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By C. H. Fulton

Page Introduction........................... 280 Distillation Products from Reduction of Zinc Ore........... 281 Preliminary Investigations..................... 290 Equilibrium of Reaction Zn + CO2 + ZnO + CO in Temperature Range of Condensation........................ 293 Requisites for Successful Condensation................ 299 Discussion............................ 300 Introduction The study of the condensation of zinc from its vapor was undertaken to shed light on certain problems encountered in large-scale electric zine-furnace work. recently conducted. It is a matter of common knowledge that one of the disadvantages of the arc type, electric zinc furnace, is the production of a large amount of blue powder and proportionately little liquid spelter, for, as stated by Stansfield,l "A notable defect in the electric smelting of zinc ores is the difficulty experienced in obtaining the distilled zinc in the liquid state; ...... when zinc ores are smelted electrically, very little liquid metal is commonly obtained, nearly all of the zinc being in the state of powder." This difficulty was not encountered in the electric furnace used12 the main difficulty being the destruction of the fire-brick lining of the large condenser, in certain parts, and the formation of .some oxide and dross coatings on the condensing surfaces. The reason for these difficulties could readily be explained by the infiltration of air whenever the condenser was changed from one retort base to the other, the zinc absorbed in the fire-brick forming oxide and causing rupture by its expending volume. Two facts, however, tended to disprove this theory for the rupture of the fire-brick lining: first, the large distilling retort, lined with fire-brick, which was shifted from charge to charge on alternate bases at temperatures between 1200 and 1300 C., fully exposed to the air, showed no signs of disintegration whatever; second, marked disintegration in the condenser occurred .only in places that were at tempera-

Jan 1, 1919

By J. H. Allport, C. Garnsey

During the latter part of 1916 and the early months of 1917, due to war activities, there was a threatened shortage of coal which resulted in panic among consumers and a rush to obtain coal at once at any price. As a result of this insistent demand for immediate delivery, prices were bid up by the consumers to unprecedented heights; spot coal which had previously been selling at from $1.50 to $2 per ton was bid up to $5, $6, and, in exceptional cases, as high as $7.50 or more per ton. Then when the April, 1917, contract period arrived, contracts could be made only at prices ranging from $3 up to $5 and $6 per ton for the year's delivery. This condition caused such a demoralization of the business, and SO much complaint, that some action to regulate prices was considered essential by the National Administration. Lane-Peabody Agreement In May, 1917, a committee under the chairmanship of F. S. Peabody, of Chicago, was appointed by the Council of National Defense, through Mr. Lane, to consider the whole question of bituminous coal. This committee, with the Secretary of the Interior, Mr. Lane, after numerous meetings and long negotiations with the operators throughout the country, announced on June 29 an agreement between the Committee and the producers, fixing a tentative maximum price for bituminous coal throughout the country at $3 per net ton f.o.b. mines, to which was added 25 c. for selling commission to wholesalers. This plan was based on the idea of fixing a maximum price, high enough to greatly stimulate production, with the expectation that the laws of supply and demand would, with ample production, operate to maintain fair and just prices for coal throughout the country.

Jan 1, 1920

By H. F. Silliman, Daniel R. Hull, Earl W. Palmer

The brass-rolling industry has not had a great deal of experience with antimony in its product. There have been some recent excursions with antimony as a corrosion inhibitor in tubes, but in sheet brass it has been regarded with apprehension and generally avoided. This is not to say that contaminations have never occurred, and probably a great many brass mill men have had their own ideas on the effect of such contamination. Our own views were based upon certain experiences some years ago with strip castings that split lengthwise in the early stages of rolling. The nature of this splitting is shown in Fig. I, from a photograph taken in 1922 as a record of 20 bars of 65-35 common brass made with an antimonial brand of copper. These bars were cast 6¾ in. wide by I in. thick by 45 in. long. In the first pass through the rolls, 19 of the 20 split lengthwise throughout their length, while each half curved outward in a wide arc as it emerged from the rolls. In those days, if splitting was not a frequent occurrence, it was not unfamiliar. One can recall periods of short duration when large amounts of common brass would behave in this way. There was nothing imaginary about these spells. The affected metal would split lengthwise in the breakdown rolls, and no maneuvering of mill practice made any difference. The condition would descend like a plague, demoralize the mill for several days, and disappear. It is doubtful if anyone knew the cause—however many explanations may have been current. In 1921 a quantity of split brass was traced to the use of fired small-arms

Jan 1, 1943

By J. B. Davis

This paper has been prepared at the suggestion of Mr. Dunbar D. Scott, to supplement his " Evolution of Mine-Surveying Instruments."† Before entering into a detailed history of solar instruments, a few remarks will be made touching upon land-surveys in general, and on what has led to the development of these instruments.The oxidation of metals melted in contact with air takes place with dissimilar results. Tin, lead or zinc are examples of a class, the oxides of which float on the surface of the melted metal. First a film is produced, which covers the surface; then, if agitation from any cause exposes new metal to the action of the air, additional oxidation takes place, and the film is increased in volume. This change goes on until a considerable quantity of oxide (or " dross," as it is technically called) is formed; depending, of course, upon the duration of the exposure of the metal to the atmosphere. When such metals are poured, the dross may be skimmed off; and clean metal will be left underneath. The removal of such oxides is, therefore, merely a mechanical process. In the case of copper, however, the result is quite different. The sub-oxide of copper (Cu2O) is readily soluble in molten copper; and therefore, instead of the formation of a film of oxide, to be finally removed as dross, the surface of the metal remains bright and clear, because the oxide has been dissolved as soon as it was produced. It is customary in the process of copper-refining to leave a small quantity of oxide in the metal, in order to oxidize any traces of bismuth, arsenic or antimony which have not been entirely removed. As a result, these metals exist in the commercial product as oxides, and not as metals, which would form an

Jan 1, 1901

By A. S. Dwight

Taking up first the lead field, flotation concentrates offer serious difficulties in handling and in preparing for the blast furnace, quite aside from the problems presented to the furnaceman by the necessity of smelting smaller tonnages of material higher in grade and usually basic in character, with the consequent changes in flux requirements and furnace operation. As received at the smelter, these concentrates are always wet and usually of the consistency of sticky mud. Difficult enough to handle in warm weather, they are worse in winter, when it may be necessary to blast them out of the cars. They hang up in bins and chutes and stick to conveyors, requiring the constant attention of the operators. If dried they become like wheat flour, involving heavy dust losses in handling and in furnace operations. Roasting in hearth furnaces is more difficult than with coarser materials. Dust losses are increased and, what is more serious, the moist concentrates tend to form balls or nodules, which harden and pass almost unaltered through the furnace with consequent high sulfur in the product, while the unballed fine particles lie on the hearth in a dense bed, practically impenetrable to the oxidizing gases, so that roasting takes place only on the surface of the bed. A more prolonged roasting period is therefore required and the capacity of a given furnace is decreased. They are entirely too fine to be charged into the blast furnace, even if thoroughly roasted; excessive flue-dust losses, irregular operation and slowing up of the furnace would be the obvious result. Consequently, it was early recognized that flotation concentrates would have to be put in coarser condition for smelting and the universal method adopted has been the Dwight & Lloyd process of sintering. This did not usually

Jan 1, 1928

By G. R. Fitterer

By means of the C-Sic thermocouple1, liquid metal temperatures have been found to vary much more than was previously supposed, and fortunately these variations can be directly associated with some of our former knowledge which combined to form the "art" of liquid-metal manipulation. Commercial Development of This Device Several types of installations are operating in different plants. There are so many variables in steel plants in regard to operation, procedure, arrangement of pouring platforms, ladles, etc., that most of the installations now in service in this country are "tailor-made"; nevertheless, it is felt that satisfactory gains have been made, inasmuch as each installation has indicated some effect of temperature upon the metallurgical operation, and has pointed the way toward technical and financial benefits. In most cases, it has been necessary to accumulate the temperature data until sufficient metallurgical information is available for the drawing of conclusions. When mechanical difficulties have been eliminated, a distinct correlation of these factors has been obtained. The installations now in service are used for the determination of temperatures in the basic open-hearth furnace prior to tapping and in ladles from both acid and basic furnaces prior to pouring. Some of the installations are in shops making the higher priced steels; others are in "tonnage shops." The errors of human element, smoke screens and emissivity corrections connected with the use of the optical pyrometer do not affect the C-SiC thermocouple readings. The accuracy of the C-Sic thermocouple and the temperatures measured are discussed later in this paper. Temperature Variations or Liquid Pig Iron One well-known discussion between the blast-furnace and open-hearth (or Bessemer) departments has occurred intermittently for more

Jan 1, 1936

By Zay Jeffries

It has been known for centuries that iron and steel could be hardened by cold hammering and that the metal could be restored to the normal condition by heating to a red heat arid cooling, either rapidly or slowly with nearly pure iron, but slowly with steels containing considerable carbon. The art of tempering steels is also very old. When a medium- or high-carbon steel is quenched from a cherry-red heat, the hardness is increased; this hardness can be reduced by heating to various temperatures below the lower thermal critical point,, which is near 700" C. The present paper will not consider these old and well known changes in iron and steel below the thermal critical range but will confine itself to the more unusual changes, some of which have been studied recently. Stromeyer,1 for example, In 1886, reports that both working steel and heat treatment of steel in the blue-heat range arc highly injurious. Recently, however, some metallurgists believe that the straiglltening of warped steel forgings at a blue heat produces a beneficial effect on the metal2 The Engineering Division of the National Research Council has constituted a committee on Physical Changes in Iron and Steel below the Thermal Critical Range, which has the following personnel: K. R. -Abbott, H. C. Boynton, William Campbell, J. V. Emmons, F. B. Foley, H. J. French, H. M. Howe, Zay Jeffries (chairman), F. C. Langenberg, J. A. Mathews, P. D. Merica, A. H. Miller, J. H. Nelson, G. A. Reinhardt, W. E. Ruder, H. F. Wood. This committee is studying several aspects of the physical changes in iron and steel. The results, reported in the literature and obtained by recent experimentation, will be given; this will be followed by a general theoretical discussion of the more important

Jan 1, 1922

By C. A. Mitke

In the Southwest, mcchanical ventilation of metal mines has been receiving consideration for many years. The United Verde Copper Co., in Jerome, has used large mine fans for ventilation and fire-fighting purposes for at lcast 15 years, while the Copper Qucen Branch of the Phelps Dodge Corpn. commenced installing mechanical ventilation in its various divisions 10 years ago.' Since then, with few exceptions, every large mine in this part of the country has installed and put in operation a mechanical ventilating system. The properties of some of these companies consist of from two to six divisions, or separate mines, each of which requires an independent ventilating system. In other words, thirteen copper mining companies, with an aggregate tonnage, when operating at capacity, of approximately 50,000 tons a day, have installed mechanical ventilating systems in their mines. All these mines are within a radius of approximately 200 miles, which constitutes the largest copper-producing area in the world. The capacities of mechanical ventilating installations in these mines range from 100,000 to 300,000 cu. ft. of air per minute, depending on the size of the mine, character of the workings, tonnage produced, etc. The latter varies from 300 to 20,000 tons per day. The mines include both high- and low-grade deposits, the greatest depth of the former, at present, being approximately 2500 ft.; and of the latter, 1200 ft. The volumes of air at present being coursed through the mines are from 60,000 up to 225,000 cu. ft. of air per minute,which, in their relation to the undcrground working force, range from 200 to 800 cu. ft. of air per man, per minute. While not to be taken as criteria, these figures are indicative of the character of the ventilation furnished.

Jan 1, 1923

By Kenneth B. Barnes, George H. Fancher

With the advent of water-flooding into active commercial usage in half a dozen areas in the Mid-Continent, the process passes the experimental stage and joins other methods and processes now in use which have been found suitable in one oil field or another in securing a more profitable production than has existed heretofore. The use of the air-gas lift, acidization, pressure maintenance and repressuring have presented their problems in economics and engineering during their introduction and extended application. When a new field is discovered or attention is turned to an old producing area in which these methods have not been considered, it is to be expected that these problems again arise. While some information is available as to the results obtained by water-flooding in a few localities in the Mid-Continent, the extrapolation of the sand data on which the results are based, for even generalized use in other areas and fields in the region, is hazardous. It is precarious to assume that the same physical condition will obtain in a sand over more than small, special areas. This paper is concerned with a brief presentation of such data as are available to the authors on existing operations, a survey of the region and extent to which application of the method seems most likely to be made, an estimation of the crude reserve existing for such operations, suggestions as to the importance of core analysis in guarding against uncontrolled floods and its usefulness in predicting ultimate recoveries, and comment on some of the economic phases involved. These subjects, as concerned with water-flooding in the East (notably Bradford, Pennsylvania), have been discussed in detail in the literature and are generally well known. Especially is this true of discussions of the mechanical equipment and various lease layouts and development patterns for water-flooding.

Jan 1, 1936

By Walter Crafts

Structural steels containing chromium have become widely used in the last 20 years. In the earlier part of this period the major applications were in chromium-molybdenum aircraft tubing and similar special high-strength steels. During the past 10 years there has been a notable expansion in the use of chromium-bearing steel for structural purposes when welding was utilized for fabrication. The chromium-bearing steels introduced by Saklatwallal (chromium-copper), Kinzel2 (chromium-manganese-silicon), and Schultz3 (chromium-copper) are being extensively used at the present time. General Effects of Chromium Chromium is so widely known for its carbide-forming tendency that its capacity to stabilize oxygen, nitrogen, and phosphorus is often overlooked. In low-carbon steels of the structural type these so-called secondary characteristics become more prominent. For this reason also, chromium in structural steel is definitely a toughening agent. As the carbon content is increased, the more widely known hardening effect becomes more evident. In low-carbon steels chromium increases the notched-bar impact strength substantially. This property persists at subzero temperatures and is utilized for low-temperature service in chromium-copper steel.4 Chromium also reduces any tendency to strain-aging embrittlement. In addition to improving the toughness of steels with the usual impurities, chromium has the specific property of counteracting the brittleness induced by high phosphorus.5,6 In steels low in carbon and alloys, chromium has an almost negligible effect on tensile strength, and a hardening influence is noticeable only in the stronger steels. The ductility of welds adjacent to the base plate is also improved by chromium, both in the range of foolproof welding steels having strengths of less than 80,000 lb. per sq. in. as well as in the higher strength steels.

Jan 1, 1939

By J. Ralph Finlay

In latitude 4" S., about fifty miles from the Pacific, and in the amphitheater on the west flank of the Andes, which is drained by the river Tumbez, is the ancient town and mining district of Zaruma. The town is picturesque in the extreme, perched on a ridge 1800 feet high, between two lovely mountain rivers, looking out upon neighboring hills and valleys clothed in rich green, relieved by many hamlets roofed in red tiles, and, at greater distances on all sides, upon mountain slopes of gloomy forest crowned by the bare summits of the Andes. General Description. The gold-mines, discovered in 1549, mere worked extensively by the Spaniards in the 16th and 17th centuries, until their success was curtailed by the exhaustion of the oxidized surfaceores, and the uncovering of the refractory and hard ores underneath. The industry slowly declined until it was nearly or quite at a standstill in 1878, when an unfortunate English company, organized by Chilian promoters, acquired some of the best properties and began to work them. This company, after an extravagant début, relapsed into a struggle against poverty and mismanagement, and finally collapsed in 1894. In 1896 the English mines and many others, covering most of the district, were acquired by the South American co., formerly the South American Development Co., of New York. (See Figs. 1 and 2.) The vein-formation of Zaruma is extensive and complex, and the ores are somewhat refractory. In the immediate neighborhood of the gold-bearing veins the formation seems to be altogether volcanic, consisting of rather fine-grained holocrystalline diorite; but a few miles away, on either side, some gueisses and crystalline schists are to be found. About four miles south of the mines, and beyond some intervening granites, appear

Jan 1, 1901

By Warren C. Bracewell

At your request, am submitting to you several suggestions for the amendment of our safety code which you felt should be kept up to date. These suggestions are the individual opinions of the several members of the Committee who have expressed (heir wishes to me in the form of letters. I am particularly indebted to Mr. Daniel Harrington, Mr. Wm. Littlejohn, Mr. Warren Bracewell, Mr. James Dalrymple and Mr. Hugh McLeod. Would recommend the following amendments Section 1. Wherever practical trolley wires should be securely hung to roof or timbers at a distance of not less than five feet and not more than six and one-half feet above rail and six inches to one side. Spacing of hangers should be from 20 to 25 feet apart. (Adopted.) Section 2. 500 volts D. C. should not be allowed in any installations. Trolley wires should not carry a voltage of more than 250 D. C. nominal voltage. (Referred back.) Pumps, mining machines and other small machinery units where A. C. power is used should not carry a voltage of more than 220. Large units, such as pumps, motor generator sets and hoists, may use a volt- age of 2,200. When power cables to operate same are of armored construction, cables should be securely buried at all crossings, on haulage-ways or where men travel. (Adopted.) Section. 4. Where power lines pass through door frames or stop- pings they should be properly insulated with porcelain compound or rubber tubing. Wherever men get on or off man-trips in vicinity of trolley wires same should be secure1y guarded and should also be protected with a cut- out switch, same to be pulled before men are allowed to get on or off trips. (Adopted.)

Jan 1, 1926

By T. H. Troller

FOR a long time propeller-type fans have been considered a very adequate means to move great quantities of air against small static pres-sures. They have been in use for this purpose in mines, as well as in other installations. For static pressures of over 2 or 3 in. of water, the centrifugal blower almost ruled the field until very recently. Some attempts were made to use a number of propellers in line. Such arrange-ments made it possible to obtain pressures higher than 2 in. of water, but they complicated the construction and increased its expense, and the efficiencies were not improved. The more recent development of propeller-type fans has been decidedly influenced by the intensive aerodynamic research in connection with aeronautical development, which has taught us, in particular, how to use airfoils properly. The characteristic that makes an airfoil so valuable is the fact that when it moves through the air a high force component, the "lift," acts on it vertical to the motion, while the "drag" in the direction of the flow is small. The ratio of lift to drag is approximately 20 to 1 at the angles at which the profile is used in practice. An element of the turning blade, the movement of which, relative to the air, is mainly in the direction of the plane of rotation, thus experiences only a small "drag" FIG. 1.-DIAGRAM OF FORCES ON WING SECTION. opposing its rotation, and for this reason a relatively small torque is required at the driving shaft. At the same time there is a strong force component at 90° to the plane of rotation. This force is parallel to the propeller axis in the direction opposite to that of the flow of air, with a correspondingly high pressure increase.

Jan 1, 1936

By A. Bascetin

The human requirements have increased rapidly depending on population density and urbanization thus industrialization has grown steadily. As a result of the situation, the greenhouse gas emissions into the atmosphere and the global warming have increased slowly. Today this effect has continued to increase. Therefore, the effects of greenhouse gases in all areas of production must be controlled. The study presents the methods of determination the CO2 emissions (CO2-e) and energy consumption in aggregate production. The aggregate constitute approximately 70% by volume of concrete that has widespread use as construction material in the world. One of the most important elements in today's terms is sustainable use of resources and minimum CO2 emissions (CO2 + CO + NOx + CH4.vb.) at every stage of production of aggregate. Therefore, these elements must be taken into consideration in the aggregate production standards. The choice of production method of aggregate is very important for optimum use of energy and effects of greenhouse gas emissions. So the properties of the aggregate material must be known well to obtain the target. Within the scope of this study, the unit value of CO2-e that release when the production of aggregate in different formations is determined for our country. Thus, the effects of green house gas emission can be evaluated according to the characteristics of material in aggregate production planning. In this study, energies consumed during the production of aggregates at a quarry in Istanbul Cendere region were investigated by taking the different formations encountered at the quarry into consideration. The unit CO2 emission values per ton of produced aggregates were calculated as a result of this investigation. Besides, energy consumption values of previous months at this quarry were taken and the unit CO2 emission values were also calculated.

Jan 1, 2011

By Robert M. Keeney

Important recent developments in the melting and annealing of non-ferrous metals include: 1. Melting of nickel silver in the vertical ring induction furnace. 2. Electric melting of stereotype metal. 3. The rotary-drum gas-fired brass melting furnace. 4. The low-frequency coreless induction furnace. 5. Finishing annealing of brass sheets with city gas1 replacing wood in the large brass-rolling mill. 6. Electric annealing of brass and copper tubing and sheets. 7. Replacement of oil by gas and electricity in the annealing of nickel-silver shells and stampings. Melting Nickel Silver in Vertical Ring Induction Furnace Although over 90 per cent. of the output of the brass rolling mills in the United States is now melted in electric furnaces,2 until recently a considerable part of the output of nickel silver has been the product of the pit fire. The application of the electric furnace to the melting of nickel silver has been slow for several reasons: (I) Until recently no lining has been available that gave a satisfactory life in the vertical ring induction furnace when melting nickel silver; (2) the rocking arc furnace so widely used in the foundry does not appear to have been favored by the rolling mill for melting nickel silver, possibly because the gases present may affect the quality of the alloy; and (3) the exclusive rights to the use of the high-frequency coreless induction furnace (which has proved very satisfactory for melting nickel silver) for the wrought brass industry are controlled by one concern. A little over one year ago the first vertical ring induction furnace to be used for melting nickel silver in the Naugatuck Valley was placed in operation. This was followed by two more in the same mill, and by

Jan 1, 1930

By Robert Pike

THE first authentic description of an iron bath for the deposition of iron is probably that of Bottger in 1846, who used a bath containing ferrous sulfate and ammonium chloride. In 1861, Kramer deposited iron from ferrous chloride solution. Electrolytic iron was produced in 1.869 by Bietz, who used it for making some magnetic tests. In the same year, Klein is said to have worked out his process. Jacobi1 in 1869 described the results obtained in electroplating with iron on copper for making dies and plates for bank notes, by Klein's process. A letter from Klein to Jacobi describes the bath more fully. It consisted of FeSO4 + (NH4)2S04. Lenz2 described ?some properties of electrolytically precipitated iron. He used Klein's bath, FeSO4 + MgSO4 + MgCO3, to neutralize and obtained fine-grained and hard iron. His conclusions were as follows: 1. Electrolytic iron and copper contain gases, notably hydrogen. 2. The volume of gas absorbed by iron varies within wide limits, but it is easy for iron to take up very considerable quantities of gas. 3. The absorption of gas is principally in the first formed layers of iron. 4. When iron is heated, gas begins to come off below 100°, principally hydrogen. 5. Heated to redness, reduced iron oxidizes in water, in part at least at the expense of the oxygen of the water, decomposing it and setting free hydrogen, which is partly or wholly absorbed. Siemens,3 in 1889, was the first to propose a general process embodying a step for leaching a sulfide mineral with ferric chloride or sulfate and a step for regenerating the leach and depositing iron on a cathode in a diaphragm cell. So far as is known, Siemens did not carry out his patent

Jan 1, 1930

Annual Meeting,Wallace, Idaho, Nov. 15-16, 1913. The third annual meeting, which was also the eighth consecutive meeting and the second to be held in the Coeur d'Alène district, was held in Wallace, Idaho, Nov. 15-16, 1913, with side trips to Kellogg-Wardner, Larson, and Mullan, where several mills were visited. The meeting was held jointly with the Montana Section, about 50 members and guests being present. Headquarters were in the Samuels Hotel, sessions being held in the public library. The arrangements and program were in the hands of the following local committee: George W. Roddewig, W. Earl Greenough, H. M. Childs. At 2.30 p.m., Nov. 15, the first session was called to order by Prof. F. A. Thomson, member of the Executive Committee, adjournment being taken to the Mine Rescue car, where Mr. Anderson and his assistant entertained the visitors for nearly two hours by demonstrations of mine-rescue and, first-aid practice, after which the party visited the Hercules mill, mention of which was made in the report of last year when the Section visited the plant. There are, however, several important alterations and additions to the flow-sheet to be noted, such as substitution of Chilean and Hardinge mills for the Huntington mills in the regrinding department; rearrangement of the tables and slimers, with a noticeable addition of the later models of the Franz machines, and the installation of the Wyman flotation process, which has been tried out, or is being tested, with more than ordinary success, on the middlings in several of the mills of the district, the Green Hill Cleveland mill being provided with a 100-ton unit, partly described below

Jan 12, 1913

SPEAKING generally, it may be said that leaching is the simplest method of recovering copper from its ores. Likewise it is perhaps the oldest method of treatment used by copper metallurgists of the modern era. Reliable records indicate that as early as 1752 cupriferous pyrite was leached in the famous Rio Tinto region in Spain. Though the manipulation was quite different from that in use today at Chuquicamata, New Cornelia, Inspiration, and Andes, it resembled that employed by Phelps Dodge at Bisbee, as described in Chapter XIV. Leaching consists of subjecting ore to the action of a liquid solvent or menstruum (usually an aqueous solution) which dissolves the major part of the soluble copper minerals. The resulting pregnant solution is drained off or otherwise separated from the residual ore; and the copper in the solution is then recovered by some appropriate means of precipitation. When sulphuric acid is the lixiviant, as is usual, the simplest procedure is to pass the copper-bearing solution through large troughs containing scrap iron. The iron displaces the copper in the solution, precipitating it as a slime coating the iron and varying in color -from bright copper to a dull black. This may be washed off at intervals, collected as a sludge, dried, and melted with a little fluxing material to produce reasonably pure copper. Usually, of course, the mud is sent to a smelter where most often its destination is the converter or reverberatory furnace. Modern practice uses precipitation on iron only as a complemental process to electrolytic precipitation or deposition, wherein the pregnant copper-bearing solution, acting as the electrolyte in a cell having insoluble anodes and copper cathodes, is depleted of the copper it contains. Cathode copper, 99.5 per cent pure, is produced ready for the market as refined copper, or for a simple process of melting, fire-refining, and casting in

Jan 1, 1933

By Cyril Stanley Smith, Earl W. Palmer

A complete discussion of the literature on the subject of the influence of copper on iron and steel will be published elsewhere.' The present paper is concerned especially with the precipitation-hardening of copper steels, and brief mention will be made here only of the work of Kin-near,2,3 Nehl4 and Buchholtz and Koster,5 who alone have studied this phase of the subject. Kinnear found that normalized low-carbon steel castings containing about 1.0 per cent copper on drawing at temperatures in the neighborhood of 530" C. (1000" F.) increased in tensile strength and yield point, with little decrease in ductility. The maximum effect was obtained with about 0.9 to 1.0 per cent copper, and when the copper exceeded 3 per cent no improvement occurred on reheating. Kinnear did not study the effect of time of reheating—an all important factor where precipitation is concerned. Neh1,6 who apparently was unaware of Kinnear's work, recognized the change as due to precipitation and studied the interdependence of time and temperature of reheating, the temperature of the initial solution heat treatment, and the speed of cooling necessary to retain the bulk of the copper in supersaturated solution and to give an increase in hardness and tensile strength on reheating. Nehl found that if the final rolling or forging temperatures exceeded 700" C. (1300" F.) it was not necessary even to normalize the steel, but full precipitation occurred on merely reheating the forged or rolled shapes at 500" C. (930" F.). Buchholtz and Koster7 studied in detail the precipitation-hardening of a mild steel containing 1.0 per cent copper and 0.5 per cent chromium. From data on the electrical and magnetic properties of copper steels, they drew the portion of the equilibrium diagram in Fig. 1, assuming the

Jan 1, 1933

By Hamid Maleki

Results of geologic investigations, in-mine instrumentation, and numerical modeling are presented for two longwall mines in which pillars with large width-to-height ratios (8 to 9) are used. These investigations revealed that wide pillars unload when subjected to sufficient stress and that pillar unloading is influenced by geologic conditions. Field measurements in mine 1 clearly indicated load transfer from the longwall area toward the gate roads, resulting in pillar failure near the margin of a fluvial channel. Loads were shown to transfer to a harrier pillar (width height ratio equal to 9), contributing to progressive failure of this pillar. Unloading of the barrier pillar was associated with significant load transfer to the two-seam submains to the north of the harrier, contributing to roof falls, floor heave, and rib spalling within the submains. Stress analysis results addressed pillar peak strength and unloading behavior that was in agreement with the measurements and underground observations. Underground observations and stress analyses were completed before and after longwall mining near a six-entry submain in mine 2. This submain was intended to he used as a temporary bleeder and tailgate for a small longwall block consisting of one to two panels, depending on the development schedule in other areas of the trine and observed ground conditions. Numerical modeling using both elastic and inelastic pillar behavior for submain pillars with a width-to-height ratio of 8 was completed before mining began. Results indicated that pillar unloading was likely. During retreat of the first longwall panel, pillars unloaded. as evidenced by progressive rib spalling along the cleats, This behavior was mostly confined to the immediate face area, an observation that was in agreement with the modeling results,

Jan 1, 2000