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By Dick Whittington, W. R. Taylor

GENERAL In mid-1974, a representative of ARCO Petroleum Company walked into our Austin offices and asked for a permit for ARCO's first Clay West Mine site. This was the first in situ uranium mining permit issued in the United States. That initial permit, issued in January 1975, was for three acres. The four years since have been characterized by growth and change. Today there are 16 permits approved for approximately 1,540 production acres issued to five companies at eight sites in four counties. There are approximately seven additional permit applications being processed or on the verge of being submitted for an estimated 2,000 additional acres of production. As a rough gauge of the financial scope of this activity, at the typical 40 production wells per acre and an estimated $2,000/well, operators hale installed or committed $122 million for production wells. This does not account for the exploration and development wells installed to delineate the ore or the cost of processing facilities for extracting the uranium. HISTORY OF URANIUM MINING IN TEXAS Information I have concerning early in situ uranium mining activities is "sketchy" but the apparent first on-site test of in situ uranium mining was conducted between 1967 and 1971 at the Dueterstat site, north of Yorktown in Gonzales County, by City Service. Others ran tests at the Bruni site in Webb County and the Burns and Clay West sites in Live Oak County in the mid-70's. During this period, Texas Water Quality Board personnel in the central and district offices maintained a general surveillance of these various test activities. Regulation of in situ uranium mining was formalized with the issuance of a permit in January 1975 with the advent of ARCO's initial production scale (3 acre) effort in the Clay West area at the Moser mine site. Since 1975, the accelerating rate of mining and exploration activity is noticeable. There were 16 exploratory rigs operating early in 1977. This year, the rig count is averaging 46--a 287% increase. HISTORY OF LEGISLATION Paralleling this mining activity was state and federal legislation which subjected in situ mining to environmental regulation. The following is a brief chronology of the legislation that is directly or indirectly related to uranium mining. As most of you know, disposal wells are an integral part of most in situ uranium mines operating in Texas. They are used both during production and during aquifer restoration following production. The wells are regulated by the Texas Injection Well Act, enacted in 1961 by the Texas Legislature. In 1967, the Water Quality Act established the Texas Water Quality Board, and provided for the regulation of water quality by the so-called permit system. In 1969, the Solid Waste Act was enacted by the Texas Legislature. The legislation provides for control of wastes from manufacturing, mining, and agriculture. This Act regulated uranium surface mining activities until 1975 when the Texas Surface and Mining Reclamation Act placed responsibility with the Railroad Commission for uranium open-pit mining and surface mining of coal and lignite. In 1972, the Federal Water Pollution Control Act (Public Law 92-500) was passed. This legislation forms the legal base for the NPDES (National Pollutant Discharge Elimination System) and the subsequent point source effluent guidelines and standards. The November 6, 1975 issue of the Federal Register published interim final rules for Best Practical Treatment levels for effluent discharges from ore mining and dressing operations. Litigation was immediately initiated by eleven companies against these proposed rules, and they are currently being reconsidered for reissuance in 1979. In 1974, the Federal Safe Drinking Water Act (Public Law 93-523) was enacted. A part of this legislation is the Underground Injection Congrol Program. The regulations implementing this program have undergone various public hearings and it is expected that they will be published in the Federal Register before the end of 1978. In 1975, the Texas Surface Mining and Reclamation Act (Senate Bill 55), providing for the Railroad Commission's authority to require reclamation of surface mines, was passed. In 1977, an amendment to Senate Bill 55 was introduced that proposed to place regulation of in situ mining of coal, lignite, and

Jan 1, 1979

By K. R. Weller

The Ardlethan Tin Ltd. concentrator typically recovers 55% of the tin in a gravity concentrate at 51% grade from fresh ore assaying 0.5% Sn. Coarse gravity concentration is performed in a complex circuit involving Reichert cones, spirals, shaking tables and two regrind mills. The paper describes how flow and size-by-size sample data from a steady-state survey were used to construct a computer model of the plant involving 46 process streams. The data reduction involved a computer- aided mass balancing technique, recovery-size modelling of gravity concentrators and the use of a mineral dressing flowsheet simulator. The model was used to simulate possible rearrangements of the available equipment. Early simulations indicated that improved performance could be obtained by using spirals to-treat cone middlings or tailings rather than cone concentrates. A test spiral rig was used at Ardlethan to determine typical performances for all cone product streams and the results were incorporated in new simulations. A revised circuit was recommended and implemented by Ardlethan Tin as far as physical restraints within the plant would allow. Production figures show that a substantial increase in tin recovery and 10-15% increase in milling rate were achieved following the circuit changes, and these improvements were sustained over a six month period.

Jan 1, 1984

By W. C. Hittinger, J. McGlassan, J. W. Peterson

THIS paper describes the result of an investigation of the production of thin alloyed layers on a thicker substrate of pure germanium as one step in the manufacture of transistors.' The technique of alloying materials with semiconductors is a means of introducing small amounts of impurity elements in the alloyed regions of the crystal lattice of the semiconductor, the presence of which make possible the junction type transistor.2 Impurity elements are added which will produce regions having differing electrical resistivities and means of carrying current. Impurities are of two types: those which produce an excess of electrons (negative or n-type), and those which produce a deficiency of electrons (positive or p-type) in comparison to the pure semiconductor. The boundary between two such regions is designated a p-n junction. Elements in Group V of the periodic table, having five valence electrons, give rise to an excess of electrons when present substitutionally in the semiconductor lattice (usually germanium or silicon from Group IV). Similarly, elements in Group III create a deficiency of electrons. Germanium and silicon which are substantially free of impurities of either p or n-type are designated intrinsic (i-type) semiconductors. The usual junction ----trarnsistor has

Jan 1, 1958

By Read Winterburn

This discussion covers only one method of pressure drilling—that developed in the Kettleman Hills field. Thus it is probable that many departures from the procedure herein described would be advisable, and perhaps necessary, in using this method of drilling wells in other localities. Purpose of Pressure Drilling By the early part of 1936, formation pressures in the heavily produced north end of the Kettleman North Dome field had declined to range from 1000 to 1500 lb. per sq. in. This low pressure, combined with the depth of the wells (8000 to 9000 ft.) permitted water to be filtered out of the mud into the producing sands during drilling operations. The loss of water was indicated by loss of fluid from the suction tank while drilling, accompanied by an increase in mud weight. It was found that when water was added to the mud stream at such a rate as to keep the fluid level in the suction tank constant, the mud weight would not vary. This indicates that water only was forced into the sands. The rate of this loss at various wells ranged from 2 to 5 bbl. per hour. At some places complete loss of circulation occurred, and drilling mud to the extent of 200 to 1000 bbl. had to be pumped into the sands before returns were regained. It was believed that these conditions had already begun to harmfully affect production, and that such effect would become more pronounced as formation pressures continued to decline. Pressure drilling with oil was introduced because it eliminated the danger of loading the formations with mud and water. The method also afforded a convenient means of testing as drilling progressed, lessening the amount of formation testing, which had become necessary because of encroaching edge water.

Jan 1, 1938

By Ralph W. Bailey, William B. Price

ARSENIC, antimony and phosphorus are now used in the brass industry as standard inhibitors in preventing dezincification in [ ] condenser tubes. This subject has been thoroughly covered by Barry,1 who described the testing procedure by total immersion of suitable specimens in a I per cent cupric chloride solution at definite temperatures. Effects of dezincification were then determined by loss in tensile strength and elongation of the test specimens after definite periods of immersion. In the crystallography of the chemical elements as tabulated by William Hume-Rothery,2 phosphorus (metallic), arsenic, antimony and bismuth are placed in group V-B and the type of crystal lattice for arsenic, antimony and bismuth is given as rhombohedral. The Metals Handbook3 [ ] lists them as "rhombohedral hexagonal," with the additional notation that for arsenic this is the ordinary form at 20°C.; other modifications known or probable at other temperatures. In view of these statements and of the fact that phosphorus, arsenic and antimony are effective in increasing the resistance to dezincification, it was natural to assume that bismuth would act in the same manner. A series of tests was therefore carried out employing the methods described by Barry. Much to our surprise, bismuth did not inhibit dezincification, but rather seemed to accelerate it. Tensile-test speci-

Jan 1, 1942

By James K. Richardson

FIRST indications that mineral industries expansion is beginning to show results are contained in the report by Defense Mobilizer Charles E. Wilson, The Battle for Production. The report, submitted to the President early this year, says that the United States has reached a $2 billion-per-month rate in military deliveries-three times that of 1950. Plant expansion in 1951 totalled $11.1 billion, the report states. Certificates of accelerated amortization have been approved to cover $11.4 billion in proposed plant construction. In reference to plant expansion significant to the mineral industry, the report states: •Steel industry goal is 120 million ingot tons by 1954, compared with present 108 -million ingot ton capacity. •Taconite beneficiation should result in 15 million tons by 1955. •An existing annual aluminum output rate of 860,000 tons. •An estimated 500,000 tons of sulphur by late 1953 •Manganese production up 50,000 tons as- the result of new projects in 1952. •Montana tungsten project coming into production in 1952. •Present zinc production expansion projects to add an estimated 150,000 tons to the 1951 production figure in 1953. Information gathered from official sources, other than Mr. Wilson's report, indicates an increase in the annual capacity of other segments of the industry by 1955, as shown in Table I. [ ]

Jan 1, 1952

By Edward Keller

Someone some time ago remarked that some chemists still insist on telling us how to determine copper by the electrolytic method. The writer must confess that he believes that everything is not known definitely as yet as to how the exact amount of copper is determined in such material as purest commercial electrolytic copper. Some of us are not yet convinced that the pure copper atom is at all times deposited from an acid solution and that no oxygen or hydrogen will, under certain conditions, accompany it. Difficulties with impurer material are frequent, but erroneous results are not always apparent, since these do not speak so readily for themselves as those in the first case. By this is meant that if a chemist finds 100 per cent. of copper in electrolytic copper it is pretty certain that he perceives the result to be wrong, while if he finds 0.1 per cent. of copper too much in a very impure material he is far more likely to be unconscious of his error. These, in a wide experience, are frequent happenings and the writer has always looked with interest to publications on this subject. In turn, he feels justified in giving to others a few of his own observations. Up to a few years ago there were two methods of electrolytic copper assay in technical use, which had in common, that the amount of copper deposited on the cathode did not exceed 2 g., and they differed in that, for the one a large sample1 (20 to 80 g.) was taken from the general sample by a splitting device, dissolved, and from the solution a small portion (to contain 1 or 2 g. of copper) measured out for the electrolytic deposition; in the other method the copper was determined, generally in 1-g. portions of the separated coarse and fine portions of the sample, all of which passed a 16 or 20-mesh screen, being accomplished by a 40-mesh screen,

Jan 1, 1914

By Leslie Burris, J. C. Hesson

The diffusivity of uranium in liquid cadmium has been measured as a function of temperature by the capillary -bath technique. The diffusivity measurements were made at 4509 500°, 575º, and 650°C, over which temperature range the diffusivity of uranium varied from 1.3 to 2.3 x 10-5 sq cm per sec. The diffusivity of uranium in cadmium was less than that predicted by the Einstein-Stokes equation. VERY little information is available on the diffusivity of uranium in liquid metals. Bonillal has reported a single measurement of the diffusivity of uranium in bismuth. Measurement of the diffusivity of uranium in cadmium was undertaken, not only to supply data in an area in which a dearth of information exists, but also because of a need for this physical property measurement in connection with mass transfer studies now underway in the U-Cd system at Argonne National Laboratory. The capillary-bath method used in this work has been successfully used by other workers2"4 to obtain diffusivities in liquid metal systems. Although considerable experimental technique is required to obtain reliable diffusivity measurements, the basic information required is only that of temperature, capillary tube length, the initial and final compositions of the alloy in the capillary tube, and the composition of the bath into which the solute element is diffusing. From these measurements, diffusivities may be calculated using Fick's law. The diffusivity equations are presented in the Appendix. Equations which are often used to predict diffusivities in dilute solutions5 are the Einstein-Stokes equation: D= (kT)/(6pµr) and the Eyring equation: D = (?,kT/?y?zp), where D= diffusivity (sq cm per sec), k = Boltzman's constant, T= temperature ("K), p = viscosity (poises), r = radius of diffusing molecule or species (cm), and A,, Ay, and A, are the diameters of the diffusing molecule in the three axial directions. For round molecules, the Eyring equation gives values which are 37r times larger than the Einstein-Stokes equation. In this work, the experimental values were compared to the Einstein-Stokes equation. Experimental values of diffusivities in liquid metal systems usually lie between those predicted by the Einstein-Stokes and Eyring equations. The viscosity values for cadmium were obtained from the Liquid Metals Handbook.6 EXPERIMENTAL APPARATUS AND PROCEDURE The general procedure employed consisted of rapidly immersing in a molten cadmium bath containing a negligible amount of uranium a capillary

Jan 1, 1963

By Edward Keller

THE ASSAY FOR COPPER. SOMEONE some time ago remarked that some chemists still insist on telling us how to determine copper by the electrolytic method. The. writer must confess that he believes that everything is not known definitely as yet as to how the exact amount of copper is determined in such material as purest commercial electrolytic copper. Some of us are not yet convinced that the pure copper atom is at all times deposited from an acid solution and that no oxygen or hydrogen will, under certain conditions, accompany it. Difficulties with impurer material are frequent, but erroneous results are not always apparent, since these do not speak so readily for themselves as those in the first case. By this is meant that if a chemist finds 100 per cent. of copper in electrolytic copper it is pretty certain that he perceives the result to be wrong, while if he finds 0.1 per cent. of copper too much in a very impure material he is far more likely to be unconscious of his error. These, in a wide experience, are frequent happenings and the writer has always looked with interest to publications on this subject. In turn, he :feels justified in giving to others a few of his own observations. Up to a few years ago there were two methods of electrolytic copper assay in technical use, which had in common, that the amount of copper deposited on the cathode did not exceed 2 g., and they differed in that, for the one a large sample 1 (20 to 80 g.) was taken from the general sample by a splitting device, dissolved, and from the solution a small portion (to contain 1 or 2, g. of copper) measured out for the electrolytic deposition; in the other Method the copper was determined, generally in 1-g. portions of the separated coarse and fine portions of the sample, all of which passed -a 16 or 20-mesh screen, being accomplished by a 40-mesh screen,

Jan 8, 1913

By Bryon W. Cheever

The greatest objection to be brought against the present methods for estimating phosphorus in iron and steel, is the time consumed in the operation. The following method, originated and perfected by Mr. E. D. Campbell, assistant in the chemical laboratory of the University of Michigan, will, 1 think, if carefully followed out, give results that are sufficiently accurate for technical purposes, and will give them in less time than they can be obtained by any other process. The process consists in comparing the color obtained by the action of stannous chloride upon a solution of the phospho-molybdate precipitate obtained from the solution of iron or steel, with that obtained from a standard solution of molybdie acid which represents a given amount of phosphorus. The operation is as follows : Take of ordinary steel 1 grm. and treat as in any of the wellknown processes until the phosphorus is precipitated as ammoniumphospho-molybdate. When precipitated, the phospho-molybdate precipitate is filtered out, thoroughly washed with an acid solution of ammonium nitrate, and, finally, twice with water, to remove most of the ammonium nitrate. The precipitate is then dissolved in about 1 c. c. of 10 per cent. potassium hydrate, which is let fall drop by drop on the filter till the precipitate is dissolved ; the filter is now washed with about 25 or 30 c. c. of water, and the potassium hydrate solution, which now consists of 25-32 c. c. of solution, is boiled until the peculiar frothy appearance, which first appears on boiling, is entirely gone. The solution is then cooled until perfectly cold, and about 10 or 15 c. c. of strong hydrochloric acid added ; if the solution is kept cold this will form no precipitate, but a light yellow or colorless solution. The solution is now ready for the addition of stannous chloride, and the subsequent comparison of color produced with that obtained from the standard molybdie acid. The comparison is made in tubes that are calibrated like carbon-tubes, but which are larger, about 5/8-inch bore, and graduated to 100 c. c.; this makes them about 18 inches long. To make the comparison of color, first transfer the now acid solu

Jan 1, 1886

By Edward J. Ryan, E. A. Peretti

iV preliminary X-ray and metallographic survey of the ternary system Bi-In-Te revealed that the following isopleths could form quasibinary systems: InTe-Bi, InTe-InBi, InTe-BizTe3, and InzTe3-Bi2Te3. The nature of the InTe-Bi phase diagram was established by Bologna and Peretti.' This article presents the results of an investigation of the InTe-InBi system by thermal analysis, X-ray methods, and metallographic examination. The bismuth and tellurium were bought from the American Smelting and Refining Co. The tellurium had the following spectrographic analysis: 0.0001 pct Mg, 0.0001 pct Si, 0.0001 pct Fe, 0.0002 pct Al, and 99.999+ pct Te (by difference). The bismuth assayed: 0.0001 pct Mg, 0.0001 pct Pb, 0.0001 pct Fe, 0.0001 pct Cu, and 99.999+ pct Bi (by difference). The indium was obtained from the Indium Corp. of America and contained 0.002 pct Cu, 0.006 pct Pb, 0.01 pct Sn, 0.01 pct Zn, and 99.97+pct In. The alloys were made by melting the required proPortions of InTe and in evacuated, sealed quartz

Jan 1, 1967

By M. R. Geer, H. F. Yancey

John Grifien (Pittsburgh)—I wish to congratulate the authors on this paper, which, I am sure, will promote a clearer conception of the various criteria which have been advanced as measures of coal-cleaning performance. Their clear descriptions of the more important criteria that have been advanced and explanations of their meaning and application have been sorely needed and, if widely promulgated and followed, should remove much of the confusion which, heretofore, has been evident. I suggest that much of this confusion has also arisen from lack of common agreement as to the exact meaning of the words and terms used in our discussions of this subject. I am sure I have been equally guilty in this respect and suggest it is time that we select a committee to study vocabulary as well as criteria, so that common understanding and agreement can be had. Thus, I suggest, that the title of this paper should have used the words "coal-cleaning performance" and not "coal-washery performance." My understanding is that "washery" refers to a complete plant and it has additional functions to that of coal-cleaning, such as control of size, moisture, etc. Also, I do not agree with the authors that the formulas given in their paper, the Fraser and Yancey formulas, are necessarily the only ones that can be called efficiency formulas. When a dictionary is consulted one realizes that the words "efficiency" and "efficient" have not precise meanings but only very general ones and must be further defined for each particular use, if they are to have any precise meaning. To my mind, the first of the Fraser and Yancey formulas given should never be used as expressing "efficiency" alone but only by the fuller phrase which truly expresses the kind of efficiency it states, which is "coal recovery efficiency." For complete clarity we then need only define "coal" for the particular circumstances under which the formula is used. This would recognize the fact, fully explained by the authors, that the limits in coal qualities imposed by the market have imposed a factor—and a variable factor—which has influenced any answer obtained by this formula. Such a procedure makes it entirely practical and logical to use the values of any of the qualities of coal—ash, sulphur, phosphorus, specific gravity—or a combination of them to define what is coal for that particular use of the formula. Further, it is clear to me that the criteria to be used must be dictated by the objective in view and the use for which the data are obtained. The authors clearly point out that the Fraser and Yancey coal-recovery efficiency formula is influenced by three factors, "one is determined by the coal, one is dictated by market or use conditions, and one is an inherent characteristic of the cleaning unit itself." The formula which uses the inverse of misplaced material as a measure of efficiency is also a coal recovery efficiency formula and is influenced in like manner by these three factors. As the authors point out, both are useless in obtaining data which enables a direct and valid comparison of the performance of a given cleaning unit on two coals where the other two factors vary or of the performance of two or more cleaning units of different types unless the values of the other two factors are identical. Much of the confusion in our discussions of and literature on coal cleaning has come from failure to understand clearly this fact. Many such comparisons have been made from which erroneous conclusions have been drawn. I am, therefore, particularly glad to see the authors' emphasis on 4?-1e criteria which indicate the "sharpness of separation. I feel that these are the essential criteria

Jan 1, 1952

By Rossiter W. Raymond

The term " pipe-vein " has recently been applied in this country to certain deposits of lead ore in magnesian limestone. The use of the term has been twofold. It has been revived as a term found in textbooks on mineral veins, with the implied or declared assertion that the ore-deposits thus named in this country are similar to those which have borne the title abroad. It has also been advanced as an appropriate name for a new class of deposits, even if such a class had not previously been recognized. In either case, the assumption is that pipe-veins form a group or class by themselves, and are not merely interior and subordinate features in larger deposits. The peculiar mining law of the United States, which regards " the vein," whatever that may be, as the basis of title, lends a special interest to these claims. But the object of this paper is rather to discuss the subject from the standpoint of geology and technical literature. I shall briefly answer two questions: (1) What are pipe-veins as described in technical literature? and (2) Is the name appropriate or necessary for a new class of deposits ? The term " pipe-ore," as applied, for instance, to irregular, cylin-

Jan 1, 1879

By Reuben B. Ellestad, Fremont F. Clarke

In the early days of the lithium industry most of the production was from lepidolite, zinnwaldite, and amblygonite. Nearly all the early extraction processes described in the literature involve heating the finely ground mineral with sulphuric or hydrochloric acid. On subsequent water leaching most of the bases present in the mineral (especially aluminum) are dissolved as sulphates. As a result, the leach solution required extensive chemical purification before the lithium could be precipitated as carbonate. Following the remarkable growth of the lithium industry to its present size, zinnwaldite and amblygonite ores must be considered of minor importance only. Attention is now focused on spodumene, abundant enough in North America to be a major source of supply, and there are important supplies of lepidolite and petalite in Africa. The extraction processes described below all apply to spodumene, although several will also operate on other lithium minerals, such as petalite. Base Exchange with Alkali Sulphates: A distinct advance was made with the disclosures of Wadman and von Girsewalt. In these methods the finely ground silicate ore (spodumene or lepidolite) is intimately mixed with an excess of alkali sulphate (usually K2S04) in at least a 1 to 1 proportion, and the mixture was heated to a relatively high temperature. Base exchange results, with the formation of lithium sulphate. A water leach dissolves the lithium sulphate, together with the excess potassium sulphate. Successful operation of this type of process requires very thorough grinding and mixing, as well as careful temperature control. The use of K,SO, is objectionable from cost considerations since purification of lithium carbonate re- quires the use of potassium carbonate, if the K2S04 is to be recovered and recycled. The lower solubility of K,SO, as compared with Na,SO, is also objectionable, since it limits the concentration of the Li,SO, solution to be precipitated by K,CO,. Early laboratory-scale investigation of this process by Lithium Corp. was not encouraging

Nov 1, 1955

By W. G. Fischer, S. R. Felde

Trona ore at the Westvaco, Wyo., mine of FMC Corp. has been obtained by room-and-pillar methods since the mine began operation. The flat- lying, 10-ft thick trona (Na2CO3.NaHCO3.2H2O) is covered by 1500 ft of weak shale and sandstone, and extraction of pillars on the retreat quite often throws large amounts of weight onto development workings. Weak shales in the roof and floor fail rapidly, and the mine ribs slough to such an extent that mining often becomes very difficult. When this occurs, efficiency goes down, costs go up, and the risk to men and machinery increases greatly. Difficult mining conditions in the early '60s forced a re-evaluation of all presently known mining techniques in bedded deposits. Many room-and-pillar mining plans were compared with the system in use at that time, but none of them offered a better solution to the roof control problem. Longwall techniques were also seriously considered, but machinery was not available that would cut the hard trona seam and still maintain the productivity obtained from room-and-pillar sections. However, since roof control in the longwall methods appeared to be more satisfactory than that found in room-and-pillar techniques it was believed that a new technique using the longwall principle and based on rock mechanics should be tried rather than previously known pillaring methods.

Jan 4, 1966

By Volker Ruth

DURING an experimental investigation of the Kirken dall effect in the Ag-Au system, cracks along grain boundaries in connection with a shift of adjoining crys tallites are observed on the gold-rich side of the couple. Also on the gold-rich side the formation of a zone of small protrusions is found.' The growth law of the width of this zone indicates that the protrusion formation is a secondary effect of diffusion. The protrusions are not found within a distance of approximately 60 from a grain boundary. Unaffected regions along grain boundaries were also observed by Doherty and Davis during precipitation of vacancies in aluminum2 and by Wyon and Lacombe during precipitation of iron in aluminum.3 Thus we may suppose that we have an effect analogous to precipitation in which the crystal tends to maintain its equilibrium vacancy concentration by transporting excess atoms to the surface. At an early stage (i.e., before sintering has influenced the shape of the protrusions) the protrusions have similar shapes (three sided pyramids and roof shapes) and similar orientations within a single grain but vary from one grain to another. Further experiments were carried out on cylindrical Au-Ag single crystal couples. During the weld-

Jan 1, 1963

By Douglas Semmes

THE possible oil territory of Alabama can be readily divided into two regions, the Paleozoic area of the north, and the Coastal Plain province of Cretaceous and younger formations lying to the south. This latter area has received much attention in the last few years and has been described by a number of writers.1 Although the possibilities of the Cretaceous series have been much emphasized by recent writers, the fact remains that the two or, possibly, three localities where oil or as have been found in, anything like paying quantities are confined o the area of Carboniferous rocks. Moreover, almost all of the oil seeps and a good percentage of the gas seeps are confined to this area .2 Topographically, as well as structurally, the Paleozoic area can be divided into three rather well defined provinces: (1) The broad, open Coosa Valley lying adjacent to the crystalline oldland, with comparatively little relief, except for occasional longitudinal ridges and rather intense folding; (2) the plateau region of horizontal or gently warped Pennsylvanian strata broken by occasional anticlinal valleys aligned northeast and southwest, outliers of the Coosa Valley proper, in which

Jan 3, 1920

By Howland Bancroft

This article is not presented as a treatise on tin mines and mining in Bolivia. It deals primarily with the tin situation, and but fragmentary information is given regarding individual properties, generalizations being necessary in so short an article. Data on general subjects related to tin mining in Bolivia are necessarily abbreviated and very incomplete. It is believed that the references to be found in this article will help those interested to a more thorough under-' standing of the general conditions extant in Bolivia. Bolivia produces from one-fifth to one-fourth of the world's supply of tin. The United States consumes about one-half of the world's supply and produces practically none. Tin ore is not reduced in the United States. These facts are not generally appreciated by American mining men. Many conflicting data have been published regarding tin in Bolivia. The Transactions of the Institute contain practically no mention of this subject.1 I have made a study of mines and mining conditions in the west coast republics of South America and have been particularly impressed by the possibilities of the Bolivian field.2 In consequence the thought seems justified that the present meeting would, present a fitting occasion to bring the tin situation in Bolivia to the attention of American mining men.

Jan 9, 1913

By I. N. Zavarine

The observations presented in this paper were recorded during a study of the spheroidizing process. Spheroidization of cementite in steel is either brought about to develop a set of desirable mechanical properties or is an incidental result of mechanical and heat-treating manipulations. Physical properties of steel are materially influenced by the state of the cementite. Conversion of cementite from the lamellar to the spheroidal state is usually accompanied by a decrease of hardness and of strength and by an increase in ductility. The spheroidized structure is usually considered as an ultimate step in the process of the softening of steel. The unorthodox hardening of a 3.5 per cent Ni steel (SAE No. 2330) after a heat-treatment that previously proved entirely suitable for a complete spheroidization of cementite in carbon steels led to the observations that constitute the subject of the present paper. Experimental Procedure The steels used for the experiments described were bought on the market. All were in the form of 3/4-in. round bars. Their chemical compositions are given in Table 1. The spheroidization of cementite in steels can be obtained in several ways. The method used in the present work is, perhaps, the least known. It consists of cyclic heating and cooling of steel, the temperature being

Jan 1, 1939

By I. N. Zavarine

The observations presented in this paper were recorded during a study of the spheroidizing process. Spheroidization of cementite in steel is either brought about to develop a set of desirable mechanical properties or is an incidental result of mechanical and heat-treating manipulations. Physical properties of steel are materially influenced by the state of the cementite. Conversion of cementite from the lamellar to the spheroidal state is usually accompanied by a decrease of hardness and of strength and by an increase in ductility. The spheroidized structure is usually considered as an ultimate step in the process of the softening of steel. The unorthodox hardening of a 3.5 per cent Ni steel (SAE No. 2330) after a heat-treatment that previously proved entirely suitable for a complete spheroidization of cementite in carbon steels led to the observations that constitute the subject of the present paper. Experimental Procedure The steels used for the experiments described were bought on the market. All were in the form of 3/4-in. round bars. Their chemical compositions are given in Table 1. The spheroidization of cementite in steels can be obtained in several ways. The method used in the present work is, perhaps, the least known. It consists of cyclic heating and cooling of steel, the temperature being

Jan 1, 1939