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By Isobel Clark

The increasing complexity of modern mining technology makes it ever more difficult to decide on the 'best* way to solve problems in mine planning. Yet with escalating costs it becomes increasingly more important for the mining engineer to be able to evaluate quantitatively the implications of the 'what happens if' postulation on the efficiency and economics of exploitation. The use of a model of the orebody can yield an estimate, not just of overall expected results, but also of the sensitivity of these results to possible variations in the orebody. Estimation techniques, such as Kriging, will produce the expected value for the grade of ore at any given point, or over any given volume within a deposit. However, the actual grades mined during production will - of necessity - differ from the predicted values. These possible variations, and the sensitivity of the management decisions to them, can be investigated in detail by the use of simulation. An orebody can be simulated which follows the known characteristics of the deposit at any given stage in development. These properties might be the histogram of grade values, the semivariogram from the samples, the actual borehole assays, geological constraints and/or interpretation, topography, lease boundaries etc. This would be one possible 'realisation' of the deposit as dictated by the currently known data. If several of these simulations are carried out, each conditioned to the current knowledge of the orebody, then it is possible to gain an idea of the range of possible outcomes of any mining procedure or decision taken - all of which are equally likely. Not only can the best decision then be taken, but its sensitivity to the inherent variation within the orebody, and to the ever present estimation errors may be thoroughly studied.

Jan 1, 1977

By John E. Sweet

There have already been so many subjects of a purely mechanical nature presented to the Institute of Mining Engineers, that it is unnecessary for me to apologize for adding another to the list. When a new invention, or what is supposed to be a new invention, claiming simply an improvement on the well-known devices, is to be described, it is usual to point out the defects of the old and give a history of the object or the art up to date. But, as no doubt a large proportion of the members of this Institute know as much, or more, about the history and use of the steam-engine indicator than I do myself, I will not further preface the subject, than to remind you that what called for the Richards's improvement on the Watt's indicator was high speed; that the leading improvement was the reduction of momentum in the reciprocating parts; and that this was accomplished by making the parts lighter, and reducing the travel of the heaviest, of them, and consequently the speed and momentum. The use of the indicator has been extended, for the speed of steamengines and other prime movers has been increased, until one engineer at least, John Cooper, of Philadelphia, says, "I want an indicator that will work up to a thousand revolutions." .Mr. Thompson, of the Buckeye Steam-Engine Company, of Salem, Ohio, has improved on the Richards's indicator by another reduction in the momentum, which is done by putting the parallel motion nearer the fulcrum of the pencil arm, reducing both weight and travel. The characteristic feature of the indicator I am going to illustrate is a still further reduction in the same direction, which is accomplished by dispensing with the parallel motion altogether. As is often the. case, in putting a simple idea into shape, some difficulties

Jan 1, 1879

By H. l. Burghoff, A. I. Blank

J. J. Kanter.*—The authors of this paper have demonstrated that at 500°F their alloy will elongate, under appropriately adjusted stress, one or two per cent over a period of 6000 hr. Then they show that after the alloy has so elongated, it will still elongate anothcr 40 per cent if it is tested at ordinary temperature. I should like to ask the authors how much more than 2 per cent over a period of 6000 hr. their alloy will elongate at 500°F. H. L. BuRghofE.—We do not know, because we have not carried out stress-rupture tests on this material. I believe your point concerning the desirability of stress-rupture testing is very well taken. In the material that we have subsequently tested we have not seen any signs of deterioration. We do not know how much further it is possible to go beyond the 2 per cent before finding grain-boundary separation. We have not encountered any under the conditions of the test. W. E. Kingston.†—IS this particular type of copper susceptible to strain-aging, and if so at those comparatively low temperatures, is that going to affect the shape of the curve? By strain-aging I mean the phenomena that certain ferrous alloys show in which the resistance to deformation increases suddenly during the low-temperature creep cycle, apparently due to some precipitation type of reaction, perhaps analogous to hydrogen embrittlement. H. L. BUrghoff.—I believe that this material is not subject to strain-aging of this type. It is very high in copper content, of course, nearly loo per cent. There are some very minor impurities and it carries a small amount of phosphorus, which, unless it is present as an oxide, should be in solid solution well within the solubility limits. I believe it does not precipitate

Jan 1, 1945

By Henry Hibbard

THE process of making washed metal now followed is in principle that described by Holley before this Institute in 1879, as the Krupp washing process. Sir Lowthian Bell also experimented extensively in England during 1877 and 1878 on refining iron and joined his interest with Krupp, the process being often referred to as the Bell-Krupp process. The only plant in this country now operating this process is that of the Brier Hill Steel Co., Youngstown, Ohio. This process may be considered as the sole survivor of the numerous methods conceived for refining crude iron, when the removal of phosphorus from steel-making material was the great desideratum affecting large districts. The east coast of England and all northern Germany, the homes of Bell and Krupp, respectively, could at that time make steel only from imported ores. These processes were in use or in various stages of development 40 years ago and all except the Bell-Krupp received their quietus from the development of the basic steel processes, both pneumatic and open hearth. The aim of the early refining processes was, first, the removal of the silicon; which could be clone on a sand bottom, and later, the removal of the phosphorus, requiring a bottom which would give or permit a basic slag. The incidental advantages of increased yield and small fuel consumption were not generally recognized or considered; the aim of the later. operations was the saving of the difference in value between low and high phosphorus irons, as well as hastening the removal of the metalloids. The chemistry of the washing process follows in part that of the puddling process, and indeed washing might, be considered as the first half of puddling, since all the non-ferrous elements of the crude iron, except the carbon, are eliminated and the iron is maintained molten until cast. In puddling, the iron loses its carbon as well, and because of that, its fusion point rises above the hearth temperature; it freezes into a pasty malleable form, and is worked at once by squeezer, hammer, or rolls.

Jan 12, 1915

By Cyril Stanley Smith

Jan 1, 1949

By Cyril Stanley Smith

Jan 1, 1949

By Noel H. Stearn

OF the many instruments devised for the measurement of magnetic anomalies, the ordinary dip needle, by virtue of its superior simplicity of construction, facility of manipulation, and definiteness of interpretation, seems to merit serious attention as the instrument most readily applicable to the detection of magnetic anomalies of the higher order of magnitude. In spite of the fact that it has been used for many years for the discovery of iron ore in Europe and in the Lake Superior region of America, its capabilities as a geological instrument have not yet been thoroughly plumbed. The Wisconsin Geological Survey, under Dr. W. 0. Hotchkiss, E. F. Bean, and H. R. Aldrich, has been most thorough in developing the technique of the instrument, and the results it has obtained have aroused a general interest in a more widespread use of geomagnetics as an exploration method and the dip needle as a geological instrument. The simplicity of the instrument is an especial advantage, as it can be used by anyone, regardless of his technical training; but to insure useful results not only is a knowledge of the background of geomagnetics necessary but also an understanding of the principles of the instrument itself. Principles of the Dip Needle The major feature of the dip needle is an elongated magnet suspended with fixed bearings in such a way that it can move in a single plane. If the point of suspension were exactly at the center of gravity of the magnet, the instrument would be identical with the "dip circle" or "dipping needle" of terrestrial magneticists, and as such could be used to determine variations in the inclination of the earth's magnetic field when observed in the plane of the magnetic meridian. The dip needle, however, differs from the "dip circle" or "dipping needle" in having an adjustable counterweight affixed to one end of the magnet. This counterweight serves to balance the magnet at an angle to the inclination of the earth's field when the instrument is oriented in the plane of magnetic

Jan 1, 1929

By E. P. Haqyes, J. K. Butler

011, and gas development has continued unabated on the Texas Gulf Coast during 1937. Although the number of important new discoveries has not been great, the extensions in older fields, owing to discovery of new sands and the lateral extension of known sands, has been extensive. Twenty-four new producing fields were added during the year, and many of these areas give promise of developing into important producing districts in the future. Alta Mesa, Amelia, Aransas, Clara Driscoll, Five Corners, Hamman, Heyser, Old Ocean, Premont, Seabreeae, Segno and West Columbia have all had major extensions during 1937. The 1937 production for the Texas Gulf Coast was 120,141,429 bbl., or 32f per cent increase over the 1936 production of 90,865,293 bb1. t The total number of producing wells has increased from 6727 to 8968. Well abandonments have becn few and indications are that they will continue to be so. Rigid proration has been and continues to be in effect, and, as a result, wells in the Gulf Coast will have prolonged life. New Fields Tables 1 and 2 contain general information on all fields in this district. The following named fields were discovered in 1937: Aransas County.—Barnsdall Oil Company's No. 1-A Edwards was the discovery well for the Lamar field. It was drilled to a total depth of 9785 ft., plugged back and completed at 7530 ft. in the Frio as a gas and distillate well. Present indications are not very promising for a major field. Bee County.—The McMurray (Strauch) field was discovered by Dirks Bros. No. 1 Strauch at a total depth of 4577 ft. This is a Yegua producer, and had an initial production of 230 bbl. on a 3/16-in. choke. Brazoria County.—The Sandy Point field was discovered by Henry DeArmanls No. 1 Fite, which was completed as a producer at 6501 ft. in the Marginulina-Frio series. Galveston County.—Although the Hitchcock field was discovered in 1936, the first commercial oil producer was completed in 1937 when

Jan 1, 1938

By W. S. Ayres

[Secretary's Note.—At the Spokane meeting of the Institute, in discussion of President Brunton's address on "Modern Progress in Mining and Metallurgy in the Western United States," and at the request of members present, Mr. Ayres gave an oral account of his new separator, which is here published as an independent paper, partly because of its inherent importance and partly because it describes an improvement which did not originate in the Western United States, and therefore does not fall, strictly speaking, under the title of President Urunton's address.—R. W. R.] A brief history of the growth of the anthracite-coal preparation will give a better view-point from which to judge the present problem of separating slate from coal. At the beginning of the commercial value of anthracite, 70 years ago, only the pure portions, or " splits," of the veins were mined and shipped to market, and without any preparation or screening other than the selection, while loading, of the glassy lumps, and the rejection of the fine material and the slate that had strayed accidentally into the coal. The next step was the crushing or breaking of the coal (hence the name "breaker" as applied to the preparation-building), and the sizing of it by means of bars or revolving screens. This stage of its development marked the advent of the " breaker-boy " as a slate-picker, with his ever-increasing capriciousness. As the richer veins or a splits " became exhausted and the market demanded a still greater output, the less-pure " splits " and the thinner veins were utilized to produce the coal. Carrying as they do a far greater percentage of impurities, particularly when removing the pillars, it became necessary to build new and better equipped preparation-plants. Finally, we are now at the highest stage of complicatioii yet known to the art of coal-preparation. We are dealing with varying specific gravities, frictional difference, hardness, structure, and form in the pieces of coal and slate coming from many different veins, and

Jan 1, 1910

By T. C. Clarke

The history of iron construction in this country well illustrates the three phases of thought described by Auguste Comte, the French philosopher. The first is the era of faith, when belief in the safety of structures rests on the authority of the designer. The second is the era of criticism, when plans of structures are analyzed with much mathematical skill, but the data upon which the chain of reasoning depends is assumed upon insufficient experiment. The third, upon which we are now entering, is a scientific era, which demands experimental proof. It also demands that this proof shall be derived from experiments made on full-sized specimens, such as are in actual use, and not upon toy models. Until the construction of the United States testing-machine, now at Watertown Arsenal, it was impossible to make such experiments with accuracy. We now have a machine in which we can test full-sized specimens of every part of a bridge or other structure that we want to use, and under the same conditions in which it is actually used. The next thing is to get money to make these experiments available. No private individuals can afford to do it, and even if they could, they might wish to keep the results to themselves. So that the next point is that we want money, and that, I believe, everybodly thinks we should ask Congress for. We want also, as has been said, some one who shall make a business of testing, and who has plenty of time. Persons who are employed in private business are too much in a hurry; they want to do a thing and get done with it, and then do something else; but government officers are entirely free from this feeling; time to them is of no account, and in experimenting that is the very element that is of value; it does not do to be hurried; the great thing is to get it right and to test your results, and go over it, again and again. And the experimenter who operates the machine must be some person educated up to the use of it. We then want a general advisory board who will indicate a plan of experiments, collect the results; and publish them. Some experiments were made the other day at the Watertown Arsenal upon full-sized

Jan 1, 1882

Discussion of the paper of J. K. FURST, presented at the Pittsburgh meeting, October, 1914, and printed in" Bulletin No. 94, October, 1914, pp. 2493 to 2514. W..McA. JOHNSON, New York, N. Y.-On discussing this paper I am open to the criticism of "bringing coals to Newcastle," as I, a zinc man, am bringing new ideas on steel to Pittsburgh. But still the view of an outsider can be valuable to the insider. Any multistage process, where each apparatus operates on its particular part of the work at a high efficiency, constitutes an advance in the state of art. But in multiplicity there can be complication and ensuing loss and inefficiency. The duplex steel process is not the pronounced success which was predicted for it by its adherents, for several of such plants have reverted to plain open-hearth methods. If we regard broadly refining processes, such as the Bessemer, open-hearth, puddling, copper refining, lead cupelling, nickel refining, we find that in general refining processes are intermittent and 'concentration processes are continuous. (This generalization I believe to be original with me; it was communicated to Dr. E. F. Roeber, editor, and appeared as an editorial in Metallurgical and Chemical Engineering, March, 1905.) Where we desire primarily quality in a metallurgical operation we must put a batch of metal in the furnace, work on it until we get it to the required purity, test it, and take it out; whereas, if we desire primarily quantity we shove ore into a furnace and smelt it as fast as possible, allowing conditions to make a non-uniform product provided only we get tonnage. From general commercial principles, I believe that the weak point of the duplex process is that the operation is not a money maker unless the plant is kept at. 90 to 95 per cent. of its rated capacity, or unless the Bessemerizing is done so often that it is practically continuous. For in some manner the operation should be made continuous and the control on the tonnage should be commercially flexible. The commercial rigidity of having to control purity exactly increases operating costs without a corresponding gain. Conversely, the chief reason for failure of "steel from ore direct" is that it makes a final operation continuous, which should be naturally intermittent.

Jan 4, 1915

By Emerson F. Heald

A systematic study was made of new and old data on chemical activities in Fe-Pt alloys at elevated ternperatuves. Experimental results may be expressed in terms of the excess free energy using Least-squares analysis of the data gave the following values for the constants: for the temperature range 1130° to 1350°C, and tentatively to 155O°C, B = -3.326564 and C = 0.221051; for the temperature range 650" to 850°C, B = -2.555690, C = 1.762735, and D =0.097196. In the study of iron-containing silicate systems, it is sometimes desirable to have a direct experimental measure of the activity of iron in the system. The well-known solubility of iron in platinum, often a headache in experimental work on iron compounds under reducing conditions, can be used to advantage in this respect. If the activity of iron in an Fe-Pt alloy in equilibrium with the silicate is known as a function of the composition of the alloy, chemical analysis of the alloy will give a knowledge of the activity of iron in all of the phases in the system. The present study was undertaken in order to elucidate the characteristics of Fe-Pt alloys as iron activity indicators. This work is intended to tie together some previous work, which may be summarized as follows. Larson and Chipman1 determined the activity of iron in Fe-Pt alloys at 1550°C by equilibrating platinum metal with calcium oxide-iron oxide-silica melts of known iron activity. Compositions of the resulting alloys were determined by chemical analysis. A similar study was carried out by Taylor and ~uan,' who worked at 1300°C. They brought the Fe-Pt alloys into equilibrium with iron oxide under conditions of known partial pressure of oxygen, and thus, from the work of Darken and ~urr~,~ conditions of known iron activity. Compositions were determined indirectly, by following the change in weight of the sample. Sundaresen et el* used the electromotive force of cells in which the alloy formed one electrode in order to measure the activity of iron in the alloy at 650" and 850°C. These temperatures were chosen to be above and below the first-order phase transition which takes place upon the ordering of Fe3Pt and the second-order transition which occurs upon the ordering of FePt3. EXPERIMENTAL 1) High Temperatures. The starting materials used were thin platinum foil, about 0.002 mm thick, and Fisher Certified reagent ferric oxide, Fez03, which had been heated for 24 hr at 1000°C. An intimate mixture of 80-mesh Fez03 and platinum platelets was placed in a thin platinum foil envelope. The latter was suspended from thin platinum wires in the hot zone of a vertical-tube, platinum-wound furnace of the type described by Muan and ~sborn.~ A capillary gas mixer similar to that used by Darken and Gurry3 was used to prepare a precisely known mixture of carbon dioxide and hydrogen, which was allowed to flow upward through the furnace tube. The partial pressure of oxygen in contact with the sample was thereby fixed at a value which was calculated from the charts prepared by porter? Temperatures were measured with a Pt-10 pct Rh-in-platinum thermocouple, which was calibrated using the melting points of gold (1062 .@C) and diopside, CaMgSizOB (1391.5"C). Temperature control was maintained to within i3"C with a Geophysical Laboratory proportional controller, using the furnace resistance as the sensing element. Samples were quenched by passing a small current through the platinum suspension wires, allowing the sample to drop into a bath of dibutyl phthalate at the bottom of the furnace tube. Prior to chemical analysis the samples were washed with acetone and dried. 2) Chemical Analysis. It proved possible, in almost all cases, to separate the Pt-Fe platelets physically from particles of iron oxide. The platelets were dissolved in a small volume of aqua regia, evaporated to dryness, and redissolved to 0.1 M HC1. In order to determine iron in the platinum alloy potentiometrically, it is necessary first to remove the platinum. A 10-cm column of Amberlite IR-120 cation exchange resin in the hydrogen form provided separation quickly and quantitatively: The mixture of iron and platinum in 0.1 M HC1 was added to the top of the column, and washed with about 100 ml of 0.1 M HC1. Under these conditions, the iron, principally in the form of cations such as FeC1" and FeCl;, is held quantitatively in the uppermost centimeter of the column. The platinum, in the form of anions such as PtC&- , is washed through without being adsorbed. After a qualitative test with stannous chloride indicated all of the platinum was removed, the iron was

Jan 1, 1968

By H. Conrad, V. V. Damiano, G. J. London

The slip mode activated during the c axis compression of single crystals of commercial-purity ingot SR beryllium, high-purity (twelve-zone-pass) beryllium, and Be-4.4 wt pct Cu and Be-5.2 wt pct Ni alloys in the temperature range of 25° to 364°C was determined using two-surface slip trace analysis, slip-step height analysis, and electron transmission microscopy. All three techniques indicated the occurrence of copious pyramidal {1 122) (1123) slip in the alloys over the entire temperature range, the amount increasing with temperature. Pyramidal slip was also indicated in the high-purity beryllium by slip trace analysis and electron transmission microscopy, but the amount was somewhat less than in the alloys. For the commercial-purity ingot crystals, only a very small number of pyramidal slip lines were observed, and these were in the immediate vicinity of the fracture surface. No pyramidal dislocations could be detected by electron transmission microscopy in this material. Dislocatransmissiontions with Burgers vectors [0001] and +(ll20) were identified by electron transmission microscopy inthe (1122) slip bands, as well as those with the j (1123) vector. This was interpreted to indicate that the edge components of the 3(1123) vector dislocations activated during c axis compression dissociate upon unloading according to the reaction i (1123) — [0001] + 3(1120) THE microstrain c axis compression of single crystals of commercial-purity ingot SR beryllium (99.6 pct), high-purity twelve-zone-pass beryllium (99.98 pct), Be-5.24 pct Ni and Be-4.37 pct Cu alloys was described in a previous paper.1 This paper covers in detail the analysis of slip traces observed on two mutually perpendicular lateral surfaces of these specimens, and a detailed description of transmission electron microscopy studies performed on foils cut from the bulk crystals after they had been deformed to fracture in the c axis compression. Observation of slip traces on single surfaces of deformed single crystals are generally insufficient to positively identify slip or twinning modes. The use of two carefully cut and oriented perpendicular surfaces can greatly aid in the positive identification and index- ing of slip traces, although even this technique may be quite inadequate if more than one type of slip system operates and if an insufficient number of traces are observed on the surfaces. The problem is greatly simplified for symmetric cases like that for c axis compression of an hep crystal such as beryllium, in which the operating slip systems are all equally inclined to the direction of the applied stress, and each slip system of a given slip mode has an equal chance of operating. For such cases, the traces of any given slip mode observed on the surfaces cut parallel to the c axis are symmetrically tilted about the c axis. It is therefore possible to quickly determine whether one or more slip modes are operating. Confirmatory evidence in support of the observations made on the external surfaces can be obtained from foils cut from the deformed crystals and examined by transmission electron microscopy. This latter technique serves to identify not only the operating slip plane but also the Burgers vector of the dislocations which participate in the slip. For this purpose, a simplified technique based upon a double tetrahedron notation is used in the present paper. The planes and directions in the hep lattice are all designated by letters rather than indices and extinction conditions are easily determined if the Burgers vector lies in the plane contributing to the diffraction. RESULTS 1) Slip Trace Analysis. The standard (0001) stereo-graphic projection of beryllium is shown in Fig. 1. The two mutually perpendicular, lateral surfaces of the compression specimen are represented by the diametrical planes AA' and BB', also referred to as surface A and surface B. For the specific case represented (a Be-5.24 pct Ni specimen deformed by c axis compression at room temperature), the A surface is tilted 5 deg to the (10i0') plane and the B surface is tilted 5 deg to the (1120) plane. Two surface trace analyses may be facilitated by examining in turn the intersection of various great circle traces of specific pyramidal planes with two surfaces and comparing the angles made with the (0001) plane with those actually observed on the two surfaces. One then identifies the slip traces by trial and error on a best-fit basis. The (1122) type planes (it was found that slip occurred on these planes) are shown plotted on the stereographic projection in Fig. 1. One obtains directly the angles between the (0001) plane and the {1122) traces by measuring the angle from the periphery to the point of intersection along the lines

Jan 1, 1969

By Milton R. Pickus, Earl R. Parker

THE modern theories of creep¹-4 in general have been based upon the concept of generation and migration of dislocations, with the generation process normally assumed to be rate controlling. The theories are generally deficient in that they fail to take into account many factors that are known to influence creep. The influence of the state of the surface of the test specimen has been almost completely overlooked; yet the present report shows that the nature of the surface may, in certain cases, govern the creep characteristics of a specimen. In the period since Taylor" applied the concept of dislocations to a study of metals, a school of thought has developed that closely relates the plastic deformation of metals to the generation and migration of dislocations through the crystal lattice. It might be expected that the thermal energy required for the generation of a dislocation would be different from that for migration of the dislocation through the lattice. Furthermore, the activation energy for generation would be expected to vary for different parts of the solid metal. It has been predicted that dislocations would be generated most easily at external surfaces, but could also be activated at certain internal surfaces such as grain or phase boundaries. Within the body of the metal a range of values for the activation energy might be expected because of different degrees of disorder at such regions as grain boundaries, impurities, and second-phase particles. The particular value of the activation energy that was rate determining could then depend on the specific conditions of a test. If, for example, the surface atoms were by some means constrained, the generation of dislocations in the body of the metal might become the important factor. On the other hand, other conditions may favor generation at the surface. It is possible then that the creep behavior may not be completely determined by the inherent properties of the metal. Even the environment in which a test is carried out could have a significant effect. In fact it is conceivable that in order to obtain the maximum creep resistance from a given alloy, the surface atoms must be so constrained that the activation energy for generating dislocations on the surface is at least equal to that required for generation in the body of the metal. On the basis of such considerations, and in view of the limited number of publications discussing this subject, it seemed that an investigation of the influence of the state of the surface on creep might yield information of both theoretical and engineering interest. Experiments on single crystals, demonstrating a variation in the mechanical properties due to alterations in the surface layer, have been reported by several investigators.6-13 he results of these experiments have been briefly summarized;14 consequently, the earlier work will not be reviewed here. As an example of these findings the observations of Cottrell and Gibbons may be cited. They reported the critical shear stress of a lightly oxidized cadmium single crystal is greater by a factor of 2½ than a specimen with a clean surface. Materials and Methods Single crystals M in. in diam and 8 in. long were prepared from Horse Head Special zinc, melted under an atmosphere of helium in a large pyrex test tube, and drawn up into a long ½ in. diam pyrex tube by means of a vacuum pump. The cast zinc rods thus produced were cut into convenient lengths and sealed in evacuated pyrex tubes. Single crystals were grown by gradual solidification of the remelted rods. Cleaving the ends of the single crystal specimens chilled by liquid nitrogen proved a simple method for determining orientations from the exposed basal plane from the markings left on the cleaved surface that gave the slip directions with sufficient accuracy for the experimental work. The specimens chosen for the experiments were those having the angle between the basal plane and the specimen axis within the range of 15" to 65". Since zinc single crystals are quite delicate, it was necessary to devise an appropriate method of gripping the specimens in order to suspend them in the furnace and apply the load. Stainless steel collars were prepared having an inside taper, the smaller end of the taper being of such a size that the specimen could just pass through freely. The tapered hole did not extend the full length of the collar; a sufficient thickness of metal remained so that a hook could be attached to provide a means of applying the load and suspending the specimen. One of the collars was slipped over the upper end of a specimen which was supported vertically in a steel jig. The collar was then heated electrically until the end of the crystal melted and filled the collar with molten zinc. At this point the application of heat was discontinued, whereupon the molten zinc quickly solidified, due to the chilling effect of the jig. The specimen was then inverted and the second collar applied in a similar manner. The jig served several purposes: limiting the length of specimen that was melted, providing excellent alignment of the collars with respect to the specimen axis, and protecting the specimen from mechanical damage. Once the specimen was suspended in the furnace and loaded, it was desired to accomplish the surface treatment with a minimum of disturbance of the specimen. Around the specimen was a long pyrex tube, the upper portion of which was approximately 1 in. in diam, and in it was a copper coil of such a diameter to fit snugly against the tube. A specimen, approximately ½ in. in diam and 4 in. long, was suspended by means of a stainless steel rod so that it hung within the copper coil. The lower portion of the glass tube was approximately ¼ in. in diarn, and passing through it was a 5/32 in. diam stainless steel rod which hung from the lower specimen collar. This portion of the glass tube and the stainless steel rod extended through the bottom of the furnace. A T-connector, with suitable packing, was attached to the lower end of the stainless rod to provide a water-

Jan 1, 1952

By M. B. Bever, A. M. Reti, A. K. Jena

The results of this investigation show that in the system SnTe-PbTe l) the solid solutions have small exothermic heats of formation relative to the binary compounds, 2) solid-solution hardening is almost absent, 3) the tin and lead atoms are .randomly distributed on the sublattice occupied by them and do not undergo an ordering transition during a thermal treatment designed to promote such a transition, and 4) the lattice parameter changes linearly with composition. These findings suggest that the solid solutions of tin telluride and lead telluride approach ideal behavior. THE binary compounds SnTe and PbTe form a continuous series of solid solutions.' Information on several physical properties of these solid-solution alloys has been published.1"3 In the work reported here, the heats of formation, microhardness, and lattice parameters of these alloys have been measured and the possibility of an order-disorder transition has been investigated. Order-disorder transitions occur in some solid solutions of binary compounds. In the system Bi2Te3-BizSes, for example, the electropositive bismuth atoms and the electronegative tellurium and selenium atoms always occupy separate layers. In the disordered alloy Bi2Te2Se, the tellurium and selenium atoms are randomly distributed on the layers occupied by them, while in the ordered alloy they occupy distinct layers.4 The NaC1-type (Bl) structure of SnTe-PbTe alloys consists of two sublattices, one of which is occupied by the electropositive tin and lead atoms and the other by the electronegative tellurium atoms; any ordering would be expected to occur in the sublattice occupied by the tin and lead atoms. PREPARATION OF SPECIMENS Polycrystalline specimens of PbTe and Sn1-xPbxTe (x = 0.25, 0.50, and 0.75) were prepared by melting stoichiometric amounts of lead (99.999 pct), tin (99.98 pct), and tellurium (99.999 pct) in evacuated and sealed Vycor tubes. Because of the deviation of tin telluride from the stoichiometric composition5 this compound was prepared by melting 49.8 at. pct Sn and 50.2 pct Te. The tubes containing the melts were quenched into water; the solidified ingots were removed from the tubes and annealed for 2 weeks in vacuum (PbTe approximately 100°C below its melting point, the three alloys 100°C below their solidus tem-

Jan 1, 1969

By R. Bainbridge

THE Consolidated Mining and Smelting CO. of Canada Ltd. has operated a lead smelter at Trail, B. C., for many years. In order to take advantage of metallurgical advances, as well as to improve materials handling methods, this company, commonly known as "Cominco," commenced planning a program of smelter revision and modernization some years ago. The first stage of this program involved the design and construction of a new blast furnace gas cleaning system. The selection of equipment, the design of facilities, and preliminary operating details of this system will be dealt with in this paper. The essential problem was to clean and collect 100 tons of dust daily from 153,000 cfm* (12,225 lb per min) of lead blast furnace gas which varied in temperature from 350º to 1100°F. Because it was desired to collect the dust dry, either a Cottrell or a baghouse cleaning plant was to be selected. Comin-co's many years of experience with both systems provided a background for choosing the most satisfactory installation. All information pertinent to the two methods of dust recovery was carefully investigated, and it was decided to replace the existing equipment with a baghouse. Very briefly, the reasons for this decision were as follows: 1—A baghouse installation would be practical because the SO2 content of the gas was low and corrosion would not be a problem if the baghouse operating temperatures were held sufficiently above the dew point. 2—Variations in the physical characteristics of fume and dust, which are inherent in this blast furnace operation, should not substantially affect the operating efficiency of a baghouse. 3—For the same capital cost, metal losses (stack and water losses) would be appreciably less in a baghouse. 4—A baghouse would be easier to operate, and would not require the use of highly skilled labor. 5—Operating and maintenance costs of a bag-house would be lower. 6—The only available space for reconstruction was relatively small, and not suited to a Cottrell installation. Once the baghouse system was decided upon, detailed design of the installation was begun. Baghouse Design Gas Cooling: Before the required capacity of the baghouse could be determined, the method of cooling the gas to the temperature necessary for bag-house operation had to be chosen. The problem confronting the design engineers was how best to cool 153,000 cfm of gas from a temperature ranging from 350°F to brief peaks of 1100°F, down to 210°F, the maximum safe baghouse inlet temperature. A survey of existing blast furnace gas temperatures in the outlet flue showed that the normal range was as given in Table I. The obvious choices of cooling method were: 1— cool completely by the addition of tempering air; 2—utilize a heat exchanger; 3—cool by radiation; and 4—cool with water spray in conjunction with the admission of tempering air. The advantages and disadvantages of the various cooling methods were: Air Addition: To cool completely by the admission of tempering air involved tremendous volumes, Fig. 1. For example, to cool 1 lb of blast furnace gas at 450°F requires 1.84 lb of air at 80°F or 1.60 lb at 60°F. As it is necessary to design for peak conditions, it can readily be seen that volumes of tempering air in the order of 1,500,000 cfm would have to be handled. Using the normal design figure of 2.5 cu ft per sq ft of bag area, a baghouse installation comprising some 600,000 sq ft of filter cloth would be necessary. Such design requirements would be prohibitive, not only from a standpoint of capital expenditure, but also because of space limitations. Heat Exchanger: The utilization of a heat exchanger was given serious consideration. A horizontal tube unit using air as the medium to cool the required volume of blast furnace gas from 400" to 250°F was investigated. Cooling above 400°F would be done by water spray, and below 250°F by admission of tempering air. The estimated capital cost of such a unit was found to be prohibitive. From an operating standpoint, there was considerable doubt as to whether the soot blowing equipment provided would effectively keep the dust from building up on the tube surface. The performance of heat exchangers operating on dusty gas in other company operations had not been too favorable. Radiation Cooling: Although somewhat cumbersome, gas cooling by radiation from 'trombone' tubes or other similar equipment (cyclones) is employed in many metallurgical operations. Such an installation was also considered. However, calculations showed that an installation much larger than the space available would be required to handle the gas volume involved. For example, to cool 153,000 cfm of blast furnace gas from, say, 600' to 250°F (i.e., remove in the order of 58,500,000 Btu per hr with heat transfer rates varying from 1.1 Btu per sq ft per hr per OF for the higher temperature ranges to 0.88 Btu per sq ft per hr per OF for the lower ranges) would need a cooling area of some 175,000 sq ft.

Jan 1, 1953

By AIME AIME

T HE appointment of Herbert Hoover to the portfolio of Commerce in the President's Cabinet is to engineers the fulfillment of a long deferred hope to have an engineer in high political office and is a matter of congratulation to us for three reasons; because he is a mining engineer who represents the highest type of idealistic engineering effort; because he is a past president of the Institute; and because he has probably a broader grasp of world problems than any other living engineer. Frank A. Vanderlip in the preface to his book "What Happened to Europe" tells of the many interviews he had with the most prominent men in Europe which were made possible for him by his eminence as a banker and by the courtesy of the American ambassadors. He cites by name such well known figures as Austin Chamberlain, Sir Auckland Geddes, Monsieur Delacroix, Monsieur Briand, Mr. Padkrewski, Mr. Venizelos, Colonel House, General Pershing, Mr. Baruch, and many others and says :

Jan 1, 1921

By AIME AIME

AMONG the members of the Institute there are thirty-three who have been members for a half- century or-more Some time ago a professor of psychology made a careful study of a group of unusually brilliant children to determine whether there was any truth in the general belief that a brilliant mind is usually to be found in a physically sub-normal body. He definitely proved the exact opposite and it is now known that children who are above the average in mental capacity are also above the average in physical health and strength.

Jan 1, 1929

By John Hays Hammond

The following notes are descriptive of a country as yet in its infancy as regards the advancement made in mining operations. Its inaccessibility and other militating circumstances have retarded progress in that direction. With the completion of the railroad, now under construction, having the city of Cali as its objective point, with the concomitant civilizing and developing consequences, it is certain that the slopes of the Cordilleras will prove to be a South American Eldorado. Deposits of coal, copper, and minerals other than those of the precious metals are known to exist in quantities which, under more favorable conditions of accessibility, etc., could be profitably mined. The Government of the United States of Colombia, I think, is disposed to encourage and foster mining enterprises. Articles designed for mining are admitted free of duty; the permanency of the government is, at least, as well assured as that of Mexico (which is not noted for its immutability), and a more sincerely friendly sentitment towards Americans prevails in the United States of Colombia than in Mexico. This paper is confined to a description of the property of the Cauca company's mines, and is intended rather as a preliminary notice than as an exhaustive report. The Cauca mining district is reached by the following route: New York to Aspinwall; to Panama; to Buenaventura, a port on the west coast of the United States of Colombia, distant thirty-six hours from Panama by steamer; to Cali in the State of Cauca. The State of Cauca is bounded on the north by the Atlantic Ocean, on the northwest by the State of Panama, on the northeast by the States of Bolivar and Antioquia, on the east by Brazil and Venzuela, on the south by the Republic of Ecuador, and on the west by the Pacific. Ocean. It has a territory of 41,443 square miles, which is about one-tenth of the entire territory of the United States of Colombia. Its population, including the 50,000 savage Indians of the Caqueta (some of whom are cannibals), is nearly 450,000 souls, or about one-sixth of the population of the Colombian republic. Of these, one-fifth are whites (Spanish' South Amer-

Jan 1, 1885

By D. C. Reynolds

Recent experiments with II-VI compounds have shown that they hazle considerable potential for laser applications over a broad region of the optical spectrum. It may be possible to cover the spectrum continuously from 3200A (ZnS) to the far infrared (CdHg:Te) since HgTe is a semimetal. At this writing laser action has been observed in ZnS, Zn0, CdS, CdSe, CdS:Se, CdTe, and some of the CdHg:Te alloys. Of particular interest are those lasers operating in the zlisible and near ultraciolet regzons of the spectrum where detectors of high sensitivity are available. The lasing transitions in II-VI compounds are bound exciton transitions some of which have been identified in auxiliary experiments. High efficiencies and low thresholds for lasing hare been achieved almost exc1usively in plutelet-type crystals. The greater crystalline quality exhibited by the phtelet-type material is shown to result from the crystal growth habit. Phonon scattering- of conduction electrons to the ground-state exciton is discussed ill relution to Lou thresholds and high efficiencies for lasing- observed in the CdS:Se solid solutions. The first successful semiconductor laser operation was achieved in the III-V compounds. It is possible to choose a material in this group that will operate between approximately 0.65 and 8.5 . There are at least two reasons why one would like to have a laser operating at shorter wavelengths. First, it would be easier to experiment with a laser operating in the visible region of the spectrum, and also more desirable to have high-in tensity visible light sources. Second, the most sensitive photomul-tiplier detectors are available in the visible and near ultraviolet regions of the spectrum. It is known that II-VI compounds are direct-band-gap semiconductors and as such offer the potential of operating at any specified wavelength between 3200 (ZnS) and 7772A (CdTe). Light emission from II-VI compounds has been the subject of numerous investigations for many years. These investigations were all primarily concerned with noncoherent emission. It has been only recently that coherent emission from these compounds has been observed. To date, laser operation has been demonstrated in CdS, CdSe, and the solid solutions of CdS:Se, ZnS, ZnO, and CdTe. These compounds cover an appreciable portion of the optical spectrum from the ultraviolet to the near infrared. In considering laser applications, the use of lasers in communication's systems offers many desirable features. In any operation of this type one must consider the losses in transmitting the radiation from the source to the detector. Atmospheric absorption in the visible and near ultraviolet is variable and greater than in certain regions of the infrared. It might be concluded that for long-range communication systems an infrared laser operating in a spectral region that is coincident with a transmission window in the atmosphere would be preferable. However, one cannot overlook the possibility of operating a system in the sensitive region of a highly sensitive photomultiplier detector or other light-amplifying system. LASER CONSIDERATIONS To produce a source of coherent radiation it is necessary to achieve a population inversion. In the case of semiconducting materials it is necessary to raise the electrons from one energy state to a higher-energy state relative to it. In semiconductors, this population inversion can be achieved by three different techniques: 1) Current Injection. This technique uses a p-n junction biased in the forward direction. Large numbers of electrons are injected from the n region into the p region, and recombination occurs close to the junction. An inverted population is obtained in this region and the recombination radiation propagates parallel to the junction. This type of pumping has been used in the GaAs junction-type lasers but has not been successfully employed in the II-VI compounds. 2) Optical Pumping. In this case, one uses photons to obtain a population inversion by exciting electrons to higher-energy states. The pump sources are flash lamps or arc lamps and, occasionally, other laser sources when such sources have the appropriate energy for exciting the electrons. The disadvantage of this type of pumping is that flash lamps put out a rather broad spectrum of radiation, whereas the laser material has a rather narrow region of absorption. This results in an inefficient process. Laser sources provide efficient pump sources but the number of usable wavelengths is limited. 3) Electron Beam Pumping. In this technique, the laser sample cavity is bombarded with electrons having energies in the range from approximately 10 to a few hundred kv. The bombarding radiation excites electrons from valence to conduction band states in the semiconductor, giving rise to an inverted population. This type of pumping has been used successfully in several 11-VI compounds.

Jan 1, 1968