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By M. E. Wadsworth, R. C. Peterson, W. M. Fassell

The temperature and pressure dependence of the reaction of tantalum in oxygen were investigated from 500° to 1000°C at pressures from 10 mm Hg to 600 psi total oxygen pressure. Tantalum was found to oxidize linearly under the above conditions. Three distinct regions of temperature dependence were found with different energies of activation. From 500° to 600°C the rate of oxidation of tantalum was found to be essentially independent of the oxygen pressure at the pressure investigated. The oxidation rate increases rapidly with an increase in pressure from 600' to 800°C. The dependence of the oxidation rate on the bulk concentration may be expressed by V = k'?, where k' is the specific rate constant and ?=k1Co2/(l + K1Co2), where k, is the equilibrium constant for the adsorption of oxygen on tantalum. ONLY a limited amount of data has been presented in the literature on the oxidation behavior of tantalum metal. Some values of its oxidation rate were reported in the Corroston Handbook' and by McAdams and Geil.' The first extensive investigation of tantalum was the work of Gulbransen and Andrews." They determined the reaction rates of tantalum in O2 and N2. Their results indicate that this metal follows the parabolic law in the temperature range of 250" to 450°C in O2 at pressures of 7.6 cm Hg with an activation energy of 27,400 cal per mol. In nitrogen, the metal follows the parabolic law from 500" to 800°C at 7.6 cm pressure. All experimental determinations were of 2 hr or less duration and deviations from the parabolic rate conceivably could occur at longer times. A spectrophotometric study of the oxidation of tantalum by Waber, Sturdy, Wise, and Tipton' indicated good agreement between this method and the microbalance technique. The experiments were conducted in air from 220" to 350°C. The metal was found to follow the logarithmic law up to 320°C and the parabolic law at higher temperatures. The activation energies in the logarithmic region were reported as 12.57 kcal per mol and 12.0 kcal per mol, respectively, for the microgravimetric and spectrophotometric methods. In the parabolic region the activation energy was found to be 27.2 kcal per mol, in good agreement with the value of Gulbransen and Andrews." The present paper is concerned with the behavior of tantalum from 500" to 1000°C in oxygen at pressures ranging from 1/2 to 40.8 atm pressure. Earlier preliminary data by McKewan5,6 indicated the following facts concerning the behavior of tantalum: 1—At temperatures from 500" to 600°C, the metal followed the linear law. 2—At 575°C the rate of oxidation was found to increase with O2 pressure. 3—The Arrhenius plot in this temperature region was nonlinear. The nonlinearity of the Arrhenius plot was indicative of a more complex behavior than originally suspected for this metal.

Jan 1, 1955

Jan 1, 1925

Jan 1, 1934

By Henry Louis

Four alloys of gold and silver were prepared, containing the metals in the following proportions by weight: I. Gold:Silver::1:2.62.

Jan 1, 1894

Jan 1, 1917

The Jeffrey operation of Canadian Johns -Manville Co. , Ltd., at Asbestos, Quebec, is considered to be the world's largest asbestos mine. It accounts for approximately 37% of Canadian production of chysotile asbestos and about 13% of world production. Rated capacity is over 600,000 stpy (540,000 mtpy) of fiber, of which well over 90% is exported to the United States and seventy other countries. During the early 1970's the company completed a five-year modernization and expansion program which included the installation of a unique 72 in. by 93 in. gyratory crusher to handle the extremely blocky serpentinized peridotite ore. Because of the large diameter of this crusher the top ring of the shell was made in two halves which were bolted together. Hundred-ton trucks dump from two sides of the crusher into the 200 st (180 mt) dump pocket which is equipped with dust collecting ducts in the walls of the other two sides. The installation was designed to accommodate the eventual use of 200 -ton trucks. Crushed ore at a. size of 7 ½ in. (191 mm) falls into a uniquely designed crushed ore pocket equipped with three sloping steel sides and one vertical side, which make it totally live. Infrared heaters installed in back of the hopper sides prevent the ore from sticking to the steel. Another interesting feature is an eccentric removal bridge which is permanently mounted inside the crushed ore pocket. The two halves of the bridge are let down by electric winches to form a platform on which the eccentric cart travels and from where maintenance is done. Level indications in the crushed ore pocket are by radioactive indicators. Under the crushed ore pocket is a 72 in. by 28 ft (1.83 m by 8.5 m) apron feeder which operates at 7. 2 to 50 fpm (2. 3 to 15. 3 mpm). Crushed ore is discharged to a picking belt for tramp removal. A crossbelt magnetic separator is also mounted over this belt. Permanently mounted belt reels are also situated over the picking belt to facilitate the changing of this unit. A 60 in. (1. 52 m) wide takeaway belt then elevates the crushed ore to t.he surface facilities. Instead of discharging to a crushed ore stockpile, the takeaway conveyor delivers the ore to a 300-ton distribution bin. The ore is then screened and secondary crushed; and the plus ¾ in. (19 m) is "stored in a 3,000 ton bin while the minus ¾ in. is dried and then sent to storage. This system of directly screening primary crushed ore is similar to that used at both the Endako molybdenum and Gibraltar copper operations in British Columbia. While it would seem connecting processing equipment directly to a primary crusher would have an adverse effect on the crusher availability, the 94% of scheduled time this crusher

Jan 1, 1978

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Jan 1, 1938

Jan 1, 1890

By D. H. Bacon

Our Transactions contain so many suggestions of apparently trivial, yet really important, contrivances for the saving of time and

Jan 1, 1893

By John J. McCabe

INTRODUCTION Over the years, Congress has written into the Internal Revenue Code various provisions aimed at lessening at least one financial burden faced by taxpayers in the mining industry - the federal income tax burden. These provisions include the election to deduct exploration expenses, the election to defer deduction of development expenses, and the percentage depletion deduction. Careful tax planning from the very beginning of a mining venture is essential in taking maximum advantage of these tax benefits. A major decision to be made is the choice of organizational structure. (For a more detailed discussion of this subject, see McCabe, John J., "Developing Structures for Investments in Mineral Property," New York University Institute on Federal Taxation, 42 NYU 24, 1984). One such structure is the use of multiple corporations, with mining activities conducted by one corporation and nonmining activities, such as manufacturing, financing and administration, conducted by the other corporation. This technique, which will be discussed in detail below, can be particularly advantageous in delaying recapture of previously deducted exploration expenses and in maximizing depletion deductions. TAX BENEFITS IN MINING Exploration Subject to certain restrictions discussed below, exploration expenditures (i.e., expenditures paid or incurred during the taxable year for the purpose of ascertaining the existence, location, extent, or quality of any deposit of ore or other mineral, and paid or incurred before the beginning of the development state of the mine are deductible at the election of the taxpayer (Section 617(a)).* Were it not for this option, exploration expenditures would be required to be capitalized and recovered through depletion, after production begins. Exploration of a mineral deposit can be very costly and may not result in commercial production for some time. If the taxpayer has income to he offset by the deductions, a mining venture can usually be structured in such a way as to allow the offset of mining losses against the other income. With today's high interest rates, this election can be quite valuable in present value terms. Corporate and noncorporate taxpayers are subject to different restrictions on this tax benefit. Corporations may elect to deduct only 85 percent of eligible exploration expenditures (Section 291(b)). (The Tax Reform Act of 1984 reduced this to 80 percent effective for expenditures after December 31, 1984, in taxable years ending after such date). The remaining 15 percent (20 percent after December 31, 1984) is capitalized and recovered at the same rate as five-year ACRS property (Section 291(b)). Individual taxpayers are not subject to this 85 percent rule; however, any amount deducted in excess of ten-year straightline amortization is a tax preference item for individuals (Section 57(a)(5)). Individuals may avoid the tax preference by electing to capitalize exploration expenditures and amortize them over ten years (Section 58(i)). In order to prevent the taxpayer from, in effect, converting ordinary income into capital gain by selling property that has given rise to exploration expense deductions, the Code requires recapture of such deductions upon the occurrence of certain events (Section 617): 1. Upon disposition of the property, adjusted exploration expenditures are recaptured to the extent of gain realized on the disposition (Section 617(d)). 2. If the property is leased, the lessor is disallowed any depletion deduction until his adjusted exploration expenditures have been recaptured in the form of foregone depletion deductions (Section 617(c)).

Jan 1, 1985

Recognizing the fact that the problems of the committee named by the Board to prepare the "official ticket" for officers and Directors of the Institute are various and difficult; and desiring to assist this committee by setting forth some of the principles that should guide the committee and some of the qualifications that should be required of candidates, the following instructions are formulated and the Secretary is directed to publish them in MINING AND METALLURGY concurrently with the publication of the names of each newly appointed Nominating Committee and to send a copy to each member of the Committee

Jan 1, 1943

By T. D. Yensen, R. K. McGeary

While we have not been primarily interested in the determination of hydrogen in the alloys that we have been dealing with, we arc very glad to cooperate in this symposium on sampling and analysis for hydrogen, as we can never tell when we may find it desirable to perform such analyses. Vacuum-fusion Method Our primary interest has been oxygen and carbon, in the analysis of which we think we have become very proficient. Our oxygen-analyzing apparatus is of the vacuum-fusion type (Fig. I). This employs Dr. Derge's type of graphite cruciblc and slit sleeve, with graphite powder between, for heat insulation (Fig. 2) supported in a clear quartz bulb connected to the Pyrex glass system by means of a carefully made ground joint. The latter is kept cool by means of an air blast from a circular copper tube surrounding the joint. The crucible is heated by high-frequency induction and the 24 one-gram samples successively dropped in from the horizontal tube at the top by means of a magnet. The gases (H², CO, N2) are passed through the CuO catalyst held at 300°C. (converting CO to CO²I, H² to H²O) and the CO² and H2O frozen out in the main liquid air trap, while N2 is evacuated. At the end of the operation, shown by the termocouple vacuum gauge indicating a pressure of 10-4 mm. Hg, the analyzing system is isolated by means of the mercury cutoffs, and the CO² and H2oare determined by transferring first the CO2 and then the HzO to the small trap at the right. This is done by placing liquid air on the small trap, then removing the liquid air from the large trap for one minute, which is sufficient to evaporate the Co2 and transfer it to the small trap. The CO2 is then measured by closing the mercury cutoff at the extreme right, removing the liquid air from the small trap, warming it up to room temperature, adjusting the mercury level to one of the three marks on the glass tube (corresponding to three volumes calibrated so that I mm. Hg of CO² corresponds to 0.001, 0.002 and 0.010 mg., respectively, of oxygen) and finally reading the pressure. Liquid air is now replaced on the large trap, the mercury cutoff at the right opened, transferring the COz back to the large trap. The cutoff to the pumps is then opened, the liquid air removed for one minute, thus evacuating the CO², the pumps again cut off and the H2 O transferred to the small trap as before, except that it is now necessary to warm the large trap with a Bunsen burner in order to evaporate all the H2O. This requires about three minutes, as the inner tube must be heated to at least 100°C. In order to prevent H²O from being adsorbed on the glass walls, the glass tubing beyond the catalyst (i.e., to the right in Figs. I and 3) is kept heated to about 150°C. by means of Nichrome ribbon as shown in Fig. 3. For a I-gram sample the above amounts of oxygen (0.001, 0.002 and 0.010 mg.) 35

Jan 1, 1945

By Fred W. Gordon

It is my purpose to call attention to the close approximate correctness of certain coefficients and formulas concerning the flow of gases, and their applicability to the practical construction of flues and

Jan 1, 1886

By Y. L. Yao

The solubility limit of oxygeu in a titanionn at 850°C has been determined by magnetic measurements as 12.5 + 0.5 pct (29.0—30,9 at. pct). Also in the susceptibility-co~centmtion curve, there is n distinct but not sharp maximum at 19.0 * 0.5 z~t pet (40.5--42.1 at. pct), which indicates the presence of the 6 phase. The magnetic susceptibilities of the alloys of the titanium-oxygen system were determined byEhrlich in 1939.' is alloys were prepared by sintiring mixtures of titanium and its oxide at high temperatures. On the titanium-rich side, despite the fact that the alloy compositions he measured crossed two phase boundaries, the limited results obtained

Jan 1, 1960

By F. M. Sandoval, R. E. Ries, J. F. Power

Returning the original soil material to the surface of smoothed mine spoils is a practical means of restoring agricultural productivity. Research has established that high-sodium spoils in North Dakota: (1) must be covered with about 70 cm of soil material to achieve maximum production; (2) top-soil must be segregated and spread separately from subsoil; (3) potential production depends on the quality of the soil material returned; and (4) erosion and upward salt movement must be controlled for sustained production. Erosion is best controlled by reducing final grades as much as possible during the smoothing process followed by prompt establishment of vegetation.

Jan 1, 1980

New York Meets first Wednesday after first Tuesday of each month. DAVID H.-BROWNE, Chairman, JOHN H. JANEWAY, Vice-Chairman. F. E. PIERCE, Secretary, 35 Nassau St., New York, N. Y. P. A. MOSMAN, Treasurer. LEWIS W. FRANCIS. Boston Meets first Monday of each winter month. HENRY L. SMYTH, Chairman. . ALFRED C. LANE, Vice-Chairman. HENRY A. WENTWORTH, Secretary-Treasurer, 60 India St., Boston, Mass. ROBERT H. RICHARDS, ALBERT SAUVEUR. Columbia Holds four sessions during year. Annual meeting in September or October. FRANK A. ROSS, Chairman. RUSH J. WHITE, Vice-Chairman. LYNDON K. ARMSTRONG, Secretary-Treasurer, P O. Drawer 2154, Spokane, Wash. FREDERIC KEFFER, FRANCIS A. THOMSON.

Jan 11, 1915

By G. M. Schwartz, J. N. Gundersen

John W. Gruner (Professor Emeritus, College of Science, Literature, and the Arts, Dept. of Geology, University of Minnesota, Minneapolis) — It is surprising that two men as well acquainted with the taconite rocks of the Mesabi District as Drs. J. N. Gundersen and G. M. Schwartz should have concluded that the taconite of the Eastern Mesabi before the intrusion of the Duluth gabbro consisted largely of quartz and magnetite. These minerals were "locally reconstituted" into "a wide variety of silicate mineral assemblages" by the gabbro. It is well known, of course, that the silicate mineralogy of the Eastern Mesabi ('about 14 miles in length) is quite different from that of the Main Mesabi which is over 60 miles long. The change from one to the other is abrupt and cannot be attributed to any other cause than the thermal effects of the gabbro. Are we to assume or believe that the taconite of the Eastern Mesabi was radically different from that of the Main range before the gabbro metamorphosed it?

Jan 1, 1962

By Reed W. Hyde

SOME information has been published on the sulphur dioxide concentration of gases from Dwight-Lloyd machines sintering lead ores but most of this relates to the customary practice in which the charge is relatively high in lead and is sintered in two passes over the machine. It is thought, therefore, that the following observations on sintering in one pass a low-lead, low-sulphur charge may be of interest. The data were obtained in sintering lead sulphide flotation concentrates mixed with minus 20-mesh oxide ore, the mixture carrying 16.8 per cent Pb and 5.3 per cent S. No returns were used because of the limited amount of sulphur available as fuel, but the mixture pelletized readily to make a satisfactorily permeable bed on the sintering machine. As there was a possibility that the SO2 might be utilized, a series of runs was made to determine the concentration of SO2 in the gases at different points along the wind box, and the effect on this concentration of changes in the wind-box vacuum. Several runs each were made with vacuums (as measured in inches of water at the wind box) of (1) 2 to 1 3/4 in., (2) 4 to 3 1/2 in. and (3) 6 to 5 1/8 in. The averages of the determinations from each series are platted on the graph (Fig. I). The vertical scale shows the percentage by volume of SO2 (as determined by the Reich method), and the horizontal scale shows the time expressed as percentage of the total sintering time. Sintering was considered to be complete when no SO2 could be detected in the gases. In all cases the depth of bed was 4 1/2 in. and the weight of dry charge per square foot of hearth area was 45.2 lb. Other data are given in the table. The volume of gases corresponding to the several points along the wind box at which SO2 determinations were made could not be measured, but has been calculated from the SO2 content and sulphur elimination on the assumption that the volume is uniform throughout the sintering period. This is not strictly true, as with a given vacuum the volume will usually drop slightly toward the middle of the period and increase toward the end. However, this assumption is a reasonable approximation. Several interesting features are brought out by these data. In general, the published data on SO2 concentration in sintering under ordinary conditions show a high SO2 concentration in the early stages followed by a rapid decrease in concentration and with relatively little SO2 in the gases from the last half or third of the operation. In other words, the greater part of the sulphur elimination is obtained in the first third or half of the period. In these runs, the 6-in. vacuum, which approximates the usual operating condition, gives a curve that follows this customary pattern. Maximum SO2 concentration is obtained 2 ½ min. after

Jan 1, 1942

By Carl R. Christiansen, James J. Scott

Advance mine planning, coupled with good mining practice, can be employed to develop underground space in stone mines for future industrial usage. To assure the developer the maximum return on his investment, initial planning should consider all aspects of the commercial operation, including surface layout, mining, and underground industrialization. The modular concept of mining to compartmentalize the space offers several advantages over conventional methods. Some expenditures can be considered as mining costs with a reduction of profit from stone production while lowering the capital requirements for conversion for usable space.

Jan 1, 1977

By Reichmuth, Donald R.

Most brittle solids are relatively weak in tension and this weakness can be very significant in determining their performance in structures and excavations. Consequently, accurate knowledge of the tensile strength of brittle materials has long been recognized as important. In the past, measurements of the tensile strength of materials such as concrete, ceramics, and particularly rock have been hindered by problems encountered in fabricating test specimens and in accurately loading them. These difficulties have resulted in a scarcity of published tensile strength data. This can be readily seen in tabulations such as Wuerker's "Annotated Tables of Strength and Elastic Properties of Rocks.

Jan 1, 1968