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By R. F. Mehl, C. S. Barrett, A. H. Geisler

THE complicated nature of the property changes that accompany age-hardening has made it necessary to reconsider and to elaborate the simple dispersion theory.1 It has been apparent for some time that more direct information is needed concerning the atomic mechanism of precipitation from solid solution if the theory of age-hardening is to be developed past a purely qualitative stage.‡ Fortunately, in recent years information has been developed which allows us to trace in detail the lattice changes accompanying the process of precipitation from solid solution. This information relates chiefly to the sequence of the several stages of lattice alteration by which the matrix lattice is transformed to the equilibrium precipitate lattice, and permits reasonable inferences to be drawn concerning the states of internal strain that accompany these stages. This information is most complete for the solid solution of copper in aluminum. The equilibrium precipitate is the ?' phase," CuA12." This forms in plates, parallel to the {100} matrix planes. The atom pattern and atom spacing on the plane in ?' lying parallel to this plane are roughly similar to those opposite it in the matrix.' The formation of ?', however, is preceded by the formation of a transition lattice ?', which again lies parallel to the matrix {100} plane, but in this case the matching of atom pattern and spacing across the matrix-precipitate interface is nearly perfect; thus there is lattice coherency across the interface and the interface is a plane of separation in only a very limited sense.4-8 Particles of ?' may be recognized microscopically and form a well-defined Widmanstätten figure.* The ?' lattice is recognized by the occurrence of diffraction lines on powder photograms or of spots on Laue photograms which may be analyzed in the usual ways to determine the lattice type and the lattice spacings. Very recent research 6.7,1 has shown, however, that streaks occur on the Laue photogram at an earlier point in time during the aging process. These streaks have been attributed to a preferential clustering of copper atoms into small platelike elements of only a few atoms in thickness and a few hundred atoms in diameter, probably of the composition of "CuA12," which may be designated as Guinier-Preston zones or aggregates.1 It is difficult if not impossible to determine the lattice type and lattice spacing in these aggregates. It is possible1 that these aggregates are in fact merely ?' in a high state of dispersion; the inclination to argue this is strong, as we shall see later. Never-

Jan 1, 1941

By S. B. Christy

The practice of the cyanide-process of gold-extraction has brought to light many important contradictions of familiar chemical analogies, which still obscure both the theory and the practice of the art with distinctions subtler and more difficult to make or follow than those which delighted the heart of the old-time metaphysician. Yet Nature herself has drawn these distinctions; and if we hope to succeed in this modern search for the Golden Fleece, we must be able to follow her through the winding labyrinth. There are so many phases of this question that I shall attempt to touch on only one of them at this time, but it is one that lies at the root of many others. In reviewing my paper on " The Solution and Precipitation of Cyanide of Gold,"* Mr. E. B. Wilson contends† that" in the solution of gold by means of alkaline cyanides the various reactions are determined, as to their order and intensity, by the relative position of the elements concerned in the electro-chemical series, or series of voltaic tension." In a modified form this statement is probably true. That is to say, the difference of electrical potential in any closed electrical circuit determines the nature of the reactions which ensue. But the matter is not so simple as Mr. Wilson assumes. Recent investigations show that the order of the metals in the electro-chemical series depends not only on the nature of the elements themselves, but also on the chemical composition of the solution in which they are placed; its degree of concentration; its temperature; and, in the case of gases, on the pressure. Unless all these conditions are taken into account, inferences drawn from the electro-chemical series are likely to prove more

Jan 1, 1901

By Arthur C. Spencer

HAVING suggested magmatic waters as the probable agents of vein- and ore-deposition in southeastern Alaska in a paper entitled, The Geology of the Treadwell Ore-Deposits,1 it is with particular interest that I note W. Lindgren's application of the hypothesis of igneous emanations to the gold-quartz veins of Victoria and of California.2 Mr. Lindgren says: "In the above paragraphs I have repeatedly called attention to remarkable similarities in vein-filling and metasomatic action between the Victorian quartz veins and those of Sierra Nevada. Another striking similarity is that in both of these regions the veins were formed just after the intrusions of vast masses of granite or dioritic magma into crumpled and compressed sediments. I am convinced that these similarities are due to closely similar modes of formation. With some confidence, I would formulate the hypothesis that the gold and the quartz in this type of veins have been deposited chiefly by `eruptive after-effects;' in other words, chiefly by hot ascending waters originally contained in the granitic magma and released from it by decreasing pressure, due to its eruption into the upper parts of the lithosphere. It is quite possible that atmospheric waters may have played a certain part by aiding the precipitation and by effecting certain forms of concentration in the deposits." There are many reasons for extending this hypothesis to southeastern Alaska. This region and the Sierra Nevada belt of California are undoubtedly parts of one geologic province, throughout which the main events of geologic time are evidenced by identical or closely similar records in the rocks. Our knowledge of the former region is still fragmentary, to be sure, but the origin-dates of the most prominent features of

Jan 1, 1913

By R. P. Marshall, L. P. Costas

The solid solubility of lithium in aluminum was determined by two independent techniques, electrical resistivity and microhardness, and the results are in close agreement. The solubility limits X-ray diffraction studies of the intermetallic compound LiAl indicate that its composition is nearly independent of temperature when in equilibrium with the terminal solid solution of aluminum. THE investigation of the aluminum-rich portion of the aluminum-lithium system at the Savannah River Laboratory was prompted by the observation that over-aged alloys consistently differed from the equilibrium states predicted by the latest published diagrams. Chemical analyses of these alloys showed their impurity contents to be quite low; therefore, the results obtained should have very nearly coincided with true equilibrium. A survey of the literature disclosed that previous studies had been made with metallographicig or electrical resistivity methods,4'5 but that agreement between results and technique was poor as evidenced in Fig. 1, which also includes the present results for comparison. The discrepancies have been attributed to impurities,3 and this is undoubtedly true in the early work.1'4'5 The latest Studies,''~ conducted with starting materials of higher purity, employed metallographic analysis, a technique that is quite sensitive to local homogeneity and depends strongly on subjective interpretation. In the present work the problem of defining solubility limits was approached in two ways. The first measured a physical property, electrical resistivity, at the equilibrium temperature. The second, a micro-hardness characterization of a diffusion zone, is a room temperature evaluation of a mechanical property under conditions removed from equilibrium. A close correlation between two such basically different approaches would strongly justify confidence in the results. I) MEASUREMENT OF SOLUBILITY OF LITHIUM IN ALUMINUM BY ELECTRICAL RESISTIVITY Experimental Procedure. Alloys for electrical resistivity measurements were made by melting and

Jan 1, 1962

By F. H. Buttner, H. Udin, J. Wulff

Using a modified Udin, Shaler, and Wulff technique, the surface tension of gold Udin, purified helium was found to be 1400 ± 65 dynes per cm for the temperature range 1017° to 1042°C. IN the original Udin, Shaler, and Wulff technique for measuring the surface tension of copper: variously weighted wires were allowed to extend or contract in a copper cell held at elevated temperatures in vacuum. By plotting stress vs. strain for a wire array in one test, the stress at zero strain is obtained. This is the point where the contractile forces resulting from surface tension are balanced by the applied load, according to the expression: y = e=o r [1] where y is the surface tension in dynes per cm; a,,,, the stress at zero strain in dynes per cm; and T, the radius of the wire in cm. The assumption that the wires deform viscously permits the drawing of a straight line through the points on the stress-strain plot. Justification of the assumption has received further experimental support recently.'-' The presence of grain boundaries in the wires requires a correction to the original expression used." Thus: y = d4=T [l- (dl) (ar)Y1 [2] where, n/l is the number of grain boundaries per unit length, and a, the ratio of grain boundary tension to free surface tension. Alexander, Kuczynski, and Dawson in studying the creep of gold wire in vacuum were unable to obtain reproducible values of the surface tension of gold. In plotting stress vs. strain for progressively longer times, they found that the stress at zero strain drifted with time from positive stress values to negative values. Similarly, for the surface tension of silver, reproducible values were obtained only when a purified helium atmosphere was substituted.' Evidently the evaporation rate of silver in vacuum is too high at the temperatures employed to obtain solid-gas equilibrium even in a similar metal enclosure. Thus reproducibility of results is lost. Experimental Procedure The experimental procedure was much the same as that originally developed by Udin, Shaler, and Wulff with a few modifications and improvements. For greater accuracy in strain measurements, knots gave way to cut gage marks as shown in Fig. 1. These were made with a hand-driven lathe in which razor blades serv'ed as cutting tools. Also a more precise cathetometer with a screw accurate to 0.00015 cm was used. The tests were conducted in an atmosphere of purified .helium rather than in vacuum in order to avoid possible evaporation difficulties. Five mil wire of high purity gold (99.98 pct) was used. After cutting in the gage marks, each wire of a series of about 12 was differently loaded by welding a gold ball to one end. This was done by dipping the end of the wire in a cooling gold droplet, previously melted on a charcoal block with a No. 2 acetylene torch. The other end of the wire was strung through a hole in a gold lid and twisted over the edge to hold the wires fixed and in suspension from the lid. The lid and mounted wires were then dipped in pure ethyl alcohol to dissolve any skin oils and dirt on the surface of the wires due to handling. Finally the lid was put in place on an alundum crucible lined with gold so that the wires hung freely within the gold-lined chamber. This whole assembly was next heated in a quartz nichrome wound tube furnace and heated for a few minutes at 600°C to soften the wires. After this anneal the wires were easily straightened with tweezers. The wire assembly was finally annealed 10" to 25°C above the subsequent test temperature for 2 hr. This treatment allowed the grains to grow to equilibrium size and shape. After the anneal, the lid was mounted in front of the cathetometer. The gage length was measured by sighting the 40 power microscope on the upper lip of the lower gage mark for the first reading, then traveling up to the lower lip of the upper gage mark for the final reading. This procedure was repeated four times to give an average gage length value. In this manner the annealed gage length and the final gage length could be measured to determine the strains. During all measurements, grain counts were made.

Jan 1, 1952

By W. C. Peters, M. W. Pullen, C. A. Bays

During the past three and a half years considerable improvement in the techniques of solution extraction of salt has been made by the use of wells which are cross-connected by hydraulic fracture at the base of the salt. Fracture is initiated by the application of hydraulic pressure. Underreaming and perforating techniques are used to control initiation. The fracture is then extended by continuous pumping until a pressure communication is obtained. Pressure communication is followed by washing-through to obtain a low-pressure connection. Well construction using non-shrinking cements that will bond with the salt and with associated strata is essential to the process. The connecting procedure described permits solution to attack the salt deposit from its base upward, thereby permitting greater recovery, fewer well repairs, better saturation of brine, and overall economy of development and operation. The fracture method of cross-connection requires special pumping of the fluid and is limited by present experience to initial well spacings up to about 1200 feet. The method has been used in bedded salts and is applicable for wells in salt domes. Since spring of 1956, new developnents in salt extraction wells have followed procedures substantially different from those in prior use. Although multiple well systems, connected either by the natural consequence of the solution process or by undercutting under protective pads, have been used previously, the past three and a half years have brought about new designs and new operation procedures based on cross-connection of the wells using hydraulic fracture. To date these techniques have been applied largely in the bedded salt deposits of Michigan, Ontario, Ohio, West Virginia, and New York. To the writers' knowledge they have not been used in salt dome wells. The methods have not yet been in use for a sufficient period to permit any statistical comparison with the older methods. It is evident from experience to date that the methods result in higher recoveries, lower capital and operating costs, better saturation of produced brine, reduced well maintenance and repair, and in considerably fewer production units to insure

Jan 1, 1961

By A. A. Stripling

The Cretaceous limestone wells of the Mara/Maru-caibo Dist. of Venezuela are extremely prolific producers. To maintain production on cessation of natural flow, large scale gas-lift operations were commenced involving high production rates on caring Flow. For the design of these gas-lift installations it was essential to have some knowledge of the pressure gradients involved in casing flow, so that the required injection pressures, optimum gas injection raws, etc., could be forecast. This paper presents a method of calculating these annular pressure gradients. Basically the method makes use of an energy balance equation coupled with an empirical energy loss factor derived from field data. The calculations have been put in a form suitable for "punch card-type" calculating machines. A set of gradient curves for Mara/Maracaibo conditions covering flow rates up to 12,000 B/D, and GOR's of 500 to 2,000 cu fd/bbl is presented. From these curves the flowing BHP can be predicted from surface data and the vertical pow performance under varying conditions of gas injection can be estimated. The method has been applied to La Paz and Mam gas-lift operations for over three years and has given consistently accurate results. INTRODUCTION The Cretaceous limestone fields of the Mara/Maracaibo area in Venezuela are characterized by the presence of widely distributed fissure systems. Under these conditions individual wells frequently have extremely high potentials and such wells are generally flowed on the casing-tubing annulus in order to reduce the pressure loss in vertical flow. To maintain production on cessation of natural flow, an extensive gas-lift system was planned. As a first approach to this gas-lift design problem, an attempt was made to construct a set of empirical flowing gradient curves from the available subsurface pressure data. Such a method has been used successfully for tubing-flow conditions in California by Gilbert'. Unfortunately, the empirical construction of casing-flow gradient curves presents additional difficulties, as pres- sure bombs cannot bc run in the casing-tubing annulus against high rates of flow. Thus, the Full flowing gradients cannot be defined by actual measurement and the best that can be done is to obtain spot pressures at the tubing shoe. Under these conditions a vast accumulation of BHP data is required to construct a set of gradients. To the La Paz and Mara fields the majority of the available flowing pressure measurements fall into a relatively narrow GOR range, in the neighborhood of the solution ratio. While there appeared to be reasonable prospects of constructing gradient curves for this limited range, measurements at higher GOR's, which were of major interest for gas-lift operations, were relatively few and the prospects of constructing empirical curves cor~spondingly remote. As an alternative approach, the possibilities of a mathematical analysis of vertical flow conditions were investigated. May and Laird2fV n 1934 presented an excellent analysis of the vertical-flow conditions in the Anglo-Iranian Oil Co.'s fields. Their analysis was based on an energy-balance equation and calculated the losses due to kinetic energy, friction and slippage separately. By combining these losses with the total calculated available energy, the required depth-pressure traverse could be deduced. On applying the method to La Paz conditions, good results were obtained for tubing flow at high tubing-head pressures. However, for lower wellhead pressures (300 psi and under) the discrepancy between calculated and measured values increased appreciably. It was considered that this was probably due to energy losses caused by slippage or liquid hang-up in a continuous gas phase, for which it was difficult to visualize any analytical approach. In 1952 Poettmann and Carpenter4 presented a method of pressure gradient calculation which, while based on an energy-balance equation similar to that employed by May and Laird, made no attempt to evaluate the various components making up the total energy loss resulting from irreversibilities of flowing fluids. Instead, they proposed a method of analysis which assumed that all significant losses for multiphase flow could be correlated in a form similar to that of the Fanning equation for frictional losses in single-phase flow. They then derived an empirical relationship linking measurable field data with a factor which, when applied to the standard form of the Fanning equation, would enable the energy losses to be determined. The total available

By David P. Hale

THE Cartersville barite district is near Cartersville, Ga., in the southeastern part of Bartow County, about 43 miles northeast of Atlanta. The area over which active mining is being done extends about six miles in a northeasterly direction and is about three miles wide. Barite production in Georgia began about 1907,1but the existence of the mineral was known much earlier. At present four companies are operating washing plants and three other plants are operating on leases from those companies. The chief impurities in the ores are silica and iron oxide. The silica is easily washed and jigged out and gives little trouble. Any gravity separation between the iron and the barite is generally poor, owing to the slight difference in specific gravity. Two operators have turned to magnetic separation as the solution to the problem and have made remarkable improvements in the finished product. By very close sizing prior to jigging, the separation between iron and barite has been greatly improved. In some localities manganese occasionally appears as an impurity, but is fairly easy to eliminate by gravity methods. A considerable percentage of iron and silica is eliminated by being broken free in crushing. Until methods for the recovery of fine ore were introduced a minimum of crushing was done, but modern methods allow more than formerly. The depression years brought about the need for increased recovery of ore handled on the part of the producers and a demand for a higher grade of product on the part of the buyers. Improvements in milling and mining practice have had a far greater effect, however, than merely the production of a better grade of ore with greater recovery. They have opened for mining large areas that a few years ago were considered noncommercial deposits because of their inaccessibility and their high iron content. It is no exaggeration to say that the new methods have more than doubled present known reserves of barite ore of economic value.

Jan 1, 1938

By David P. Hale

The Cartersville barite district is near Cartersville, Ga., in the southeastern part of Bartow County, about 43 miles northeast of Atlanta. The area over which active mining is being done extends about six miles in a northeasterly direction and is about three miles wide. Barite production in Georgia began about 1907,' but the existence of the mineral was known much earlier. At present four companies are operating washing plants and three other plants are operating on leases from those companies. The chief impurities in the ores are silica and iron oxide. The silica is easily washed and jigged out and gives little trouble. Any gravity separation between the iron and the barite is generally poor, owing to the slight difference in specific gravity. Two operators have turned to magnetic separation as the solution to the problem and have made remarkable improvements in the finished product. By very close sizing prior to jigging, the separation between iron and barite has been greatly improved. In some localities manganese occasionally appears as an impurity, but is fairly easy to eliminate by gravity methods. A considerable percentage of iron and silica is eliminated by being broken free in crushing. Until methods for the recovery of fine ore were introduced a minimum of crushing was done, but modern methods allow more than formerly. The depression years brought about the need for increased recovery of ore handled on the part of the producers and a demand for a higher grade of product on the part of the buyers. Improvements in milling and mining practice have had a far greater effect, however, than merely the production of a better grade of ore with greater recovery. They have opened for mining large areas that a few years ago were considered noncommercial deposits because of their inaccessibility and their high iron content. It is no exaggeration to say that the new methods have more than doubled present known reserves of barite ore of economic value.

Jan 1, 1942

By David P. Hale

The Cartersville barite district is near Cartersville, Ga., in the southeastern part of Bartow County, about 43 miles northeast of Atlanta. The area over which active mining is being done extends about six miles in a northeasterly direction and is about three miles wide. Barite production in Georgia began about 1907,' but the existence of the mineral was known much earlier. At present four companies are operating washing plants and three other plants are operating on leases from those companies. The chief impurities in the ores are silica and iron oxide. The silica is easily washed and jigged out and gives little trouble. Any gravity separation between the iron and the barite is generally poor, owing to the slight difference in specific gravity. Two operators have turned to magnetic separation as the solution to the problem and have made remarkable improvements in the finished product. By very close sizing prior to jigging, the separation between iron and barite has been greatly improved. In some localities manganese occasionally appears as an impurity, but is fairly easy to eliminate by gravity methods. A considerable percentage of iron and silica is eliminated by being broken free in crushing. Until methods for the recovery of fine ore were introduced a minimum of crushing was done, but modern methods allow more than formerly. The depression years brought about the need for increased recovery of ore handled on the part of the producers and a demand for a higher grade of product on the part of the buyers. Improvements in milling and mining practice have had a far greater effect, however, than merely the production of a better grade of ore with greater recovery. They have opened for mining large areas that a few years ago were considered noncommercial deposits because of their inaccessibility and their high iron content. It is no exaggeration to say that the new methods have more than doubled present known reserves of barite ore of economic value.

Jan 1, 1942

By James Barr

Geology and Mineralogy1 TENNESSEE phosphates are commercially divided into three varieties: Brown, blue and white. The first two only are now of commercial importance. The white phosphates of Perry county are not being mined at present owing to their pockety occurrence. The white phosphate is Fig. I.-DEPOSITS OF 75 PER CENT. BROWN PLATE ROCK UNDERLAIN BY SAND. the highest grade of the three varieties, running often more than 90 per cent. tricalcium phosphate. The brown rock is found in three varieties, grading from the dense almost vitreous gray rock, 76 to 82 per cent. tricalcium phosphate, down

Jan 9, 1914

By Ted C. Briggs

Nitrogen exists in two broad categories commonly designated as elemental nitrogen and fixed nitrogen. Elemental nitrogen is found in nature as a diatomic molecule and constitutes about 78%, by volume, of the earth's atmosphere. Fixed nitrogen is a common term used for nitrogen that is chemically bound to other elements. Although elemental nitrogen is very abundant, nonleguminous plants cannot utilize nitrogen unless it is in the chemically combined form. The content of this chapter is confined to fixed nitrogen since the uses and properties of elemental nitrogen and the fixed nitrogen compounds are different. Bacteria associated with legumes are able to fix atmospheric nitrogen, but not to the extent or in the locations required by modem agriculture. The need to use fertilizers containing fixed nitrogen compounds to grow food crops has been recognized for hundreds of years, and from antiquity farmers have used organic wastes such as animal manures, vegetable wastes, sewage sludge, fish scraps, etc., containing these compounds for fertilizers. The organic materials have a low nitrogen content, however, and cannot support large-scale food production. Known commercial-size deposits of natural nitrates containing much higher nitrogen content exist only in Chile, and the possibility of the discovery of other significant deposits is remote. The Chilean deposits were the major source of nitrogenous fertilizers until about 1913, when the Haber-Bosch process for the production of synthetic ammonia was developed. In the Haber-Bosch process, nitrogen reacts with hydrogen, at high temperatures and pressures and in the presence of a catalyst, to form ammonia. At present Chile is the only country in the world with a nitrate mining industry, and, although the mining of natural nitrates is an important industry in Chile, natural nitrates are relatively unimportant, worldwide, because of the adoption of fixed nitrogen processes. The relative amount of the world demand for fixed nitrogen that is derived from natural nitrates has declined in recent years and will continue to decline. Modern farmers are sophisticated in economic calculations such as cost to benefit ratios and, for the most part, they purchase plant nutrients which give the highest return on their investment. Natural nitrates cannot compete on a fixed-nitrogen cost basis with anhydrous ammonia and its derivative products. In a limited sense, the fixed nitrogen industry is mining the air. Modern plants use air, water, and, in most cases, natural gas to produce the ammonia that is now the key building block of the fixed nitrogen industry. To present an accurate picture of the industry, this chapter on nitrogen follows a format somewhat different from that of other chapters in this volume.

Jan 1, 1975

By William B. Plank

ENGINEERING students to the number of 73,269 had been enrolled in United States and Canadian schools on Nov. 5, 1945, but, as shown in the following tables, even this sizable number will not greatly remedy the 150,000 deficit reported by Vannevar Bush, director of the U. S. Office of Scientific Research and Development, to exist in the engineering and scientific man-power supply. These figures were received in advance from the Society for the Promotion of Engineering Education, and are given in detail in the January 1946 issue of the Journal of Engineering Education. Although the enrollment on Nov. 5 was an increase of 76% over the low of 41,632 in 1944-45, it was still 36% below the peak enrollment in 1941-42 of 115, 228. These figures include both undergraduate students and graduate students in the schools of the United States and Canada and are therefore comparable. As was to be expected, almost half of this enrollment is in the first or freshman year and 25% of the total are veterans. Also, 1,850, or about 2.5%, are women. A measure of the seriousness of the engineering graduate supply in these two countries is indicated by the trend of the number of first degrees that have been conferred during this period of scarcity:

Jan 1, 1946

By G. T. Hahn

On the basis of the recommendation of Lovell, Vogel, and Wernick,&apos; Fry&apos;s reagent*2 was recently c) if decoration of the dislocations by carbon or nitrogen atoms is a factor in the etch pitting. Experiments were performed with samples of a commercial 1020 steel, a vacuum-melted iron (C - 10 to 15 ppm, 0 - 20 to 50 ppm, N < 2 ppm), both annealed 4 hr at 1100°C, and a zone-refined iron (C - 3 to 5 ppm, 0 - 10 ppm, N < 1 ppm ) in the as-cast condition. Saomple surfaces were prepared by grinding to 600A grit and electropolishing. Initially, effects of etching the steel with modifications of the basic Fry composition were examined. It was found that increasing the alcohol or HC1 concentratior~ retarded dislocation pitting; reducing the acid content promoted secondary pitting. Cooling the reagent and the sample did not improve the quality of the etch pits. Best results were obtained with freshly prepared reagent modified by increasing the CuC12 content to 15 g. This composition was used in subsequent experiments. Annealed samples were etched 10 to 15 sec; cold-worked samples —2 to 5 sec.

Jan 1, 1962

By Reno H. Sales, Charles Meyer

AT Butte, successive zones of sericitized and argillized quartz monzonite occur around every ore-bearing fracture regardless of its size, attitude, or relative age. The two types of alteration always occupy the same relative positions; sericite adjacent to the ore-bearing vein, clay minerals always between the scricitized rock and fresh quartz monzonite, except where overlap of alteration effects between adjacent fissures has eliminated the lower grade mineralogical products, as is the case in much of Butte&apos;s Central zone of pervasive sericitization. As long as active circulation continued in the channel, each zone migrated away from the fissure, that is, it grew at its outer edge and simultaneously receded at its veinward edge because of encroachment by the next innermost zone. The different mineralogical and chemical responses within the wall rocks to the attack by the ore fluid are dependent not on a drastic about-face change of composition of the fluid in the channel relative to its ability to alter the quartz monzonite but on continuously varying conditions of physico-chemical environment within the wall rock outwardly from the vein.&apos; Introduction From the economic viewpoint it is highly desirable that much effort be expended for the purpose of increasing our knowledge of ores and their origin. It has been the observation of the senior writer, many times expressed, that the mining companies have spent too little money in research on the geology of nature&apos;s deposits of copper, lead, and zinc, which we know to be of limited extent and which, when exhausted, must be replaced by new discoveries. Experience at Butte and elsewhere has forced the conclusion that observation and mapping in the field must be supplemented by laboratory work if we are to arrive at a reasonably correct understanding of the geology of ore bodies and their environments. It is only through the medium of such correct understanding of geology that we shall be able to accomplish the maximum toward aiding mine operations and at the same time provide a proper background for field examination work whether it be geological or geophysical. The Anaconda Copper Mining Company&apos;s answer to the need above expressed has been to equip a geological laboratory at Butte. The reason why Butte was selected is obvious, for situated there is one of the world&apos;s largest and geologically most interesting concentrations of copper and zinc. Furthermore, because of the great extent of underground workings both laterally and vertically, the opportunities for observation and study of ore occurrences probably are unequaled anywhere. The laboratory was established with five principal objectives in view. These were: 1. As an aid to Anaconda Company mine operations at Butte and elsewhere, this work to supplement that of the mine geologists. 2. To aid in acquiring as complete an understanding as possible of the behavior of Butte veins and ore bodies laterally and in depth.

Jan 1, 1949

By Charles Meyer, Reno H. Sales

AT Butte, successive zones of sericitized and argillized quartz monzonite occur around every ore-bearing fracture regardless of its size, attitude, or relative age. The two types of alteration always occupy the same relative positions; sericite adjacent to the ore-bearing vein, clay minerals always between the scricitized rock and fresh quartz monzonite, except where overlap of alteration effects between adjacent fissures has eliminated the lower grade mineralogical products, as is the case in much of Butte&apos;s Central zone of pervasive sericitization. As long as active circulation continued in the channel, each zone migrated away from the fissure, that is, it grew at its outer edge and simultaneously receded at its veinward edge because of encroachment by the next innermost zone. The different mineralogical and chemical responses within the wall rocks to the attack by the ore fluid are dependent not on a drastic about-face change of composition of the fluid in the channel relative to its ability to alter the quartz monzonite but on continuously varying conditions of physico-chemical environment within the wall rock outwardly from the vein.&apos; Introduction From the economic viewpoint it is highly desirable that much effort be expended for the purpose of increasing our knowledge of ores and their origin. It has been the observation of the senior writer, many times expressed, that the mining companies have spent too little money in research on the geology of nature&apos;s deposits of copper, lead, and zinc, which we know to be of limited extent and which, when exhausted, must be replaced by new discoveries. Experience at Butte and elsewhere has forced the conclusion that observation and mapping in the field must be supplemented by laboratory work if we are to arrive at a reasonably correct understanding of the geology of ore bodies and their environments. It is only through the medium of such correct understanding of geology that we shall be able to accomplish the maximum toward aiding mine operations and at the same time provide a proper background for field examination work whether it be geological or geophysical. The Anaconda Copper Mining Company&apos;s answer to the need above expressed has been to equip a geological laboratory at Butte. The reason why Butte was selected is obvious, for situated there is one of the world&apos;s largest and geologically most interesting concentrations of copper and zinc. Furthermore, because of the great extent of underground workings both laterally and vertically, the opportunities for observation and study of ore occurrences probably are unequaled anywhere. The laboratory was established with five principal objectives in view. These were: 1. As an aid to Anaconda Company mine operations at Butte and elsewhere, this work to supplement that of the mine geologists. 2. To aid in acquiring as complete an understanding as possible of the behavior of Butte veins and ore bodies laterally and in depth.

Jan 1, 1949

By Wolfgang Gartner

METALLURGISTS engaged in the pulling of single crystals of germanium and silicon, and their zone purification and zone levelling for transistor and diode production, have found that the lifetimes of minority carriers in low resistivity samples tend to be shorter than in high resistivity material, although equal care is taken in the crystal preparation. In other words, it is more difficult to obtain long lifetimes in single crystals of low resistivity semiconductors. It is the purpose of this note to point out that this phenomenon follows directly from the Hall1 and Shockley-Read&apos; theories of lifetimes in semiconductors." In general, the recombination mechanism may be very complicated,&apos; but experiments seem to indicate that the simple formula2 for the lifetime of excess carriers given by n0 + n3 Pn + P1 T = Tpo,------------------+ Tjpu ----------------------- [ 1 ] nu + pn na+ + Pa is a good representation of the situation prevailing in transistor grade semiconductors. In this formula, no and pa are the equilibrium densities of electrons 6+ - E./ET and holes, n1 = N,e is the number of electrons E1- E2/KT in the conduction band, and p1 - N,e is the number of holes in the valence band, both for the case in which the Fermi level falls at the trap level, E1. N,. is the effective density of states in the conduction band; E1, the recombination level; E1, the lower edge of the conduction band; k, Boltzmann&apos;s constant; T, absolute temperature; N,., effective density of states in the valence band; and E,., the upper edge of the valence band. t,.,, denotes the lifetime of holes injected into highly n-type material, and The indicates the lifetime of electrons injected into highly p-type material. Eq. 1 holds for nondegenerate semiconductors in which only one recombination level is active and the charge in the recombination centers is neglected. It is further assumed that the number of injected ex-

Jan 1, 1957

By Philip McKenna

WHEN a new material becomes available to industry, it is useful to describe its properties as a guide to its most effective application; and when the new material may be produced in compositions having a series of graded properties, tests to select the combination of properties best adapted for various uses are helpful. The class of materials to be con-sidered in this paper are hard tool materials produced by processes of powder metallurgy from hard carbide constituents and various matrices of iron, nickel or cobalt, or alloys of them with tungsten, or tungsten and carbon. The customary use of carbide hard alloys is for metal-cutting tools; although wire-drawing dies, lathe centers, follow rests, grinding rests, burnishers, rolls, extrusion dies, measuring gauges and micrometers, and a number of other tools are also made with these hard alloys as the essen-tial wear-resisting parts. The properties and tests to be considered are those affecting these uses. In the development of tool, materials since the industrial revolution we have had carbon tool steels, Mushet steel, high-speed steels, stellites, and now cemented carbide compositions. For an understanding of the latter category of materials their properties and uses relative to the older and more familiar tool materials will be considered.

Jan 1, 1938

By W. R. Crane

MINING of the red iron ores of the Birmingham district has been carried on energetically during the past 50, years, and their development has created a large iron and steel manufacturing, center, the only important one in the South. The district produces approximately 10 per cent. of all the iron ore of the United States (80 per cent. of the Alabama ore mined is red ore) ; also, 43 of the 419 blast furnaces of the country are in the district tributary to Birmingham. The rapid growth of the district has been made possible through investigations that resulted in radical changes in furnace practice, and a still greater impetus will come from the study of the low-grade, high-silica ores, as a result of which they will be made amenable to treatment by concentration. Mining practice in this district has been comparatively simple because of the occurrence of the ore; but with the-rapid extension of the work-ings and the disturbed condition of the ore bed at some distance from the outcrop, more difficult conditions are encountered and the tendency is toward worse rather than better conditions. Should the high-silica ores of the lower bench of the Big Seam become available through beneficiation, mining practice will have to be modified to meet the new conditions, which will be rendered more difficult by the increased weight of cover that will exist at considerable distances from the outcrop. Support of workings will require greater attention and the efficient and economical operation of the mines will depend largely on the successful solution of the problems of working-and handling the ore.

Jan 9, 1924

By E. E. Mason

The Canadian National Railway system is completing construction of the first major tunnel in North America to use the coarse-aggregate (+ ½ -in.) shotcrete technique of primary support and lining. The tunnel was driven 29 X 20 ft in cross section, 10,760 ft long, passing under an industrial and residential area of Vancouver. With the exception of 1400 ft in soil (mainly impervious tills), the tunnel passes through a very young series of flat-lying sedimentary beds, to a large extent so incompletely consolidated as to fall apart on exposure. For a conventional steel-support system, it was estimated 8 WF, 28-lb steel should be used at 5-ft centers. Cost of erection including lagging would amount to $120 per linear ft of tunnel at 304 per lb. With 8-in. concrete cover on the steel, lining would cost $280 per linear ft at $82 per cu yd. Thus, minimum cost of support and lining would have amounted to $400 per linear ft. It is now estimated that at least 90% of the rock tunnel would have required support and 100 % required lining. Specified shotcrete support was 6 in. in the arch and 4 in. in the walls. Cost of this work was roughly $100 per linear ft. In addition, another $10-$12 per ft has been incurred in drainage and waterproofing wet areas and in measures to correct experimental and operational errors, thus finalizing the support as a lining (Fig. 1). The tunnel was driven three shifts five days weekly, no blasting being allowed by city ordinance between midnight and 7.00 a.m. A six-drill jumbo was used to drill a 10-ft round, 110 holes blasted three times daily. A 2-in. layer of shotcrete was applied to the newly blasted arch commencing within 45 min of blasting. This was done from a flying deck that extended over the muck pile from the jumbo (Fig. 2). Also during the mucking cycle, the preceding incomplete arch support was brought up to 6-in. specification. The walls were sprayed 4 in. thick during the drilling cycle (Fig. 3). The shotcrete machines and aggregate bins were mounted on the jumbo.

Jan 1, 1970