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By D. J. Pye

Certain high molecular weight synthetic polymers in very dilute solutions decrease water mobility in porous media 5 to 20 times more than would be expected from the solution viscosity. This indicates that increasing water viscosity to reduce adverse mobility ratios in water floods is economically feasible in many situations. Laboratory results are consistent with accepted theory with respect to improved areal sweep, permeability distribution and displacement efficiencies as would be predicted from the solution mobility measured in the core. The laboratory results have been confirmed by field pilot floods which recovered 80 per cent and 100 per cent more oil than comparative water-flood pilots in fields containing 16 cp and 130 cp oil respectively. Economic analyses based on pilot data indicate the method to be profitable. INTRODUCTION The desirability of improving the water-oil mobility ratio in waterflood-ing operations has long been appreciated, especially for high viscosity crudes. Methods of reducing the oil viscosity by application of heat, gas resaturation and miscible drives have met with some success. Conversely, it has been generally conceded that increasing the water viscosity would also be effective, but the amount of thickening agent required to effect an appreciable increase in viscosity is discouragingly high. The use of such materials as glycerin, sugar, or glycols is completely out of the question economically, so that considerable attention has been given to the use of the much more efficient synthetic water-soluble polymers as viscosity improvers; but even these materials are not economically attractive. If increased water viscosity could be economically realized, marked improvements in areal sweep efficiency, as discussed by Caudle and Wittel and others, would be realized in field operations. Similarly, the improved mobility ratio would bring about increased recoveries by correcting permeability distribution problems as discussed by Stiles2 and Dykstra and Parsons,' and improvements in displacement efficiency would be obtained as recognized by Buckley and Leverett4 and Welge.5 LABORATORY STUDIES THE RESISTANCE EFFECT In the course of research to develop a more efficient water-soluble polymer viscosity builder, we discovered that a very few types of water-soluble polymers exhibited a most unusual and very interesting property not previously observed. Among the earliest materials showing such activity were polymers containing acry-lamide. Fig. 1 shows a typical plot of the solution viscosity vs concentration for one of these polymer solutions as determined in an Ostwald viscometer. As usual, such a plot is an approximate straight line on semi-logarithmic paper. Now, an inspection of Darcy's law, shows that a viscosity value can also be determined in a formation sample if the pressure, flow rate and permeability are known. If the core permeability is previously determined with wa- ter or brine, then the viscosity of another aqueous fluid may be determined from the equation. The viscosities so determined for glycerin (glycol or polyvinyl alcohol solutions, for example) agree with the viscometer determinations. However, in the case of the water-soluble polymer solutions in which we are interested, the viscosities measured in the formation sample depart very markedly from the viscometer values. A typical relationship for a polymer solution is also shown in Fig. 1. This unusual departure from the expected response is referred to as a resistance property of the polymer and is quantified as "resistance factor". Since the resistance factor R can best be determined in a core under study, the term has been defined on the basis of the ratio of the brine mobility to the polymer solution mobility at residual oil saturation so that:

Jan 1, 1965

By H. H. Keller, E. J. Couch

Damage to production wells subjected to the high temperatures associated with in-situ combustion projects has been a problem since the advent of this thermal recovery technique. Injection of water down the annulus of hot wells has been successfully utilized for cooling and prolonging the life of such wells. A mathematical model that is suitable for predicting the effectiveness of cooling water in a particular application is developed. Typical results for practical ranges of the various parameters involved are presented. INTRODUCTION In the normal course of in-situ combustion operations, highly damaging conditions develop in the production wells as the combustion zone approaches, and these wells are subjected to high temperatures (up to 1500F). The resulting well damage is recognized as one of the more serious operating problems unique to the in-situ combustion process. Even in operations where well completions have been specifically designed to cope with this problem, the question arises as to how this destructively high temperature can be kept within tolerable limits. A simple and economical approach to this problem is to circulate cooling water down-hole. This method has been used with some success in shallow reservoirs. At greater depths, however, the heat exchange with the overburden surrounding the well and between the fluids in the tubing and the annulus tends to equalize the temperatures of the two fluid streams so that the cooling capacity delivered to the bottom of the hole decreases with well depth. This method would provide no appreciable control over the bottom-hole temperature at great depths. In order to delimit the condition under which cooling by water circulation is effective, the wellbore temperature must be related to the water inlet rate and temperature; to the reservoir depth, production rate, and initial temperature; and to the combustion at at bot tom-hole depth. A model that meets these requirements and that will offer an approach for developing engineering solutions to practical design and operating problems is described in this paper. MATHEMATICAL MODEL Previous studies of temperature distributions include those for flowing wells1p2 and those for hot fluid injection. Adams and Haddenhorst 6 presented solutions for the down-hole circulation of hot oil in the treatment of paraffin-deposition problems. In this paper the thermal model presented by Ramey 4 is adapted to the flow system shown schematically in Fig. 1. Water at temperature Ti is injected at a rate wi and flows down the annulus outside the tubing. It mixes at bottom-hole depth D with the fluids produced at race w from the hot reservoir at temperature T. This mlxtureJ. of injected water and reservoir fluids flows up the tubing and is produced at the surface at TI,. In order to describe the temperature response in this system, we make use of the usual conservation of

Jan 1, 1969

By Carl Swartz

FOR many years kettles used in the melting and refining of lead and other nonferrous metals and alloys have been made of cast iron. The logic of this probably lies in the fact that cast iron has been known as a material of construction for vessels of this type much longer than steel, and satisfactory fabrication from it has been more easily accomplished and better understood. As the capacity of lead refineries has increased, it has been only natural to increase the size of kettles. Today kettles of 150 to 250 tons are not uncommon. As the size of the kettles increased and better shapes were designed, the uniformity of material of construction became more important. Records kept over comparatively long periods of time have shown that the length of service of kettles has not been uniform. Many causes contribute to this and the importance of each has not yet been evaluated. Kettle design, kettle setting, method of firing and material of construction have been changed from time to time to obtain better service, but the variation in length of service is still great. A kettle may fail during the first few heats or may last through more than one thousand heats. The purpose of this article is not to present the conclusions of a finished piece of research on kettle manufacture and use, but to present a series of observations made over considerable time in the hope that others will publish data and that all may be correlated into a logical scheme which will result in better service and longer kettle life.

Jan 1, 1931

By Robert Hunt

The American Institute of Mining and Metallurgical Engineers was the first American technical organization to consider steel-rail specifications and sections. If I am not mistaken, the first contribution on those subjects to the Proceedings of the Institute was presented by Prof. Thomas Egleston, in 1874, and was entitled "Investigations on Iron and Steel Rails made in Europe in the Year 1873.1" The next contribution was Dr. C. B. Dudley's report of his investigation for the Pennsylvania Railroad of the wear of steel rails in their tracks, in 1878, which contribution led to a very memorable discussion that extended through several meetings.2 In 1880, Mr. C. P. Sandberg3 presented an article on rail specifications and inspection and rail sections. This was followed, in 1881, by A. L. Holley,4 in his exhaustive report on the then used American rail sections. The next contribution, I believe, was made by myself' at the Buffalo meeting, in 1888, on steel-rail specifications, which I followed,6 in 1889, by a paper on steel-rail sections. Since that time there have been numerous contributions to the Transactions of the Institute in relation to the manufacture of steel rails. The American Society of Civil Engineers officially took up the investigation of the relation of rail sections to the wear of car wheels in 1888. In the prosecution of this work, the Society appointed a special committee, whose labors extended through several years and resulted in an exhaustive report to the Society in 1893.7 Later, another committee was appointed to consider specifications for the manufacture of steel rails; the labors of this committee extended over a period of several years, a final report8 being made in 1910. It was my fortune to be the secretary of both of those committees.

Jan 9, 1919

By J. A. Cordier

USINOR has conducted four blast furnace tests with formcoke made from marginal coals in the pilot plant of HBNPC ("H. B. N." process) in four different blast furnaces of various sizes and with medium and high grade burdens. The tests in which up to 30% of the blast furnace fuel burden was replaced by HBN formcoke yielded good results on furnaces ranging in hearth diameters from 5.6 to 9.5 m. The tests demonstrated that: - the slight increase of pressure drop in the stack did not prevent smooth operation at record production rates with the same blowers - the total coke rate was not significantly affected, but there was a slight increase of the calorific value of the top gas - the hot properties of the formcoke are satisfactory as seen from the samples withdrawn at the tuyeres and tapholes. At the end of the two months test on BE nº 2 of Dunkerque, the hearth was as permeable and clean as with good standard coke. Our conclusion is that HBNPC formcoke made from lean coals is an adequate substitute for conventional coke in the range of 20 to 40% replacement, which is of interest to USINOR.

Jan 1, 1977

By Robert Abbott

THE influence of various elements in retarding or accelerating the absorption of carbon during the process of carburization is fairly well known. In general those elements which forth carbides accelerate the absorption, while those which do not retard it. It has sometimes been wrongly stated that those elements which raise the temperature of the critical range increase the absorption, while those which lower this temperature decrease it. Silicon is a notable exception to this rule, for its influence is to raise the critical range but to lower the absorption of carbon. Some elements which do not form carbides have no apparent influence upon the absorption rate. Carbon itself retards the absorption rate. With a view to obtaining more exact data upon the subject the following experiments were undertaken : 208 steels of different chemical composition were selected to represent most of the types of modern constructional steels. Specimens 3 in. in diameter and in. in length were weighed to milligrams. They were then packed in the special carburizing box shown in Fig. 1, and kept in .the furnace for 10 hours at a temperature of 900° C. A duplicate experiment was conducted at 1,000° C. At equal' intervals of time the box was rotated in the furnace so that. two complete revolutions were made in the 10 hours. This precaution was taken to neutralize as much as possible any effect of unequal heating. At the end of the 10 hours the box was allowed to cool in the furnace with the doors open. The specimens were then weighed again and the increased weight (carbon) determined. In. the following table are given the analyses of the various steels, together with the. increased weight of .carbon expressed in milligrams.

Jan 10, 1913

By C. H. Li, R. J. Stokes, T. L. Johnston

Sodium chloride crystals are brittle in the presence of surface microcracks. Water immersion leads to an enhancement of ductility which is retained indefinitely in dry air providing the crystal is dried without leaving a surface precipitate. Storage in a damp atmosphere results in a surface reaction and consequent rembrittlement. Although elimination of surface flaws in ionic solids does not necessarily enhance ductility, there is always a change in the location of the fracture origin. EVER since the original experiments of Joffel there has been controversy over their interpretation and no satisfactory generalized explanation has yet been given. It is generally admitted that when sodium

Jan 1, 1961

By W. C. Knoblaugh

Rotary kilns are adaptable to many fuels, but this paper deals principally with the use of powdered coal. The observations and conclusions presented are based on rotary kilns used in the manufacture of basic refractories for steel furnaces. Solid fuels are pulverized for two principal reasons: (I) ease of control, and (2) rapidity of combustion. By the use of pulverized coal, the operator can increase or decrease the fuel supply by small increments and with very little time lag between the change of control and the resultant change in the flame. This is extremely important in this type of furnace, as the temperature range for maturing the clinker is very narrow. By fine grinding, it is possible to increase the rate of burning of the coal, thereby liberating great quantities of heat within a small space in a short time. Under given conditions, temperature is a measure of the heat liberated per unit of time. To attain the temperatures of 2950° to 3150ºF., which are encountered in the manufacture of various steel-furnace refractories, it is estimated that it is necessary to liberate 125,000 to 175,000 B.t.u. per cubic foot of the burning zone per hour. The manufacture of dolomitic refractories is a ceramic process and, as is true in most such processes, the material must be subjected to a certain critical temperature for a certain length of time in order to complete the reaction. If the time of reaction is reduced, the temperature must be increased; in other words, if the rate at which the material flows through the hot zone of the kiln is increased, the temperature of the hot zone must be increased to compensate for this shorter exposure to the flame. Firing with Pulverized Coal Fig. I is a line drawing of a rotary kiln with the attendant equipment indicated in their relative positions. The kiln proper consists of a sloping, refractory-lined steel tube rotating slowly about its longitudinal axis (0.75 r.p.m.), and is countercurrent in operation in that the raw feed is introduced at the stack end and gradually approaches the zone of highest temperature at the lower end, where the fuel is introduced. Before 1930, the usual method of firing a rotary kiln was to store the coal in the pulverized form and then feed from this storage to the kiln as needed. This proved unsatisfactory and dangerous because of dust explosions and the inability to obtain an even feed to the kiln caused by arching of the coal in storage and flooding of the coal feeders. In later years the practice has been to store the raw coal and grind it as it is needed. Such a layout is indicated in Fig. I. The coal is stored in bins, charged from the top and drawn from the bottom into recording scales and then into some type of unit pulverizer. There are a number of good pulverizers .on the market, each incorporating features that the manufacturer considers outstanding.

Jan 1, 1948

By W. C. Knoblaugh

Rotary kilns are adaptable to many fuels, but this paper deals principally with the use of powdered coal. The observations and conclusions presented are based on rotary kilns used in the manufacture of basic refractories for steel furnaces. Solid fuels are pulverized for two principal reasons: (I) ease of control, and (2) rapidity of combustion. By the use of pulverized coal, the operator can increase or decrease the fuel supply by small increments and with very little time lag between the change of control and the resultant change in the flame. This is extremely important in this type of furnace, as the temperature range for maturing the clinker is very narrow. By fine grinding, it is possible to increase the rate of burning of the coal, thereby liberating great quantities of heat within a small space in a short time. Under given conditions, temperature is a measure of the heat liberated per unit of time. To attain the temperatures of 2950° to 3150ºF., which are encountered in the manufacture of various steel-furnace refractories, it is estimated that it is necessary to liberate 125,000 to 175,000 B.t.u. per cubic foot of the burning zone per hour. The manufacture of dolomitic refractories is a ceramic process and, as is true in most such processes, the material must be subjected to a certain critical temperature for a certain length of time in order to complete the reaction. If the time of reaction is reduced, the temperature must be increased; in other words, if the rate at which the material flows through the hot zone of the kiln is increased, the temperature of the hot zone must be increased to compensate for this shorter exposure to the flame. Firing with Pulverized Coal Fig. I is a line drawing of a rotary kiln with the attendant equipment indicated in their relative positions. The kiln proper consists of a sloping, refractory-lined steel tube rotating slowly about its longitudinal axis (0.75 r.p.m.), and is countercurrent in operation in that the raw feed is introduced at the stack end and gradually approaches the zone of highest temperature at the lower end, where the fuel is introduced. Before 1930, the usual method of firing a rotary kiln was to store the coal in the pulverized form and then feed from this storage to the kiln as needed. This proved unsatisfactory and dangerous because of dust explosions and the inability to obtain an even feed to the kiln caused by arching of the coal in storage and flooding of the coal feeders. In later years the practice has been to store the raw coal and grind it as it is needed. Such a layout is indicated in Fig. I. The coal is stored in bins, charged from the top and drawn from the bottom into recording scales and then into some type of unit pulverizer. There are a number of good pulverizers .on the market, each incorporating features that the manufacturer considers outstanding.

Jan 1, 1948

By David W. James

DURING a recent investigation of the transition from a planar to a nonplanar solid/liquid interface for the systems H20-NH4F and 0-AIR,' an apparatus was developed which enabled the morphology of the ice-water interface to be examined during the transition. The slightly curved interface was viewed at a glancing angle with a Bausch and Lomb X30 stereomicro-scope. The interface was obliquely illuminated by a polarized light source. It was thus possible to differentiate between small projections or depressions at the interface, both by a shadowing effect and by the way in which they distorted the colored interference fringes across a particular crystal surface. Many attempts were made to photograph the various stages of interface breakdown. Unfortunately, the limited depth of focus of the microscope rendered the system unsuitable for photographic recording. Visual examination, however, was facilitated by continuous adjustment of the microscope focus control. The following observations of the interface transition were recorded for dilute solutions of ammonium fluoride in water. They are compared with iller's postulated morphologies shown in Fig. 1. i) The initial departure from planarity was characterized by the appearance of a large number of small depressions or "pores" in the interface. ii) The pores were arranged in wavy rows all lying roughly in the same direction within a particular grain. iii) The pores did not appear to form near to grain boundaries. iv) The pores appeared in certain grains before others. v) The transition from the pore structure to the elongated cell structure, Fig. l(d), was difficult to follow. It occurred quite rapidly and no truly irregular cell structure, Fig. l(c), was noticed. vi) The elongated cells gradually became more uniform in size and shape, with straight cell boundaries. They remained elongated, however, and no regular hexagonal cells were observed, cf. Fig. l(e). Several conclusions may be drawn from these observations. Firstly, the appearance of a poxed or, more accurately, a pore structure can be used as a criterion for the onset of constitutional supercooling. Care should, of course, be taken to distinguish between the true pore structure and artifacts caused by splashed-back liquid, particles of oxide, or inefficient decantation of liquid retained between cell boundaries, as described by Spittle et al? Secondly, and contrary to the suggestions of Tiller el l., it seems that interfacial perturbations are characterized not by curved projections but by small depressions or pores. A recent independent investigation by Biloni, Bolling, and cole5 reported in this issue indicates that the depressions might be explained in terms of dislocations intersecting the solid/liquid interface. It is possible that the dislocation concentration is reduced in the vicinity of grain boundaries. This would then explain the grain boundary depleted areas noted in (iii) above. This work was partially supported by the Air Force Office of Scientific Research, Contract No. AF 49-(638)-1029.

Jan 1, 1967

MAY 17-The last bit of verbal sod had hardly come to rest on the grave of the coal industry-which grave was being eagerly dug with typewriters and microphones by administration hangers-on and even an operator or two-when its leaders gathered for the 1950 Coal Convention of the AMC in Cincinnati on April 24. Surprisingly, mourning clothes were not being worn but the boys had on their diggers preparatory to digging their way out from under the muck. High costs created by wage and welfare demands, together with work stoppages, have caused markets to shrink, but even so, an optimistic air still prevailed as new techniques were disclosed at technical sessions. The administration, however, came in for its share of knocks.

Jan 6, 1950

By Albert Hill Fay

IN giving a sketch of the geology and mining of the tin-deposits of Cape Prince of Wales, a short description of the geographic and climatic conditions may be of special interest on account of this being a part of the world of which very little is known, even by the reading public. As shown in Fig. 1, the location of the Cape is lat. N. 65° 35' and long. W. 168°. It is bounded on the north by the Arctic ocean ; on the west by Bering strait and on the south by Bering sea. It is the western-most point of the mainland of North America, and to the west, across the strait, one can see East Cape, Siberia, which consists of a rugged, steep coast of granite cliffs. The climatic conditions are of interest because of the part they have had in the surface geology, and also because they affect mining from an economic standpoint. In connection with the climate and geography, it does not seem out of place here to quote a few lines from the prologue of The Wandering Jew, written by Eugene Sue, under the caption '1 The Land's End of Two Worlds."

Sep 1, 1907

By Carl E. Swartz

For many years kettles used in the melting and refining of lead and other nonferrous metals and alloys have been made of cast iron. The logic of this probably lies in the fact that cast iron has been known as a material of construction for vessels of this type much longer than steel, and satisfactory fabrication from it has been more easily accomplished and better understood. As the capacity of lead refineries has increased, it has been only natural to increase the size of kettles. Today kettles of 150 to 250 tons are not uncommon. As the size of the kettles increased and better shapes were designed, the uniformity of material of construction became more important. Records kept over comparatively long periods of time have shown that the length of service of kettles has not been uniform. Many causes contribute to this and the importance of each has not yet been evaluated. Kettle design, kettle setting, method of firing and material of construction have been changed from time to time to obtain better service, but the variation in length of service is still great. A kettle may fail during the first few heats or may last through more than one thousand heats. The purpose of this article is not to present the conclusions of a finished piece of research on kettle manufacture and use, but to present a series of observations made over considerable time in the hope that others will publish data and that all may be correlated into a logical scheme which will result in better service and longer kettle life.

Jan 1, 1931

By C. F. Floe, M. Cohen, M. B. Bever, V. G. Paranjpe

NITROGEN is becoming recognized as one of the important elements in ferrous physical metallurgy. Several investigations indicate that nitrogen plays a significant part in such phenomena as strain aging and temper brittleness. Nitrogen is known to be a powerful austenite stabilizer and may be a useful alloying element in stainless steels. The hard-enability of steels has been found to be increased by nitrogen. The nitriding and carbonitriding pro- cesses are examples of successful industrial application of nitrogen in ferrous materials. For a complete understanding of the various roles played by nitrogen in ferrous metallurgy a knowledge of the phase relations in the binary iron-nitrogen system is essential. The literature contains a variety of iron-nitrogen phase diagrams. Those suggested by Fry, Sawyer,² Epstein and his coworkers,³,4 Lehrer,5 Eisenhut and Kaupp, and Hägg7,8 differ significantly from one another. Moreover, the most recent of these investigations dates back about twenty years. A re-determination of the entire diagram, therefore, appeared desirable. In addition to the published phase diagrams, investigations have been carried out on portions of the iron-nitrogen system. Bramley and Haywood determined the composition and temperature of the iron-iron nitride eutectoid. The maximum solubility of nitrogen in a iron was investigated by Portevin and Seferian10 and by Diikstra. 11 Several investigators have determined the crystal structure of the various iron-nitrogen phases. In fact, Eisenhut and Kaupp6 and Hägg7 based their entire phase diagrams on the results of such studies. Epstein' and Emmett12 reported lattice-parameter measurements on the E (hexagonal close-packed) phase. Osawa and Iwaisumi13 also studied the change in lattice parameters of the a, ? and E phases with nitrogen content. Brill" and Hägg7 showed that the y' phase has an ordered structure, and Hendricks and Kostingsl5 suggested a structural relation between the E and phases. In a recent investigation Jackl6 arefully studied the super-lattice reflections from the y' and phases. Experimental Procedure A large variety of experimental methods has been used by previous investigators in studying the iron-nitrogen system. These methods include thermal analysis, microscopic examination, X ray diffraction, magnetic measurements, dilatometric analysis and anelastic experiments. Thermal analysis is of low accuracy in determining changes in the solid state. This accuracy is further decreased for iron-nitrogen alloys since composition changes will occur during heating or cooling unless extreme care is taken to use a proper atmosphere. Metallographic methods are of small value . because homogeneous iron-nitrogen alloys of sufficient size can be produced only with great difficulty. The dilatometric method is open to the same objections as thermal analysis in that changes in composition may occur during heating and cooling. Lattice parameter measurements by X ray diffraction can be used satisfactorily for determining phase boundaries if cooling is fast enough to prevent structural changes. In view of the limitations of the various other techniques two methods only were adopted in this investigation, (1) X ray diffraction measurements, and (2) a controlled nitrogenizing method. The second method is an innovation for investigating the iron-nitrogen system, and will be described at length. Materials: All iron-nitrogen alloys were prepared from carbonyl iron powder of the analysis shown in table I. The average particle size was about 20

Jan 1, 1951

By G. S. Hume

RECENT developments in the Turner Valley gas and oil field, 40 mi. southwest of Calgary, Alberta, have indicated a large producing crude-oil area. Drilling be¬gan in Turner Valley in 1913 but no major developments took place until the fall of 1924, when Royalite No. 4 well at a depth of 3740 ft. in the upper part of the Paleozoic (Mississippian) limestone obtained a production - of 20,000 M cu. ft. of gas with a content of about one imperial gallon of naphtha (73° A.P.I.) per M cu. ft. This well produced as much as 600 bbl. of naphtha per day, and until abandonment in 1934 produced 911,313 bbl., which together with the gas sold was valued at about $5,000.000.

Jan 1, 1937

By J. M. Lohr

THE characteristics and uses of thermocouples of platinum and the platinum alloys being so well known, this paper will be confined to base-metal couples. During the past decade, there has developed a strong demand for thermocouples made of metals cheaper than the platinum alloys, and suitable for industrial heat measurements. Much research has been clone but only a very limited number of alloys have been found to possess the necessary characteristics for general technical use. In the development of thermocouple alloys it is necessary to consider the following points: The electromotive force and temperature relations; permanency or constancy; reproducibility; manufacturing difficulties; durability; and accuracy in use. The electromotive force developed by the thermocouple should increase with the rise of temperature according to some definite law. It is desirable that the electromotive force should vary directly with the temperature difference of its junctions, in other words, giving a curve linear or nearly so. It is also desirable that the resulting electromotive force be as large as possible for any given range of temperature, thereby insuring greater accuracy of readings.

Jan 9, 1919

By W. W. Anderson, D. G. Girton

The photoluminescence of Pr, Nd, Ho, Er, Tm, and Yb in CdS, and Ho, Er, Tm, and Yb in ZnSe has been observed from crystals Prepared by diffusion using rare earth metals and an excess chalcogen pressure. For a given temperature, time, and chalcogen pressure the spectral characteristics were very reproducible from run to run, and the emission intensity for Nd, Er, and Yb in CdS was as high or higher than the best vapor phase doped crystals we have grown. For a few rare earths it was found that certain conditions of diffusion tend to yield optimum rare earth emission intensity with respect to the background lattice emission. Photoluminescence measwements of Yb in CdS as a function of depth gave a profile which was neither a Gaussian nor complementary error function. Part of the profile appears to arise from a fast component of the diffusion and the other part from a slow diffusing component. At 960°C and 33 atm S pressure, a com -plimentary error function approximation of the slow diffusing component gave a diffusion coefficient of D = 1.3 x 10-9 sq cm per sec. MOST of the studies of emission from rare earth ions in II-VI compounds have been reported on crystals doped during growth,1,2 although Kingsley and Aven prepared ZnSe:Er by diffusion for paramagnetic resonance and fluorescence studies. Pappalardo and Dietz prepared CdS:Yb by diffusion, but they made optical absorption measurements., We know of no study on the properties of rare earth diffusion in the II-VI compounds. To date we have diffused Pr, Nd, Ho, Er, Tm, and Yb into CdS, and Ho, Er, Tm, and Yb into ZnSe and observed the rare earth emission spectra. For a given temperature and chalcogen pressure, the emission characteristics are very reproducible from run to run and for Yb, Nd, and Er in CdS, as good as the best crystals we had prepared by doping during vapor phase growth.2 The emission of Pr, Ho, and Tm has been observed in CdS prepared by diffusion for the first time. Previous attempts2 to prepare these later three materials by vapor phase growth were unsuccessful. The problem of obtaining reproducible characteristics in II-VI semiconductor compound work is well known.5 Not only is it difficult to reproduce results from one laboratory to another but it is sometimes difficult to reproduce results from one growth run to another under ostensibly identical conditions within one laboratory. This situation has been particularly bothersome in research on the luminescence of rare earth activated ZnS1 and Cds2. Crystals from one vapor phase growth run would show very strong rare earth line emission while crystals from a nearly identical run would show no rare earth emission. It was also observed on occasion that the intensity of the rare earth emission was not constant over the entire volume of a single crystal. MATERIAL PREPARATION AND INSTRUMENTATION Vapor phase grown boules of CdS were supplied by Dow Corning. This material was characterized by a free electron concentration of n - 3.5 x 1015 cm-3 and Hall mobility of 350 sq cm per v sec at room temperature. There were microscopic voids and decorated precipitates in some samples. The precipitates annealed out at diffusion temperatures but the voids remained. Single crystal rectangular samples of mm dimensions were sawed from the boules. The ZnSe was polycrystalline, UHP grade from Eagle-Picher. Poly-crystalline samples were sawed from the ingots. The samples were lapped, polished on one side, etched in a solution of 0.5 M K2Cr2O7 in 16 N H2SO4, and thoroughly washed in distilled water. A sample, excess sulfur (or selenium), and 5 mg of rare earth metal (turnings) were sealed in a 3.6 cm3 quartz ampoule at about 2 X 10-5 torr. The high chalcogen pressure used (1 to 30 atm) prevented thermal etching of the crystals and affected the diffusivity and solubility of the rare earth ions in the crystal lattice. For meaningful or reproducible results, it is thus necessary to specify the vapor pressure at which the diffusion was carried out. It is assumed that a negligible amount of the chalcogen was used in the formation of rare earth sulfides or selenides Our sulfur vapor pressure calculations are based on data assuming S2, S6, and S, molecules only in which case the equilibrium constants are given by6 where the pressures are expressed in torr. Selenium vapor consists of a mixture of Se2, Se4, Se6, and Se6 molecules. The selenium vapor pressure was calculated using equilibrium constants given by The status of the rare earth source during diffusion is unknown, i.e., the partial pressures of the rare earth metal and of the rare earth chalcogenides has not been determined. All emission spectra were recorded at 77°K on a Perkin-Elmer model 98-G spectrometer using a 640 line per mm grating. No correction was made for the spectrometer and detector spectral sensitivity. Excitation was by means of an XBO 1600 w xenon arc

Jan 1, 1970

By O. C. Wheeler

The activity in exploration and in the acquisition of prospective oil lands that reached such a high level in Colombia during 1936 gained momentum and reached unprecedented proportions during 1937. Both national and private lands were taken up. In the Magdalena Valley above Puerto Berrio, leases on large tracts of private lands are held by Richmond (Standard of California), Shell and Texas. Tropical also owns leases covering a block of acreage in this area near Honda. From Puerto Berrio to El Banco most of the acreage is of national ownership, and concessions covering parts of this area have been granted to Tropical, Socony Vacuum, Shell and others, while applications for additional concessions are pending. Latterly leases on private lands below the Lebrija River have been taken out by Shell and Richmond. In the drainage basins of the Meta and Guaviare Rivers of the Llanos region of eastern Colombia, several of the major companies have carried on geological exploration and it is understood that some private properties have been leased or optioned. Under Colombian law, subsoil rights are reserved to the nation on all lands that passed from Government ownership after Oct. 28, 1873. Private titles antedating that day carry both surface and subsurface rights. Conditions under which lands may be acquired, explored and

Jan 1, 1938

By James Douglas

Discussion of the paper of James Douglas, presented at the New Haven meeting, February, 1909, and published in Bulletin No. 29, May, 1909, pp. 439 to 451. JAMES DOUGLAS, New York, N. Y. (communication to the Secretary*) :-In my paper on the Conservation of Natural Resources, I referred to the slow replacement of bee-hive ovens by the by-product ovens as a most notable instance of waste. And I quoted from Mr. Parker's report for .1906 an explanation given by him in accounting for the small production of by-product coke. It was that the markets for the by-products of the coke-ovens was so limited that some of the ovens constructed were out of operation. His report on the manufacture of coke in 1908 1 does not record an improvement, and attributes the strange fact that we alone, of all the industrial peoples, delay the adoption of this cardinal improvement from the continuance of the same almost inexplicable cause. To quote again from his report, lie says (p. 241): "The year 1908 was not marked by any notable gain in the construction of by-product coking plants, though some new work was done. There was a net increase of 115 in the number of completed ovens in 1908 over 1907, the totals for the two years being, respectively, 3,892 and 4,007. The additional equipment consisted of 140 Koppers regenerative ovens built at Joliet, I11., by the United States Steel Corporation, but this increase was partly offset by the dismantling of Y5 Semet Solvay ovens at Sharon, Pa., the net gain being 115 ovens. Included in the total of 4,007 completed ovens in 1908 are 152 Newton-Chambers ovens at Vintondale, Pa., but as no recovery of by-products was made at this plant in 190S, the production of coke is included with that from beehive ovens. The 56 ovens of the same type at Pocahontas, Va., have not been in practical operation since they were first. installed. In addition to these there was one other by-product plant of 120 ovens. Oat. was not operated during the year. The number of retort ovens producing coke in 1908 was 3,679, as compared with 3,811 active ovens in 1907." In describing the anomaly he says (p. 249): It has been contended that the development of the by-product coking industry would have shown more rapid progress if markets for the by-products were * Received Feb. 2, 1910. Mineral Resources of the United States for 1908, Part I1., U. S. Geological Survey (1909).

Apr 1, 1910

By W. A. Vine

WHEN a hole is made in a stressed solid, such as rock pierced by mine openings, equilibrium of the solid is destroyed. To re-establish that equilibrium the stress condition in the rock surrounding the opening becomes rearranged. This rearrangement may or may not develop local stresses in the vicinity of the opening which exceed the elastic strength of the rock. Since stability of the opening depends, therefore, on the strength of the naturally occurring rock surrounding the opening, this rock is an engineering material of construction, and all rock affected by the associated opening or system of open- ings may be considered a structure. The term invert is chosen to describe the formation of the structure —built from the inside, as it were, and a consequence of mining rather than an entity built for a purpose. By definition, an invert structure is formed when openings are made underground and is composed of that material on the solid side of a rock-air interface wherein the stress condition is affected by the associated opening or system of openings. The shape of an invert structure is never clearly defined; the skin of the structure may be mapped, and even described, but the boundary of the structure within the solid rock mass must be arbitrarily set. The name geomechanics is proposed to describe a branch of scientific knowledge which will encompass principles and working hypotheses for behavior and design of invert structures. It is foreseen that study

Jan 1, 1956