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By Leonard Obert

The structural stability of any mine or under- ground opening in rock is dependent on the stress field, that is, the state of stress in rock before mining, the stress distribution in the rock created by the opening, and the in situ strength of the rock. In the past mine design problems have been considered by assuming that the stress field is due only to the weight of the overlying rock, the stress around the opening can be calculated from elastic theory using laboratory-determined elastic constants, and the in situ strength of the rock can be determined from laboratory tests on small specimens. Solutions to hypothetical problems using this procedure are given in a report by Obert, Duvall, and Merrill.' Because of the uncertainties of these assumptions, this method can give only a rough approximation to the solution of actual structural problems. Obviously, this approach to determining the stability of underground openings would be greatly improved if the rock stress could be measured in situ, and it is undoubtedly for this reason that in recent years many investigators have spent considerable effort on the development of procedures for measuring rock stress. In this report a method is described for determining in situ the absolute stress in rock. The method requires the measurement of the deformation of a borehole before and after the rock is stress-relieved. The magnitude and direction of the applied stresses are calculated from the borehole deformation and modulus of elasticity of the rock. Also, the results of absolute stress determination made in the walls and pillars of underground openings in five rock types are presented. From these results a number of conclusions are drawn regarding the accuracy and limitations of this method and the problem of stress measurements in general.

Jan 8, 1962

By G. R. Lehman

The Inspiration Consolidated Copper Co. had an orebody at Miami, Ariz., of close to 100,000,000 tons of low-grade copper ore, and the method of mining this ore most profitably was of great importance. The selection of a method was practically limited to a "top-slicing," a "shrinkage-stope" or a "caving" method. The "top-slicing" method would give a high extraction of the developed ore, at a high mining cost, and the "shrinkage-stope" or "caving" methods a lower extraction of the developed ore, at a lower mining cost. Ore-Drawing Tests To decide on the method to be used it was necessary to know about what extraction of the ore could be obtained by the "shrinkage-stope" or " caving " methods. As no definite information regarding the,question was available at the time, C. E. Mills, the general manager, thought that some information could be obtained by experimenting in drawing ore, covered with capping, from an experimental box. Some work had already been done along these lines by W. C. Browning for the Inspiration Copper Co. and by myself for the Live Oak Development Co. The idea was to represent as nearly as possible, in the experimental box, the conditions within an area of caved stopes of caved ore all ready for drawing. That is, the area was supposed to represent a semibroken mass with the capping above it in the same condition and ready to follow the ore downward as it was drawn out of the chutes under the ore. To represent the above condition, in the experimental box, crushed ore from the mine was placed in it to a given height, and red barren capping from the mine was placed on top of the ore. The Experimental Box The experimental box shown in Fig. 1 was made of wood and glass. The glass was used for the sides so that the drawing action of the outside row of chutes could be seen and noted, the latter being cut in the center by the glass sides. The length of the box was 30 in., width 20 in. and the

Jan 1, 1917

As already said Pattin's map and the later one of Evans' showed coal in several places in Ohio as early as 1750, and possibly 1748; the reference on the latter map was' to an exposure near Bolivar, in Tuscarawas County, as well as along the Hocking River. So far. as now known, it 'was not mined in either place until 1810. George Croghan, in descending the Ohio with his party in 1765, mentions an "Alum Hill" which they saw near the present site of Pomeroy, probably an exposure of saline deposits, but does not mention coal. As settlement north of the Ohio River was prohibited until 1787, no coal was mined until long after that date. In 1785 a survey of seven ranges in the Ohio country was made, the line running west from a point on the north bank of 'the Ohio River, due north of the western termination of the southern boundary of Pennsylvania. The surveyors noted, "from hence to Stoney Brook between two very steep and high Ridges; it is eight yards wide, its bottom is of Slate and Sand Stone, and in many parts of it are large pieces of excellent Coal washed by, the Rains from the Neighboring Hills."' This was the present Yellow Creek, and the coal was from some of the lower measures. The Scioto Company published a pamphlet in French in 1787, to promote the sale of their lands and emigration to them, in which was said,

Jan 1, 1942

By L. J. Klinkenberg

It is pointed out that the current concept of pore size distribution is not unequivocally defined and that different methods aiming at a determination of such a distribution therefore do not lead to the same results. A pore size distribution should not be based on the idea that a core should, under all circumstances, behave as a bundle of straight non-interconnected capillaries of the same pore size distribution. This is illustrated by calculations and experiments on the displacement of miscible liquids. INTRODUCTION The introduction of the concept of pore size distribution has been an attempt to characterize the intricate geometry of the flow channels in porous media. As pores in a porous medium are interconnected it is impossible to describe exactly what is meant by a "pore" and, therefore, the term pore size distribution requires further amplification. In the visual method for the determination of pore size distribution "the pore" is considered to be the hole between the grains as observed on thin sections or on a polished surface of the rock under a microscope. In all other presently known methods,1,2 a displacement process is studied and it is ascertained what as- semblaae of straight cylindrical capillaries would show the same behavior. The distribution of the capillary diameters of this assemblage is said to represent the size distribution of the pores of the actual porous medium. From the foregoing it is already apparent that it is useless to try to decide which process or which method of investigation leads to a "correct" pore size distribution. To illustrate this further a displacement process in which a fluid is displaced by another miscible with it will be discussed and the results will be interpreted in terms of a pore size distribution. DISPLACEMENT EXPERIMENTS WITH MISCIBLE LIQUIDS OF NEARLY IDENTICAL VISCOSITY AND DENSITY Interpretation in the Form of a Pore Size Distribution If distilled water is displaced from a homogeneous unconsolidated sand pack by, for instance, a dilute solution of NaCI, the breakthrough recovery i.e., the amount of distilled water produced at the moment the first trace of NaCl can be detected in the effluent water, is between 95 and 100 per cent of the pore volume of the pack. This result can be understood by following in imagination the course of one particle of the liquid. Imagine a length, ?l, at the end of which a liquid particle has an independent chance of a renewed choice of pores of different diameters. In other words, the particle has a choice of traveling time, at, for any length ?l; instead

Jan 1, 1958

By Robert Mehl

METALLURGISTS are properly interested in papers dealing with subjects ranging from the theories of the metallic state to very practical details on the use of metals. A review of theoretical metallurgy naturally excludes papers concerned with the usefulness of metals and limits itself to those concerned purely with the science of metals. Even in this more limited field the reviewer is confronted with thousands of papers dealing with facts and theories of metallic behavior, from which he can select only a few hundred. The selection is necessarily highly arbitrary. Certain classes of papers definitely fall within the scope of this review. Thus, papers on the deformation of metals, on the structure of alloys, on recrystallization, to select only a few, are fully represented. Other subjects, which verge on what is generally accepted as the science of metals, such as the magnetic properties of metals, the less familiar electrical properties and theories, adsorption of gases by metal surfaces, and the like, are treated scantily. Particular attention is given to reviews of subjects that fall with in the groups chosen; in a summary such as this, which is largely in the nature of a progress report, capably written reviews are of importance, particularly since the monograph and text book literature is so meager in this field.

Jan 1, 1935

By A. W. McReynolds

One characteristic of plastic deformation which distinguishes it from elastic strain is the essential inhomo-geneity of plastic strains. Elastic strain varies continuously through a material, and average relative displacements of initially adjacent atoms are only small fractions of their initial spacing, (strains of the order of 0.01 or less). On the other hand, plastic flow corresponds to the appearance of discontinuities in strain of the lattice, such as dislocations or slip bands, where local strain, on an atomic scale, is several orders of magnitude higher. These discontinuities are visible on a microscopic scale as the familiar slip lines (Fig 1). In spite of this obvious microscopic inhomogeneity, however, macroscopic measurements almost invariably show a smooth curve of stress vs. strain (Fig 2b) even if measurements of linear strains be made to an accuracy of one part in 107. This macroscopic homogeneity of strain indicates that the discontinuities in strain on slip planes occur in increments too small or too slow to be recorded individually, and further that they occur sufficiently independent of one another so that the small increments add at random to a smooth stress-strain curve. The present paper describes observations of plastic strain in aluminum of commercial purity and in high purity Al-Cu alloys, where there exists a strong coupling between slip in various regions of the specimen such that once initiated it spreads rapidly through a large volume. The total effect is that of relatively large, rapid, and regularly spaced steps of strain followed by periods of only elastic strain. Fig 2a illustrates the type of "stair-step" stress-strain curve which results. The properties of this cooperative slip phenomenon will be described further in the section on results: in par- ticular it will be shown that each step corresponds to the propagation of a wave of plastic deformation through the specimen. Some interpretations of the mechanism by which it occurs will be made in the following section. Although the type of plastic wave phenomena to be described has not previously been reported, there are numerous cases of related effects in the plastic yielding of metals: YIELD POINT PHENOMENA The most familiar of such effects is the "yield point" observed in low carbon steels, brass, duralurninum, and the like. It consists in the sudden termination of the elastic portion of the stress-strain curve by a large plastic strain. Since the usual tensile machine is such that yielding of the specimen relieves the load, the resulting curve is as shown in Fig 3. As the strain continues, deformation occurs at a lower stress for some time, then follows a rising curve, but with no further sudden yielding. This effect has been observed in brass by Sachs and Shojil and later by many others. Edwards, Phillips and Jones2 made extensive studies of the effect in steel, and of the role of various alloying elements. Although there seems to be fairly clear evidence that the yield point is caused by a hardening of the material by precipitation of impurities, no satisfactory explanation for the sudden yielding has been given. Winlock and Leiter3 have shown that the strain. level of the upper yield point depends strongly on the rate of loading, the yield point increasing by almost a fac- tor of two as the strain rate goes from 0.002 in. per in. per min. to 4.4 in. per in. per min. This effect would seem to imply an incubation period before yielding is initiated at a certain stress. On the other hand, by going to very slow loading rates, Edwards, Phillips and Jones2 showed that the yield point does not become lower and eventually disappear as might be expected, but, on the contrary, begins to rise at loading rates below about 25 Ib per in. per min. becoming much higher than at rapid loading rates. STRAIN AGING If, instead of continuing straining of a specimen after occurrence of a yield point, the load is removed and the specimen aged, resumption of the test results in occurrence of another yield point as shown by the dotted curve of Fig 3. The new yield stress is generally higher than the previous maximum applied stress. This hardening of the material by straining and subsequent aging is undoubtedly related to quench age-hardening resulting from the aging of a specimen quenched from high temperature. Since neither effect is observed in pure metals, it is generally accepted that quench-aging in all cases is the result of hardening by precipitation of a supersaturated alloying element, and that strain-aging is probably a similar precipitation, accelerated by disruptions of the lattice by previous strain. Pfeil4 has shown that strain-aging does not occur in iron from which all of the carbon has been removed, but that only a very small carbon content, around 0.003 pct, is necessary to cause strain-aging. In accord with this observation is recent work by Dijkstra5 in this laboratory showing that the solubility limit of carbon in iron is extremely low, less than 0.001 pct at 400°C. Edwards, Phillips and Jones2 have shown that the strain-aging effect is also removed by the addition of small quantities of elements such as Mo, Mn, Ti, and the like, which readily form carbides. Their results demonstrate the

Jan 1, 1950

By L. P. Teas

In spite of the influx of operators into the Gulf Coast anxious to retrieve their depleted production in other fields, and in spite of very active application of the most scientific geophysical methods to locate new producing areas, the results have been very discouraging and the year has failed to produce more than the average results for a Gulf Coast year. During the year seven new oil fields, some of which are still of very little importance, and one new gas area have been discovered. These fields are Tom Ball, Greta, Cleveland, Raisin and Garwood in Colorado County; Louise and Premont in Jim Wells County, and the new producing gas area near Ace in southern Polk County. During the year salt has been found for the first time at Carlos and Esperson. New producing areas have been developed on East Stratton Ridge, Hockley, Hull, Port Neches, near Pettus in Bee County, and on the O'Connor Ranch in Victoria County. The total production for the Gulf Coast for the year was 62,837,435 bbl., an increase of 18,589,000 bbl. over 1932. During the year, 1307 wells have been drilled of which 207 were wildcats, compared with 653 wells and 141 wildcats the previous year. The total daily production at the end of the year was 165,201 bbl. At present there are 3100 oil wells producing. The average production per well is 55.5 bbl. per day. The price of crude fluctuated considerably during the year, beginning at 80c per barrel and closing the year at $1.04 per barrel. Completion data for 1933 are as follows:

Jan 1, 1934

By C. E. Jr. Reistle

ALL crude oils become more viscous when chilled, but the only oils that congeal and precipitate paraffin to such an extent as actually to cause production troubles are those that contain an appreciable amount of wax. In handling these oils of high wax content, three distinct problems may be encountered before the oil reaches the refinery. The first problem is the precipitation and accumulation of paraffin in the well, either in the oil string or on the face and in the pores of the sand. The second problem is the accumulation of paraffin and the congealing of oil in the transportation lines. The third problem is the precipitation of paraffin and the formation of tank bottoms.

Jan 1, 1927

By Richard L. Ash

7.3-1. Introduction. All phases of mining competent materials are affected directly by the results achieved from primary blasts. It is imperative that their design suit each particular set of mining conditions. In general, the round design must provide an adequate tonnage of material, properly placed with suitable fragmentation, to ensure that loading, haulage, and subsequent disposal or processing are accomplished at the lowest possible cost. Blasting rounds are designed by the proper application of cratering relationships developed for the single, concentric, confined explosive charge. Blasting for surface mining and most open-cut heavy construction, however, is characterized by the use of rounds, composed of a number of explosive charges with relatively long lengths, which are placed in benches with specific finite dimensions. Therefore, modifications must be made to the classical, single point-charge cratering concepts. It is the purpose of this discussion to outline the basic principles, significant variables, and procedures for their integration in the design of rounds that are applicable to conditions characteristic of surface mining. Because relatively insensitive blasting agents will be used in most instances, particular attention must be given to priming, control of confinement, and selection of charge diameters that ensure complete explosive-reaction execution. 7.3-2. General Considerations. The primary requisites for any blasting round are that it ensure optimum results for existing operating conditions, possess adequate flexibility, and be relatively simple to employ. It is important that the relative arrangement of blastholes within a round be properly balanced to take advantage of the energy released by the explosives and the specific properties of the materials being blasted. There are also environ- mental and operational factors peculiar to each mine that will limit the choice of blasting patterns.

Jan 1, 1968

By Charles A. Ashburner

At the Philadelphia meeting of the Institute, held in February, 1881,I had the honor of reading a paper on "A New Method of Mapping the Anthracite Coal Fields of Pennsylvania."* At that time the State appropriation for the Second Geological Survey had just expired, and, as a new appropriation was not assured, no detailed plan had been adopted by Professor Lesley, State Geologist, for the practical examination of the mines, and the solution of the geological structure of special localities, or the representation in sections, vertical and columnar, of the general structure of the coal basins and coal beds. I had merely proposed a plan of mapping, as the material for the construction of maps was most available, and it was at that time uncertain what money the Survey would have to enable it to extend the surface and underground explorations, in order to make the examinations complete. After a continuation of the Survey was authorized until January, 1884, by the legislature, in May, 1881, the Anthracite Survey was regularly organized, and a plan adopted for a systematic and exhaustive geological and mine examination of the region. This plan provided for such work, other than that of mapping, as was necessary for a complete and practical geological and mining survey of a coal field. To do any geological work, of however general a character, it was absolutely. necessary that the members of the Survey Corps should obtain unrestricted access to all the mining records of the operators, which have been made with great care and accuracy and at an enormous expense during the past thirty years and more. The unanimous and generous support of the individual and corporate coal operators, of the plan of carrying on the Survey, was promptly assured, on condition that the results should be of such a character as to render them of practical utility to the property-owners and those directly interested. It was hoped

Jan 1, 1883

By E. C. Harder

AT a Meeting of the New York Section, on May 23, 1918, the sole subject of discussion was the nature and occurrence of iron ores in certain parts of the world.? Owing to the importance of this subject, it has been deemed' advisable to publish the remarks made at that meeting in the form of a paper, for presentation at the Milwaukee Meeting, instead of in the usual place, under News of Local Sections. The remarks related to the following districts: Brazil, by E. C. Harder, of the U. S. Geological Survey; Scandinavia, by Waldemar Lindgren, of the U. S. Geological Survey; Cuba, by C. M. Weld, of the U. S. Bureau 'of Mines; Southern Europe, by A. C. Spencer, of the U. S. Geological Survey; China, by H. Foster Bain, of the U. S. Bureau of Mines; Alsace-Lorraine, by Sidney Paige, of the U. S. Geological Survey. BRAZIL By E. C. Harder During the years immediately preceding the war, the iron ores of Brazil were attracting the attention of iron operators both in Europe and in the United States. This was clue to the large quantities of practically undeveloped ore available, and to its great purity. It is reasonably safe to state that had capital not been diverted from the exploitation of these deposits to war purposes, Brazilian iron ores would probably now be offered in European and American markets. It is certain that after the war these ores will play a prominent part in the economic reconstruction of Europe and perhaps in the development of America.

Jan 9, 1918

By Fred Bond

This paper is a continuation of two earlier papers,1,2 and presents new data on the grindability of various ores and other materials-the results of several years of intermittent research work on the nature of grinding and interpretation of test results. It is divided into five parts: 1. The tabulated results of several hundred grindability tests on a wide variety of ores. 2. A method of correcting screen analyses and calculating from them the surface and other properties. 3. A description of a. new method of measuring the "surface energy" of in ore by pendulum impact tests. 4. Test results. 5. A general discussion of the test results and their application to grinding problems.

Jan 1, 1938

By J. Walter Snavely

PRESENT-DAY processing in many industries, calcining, sintering, briquetting, beneficiation and nodulizing, increasingly calls for the handling of large volumes of hot bulk materials. Various types of conveyors have been employed. This discussion will cover the factors governing their selection. For temperature ranges up to 400°F, or approximately 200°C, a wide range of conveyors is available. Special constructions of rubber conveyor belts. steel conveyor belts, vibrating and shaker conveyors, apron conveyors, and drag chain conveyors, all are used successfully. As temperatures go well above 400°F, however, choice of conveyors is narrowly limited. This paper will consider the problem of handling bulk materials only where the temperatures exceed 400°F.

Jan 5, 1953

By Arnold S. Epstein

Tlze green electroluminescence occurring at liquid-nitvogen temperature in epitaxial gallium phosphide diodes is exarnined using the donor dopants silicon and sulfur. Zinc is used as the p-type diffusant. Two tt~ain peaks are found, namely til 0.56 and 0.535 p. The intensity of the gYeen peak occurring at 0.56 is found to oary as -4"' wlzere Jf is the forward current density and to first order appears to be dependent on the concet~tvation of ionized donovs. Tile vadintive lifetinze fov this process is -10-'sec. The intensity of the 0.56-p lu~ninescence is nt least several ovdevs of magnitude greate,, at liquid-nitvogen temperature than that noted jor the 0.538 radiation for current densities up to about 35 amp per sq cm. The variation oj- the intensity of. the 0.538-p peak with current density caries according to the donor dopant. With sulfur as the donor one has a J12 dependence, whereas when silicon is the donov a J1.5 dependence is noted. Tl~e above can be fitted to a In molecular process (in first order) such as a band to band recombination. The constant B fir band to band vecombination) is found from our experitt~etlt to be of the order of 2 CZI cm per sec, zcl~ereas for tlze impurity vecombination peak (0.56 p]) tile A cotzstor~t is of the order of. 7 x 10-' cu cm per sec. The structuve o/. the diodes at liquid-nitvog-en tett~peruture is oj tlze double injection type, and by carefi~lly selecting. the thickness of the structure one can regulate the onset of the 0.538-p radiation. The diode clzavaclevistics follow an I-Vx laiv where x is >1. Llregatiue resistance in these structures con be correlated with saturation of tlze 0.56- peak. ThE development of high-purity, large single crystals of epitaxially grown gallium phosphide is the ultimate aim of the studies to be reported. While a number of papers and reviews' have been presented on properties of gallium phosphide grown from gallium solution and from the melt, less attention has been paid to the properties of epitaxial gallium phosphide grown from the vapor. In the studies to be reported we have examined the effects of shallow donor impurities, primarily silicon and sulfur, at liquid-nitrogen temperature, on both the electrical and green electroluminescent properties of carefully characterized single-crystal epitaxial Gap. I) EXPERIMENTAL PROCEDURES A) Material Preparation and Properties. The samules used in this investigation were single-crystal n-type epitaxial gallium phosphide. he single crystals were synthesized from the elements by vapor transport and epitaxial deposition on single-crystal gallium arsenide substrates. Typical transport agents used were chlorides. The growth procedures are described in more detail in Ref. 2. The samples were grown in the (111) orientation and had thicknesses up to 480 . Following the growth, the GaAs substrate was removed from the epitaxial Gap by etching in nitric acid. The Hall effect and resistivity of these n-type samples were measured as a function of temperature and analyzed for impurity content and compared with spectroscopic emission analysis. The results are given in greater detail in Ref. 3 but a summary is noted in Table I. In Table I, AED denotes the donor ionization energy, Nd is the donor impurity concentration, lvA is the acceptor impurity concentration, NI is the total impurity concentration, Rip vs temperature is the measured Hall mobility-temperature relationship from liquid nitrogen to about 400"K, n(77"K) is the measured carrier concentration at liquid nitrogen, and R/p(77'~) is the measured Hall mobility at liquid nitrogen. Good agreement is noted between electrical and emission analysis for the major donor impurity, silicon, in the two materials where it is a major constituent. In the case of the two samples SC90-6 and AP138-3(111) B which were sulfur-doped the ionization energy found from the electrical data is in good agreement with that reported for sulfur.4 The acceptor impurities are not known, although from the presence of magnesium in the samples as indicated by emission analysis and its known role as an acceptor in GaP,4 magnesium could be present as an acceptor. Similarly, since silicon is known to be an amphoteric impurity4 it may also be present as an acceptor in the Gap.* The *A small band has been noted at 0.625 11 in samples SC90-6, SC76-4, and SC77-4, suggesting according to Ref. 5 that sillcon could be present as an acceptor In these samples since these authors have found this peak to represent a donor-silicon emission. presence of calcium deduced from emission analysis is not correlatable with the electrical analysis and its presence as an electrically active impurity should be questioned. B) Sample Preparation and Diode Fabrication. The original slices were of the order of 2 sq cm in area witi the (111)B face up. The material was cleaved and sectioned and the best pieces selected (i.e., those which visually appeared to have the least strain and defects). The samples were polished, lightly etched, and cleaned in trichloroethylene. Zinc was diffused in a closed tube at 800°C to form a p-n junction. Diodes were made from these samples. The depth of junction varied, but did not exceed 10 p depth. The back side of the slice was lapped back and a low-resistance n-type contact was formed (at 600°C in forming gas) to an Au-Mo tab with a hole in the middle for

Jan 1, 1968

By Frank C. Aplleyard

The two calcium sulfate minerals-gypsum and anhydrite-occur in many parts of the world, and gypsum has long been of economic importance in the family of industrial minerals. Gypsum, the dihydrate form of calcium sulfate (CaSO4•2H2O) and anhydrite, the anhydrous form (CaSO4) are frequently found in close association, and it is seldom that a calcium sulfate deposit will consist exclusively of one mineral or the other. Although known gypsum deposits are extensive, anhydrite makes up the largest part of total calcium sulfate reserves. However, it has very minor economic use, and most of the following discussion will be devoted to gypsum. Calcium sulfate is one of the principal constituents of evaporite deposits, and when pure, has the following composition: [Sulfur Combined Lime Trioxide Water (CaO) (SO,) (H2O) Gypsum 32.6% 46.5% 20.9% Anhydrite 41.2% 58.8% -] Deposits of pure gypsum or of pure anhydrite which are large enough to be considered commercial have never been found because of both the metastable relationship between the two minerals, and the presence of impurities such as calcium or magnesium carbonates, chlorides, other sulfate minerals, clay minerals, or silica. As a result most mine production of gypsum will range between 85 and 95% pure. Often it is used as mined, although in certain cases, one or more forms of mineral beneficiation are employed to upgrade the product. End Uses The largest use for gypsum is based upon the unique property which calcium sulfate has of readily giving up, or taking on, water of crystallization. With the application of a moderate amount of heat in a process known as calcining, gypsum is converted to plaster of paris (the hemihydrate of calcium sulfate, CaSO4 ½ H2O) which when mixed with water will set or harden as the calcium sulfate returns to the dihydrate form. This semifinished product, usually called stucco, is then manufactured into a large variety of plasters, wallboard, and block for construction use, or into plasters for industrial applications. About 75% of the gypsum used in the United States is calcined for these purposes. Uncalcined uses of gypsum are principally as a retarder for portland cement, as a soil conditioner, as a mineral filler, and other minor industrial applications. About 25% of the gypsum mined in the United States goes into these markets; however, in less developed countries where construction and other industrial uses may be quite limited, the use of uncalcined gypsum for portland cement retarder may well be the dominant-if not the only-market for the mineral. It has often been noted that calcium sulfate constitutes the world's largest reserve of sulfur, and minor use of both anhydrite and gypsum has been made to produce sulfuric acid or other sulfur compounds such as ammonium sulfate. However, because sulfur is readily available at lower cost from other sources, use of calcium sulfate has been limited to only a few locations where it could compete economically. No such use is reported in the United States at this time. Mineralogy Anhydrite, CaSO4 because of its geologically rapid conversion to gypsum, and relatively high solubility (about 0.2 g per 100 g H2O) is not often found outcropping in climates wet enough to support abundant vegetation except on steeply dipping slopes or other places where hydrated material is continuously removed. Anhydrite rock is most often light to bluish gray in color, and under the microscope, varies

Jan 1, 1983

By Arne Westgren

ONLY in exceptional cases can the ordinary methods of chemistry be used for determining the constitution of compound metallic substances. Recourse has therefore been taken to special methods, the main expedients of which are, as we know, thermal analysis and metal microscopy. To these may be added-though more accessory-the determination of electric conductivity, specific volume, hardness or other properties. The information obtained by these methods has been compiled in equilibrium diagrams. Naturally, the technically most important alloys, such as steel, bronze and some others, have been subjected to very close study, and many investigators have devoted themselves to the solving of their problems of constitution. The equilibrium diagrams of these systems are therefore known today with a comparatively high degree of accuracy, even though it must be admitted that many details regarding their transformation reactions still remain to be completely explained. The equilibrium diagrams of the other alloys as a rule have not been determined so accurately. Most of them are based only on approximate determinations of the homogeneity ranges of the various phases. Thus extensive, detailed studies remain before these diagrams may be considered as established. Unfortunately, it must also be admitted that many of the alloy diagrams given in the present handbooks are as a whole very dubious. As a matter of fact, many of them may really only be viewed as the results of rather superficial, orientating investigations. In fact, there also seems to be a general opinion prevailing in our day that much work still remains to be done before the equilibrium conditions of the alloys may be considered as fully explained. At present, in almost all institutes for research on metals, as well as in many university laboratories, investigations to this effect are being carried out. As a rule, the classical methods of metallography, the thermal analysis and metal microscopy are applied.

Jan 1, 1931

By Frank Firmstone

When in charge of the Glen don Iron Works, the importance of good methods of filling was forcibly brought to my attention, and it occurred to me that the first step toward the discovery of the best plans was the accumulation of exact information as to the distribution actually effected by various chargers; also, that something could be done in this direction by careful measurements in the furnace, to be afterwards recorded for comparison on drawings. The figures shown herewith have been prepared from such measurements, and nearly all of them refer to Glendon, where the fuel used was anthracite and the ore-mixture about threequarters of New Jersey magnetic ores and one-quarter of brown-ores from the vicinity of the works. Every occasion furnished by the blowing-in of furnaces was utilized, but the data accumulated rather slowly in this way; and, opportunity oEering to make special trials at no great expense, the figures from 2 to 7 were thus obtained. The trials were made by dumping a hopperful (6 barrows) of material at once into the furnace, and, when all the fuel of a round (12 barrows) had been put in, the profile of the upper surface was obtained by stretching a steel tape across the top on a diameter and at a known height. By measuring down from this with a graduated rod, the profile was easily obtained with sufficient accuracy, especial pains being taken to get correctly the crests of the ridges and the bottoms of the hollows, as many intermediate points being included as seemed necessary. This was repeated on another diameter when there was occasion. The same course was followed for the limestone and ore.

Jan 1, 1899

By Frank Tolonen

IRON-ORE beneficiation is becoming of vital importance to the Lake Superior region, since only a few decades will be needed to exhaust the direct shipping ores even if generous allowances are made for discoveries of new orebodies. If the region is to continue as the chief source of ore to the steel industry of the United States, it must concentrate or otherwise beneficiate the enormous tonnages of available iron formations. A beginning along this line has already been made. About one-fifth of the total shipment, even now, is the product of some sort of concentrating process, while another fifth is improved in physical structure by crushing, screening, drying, sintering, or some other similar method. The amount of material amenable to these processes is limited, however; and, in order to be able to utilize the billions of tons of iron formations that cannot be so beneficiated, an intensive study of their nature and concentration possi-bilities is necessary. As long as high-grade ores are available in ample quantities, ore dressing is economically impossible, but as soon as the supply nears exhaustion it becomes necessary. At first the products of ore dressing must meet as nearly as possible the same specifications as the rich ores in order to be adapted to the reduction processes already established. The future requirements as to quality will depend on the one hand upon the ability of the ore dresser to eliminate undesired constituents and charac-teristics in the material, and on the other upon the adaptation of the reduction processes to the product that can be economically supplied. A better understanding of the blast furnace and other reduction reactions, and improvements in the preparation of raw materials, should enable the Michigan districts to continue to supply ore for a long time to come. The study and testing of the iron formations necessary to bring a utilization of the low-grade ores, though requiring time and effort on the part of all concerned, should not be postponed, especially since the economic situation forces the use of the highest grade ore in preference to the leaner material.

Jan 1, 1933

By J. E. Johnson

The general construction of blast-furnaces has undergone no radical change in more than a generation. When the old style of masonry construction was replaced by the steel shell, the masonry piers were simultaneously replaced by columns, never lese than 6 and frequently 12 or 16 in number, set under the mantle-ring. These columns were at first unvaryingly made of cast-iron, but in more recent years have frequently been made of structural steel. The furnace itself has recently been the subject of radical changes; in some cases the thin-lined construction has been adopted for the whole furnace, and in other cases it has been adopted for a zone immediately above the bosh, raising the mantle several feet to make this possible, but still the style of construction with columns set immediately under the mantle has been universally followed. In spite of the apparent fixity of this type of construction it is open to grave disadvantages from the operating point of view, which may be briefly outlined as follows: The slope of the bosh and size of the crucible are such as to leave scant room inside the columns for the necessary water-piping, etc. The bustle-pipe must necessarily be outside the columns and the penstocks have to pass between them, with the result that the columns are frequently much in the way when changing the tuyeres or otherwise handling the penstocks. Moreover, the hearth-jacket requires a diameter but little smaller than the circle of the inside of the columns, and as a result the cooling-water ditch for protection against breakouts is exceedingly limited in width. As a consequence of these conditions, when any work requires to be done around the furnace, such as changing a tuyere or working on the cooling-water pipes, the amount of room left between the columns, pen-

Jan 1, 1913

By Larry Kaufman, Morris Cohen

THE solid phase equilibria' and the martensitic transformation in the iron-nickel system have been the subject of considerable study. In addition, there have been numerous investigations on the calorimetric and thermodynamic properties of iron-nickel alloys. The purpose of the present work is to extend the existing information concerning the martensitic reaction in the iron-nickel system, and to develop a general thermodynamic treatment which will encompass the equilibrium and non-equilibrium phase

Jan 1, 1957