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

Jan 1, 1937

By P. St. J. Perrott

AN explosive of balanced composition might be expected, on first consideration, to develop maximum propulsive strength.1 This hypoth¬esis is based on the assumption that an excess of oxygen would act simply as an inert material with a consequent lowering of flame temperature, also that a deficiency of oxygen would tend toward incomplete reaction of the combustible materials, thereby preventing development of the full strength of the explosion. Actually, however, it can be shown both theoretically and experimentally that an explosive having a certain oxygen deficiency will develop the greatest propulsive strength. This fact has been known to the technical staffs of explosives manufacturers for many years, but it has not always been recognized by explosives engineers in the field. For example: There is a fairly widespread opinion that the wrapper of a stick of dynamite is merely a container for the explosive and that it plays little if any part in the development of propulsive strength. Actually, it can be shown that the wrapper enters fairly completely into the explosive reaction. In the case of most gelatin dynamites, a given weight of explosive from which the wrappers have been removed will develop considerably less strength than the same weight of explosive plus wrapper, in spite of the fact that the latter combination contains less weight of the actual explosive ingredient. It can also be shown that a cartridge 7/8 in. in diameter may be stronger, weight for

Jan 1, 1928

By G. R. St. Pierre, M. J. Pool, R. Speiser

The activities of chromium in solid Cr-Ti solulions contaitning from 10 to 90 at, pct Cr were measured over the temperatutre range 1250" to 1380°C. The Knzudsen effusion technique with direct weighing of the Knudsen cell was used. This was possible because the vapor pressure 0f chromium is about 600 times greater than the capor pressure of titanium so that the amount 0f titanium effusing could be neg-Lected. the activities of titanium were determined by g-raphical integration of the Gibbs-Duhertz equatiotz. The solutio~ls sllcdied exhibited positive deviations from Raoult's law, but they approached ideality as the temperature was raised from 125 to 138t C. The integral free energy of mixing was calclated from the activity values. AF has a maximum value of - 1.66 kcal a1 1390°C and a composition oj 55 at. pcl Cv. The free energy of formation of 'TiCr, is —0.76' lzcal a1 1250°C. The heats and entropies of mixing usere determined using the second law and thus tile mlues could be in error by a considerable amount. The Cv-Ti system is not a regular solution. ThE increasing emphasis on application of various models to alloy formation and solution behavior has led to an intensified interest in the thermochemistry of alloys. In a majority of the cases where different models have been applied the alloy system used was a simple one. However, the amount of data available on more complicated systems is small and in order to fully understand the behavior of metallic solutions more experimental work has to be carried out on these systems. The Cr-Ti system is reasonably complex and even though this system was being investigated as early as 1937 by Kroll,' no previous work has been done on the thermodynamic properties of either the liquid or solid state. This research was undertaken to determine the thermodynamic properties of solid Cr-Ti alloys. EXPERIMENTAL PROCEDURE The experiments on the Cr-Ti system were carried out in a water-cooled metal vacuum system. This system is composed of a brass vaporization chamber wound with copper tubing for cooling purposes, a brass liquid-nitrogen trap, an oil diffusion pump, and a Duo-Seal forepump. The pressure in the system is measured with an ionization gage. The interior of the vaporization chamber is shown schematically in Fig. 1. The Knudsen cell is supported by the molybdenum tripod, and a magnetically operated shutter is provided to protect the Pyrex sighting glass against deposition of metallic vapors in the intervals between temperature measurements. Heating is accomplished by means of a 20-kw 450-kc Westinghouse oscillator. The susceptor in this case is 10-mil tantalum seamless tubing which also forms the outside of the sample container. The remainder of the sample container consists Of an im~ervims re-crystallized alumina crucible and a 10-mil-thick tantalum lid. Two holes are drilled in the lid. The diameters of these holes were measured with the calibrated stage of a "Tukon" microhardness tester. The thicknesses were measured with a micrometer. A Leeds and Northrup disappear ing-filament optical pyrometer was used to measure the temperature. This is sighted through the smaller of the two holes in the lid and corrections for the emissivity of the sample were not necessary since the ratio bf cell length to hole diameter was large enough to insure a hohlraum. The pyrometer was calibrated at the ~~t~~~l Bureau of Standards, and the correction for the Pyrex sighting window was determined in the laboratory. The titanium used in this investigation was obtained from Mallory-Sharon and the chromium from The Union Carbide Metals Co. The reported purities were

Jan 1, 1968

By John Birkinbine

Among the notable deposits of iron-ore, the Iron Mountain at Durango, Mexico, is prominent. But, although it has been noticed in records of travel and official reports for three centuries, the statements made concerning it have been so largely alloyed with improbabilities that general credence has not been given to data relating to the Cerro & Mercado, that being the name by which this remarkable mountain of ore is known. Location. Geographically, the mountain is centrally located, being situated immediately at the City of Durango, which is distant in direct lines (as the crow flies) as follows: From the Rio Grande River at El Paso, Texas, in the north, 510 miles; from the same stream at Laredo, Texas, in the northeast, 410 miles; from Tampico, in the east, 475 miles; from the City of Mexico in the southeast, 520 miles; from Mazatlan in the west, 110 miles. At El Paso, the standard-gauge Mexican Central Railroad, and at Laredo, the narrow-gauge Mexican National Railroad, enter Mexico. Tampico is a prominent Mexican port on the Gulf of Mexico, and Mazatlan occupies a similar position on the Gulf of California. To reach Durango from Laredo or Tampico, spurs of the Sierra Madre Mountains must be crossed, and between Mazatlan

Jan 1, 1885

Economic Significance of High-grade Concentrates BY PAUL M TYLER AND CARLE R HAYWARD (Min & Met, Dec, 563 4000 words) Generally pyro¬mctallurgical methods yield a higher recovery but cost more per ton of ore treated Milling methods are inherently cheaper for the reason that they do not involve dissipa¬tion of heat energy in slag formation, ctc It is vaguely realized that the smelter man could do a better job if he were supplied with purer raw materials but hard¬headed mill men have been offered little inducement to do a really good job of cleaning concentrates To do this may involve some sacrifice in percentage yield and in mill capacity and unless there is a compensating saving in freight and smelter charges, it simply is not good business to go beyond a certain point in the way of making clean concentrate Opportunities exist for eliminating one or more steps in the expensive series of processes for recovering various metals, or at least reducing the volume of materials that has to be handled at the most costly steps The beneficiation of nonmetallic minerals likewise affords numerous examples of over-all economies obtainable through more refined methods of mechanical improvement All this leads to the conclusion that perfecting selective processes for isolating pure minerals (e g, galena) virtually free from other sulfides as well as gangue may be productive of industrial economies Conversely, cheapening smelting methods may invade the field of mechanical improvement of ores but, as Kiphng said, that is another story

Jan 1, 1937

By George D. Roberts

INTRODUCTION CIVIL engineers are primarily interested in maximum core recovery. This is even more important in foundation work than in mining investigations where sludge samples are of some value. The soft materials, such as clay, gouge, or partially decomposed seams that are most readily ground up or washed away, are the materials that usually have the greatest influence on foundation and leakage conditions. Undisturbed samples of such materials should be obtained for detailed geological examination and laboratory tests. Therefore the attainable goal of sampling in connection with foundation investigations is the recovery of 99.9 pct of undisturbed core. FACTORS CAUSING CORE LOSSES The principal factors contributing to core losses are: (I) coring badly fractured or very soft material; (2) use of improperly designed coring equipment, including the use of bits of too small a diameter; (3) lack of the proper training and attitude on the part of the drillers and pertinent technical information on the part of the supervising personnel. Little can be done about the character of the material being cored but the other two factors contributing to unsatisfactory performance can be corrected. Although the title of this paper is the improvement and standardization of core barrels, it is believed that the drillers' shortcomings and the lack of pertinent technical literature are more detrimental to good core recovery than either of the other factors. USES FOR LARGE DIAMETER CORE BARRELS It is well known that the use of larger diameter bits and core barrels generally produce better cores, particularly when sampling soft or broken material. The use of larger and larger bit diameters and the insistence on better core recovery is well demonstrated by the change in practices of the various districts of the Corps of Engineers. Today NX core is the smallest diameter commonly permitted for investigational work and the more active districts are using coring bits up to 6 in. in diameter, as well as 36 and 40-in. calyx rigs. The latter size has proved to be just as economical because it provides more room for core removal and cleanup operations. The use of large diameter cores to replace the driving and jacking methods of obtaining soil samples is also increasing. The 5 7/8-in. Denison sampler, developed by H. L. Johnson to obtain samples from soft formations, is one example. The principal uses for bits larger than NX are: sampling soils and semi-consolidated rock; sampling decomposed rock or rock with soft seams; sampling concrete; obtaining samples for laboratory tests; drilling drainage holes, and other miscellaneous work. CORE DRILLING PRACTICES OF SEVERAL ENGINEER DISTRICTS Little Rock District The writer was employed in the Little Rock District from 1938 until 1942. Prior

Jan 1, 1947

By Francisco Cadena

THE construction of Norris Dam, built by the Tennessee Valley Authority on the Clinch River, a tributary of the Tennessee River, involved the production of coarse and fine aggregate for approximately 1,000,000 cu. yd. of concrete. A hammer-mill plant for the manufacture of sand from quarried rock was indicated as the most economical method of providing this material. The abrasive character of the feed as compared to the average hammer-mill feed made it necessary to control operations rather closely, and this resulted in the accumulation of many data bearing on production and maintenance. This paper will deal only with three specific sets of data, accompanied by such general information as may be necessary to explain the conditions under which they were obtained and followed by discussions on the relation of silica content to hammer wear, comparative costs of slugger and stirrup hammers, and comparative costs of tool-steel and manganese-steel grate bars. Coarse Aggregate Aggregate for the concrete poured at Norris Dam came from a dolomite quarry within 2000 ft. of the west abutment of the dam. Geologically this rock is known as a Knox dolomite. A typical chemical analysis is given in Table 1. TABLE 1 .-Typica.1 Chemica1 Analysis [PER CENT H20,1100F ............................................ 0.0'2 Ignitionloss ............................................. 43.56 MgO .................................................. 19.19 CaO .................................................... 29.07 FezO .................................................... 0.39 A1203 .................................................... 1.94 FezO .................................................... 0.39 A1203 .................................................... 1.94 ..................................................... 5.75 SO2.. .................................................. Tr.] Rock was carried by 12-yd. dump trucks to a 42-in. gyratory crusher set at 6 1/2 in. The product of the primary crusher was taken by a belt conveyor to a double-deck vibrating screen followed by a 5 1/2-ft. cone

Jan 1, 1937

By Y. Nakahiro

The removal of heavy metal compounds from a synthesized waste cyanide solution is achievable by a precipitation-flotation method. However, the differential separation of constituting metals by this method was thought to be very difficult. The present author found that addition of ferrous salt to the synthesized waste cyanide solution of cadmium and copper can modify the separation characteristics of these metals. In this paper, the separation of cadmium from copper in the synthesized waste cyanide water by the precipitation-flotation method is discussed. This differential flotation uses ferrous salt as a precipitant and sodium oleate as a collector. Based on a series of fundamental flotation tests, actual differential flotation tests were made. The separation of cadmium from copper in the synthesized waste cyanide water was found to be satisfactory. This method can be effective for the removal of difficult-to- separate colloidal precipitates from liquids by the sedimentation method, provided the applicability of this method to the separation of the other metals is promising. This consists of the intensive studies which have been conducted at author's laboratory.

Jan 1, 1980

By Craig S. Hartley

Expressions are obtained for the energy changes associated with the reaction of (a& (111) slip dislocations on intersecting (110)planes in anisotropic bcc metals. An energy criterion for assessing the likelihood of dissociation of the products of such reactions is also presented. It is found that the "burrier reactions" which form a(100) dislocations at the intersection of two active {110) slip planes are more energetically favorable in metals which exhibit a high value of Zener's anisotropy factor, A, than those which have a low value. The results are presented in a form which permits the stacking fault energy to be obtained from a measurement of the separation between par-tials in a dissociated configuration. However, until accurate calculations or measurements of the stacking fault energies involved are available, it is not possible to assess the physical importance of dissociated dislocations. In a recent paper,' the energy changes associated with several types of reactions between two slip dislocations, (a/2)(111){110), in bcc structures were calculated.* Isotropic elasticity and the approxima- tion v = -3- were employed. The purpose of this work is to present calculations of the energy changes for many of the same reactions using anisotropic elasticity. The problem of dissociation of a(100) and a(110) dislocations is also considered, and maximum fault energies for which dissociation will be energetically favorable are calculated for several bcc metals. Two general types of reactions are considered; those for which the reactant (a/2)(111) dislocations have long-range attractive forces and those for which the reverse is true. An example of the former is: (a/2)[lll] + (a/2)[lll]-a[l00] while the latter are typified by: (a/2)[lll] + (a/2)[111] -a[011] Only reactants lying in different slip planes are considered; therefore, the products must lie along (111) or (100) directions, which are the intersection of two {llO} planes. It will be assumed that the reactants and products are infinitely long parallel dislocations, since in this case the energy change associated with the reactions is a maximum.' THEORY The self-energy per unit length of a straight mixed dislocation in an anisotropic medium can be written? where b is the Burgers vector, K is an appropriate combination of the single-crystal elastic constants, and R and ro are, respectively, outer and inner cut-off radii of the elastic solution. The energy given by Eq. [I] does not account for any variation of the core energy with orientation. This could be manifested by an orientation dependence of the core radius or, equivalently, the Peierls width, of the dislocation. However, the energy contribution due to this source is expected to be small, and current models of the dislocation core are not sufficiently accurate to justify such a refinement. It has already been shown that for the isotropic case the energy contributions due to nonzero tractions across the cores of the reactants and products exactly cancel one another in the reaction.' Accordingly, it will be assumed that this contribution to the total energy change in the anisotropic case is small. In the subsequent discussion it is also assumed that the core radii of the reactant and product dislocation are the same and that, where stacking faults are formed, the faulted region is bounded by the centers of the partials. Consequently only changes in elastic energy due to the reactions will be considered. When the dislocation is parallel to either the (111) or the (100) directions, K may be written:375 K = (Ke sin2 a + Ks cos2 a) [2] where K, and Ks are the combination of elastic constants corresponding to an edge and screw dislocation lying along the same direction as the mixed dislocation, and a is the angle between the direction tangent to the dislocation line and the Burgers vector. Eq. [2] should not be confused with the isotropic approximation to the variation in energy with line Orientation.6 It should be noted that the essentially isotropic expression for K is a result of the characteristic symmetry of the (111) and (100) directions and is not, in general, valid for other dislocation directions in anisotropic cubic metals. The energy* change for a reaction in which the re- actant and product dislocations are parallel perfect dislocations can be written: where Ep and E, refer to the self-energies of the products and reactants, respectively. For dislocations parallel to (100) and (111) directions, Eq. [3] becomes:

Jan 1, 1969

By Bruce R. Lipin

Chromite, the only ore of chromium, occurs almost exclusively in mafic-ultramafic rocks and their weathering products. However, not all kinds of mafic-ultramafic rocks are favorable hosts for possible low-grade chromite deposits. For instance, chromium-bearing basalts are not favorable because they commonly contain <0.3% Cr203, and chromite is almost always less than 50 mp in diameter, if it is present at all. Chromite-bearing ultramafic rocks in stratiform and alpine complexes tend to be either ore grade (>25% chromite) or very low grade (<2% chromite); intermediate rocks are scarce. In most complexes, large tonnages exist only in the <2% chromite rocks and the composition of the chromite in those rocks may be unsuitable for metallurgical use. Some nickel laterite districts contain more than lo8 tons of material with 2.0 to 5.5% Cr203, and hence, chromium could be a byproduct of nickel in some laterite districts. In addition, some chromiferous sand placers may contain tens to hundreds of millions of tons of material between 2 and 5% Cr203

Jan 1, 1983

By J. B. Woodworth

Under the above title it is desired to bring to the attention of assayers a short-cut method which has been perfected by Mr. A. S. Warren, of Buffalo, and the writer; has been used several years at three " Lake copper " refineries in occasional alternation with the regular " combination," or a wet and fire," assay; and has proved more rapid, and rather more accurate than the latter on all refined copper—namely, the direct cupellation of the silver chloride (+gold) precipitate, without scorification. No claim of priority is made for this direct method, as it has suggested itself to many others, and was mentioned by Mr. Warren in the symposium of assayers&apos; results brought together in 1895 by the Secretary," after the plan and suggestions of Dr. A. R. Ledoux.† Lately, this important subject of assaying copper-materials seems to have been re-opened for discussion. The shortening of time by &apos;the direct method is so considerable (nearly 20 minutes on a batch)—to say nothing of the saving

Jan 1, 1902

By T. W. Healy, P. Somasundaran, K. Ananthpadmanabhan

Hydrolyzable surfactants such as fatty acids and amines undergo, in addition to micellisation and precipitation, various associative interactions in aqueous solutions to form ionomolecular complexes such as acid-soap, dimers, etc., depending upon the solution conditions such as pH. The interaction of these collector species with the mineral surface and with other dissolved species in solution will play a significant role in determining the interfacial processes such as adsorption and flotation. Marked differences in the hydrophobicity imparted to the mineral surface depending upon the solution conditions such as pH can be attributed to possible differences in surface activities of the foregoing complexes. This aspect of solution chemistry of flotation system is discussed here for two widely used collectors, namely, oleic acid and dodecylamine. Equilibrium species distribution diagrams, based on the available literature data and on estimates of energy of interactions between molecules, have been obtained for oleic acid and dodecylamine solutions.

Jan 1, 1980

By C. R. Pelley

This paper describes the analytical characteristics of Western subbituminous coal and the manner in which these characteristics apply to their use in a utility-sized steam generator. It compares these characteristics with those of typical Midwestern coal and Eastern bituminous coal. The paper also reviews in detail the design considerations that must receive attention when various blends of these three coals, or any combinations thereof, are planned to be used. This research paper describes variations in analytical and utilization characteristics when coals from different origins are blended in order to achieve a predetermined sulfur content for the purpose of predicting sulfur oxides emissions as they affect environmental regulations and the resulting alterations in utilization characteristics such blending would cause, and how such blends of coal would affect a utility-sized steam generator.

Jan 1, 1979

By Clarence Linville

FULTON1 says: "Speiss is an artificial arsenide of iron containing smaller amounts of other metals. In constitution it is similar to a matte except that arsenic replaces sulfur." For the purposes of this paper it will be necessary to broaden the definition, and I propose the following: Speiss is an artificial mixture of arsenides, of which arsenide of iron may be taken as a type, but iron may be replaced in part or wholly by other metals (such as copper, nickel, cobalt, lead and zinc) and the arsenic may be replaced in part or wholly by antimony. In addition to antimony and arsenic, speisses often contain sulfur. Speisses usually also contain both silver and gold. Table 1 illustrates the variations that may be encountered. TABLE 1.-Speiss Analyses

Jan 5, 1925

By Jeffrey L. Thompson, Kenneth A. Gutschick, Robert C. Freas, Robert S. Boynton

Lime, the "versatile chemical," is, generally speaking, a calcined or burned form of limestone commonly known as quicklime, calcium oxide or calcia, or, when water is added, calcium hydroxide or slaked lime. Almost 40 different lime products are available, a fact which has contributed to the rather loose use of the term lime as well as to much confusion and misunderstanding. The term is frequently, albeit erroneously, used to denote almost any kind of calcareous material or finely ground form of limestone or dolomite. Lime is usually made from high-calcium or high-magnesium limestone, generally having a minimum of 97% combined carbonate content. Normally, high-calcium limes contain less than 5% MgO. When the lime is produced from a high-magnesium limestone, the product is referred to as dolomitic lime. Calcination, or the production of lime, has its origins in the earliest days of alchemy, with the general reaction class having been identified in an Arabic text printed in 1000 A.D. It was much later, however, in the mid-1700s to the mid-1800s before this basic reaction became understood from a scientific perspective. The production of lime has been so basic and simple that its underlying scientific principles have over the years received only intermittent investigation. Rather, much of the thought and inquiry has been directed toward the development of kilns. Thus, it has only been in the last 15 to 20 years that lime has received any concentrated scientific investigation relative to the thermodynamics and kinetics of the calcination and hydration reactions. Calcination refers to a broad class of reactions, of which the lime/limestone reaction is just one, wherein a substance is heated to less than its melting point, resulting in a weight gain or weight loss. In the calcination of limestone to produce lime, the basic chemical reaction is as follows: [CaCO3 (limestone) + heat (1000° to 1300°C)= 100 CaO (quicklime) + CO2 T 5644 or CaCO3 • MgCO3 (limestone) 10084 + heat (900°C to 1200°C) CaO • MgO (quicklime) + 2CO2 T 56 4088] While there is nearly universal agreement about the equilibrium conditions related to the limestone/lime reaction above, there have been numerous and varied calcination models developed for the reaction. Recent investigations have resulted in the development of the model shown in Fig. 1. From this model it can be seen that calcination is a function of both temperature and CO2 pressure. It does not, however, provide any indication of the rate at which the reaction takes place. Calcination is strongly time variant with different limestones. In a very broad sense this relates to the fact that the calcination reaction starts on the exterior surface of the limestone and then proceeds toward the center. As the calcination reaction takes place, the CO2 released at the reaction interface must make its way through the lime to the exterior surface. Therefore, because calcination is limited by gas diffusion to the surface of the partially calcined limestone, natural impurities in the stone, differences in crystallinity, grain boundary chemistry, density variations, and imperfections in the atomic lattice all play a significant role in

Jan 1, 1983

By AIME AIME

OUT of the fabulous iron ranges of Michigan?s Upper Peninsula since Pearl Harbor have come go to the steel mills to become tanks, guns, ships, and other weapons for a United Nations&apos; victory. But the contributions to the war effort, as far as Michigan&apos;s iron country is concerned, do not stop there. The same men who mine iron ore deep inside the earth also are "mining" on top of the ground, gleaning a harvest of scrap iron and steel that is writing a big chapter in the War Production Board&apos;s salvage program. At virtually every mine over an area of a hundred square miles, everyone from the top mine official and straw boss to the man in the dippings is scrap conscious. They know the importance of the ore they mine but they are equally familiar with the importance of iron and steel scrap in war production. The successful job they are doing in salvage is a tribute to the entire Upper Michigan mining industry and to the man who marshaled them into action-John M. Bush, chief of the land department for the Cleveland- Cliffs Iron Co. at Negaunee, and for ten years an A.I.M.E. member. Also, this job should be an inspiration to 611 mining. metallurgical, and petroleum communities as to the latent possibilities of organized scrap recovery.

Jan 1, 1943

By Homer E. Harris, William C. DeSieghardt, William A. Burgess

Under sponsorship of NIOSH, Eastern Associated Coal Corp., with the Harvard School of Public Health acting as a subcontractor, has determined for the first time the effective protection provided to working underground coal miners wearing approved half-mask dust respirators. This was done by conducting 187 man-shifts of in-mine testing in four different coal mines; included in this testing were 37 different test subjects representing 11 different job classifications and 5 different models of respirators. Presently available respirators on average provided significant protection levels to working miners even though on an intermittent use basis. However, "average" protection values were well below those achieved under laboratory conditions. Protection levels varied from man to man in a given work crew and from day to day for a given man. In addition, some of the factors affecting use and effectiveness of presently used respirators are discussed, as are areas in which improvements are needed, and the need to consider these improvements in context of a systems approach.

Jan 1, 1975

By A. C. Stoddard

Early in the present century, prospect-ing was active in the area of the present Miami district. There were plenty of blue and green copper outcroppings, but very little ore of a grade that would stand shipping costs had been uncovered. Late in the first decade of the century, tunnels were driven into the north and south slopes of the Inspiration ridge, and two of them exposed disseminated copper sulphide ore. This was the original discovery of such ore on the ground of what eventually became the Inspiration Division of the consolidated company. By 1910 exploration of the ground area was well along and by 1911 underground development had been started. In the next few years a large tonnage of disseminated copper ore had been proven— sufficient to justify the expenditure of several million dollars in mine development and for mine equipment plus large sums for treatment plants. The mine and treatment plants were placed in production July 1, 1915. To Jan. I, 1945, there had been produced from the mines of the Inspiration Consoli-dated Copper Co., more than 106,000,000 tons of ore. Nearly all of this tonnage had been recovered by block caving. GeologIcal and EconomIc FActors Block caving is a mining system based on the fact that if a mass of rock has a sufficient number of fractures and planes of weakness the mass will disintegrate if the support of an area of sufficient size is taken away—that is, "undercut." If the material that caves away from the bottom of a block is drawn off the spalling is progressive. There is a limit to the speed of this spalling or caving action, which varies with the structure of the rock being caved. If the rock is drawn at a rate faster than the caving rate, and if this drawing is continued too long, a void may be created that could make a very dangerous condition if the area should drop as a block and force the air below the uncaved rock out through the raises and drifts. This can be a very destructive force. On the other hand, if the broken material is not drawn fast enough the swell of the material in place to broken material would pack the mass until it was almost solid again and could not be drawn without much blasting, or perhaps even partially undercutting again. Geologically therefore it would seem that any rock with seams and fractures would cave; but for block caving there should be enough seams and fractures in a limited area so that such an area will cave and produce a product that can be drawn safely, rapidly enough and at a cost justified by the value of the product being drawn. At the Inspiration the disseminated ores occur in two formations, the Pinal schist and the Schultze granite. There is no material difference in the grade of the ore formed in the schist and in the granite. The chief copper minerals are chalcocite, malachite, azurite and chrysocolla. Other copper minerals occur in limited quantity.

Jan 1, 1946

By Rip Thompson

ALTHOUGH the metallurgical treatment for the Ophir Hill tailings was developed more than 20 years ago and in the interim a vast amount of experimental work was done with later-developed flotation rea-gents, it was found necessary to revert to the original oil reagents and their combina-tions with specific chemical reagents in order to obtain results of economic value. This is of especial interest because in present ore-treatment investigations later-developed flotation reagents are used almost exclusively and the coal-tar deriva-tives, except in certain patented reagents, are virtually neglected. These coal-tar oils and derivatives still have a definite field of application, especially in the treatment of some oxidized ores when modified sulphidi-zation is desirable. The Ophir Hill tailings deposit is in Ophir Canyon, Tooele County, Utah, about 55 miles southwest of Salt Lake City and 25 miles south of the Tooele smelter of the International Smelting and Refining Co. A road good for trucks leads directly from the Ophir mill to the smelter.

Jan 1, 1940

By Clarence Zener

The heat-treatment of steels will not pass from the stage of an art into that of a science until the mechanism of the phase transformations associated therewith is thoroughly understood. Such an understanding will involve two distinct types of inquiry: (I) the direction of the transformation, (2) the speed of the transformation. The first type of inquiry, which involves only the equilibrium relations between the various phases in steel, is the subject of the present and of a succeeding article; the second type, which involves the kinetics of transformations, will be the subject of a later article. In order that a theory of equilibrium relations may give useful information, certain experimental data must be put into the theory. It is customary for these data to be of a thermal nature. In the system discussed herein—steel—such thermal data are very scarce. In medium-alloy steels another type of data might possibly be used. In these steels the concentration of solute is so low that it may be possible to use the approximation of dilute solutions, an approximation that leads to linear relationships. The unknown functions, or constants, may then be determined in some cases from the binary iron-alloy system and in other cases from the ternary iron-carbon-alloy system. From the functions, or constants, so determined may then be computed the equilibrium relations in more complex medium-alloy steels. In the present article this second approach is used, the necessary experimental data &apos;being obtained from the simple binary and ternary equilibrium diagrams. Fundamental Equations In this article are derived the equilibrium relations between the gamma, alpha and cementite phases. In these three phases all important alloying elements except carbon form substitutional solutions, each alloying atom occupying a potential site for an iron atom. Carbon, on the other hand, forms an interstitial solution. In the face-centered cubic gamma phase, the interstitial positions are at the center of the unit cube and at the centers of the cube edges. There are therefore four interstitial positions per unit cell, or one per iron atom. In the body-centered cubic alpha phase, the interstitial positions are probably at the face centers, and also at the centers of the edges, which are crystallographically equivalent to the face centers. There are therefore six interstitial positions per unit cube, or three per iron atom. In cementite, (Fe, Alloy)3C, the carbon atoms may. be regarded as filling all the lattice positions of a given type. The introduction of the fundamental the of equilibrium has presented the author with a quandary. These equations are formally so similar to other equations that have been derived1,2 for related systems that they may appear to some readers

Jan 1, 1947