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By Donald H. McLaughlin

MINERAL industry activities have not been seriously hampered by a lack of men with higher training. The balance between opportunities for employment and advancement and available personnel has been a happy one, with enough competition to stimulate effort but not the unfortunate conditions arising from an overabundance. of employment seekers. Nearly all mineral industry educational institutions have been concerned about the falling enrollment in mining and metallurgical courses of study during the past decade. But industry has drawn upon a supply of many types of technically trained men apart from those who prepared their careers specifically in the mineral industry. Some schools have made this possible by uniting geologists, mineralogists, and others with students in mining and engineering. On the other hand, some schools have combined their department of mining engineering with an over-all engineering department and continue to send their graduates into the mineral industry by another route. On the whole, this seems to be a good trend and is likely to result in men better trained for current problems than would have been possible under the older rigid curricula.

Jan 1, 1947

By H. J. Fraser

LIKE a runner catching his second wind, the mining geologist in 1944 has had some opportunity to appraise the result of three years of active and intense search for the metallic sinews of war and peace. The war period has been one of physical activity and accumulation of new data but has not so far resulted in the announcement of any profound or revolutionary theoretical concepts or techniques. Most technical publications during the year have been either descriptive or statistical. A review of accomplishments during the war years, although affording some measure of satisfaction in individual cases or regarding production of certain metals or' ores, is far from justifying any feeling of complacency regarding the growth of the profession either in fundamental knowledge or in application. During 1944 an abundant supply of all metals and minerals flowed steadily to smelters and fabricating plants. Also, during this and preceding years, adequate stock piles for war needs, in view of the improved foreign and domestic supply situation, were accumulated in many metals in such quantities that the mining industry has become concerned not with the problem of supply but with the effect these accumulated stocks, if maintained, might have on the postwar market. These considerations culminated in the enactment by Congress of the Surplus Disposal Act, which, admittedly a tempo-

Jan 1, 1945

By A. Blake Caldwell

Tyrone-a complete mining and concentrating facility built by Phelps Dodge Corp.-straddles the Continental Divide where surface water on either side flows in opposite directions although all water is taken from and returned on the northwest side of the Divide. At the outset, Tyrone was saddled with a problem of an adequate water supply, and the Gila River some 23 miles distant appeared to be the logical source. This in itself presented a major obstacle to Phelps Dodge because of the distance water had to be pumped and because of an adverse head which had to be overcome between the Gila River and the two 4-million-gal-capacity terminal water supply tanks at the mill. Having acquired water rights on the Gila River and in order to control the seasonal fluctuations in water volume, the company built the Bill Evans, off stream, earth-filled dam. This reservoir will contain 2100 acre-ft of water when full and it was constructed by the Hamilton Construction Co. for Phelps Dodge. The dam impounds fresh water for the Tyrone plant's use and four vertical turbine pumps (4500 gpm each) lift the water 275 ft from the Gila River into the reservoir. Since construction, Phelps Dodge has optioned the lake to the New Mexico State Game Commission for recreational purposes. In addition to the lake, land around the reservoir has been optioned to the State Game Commission for public use. The lake has already been stocked with trout and by next summer some keepers should be available for the taking.

Jan 12, 1969

By Clyde Williams

IN this war as in no former one, the use of metals has been the major factor governing success. For building new plants, new transport facilities whether by land, sea, or air, for our mechanized army, and for nearly all weapons, iron and steel has provided the basic material. Being the world leader in iron and steel production in peacetime, we soon adapted plants to production for war. Starting with a production of 66,000,000 tons of steel ingots in 1940 from a rated capacity of 80,000,000 tons which only could be reached by straining every productive device available, our industry expanded to 86,000,000 tons in 1942, and ultimately to 96,000,000 tons. To do so required expansion of every unit operation including mining, rail and water transportation, blast-furnace and steelmaking facilities, and rolling mills. New plants not only had to be built in record time but more output for each operation was essential. This performance required skillful operation and engineering techniques and also a better understanding of the physics and chemistry underlying such complex operations as the working of a big blast furnace. A vastly increased pig iron production made possible the great output of steel by an industry that had depended on scrap for its basic raw material even though sufficient scrap was unavailable. This was done by conversion of pig iron in the Bessemer either into steel or into a low-carbon product that was subsequently used in place of scrap in the open¬hearth steel furnace. Furthermore, by duplexing from the open-hearth to the electric furnace, and the construction of many new electric furnaces, our output of electric-furnace alloy steel was greatly increased. Moreover, techniques were developed by which alloy steel could be made in the open hearth with the result that our production of alloy steel reached the fantastic figure of 15,000,000 tons a year.

Jan 1, 1945

By H. J. C. MAC DONALD

THE mining engineer must have a chest of books snug enough for a camelback or to be stowed away in a canoe; at the lowest possible cost, as he needs it the most in those early years when he earns the least; but at the same time one having an unusually wide range, for he may have to cut down a forest, put up a sawmill, build mine towns, construct dams, power houses, power lines, and railroads. In fact he may be called upon for many unexpected accomplishments and all in extension of the characteristically broad demands of his profession. Suppose that an average mining engineer with a thorough theoretical training and a specialized mining education has accumulated, during a cosmopolitan experience, a complete and up-to-date library, but, unfortunately, in accepting a long term assignment to a far country he is forced to discard the greater part of

Jan 1, 1925

By T. A. Rickard

Technology has no recognized rank in what is called polite literature; the subject-matter of engineering is not supposed to lend itself to artistic treatment; we are the hewers of wood and drawers of water to the high-priests of learning that live on the cold summit above our humbler dwellings. Therefore the hierophants smile at the notion of 'style1-" that curiously personal thingy-in technical writing. The "great art" of Pater, the "inevitable phrase" of Raleigh, the "note of distinction" that Arnold demanded are said to be beyond the scope, as they are supposed to be beside the need, of a writer on geology or engineering. This is a narrow view. Science, no less than belles lettres, calls for the best exercise of the human intelligence; the art of writing should be employed as skilfully and as earnestly in a description of the structure of the Sierra Nevada, or of the construction of a tunnel through the range, as in a rhapsody welcoming the rosy fingers of the dawn. The idea still lingers that fine writing does not befit technology, even though the masters of the Victorian period-Huxley, Tyndall, Ruskin-proved that science is worthy to be arrayed in the best robes that the looms of thought can weave. At the beginning of these lectures I quoted Barrie's remark touching the inability of the scientific man to express himself. That imputation has been passed to the technologist, whose utilitarian pursuits are supposed to make him too clumsy for the refinements of human speech. We may not have acquired the self-consciousness of those writers on Art whose "power of expression is so cultivated that their sensual caterwauling may be almost mistaken for the music of the spheres"; nor can we imitate the politicians, who have the ability to speak far beyond anything that they may have to say; but we too have a litera-

Jan 1, 1931

By M. B. Kahle, A. D. Pernichele

Four types of slope failures in waste dumps are recognized debris flow, foundation failure, edge slump, and blowout. The first three types, although at times causing considerable damage to property and interfering with mine operations, are not usually dangerous to personnel because of their slow rate of movement. The fourth type, the blowout, is the most dangerous because of its explosive mode of failure and lack of forewarning. The December 1969 failure at Verona dump is presented as an example of a blowout. Data from piezometer holes indicate that the blowout was due to perched leach solutions near the face of the dump. The level of water in this zone is very closely related to the rate of leach water application on the dump. A detailed analysis of core samples indicates that the impounded water was perched on a zonal accumulation of jarosite which is associated with a buried dump surface. Drain holes proved successful in controlling perched leach solutions in the critical zone near the face of the dump. Monitoring of the water level in the perched zone is considered essential in preventing blowouts. The use of drain and piezometer holes has allowed an increase in the rate of water application on the dump while preventing additional failure.

Jan 1, 1972

By James K. Gluck, William E. Galloway, Gary E. Smith, John P. Morton, Christopher D. Henry

INTRODUCTION Surface mining and in situ leaching of uranium have the potential to alter ground-water quality around mines and leach sites. Of particular concern is the fate of uranium and its associated trace elements: molybdenum, arsenic, and selenium. We wish to under- stand the natural processes that control trace element concentrations in ground water and how these processes will influence dispersion of the elements from a mineralized zone, both naturally and during and after mining or restoration. For example, it is commonly recognized that the trace elements are soluble in oxidizing ground water but are insoluble, and can be precipitated, in reducing ground water. Thus oxidizing, metal-bearing water leaving a deposit could re- enter reduced ground, causing the water to be re- reduced and the trace elements to be, reprecipitated. In a sense, this is recreating the original mineralization process. To accomplish the above goals, we have (1) examined the theoretical controls of concentrations based on the available geochemical and thermodynamic data, (2) determined the major ion composition and oxidation-reduction status of Oakville waters because of the influence of these factors on trace element solubility, and (3) determined trace element concentrations and distribution in Oakville ground water. The last approach is used to evaluate how well actual behavior follows predicted behavior. This report focuses on two elements, uranium and molybdenum, because they exemplify the results obtained. The report also is restricted to a regional study of Oakville ground water. Results of more de- tailed study in and around major uranium districts in the Oakville and much of the raw data that support the conclusions in this report are presented in Galloway, Henry and Smith (1980). This report is part of that larger study, which concerned the depositional systems, hydrology, and geochemistry of the Oakville. The U.S. Environmental Protection Agency funded the study, under grant numbers R-805357-01 and R-805357-02. Theoretical controls were determined by reviewing the available literature on aqueous chemistry and behavior of uranium and molybdenum. To aid in under- standing water chemistry, Oakville water analyses were run through a modified version of the computer model WATEQF (Plumer, Jones, and Truesdell, 1976). WATEQF calculates speciation of dissolved ions and determines saturation with respect to a variety of minerals. In the discussion below, ion activity products (IAP) are compared with the equilibrium constant (KT) for various reactions and mineral products. Values of log IAP/KT near zero indicate that the water is in equilibrium with a mineral. Values less than -1 indicate considerable undersaturation and values greater than +1 indicate oversaturation. Galloway, Henry, and Smith (1980) give a more complete discussion of the application of this approach to Oakville water chemistry. Eh-pH diagrams have been constructed or adapted from the literature to predict what form -- dissolved ion or stable mineral species -- uranium and molybdenum assume under various conditions. Construction of the diagrams has followed procedures described by Garrels and Christ (1965). This approach is particularly appropriate because the solubility of the elements is Eh-dependent, and Eh varies greatly within the Oakville aquifer. A number of assumptions or approximations are inherent in the use of Eh-pH diagrams and chemical models such as WATEQF and in the interpretation of water chemistry in general. Both Eh-pH diagrams and chemical modeling rely entirely upon available thermo- dynamic data, including free energies of formation and dissociation constants for various reactions. These values are known to varying degrees of accuracy. Most major ions and minerals are relatively well control- led; however, data for trace metals are much poorer. Thermodynamic data are not available for some minerals, and for other minerals, two or more divergent values exist. By necessity, we have relied on the judgment of others to evaluate thermodynamic data. Calculations by WATEQF and constructions of Eh-pH diagrams are based on an assumption of equi1ibrium. Equilibrium may not be comnon in low-temperature aqueous environments; at best, ground-water composi tion may be in a state of dynamic equilibrium, continuously changing due to changes in environmental conditions. Eh-pH diagrams show what phases are stable at equilibrium under given conditions; they do not prove that the phases actually exist. Many minerals persist or form metastably under conditions outside their equilibrium stability field. The kinetics of reactions, which cannot be evaluated here, are important in determining what phases occur. Kinetics may be less of a problem for ground water that travels and evolves slowly through a semihomogeneous matrix than for many other natural systems. Eh-pH diagrams show equilibrium fields only of phases included. They do not indicate anything about stability relative to phases not included in the diagram. WATEQF, obviously, cannot calculate the degree of saturation of a mineral not included in the program or for which the appropriate ions were not analyzed. Thus, a mineral that was not considered may be the most stable phase under a given set of conditions and may control the solubility of a trace element. Also, this study is limited exclusively to in- organic compounds. Organic material is known to be an

Jan 1, 1980

By J. W. Spretnak, J. N. Cordea

The gain boundary relaxation in high-purity aluminum, nickel, copper, and silver was studied by means of a low-frequency torsion pendulum. Both internal friction and creep at constant stress tests were conducted. A lognormal distribution in relaxation times was found to account for the relatively wide experimental internal friction peaks and the gradual relaxation behavior during the creep tests. This distribution was separated further into a lognormal distribution of relaxation time constants and a normal distribution in activation energies. A spread of up to ±6 kcal per mole in the activation energies accounted for the major part of the distribution. A "double-peak" internal friction phenomenon was observed in silver. The activation energies in kcal per mole derived from the grain boundary relaxation phenomena are 34.5 for aluminum, 73.5 for nickel, 31.5 for copper, and 41.5 for silver. It was found that the rain boundary relaxation strength in these metals increases with the reported stacking-fault energy. GRAIN boundary relaxation phenomena have been observed in a large number of polycrystalline metals and alloys. Numerous investigations have been conducted to study the structure of the grain boundary through this relaxation process. One of the first investigators was Ke1-4 who observed that the activation energy for grain boundary relaxation in aluminum, a brass, and a iron was about the same as that for volume diffusion. He concluded that the grain boundary behaved as if it were a thin liquid layer with neighboring grains sliding over one another. Leak5 conducted experiments on iron of a higher purity and observed that the grain boundary activation energy is comparable with that of grain boundary diffusion. He suggested that, in metals where this relationship holds, the damping may be caused by a reversible migration of grain boundaries into adjoining grains. Nowick6 has presented an interesting view of inter-facial relaxation with his "sphere of relaxation" model. A relaxed interface is represented as one where the shear stress is greater than the normal value along the edges and zero in the interior of the interface. The region of the stress relaxation is pictured as a sphere surrounding the interface. From his calculations Nowick concluded that the slip along an interface is directly proportional to its length. Therefore, the time of relaxation, T, depends on the size of the relaxation interface. This means that in the Arrhenius relationship, t = TO exp[H/RT], valid for atom movements, the relaxation time T is predicted to be proportional to the grain diameter through the pre-exponential term, TO. Since the internal friction can be given as Q-1 = ?j wt/(1 + w2r2), where ?J is the relaxation strength and w is the angular frequency, an increase in grain size at a constant frequency will shift the peak to a higher temperature. A great deal of work has been done to determine the exact relationship between the internal friction and grain size.1,5,7,8 In metals, the grain boundary peaks are found to be lower and broader than predicted theoretically.' The above model can explain this by a distribution in the size of the interface areas, represented by a distribution in the parameter tO, and an overlap of spheres of relaxation, represented by a distribution in activation energies. Both these phenomena result in an over-all distribution in the relaxation time, which could affect the internal friction peak height, breadth, and also position. This relationship between the experimental data and theoretical calculations appears very promising in the study of interfacial relaxation mechanisms. THEORY A lognormal distribution in t can sometimes be used to adequately describe the spectrum of relaxation times governing an anelastic relaxation. wiechert9 originally suggested such a distribution to explain the elastic after-effect in solids. This choice is particularly applicable to grain boundary relaxation when considering Saltykov's work.'' He found a lognormal distribution in the grain sizes within a metal. Recently Nowick and Berry11 have introduced a log-normal distribution in T into the theoretical internal friction equations. The form of the distribution function is where z = In(r/rm), and Tm is the mean value of t. The parameter ß is a measure of the distribution and is the half-width of the distribution when is l/e of its maximum, IC/(O). Nowick and Berry have described the methods to obtain the parameters Tm, ß, and ?,J from experimental internal friction and creep test data. In the idealized case, where only one relaxation event occurs with one relaxation time, only ?J and T are necessary to completely describe the event, and 0 = 0. For the broader internal friction curves 6 is some positive number greater than zero. The larger the 6, the greater is the half-width of the distribution in In t.

Jan 1, 1967

By John Henderson

Densities of melts 0f the lime-iron oxide-silica system in contact with solid iron have been measured by the maximum bubble pressure method in the temperature range 1250° to 1440°C and the composition range 0 to 40 mol pct lime, 15 to 100 mol pct iron oxide, and 0 to 55 mol pct silica. Densities range from 4.65 g cm 3 for wustite at 1440°C to 2.75 g cm-&apos; at 1350°C for a melt containing 30 mol pct lime, 20 mol pct iron oxide, and 50 mol pct silica. The results are interpreted in terms of a postulate that the melts can be regarded as a random array of oxygen ions in which regions of local order exist to satisfy the coordination requirements 0.f the cations. An understanding of the nature of metallurgical slags is basic to the development of a sound theoretical description of heavy metallurgical extractive and refining processes. Because these liquids are complex, direct measurements of their properties has not thrown much light on their structure. This has led to the approach of measuring the properties of simpler liquids, and building up their complexity until slag compositions are reached. In this way the density of liquid iron silicates was measured in a previous study1 and the present work represents a further stage in this synthesis. EXPERIMENTAL The technique used in the measurement of density was the maximum bubble pressure method. Details of the apparatus and procedure were similar to those previously reported,&apos; with the exception that a constant voltage transformer was used to supply the power input to the furnace and six silicon carbide resistance elements were used in place of the molybdenum winding. With these modifications melt temperature could be maintained within 1 centigrade degree during the course of a run. The silica used to prepare the melts was washed natural quartz ignited at 1000°C; wustite was prepared by air-melting A.R. grade ferric oxide in an iron crucible and lime was prepared by air ignition, at 1000°C, of weighed quantities of A.R. grade calcium carbonate, previously air-dried at 110°C. The finely ground constituents were intimately mixed in a glass ball mill prior to melting. Temperatures quoted are accurate to * 5°C and the standard deviation of the density values, calculated by the method of least squares, ranged from 0.5 to 1.8 pet. However, replicate determinations of density on different melts of the same nominal composition at the same nominal temperature did not vary by more than 1 pct, Table I, and this figure has been taken as an estimate of the accuracy of the density results. The density of carbon tetra-chloride was also measured as a check on the absolute performance of the experimental method. At 20°C a value of 1.593 * 0.002 g cm"3 was obtained; this compares with the literature value2 of 1.595 g cm"3. Results of experiments designed to measure the dependence of the density of lime-iron oxide-silica melts, in contact with solid iron, on composition and temperature are shown in Table I. Because iron sometimes precipitated in the sample during quenching, the Fe203 chemical analyses were only poorly reproducible and should be taken as a guide rather than as absolute values. Fig. 1 shows the data from various sources for the density of liquid iron silicates and Fig. 2 shows isodensity contours at 1410°C for lime-iron oxide-silica melts, calculated by graphical interpolation of smoothed curves drawn through the experimental results, together with the 1400°C results of Adachi and ogino3 and Pope1 and Esin.4 Fig. 3 shows the isothermal variation with composition of the volume of melt per gram ion of oxygen at 1410°C and Fig. 4 shows regions in which the temperature coefficient of this volume is negative, positive, or negligible (<0.005 cm3 deg-I). DISCUSSION a) Disparity Between Reported Density Results. Consider the system iron oxide-silica, the results for which are summarized in Fig. 1. Although there is some difference in the temperatures at which the various densities apply, this difference is not sufficiently large to account for the observed discrepancies. The reliability of the present results for the low-silica region has been confirmed by measurement of the density of liquid wustite by three different techniques. At 1410°C the density measured by a balanced-column method was 4.55 g cm"3, by a combination balanced-column and gas-densitometer method 4.59 g emd3, and by a pycnometer method 4.53 g cm"3. Schenck, Frohberg, and Hoffermann&apos; have also reported a value of 4.55 g cm"3 for the density of liquid wustite at 1400°C. It must be concluded, therefore, that neither Pope1

Jan 1, 1964

By J. R. O’Connor

Stimulated emission from Nd+3 in yttrium uanadate fYVOJ is reported. Single crystals of YVO4:Nd, obtained from Linde Col-p., have improved substantially in the last several months. Pulsed thresholds of YVO, laser rods are now approximately 2 to 3 5, cowparable to tliose for YAG:Nd. Yttrium uanadate crystalli~es irz a space group similar to zircon. All rare-earth vanadates have this structure. Rare-earth ions sucll as Nd+3 which substitutes for Y+3, aye situated irz a strong tetragonal crystal field which lacks inversion symmetry. This condition increases the p&apos;robability of the parity-forbidden f — f transitions. Yttrium anadate has strong absorption bands beyond -1000A. These are clue to Y-O, V-O charge transfer and molecular transitions. Under 2537 and 3660A irradiation pure YVO, fluroresces u bright yel-LOLO. This fli&orescence is corrzpletely quenched in YV04:Ncl crystals. This and other evidence of energy trut~sjer from the lattice is repovted. Optzcul atz 1user pvope 1-ties o! YI&apos;U4:E[t are brieJy described. THIS paper describes some of the optical and laser properties of Nd+3- and Eu+3-doped yttrium orthovana-date (YVO4). It reports laser action for the first time in this low-symmetry host. For some time we have pursued a research program concerning laser hosts&apos; wherein the rare-earth (RE) ion is situated at a site of low crystal symmetry so as to increase the probability of radiative transitions. Single crystals of doped and undoped YV04 are grown from iridium crucibles in an oxyhydrogen gas-fired furnace by a modified Czochralski technique.&apos; This material crystallizes in a D4li tetragonal space group of the zircon (ZrSiO,) type.3 All RE vanadates have the same structure and form solid solutions with YVO4. Therefore, it will be possible to investigate a variety of cross-pumped laser systems, as in the case of yttrium aluminum garnet (YAG).4 At present, ~d&apos;~-doped YAG is one of the most efficient solid-state lasers.5 Accordingly, most of the material to follow will compare the properties of YV04 to those of YAG. Fig. 1 shows the relative transmission of YAG and two types of YVO4. "Pure" YVO4 has a normal absorption edge and is colorless. A second type has a broad absorption peaking near 4200A and is yellow. Rubin and Van uitert6 suggest the yellow material is slightly reduced. Samples of each type are being investigated by electron spin resonance,7 but these studies are so far inconclusive. The pulsed laser threshold is much lower in the yellow material than in the colorless. Therefore, the absorption at 3500 to 5000.4 transfers energy to the Ndi3 ions. Photons of wave length between 2000 and 4500A cause undoped YVO4 to fluoresce at 4800, 5250, 5460, 5540, and 5750A. This emission, previously reported by Brixner and Abramsom,8 is partially quenched by EU&apos;~ and completely quenched by Ndt3 at room temperature due to energy transfer from the lattice to the RE ions. At low temperatures, some lattice fluorescence is present. This implies that the energy-transfer process is in part phonon-assisted. Although the YVO, single crystals used in this work were prepared from Y2O3 containing less than 0.01 pct rare-earth impurities, there is aopossibility that emission lines between 4800 and 5750A are due to dysprosium, terbium, and so forth. However, these lines are not observed in other compounds, prepared from Y2O3, such as YP04, Y2MoO6, and so forth. Furthermore, extensive absorption measurements on our "pure" YV04 single crystals between 0.4 and 5.0 failed to reveal any characteristic rare-earth lines. Fig. 2 compares the absorption spectra of Ndt3-doped YAG and YVO4from 0.6 to 1.0 . The Ndt3 absorptions are labeled according to free ion, R-S coupling. These term designationsQ are appropriate for YAG:Nd. They appear to be inappropriate for YV04:Nd. In YVO, neodymium must substitute for yttrium. The yttrium site is situated In a strong tetragonal field, where point symmetry is (42m) or possibly lower.1° However, the reduced splitting of the Stark components of the YV0,:Nd spectrum implies that the NdT3 ion is in a cubic site. The only plausible explanation for this discrepancy is that the Ndt3 ion is in a low-symmetry site, lacking inversion symmetry, so that a substantial admixture of 4f and 5d wave functions occurs. In this case, R-S coupling is not valid and J is no longer a good quantum number." Consistent with this view, the 4~ metastable level of YV04:Nd has an oscillator strength larger and a

Jan 1, 1968

By N. W. Lord

The process of molten-zone refining is analyzed for long ingots and many zone passages. Formulas are derived which give the resultant impurity distribution in terms of finite series. A comparison with the approximate procedure of Hamming is given. HE physical principles and applications of an extremely physicalprinciple efficient form of metallurgical refinement has been described by Pfann. The purpose of the present paper is to describe a method of analyzing exactly the particular program used which enables the segregation effect to be predicted for any number of molten-zone passages in a long ingot. The method is applied to the particular case of refinement of an ingot whose impurity initially is uniformly distributed throughout its length. A number of molten zones of equal length are passed through the ingot effecting a radical redistribution of impurity. Pfann has indicated an approximate method, due to R. W. Hamming, of calculating the resultant concentration after each successive zone pass for a particular value of the segregation constant defined in his paper. Here a solution will be presented in terms of the number of zone passes and the segregation constant. The expression, though cumbersome, is exact and susceptible to ordinary numerical computation procedures. The results of a similar computation using the procedure of Hamming are presented in a table together with the exact results of the present method. The discrepancy in terms of absolute concentrations is tabulated for the first eight zone-lengths. To establish the notation (which follows that of Pfann1 as closely as possible) and physical basis of the analytical equations, the physical model and principal assumptions may be reviewed. An alloy of two elements, where there is formed a continuous range of solid solutions, usually does not melt as a simple compound. Rather, a temperature is reached where the solid solution is in heterogeneous phase equilibrium with a liquid solution of different composition. The temperature dependence of these equilibrium compositions forms part of the phase diagram. For very small concentrations of a solute B in a solvent A, this usually takes the form of Fig. 1. Sometimes the solidus and liquidus slope upward. This corresponds to a segregation constant (defined below) which is greater than unity. The segregation constant is now defined as k = Cn(x)/CnI(x) [1] where C,,(x) is the impurity concentration in the solid ingot at distance x during the nth passing of a molten zone and Cnl (x) is the impurity concentration of the liquid zone from which the solid at dis- tance x is formed (see Fig. 4 of ref. 1.) C (x) remains the same after passage of the zone. The constant k may be either greater or less than unity in general. Purification in the former case is effected only in a finite ingot and in the portion that is melted last. For k less than unity purification is effected even in an infinite ingot. The method which follows gives, in the former case, the successive increases in impurity concentration and, in the latter case, the successive decreases in concentration. The general case of impurity redistribution will be considered first, and purification will be discussed later on. The analysis rests on the following assumption: The movement of the zone is too rapid to allow appreciable atomic rearrangement in the solid sections and too slow to disturb the uniform impurity distribution in the liquid zone characteristic of equilibrium. Hence, the composition in the solid at the left solidifying interface will be determined by Eq. 1 while the impurity concentration of the liquid zone will be uniform throughout its length. The reasoning which follows closely parallels that of Appendix 11 in Pfann&apos;s paper. It is reviewed here for the case of the nth zone pass in order to make clear the meaning of an operator essential to the present method. Fig. 4 of ref. 1 shows the movement of a molten zone of length 1 in an ingot of total length d. Each Cn(x) can be determined from the condition that the amount of solute added to the zone during an incremental advance, dx, is due to the melting in of a solid portion C(x)dx and the freezing out of kCnl(x), that is d I —r- CnL (x) dx = Cn-1 (x+l)- kCnL (x) dx or, in terms of Cn(x) d k k —— C,(x) +—c.(x) =— Cn-1 (x + l). [2] dx l l This, of course, is derived from the main assumption, the fact that 1 is constant, and that the total impurity content previously present up to x + 1 is constant . A correction has to be made for the region (d — nl) < x < d. This is due to the zone length changing during the passage of the solidifying interface beyond x = d — 1. Since the general solution would be too complicated otherwise, only the region 0 < x < d — nl is considered. The general solution of Eq. 2 is

Jan 1, 1954

By C. Chu

An investigation has been made of the radial heat-wave process using a mathematical model in two-dimensional cylindrical coordinates. This model considers combustion, convection and conduction inside the reservoir, but only conduction in the bounding formations. From a study of the general features of the process, an important phenomenon has been revealed, namely, the feedback of heat into the reservoir on the trailing edge of the heat wave. The effects of various process variables on the performance characteristics of the process have also been investigated. It was found that up to the time when the combustion front reaches a given point, the per cent heat loss, provided it is not higher than 40 per cent, is approximately directly proportional to the square root of thermal conductivity arid fuel content, but inversely proportional to the square root of gas-injection rate and oxygen concentration. The effecr of reservoir thickness is more pronounced, since halving the thickness doubles the per cent heat loss. The most decisive factor in determining the center-plane peak temperature is the fuel content of the reservoir. Within the temperature range investigated, doubling the fuel content doubles the peak temperature in the early stage, but the rate of decline of the peak temperature is high. Reservoir thickness is also a very influential factor. The peak temperature is lowered when the thickness is reduced; however, the effect of thickness becomes less pronounced when the thickness is high. Reduction of oxygen concentration increases the peak temperature in the early stage but lowers it afterwards because of the higher rate of decline of the peak temperature. Increase in gas injection rate or decredse in thermal conductivity geives a higher peak temperature which stays high for a longer period. The propagation range of the heat wave is chiefly governed by the fuel content of the reservoir. An increase of 0.2 1b/cu ft in the fuel content increases the propagation range by 100 per cent. The propagation range is more than doubled by doubling the gas injection rate, or reservoir thickness, or by reducing the thermal conductivity by 50 per cent. Comparatively, oxygen concentration has less effect on the propagation range. INTRODUCTION Several investigators have conducted theoretical studies of a radial heat wave. Vogel and Krueger1 studied a system with a moving cylindrical heat source of constant temper- ature, considering conduction in the radial direction only. Ramey2 included conduction in the vertical direction in his studies. Bailey and Larkin2 attacked a more general problem where initial well heating, vertical heat losses and arbitrary frontal velocities were included. In all these studies, however, conduction was considered to be the only means of heat transfer. Bailey and Larkin in a later paper included the effects of convection in a study involving both linear and radial geometries. Vertical heat losses were neglected in the radial case. Katz5 studied a similar problem in a one-dimensional radial model, using a heat-loss coefficient to account for vertical heat losses. Selig and Couch6 mployed a cylindrical model and investigated two limiting cases. In one case they considered no heat loss from the reservoir whereas in the other they assumed a constant temperature at the interface between the reservoir and its bounding formations. Thomas&apos; studied a more general case but assumed a permeable bounding formation so that the convection effect is not confined to the reservoir. In the present work a more realistic and more generalized model is used. It involves a two-dimensional cylindrical system with combustion, convection and conduction inside the reservoir, but only conduction in the bounding formations. The purpose is to establish the temperature distribution both inside and outside the reservoir, to study the general features of the radial heat wave process, and to investigate the effects of various process variables on the performance characteristics of the process. THEORY We fist consider a circular porous reservoir of thickness H extending vertically from y = — H/2 to y = + H/2. The reservoir extends from a well bore radius r, to an external radius re. A stream of oxygen-containing gas is introduced into the reservoir through the wellbore. The oxygen-containing gas reacts with the fuel contained in the reservoir and forms a combustion front wherever the prevailing temperature can support the combustion. It is here assumed that this combustion front constitutes a cylindrical surface source of heat having an infinitesimal thickness in the radial direction and extending vertically throughout the whole thickness H. This is designated as Region I. We next consider a Region II corresponding to the upper and lower formations bounding the reservoir, extending from y = — - to y = — H/2 and from y = + H/2 to y = + m. Since r, is very small, we may assume that the two bounding formations have the same dimensions, symmetric with respect to the center plane of the reservoir. In this way, we may take the upper half of the system alone into consideration. In contrast with

By Martin F. Littmann

Inclusions of MnS and Fe3C have been introduced into single crystals of 3 pct Si-Fe to study their effects on recrystallization behavior and textures after cold rolling and annealing. The presence of MnS in (110) [001] and (111)[112] crystals inhibited primary grain growth and promoted secondary recrystallization but did not alter the texture significantly after annealing at 1200°C. The presence of Fe3C in (llO)[OOl] and (100)[001] crystals caused a refinement of the primary re crystallized grain size but did not promote secondary recrystallization. THE texture behavior of single crystals of 3 pct Si-Fe during deformation and recrystallization has been studied by numerous investigators. The early work of Dunn&apos; followed by Decker and Harker2 involved relatively small cold reductions. More detailed studies of Dunn3&apos;4 and of Dunn and Koh5&apos;6 involved a reduction of 70 pct and recrystallization at 980°C for several crystals. Walter and Hibbard7 studied a greater variety of initial orientations and sought to relate the textures to those of polycrystalline material. Attention was focused on the nucleation process during early stages of annealing and on surface energy effects in studies by Walter and Dunn8 and by HU.9&apos;10 One of the most extensive investigations has been reported by T. Taoka, E. Furubayashi, and S. Takeuchi.11 Most of this work has been conducted using relatively pure crystals with minimal amounts of precipi-tate-forming elements such as carbon, oxygen, sulfur, and nitrogen. Recently, however, S. Taguchi and A. Sakakura have observed that AIN precipitates can alter the recrystallization textures of rolled (100)[001] crystals.12 The present studies were initiated to determine effects of MnS and Fe3C precipitates on recrystalli-zation and grain growth behavior of rolled single-crystals of 3 pct Si-Fe. Both of these types of inclusions play significant roles in the recrystallization behavior leading to the formation of the (110)[001] or cube-on-edge texture in commercial grain-oriented silicon iron. It is well known that (110)[001] primary grains are formed by recrystallization of (110)[001] or (11 l)[ 112] crystals after cold reduction of about 60 pct or more. Crystals of these orientations, therefore, were selected for study of the effect of MnS in-clusions on grain growth. On the other hand, a major component of the texture of cold-rolled, polycrystal-line 3 pct Si-Fe is the (100)[011] orientation. The function of Fe3,C inclusions is of interest for this orientation. EXPERIMENTAL PROCEDURE The single crystals used are listed in Table I and were obtained from commercial Si-Fe alloy processed to produce (110)[001] and (100)[001] texture by secondary growth. The cube-on-edge material was 0.59 mm thick. Suitably large (110)[001] crystals 25 mm wide were selected and their orientations were determined using an optical goniometer. Etch pits for texture determination were formed by a ferric sulfate solution. The other crystals used in the study with (100)[001], (100)[011], and (111)[112] orientations were obtained from sheet which contained large grains developed from secondary recrystallization by a surface-energy driving force.13 Most crystals had a (100) plane very nearly parallel to the sheet surface and the rolling direction could be selected readily. The same sheet also contained a few crystals with (111) planes parallel to the sheet surface, these also being a result of growth by surface energy. The crystals selected from the sheet were about 25 mm wide and 0.25 to 0.28 mm thick. As shown in Table 11, the crystals already contained about 0.070 to 0.10 pct Mn. Inclusions of MnS were incorporated into crystal 36 in the following manner. The crystals were first sulfurized by holding them Table I. Initial Orientations of Crystals Crystal No. Initial Orientation Thickness, mm Special Treatment 34 (I10) [00l]* 0.59 None 36s (110) [001] 0.59 Sulfide precipitates added 30,40 (111)[Ti21 0.28 None 43s (III) [Ti21 0.28 Sulfide precipitates added 37 (100) [Oll] 0.30 None 37C (100) [01I] 0.27 Carbon added 41 (100) (01I] 0.25 None 41C (100) [OI11 025 Carbide precipitates added 42 (100) [OOl] 0.25 None 42C (100) [001] 0.25 Carbide precipitates added *Tilted 4 deg to r~ght about R.D. Table II. Compositions of Crystals Special Treatments Base Analysis ~ ______________________£________________Crys- Crystals Pct Si Pct C Pct Mn Pct S Pct N Pct Al tal Pct C Pct S 34.36 2.93 • 0.099 <0.005 - 0.0014 36S 0.011 30.37 to 42 2.78 0.0057 0.070 0.001 0.0008 0.0011 43S 0.022 37C 0.029 -41C 0.028 -42C 0.026 *Estimate 0.004 pct. Oxygen estimated <0.003 pct on all samples

Jan 1, 1970

By W. Philippoff

ALTHOUGH Gaudin1 and more recently Sutherland2 have calculated the probability of collision of a falling mineral particle with a rising bubble, there is no published information concerning the details of the mechanism of attachment of a collector-coated particle to a bubble. During the past year the writer has developed a theory for the mechanism of attachment, which has been substantiated experimentally.&apos; Funds for the investigation and for some of the equipment used have been supplied by the Mines Experiment Station of the University of Minnesota. Motion picture studies of the phenomena involved in the collision between mineral particles and bubbles, such as those of Spedden and Hannan,3 show that the contact can be completed within 0.3 millisec. Formulas developed for rigid bodies have hitherto been used&apos; for the calculation of the motion of bubble and particle, but it is obvious that a bubble cannot be regarded as a rigid body. On the contrary, Spedden and Hannan&apos;s pictures show a great degree of deformation during the collision. The time of attachment was calculated as the time the particle drifted past the bubble. Time of Collision The theory presented in this paper enables calculation of the time of collision; using the concept that the bubble, or more generally, a liquid-air interface, acts as an elastic body. The elasticity, defined as the restoring force on a mechanical deformation, is caused by, the surface tension and is the result of the principle of the minimum of free surface energy. It is well known that an elasticity together with a mass determines a frequency of vibration. The vibrations of jets and drops caused by the elasticity of the interface are known to comply exactly with the classical theory of capillarity.5 However, the vibrations of isolated bubbles, as distinct from foams, have not been investigated previously. The following equation, presented elsewhere,&apos; has been deduced for these frequencies: [3fB = 9.20•&apos;./V•Vn- (n-1) • (n+2) /8[1]] in which fB is the frequency of a harmonic of the bubble in cycles per second, V the volume of the bubble in cc, n a number determining the order of the harmonic, and n = 2 the basic vibration. The first (basic) harmonic describes a change of the spherical bubble to an ellipsoidal bubble. The higher harmonics are more complicated, for the circumference of the bubble is divided approximately into as many parts&apos; as the order of the harmonic. As an example, Spedden and Hannan&apos;s published motion picture of, a vibrating bubble corresponds to the sixth harmonic. Eq 1 shows that only the first and third harmonics are simple multiples (1 and 3), all the others being irrational fractions of the basic frequency. This means that the shape of the vibration can change with time and is in general unsymmetric in respect to the time axis. Such conditions prevail when there is a distributed elasticity or mass, as in the case of vibrating membranes or rods. The constant 9.20 is valid for water at room temperature, but a general solution involving the physical constants of the liquid has not been found. The case of the floating particle is much easier to treat I than that of the bubble. It can be assumed that the elasticity is caused exclusively by the interface and that the mass is concentrated in the particle together with some adhering water. The following expression for the frequency of a system, of one degree of freedom can be applied: [1E/m[2] fP = 27] Here f, is the frequency of the particle vibration in cycles per second, E the elasticity in dynes per cm, and m the mass in grams. The classical theory of impact phenomena gives the time of collision during the striking of a spring (in this case the surface of the bubble) by a mass, as: [t~ = 2/f = 7r\/m/E[3]] It is now possible to develop an expression for the elasticity of a floating cylindrical particle. The force equilibrium of a cylinder floating end on at the air-liquid interface is given by the well-known equation (Poisson&apos; 1831) [aP = 4 D2.pL•g•h +7rD•y sin a[4]] which accounts for the buoyancy and the action of the surface tension where P is the force acting on the particle in dynes (weight-buoyancy), D the diameter of the cylinder in cm, pL the density of the liquid in grams per cc, g the acceleration of gravity = 981 cm per sec2, h the depression of the cylinder below the surface of-the liquid in cm, y the surface tension in dynes per cm and a the supporting angle&apos; or the one required to insure equilibrium, a being smaller than the contact angle ?. Although demonstrated by Poisson, it has not

Jan 1, 1952

By A. L. Slaughter

The Homestake mine, located in western South Dakota, was discovered in 1876. The first reported production was in I 878. Total production through 1965 is 6,554,249 troy ounces of silver and 27,961,276 troy ounces of gold, worth $987,000,000 at present prices. Precambrian sedimentary formations at Lead total 20,000 feet. The Poorman Formation, the oldest, is chiefly ankerite carbonate. The Homestake Formation is iron-magnesium carbonate. The younger formations are argillaceous with some quartzites. The Cambrian Deadwood Formation unconformably overlies the Precambrian. All are cut by Tertiary intrusives. Sideroplesite schist of the Homestake Formation was converted to cummingtonite schist in the zones of higher-grade metamorphism. The Precambrian rocks show the effects of extreme isoclinal folding. A second stage of folding ( cross folds) may have been caused by the Tertiary intrusives. All folds plunge to the southeast. The Homestake ore bodies are pipe-like replacements of the Homestake Formation in zones of cross folding. It is believed that dilatation of the schists has increased permeability in these zones. Chloritization of the schists is the most widespread effect of the mineralization which is divided into four stages. Principal minerals of the first stage are quartz, chlorite, and arsenopyrite; in the second stage, quartz, ankerite, and pyrrhotite. In the third stage only pyrrhotite was deposited. The fourth stage followed the intrusions of Tertiary dikes and deposited mostly pyrite and calcite. Gold accompanies all stages and is always the last mineral to be deposited. It is most closely associated with arsenopyrite of the first stage but can be interpreted as having been deposited during the fourth stage and superimposed on the products of the earlier stages.

Jan 1, 1968

By Henry Louis

IN the discussion on the paper on subsidence by R. V. Norris and H. W. Montz (Teohnical Publication No. 153), H. N. Eavenson has been good enough to quote some of my views regarding the phenomena of subsidence; he has, of course, only mentioned these briefly, and as he has not represented them quite correctly, it is evident that I have failed to make them clear. Seeing that he, and apparently some of the others who took part in the discussion, appear to hold views different from my own, I think it advisable to put my opinions down as definitely and as clearly as possible, because it appears to me at least possible that some of the differences above referred to may be differences of language and definition rather than of fact. The statements I propose to submit refer to the simplest cases, namely where an area in a practically horizontal bed has been entirely worked out. My experience has been confined to beds of bituminous coal and of ironstone, but D I do not at the moment see why there should be any difference in principle between the working of a bed of anthracite and one of bituminous coal, provided that the other conditions are the same. I wish to emphasize that I am considering the conditions of complete working out of the mineral bed with the roof allowed to come down and form goaf in accordance with the general British practice; 1 am excluding, therefore, methods of hydraulic, pneumatic, and hand stowage where extraneous material is brought in to hold up the roof. I am also excluding the case of bord and pillar working where pillars of small size are deliberately left in, apparently with the idea that these will subsequently crush and let the roof down gradually. Such a method of mining has long been discontinued in this country, indeed in Europe generally, and I venture to predict that the time will come when such a recklessly wasteful method will no longer be tolerated even in the United States. Further, I am referring entirely td static conditions after the mineral bed has been worked out and the ground has come to rest; the phenomena that occur during the course of extraction are much more complicated, and these I am not discussing here. Under these conditions, I have

Jan 1, 1929

By J. E. Harris

The metallic elements, beryllium, calcium, cerium, lithium, manganese, titanium, vanadium and zirconium are used in metallurgical practice in relatively small percentages for the purpose of improving the physical properties of various alloys. No important uses for any of these elements have thus far been developed either in the pure form or in alloys of which they constitute the major constituent.

Jan 1, 1935

By H. M. Beatty, T. L. Joseph, Gust Bitsianes

SUCCESSFUL blast-furnace operation depends upon securing an optimum balance between a number of important variables. This balance will vary somewhat from furnace to furnace in the same plant and with raw materials available in different plants. It is difficult to isolate the effect of any one variable unless it has a rather pronounced effect upon the efficiency of operation. The physical properties of iron ore and coke are known to affect the process, yet it is difficult to set up any definite yardstick by which these differences can be appraised. In recent years, whenever practicable, operators have taken steps to obtain better control over the absolute size and uniformity of size of the ore and coke. The size and physical character of the stone, however, have received comparatively little attention, emphasis being placed upon chemical composition, fluxing efficiency, and action as a desulphurizing agent. Since the stone occupies only about 10 per cent of the volume of the stock column, its influence upon permeability is less than that of the ore and the coke. The large pieces now used have a tendency to roll to the center and thus increase the permeability of this part of the stock column. Smaller pieces would be more effective in promoting the permeability of denser portions of the stock. The size and physical properties of blast- furnace stone are important also for reasons best understood by considering the results obtained by the crushing and the sizing of iron ore. Crushing ore to about 2 in. at Provo, Utah, and to about I in. in Alabama produced material somewhat less permeable to gases, even though sized. In spite of some sacrifice in permeability, the efficiency of the process was improved by crushing and sizing the ore, as indicated by a substantial saving in fuel and increased output. This saving in fuel is due in large measure to more thorough reduction of ore in the upper part of the furnace and to a corresponding decrease in the amount of carbon consumed prematurely above the tuyeres by the reaction CO2 + C = 2CO ? 70,080 B.t.u. [I] The physical properties of stone, its size and rate of calcination are important because they influence the rate at which C02 is released and the completeness of calcination before reaching a level in the furnace where the temperature does not exceed 1050°C. (1920°F.). Briefly, carbon dioxide from the limestone or from the reduction of ore may cause premature com- bustion of carbon above the tuyeres. Assuming that 1000 lb. of limestone is used per ton of pig iron, about 435 lb. of C02 will be liberated during calcination of a good grade of stone. If all this CO2 from the stone were to oxidize carbon prematurely, about 120 lb. would be consumed above the tuyeres in a heat-absorbing reaction. The amount of carbon thus consumed when a

Jan 1, 1942

By J. E. Burke, C. W. Mason

IN attempting to study precipitation from a tetragonal lattice using solid solutions of bismuth in tin, it was found that although a Widnmanstatten pattern is observed 1 only a qualitative analysis of the orientation relationships is possible, because of the unusual structural changes that accompany the precipitation process MICROSCOPICAL STUDIES Alloys were made from Chempur tin (Standard samples 42b and 42c, National Bureau of Standards), and bismuth (Kahlbaum C P ) by melting neighed quantities together under palm oil, stirring well, and casting in a heated graphite mold The polishing and etching techniques employed largely govern the visibility of the structural changes The preliminary surfacing operations were similar to those recommended by Villela and Bergekoff,5 through BehrManning 3/o abrasive papers, lubricated by a solution of paraffin in kerosene A rough metallographic polish was next given, using a thin cotton cloth charged with relevigated alumina (maximum particle size of about 4µ) and soap solution, repeated etching and polishing served to remove disturbed metal For high-power examination better preparation was necessary It was found that on such soft metals the threads of the fabric, rather than the abrasive, cause most of the scratching Cotton outing flannel, which had been brushed so that the nap lay down, was fairly satisfactory, but a Heavy grade of silk velvet (not the noncrushable kind) was found to be better, especially after some use A better procedure was as follows The metal lap was warmed slightly, and a 4-in circle of woolen broadcloth was cemented to its center by a thin film of melted paraffin The broadcloth was then moistened with water, and a 30 to 40 per cent solution of sodium hydroxide heated to about 50°C was poured over it, allowed to stand for 1 to 2 min and then washed off It was neither necessary nor desirable to remove all the sodium hydroxide from the cloth, since its etching action aided in the removal of the flowed layer from the sample The cloth was then charged with a paste of the relevigated alumina in water Since this lap did not remove deep scratches, it was necessary previously to polish the specimen on some material such as the silk velvet The sodium hydroxide softens and partly gelatinizes the woolen lap covering, permitting a scratch-free polish, but its action continues, and the cloth deteriorates after about 24 hr This is not serious, because a new lap can be prepared in about 5 min, and only small pieces of cloth are used Etching with a strongly acid solution of ferric chloride was found satisfactory for removing the flowed layer For the final etching, the most satisfactory reagent was that of Taffs,7 the formula for which is FeC13 6H20, 2 grams, HC1, 5 c c , H2O, 30 c c , C2H5OH (95 per cent), 60 c c This etchant reveals differences in com-

Jan 1, 1941