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By Thomas P. Bispham

INTRODUCTION From the lender's point of view, the greatest period of risk in a project financing occurs during the construction phase. Therefore, most projects are supported during this phase by completion guarantees supplied by some credit-worthy entity; for example, the project sponsors in the case of a joint venture, such as that of W.R. Grace, Hanna Mining, and Liberty Capital; or by a strong contract with a utility or foreign importer/investor, such as the way North American Coal Corporation has structured many of its transactions. THE PROJECT LOAN REQUEST A project financing is a more complex form of term loan than one using an ongoing corporation's balance sheet as a credit base and, therefore, a potential lender will subject the loan request to a more rigorous analysis. To support this effort, the financial institution will require a more detailed information memorandum to evaluate the credit and technical risks of a project - especially since much of the necessary information is not otherwise available. (See also Gibbs and Sroka paper above in this Chapter) A well-prepared information memorandum will impress prospective lenders with the planning ability and general competence of management. Also, the process of preparing the memorandum will help management understand the true extent of the opportunities and limitations of its venture. Appendix A outlines the topics which comprise a complete information memorandum for a loan request. Of some interest to those seeking to sell a currently-operating mining venture, a similar information memorandum should be prepared i.e., covering the same topics discussed here, for the investment banker to use with potential purchasers. For that purpose, though, one might not want to prepare quite as much detail as for a lender. Appendix B outlines the elements of a reserve evaluation and feasibility study, often called the "Bankable Document." Usually, these studies are prepared by independent engineering consultants for use by potential borrowers and sellers. (Potential purchasers will often contract for a similar study for their use in evaluating an acquisition.) ELEMENTS OF A LOAN INFORMATION MEMORANDUM 1. Outline: The information memorandum should begin with a one-page outline covering such topics as: a. The borrower's name, address, and phone number. b. Principal contact at the borrower. c. Amount of the proposed financing. d. Desired pricing and structure of the proposed financing. This should include a description of the amount and source of equity in the proposed financing. e. Use of the proceeds and timing. 2. Summary: The most important information contained in the memorandum should be summarized in two pages. Note - If the borrower is a recently-formed single-purpose company, then elements 3, 4, and 5 will apply to the guarantors of completion and to the project sponsors. 3. The Borrower: This section is a brief biography of the borrower including such topics as date and state of incorporation, founder(s), lines of business, etc. 4. Capitalization: The borrower's current debt and equity position, including leases and trade debt, with amounts, terms, names, and addresses enumerated. Equity owners, and percentage ownership, should be identified. 5. Historical Financial Statements: If available, a minimum of five year's worth of complete historical financial statements

Jan 1, 1985

By John Tyssowski

In 1925, Harry Howard Stout, then metallurgist for Phelps Dodge Corporation, while investigating the cleaning of cathode copper by various gases at elevated temperatures below the melting point of the metal, observed in the laboratory that particles of pure copper heated in a closed tube filled with hydrogen seemingly "stuck together." By further investigation he found that there was actual crystal growth across the boundaries of the particles of pure metal; in other words, there was a complete new crystal realignment and growth throughout the newly formed copper mass. It was coalescence, not adhesion; the several particles had become one unit. From this discovery has been developed the coalescence process, whereby copper of cathode purity is squirted out in semifabricated form from an extrusion press, by the application of about 3000 tons pressure on a 10-in. piston. Stout decided that cathode copper produced by electrolytic deposition was the logical source of the pure copper required for the coalescence process, but as there was no way of reducing the ordinary tough commercial cathodes to the small particles required he was confronted by a serious problem at the outset. Under his direction, this problem was solved by William H. Osborn and Harry Howard Stout, Jr. They developed the process and technique for producing cathode copper in brittle, friable form, and to them must be given the greater part of the credit for this phase of the development program as well as for that relating to the gas cleaning of the cathode particles. Concurrently, the three metallurgists worked on the problem of effecting a complete union of the cathode particles. Adequate washing was all that was needed to free the particles from electrolyte solution and slimes. A press was designed to produce briquettes of the proper porosity and density, and a method was devised of removing surface oxidation from the particles of cathode, by treatment in an atmosphere of deoxidizing gas at an elevated temperature. The temperature was determined at which the surface cleansing and preheating could be done in one operation, and for this a charging and preheating furnace in which there is maintained a positive pressure of deoxidizing gas atmosphere was designed. And finally, a method of feeding the heated briquettes of deoxidized cathode copper into an extrusion press without contamination from the air was evolved. For the final stage, a press was required because not only heat but pressure was required to obtain complete growth of the new crystals between the cathode particles as well as the elimination of all voids or non-coalesced areas. All essential stages of the process are protected by patents or patent applications in the United States and principal foreign countries, and the copper is produced on a commercial scale.

Jan 1, 1941

By Wilford S. Wright

FOR the past four years the management of the Black Hawk Consolidated Mines plant at Mogollon has conscientiously kept accurate records pertaining to cost of operation and the performance of certain equipment. These records have been valuable in coordinating the work in the mine, mill and power plant. Also, as to quantity and kind of equipment and supplies most suitable from the standpoint of economy and dependable operation, they have served as a guide. Through comparison with records at other mines, where the same things are being done in a different way, they have pointed out mistakes to be avoided. No outstanding accomplishments, either in costs or performances, are revealed; in fact, some of the results are perhaps quite inferior to those obtained at similar plants, but it is with the thought that more records should be published for the benefit of the mining profession that the author presents these data. To other operators and to mining engineers who are called upon to make estimates for prospective operations, the information herein should be helpful. GENERAL CONDITIONS Mogollon is in the southern part of Catron County, southwestern New Mexico. It lies near the western border of the Mogollon Range, 14 miles east of the Arizona line. Silver City, 80 miles to the southeast, is the nearest railroad point. The connecting road, over which supplies are hauled into camp by trucks, is an improved highway for about 50 miles; the remainder consists of graveled roads and unimproved steep mountain grades. One general supply truck and one tank truck make daily round trips. Hauling of supplies to the mine has cost at the rate of $0.08 per ton-mile; or, on the basis of ore production, $0.30 per ton mined. Lumber, hauled in from local mills, has cost an average of $30.00 per 1000 board feet, $8.50 of which has been for hauling. The annual consumption averages 108,000 board feet. Lime, hauled from a plant in Arizona, is about the only other item not brought out from Silver City. Fuel oil for the generation of power is the item of greatest hauling expense, the f.o.b. Mogollon cost of approximately $0.06 per gal. being nearly twice the f.o.b. refinery price. Water for power plant, mill and camp use flows to camp storage tanks through a 4-in. pipe line from a spring and intake 3 miles up Silver Creek Canyon. A few times, particularly in the month of June, mill operations have been suspended for two or three days because of water shortage. MINING CONDITIONS During the years 1938, 1939, 1940 and 1941, the mine produced 230,059 dry tons

Jan 1, 1943

By John L. Boardman, C. W. Goodale

The motives behind the organization of the Bureau of Safety were twofold. First, there was the policy of the company toward its employees, which was one of fairness and consideration for their welfare and which entails the prevention of injuries; second, in order to prevent injuries, a study of their causes was essential, and this study could be made only by a thorough systematic classification of accidents, which required a special department to form and carry out the plans. The Bureau of Safety was organized to begin operation Jan. 1, 1914, hut practically all of the first year was spent in collecting data, making plans, etc. This department is semi-independent of others and reports directly to the president and general manager. It consists of the president of the company and the managers of the following departments: Mines, Washoe Reduction Works, Great Falls Reduction Works, Coal department, lumber department, B. A. & P. railway; and the chairman of the Bureau of Safety. Working under this group is the General Safety Committee consisting of the manager of mines, as chairman, the general superintendent, two assistant general superintendents, and the heads of the following departments: mechanical, geological, purchasing, sampling works, and framing plant; and also the safety engineer. Operating under the General Safety Committee are the group safety committees, consisting of the Anaconda group of mines, Boston & Montana group of mines, zinc group of mines, Washoe reduction works at Anaconda, B. & M. reduction works at Great Falls, coal department, lumber department and the R. A. & P. railway. Each of these group safety committces was in charge of the superintendent or manager of the group represented and the committee consisted of the foremen of the mine's or works that the committee served, as well as the safety engineer. These foremen and superintendents had met regularly for the purpose

Jan 1, 1923

By Blake M. Caldwell, Thomas C. Poulter

A new approach to an old problem has made it possible to do in a a tively short period what has not been accomplished in the past three quarters of a century using strictly experimental methods. A theoretical study was made of the underlying principles whereby a jet is formed by a shaped charge and of the mechanism of the penetration of the target by that jet. It was found that there are more than 10, and perhaps as many as 15 variables affectin!? the performance of the shaped charge. Only a few calculations are necessary to show that it is physically impossible to investigate all of these variables experimentally. The shaped charge theory has been extended to include a previously little-understood mechanism in high explosive phenomena; namely, low order detonation. By superimposing a high order detonation on a zone already undergoing low order detonation, all appreciable improvement in performance is accomplished. The development of a design wherehy these phenomena are coordinated in such a way as to develop a jet which is tailored to meet the specific target requirement will be described in detail. The shortcomings or even impossibility of strictly experimental techniques will be illustrated by a discussion of the development of a special-purpose explosive charge. INTRODUCTION In an article appearing in the May, 1888 issue of Scribner's Magazine, Charles E. Monroe described his early experiments with gun cotton (Fig. 1) which led to his name being most fre-quently connected with our present-day shaped charge. Although the sunken letters or "cavities" in Mon- roe's gun cotton were not lined, they produced some penetration of an iron plate. The credit for the lined shaped charge, however, should rightfully go to Dr. R. W. Wood of the Physics Dept. of Johns Hopkins University, who was responsible for first discovering the fact that a metal liner in a cavity of explosive gave high velocity fragments and/or jets of metal. This discovery was made by Dr. Wood inadvertently while investigating an accidental death resulting from an electric blasting cap. He discovered that a jet of high velocity copper particles was ejected from the dimple

Jan 1, 1958

By R. R. Brandenthaler

CONTROLLING -the pressure under which a well produces crude oil has advantages that are ap¬parently not entirely realized by many operators in the Mid-Continent district. The possibilities of utilizing well pressures are indicated by a series of ex-periments recently completed by the Bureau of Mines in which pressure control was successfully applied to 20 wells in, the Davenport field. The flowing period of all of .the wells was lengthened in some instances it was. more than doubled. The daily oil production from approximately one-half of the tested wells was in-creased. The amount of gas produced per barrel of oil was decreased, and this, in addition to a slower rate of decline in production, indicated that the ultimate re-covery had been increased. The successful application of pressure control to flow-ing oil wells must take into consideration the relation-ships existing between pressures in the different parts of the system which, though not equal, are nevertheless more or less interrelated. These relationships, which have such an important bearing on the results obtained by applying pressure control, are as follows: A change in rock pressure will affect the tubing pressure, casing pressure, and differential pressure, but it will not affect the trap pressure. A change in tubing pressure will affect the differential pressure and casing pressure; also, a change in casing pressure will affect the tubing pressure and differential pressure. Trap pressures are not affected by rock pressure, casing pressure, tubing pressure, or differential pressure, unless the traps are required to handle gas and oil beyond their capacity. Trap pressures will affect the differential pressure, tubing pressure, and casing pressure and any changes at the well-head, whether differential pressure, tubing pres-sure or casing pressure, will affect the pressures in the well. Any change in rock pressure results in a change in the tubing pressure, casing pressure, and differential pressure. When any sudden or unusual change in well-head pres-sures occurs (for example, an erratic tubing pressure), and when a sudden decrease in oil or gas takes place, it is al-ways advisable to note whether the trap pressure has changed. If the trap pressure has not changed, note whether the oil line from the trap to the flow-tank has become clogged, as would be evidenced by a rise in the oil level in, the trap. If the oil line is functioning properly, and if the trap pressure has not changed, the flow-line from the well to the trap should be inspected. If it is free from obstructions, then changes in the differential pressure, tubing pressure, and casing pressure must be due to changed well conditions.

Jan 4, 1927

By Waldemar Dyrssen

I CANNOT agree with the results obtained by the committee. The gas obtained per pound of coal is too high in calorific value and the amount of gas is too large. It should require about 190 cu. ft. of oxygen per 1000 cu. ft. of gas and not 75.14 cu. ft. as is given on page 35 of the report, or about 2.5 as much. Calculating the calorific value per pound of coal from the coal analysis given on page 34, according to Dulong's formula, the gross and net calorific heat are about 12,890 and 12,430 B.t.u., respectively, which is about 18,600 and 17,900 B.t.u., respectively, per pound of carbon in the coal. This is an unusually high figure, as ordinary bituminous coal has less than 18,000 gross B.t.u. per pound of carbon. Assuming, however, that the calorific values calculated are correct, the following results are obtained. On page 35, the net calorific heat in the gas per pound of coal is given as 12,856 B.t.u. and calculation for the gross value shows it to be about 13,950; in other words, the gas contains (13,950 - 12,890) ÷ 12,890 = 8.2 per cent. more heat than the coal on a gross basis and (12,856 - 12,430) ÷ 12,430 = 3.4 per cent. more on a net basis. The calculated amount of carbon in this gas per pound of coal gasified is about 0.688 lb., or nearly the same as in the coal (0.6972) and the gross and net calorific heat per pound of carbon in the gas are 20,300 and 18,710 B.t.u. which are 9.1 and 4.5 per cent. more than for the carbon in the coal. These calculations show that the results given in the report cannot be correct. There must always be some heat losses in the gasification of coal, in radiation from the producer, and in sensible heat in the gas; there must be some loss of carbon in ashes and in soot, and there are always tarry vapors in the gases that are condensed and do not appear in the fixed gases. From the excessive heat in gas per pound of carbon contained therein, it can also be concluded that the percentage of hydrogen in the gas is too high, from which it follows that the moisture decomposed is too high and that more free oxygen must be used.

Jan 11, 1924

By H. R. Stahl

THE disseminated lead district of Southeast Missouri lies 70 miles south of St. Louis. The only metal of economic importance in the ore is lead, but minor amounts occur of iron, zinc, copper, cobalt, nickel, silver and cadmium. These minor metals, as might be expected, tend to concentrate in both the flotation and table middlings. In the past, some zinc has been recovered by differential flotation. The silver and cadmium tend to associate with the zinc, and some recovery is made of these two metals at the smelter. The lead occurs as galena, or lead sulphide. The minor metals are also present as sulphides. The presence of oxidized lead is suspected, but has not been definitely proved. The gangue is chiefly dolomitic limestone, with small amounts of sandstone and shaly glauconitic and chloritic minerals. The ore contains about 3.25 per cent lead, occurring as galena disseminated through the gangue. Some of the galena is very finely disseminated, and the mineral in the gravity tailings, or chat, is seldom or never in the free state. The method of treatment of the ore has been evolved over a period of 75 years; hence probably is not far from correct. The milling processes have tended toward simplification during the past 15 years, but recoveries have never been sacrificed for the sake of simplicity. In many cases, simplification of flowsheets has led to better recoveries and operating economies. A simplified flowsheet is shown in Fig. I. The St. Joseph Lead Co. operates four mills in the Flat River district, with a normal total capacity of about 21,000 tons per day, divided as follows: Federal mill, 11,000 tons; Leadwood mill, 4500 tons; Desloge mill, 3400 tons and Bonne Terre mill 2400 tons. The methods of concentration used at these plants are similar in principle; they differ mainly in details and in the type and size of the equipment used. The process of concentration may be divided into five main steps; i.e., dry crushing, wet grinding, classification with its attendant desliming, tabling and flotation. A brief description of these processes will be given, noting important differences in the various plants, and also noting the more important changes or developments of the past few years. DRY CRUSHING The run-of-mine ore is hoisted in skips, the capacity of these skips ranging from 2 ¾ tons to 8 ¼ tons. At the Desloge plant, the ore is hoisted in 2-ton mine cars on self-dumping cages. All ore is hoisted at shafts adjacent to the various crushing plants, no ore being transported on the surface. Primary breaking at all the mills is accomplished with 9E Telsmith breakers. Preliminary screening is provided ahead of most of these crushers, either by station-

Jan 1, 1943

By P. H. Dudley

I HAVE taken the liberty of calling the researches herein mentioned industrial, to distinguish them from those strictly scientific, where every known appliance is used to insure accuracy in determining principles. The industrial researches are made to ascertain wherein we have failed to embody, in practice, the principles which have been fully demonstrated by the more purely scientific investigations. So far the researches have been mostly confined to the conditions of combustion as used in locomotive furnaces, although we have examined, to some extent, furnaces under marine and stationary boilers. The products of complete combustion are gases, and, knowing what we should have, it is at once shown by analyzing the products whether the desired reactions are taking place. In spite of imperfect furnaces, lack of system in the arrangement of grate-bars and exhaust nozzles, the results are not altogether vitiated, because the analyses are not closer than one-tenth of one per cent., as under the present conditions it is hardly possible to collect gas exactly under the same conditions at different times. All of our industrial operations have developed in the past few years so rapidly, nearly all of them paying, that, until within the past three years, comparatively little attention has been given to their economy outside of the profession. Great corporations have not asked and considered the question in earnest, can we utilize our heat so as to produce the same effect at less cost? The applications of heat are so extensive, entering into every branch of industry, the principal power used to carry on metallurgical processes, to conduct transportation, that its economical generation becomes of universal importance; in fact, its economical generation and application is the leading industrial question of the day. It is stated by those who have given the subject much attention, that in our best steam-engines not over 10 per cent of the theoretical value of the fuel is utilized, and upon locomotives it is far less, probably not exceeding under the most favorable circumstances 5 or 6 per cent. In recent experiments made with the dynagraph, in drawing trains upon the Lake Shore and Michigan Southern Railway from Cleveland to Erie, 95i miles, we found the force required to draw a stock train of 709 tons to be 2,498,396,320 foot-pounds, exclusive of the force to move the locomotive itself. We

Jan 1, 1876

By O. J. C. Runnalls, L. M. Pidgeon

J. M. Blocher, Jr. and I. E. Campbell (Battelle Memorial Institute, Columbus, Ohio)—Since the de Boer-Van Arkel process for making titanium metal involves a number of steps in a fairly compact unit, it is difficult to determine simply which of the steps is rate controlling. In any statement as to which step constitutes the rate-controlling process, qualifications appear to be in order. It is possible to design a reaction bulb in which any one of a number of steps is made to be controlling. I—With the filament removed some distance from the crude, as in the case of the authors' experiments, the interdiffusion of iodine and iodide may be controlling. 2—If, as is usually done, the crude metal is placed in a perforated cylindrical basket, or as a briquetted mass, in close proximity to the filament, the rate of deposition is increased (we obtained rates of deposition 5 to 10 times those cited in the authors' paper), and another rate-limiting factor, such as the reactivity of the crude, may take over. In this regard, we have noticed radically different rates of deposition with different crudes, and with crudes in various stages of exhaustion. 3—With a very reactive crude metal and with optimum practical geometry, still another process may be controlling. It is felt that this is a diffusion process in the immediate vicinity of the filament involving the fundamentally adverse situation of a net flow of particles away from the filament. The separate experiments on the reactivity of iodine with titanium are interesting but somewhat inconclusive. Data is still needed on the partial pressure of iodine in an operating decomposition bulb. A knowledge of the gradient of iodine partial pressure from the crude to the filament would be particularly enlightening. Optical absorption may be a useful technique here. Accurate measurements of the total pressure within a decomposition bulb under various conditions would be quite revealing. Preliminary measurements have been made at Battelle in following this line of attack. It is interesting to note that the authors' data on the temperature dependence of deposition rate indicate that the overall rate is not controlled by the kinetics of the decomposition reaction at the filament: TiI1 ? Ti + 4I Any reasonable estimate of the activation energy of this reaction would, if its kinetics were controlling, dictate a much greater temperature dependence than is observed here. The authors apparently attribute the drop in deposition rate (eventually to zero) with increased TiI4 pressure solely to a decrease in diffusion rate. However, there is an equilibrium factor involved here that must not be overlooked. As the partial pressure of TiI4 is increased, a point is reached where, due to the competing reaction of the tetraiodide with titanium to form lower iodides, the equilibrium partial pressure of titanium is reduced to the point that it equals the vapor pressure of titanium at the filament temperature and the deposition rate falls to zero. This effect would

Jan 1, 1953

By John McCoy, Edward Thimons, Kenneth Heller

As the working levels in domestic mines are developed to greater depths and work areas move further from the shafts, maintaining a safe and healthful working environment becomes more difficult. Increased temperature and humidity at greater depths becomes first a factor in productivity and then a threat to the miner's safety. Initially, a miner might develop listlessness leading to reduced productivity and reduced alertness. Continued overexertion can lead to heat stroke and possibly death. Mine ventilation engineers, therefore, must not only provide clean air to work areas, but also must provide cooled air. The following article describes the United States Bureau of Mines (USBM) and Foster-Miller's successful development of a high performance, low maintenance direct water to air contact heat exchanger for mine cooling. While heat problems frequently do not develop until mining operations descend below sea level, problems will arise any time mining penetrates high temperature rock. Hot fissure water will increase the severity of the situation, causing increases in wet bulb temperature - the temperature to which perspiring miners reject metabolic body heat. All energy expended in mining adds to the heat load which must be absorbed by the ventilation air. Just when the cooling capacity of ventilation air is needed most, adiabatic compression (autocompression) of air descending the shaft raises air temperatures 1.3g°C (2.5'F) to 2.94"C (5.3OF)/305m (1000 ft) depending on humidity. Increased temperatures decrease the ability of the air to absorb heat from the mine, and work area temperatures rise. Once forced ventilation air can no longer maintain safe work area temperatures, refrigeration methods must be employed. Many mines now use cooling coils for this purpose. A cooling coil uses refrigerated mine water to cool the air by passing the air through banks of copper tubing filled with cold water. Heat from the air is transferred to the water through the pipe with the aid of fins. Conventional water to air heat exchangers prove troublesome for many mines be- cause of the high levels of dust that are encountered, causing these exchangers to operate at relatively low efficiencies. A more satisfactory approach to work- place cooling is desired - one that offers reduced maintenance and increased cooling efficiency.

Jan 1, 1982

By William Lodding

Muscovite was the crystalline material used in the experiments discussed in this paper. It was both wet and dry ground for various periods of time. The effects (physical and chemical changes) produced in grinding are analyzed by use of thermal analysis. That grinding may change a crystalline material both in a physical and in a chemical sense has been shown by a number of authors in recent years. Mackenziel and Bartha2 reported the effects of careful grinding on muscovite, quartz, gypsum, dolomite, etc. Increase in specific surface produced by grinding implies increase in total energy of a system. Newly produced surfaces are chemically more reactive; dislocations may be introduced during grinding and, on the other hand, existing strain may be released by the same process, as shown by Holt, et a1.3 All these changes are easily detected by thermal analysis, but it is not easy to separate the multiplicity of effects registered and to arrive at quantitative interpretations. This paper is an attempt to analyze, by the use of thermal analysis, some effects produced in grinding. In differential thermal analysis (DTA) one measures the sum of all thermal changes occurring in a substance during heating or cooling; e.g., chemical changes, such as decompositions, synthesis, oxidation, reduction, etc., and physical changes such as phase transformations, changes in specific surface and thermal conductivity, strain release, etc. By thermogravimetric analysis (TGA), on the other hand, only chemical changes involving weight loss or gain are recorded. Similarly, gas evolution analysis (GEA) will register only reactions involving gas evolution. By performing two or all three of these methods of thermal analysis simultaneously and on the same specimen, one can separate the different effects registered and, by difference, evaluate their magnitude. The results of TGA are usually plotted as percent weight against furnace temp. When one differentiates weight against furnace temp, a rate of weight-change curve is obtained, and the resulting differential thermogravimetric (DTG) plots are similar in appearance to DTA thermograms for the same reaction. While the integrated area under a DTA peak represents enthalpy and can be expressed in calories per gram the area under the corresponding DTG peak represents the weight change which took place during a reaction. The similarity of DTA and DTG thermograms obtained from one material can be seen in Figs. 1 and 2. EXPERIMENTAL A Fisher mortar grinder and a porcelain mill with burundum balls were used for both dry and wet grinding. Muscovite was first carefully hand-filed and screened on 20 and 100 mesh. The middle fraction was considered essentially unaltered muscovite.

Jan 1, 1968

By A. Bar-Or, G. Hirsch, P. Wynblatt

The rates of nucleation and growth at various temperatures in U-0.45, 1.1, and 1.35 at. pet Cr alloys were determined, providing a qliantitative proo-f that the transformation under study is controlled by nucleation and diffusional growth. The linear relationship, log NV US 1/T2, suggests that the nucleation of the alloys is probably controlled by the classical law of nuclei formation. The established linear relationship, log G us 1/T, in the three alloys suggests that growth in each alloy is controlled by bidimensional nuclei formation. It was established that both the rate of growth and the rale of nucleation are retarded by chromium. Using classical formulae, sApN and sApG (the ß/a apparent interphase energies) were calculated from the nucleation and growth results, respectively. It was found that their values are of the same order of magnitude. However, why sApN is unaffected by the addition of chromium, while sApG increases with it, needs further clarification. In the last few years, an appreciable amount of research has been conducted into the mechanism of the ß —a transformation in uranium and uranium alloys. Recently, Burke1 reviewed the published work concerned with this transformation. He concluded that in dilute uranium alloys it is firmly established that, at high temperatures in the a range, ß decomposes by a diffusional process. However, he based his conclusion either on experiments dealing with the over-all transformation,2 or on qualitative results.3 It was felt that a better insight into the mechanism of transformation could be gained from the quantitative measurements of growth and nucleation rates, which we aimed to carry out in the present work. In a previous work,4 we have shown that a rim of a grains is formed during isothermal transformation at the high a range. The thickening of this rim with time was used for measuring the rate of growth in U-0.45 at. pet Cr.5 This method was also used in the present work for two more alloys. For meas- uring the rate of nucleation, a method of quenching and macroetching was developed to allow differentiation between a grains formed during isothermal transformation at the upper a range and those formed after quenching, Fig. 1. EXPERIMENTAL WORK AND RESULTS The Rate of Nucleation. The measurement of the rate of nucleation was effected by counting the num-

Jan 1, 1965

By Howard W. Miller, Charles R. L. Oder

Approximately 5000 tons of zinc ore a day was mined during 1943 in the Mascot-Jefferson City district in East Tennessee. This ore came from the Kingsport formation, a part of the Knox dolomite, of Ordovician age. The Kings-port is composed of 350 to 400 ft. of limestone and dolomite. Thin cherts, sandy layers and shales are numerous. Frequently, the limestones are altered to crystalline dolomite. The Kingsport is divisible into four main lithologic zones. These divisions are illustrated in an accompanying table, which gives detailed sections of the ore-bearing beds as found in the mines and shows the exact positions of the various ore zones within the formation. Key beds are described and the practical applications of stratigraphy in mapping, prospecting and mining are discussed. Introduction The Mascot-Jefferson City zinc district is in Knox and Jefferson Counties, in the Great Valley of East Tennessee. It extends from Mascot, I3 miles northeast of Knoxville, to Jefferson City, about 30 miles northeast of that city. The American Zinc Company of Tennessee is producing from five mines in the district, in which it has operated for more than 30 years. The only other important producer is the Universal Exploration Co. The approximate daily production of the district in 1943 was 5000 tons of sulphide ore, grading from 2.5 to 6 per cent zinc. Small amounts of oxidized ore are mined intermittently. The Knox dolomite has been described by various geologists,'-' but no detailed descriptions of the rock sections revealed by mining have been published. Rock units are not conspicuously different and careful study is required to distinguish them. Nevertheless, familiarity with the stratigraphy of the mineralized zones is essential to successful exploration and extraction of the ores; therefore the purpose of this paper is to give detailed stratigraphic sections as measured in the mines, to discuss their important features and to show their relationship to the stratigraphy of the district. Generalized Section Table I gives the most characteristic general features of the major stratigraphic units. The formation names given in parenthesis are locally and widely used terms, the correlations of which are not necessarily established. For this reason they are put in quotation marks and are replaced by more restricted terms. The names "Mascot" and "Kingsport" were adopted from local towns. They were chosen jointly by Josiah Bridge, of the Federal Geological Survey, and the senior author for use in their separate unpublished manuscripts describing the Knox dolomite in East Tennessee. Descriptions of the type sections may soon be published. The name "Longview" was first applied by Butts6 in Alabama.

Jan 1, 1949

By Ian William Wark, Alwyn Birchmore Cox

In defending the chemical theory of flotation, Taggart, del Giudice and Ziehl have criticized1 the views of those who prefer to attribute the effects of certain flotation agents to adsorption. Perhaps with some justification, they describe the latter term as the "haven of refuge of writers lost in a morass of shaky experiment and muddy thinking." We prefer to regard it, however, as a haven of refuge for writers who seek a conventional term to describe the formation of films of flotation reagents on solid surfaces, because in many cases it is not yet possible to specify the forces that hold them there. Originally, as Taggart and his associates state, adsorption connoted a concentration difference and nothing more. In recent years, workers in the field of surface chemistry have tacitly added other meanings, and they now speak of orientated adsorption of unimolecular films on a solid sub-strate, of chemi-adsorption, and of exchange adsorption. Thus the term adsorption may connote simply the Gibbs layer of excess concentration at the surface of a solution, or a unimolecular film at the surface of a solid. Perhaps this has led to the misunderstanding of Taggart, del Giudice and Ziehl concerning the relationship between surface tension and adsorption at solid surfaces. The change in "surface tension" accompanying adsorption at a liquid surface can be used as a measure of the adsorption, and the Gibbs equation as quoted by these authors correlates these two conceptions. But, to correlate two conceptions docs not necessarily imply an attempt to explain either, although sometimes such an "explanation" is carelessly inferred. Use of "surface energy per unit area" instead of the numerically equal but more difficult and less definite conception of "surface tension per unit length " would lessen many of the present difficulties. (Compare with Adam.2) At interfaces involving a solid phase, neither '" surface tension " nor " interfacial tension "can have any meaning, but the conception "interfacial energy per unit area" call be understood by anyone who is familiar with the concept of free energy. While it is true that surface energy cannot be directly measured at a solid surface,

Jan 1, 1939

By W. T. Isbell

In the Parkes process of lead refining, after desilverization has been completed by means of the addition of zinc, there remains in the lead from 0.5 to 0.6 pct zinc. At this stage in the refining operations virtually all impurities are reduced to refined lead specifications except zinc and antimony. All excess copper, nickel and cobalt have been removed by the zinc additions. The silver remaining should not exceed 0.1 oz per ton. It then remains only to remove the zinc and antimony in order to produce refined lead. At the Herculaneum plant of the St. Joseph Lead Co., practice formerly was to complete the refining by means of oxidation in a reverberatory furnace. This process consisted of heating the lead to 1400O to 1500OF and allowing it to come in contact with excess air passing over the surface of the lead and periodically agitating the bath of lead with air. This procedure not only resulted in the loss of zinc but of a considerable quantity of lead converted to the oxide in the form of dross and fume. The fume, collected in the baghouse, together with the dross was returned to the blast furnace, thus adding appreciably to the circulating load on the blast furnace and refinery. In addition, operation and maintenance of the reverberatory furnace were expensive and required the performance of disagreeably hot and somewhat hazardous work. The process of dezincing with high vacuum was developed at this plant as a substitute for the oxidation process and finally led to lower operating costs, the practical elimination of dross and fume and the direct production of metallic zinc, which is very suitable for re-use in the desilverization process. Essentially this process consists of subjecting the lead to high vacuum, in a kettle provided with means for heating, a bell-shaped member open at the lower end so constructed that it can be immersed in the molten lead, and means for evacuating the interior of the bell and for sealing an agitator. Metallic zinc is thus produced and collects on the upper cooled part of the bell member. This metallic zinc is periodically removed and re-used in the desilverization process. The process is quite simple. It is conducted at a low temperature, thus permitting the use of iron equipment, and shows a material saving in refining costs over the old method. Equipment and Its Uses Degincing Machine.—The equipment employed in this process consists of a dezincing machine, a steel kettle of 120 tons capacity, a vacuum system and equipment for handling the dezincing machine (Fig 1). The dezincing machine consists of a compact assembly, suitable for handling with an overhead crane, consisting of a treating chamber and the agitating mechanism. Treating Chamber.—The treating chamber is a bell-shaped shell (4), similar in shape to a hemispherical kettle with a lid

Jan 1, 1949

By Joseph E. Worthington

Many thousands of years ago when our earliest ancestor first swung out of a tree, picked up a rock, and threw it at what he hoped might be his lunch, the minerals industry, in a manner of speaking, was born. It was then a very long step indeed to the primitive metal industry of our early civilizations, for we know that precious metals were accumulated and some metal objects were produced several thousand years ago. Prospecting, or "exploration" to use the modern euphemism, consisted of little more than outcrop examination and the use of a gold pan, and it probably did not change much from our earliest civilizations until relatively recent times. In a general sense, all the early explorers of North America were also prospectors, for mineral wealth was certainly one of the goals of the first pioneers and settlers. The earliest pioneers didn't do too badly either, for they discovered copper and iron in various places in the Appalachians and Michigan, gold in the Southeast Piedmont and many mineralized areas in the Southwest. In most places these were outcropping ores or gossans, and the prospecting was incidental to the arduous task of ekeing out a living in a new land. It was the explosive discovery of rich placer gold deposits at Sutter's Mill in California that caught the public fancy and precipitated the establishment of prospecting as a full-time occupation. After the end of the Civil War in 1865, full-time prospecting became an important occupation and continued as such for almost three generations. Prospectors equipped with picks, shovels, gold pans and four-footed transportation swarmed all over what are now our Western States, discovering thousands upon thousands of mineral showings-and certainly most of today's large mining districts. Our vigorous western mining industry is a tribute to the courage and persistence of these men. The techniques of these picturesque prospectors, however, were essentially the same as those of their predecessors-examination of every outcrop and assiduous use of the gold pan. The great increase in discovery at this time was therefore due to increased activity rather than to different techniques. An important result of this in- creased prospecting was the growth of interest in geology. It was during this period that the U.S. Geological Survey began to grow. Many of the major mining districts were mapped, and geological studies and projections began to have an impact on further ore discovery. Ore search and development gradually became more geologically oriented and the geologist became a fixture in most mining camps by the 20th century. The development of mass-mining techniques in the early part of the century also changed exploration concepts.

Jan 1, 1971

By Donald C. Bradford

THE place of geophysics in the curriculum of a college or an engineering school has been much discussed. There is uncertainty as to whether the graduate may be called a "geological geophysicist" or a "geophysical geologist." Some have used the term "geophysical engineer." The question of the specialized undergraduate curriculum versus a general undergraduate training in the parent sciences with the addition of cultural electives has been and is still being argued. The literature during the past 10 years shows that there are two rather definite schools of thought on this subject. The prospective employer, engaged in active geophysical exploration, visualizes the graduate in terms of the routine work he will do in the field. The school administrator, grounded in many years of tradition in the cultural type of education, visualizes the graduate in terms of his position in a political and cultural society as well as in his work as a professional geophysicist. Both are right and both wrong. A third school of thought, that of the student himself, has been almost totally ignored. It would seem best, for the purpose of this paper, to treat these various points and allied material separately, and then to integrate the conclusions as a set of conditions that should be fulfilled as far as possible in the ideal curriculum. At the end the relationship of our findings to the curriculum that has been tentatively adopted at the University of Pittsburgh will be considered. DIVISIONS IN DEFINITION OF FIELD OF GEOPHYSICS Geophysics is that field of science in which geological and earth problems are solved with the use of physical and chemical techniques. Altogether too much attention has been paid to the artificial separation in this science of the commercial applications from the so-called "pure" or academic geophysics. The only real difference in the two types of work is one of scale of operations. In the commercial field the scale is large in terms of financial backing, immediate economic importance, and speed of operations. In the academic field the scale is large in terms of breadth of interests, in eventual economic importance, and length of time allowable for theoretical investigations. In exploration work the scale is small in terms of dimensions, since the methods are applicable only to the outer 20,000 ft. or so of the earth's. crust. In academic work, the student is not pressed for results of immediate economic importance, and therefore can afford to spend more time on problems that seem unimportant at the time. In the sense of background knowledge of the parent sciences necessary to the geophysicist, no essential difference can be found. Physics, chemistry, geology, and mathematics together, and in their proper proportionate amounts, form the matrix from which geophysical ideas and methods may spring.

Jan 1, 1942

By C. E. Birchenall, M. H. Davis

The rate of oxidation of titanium in the temperature range 650° to 950°C has been measured. 'The linear rate law obtained is explained by interface reaction control of the process. Tracer experiments indicate the oxygen diffuses in at least one phase of the scale. THE kinetics of oxidation of titanium, principally at low temperatures and under varying oxygen pressures, have been reported.¹,² In the present investigation the rates of oxidation of titanium have been determined by the gravimetric method in the temperature range 650" to 1000°C under 1 atm of oxygen. Some of the scales formed were powdered and an endeavor was made to identify the phases present by X-ray diffraction. Alexander and Pigeon1 ascribe a logarithmic rate law to the growth of thick films formed at temperatures up to 565"C, and Gulbransen and Andrew' suggest that the parabolic rate law holds up to 600°C. In both cases large initial deviations from those relationships are apparent and no explanation is offered. In the present experiments it is shown that a linear rate law holds in the temperature range 650" to 1000°C, and it is suggested that the initial deviations observed are due in part to a spurious surface area effect and also to the high solubility of oxygen in titanium metal. Positive information on the mechanism of oxidation is not available, but oxygen ion diffusion through the lattice is inferred from the re- sults of trace experiments. X-ray analysis of the scale confirms Gulbransen and Hickman's' observation on the presence of rutile TiO². Experimental Details The titanium used in these experiments was prepared by the reduction of titanium tetrachloride with magnesium and was used in the form of rolled sheet. Samples approximately 0.040x0.5x0.75 in. were cut and polished to a fineness of 4/0 on metal-lographic polishing papers. Individual samples, suspended on a platinum wire, were lowered into the hot zone of a furnace, in vacuo, by means of a winch, and oxygen was admitted after the desired temperature was attained. The increase of weight of single samples oxidized for fixed times at certain temperatures was determined by weighing the sample before and after oxidation on a chemical balance. In these instances the sample was used for only one time at one temperature. In some cases the course of oxidation was followed by attaching the sample to a sensitive spring balance and noting periodically the extension of the spring with time of oxidation. Kirkendall type experiments were carried out by marking the surface of the titanium prior to oxidation with a solution containing radioactive silver. After drying, the specimen was heated in vacuo to decompose the silver nitrate used, leaving a small amount of metallic radioactive silver on the surface. Following oxidation, these samples were mounted, ground, and then placed in intimate contact with

Jan 1, 1952

By R. S. Archibald

The subject of this paper is particularly appropriate, since Daniel C. Jackling was active in early exploitation of taconites on the Mesabi Range and contributed greatly to their later economic development. After his success in developing the low grade porphyries in the West he looked for more worlds to conquer, and so undertook the concentration of low grade taconites, from which he hoped to produce commercial ore. Mesabi Iron Co., organized in 1919, actually did produce merchantable sinter from taconites in 1922. The enterprise did not prove commercial at the time, as cost of production was high and the surplus of iron ore in the Lake Superior District already contributed to a low market price, but this same property has since been developed by Reserve Mining Co. The work done by Jackling had much to do with the success of this later venture. Iron ore was first discovered on the Marquette Range in Michigan in 1845. The first ore from this range came from the old Jackson mine in Negaunee in 1848. During these early years this property and others on the Marquette produced limited tonnages for transportation to Lower Lakes and for consumption by charcoal furnaces in the area, where a plentiful supply of hardwoods furnished the charcoal for iron smelting. The Marquette and other ranges tributary to Lake Superior did not produce much ore for transportation to Lower Lakes until the locks at Sault Ste. Marie were constructed, but from the time the first lock at the "Soo" was completed in 1855 these ores were transported through the locks to consumer centers in the East. The Marquette Range has a history of continuous production from 1848 to the present day. In 1877 the Menominee Range was discovered at the location of the old Penn Mines near Vulcan, Mich. There were further discoveries of ore on the old Menominee Range and at Florence, Wis., in 1880 and at Iron River and Crystal Falls, Mich., in 1882. Penn Mines continued in operation from the date of their discovery until they were finally exhausted by Pickands-Mather in 1945, but operations still continue on the Menominee in the Crystal Falls and Iron River districts. Ore is shipped to a lake port at Escanaba, Mich.

Jan 1, 1960