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By Larry Kaufman

A useful method for estimating the entropy of NaCl type compounds has been developed by combining the Debye theory of specific heat with the Lindemann formula. This method pemnits calculation of the entropy from a knowledge of the atomic weight, atomic volume, and melting point of the compound. Comparison of the calculated and observed entropies of 35 NaCl type compounds over a wide temperature range yields good agreement thus establishing the usefulness of the method. Application of the method to other crystal types is also discussed. KUBASCHEWSKI~ has suggested a useful method of estimating the enthalpy of formation of inter-metallic compounds from a knowledge of the crystal structure, lattice parameter, and heats of sublimation of the component elements. This method is quite valuable in predicting the tendency for compound formation in a given system and is of particular value in considering systems for which no experimental data are available. In order to supplement the enthalpy calculation afforded by Kubschewski's method, it would be of value to be able to estimate the entropy of compounds so that the entropy and free energy of formation could be evaluated. Although a considerable body of such data determined by calorimetric and equilibration techniques exists at present, the difficulty of making such measurements (particularly at high temperatures) and the ever increasing number of new compounds which are of interest make the desirability of such a computational method clear. This paper deals with a method for calculating the entropy of a compound from a knowledge of the atomic weight, atomic volume, and melting point. Since these data are generally easier to determine and therefore more readily available than thermo-dynamic data, they should provide an additional tool in estimating the stability and reactivity of compounds at high temperatures. I) THE ENTROPY OF PURE METALS As a first approximation, the specific heat of a pure metal can be represented by a sum of terms where C,($/tI is the vibrational specific heat calculated on the basis of the Debye theory, lo4 TC, (0/T) is an approximation to the Cp - C, correction. T is the electronic specific heat, and Cp (p) is the magnetic specific heat. Although the Debye theory does not provide a complete description of the vibrational specific heat, i.e., the Debye temperature 0 is not a constant, it does provide a good approximation when used properly. Blackman6'7 has written several reviews on this subject discussing the different values of 0 determined by various methods (specific heat, X-rays, elastic constants, electrical resistivity, and so forth), as well as the observed temperature dependence of 0 with T. In the present case the 0 in Eq. [I] naturally refers to the specific heat 0. The variation of Debye 0 (as determined from specific heat measurements) with temperature is observed to exhibit its most radical behavior at very low temperatures. At higher temperatures the 8 values are observed to become more nearly constant. Blackman6'7 has presented the variation of 0 with temperature for several metals. His tabulation is reproduced in Table I. Reference to Table I shows that above a certain temperature level, 0 remains fairly constant. The value of 0 which is most useful in computing the specific heat, and hence the entropy, is the value of 0 in the range 0/6 « T « 0. In 1910, Lindemann' suggested a relation for estimating Debye 0 values. According to this formula, where V is the atomic volume, T is the melting point in 'K, M is the atomic weight, and CL is a constant. Mott and Jones9 present this formula and state that there is at present no satisfactory theoretical explanation, but that it does have an empirical basis. By using the valuesof 0 in Table I along with known1' values of M, T, and the molar volume VM, where the Lindemann constant can be evaluated. This

Jan 1, 1962

By Gerald W. Elger

This report compares the quality of zirconium metal prepared by batch reduction of zirconium tetrachloride by (1) sodium, (2) magnesium, and (3) mixtures of sodium and magnesium. Criteria for quality are based on chemical analyses and hardness testing of zirconium arc-melted from sponge. The best quality zirconium with respect to low oxygen content and hardness numbers was prepared by reaction of zirconium tetrachloride with a mixture of sodium and magnesium. It was found that this reaction could be successfully carried out by two methods: (1) addition of sodium and magnesium before the initial reaction and (2) periodic injection of sodium during reaction of zirconium tetrachloride with magnesium. The largest quantity of metal was found to be recovered from experiments in which a mixture of sodium and magnesium was used. Magnesium appeared to be a better reductant than sodium because magnesium-reduced zirconium contained less oxygen and exhibited lower hardness numbers than sodium-reduced metal.

Jan 1, 1962

By John C. Sawyer

A brief review is given to show that catastrophic oxidation of stainless steel in the presence of lead oxide is similar in many respects to catastrophic oxidation as caused by MoO3 and V2O5, Experimental data are presented to show that lead oxide accelerates the normal oxidation process of stainless steel by chemically altering the normally protective oxide film formed on the base metal. Data are given to show that similar reactions occur during oxidation of stainless steel in the presence of MOO3,and V2O5. THE mechanism by which pure metals oxidize at high temperatures has been the subject of intensive research for many years and much has been accomplished towards understanding the processes involved. The mechanisms by which alloys oxidize have also been investigated, but due partly to the fewer number of investigations and partly to the complexity of the oxide systems present, available knowledge is not as extensive as with pure metals. When oxidation processes are further complicated by atmospheres contaminated with sulfide, halide, or oxide vapors, the knowledge of fundamentals becomes meager or altogether lacking. Thus, it is not surprising to find that the catastrophic oxidation of stainless steels in metal oxide vapors of MOO, and V2O5 is not a well understood phenomenon despite the fact that a number of investigations have been undertaken. The literature in dealing with the subject of catastrophic oxidation is primarily concerned with the effects of MOO3 and V2O5, but does mention that other metal oxide vapors, one of which is lead oxide, appear to promote a similar type of accelerated oxidation. While this latter effect is virtually unknown, the deleterious effect of lead oxide is of considerable commercial importance, as it is believed to be one of the fundamental reasons for exhaust-valve failure in gasoline engines. For this reason studies have been in progress for many years attempting to better understand the mechanism involved. Modern exhaust-valve alloys"2containing 20 to 25 pct Cr plus nickel and/or manganese are in effect high-grade austenitic stainless steels exhibiting ex- cellent oxidation resistance in air at exhaust valve operating temperatures of 1100° to 1700°F; yet these same alloys are prone to corrode during engine service because of the conditions attending their operation. These conditions are such that the valves become coated with deposits of complex lead compounds mainly derived from gasoline additives of tetraethyllead, ethylene dibromide, and ethylene dichloride. Literature searches3-7 and discussions with various investigators show that considerable difference of opinion exists as to the nature of the lead-bearing deposits found on the surface of exhaust valves and the atmospheres to which they are subjected; yet, all seem to generally agree that corrosion, a gradual transformation of alloy to nonmetallic products of corrosion, is a consequence of the presence of lead compounds. This majority opinion seems to be substantiated by laboratory engine tests which show that corrosion does not occur to any appreciable extent when lead-free fuels are used. The first observations of catastrophic oxidation reported in the literature were probably made by pfeil,8 but it was Leslie and Fontana9 who undertook the first detailed study of the phenomenon. Their work was chiefly centered on the acceleration of oxidation which took place when stainless steels containing more than 3 pct Mo were heated in air with restricted circulation. These investigators reported that the presence of other oxides near the surface would further accelerate the rapid oxidation which occurred. While they recognized that the effect was attributable to the presence of molybdenum, it was Rathenau and Meijering" who emphasized the fact that the presence of molybdenum in the alloy was incidental to the presence of MOO3 vapor in the atmosphere surrounding the specimens. Evans,11 as well as Cunningham and Brasunas 12 studied similar

Jan 1, 1962

By William J. Campbell

Evaluation by the Bureau of Mines of published expansion values for magnesium oxide shows significant variation in values, which may be attributed to sample variables, experimental errors, or systematic differences between measuring techniques. To eliminate the sample variable in measuring expansion, thermal expansion characteristics of a high-purity polycrystalline magnesium oxide were determined by 21 cooperating laboratories using one or more of the following techniques; X-ray camera, X-ray diffractometer, dilatometer, interferometer, and telemicroscope. All expansion values were corrected by the author to a single reference temperature of 25° C. Linear expansion was expressed as a power series in the form of the following equation. Expansion (percent) = [[ A + B (?t) + C (?t)2] ?t 104] The constants, A, B, and C, were determined by least square techniques for X-ray camera, X-ray diffractometer, and dilatometer data separately, and for combined data of all five techniques. Expansion values are tabulated from 26° C. to 1,400° C. in 2° C. intervals using constants derived from X-ray camera data. Below approximately 500° C., expansion values obtained by dilatometric and interferometric methods are significantly lower than those by X-ray methods; above 500° C., this bias decreases rapidly. Comparison of results within methods showed the least variance for X-ray camera results; dilatometer and X-ray diffractometer results have about the same variance. The average deviations, in percent, between observed and calculated expansion values among methods were approximately 10 percent from 100°C. to 300°C., 5 percent from 300°C. to 500°C., and 2 percent from 500°C. to 1,400°C. Maximum deviations were approximately twice as large in most instances.

Jan 1, 1962

By A. M. Gaudin

In the first place, let me thank you for inviting me to appear before you today to speak to you on "Mineral Industry Problems - Present and Future". It is a distinguished honor for me to have this opportunity, and I am highly appreciative of this distinction. The beautiful surroundings of Gatlinburg and the pleasantness of a summer occasion are a wonderful tonic for all of us, yet they should not blind us to the seriousness of our Industry's problems No doubt, because of my past appearances before members of the Society of Mining Engineers, at which I discussed wholly scientific topics, or research in the Applied Sciences, you may be expecting me to revert to these subjects. But I intend to venture in a field that is new to me, yet old to all of us, the field of Economics.

Jan 1, 1962

By Robert D. Pehlke, Arden L. Bement

A mass transfer coefficient for the removal of hydrogen from liquid aluminum by inert flush degassing has been determined experimentally at 700°C. A mathematical model has been derived, assuming transport control, which adequately describes the experimental data. The removal of hydrogen is shown to increase with decreasing bubble size, and with increasing flow of flushing gas. The presence of hydrogen in liquid metals in amounts which exceed the solid solubility at one atmosphere hydrogen pressure is highly undesirable, causing unsound ingots or castings, or resulting in difficulties during further fabrication. The removal of hydrogen from liquid metals can be accomplished by several methods, the principal two being vacuum treating and inert flush degassing. The design of a process involving either of these techniques is based on the mass transfer coefficient for hydrogen between the liquid metal and a hydrogen-dilute gas phase. In an effort to extend our knowledge in this area, an investigation of the rate of removal of hydrogen from liquid metals by inert gas flushing was undertaken. In view of the difficulties encountered with gas porosity in the casting of aluminum and aluminum alloys, and because of certain experimental advantages, liquid aluminum was selected for the study. PREVIOUS INVESTIGATIONS The removal of gases from liquid metals, particularly steel, has received considerable attention in recent years, The first definitive work of a theoretical nature was presented by Geller1 who considered the case where equilibrium exists between purging gases and metal bath during flushing, and also deviations from this ideal case. Hulme2 has surveyed a number of experimental studies and discussed some of the practical limitations of removing dissolved gases from molten metals. More recently a number of studies have been reported on degassing of steel melts by flushing with an inert gas.3'4 Considerable work has also been reported on aqueous and organic liquid-gas systems, and an excellent summary prepared by Hovis.5 The treatment of liquid aluminum by a flushing gas to remove dissolved hydrogen has been known for several decades.6 A number of gases have been used for this purpose, including nitrogen, argon, and chlorine, or mixtures of these gases. Tikkanen and Erkko7 have studied the relative density changes of aluminum castings poured from melts degassed with chlorine, nitrogen, and mixtures of the two gases. Their

Jan 1, 1962

By Monte J. Pool, Rudolph Speiser, George R. St. Pierre, William T. Ebihara

Standard free energies of formation of WO,, W O W20058 and WO3from oxygen and the lower oxide or tungsten have been determined in the tempel-ature range of 700° to 1220°C. A tentative W-O phase diagmm is presented based on the evidence that the oxide phases, "W18O49" and "W20058", are unstable at l~atm total pressure, below 585° and 485°C:, respectively. A HE need for a complete quantitative treatment of the phase equilibria of the W-O system has been establishedby metallurgists during the past few years. In an attempt to improve the endurance of tungsten exposed to oxidizing atmospheres at high temperatures, many research groups have studied the kinetics of tungsten oxidation. The reverse process, the reduction of the tungsten oxides to metal, has also been investigated to some extent. Regardless of the particular interest, metal to oxide or oxide to metal, a knowledge of the phase equilibria of the W-O system is required to properly interpret all of the kinetic observations. It should be possible to state the stable phases of the W-O system at any given values of the chemical potential of oxygen and the temperature.

Jan 1, 1962

By R. P. Maloney

Since mining operations began in 1900, Government geologists and mining men have periodically recorded the presence of the minerals of mercury and antimony in the extensive gold placer deposits near Flat in the Iditarod district of the Yukon River region, Alaska. No serious effort was made to recover the cinnabar contained in the gold placer gravels, and there is no evidence that veins of cinnabar and stibnite exposed in the placer operations (as reported by the Geological Survey) were ever explored or developed. A large monzonitic intrusive, which is the dominant geologic feature of the immediate area, is believed to be the lode source of the valuable minerals in the placer deposits. In contact with the monzonite are argillite and quartzite, metamorphic products from the Cretaceous shales and sandstones.

Jan 1, 1962

By David T. Peterson

Calcium metal was found to deoxidize thorizcm at 1000° to 1200° C. The reaction kinetics were determilled and related to the diffusion coefficients of oxygen in thorium. The solubility of oxygen in thorium, the minimum oxygen concentration, and the diffusion coefficient were determined from 1000° to 1200°C. This firocess results in the lowest oxygen concentrations zohich have been reported for thorium metal. FOR many years it has been known that calcium metal will reduce thorium oxide to thorium metal. This reaction has been the basis for several methods of preparing thorium metal. From the equations giv-by Kubaschewski and vans, ' AF" for the reaction Cao, + Tho,(,) - CaO(,, + Th(,) was calculated and found to be -3.4 kcal at 1000°C, -2.5 kcal at llOO°C, and -2.0 kcal at 1200°c. Thorium is very slightly soluble in liquid calcium, and the solubility of calcium in solid thorium is very low. Consequently these metals would be in essentially their reference states. If thorium containing oxygen were equilibrated with liquid calcium between 1000° and 1200°C, the oxygen content of the thorium would have to be below the solubility limit in thorium. Oxygen is one of the impurities most difficult to remove from thorium and is the most abundant impurity in metal prepared by almost all known methods. Fortunately, oxygen does not have a large influence on the properties of thorium because the solubility in solid thorium is very low. EvenT in thorium containing 100 ppm of 0, particles of thorium oxide can be observed in the microstructure. In view of the incompatibility of thorium oxide and liquid calcium and the low solubility of thorium oxide in thorium, the deoxidation of thorium by this method was investigated. For thorium containing an amount of oxygen well in excess of the solubility limit, the reaction should proceed in the following sequence. The oxygen content of the thorium matrix near the surface would be depleted by the diffusion of oxygen to the surface. At the surface, the oxygen would react with calcium to form calcium oxide. To maintain equilibrium within the thorium, thorium oxide would dissolve to keep the matrix saturated. Consequently, the thorium-oxide particles would disappear first at the surface and then the particle-free rim would grow in thickness. If the rate-controlling step were the diffusion of oxygen through this layer of thorium which was growing in thickness in direct proportion to the amount of oxygen removed, the well known parabolic time law should be observed. If the oxygen concentration at the surface of the thorium and at the inner surface of the deoxidized rim were known, the diffusion coefficient of oxygen in thorium could be calculated from the parabolic rate constant. EXPERIMENTAL PROCEDURE The thorium metal used in this study was prepared by calcium reduction of ThF, by the method described by Wilhelm.' The analysis of this metal is given in Table I. The carbon was determined by combustion, the oxygen by the HC1-insoluble residue method, nitrogen by the Kjeldahl method, and the other elements by emission spectroscopy. A section of this ingot was hot rolled at 600°C to 1/4 and 1/8-in. thick plates. Specimens approximately 7/8 in. square were cut from these plates, and all surfaces of the specimens were cleaned and smoothed by filing with a clean file. Individual specimens were placed in 1-in. diam by 2-in.-long tantalum capsules. Approximately 1 g of clean, high-purity calcium was placed in the capsules and an end closure arc-welded in place. The tantalum capsules were sealed in Inconel crucibles to protect the reactive metals from oxidation. The entire loading procedure was done in a glove box filled with pure argon. The loaded crucibles were placed in a muffle furnace, controlled within 2OC of the desired temperature, for a measured length of time. After the specimen had cooled to room temperature, it was sectioned perpendicular to the large faces and through the mid-point of two of the sides. The sectioned specimen was mounted and polished through Linde A abrasive. The rim which was free of thorium-oxide particles could be clearly observed microscopically as mechanically polished. Twenty measurements of the thickness of the rim were made at equally spaced points far enough from the end of the

Jan 1, 1962

By D. F. Walsh

A study of damping capacity was made on a number of magnesium-base alloys, commercial types and experimental compositions. Hardness and tensile properties were determined, and the microstructure of each alloy was examined. Alloys of low yield strength, in general, possessed high damping ability. A correlation was established between damping capacity and composition.

Jan 1, 1962

By A. W. Storm

Vertical shaft furnace design and operation have their roots deep in antiquity. There is substantial evidence to indicate that iron was reduced from its oxides to serve mankind's needs long before recorded civilization - - actually prior to 3500 B .C. For at least 5500 years man has been matching wits with Nature to find better methods of extracting this most common, yet essential, metal from her, grasp. And, during nearly all of this period, the vertical shaft furnace has played a principle role in this dramatic struggle.

Jan 1, 1962

By D. W. Scott

Thermodynamics is a powerful tool for investigating rotational isomerism in substituted ethanes and related molecules. Accurate calorimetric data can be interpreted to give information, not only about the energy difference between conformations, but also about the shape of the potential barrier hindering rotation from one conformation to another. However, a deterrent to this use of thermodynamics is the labor required to calculate the contributions to the thermodynamic functions for assumed potential functions. Tables of thermo-dynamic contributions for appropriate potential functions can eliminate that labor and greatly facilitate the thermodynamic study of rotational isomerism. In this research, tables of contributions to the thermodynamic functions were compiled for two potential functions typical of some commonly encountered examples of rotational isomerism. TYPES OF POTENTIAL FUNCTIONS Potential function 1, illustrated in figure 1, A, has two equal minima higher than the third. It has the general shape of the barrier to internal rotation in n-butane, for example. The trans conformation of n-butane has the lowest energy, and the two skew or gauche conformations have equal but higher energy. Potential function2, illustrated in figure 1, B, has two equal minima lower than the third. It has the general shape of the barrier in 2-methylbutane, for example. The two C1 conformations of 2-methylbutane have equal energy much lower than the assumed Cs conformation, which has not been observed spectroscopically.

Jan 1, 1962

By Kevin Malone

Mercury, or quicksilver as it is often called, has many applications in modern technology. Used principally in electrical apparatus, industrial contol instruments, insecticides and fungicides, electrolytic preparation of chlorine and caustic soda, chemical processes, pharmaceuticals, and dental preparations, the liquid metal has unusual properties that make it a preferred material for many industrial uses. United States consumption of mercury during the past 40 years shows a rising trend. In all except 4 years, U.S. production has been less than the domestic requirement, and imports, principally from Spain, Italy, and Mexico, have supplied most of the deficit. After World War II, domestic output decreased rapidly until 1950, when it was the lowest in the 100 years covered by production records. Higher mercury prices since 1950 have reversed the decline in domestic output and reduced the gap between U.S. production and consumption. Domestic output in 1958 was the highest in peacetime since 1883; however, the nation still imported 28 percent of its mercury requirements from 1950 to 1960 the price of mercury was high as a result of industrial applications of the mercury cell, the impact of the cold war and the Korean war, and the Government stockpiling program. The stockpiling program, in effect, put a floor under mercury prices even though only 9,428 flasks of domestic mercury went into the stockpile under the original program which ran from July 1954 to December 31, 1957. Under an extension of the program, an additional 17,463 flasks was purchased.

Jan 1, 1962

By C. Hays, R. E. Swift, E. G. Kendall

Investigations of the Zr-Pt system, by metallography, incipient melting, and X-ray diffraction, determined the phase relationshifis from 0 to 50 at. pct Pt. Phase fields in the Pt-~ich region were outlined, and three intermetallics (ZrPt, Zr2Pt, and ZrPtd were located. A eutectic between Zr and Zr2Pt, and a eutectoid veaction between Zr and a Zr + Zr2Pt, were established. The maximum solubility of Pt in P Zr was approximately 13.5 wt pct, as opposed to less than 1 wt pct solubility in a Zr. EARLIER work on the Zr-Pt system was limited to an X-ray study on the intermetallic compound, ZrPt3, by H. J. Wallbaum,1 It was reported that ZrPt3 existed at 86.52 wt pct Pt, and had a hexagonal structure, isomorphous with TiNi3. Wallbaum's data revealed the following structural particulars: a = 5.633A, c = 9.21A, and c/a = 1.635A. Other studies allied to Zr-Pt alloys concerned only 1) Pt-rich alloys (0.05 to 5.0 pct Zr) for corrosion resistance,2 2) a Zr-base alloy with 5 pct Pt and 0.124 pct C for oxidation resistance,3 and 3) electroclad-ding of Zr with Pt for in-pile corrosion resistance of Zr to uranyl sulphate. 4 Metallographic, incipient melting, and X-ray diffraction techniques were applied to accurately resolve the phase relationships in the 0 to 50 at. pct (68.2 wt pct) Pt region, and to outline the phase fields in the Pt-rich area. Three intermediate phases: Zr2Pt, ZrPt, and ZrPt3, were also established by the same methods. PROCEDURE Melting stock for this program was of the highest purity obtainable. The Zr was iodide crystal bar with a low hafnium content of about 0.05 wt pct (Westinghouse "Grade 3"). The as-received Zr was treated to remove the surface film of corrosion product that resulted from a standard autoclave grade designation test. Next, the bars were processed to yield material suitable for arc melting and free of contaminants. Sheet platinum metal (Baker and Co. "Grade 2") was used for alloying additions. This material con-

Jan 1, 1962

By L. Zwell, H. A. Wriedt

X-ray Lattice parameter and bulk density measurements were made at room temperature on solid solutions of nitrogen in purified a, iron, containing from 0 to 0.053 wt pct N. When nitrogen is dissolved in a, iron, the fractional increase in unit cell volume (X-ray diffraction) and the fractional increase in volume per gram of iron (bulk density measurement) are the same within experimental error. The two sets of results when averaged show that the unit cell edge of a, iron increases linearly by 3.2 X 10-2 A per wt pct N dissolved and that the partial gram-atomic volume of nitrogen at infinite dilution in a, iron is the same as it is in nitrogen-martensite, that is, 5.90 cm3. RECENT reviews17' of literature dealing with the lattice parameter of ferritic iron-nitrogen alloys indicate that the dilating effect of dissolved nitrogen on the bcc unit cell of a iron is not known with confidence. Five investigations3-7 either revealed no effect of nitrogen or were inconclusive. Among other investigations, where quantitative data were obtained, the results of Osawa and Iwaizumi8 indicate too large an effect, and those of Eisenhut and Kaupp9 show the lattice parameter of ferrite varying with the nitrogen content at concentrations far beyond the known solubility limit. It is not clear in Burns'10 data what value should be used for the lattice parameter of nitrogen-free ferrite in calculating the dilation. Burdese11 shares with Burns the shortcoming that the iron-nitrogen alloys were solution-treated and quenched with undissolved nitride present. The consequence is that the un- certainties in the solubility limit1 are added to those in the lattice parameter measurements when the variation of lattice parameter with nitrogen content is computed. For a system of such widespread interest, we felt that a new investigation was merited. Both X-ray diffraction and bulk density measurements were used to determine the dilation of the , a iron lattice by dissolved nitrogen. EXPERIMENTAL PROCEDURE Material. The bulk density and X-ray diffraction experiments were both made with specimens of a purified iron (denoted as "B iron")- from Battelle Memorial Institute. The impurity contents were as follows: As, C, Cu and Pb—50 ppm; Ag, Al, Co, Ga, 0, Ti-11 to 50 ppm; B, Be, Ca, Cd, Cr, Mg, Mn, Mo, N, Ni, S, Sb, Si, Sn, V, W-10 ppm or less. The vacuum-cast ingot was hot-forged and annealed. Pieces of the forged stock were machined and cold-rolled to give strip stock 0.08 and 0.002 in. thick for density and for X-ray measurements, respectively. Preparation of Specimens. Starting with a piece of the cold-rolled iron stock, the general sequence of operations, after an initial recrystallizing anneal, was to measure the density or lattice parameter, nitrogenize, remeasure the property, age or denitrogenize, and again measure the property. Duplicate analyses for nitrogen were made by a modified Kjeldahl method on portions of the actual density specimens and on pieces nitrogenized to equilibrium alongside the X-ray specimens. Annealing of the density specimens was performed by sealing the pieces with the as-rolled surfaces removed by filing into evacuated "Vycor" capsules and treating for 1 hr at 750°C followed by furnace cooling. (TO check the effect, if any, of annealing procedure, a specimen also was

Jan 1, 1962

By R. Ward Stahl

Fire is still a scourge of the mining industry, although many precautionary measures have been and are being taken to reduce the incidence of fires and to combat them. Generally, the success of fire extinguishment is directly proportional to the speed of attack, and the speed of attack in turn is dependent upon the availability of materials and trained personnel. Preparations for firefighting are frequently neglected because they are considered emergency needs and do not contribute directly to coal production. Fire incites panic--a fact often overlooked--but such chaos can be minimized by training people in the use of equipment and procedures. Heat, smoke, and fumes hamper the approach to a fire; however, a relatively new technique of attacking fires with high-expansion foam may well contribute greatly to firefighting. The foam is transported to a fire and used at a considerable distance, thus permitting the firefighters to work more safely.

Jan 1, 1962

By P. E. Doherty, R. S. Davis

Sub boundaries and micropores, as well as certain other imperfections, may be revealed in aluminum by the formation of pits on the surface during cooling from elevated temperatures. The pits are attributed to the condensation of vacancies from supersaturated solution. This "vacancy pit" phenomenon has been used as an etching technique for studying the structure of aluminum specimens grown from the melt. Three fundamental structures were studied: stria-tions, cells, and dendrites. Two types of striations, as well as a crosswise structure are reported. Mic-roporosity is observed to occur in the cell walls on freezing. Subboundaries between primary, secondary, and tertiary branches are observed in dendritic growth. A special case is cited in which cellular growth suppresses the formation of striations. SMALL, well-defined pits have been observed to form on the surfaces of electropolished aluminum specimens during cooling from elevated temperatures.' This phenomenon was attributed to the condensation, from supersaturated solution, of vacancies at particular points on the surface. It was shown that the amount of cooling required for the formation of pits increased exponentially with decreasing holding temperatures in a way that was consistent with the thesis that a critical supersaturation of vacancies was required for the pits to form. Pits do not form in the vicinity of certain imperfections, namely, subgrain or normal graind boundaries, phase boundaries, certain surface irregularities, and pores. The width of the pit-free region increases with decreasing cooling rate. This observation suggests that the imperfections in question are effective sinks for vacancies and that the pit-free region around them is material that is not sufficiently supersaturated with respect to vacancies to nucleate the surface pits during cooling.

Jan 1, 1962

By James Westfield

Following is a brief history of Bureau of Mines Division of Coal-Mine Inspection activities that have favorably effected health and safety and reduced Injuries at coal mines: The Federal cline Safety Code for Bituminous Coal and Lignite Mines of the United States was issued originally by the Director of the Bureau of Mines on July 24, 1946, after consulting with management and labor representatives of the coal-mining industry. The code has been used by Federal coal-mine inspectors while inspecting bituminous-coal and lignite mines for the existence of unhealthful and unsafe conditions and practices in these mines. A revised code was issued by the Secretary of the Interior on October 8, 1953, after further consulting with representatives of management and mine workers, and was incorporated in the 1952 and subsequent bituminous-coal wage agreements. The agreement of May 29, 1946, betweeen the Secretary of the Interior, acting as Coal Mines Administrator under authority of Executive Order 9728, and the United Mine Workers of America, covering bituminous-coal and lignite mines in Government possession, charged Federal coal-mine inspectors with the responsibility of making periodic investigations of the mines and reporting to the Coal Mines Administrator any violations of the Federal Mine Safety Code. Federal coal-mine inspectors also had temporary authority to close mines considered imminently dangerous, but authority under Executive Order 9728 was removed on June 30, 1947, when Government control of the mines was terminated.

Jan 1, 1962

By H. Marquis

The present paper consists of a survey of the literature on the problems of abrasion and wear of metals and materials by suspended matter. This problem is a very general one in industry, and is especially notice-able in the operation of cyclones and other types of dust collectors. The problem of abrasive dust in corrosive gas environments, such as commonly encountered in metallurgical industries, is particularly severe. Very little work has been done in the study of this type of abrasive wear, especially at high temperatures. However, a general review is presented here of all the work published on related subjects, such as that involving sand erosion in turbines and water wheels and the effect of temperature on friction wear. Topics in this paper include: blasting wear by sand, quartz, limestone, silicon carbide and other refractory particles; methods of investigation; effects of velocity, temperature and *Canadian Armament Research and Development Establishment, Valcarter, P.Q. angle of attack; correlation between indentation hardness, scratch hard-ness and resistance to abrasion; the effect of protective coatings; resistance of various metals; etc.

Jan 1, 1962

By F. L. Jackson

The large scale transportation and storage of sulphur in the liquid state is a relatively new development, but is really only a logical extension of old mining and processing techniques, It is not known who the first person was to win a relatively pure sulphur from ore by melting, but this method was commercially used at least two hundred years ago in Sicily and is still in use today. The Frasch process of mining was invented over sixty years ago, and the development and improvement of-liquid sulphur pumping and handling techniques has paralleled the growth in the Frasch mining industry. During the last fifty years, improvements in the technology of using sulphur have included the premelting of sulphur prior to its being burned for acid production or conversion into CS2 and other compounds. Yet, until fairly recent times, sulphur produced as liquid has been solidified into large blocks at the producing point, broken down by blasting or with mechanical equipment, and shipped in bulk form as a solid.

Jan 1, 1962