked decrease in growth rate has been noted in the more developed countries-in fact, it was zero in the U.S. in 1972. The other factor affecting consumption of raw materials is the increase in per capita use of most items as individuals become more affluent. Many economists believe that developing countries such as China and India represent a vast future potential market; but there are others, with whom the author agrees, who believe over-population tends to stagnate development. Nevertheless, it is a fact that vigorously developing societies increase consumption at a rate far above their population growth rate.

Jan 1, 1974