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By Dr. O’Neil Thomas J., Donald W. Gentry

The greatest of all gifts is the power to estimate things at their true worth. LaRockefoucauld INTRODUCTION The primary reason for performing a feasibility study on a proposed mining venture is to investigate all phases of the proposal in as much detail as necessary to justify either dropping the project or continuing expenditures through the next stage. The economic evaluation component of the feasibility study, therefore, must ultimately be based on information which provides an answer to the question, "What is it going to cost?" Unfortunately engineers preparing feasibility studies never have all the engineering or economic information they would like or need. Consequently, the economic portion of the analysis can only be performed if estimates of the various costs associated with the project are made. Project cost estimates, in turn, require estimates of all the physical factors affecting cost components, including anticipated performance of plant and equipment as well as all pertinent geologic, mineralogic, and metallurgical variables. Before useful cost estimating procedures can be applied considerable data must be collected, compiled, and organized. Preparatory work typically includes organization of cost data available for estimating purposes, development of techniques for updating historical costs, and establishing methods of forecasting prices and costs over the duration of the project. Cost estimates for mining and mineral processing projects involve so many features and variables that it is absolutely essential to have some means by which the vast amount of detail can be organized. It is very important to identify, in as much detail as possible, all the cost data available (historical and developed) to the estimator. These costs, after being properly identified in detail, should be com- piled, stored, updated regularly, and made readily available for use in developing new cost estimates Accessing files of current cost information requires a standardized numerical system of classifying cost data. When uniform definitions and procedures are used, every project record contributes to the common store of estimating data.

Jan 1, 1984

By George Steintveit

Det Norske Zinkicompani A/S was established in 1924, on the initiative of the Compagnie Royale Asturienne des Mines. Experimental electrothermic zinc production was carried out on industrial scale for a two-year period, but the problems of electrothermic smelting were not solved. A license for the electrolytic zinc production process was then obtained from the Anaconda Copper Mining Co. A plant for electrolytic zinc production was built, near the small fjord town of Odda in Hardanger, West Norway, The production was based on zinc ore from Spain, and cheap local hydro-electric power. The plant came into operation in 1929. Annual capacity, 36,000 tons. In 1964 a long-term agreement was concluded with Boliden AB by which Det Norske Zinkkompani is secured the raw materials basis for an expansion of the annual capacity to 100,000 tons of zinc, Since World War II, the company has been pursuing extensive research and development programs. As a result, various sections have been rebuilt: nev unloading and storage facilities, a 250 ton per day Fluid Bed Roaster with contact plant, new continuous leaching system, integrating the Jarosite Residue Process, new solution purification section - upgrading the solution quality for a 600 Amp/m2 current density Tank Room operation -, installation of induction furnaces for cathode melting with casting machines and automatic stacking of slabs. Simultaneously, instrumentation, and methods of automatic control have been developed and introduced, providing conditions for optimal plant operations.

Jan 1, 1970

By B. E. Fernow

MINING interests in the Western mountains are very seriously affected by the danger to property and life from destructive snowslides and avalanches. This is a danger which the miner has largely brought upon himself by an improvident stripping of the timber from the mountain slopes, and, therefore, he might be expected to take an interest in the reforestation of the areas thus devastated. A canvass was lately undertaken by the writer to ascertain approximately the extent of the damage suffered from this source, but the difficulty of obtaining reliable data has proved too great to permit, as yet, even an approximation. So much, however, is certain : that the loss of life is considerable, and that much property is destroyed almost every winter. True, neither the number of avalanches, nor their destructiveness, nor the amount of loss compares with what Switzerland experiences. This is due not only to the greater precipitousness of the Alps and to different climatic conditions, but also to the fact that in Switzerland a larger number of settlements is exposed to these dangers. A very complete and interesting official report on the very numerous and destructive avalanches occurring in Switzerland during the season of 1887-1888 has just been published as a contribution to the inquiry, whether and how these dangers can be averted. Peculiar weather-conditions, in addition to heavy falls of snow, were the reasons for the frequency of the phenomenon during that winter. This report records 1094 avalauches, by which 850 houses were destroyed or severely damaged; 84 persons and 752 cattle were buried; traffic on railroads and on highways was greatly interrupted, and the damage to personal property alone was valued at over $100,000. One of these snow-masses covered about half an acre, with a cone 250 feet in height. During the same year in Tyrol the number of avalanches was 3647. Of these 1355 run over permanent beds; that is, they recur annually, so that they are

Jan 1, 1890

Discussion of the paper of Edward Keller, presented at the Butte meeting, August, 1913, and printed in Bulletin No. 80, August, 1913, pp. 2093 to 2115. GEORGE L. HEATH, Hubbell, Mich.:-In the admirable paper quoted, is mentioned the date when the 5-g. assay was first proposed is a standard for refined metal. The author omitted, however, to mention a later paper,1 which contains a proposal for the use of a single " stock solution " of mixed acids, which has been adopted by the American Brass Co. and others. The suggestion is made that such a scheme would save time and manipulation with converter metal. Unless the low current of 0.5 ampere and the large excess of nitric acid, recommended by Mr. Keller, have been proved necessary to hold up antimony-and selenium, the use of the mixed solution which we have adopted will permit the use of 1 ampere of current per square decimeter of cathode surface, until the solutions have become colorless. At this point, we wash the covers and reduce to 0.5 ampere to prevent oxidation or contamination. The ordinary split electrodes have been used. With strong current, at least, the use of an excess of nitric acid tends to the neutralization of the solution before the end of the period, from the formation of too much ammonia., and this is detrimental. Antimony deposits more easily than arsenic, and tends to drag the latter dorm with it. There must, be some such explanation for the fact. that we have made hundreds of deposits of pure cathodes from Lake material containing no antimony, but as. high as 0.5 per cent. of arsenic. By placing an assay beaker in the Frary solenoid, or rotary device, a cathode deposit with less than 0.01 per cent. of impurity is easily obtained in one operation from 3 g. of whitneyite, carrying from 7 to 10 per cent. of arsenic. In such a case, it is necessary to test several times for end point and remove the plate as soon as no brown tint appears (at once) when hydrogen sulphide water is added to the test portion on the spot plate. Edward Keller's proportion,, of solvent figure out as 14 cc. of strong nitric to 11.4 cc. of sulphuric acid (1.84).

Jan 11, 1913

By Charles Will Wright

The present struggle for economic and industrial supremacy by the Communist world is against the United States, its main target, and the other Free World nations. The basis of industrial power is minerals, so the Communist nations are building up mineral production within their borders, often regardless of costs, and are acquiring quantities of mineral products from Free World countries for future use. They are contracting for additional supplies and advancing funds for the development of these quantities. A number of the less developed mineral producing countries of the Free World are being infiltrated by Communists and Communistic influence. This situation is well known, but as yet little has been done to oppose these activities or to awaken the public to their seriousness. The Communist countries are still far behind the Free World Nations in production of many essential minerals. But, shortages are being made up from Free World nations in exchange for petroleum, manganese ore, chromite and other products. Restrictions on shipments of strategic materials to Communist countries have not been maintained.

Jan 1, 1964

By A. C. Fieldner, W. A. Selvig

For purposes of coal classification it is desirable to know the composition and calorific value of the pure coal substance; that is, of the coal free from its ash-forming minerals. Two methods suggest themselves: (1) To free the coal from most of the ash-forming material previous to the analysis; and (2) to analyze the coal as received and calculate the analysis, with certain more or less arbitrary corrections, to the pure-coal basis. Calculation methods are obviously more apt to give correct results with low-ash than high-ash coals. With coals of unusually high ash it would appear preferable to remove, previous to the analysis, as much of the inorganic matter as possible, by float-and-sink or acid-treating methods. Effect of Ignition on Inorganic Constituents of Coal The need of corrections in calculating analysis to the pure-coal basis is due to the fact that the ash, as determined by ignition, is not the same, in either weight or composition, as the inorganic mineral matter in the coal. On ignition a number of changes occur in the coal such as loss of water of hydration of the shaly material, conversion of pyrite (FeS2) to ferric oxide (Fe203) with evolution of the sulfur as sulfur dioxide or possible fixation of more or less of the sulfur in the ash as calcium sulfate (CaSO4), and decomposition of calcite (CaC03) to calcium oxide (CaO). The amount of sulfur from pyrite which remains in the ash as calcium sulfate depends on the amount of calcite and pyrite in the coal. Certain coals high in both calcite and pyrite show relatively large amounts of sulfate sulfur in the coal ash. The determination of total carbon and hydrogen in coal includes, besides the organic carbon and hydrogen, the carbon of inorganic carbonates such as calcite, and the hydrogen of the water of composition of some of the ash-forming minerals. For detailed discussion of corrections proposed for calculations of coal analyses to the " pure "

Jan 1, 1930

PRESIDENT W E WRATHER Washington, D C PAST PRESIDENTS Louis S CATES, New York, N Y CLYDE WILLIAMS, Columbus, Ohio VICE PRESIDENTS ' HOLCOMBE J BROWN,' Boston, Mass ROBERT W THOMAS, Ray, Ariz RLE V DAVELER, New York, N Y C HARRY BENEDICT Lake Linden, Mich DONALD H MCLAUCHLIN, San Fiancisco, Calif VICE PRESIDENT AND TREASURER ANDREW FLETCHER New York, N Y

Jan 1, 1952

Donald H, McLaughlin San Francisco, Calif PAST PRESIDENTS W E Wrather, Washington, D C L E Young, Pittsburgh, Pa VICE-PRESIDENTS C Harry Benedict, Lake Linden, Mich A B Kinzel, New York, N Y Philip Kraft, New York, N Y C V Millikan, Tulsa, Okla RoRobert W Thomas, Boy, Ariz VICE-PRESIDENT AND TREASURER Andrew Fletcher, New York, N Y

Jan 1, 1952

PRESIDENT L E Young', Pittsburgh, Pa PAST PRESIDENTS Clyde Williams, Columbus, Ohio W. E Wrather, Washington, D C VICE-PRESIDENTS Robert W Thomas', Ray, Ariz C Harry Benedict, Lake Linden, Mich D H McLaughlin, San Francisco, Calif A B Kinzel, New York, N Y Philip Kraft, New York, N Y VICE-PRESIDENT AND TREASURER Andrew Fletcher, New York, N Y

Jan 1, 1949

By K. C. Heald

THE places where, yesterday, oil was unknown contain tomorrow's fields. Unquestionably, some states that now yield little or no oil have great potentialities, and developments in these states, although perhaps of less immediate interest than those in regions where great pools now exist, may easily be of greater ultimate importance than the results of exploration closer to known fields. Not long ago, Montana had only a quarter of an oil pool, and that was regarded by many as an accident that had strayed from Wyoming. More recently, the northern line of Louisiana was a dead line that would not be crossed by any Louisiana operator who valued his reputation for sanity. Within the past few months, Colorado has shown that it is far from being a negligible factor in the oil supply of the Rocky Mountain states, and it is now known that western Kansas, long shunned by many reputable geologists and operators, should be reckoned with. There may be a vast difference between what a wildcat well yields and what the well signifies. The fact that no commercial production is encountered may be lamentable and may well be disastrous to an individual or a company, but the same well that spells ruin to one may convey to another the information that will result in opening a new field. In presenting the conclusions, in this paper, the writer recognizes fully the possibility of erroneous deductions, particularly since he has had contact with only a few of the wells that are mentioned. Information comes principally from the scout. maps and files maintained at the Geological Survey by M. E. Latimer and G. K. Drach, without whose cooperation this summary would not be possible, supplemented by some personal contact and second-hand information gained by. conversation and correspondence. However, it is felt that the data contain few errors, and that the conclusions are at least reasonable.

Jan 3, 1924

By G. W. Leney

Iron ores occur in such a wide variety of forms that nearly every kind of prospecting, geological knowledge, and geophysical technique has some application in the search for them. The type of orebody that is considered desirable depends on political and economic considerations, on transportation and markets, on the characteristics of the orebody, on the metallurgy of the ore, and on its comparison with other available ores. In North America, materials that can be efficiently processed into high grade concentrates and pellets are now the object of most exploration work. These are usually shallow, relatively unoxidized, metamorphosed iron formations that are particularly suitable for geophysical methods of exploration. Magnetic surveys are used for the direct discovery of new orebodies, for mapping stratigraphy and structure, and at times to locate oxidized zones in magnetic iron formation. Gravity mapping provides supplementary information, indicates gross tonnages, is useful in regional studies, and can discover non-magnetic orebodies. Electrical methods have not been fully exploited but self-potential, resistivity, applied potential, electromagnetic and perhaps induced polarization surveys all have restricted but highly useful applications. The use of all geophysical techniques promises to increase as the number of exposed easily discoverable orebodies decreases. A high consumption of steel, and consequently of iron ore is the chief characteristic of an industrial society and this consumption has been increasing at an average rate of about 35% every ten years for the past century. To supply this demand, iron ores and iron bearing materials in a wide variety of forms have been exploited on every inhabited continent and in nearly every country. Nearly every kind of prospecting, geological knowledge and geophysical technique has some application in the search for them. The type of orebody that is con-

Jan 1, 1964

By John J. Howard

WE are approaching the depletion of our principal source of iron ore-the Great Lakes deposits, which have provided 85% of the nation's requirements for the past fifty years. This situation presents a threat to our standard of living and our position as a world power. Fortunately, in the Great Lakes region there are still tremendous quantities of potential iron ore in the form of the low iron, high silica rock called taconite. The economical extraction of iron from taconite will insure our future steel supply if no new deposits available to the United States even in time of war are discovered. In the new process presented here, the iron is reduced directly by a simple method and then separated from the silica. The product is "feed," not to the blast furnace, but to the steel plant. This process requires very much less plant, less physical and chemical treatment, and less fuel and auxiliary materials than the conventional ore concentration-blast furnace method. In my opinion, this new, fundamentally different approach offers a better hope for the solution of the iron ore problem.

Jan 5, 1950

One of the best known of the early mining districts of Nevada was that at Eureka, where gold was first produced in 1864. While the most productive period for the district was during the early 1900s, production was maintained until World War II. During this time it is said that the Eureka district produced as much as $200 million from over 3,200 km (2,000 miles) of tunnels and workings. The Windfall Mine was discovered in 1902; and a 100 ton cyanide plant was operated there during the periods 1907 to 1912 and 1932 to 1940. Since 1974, however, Windfall Venture has been operating a unique heap leaching facility on the site of the old Windfall Mine. Gold at the Windfall occurs primarily in the Cambrian Hamburg dolomite which has been "sanded" and in which the original cementing material has been destroyed. The gold is micron sized and is accompanied by anomalous amounts of arsenic and mercury; however, the ore is low in base metals which distinguishes it from the typical Eureka district ores. Mining the ore causes it to break down into very fine sizes, approximately 50% minus 150 microns (100 mesh). Conventional heap leaching by spraying proved to be impossible; and extensive test work on alternate methods, aided by the United States Bureau of Mines, was conducted using 9 m (30 ft) high columns and then large tonnage heaps. The leaching procedure adopted was to build 10.6 m (35 ft) high heaps on a 50 mm (2 in.) asphalt pad covered with a layer of gravel for drainage assisted by perforated pipe drains and gravel-packed sumps. A berm is constructed around the top of each pad and cyanide solution is allowed to “pond” on top of the heap. The resulting percolation is at the rate of 24 liters per sq m per hr (0.6 gal per sq ft per hr), a figure about 2.4 times the average used in other heap leaching operations. The dolomite furnishes its own protective alkalinity and no lime or caustic is used in the solution which contains 0.4 kg per mt (0.8 lb per st) of NaCN. Pregnant solution from the heaps averages about 0.7 g Au per mt (0.02 oz per st) with a cyanide content of about 0. 2 kg per mt (0.4 lb per st) and a pH of plus 9. Addition of NaCN brings the pH of the leach solution up to 11 to 12. Carbon adsorption of the gold was originally done in six enclosed columns mounted in a trailer but five conventional columns have been substituted as the size of the operations has increased. Carbon stripping is with hot caustic, cyanide and 10% ethanol solution. The

Jan 1, 1981

By J. D. Pennock

About a year and a half ago, Mr. Morris, an engineer of the Solvay Process Company, was sent to Belgium and France to study the manufacture of coke in the Semet-Solvay ovens, which were in operation at Havre. With complete plans of construction and a good understanding of the methods of running the ovens, he returned to Syracuse. Work on twelve Semet-Solvay ovens was immediately begun. These ovens, with plant for crushing and washing coal, and the necessary condensers, scrubbers, and concentrator for the recovery of the byproducts are nearly finished, and will soon be in operation. As the work approached completion it became necessary to determine what coal should be used. Accordingly, a chemical investigation of the various bituminous coals was made. I. Investigation of Coals. The samples of coal taken for analysis were: I. A sample of Reynoldsville coal that had been exposed to the weather for a year; 11. Reynoldsville coal taken from a car direct from the mine; 111. Morris Run lump coal; IV. Morris Run fine coal; V. Coal from the Fairmount Coal and Coke Company; VI. A special enginecoal from Pardee colliery, Phillipsburg, Pa.; VII. South Fork, Pa., coal; VIII. Coal from Laceyville, Ill.; IX. Pittsburgh bituminous coal from Ocean mines (gas-coal); X. Steubenville, Ohio, coal; XI. Evansville, Indiana, coal; XII. Coal from the Ohio Coal Company. Proximate Analysis. I. 11, 111. IV. V. VI. Water at 90° C.,* ..................................... Volatile,. .. 31.14 33.00 17.73 18.12 37.20 23.86 Fixed Carbon,. . 64.49 58.07 71.92 71.89 56.68 73.00 Ash,. .. 4.37 8.93 10.35 9.99 6.12 3.14 Coke,. .. 68.86 67.00 82.27 81.88 61.88 76.80

Jan 1, 1893

By Rossiter W. Raymond

THE lead-mining industry of Missouri, as of other parts of the Mississippi basin, appears to have been paralyzed by the shock of competition with the mines of the States and Territories further west. It is difficult for establishments working galena ores, too poor in silver to pay for extracting it, to compete with the producers of the argentiferous carbonates of Utah and Colorado, who look upon their lead as a byproduct of little value, and are satisfied if it pays the charges of transportation, or the loss in smelting for silver. But simultaneously with this depression in the lead-mining of the Mississippi States, the development of new zinc deposits has caused a notable revival in the mining of zinc ores. There has recently been a sudden and strong rise in the price of spelter, which, though probably to a large extent temporary in character, has given important encouragement to prospectors and miners. Apart from the general recovery of business in the United States from the prostration of the past six years, the cause of the advance in spelter has been the falling off in production, resulting from the shutting down of several leading Western works,-the Martindale and Carondelet works, at St. Louis, and the Consolidated Company in Kansas. At the same time, the principal works at La Salle, Ill., were undergoing repairs, and produced less than usual, while the sheet-mill of Matthieson & Hegeler, at that place, was running as usual; so that this concern, ordinarily a large producer, entered the already depleted market as a buyer. These causes are in their nature transitory, and it is quite likely that spelter will be superabundant in a few months. Having lately received from a well-informed Missouri corres¬pondent some samples of the zinc ores and a general account of the ore deposits of Southwest Missouri, I have thought that it might interest the Institute to examine these specimens, and to hear such brief statements concerning the region as I am able, upon good authority, though without the aid of any personal investigation on the spot, to give. The zinc-bearing territory in Southwest Missouri appears to be very extensive; that is to say, zinc ores have been mined during the last year at various points throughout a district extending from the eastern edge of Kansas, west of Joplin, to a line some 50 miles east

Jan 1, 1880

By Frank C. Smith

THE following article covers the history of a metallurgical campaign, commenced in March, 1905, at the mines of the Socorro Gold Co., in the so-called desert region of Yuma county, Arizona. The results obtained were simply a function of necessity, as will be seen from the description of the local economic conditions and the character of the ores treated. The mines and mill of the Socorro Gold Co. are located near the small village of Harrisburg, about 60 miles from Congress Junction, Arizona, which, at the time this work was undertaken, was the nearest railroad station, and from which all supplies were brought by wagon through the desert, at a cost varying from $10 to $15 per ton in addition to the railroad freights. Wood, the only available fuel, cost $7 per cord. Water for all purposes was pumped to the plant from a well in the valley about 4 miles away. Under the Arizona law, a working-shift is 8 hr. Wages were $6 per day for foremen and mill-men, $4 per day for blacksmiths and engineers, $3.50 per day for miners, and $3 per day for shovelers and trammers. The ore consisted of quartz, in which, above the 250-ft. level, the iron-minerals were largely oxidized and some free gold was visible; below that level few traces of oxidation occurred, and pyrite constituted the principal mineralizer in the quartz, together with occasional pockets of galena and a few eccentric specks of covellite. The 20-stamp mill was equipped with plates for amalgamation, and three Standard tables for concentration. The tails from the tables were elevated by a centrifugal pump to a launder, by which they were conveyed to a 60-ton cyanide-mill for further treatment. The cyanide-mill was erected at so great a distance from the stamp-mill that a separate crew of workers and a separate power-plant were necessary. No arrangement had been made for the treatment of the concen-

Jan 1, 1907

By Rossiter W. Raymond

The lead-mining industry of Missouri, as of other parts of the Mississippi basin, appears to have been paralyzed by the shock of competition with the mines of the States and Territories further west. It is difficult for establishments working galena ores, too poor in silver to pay for extracting it, to compete with the producers of the argentiferous carbonates of Utah and Colorado, who look upon their lead as a by-product of little value, and are satisfied if it pays the charges of transportation, or the loss in smelting for silver. But simultaneously with this depression in the lead-mining of the Mississippi States, the development of new zinc deposits has caused a notable revival in the mining of zinc ores. There has recently been a sndden and strong rise in the price of' spelter, which, though probably to a large extent temporary in character, has given important encouragement to prospectors and miners. Apart from the general recovery of business in the United States from the prostration of the past six years, the cause of the advance in spelter has been the falling off in production, resulting from the shutting clown of several leading Western works,—the Martindale and Carondelet works, at St. Louis, and the Consolidated Company in Kansas. At the same time, the principal works at La Salle, Ill., were undergoing repairs, and produced less than usual, while the sheet-mill of Matthieson & Hegeler, at that place, was running as usual; so that this concern, ordinarily a large producer, entered the already depleted market as a buyer. These causes are in their nature transitory, and it is quite likely that spelter will be superabundant in a few months. Having lately received from a well-informed Missouri correspondent some samples of the zinc ores and a general account of the ore deposits of Southwest Missouri, I have thought that it might interest the Institute to examine these specimens, and to hear such brief statements concerning the region as I am able, upon good authority, though without the aid of any personal investigation 011 the spot, to give. The zinc-bearing territory in Southwest Missouri appears to be very extensive; that is to sap, zinc ores have been mined during the last year at various points throughout a district extending from the eastern edge of Kansas, west of Joplin, to a line some 50 miles east

Jan 1, 1880

By J. E. House, C. J. Lewis

In the solvent extraction process, also referred to as liquid-liquid extraction, the clarified uranium-pregnant sulfuric acid leach solution is contacted with an organic extractant dispersed in kerosene; the uranium enters the organic phase and associates itself with the organic extractants. Simultaneously an-ions or cations, as the case may be, leave the organic extractant phase and enter the aqueous phase. The two phases are then allowed to separate by virtue of their immiscibility. Based on the data available, a generalized procedure for the recovery of molybdenum from the sodium carbonate scrub liquor of acid leach uranium mills using secondary and tertiary amine extractants is presented, as is another generalized procedure for the recovery of molybdenum from the bleed stream of alkaline leach uranium mill circuits. Such economic appraisal as can be made at this stage of the development is also indicated. Molybdenum occurs in most uranium ores. Whether the uranium is solubilized by the acid leach route or by the alkaline leach process, some of the molybdenum present in the ore is solubilized along with the uranium. Molybdenum in uranium mill pregant solutions may cause processing difficulties, among which may be mentioned the poisoning of resins, the precipitation of organo-molybdenum complexes, or the build-up of molybdenum in recycle streams. While the uranium milling industry has been successful in applying measures to overcome the problems arising from the presence of molybdenum in the circuits, such measures nevertheless add to the cost of producing uranium yellow cake concentrate. Table I shows the analysis of typical uranium pregnant leach solutions. Uranium recovery by solvent extraction is presently practiced only in conjunction with acid leach circuits, and it may be noted that of about 16,000 tons of uranium ore daily processed by sulfuric acid leach, more than half of this tonnage follows the solvent extraction route. Uranium mills leaching ore with sodium carbonate-sodium bicarbonate solution (the so-called alkaline leach circuit) do not use solvent extraction. In this case the uranium pregnant solution is sufficiently pure to permit the direct precipitation of uranium concentrate with subsequent recycle of the alkaline leach solution. While solvent extraction procedures may be developed which are economically attractive for the alkaline leach uranium process, this has so far not been the case. The earlier uranium mill solvent extraction circuits used organo-phosphate extraction reagents, among which di-2-ethylhexyl phosphoric acid was popular. It should be borne in mind that uranium in its sulfuric acid leach solution exists in an equilibrium involving uranium in both anion and cation forms: uo + 2S0 = [uo2(so4)2] For this reason uranium may be extracted by either cation extractors or anion extractors and this is likewise true of molybdenum. However, the organo-phosphate extractants also load ferric iron which is usually present in the uranium acid leach solution. For this reason, it is necessary to reduce this solution substantially to the ferrous state ahead of solvent extraction using organo-phosphate reagents. The amines, being anion extractors, selectively reject iron and thus render the iron reduction step unnecessary. In the solvent extraction process, also referred to as liquid-liquid extraction, the clarified uranium-

Jan 1, 1961

By Louis A. Panek

Ground movements in the zone adjoining an active cave were measured at four sites in the San Manuel Mine. Measurements were made to detect extension and inclination, basic components of displacement, which can readily be duplicated by mine personnel using relatively simple equipment. The displacements demonstrated the development of a zone of strain relief surrounding the active cave, within which the ground tends to migrate toward the cave, and extension cracks develop tangential to the cave. This expansion of the ground surrounding an active cave can be exploited to promote future caving; it also creates special problems with respect to the design of an effective ground support system for mine openings in the production area.

Jan 1, 1981

By P. Chiotti, E. R. Stevens

The electromotive force between pure magnesium and Mg-Zn alloys in a fused KC1-LiCl-MgC12 cell was measured over the temperature range 360° to 730°C and for alloy compositions of 0.052 to 0.635 atom fraction magnesium. The calculated activity coefficients of magnesium in the liquid alloys may he represented by the relation These data and the phase diagram were employed in calculating the standard free energy of formation for the compounds MgZn, MgZn2, and MgZn2, In the temperature range from 25° to 590°C the relation ZINC-rich magnesium alloys have been shown to be very effective in reducing various solute chlorides or oxides from fused salts such as KC1-LiC1 eutectic. Such reactions are of interest in the developinent of pyrometallurgical methods for reprocessing nuclear reactor fuels.' As the conceniration of the magnesium is increased beyond 5 to 10 wt pct the extent to which solutes, such as yttrium, lanthanum, cerium, and other rare earths, can be reduced or removed from the salt decreases. This effect is due to the resulting change in the activity of the solutes in the Zn-Mg alloy as well as the change in the activity of both the zinc and mag- nesium. The purpose of the present investigation was to determine the thermodynamic properties of the Zn-Mg system which, in addition to yielding information on the alloying behavior of these two elements, would permit a more quantitative understanding of the above reactions. Since this investigation was initiated several publications have appeared in the literature giving results on the thermodynamic properties for the liquid alloys of this system. 2-4 Kozuka, Moriyama, and Kushima3 measured the vapor pressure of zinc over four different alloy compositions by a carrier-gas technique. Eremenko and Tukashenko2 and Terpilowski4 measured the electromotive force between pure magnesium and various alloys in a fused salt cell. Earlier work has been summarized by Hultgren, Orr, Anderson, and Kelley.5 In the present investigation electromotive-force measurements were made on a cell of the type The temperature range covered for the lower-melting alloys was roughly 375° to 730°C. These data were employed in calculating the thermodynamic properties for the liquid alloys and in conjunction with the phase diagram,' reproduced in Fig. 1, were used in calculating the standard free energy of formation of the compounds MgZn, MgZn2, and Mg2 Zn11. The results obtained are compared with available data from the literature. MATERIALS AND EXPERIMENTAL PROCEDURES Materials employed were: Bunker Hill slab zinc, 99.99 pct pure; Ames Laboratory magnesium containing 13 ppm N, 195 ppm C, and trace amounts of calcium, copper, nickel, and silicon; reagent grade KC1, LiC1; and high-purity MgC12 obtained from Dow Chemical Co. The electrolyte consisting of KC1-LiCl eutectic (44.4 wt pct LiC1) to which was added 15 wt pct MgCl2, was dried in a quartz tube by heating to 340° C under vacuum for a period of 4 to 5 hr, and then passing HC1 through the salt as the temperature was slowly raised to above the melting point of the salt. After about 3 hr the HC1 was shut off and the system flushed with argon and then vacuum applied for 1 hr. The salt was finally siphoned through a sintered glass filter and cast into a Pyrex container which was sealed and

Jan 1, 1965