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By R. R. Van Valkenburch

IT has always seemed to me that mining methods are inventions that follow necessity. I have yet, to be connected with a property where the consultant who has been engaged has laid out a mining method that has been strictly adhered to through the life of the mine. Possibly there are exceptions. As a general rule, perhaps, the method becomes the result of sad experience. I suppose if a person were to attempt to measure the tendency to get away from shrinkage stoping, he would need to send out a questionnaire and expect to receive truthful answers, and, having compiled the results, I think we would find that throughout the country there would be but few cases where present value of product permits the old original so-called shrinkage method to be followed. The method that I had hoped to hear Mr. Fozard expound is strictly an adaptation of shrinkage. Cav-ings do not enter. It was developed by Mr. Fozard and his staff at the Beatson mine of the Kennecott Copper Corp., at, Latouche, Alaska. Stephen Birch, in the TRANSACTIONS in 1923, submitted a brief paper on the mining at Beatson. He stated that a new adaptation of shrinkage was being tried because, although at sur-face the copper .content had been relatively high, at lower levels, in the mine it had decreased.

Jan 5, 1927

By R. G. Vardiman, M. R. Achter

THERE has been interest recently in the conditions under which dislocation pipe diffusion may be observed. In order to extend the measurements to temperatures below Tm/2, where pipe diffusion becomes more important, a chemical sectioning technique was developed for silver single crystals which makes possible the removal of layers of 100A or less. The procedure is briefly as follows. Silver single crystals of 99.995 pct purity were cut in the form of discs t by 4 in., electropolished, and electropolated with Ag110 to about 1000A thickness. The thickness was determined by calibrating the activity with the weight of heavier platings, up to 10,000A. Both diffused and undiffused samples were sectioned in a two-step process. Reaction with a solution of iodine in alcohol formed a thin, even layer of AgI, which was then dissolved in a KCN solution. The reaction rate of the iodine solution varied slightly over a period of time, so that the thickness of the stripped layers, while quite even and regular for a given specimen, ranged from 65 to l00W for different specimens. This variation was checked by using a thickly plated standard with each run. Layer thickness was determined from undiffused samples by the point where the layer activity drops to half the maximum. This maximum intensity also provides, with appropriate corrections, the initial concentration per layer co. Because of the small penetration distances, it is necessary to use the exact solution of Fick's law for a source of finite thickness.' For a plating of thick- where c is the concentration at depth x. flj the error function, D the apparent diffusion coefficient, and t the time. The diffusion coefficient was obtained from the concentration-penetration data by extrapolating to x = 0 where c/co = erf h/2(Dt)1/2 Enough points were taken to impart confidence in the accuracy of the intersection, generally about ten layers. Four temperatures were used as in Table I. For best accuracy, t and h were chosen to give values of the parameter (Dt)1/2/h between 1.0 and 1.7. A typical concentration-penetration curve is shown in Fig. 1. The diffusion coefficients calculated from Eq. [I] are plotted in Fig. 2. For comparison, the high-temperature data of Tomizuka and sonder 2 which go down to 630°C are plotted as the solid line 2(a) from their expression D = 0.40 exp (-44,090/RT). Also for comparison, the lowest temperature point of Hoffman and Tumbull3 is plotted. It is apparent that our data diverge appreciably from the high-temperature extrapolation by 373°C. A better straight line fit for the low-temperature portion is obtained by subtracting the extrapolated volume diffusion coefficient from the apparent. or measured coefficient, and plotting the difference, curve (h) of

Jan 1, 1970

By Thomas A. Read

The internal friction of single crystals of metals is affected markedly by a variety of factors, which, according to the literature, are without influence on the internal friction of polycrystalline metals at strain amplitudes less than 10-5. For example, the internal friction of a suitably oriented zinc single crystal is multiplied by a factor of ioo when the vibration amplitude is slightly increased, and the internal friction of a copper crystal is markedly increased by the application of a stress of 30 lb. per sq. in. for one minute. In this paper it will be shown that these, together with the other phenomena associated with the damping of mechanical vibrations in metal single crystals, can be satisfactorily explained, at least qualitatively, in terms of an atomic mechanism that has been proposed for quite another purpose—that of accounting for slip in metals. The extraordinary agreement between the observed behavior of the metal single crystals and the behavior that could be predicted on the basis of this atomic mechanism leads to the belief that the latter is probably essentially correct. If this is so, it follows that valuable information about the slip process in metals may be gained from measurements of internal friction on single crystals. In this paper the results of the only study to date on the damping of mechanical vibrations in single crystals of metals mill be presented. Experimental Procedure The internal friction of a material is a measure of the rate at which the energy of mechanical vibrations is converted into heat. The measure of internal friction used in the present paper is the decrcment A, which is defined as the fraction of the energy of vibration lost per half cycle. The measurements described here were made for longitudinal oscillations at a frequency of 33.5 kc. for the copper crystals, and at a frequency of 39 kc. for the zinc crystals. The method used is that of the composite piezoelectric oscillator. The single-crystal specimens are in the form of circular cylinders M in. in diameter and I 1/2 to 21/2 in. long. The crystal rods are waxed in a V-block and sawed to the proper length with a fine jeweler's saw. The ends of the specimen are ground flat, and one end is cemented with a very thin film of beeswax and rosin to the end of an x-cut quartz rod which is 1/4 in. in diameter and 3 in. long. The length of the specimen rod is determined by the condition that its natural frequency for longitudinal vibration be the same as that of the quartz rod, within 0.5 per cent. The lengths of the specimens are thus different for different orientations of the cylinder axis with respect to the crystallographic axes. When the specimen and quartz rods are thus matched in frequency the adhesive is at a node of stress, and it has been shown experimentally that under these circumstances

Jan 1, 1941

By Thomas A. Read

The internal friction of single crystals of metals is affected markedly by a variety of factors, which, according to the literature, are without influence on the internal friction of polycrystalline metals at strain amplitudes less than 10-5. For example, the internal friction of a suitably oriented zinc single crystal is multiplied by a factor of ioo when the vibration amplitude is slightly increased, and the internal friction of a copper crystal is markedly increased by the application of a stress of 30 lb. per sq. in. for one minute. In this paper it will be shown that these, together with the other phenomena associated with the damping of mechanical vibrations in metal single crystals, can be satisfactorily explained, at least qualitatively, in terms of an atomic mechanism that has been proposed for quite another purpose—that of accounting for slip in metals. The extraordinary agreement between the observed behavior of the metal single crystals and the behavior that could be predicted on the basis of this atomic mechanism leads to the belief that the latter is probably essentially correct. If this is so, it follows that valuable information about the slip process in metals may be gained from measurements of internal friction on single crystals. In this paper the results of the only study to date on the damping of mechanical vibrations in single crystals of metals mill be presented. Experimental Procedure The internal friction of a material is a measure of the rate at which the energy of mechanical vibrations is converted into heat. The measure of internal friction used in the present paper is the decrcment A, which is defined as the fraction of the energy of vibration lost per half cycle. The measurements described here were made for longitudinal oscillations at a frequency of 33.5 kc. for the copper crystals, and at a frequency of 39 kc. for the zinc crystals. The method used is that of the composite piezoelectric oscillator. The single-crystal specimens are in the form of circular cylinders M in. in diameter and I 1/2 to 21/2 in. long. The crystal rods are waxed in a V-block and sawed to the proper length with a fine jeweler's saw. The ends of the specimen are ground flat, and one end is cemented with a very thin film of beeswax and rosin to the end of an x-cut quartz rod which is 1/4 in. in diameter and 3 in. long. The length of the specimen rod is determined by the condition that its natural frequency for longitudinal vibration be the same as that of the quartz rod, within 0.5 per cent. The lengths of the specimens are thus different for different orientations of the cylinder axis with respect to the crystallographic axes. When the specimen and quartz rods are thus matched in frequency the adhesive is at a node of stress, and it has been shown experimentally that under these circumstances

Jan 1, 1941

By J. C. F. Randolph

New Granada, or, as it is known to its people, the Republic of Colombia, occupies the northwest corner of South America, and includes the Isthmus of Panama. Although it is one of our nearest neighbors, so little is known about it in the United States that the following notes regarding it, flowing from a year's professional residence, may be timely. It is bounded on the north by the Caribbean Sea and Costa Rica, on the east by Venezuela and Brazil, on the south by Brazil and Ecuador, and on the west by the Pacific Ocean. Its extreme geographical limits are from 2' South latitude to 12' North latitude, and from 69 to 78' East longitude. In size, therefore, it is roughly 1000 miles from north to south, and 600 miles from east to west. After many political convulsions and revolutions, and a somewhat checkered history, the country consists to-day of nine departments, Panama, Bolivar, Magdalena, Cauca, Santander, Antioquia, Tolima, Boyaca and Cundinamarca. These departments are governed from the national capital of Bogota, although each has its own capital and departmental staff. The total population of the Republic is not more than 3,000,000 inhabitants, and these to a large extent consist of mixed races. Those who live in the hot belt are, as a

Jan 1, 1890

By J. E. Gould, H. J. Hand

Many independent studies are being made on slag-metal relationships in the open-hearth furnace, and these studies cannot help but result in an ultimate improvement in the quality of open-hearth steel of both the open and killed types. In maintaining quality control at the National Tube Company's plant, emphasis has been placed on an evaluation of the iron oxide content of the steel in as quantitative a manner as possible, in order that the most desirable level of oxidation might be obtained for a given type of steel, and to secure a more precise basis for final de-oxidation. In the past, various methods were used for estimating FeO content of the metal at tap to ensure uniform and thorough deoxidation of killed steel, avoiding overdeoxidation to minimize the amount of inclusions present and to make as sound a steel as possible. For the open-type steels, such control involves obtaining the necessary level of oxidation for the most suitable action of the steel in the molds to provide good surface quality and cross section for the specific grade involved. While rapid analytical methods are available for determination of FeO in the liquid metal, such methods are still not sufficiently rapid for routine control on the open-hearth floor, nor do such analyses provide information as to what causes high or low FeO values. The method of sampling can still be considered a problem in view of the variability encountered in taking simultaneous duplicate tests. With the accurate rapid methods now available for determining carbon in the metal, estimating slag basicity and obtaining temperatures of liquid metal, it was believed possible to determine the influence of the various furnace reactions in establishiug the state of oxidation at a given time. Simultaneous slag and metal tests were used in this analysis, aided by statistical methods, to determine the factors that affect the metal FeO, and also to make a quantitative evaluation of these factors. Data obtained are from actual iurnace operations, the metal test being of the I spoon, Herty type, and taken in duplicate. Metal temperatures were taken with the open-tube bath pyrometer developed by the Research Laboratory of the United States I Steel Corporation. This method of taking open-hearth metal temperature was invented by Collins and Oseland,l and was developed into its present form by L. 0. Sordahl,2 of the Research Laboratory. The instrument and its mode of operation have been fully described by Sordahl and Sosman in three publications.3,4,5 lag components were obtained by chemical analysis. Data were taken from four 165-net-ton furnaces during the working period of the heat. Recognizing that additions of ore affect the metal FeO. no tests were included within 30 min. after ore additions. In all, 65 tests (48 heats) were used in this study.

Jan 1, 1942

By J. E. Gould, H. J. Hand

Many independent studies are being made on slag-metal relationships in the open-hearth furnace, and these studies cannot help but result in an ultimate improvement in the quality of open-hearth steel of both the open and killed types. In maintaining quality control at the National Tube Company's plant, emphasis has been placed on an evaluation of the iron oxide content of the steel in as quantitative a manner as possible, in order that the most desirable level of oxidation might be obtained for a given type of steel, and to secure a more precise basis for final de-oxidation. In the past, various methods were used for estimating FeO content of the metal at tap to ensure uniform and thorough deoxidation of killed steel, avoiding overdeoxidation to minimize the amount of inclusions present and to make as sound a steel as possible. For the open-type steels, such control involves obtaining the necessary level of oxidation for the most suitable action of the steel in the molds to provide good surface quality and cross section for the specific grade involved. While rapid analytical methods are available for determination of FeO in the liquid metal, such methods are still not sufficiently rapid for routine control on the open-hearth floor, nor do such analyses provide information as to what causes high or low FeO values. The method of sampling can still be considered a problem in view of the variability encountered in taking simultaneous duplicate tests. With the accurate rapid methods now available for determining carbon in the metal, estimating slag basicity and obtaining temperatures of liquid metal, it was believed possible to determine the influence of the various furnace reactions in establishiug the state of oxidation at a given time. Simultaneous slag and metal tests were used in this analysis, aided by statistical methods, to determine the factors that affect the metal FeO, and also to make a quantitative evaluation of these factors. Data obtained are from actual iurnace operations, the metal test being of the I spoon, Herty type, and taken in duplicate. Metal temperatures were taken with the open-tube bath pyrometer developed by the Research Laboratory of the United States I Steel Corporation. This method of taking open-hearth metal temperature was invented by Collins and Oseland,l and was developed into its present form by L. 0. Sordahl,2 of the Research Laboratory. The instrument and its mode of operation have been fully described by Sordahl and Sosman in three publications.3,4,5 lag components were obtained by chemical analysis. Data were taken from four 165-net-ton furnaces during the working period of the heat. Recognizing that additions of ore affect the metal FeO. no tests were included within 30 min. after ore additions. In all, 65 tests (48 heats) were used in this study.

Jan 1, 1942

By William G. Gates

INTRODUCTION The Heath Steele mine is located in the Bathurst-Newcastle area of northern New Brunswick. It is jointly owned by American Metal Climax, Inc. and the International Nickel Company of Canada who hold a 75% and 25% interest, respectively. The ore deposits of lead, zinc and copper sulphide occur in very fine grained pyrite and/or pyrrhotite masses. A consistent spatial relationship with a quartz feldspar porphyry is characteristic of these deposits and the many other similar sulphide deposits in the district. The two principal mineral assemblages of pyrite-sphalerite-galena, and pyrrhotite-chalcopyrite-pyrite, occupy characteristic positions relative to the enclosing rocks. This feature and the nature of the sulphide mineralization are described and the variations in metal content are noted .with special emphasis on the lead-zinc ore zones. The mine product ion rate is 3,000 tons per day of a mixed lead- zinc and copper ore which is extracted from the B-1 zone. The complex nature of the ores presents many metallurgical problems. Optimum metal recoveries are achieved when milll feed grades are relatively consistent and proportions of the contained metals are with in acceptable limits. Ore outlines and stoping blocks are delimited by close spaced diamond drilling. From this information it is possible to forecast the grade of any portion of a stoping block. Production from the various stopes may then be scheduled so as to achieve an acceptable mill feed grade.

Jan 1, 1970

By B. F. Tillson

Mining may be defined as a general term for the working of valuable deposits of minerals, either organic or inorganic in origin, for their removal from the crust of the earth. Besides subsurface excavations, mining generically includes opencuts, clay pits and stone quarries, oil wells, sulphur wells, salt wells, placers, coal stripping, and the leaching of ore bodies. The origin of the word "mine" or "mining" is a matter of conjecture. A Celtic origin has been suggested since the Irish word mein, or the mwyn, meant ore, but it seems to have come from an olf French verb mineor, which meant to excavate, to make an underground passage as in the military appraoch to a fortification, sometimes called ?sapping.?

Jan 1, 1949

By H. E. Stauss, G. Sandoz

THE purpose of this note is to draw attention to the possibility that a melt may be contaminated by a material not in direct contact with it by means of gaseous intermediate agents. In recent years silicon has assumed a position of importance because of its use in rectifiers and transistors and close attention has been required to control of both purification and contamination during all stages of preparation.' This note reports the observation that a graphite heater may have contaminated silicon ingots without direct physical contact through reactions that developed gaseous products. Several ingots made with the equipment of Hino and Stauss,2 using a graphite heater in a dried helium atmosphere, were found to have a small amount of a very hard substance on the free surface. X-ray analysis by F. W. von Batchelder showed the sub- stance to be Sic. Similar contamination was not found when the heater was tantalum, indicating that the carbon had not come from an original impurity in the silicon powder. One source of the carbon could have been volatile matter released from the graphite heater. This heater had been used about ten times at the time of the observations. A second source of carbon could have been a direct reaction between the quartz crucible and the graphite heater to form CO, or an indirect reaction involving a crucible-melt interaction and volatile SiO as an intermediate product. Such reactions should have developed Sic on the heater; and in fact a yellow powder did form on the inside of the graphite heater although its composition could not be determined. References 'H. C. Torrey and C. A. Whitmer: Crystal Rectifiers (1948) Chapter 10. New York. McGraw-Hill Book Co. 2 J. Hino and H. E. Stauss: Trans. AIME (1952) 194, p. 656; Journal of Metals (June 1952).

Jan 1, 1954

By Charles G. Yale

A few years ago somebody connected with one of those self-constituted bodies of unofficial character, like a Chamber of Commerce, Board of Trade, or State Development Board, started a catch-phrase referring to California as a The Land of Sunshine, Fruit, and Flowers," and the railroad magazines and folders keep it steadily in use, working day and night. Yet it altogether ignores the substance which brought the State into the Union, which peopled it, and which made it famous thronghout the world. You ladies and gentlemen who have come from what wc here call "the East," have in your own States, no matter which one, sunshine, fruit, and flowers. But your Eastern States, having these things as we do, have not the gold that we do. Therefore, the old designation of " The Golden State," applied to California, should be revived, as being the most distinctive term. It is worthy of remembrance, too, that during the dark days of the civil war this State handed over $172,000,000 in yellow gold, and saved the credit of the nation. Gold-mining has been carried on in California since '' The days of old, The days of gold, The days of '49," and it still continues. Since that historic year, and up to the end of 1910, the State has produced, in gold alone, $1,530,214,468. Since 1792 the entire United States production of gold has been $3,261,573,500, so that the single State of California has, in that period, produced within $201,144,564 of one-half of all the gold from Alaska, Arizona, Colorado, Idaho, Montana, Nevada, New Mexico, Oregon, South Dakota, Utah, Washington, and the Southern and scattering States. In other words, all the other 25 States of the United States combined

Jan 1, 1912

By Walter Miller

The remarkable strides which have been made in recent years in the art of petroleum refining are not fully apparent until we attempt to compare the scientific status of the industry today with the basic conditions existing a decade or so ago. The spotlight has played so strongly on the development of cracking that many of the wonderful steps brought about in other departments have crept upon us unawares. A number of causes have contributed to this highly accelerated rate of progress. Constant effort by both companies and individuals to obtain the honors and prizes rewarding new discoveries has played its usual important part in our industry as in others. Competition has applied its continuous pressure on the refiner to reduce costs and losses and increase the proportionate yields of the higher-valued fractions. Advances in the engineering professions and growth in chemistry and allied sciences have contributed much. But there are other factors which deserve particular mention. The rapid development of the internal combustion engine, with the rigorous quality requirements and large quantity consumption of both fuel and lubricants has been a tremendous influence in adding impetus to natural progress. The teaching of petroleum principles and practices in many of our best universities and technical schools, and the calling into the industry of ever greater numbers of scientifically trained men to supplement the efforts of the practically trained operators, as well as to apply at close hand the fundamentals of science as a life work, has had and is having an incalculable influence. Important Improvements Let us consider briefly some of the most important improvements: First, distillation, which constitutes the greatest single phase of refinery operations, even with cracking excluded; that phase of distillation being handled as an individual subject in this symposium. Today we are distilling crude oil and redistilling by-products at a rate very much faster than was possible with the lesser knowledge of the art which we possessed

Jan 1, 1927

By F. M. Lewis, E. C. Johnson

Used as a classifier in a plant expanding capacity or changing to closed-circuit operation, the liquid-solid cyclone offers the advantage of being adaptable to existing conditions. This paper presents the costs involved and experience gained from operating a unit of this kind. BY now application of the liquid-solid cyclone to various classification problems in the chemical and metallurgical fields is more or less familiar. A less publicized application receiving wider consideration as time goes on is its use as a classifier in closed-circuit grinding operations. This paper presents the costs involved and the experience gained from operating a unit of this kind. In May 1951 the Tennessee Copper Co. installed in its London mill at Copperhill, Tenn., a liquid-solid cyclone in closed circuit with a 6x12-ft ball mill. The circuit in which this cyclone is used is the regrind or secondary grinding circuit of a copper flotation plant. Originally it consisted of a 7x1-ft conical ball mill in closed circuit with a bowl classifier. Changes made in the primary grinding circuit of the mill necessitated a regrind circuit of greater capacity. The bulk concentrate to be ground was raised from 900 or 1000 tpd to 1200 or 1300 tpd, and to accommodate this increase a 6x12-ft ball mill which had been in the primary grinding circuit was moved into the regrind circuit. When this was done it was found that the classifier was too small to give efficient operation. Space in the plant was at a premium, and since use of the cyclone offered considerable economy the installation shown in Figs. 1-3 was made. The unit installed is a 24-in. diam cyclone classifier with a 20" cone angle. Diameter of the vortex finder is 8 in., the feed entrance area 20 sq. in. Maximum diameter of the adjustable apex valve is 6 in. and minimum diameter approximately 3.5 in. To refer again to Figs. 1 and 2, the cyclone* is mounted motor. It is charged with 18 tons of 1-in. balls. The overflow, or fines, passes by gravity directly to the copper flotation plant. The ball mill discharge and the new feed combine in a sump from which they are sent to the cone by an 8x6 SRL pump at a rate of 497 gpm. Pressure at the cyclone is 5 psi. For reasons dictated by the nature of the ore treated, particularly the bonding of fine grains of chalcopyrite to pyrrhotite, the froth from the second cell of the copper rougher circuit is returned to the regrind mill. This flow, which somewhat complicates the standard closed-circuit calculation, is seen in Fig. 1 to be 156 tpd of solids. This combines with the cyclone classifier underflow to constitute the ball mill feed. The requirement of the regrind product is that it be 77 to 80 pct —200 mesh. The liquid-solids cyclone operating in conjunction with the 6x12-ft mill adequately met this requirement. Of primary importance is the fact that this arrangement provided sufficient classification capacity to replace the undersized classifier and was capable of building up a circulating load to 87 pct, large enough to give an efficient grind. In this instance the circulating load is taken as the ratio of sands to new feed. Any comparison of performance between this liquid-solid cyclone and the replaced classifier would of course be unfair, since the bowl classifier was

Jan 1, 1955

By R. A. Vandermeer

It is usually assumed that the rate-determining step in the migration of a grain boundary involves the thermally activated transfer of single atoms across the interface. Chemical reaction rate theory then gives a migration rate which is proportional to the driving force when this is small compared to kT.1 In their recrystallization studies on aluminum, Gordon and vandermeer2 obtained data which was capable of providing the first experimental test of this proportionality. They correlated stored energy (driving force) release measurements determined calorimetrically with fraction recrystal-lized kinetic (growth rate) data acquired metallo-graphically at a temperature where a significant amount of recovery takes place concurrently with recrystallization. Within experimental error, the results of Gordon and Vandermeer confirmed experimentally, at least over a limited range, the linear dependence of boundary migration (growth) rate on driving force in accordance with theory. In obtaining these results, however, an incorrect, implicit assumption was made in relating the average instantaneous growth rate of the recrystallized grains to the measured fraction recrystallized kinetic data. The purpose of this present note is to point out and correct this assumption. An alternate approach, whereby a more proper average growth rate can be calculated from the recrystallization kinetic data, is presented. The earlier data, reevaluated in terms of this new approach, show the same general trend as before so that the original conclusion of Gordon and vandermeer2 is still valid. As was shown in a detailed study3 of the geometrical features of recrystallization in aluminum, the colonies of recrystallized grains can be regarded as uniform cylinders embedded in a three-dimensional matrix, the number of such colonies being constant. Thus during the early stages of recrystallization the volume fraction recrystallized, Xv, can be written as Xv=ynvlr2 [l] where y is a shape factor and i and r are defined as the average length and radius of a recrystallized colony and are spatial averages over the specimen. -nv, is the number of such colonies in a unit of volume. The erroneous assumption made in the earlier paper2 was that r in Eq. [I] could be replaced by

Jan 1, 1965

INTRODUCTION Porphyry copper deposits have been reported from the Caribbean area by Pease (1966), Cox, et al. (1973), Guild (1974), Kesler, et al. (1975), and others. This chapter summarizes the most widely known characteristics of those deposits. Only one deposit that conceivably can be classed as a porphyry copper occurrence is in production (Pueblo Viejo, Dominican Republic), but others are known whose tonnage and grade are of economic interest. Deposits in this province may be classified as copper-gold or copper-molybdenum types (Kesler, 1972), but deposits associated with quartz-rich plutons that have high Na2O:K2O and high gold:copper but low molybdenum: copper ratios dominate. Porphyry copper occurrences are reported in the literature from Puerto Rico, Haiti, the Dominican Republic, Jamaica, and Cuba. Only the porphyry copper deposits from Puerto Rico are extensively described in the literature; consequently the Caribbean porphyry copper province in general is not as well documented as the southern Cordilleran orogen. Because past published technical descriptions are incomplete, some data presented here are new to the literature. The Caribbean includes the island arcs between North and South America. Porphyry copper occurrences are known from the Greater Antilles, the generally east-west trending group of islands that lies south of North America. Fig. 48, therefore, only covers the Greater Antilles portion of the Caribbean. Porphyry copper deposits in this area are not described by the Lowell and Guilbert (1970) model in details of metallization (general paucity of molybdenum), alteration (scarcity of orthoclase), or petrography (preponderance of quartz diorite). Therefore, this model should be modified to include deposits associated with quartz-bearing plutons such as those found in the Caribbean. In the Meme deposit on Haiti ore occurs in skarn adjacent to the quartz diorite phase of a composite quartz monzonite-granodio-rite-quartz diorite pluton (Kesler, 1968). This deposit, with a K-Ar 66 m.y. date, is not included in Fig. 48 as a porphyry copper deposit because metallization is restricted largely to the intruded rocks. Although the intrusive rocks at the Meme deposit may contain sulfide near skarn contacts they are otherwise essentially unaltered. Porphyry molybdenum deposits as defined by Clarke (1972) have not been reported in the Caribbean area.

Jan 1, 1978

By C. W. Stratford

[During the last few years, the necessity for development work has been generally recognized by executives throughout the oil industry, resulting in greatly accelerated progress and the adoption of many noteworthy improvements in refining methods and equipment. Several years ago, the Associated Oil Co. decided to improve distillation methods with the object of reducing refining costs. This extremely interesting work was entrusted to the writer, and W. S. James, now Chief of Research for Studebaker Corpn. of America, was selected as the principal collaborator. The latter contributed much during his two years with the Associated Oil Co., to the development work that has followed. The writer extends to the Associated Oil Co. his appreciation for permission to disclose the details of distilling equipment. In petroleum refining the principal requisites of good economics are the separation of high-priced distillates from those of lower price; maxi-mum yield of any desired distillate; lowest capital investment in refining equipment; lowest cost of operation and maintenance, and the best adaptability and flexibility of the same refinery equipment for handling crudes of widely varying characteristics. The first two items mentioned, separation and yields of distillates are determined by efficiency of fractionating equipment,. Discussion in this paper is chiefly concerned with oil-heating equipment, combustion and furl economy. It has long been well known that velocity plays a very important part in all heat transfer systems. Any betterment in specific transfer. rates in such systems must. always involve velocity. Realizing this fact, IV decided to adopt as a basic principle, the employment of energy to impart velocity required for high transfer rates through a heating diaphragm, and our method of modernizing obsolete shell stills is founded on this principle. Mechanical energy is usually cheap and its rational rspcntliture is returned in the form of greatly increased heat transfer rates, on both oil and gas sides of the sheet. Certainly there is nothing new in this principle, the only novelty being that of our peculiar method of application On the oil side (Fig. I) use is made of a centrifugal pump to jet the oil against the heated sheet thereby creating a high velocity sheet flow over the entire fired area. Such a pump is one of the most efficient machines, so far developed, for moving fluids. 'I'he oil, under pressure impinging

Jan 1, 1928

By Francis Crockard

DURING the past five years we have probably witnessed greater technological advances than in any similar period. Industry and science have steadily marched ahead. The makers of iron and steel products have watched with great interest the development of stream-lined trains, faster and safer airplanes, the entirely new science of air-conditioning and the widespread use of stainless steels. Since 1930, we have witnessed the erection of the world's largest suspension bridge, the largest and fastest ocean liner and the spectacular Boulder Dam, while even greater things are planned in these particular fields. Other indus-tries, too, have been moving ahead rapidly. This advance in a few years has been caused primarily by the fierce competition of the depression. Now, more than ever, is the emphasis placed upon quality and service. Makers of southern merchant pig iron have been no exception and have been confronted with increasingly strict chemical specifications and with much greater stress on physical characteristics than ever before. For example, sulfur in the iron must be held very low, competition demanding that it be in the 0.020's and low 0.030's; silicon content must be held within a very narrow range, and definite requirements of phos-phorus and manganese are an essential part of the specifications. Physical characteristics are becoming of increasingly greater impor-tance. The introduction of triple-skimmed, slow-cooled iron several years ago was the first step in this direction. Now there are a few customers who buy iron by chemical analysis and physical appear-ance, having found that the analysis alone is an insufficient guide to their requirements.

Jan 1, 1935

By P. W. George

THE rapid increase in cost of discovering new orebodies by churn drilling in the Tri-State district has led to some attempts to lessen the expense by using geophysical methods. Electrical prospecting was tried three or four years ago, but no successful results were recorded. In 1926, the Federal Mining and Smelting Co. engaged the North American Exploration Co., of Houston, Texas, to make some tests with the torsion balance. At first, it was thought that the most favorable conditions for discovery of ore deposits with the torsion balance would be in locations where the ore was known to occur at rather shallow depths, FIG. 1.-CROSS-SECTION OF DUENWEG LEASE. therefore the first trial was made at Duenweg, east of Joplin, where some zinc ore had been developed at a depth of 130 ft. The gravity gradients at 61 stations on a tract of about seventeen acres indicated plainly one large zone of maximum gravity and a smaller narrow zone of minimum gravity. Fourteen churn-drill holes, half of which struck ore, show that all the ore found was located outside the zones of maximum and minimum gravity. In the zone of maximum gravity the limestone beds were closest to the surface, and the first chert beds encountered were at the greatest depth. The results (shown in Table 1) indicated that the gravity of the, limestone was greater than the gravity of the fractured chert together with its orebodies, and probably also greater than the bouldery soil and clay on top of the limestone. A cross-section of the Duenweg lease is shown in Fig. 1.

Jan 1, 1928

By W. Kauenhowen

The production of petroleum in Germany during 1932 totaled about 1,608,558 bbl., a slight increase over the 1, 602,517 bbl. produced in 1931. A decline, as shown in Table 1, occurred chiefly in the Volkenroda (Thuringia) field. The total production of the other fields (salt domes), however. reached a new record, about 21 per cent above 1931. Table 1.—Oil Production of Germany by Fields and Oil Provinces, 1928-1932 (Barrels of 42 Gallons)" Salt Dome Province __________________________________________________|_________________________________________________________________________________________________________________________ 1928 274,323 322,742 679 46,319 644,021 644,315 1929 310,891 337,582 10,535 67,578 719,901 720,069 1930 586,404 427,539 100,716 72,485 1,186,969 29,806 1,220,296 1931 506,548 403,634 213,549 116,088 1,242,598 360,885 1,602,517 1932 769,405 366,982 230 979 130,711 1,498,077 110,481 1,608,558 " Official figures published in Germany are given in metric tons. For the above conversion into barrels a factor of 1 metric ton equaling 7 barrels has been used. Includes a very small production from Hcide, Holstein. c Includes a very small production from Tegernsee, Bavaria, and Bruchsal, Baden. Nienhagen-Hanigsen Field In 1932 the Nienhagen-Hanigsen yielded about 51 per cent of the production from the four German salt dome fields. During 1932 the productive area was again extended, chiefly towards the northwest in the so-called north district, to which the present drilling activity is confined almost entirely. Since the discovery of the north district in 1928, about 45 wells have been drilled in it, of which only two were

Jan 1, 1933

By R. E. Boehler, N. C. Ludwig

At Buffington Station, Gary, Ind., Universal Atlas Cement operates fourteen 8 x 101/2 x 155-ft cement kilns in mill 6 and two 11 x 360-ft kilns in the Harbor plant. The No. 11 and 12 kilns in mill 6 are equipped with Manitowac recuperator sections. This report describes studies in measuring exterior shell temperatures on several of these kilns and the development of a traveling radiation pyrometer with certain novel features. Preliminary Work: At first various temperature-sensing devices were placed on the steel shell: 1) crayons with calibrated melting points, 2) colored paints with temperature-calibrated pigments, 3) aluminum paints with temperature-calibrated binders, and 4) metal-stem dial thermometers. The colored paints and aluminum paints failed to indicate the temperatures correctly. The crayons and thermometers did indicate fairly correct temperatures, but it proved impossible to apply enough of these on the shell to detect all the potential areas where hot spots might develop. Furthermore, considerable labor was required to apply these sensors and read the temperatures. Consequently no further work was done with these devices. Formation of Hot Spots: In the burning or clinker-ing zone of a cement kiln, the thickness of the protective coating and thickness of the brick govern the amount of heat transmitted to the steel kiln shell. Usually the protective coating consists of 4 to 8 in. of fused cement clinker. The formation of a hot spot is usually caused by loss of coating? that is, localized areas of the coating become thin or fall away from the refractory. This is generally caused by excessive temperature in the burning zone over a fairly long period of time. It may also be caused by a sudden thermal change in the burning zone. Variations in raw feed composition and in feed rate require changes in the fuel and air rates, and when these are not appropriately altered, conditions may develop in the kiln that will result in loss of coating. Luminescence on the kiln shell indicates that a hot spot has developed to a point that usually alters the refractory's thermal conductivity properties. When this thermal weakness zone occurs in the burning zone of the kiln, constant vigilance is required to protect it by maintaining proper coating. Even so, it has been the writers' experience that within a period of several days to about four weeks the hot spot usually recurs with greater severity. This necessitates shutting down the kiln and re-bricking the affected area. One of the prerequisites of a good burnerman is the ability to maintain a protective coating despite the many variables in operation. When he knows that it is getting thin or that an area has dropped off, he reduces the firing rate and kiln speed and brings feed into the affected area in an effort to rebuild the coating. But when powdered fuel is burned, the atmosphere of the kiln may prevent the burnerman's observing the condition of the coating closely at all times without taking off the fire. It is not considered good practice to do this frequently, as it imposes a thermal shock on the coating and upsets operation of the kiln. To help the burnerman scan the shell of the kiln along the burning zone, therefore, a radiation pyrometer, connected to a potentiometric recorder, was mounted on a slowly moving steel cable. The theory of operation, construction details, and adaptability of the radiation pyrometer are included in an excellent monograph' and also in a textbook.' Shell temperatures of the Atlas Cement kilns were measured with a Brown Instruments Div. low intermediate range Radiamatic unit, of range 200" to 1200°F, and a circular chart Electronik potentio-metric recorder, of range 500" to 1000°F. In Bulletin 59095M the supplier publishes standard calibration data (millivolts vs degrees Fahrenheit) for this radiation pyrometer, These data, however, apply only to flat surfaces having emissivities of unity. Calibration of Radiation Pyrometer for Use on Curved Surfaces: When applied to surface temperature measurements, the radiation pyrometer reading depends on the nature of the surface, the material of which it is composed, and also to some extent on the temperature of the surroundings. Although the present radiation pyrometer is designed to give a calibrated response under ideal (black body) conditions when used commercially, it must be calibrated empirically. The calibration procedure, given below, follows that described by Dike (Ref. 1, pp. 38-39). Calibration tests on plane and curved surfaces showed that the response of the radiation pyrometer was very

Jan 1, 1961