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By Lawrence Addicks

AT the San Francisco meeting of the Institute last year, I presented, through the courtesy of Dr. James Douglas; some results of experiments on the roasting and leaching of concentrator tailings. After it became apparent that flotation rather than leaching was clearly the better method of handling the particular problem under consideration, before dismantling the experimental equipment, some data were secured on roasting and leaching the concentrate itself in competition with smelting. Some of the results obtained are given in the following paper and they a re of particular interest at this time in. view of the large quantities of flotation concentrates with their somewhat difficult smelting characteristics now being produced. A complete wet process? consists of roasting and leaching the calcines in dilute sulphuric acid produced from the roaster gases, roasting the residue with salt and leaching with dilute tower liquors (the well-known Longmaid-Henderson process) and recovering the copper, silver and gold by cementation or electrolysis or a combination of both. It is evident, however, that the residue from the first leaching, carrying about 20 per cent. of the copper and all of the silver and gold, can be smelted if preferable. In considering the application of the scheme to individual cases, it must be remembered that freight plays a. large part in any reduction process wherein smelting is not conducted at the, mouth of the mine, and that it is not practicable today to build small smelting plants for individual operations. The experiments may be grouped under four main heads: Roasting, leaching, chloridizing residue, and recovery of copper from solutions. The products of two concentrators were used: The Nacozari concentrates were the product of a large modern mill not using flotation, the copper mineral being largely chalcopyrite; and the Tyrone concentrates, the product of an experimental mill including flotation, the copper mineral being chiefly chalcocite. Typical analyses would be as follows:

Jan 9, 1916

By C. J. Bier, J. F. O?Keefe

THIS study was carried out with copper because it represents the simplest form of sintering, in that but one metal is involved and all reactions occur in the solid state. [ ] The present work will cover three variables affecting the sintering process; namely, briquetting pressure, sintering temperature and time in hot zone. Although strength and dimensional changes were observed, this is primarily a metallographic study of the sintering process in copper. The term "sintering" should be understood to mean the process by which the metal powder particles of the compact become united into one body. MATERIAL USED The copper powder used was made from reduced copper oxide, and is typical of a grade used for the mass production of parts formed of metal powders. The screen analysis of the powder was as follows: [ ] The minus 325-mesh analysis was made by using a Roller Air Analyzer.1,2 The apparent density is here defined as the weight per cubic centimeter of the [ ] loose, unpacked powder as measured with the Hall flowmeter. The value for the powder used was 2.57 grams per cubic centimeter.

Jan 1, 1944

By A. E. Outerbridge

I had the honor to present to the American Institute of Mining Engineers at the Pittsburg meeting, February, 1896, a paper having the foregoing title, in which I said : " It has generally been accepted as a fact that cast-iron, under the influence of repeated shocks, becomes brittle, and will finally break under a blow which otherwise it would have withstood. It will probably surprise metallurgists, therefore, to learn that experiment disproves the supposed fact, and establishes exactly its opposite. " The result of about a thousand tests of bars of cast-iron of all grades, from the softest foundry mixtures to the strongest car-wheel metal, enables me to assert with confidence that, within limits, cast-iron is materially strengthened by subjection to repeated shocks or blows." Three tables were appended showing increase of strength

Jan 1, 1905

By R. I. Jaffee, F. C. Holden, H. R. Ogden, A. G. Imgram

The tensile and notch tensile properties of four refractory metals (molybdenum, tungsten, niobium (columbium), and tantalum) and one alloy (Mo-0.5Ti) were investigated. All the materials were evaluated in bar form, and the molybdenum and Mo-0.5Ti also were studied in sheet form. The notch sensitivity of each material was evaluated on the basis of several criteria, including the notch-unnotch strength ratio, the ductility transition, and the fracture transitions. USE of refractory metals as structural materials in aircraft and space vehicles may subject them to low-as well as high-temperature environments. At elevated temperatures, the usefulness of a material usually is limited either by strength considerations

Jan 1, 1962

By H. J. Ramey

As fluids move through a wellbore, there is transfer of heat between fluids and the earth due to the diflerence between fluid and geothermal temperatures. This type of heat transmission is involved in drilling and in all producing operations. In certain cases, quantitative knowledge of wellbore heat transmission is very important. This paper presents an approximate solution to the wellbore heat-transmission problem involved in injection of hot or cold fluids. The solution permits estimation of the temperature of fluids, tubing and casing as a function of depth and time. The result is expressed in simple algebraic form suitable for slide-rule calculation. The solution assumes that heat transfer in the wellbore is steady-state, while heat transfer to the earth will be unsteady radial conduction. Allowance is made for heat resistances in the wellbore. The method used may be applied to derivation of other heat problems such as flow through multiple strings in a wellbore. Comparisons of computed and field results are presented to establish the usefulness of the solution. INTRODUCTION During the past few years, considerable interest has been generated in hot-fluid-injection oil-recovery methods. These methods depend upon application of heat to a reservoir by means of a heat-transfer medium heated at the surface. Clearly, heat losses between the surface and the injection interval could be extremely important to this process. Not quite so obvious is the fact that every injection and production operation is accompanied by transmission of heal between wellbore fluids and the earth. Previously, the interpretation of temperature logs',' has been the main purpose of wellbore heat studies. The only papers dealing specifically with long-time injection operations are those of Moss and White3 and Lesem, et al.' The purpose of the present study is to investigate wellbore heat transmission to provide engineering methods useful in both production and injection operations, and basic techniques useful in all wellbore heat-transmission problems. The approach is similar to that of Moss and White:' DEVELOPMENT The transient heat-transmission problem under consideration is as follows. Let us consider the injection of a fluid down the tubing in a well which is cased to the top of the injection interval. Assuming fluid is injected at known rates and surface temperatures, determine the temperature of the injected fluid as a function of depth anti time. Consideration of the heat transferred from the injected fluid to the formation leads to the following equations. For liquid, Eqs. 1, 1A and 2 are developed in the Appendix. These equations were developed under the assumption that physical and thermal properties of the earth and wellbore fluids do not vary with temperature, that heat will transfer radially in the earth and that heat transmission in the wellbore is rapid compared to heat flow in the formation and. thus, can be represented by steady-state solutions. Special cases of this development have been presented by Nowakl and Moss and White.3 Both references are recommended for excellent background material. Nowak' presents very useful information concerning the effect of a shut-in period on subsequent temperatures. Since one purpose of this paper is to present methods which may be used to derive approximate solutions for heat-transmission problems associated to those specifically considered here, a brief discussion of associated heat problems is also presented in the Appendix. Analysis of the derivation presented in the Appendix will indicate that many terms can be re-defined to modify the solution for application to other problems. Before Eqs. 1, 1A and 2 can be used, it is necessary to consider the significance of the over-all heat-transfer coefficient U and the time function f(t). Thorough discussions of the concept of the over-all heat-transfer coefficient may be found in many references on heat transmission. See McAdams5 or Jakob," for example. Briefly, the over-all coefficient U considers the net- resistance to heat flow offered by fluid inside the tubing, the tubing wall, fluids or solids in the annulus, and the casing wall. The effect of radiant heat transfer from the tubing to the casing and resistance to heat flow caused by scale or wax on the tubing or casing may also be included in the over-all coefficient. According to McAdams, on page 136 of Ref. 5>

By Alexander L. Field

This paper contains an account of experimental results obtained in an extensive investigation of steels containing zirconium. There recently appeared' an announcement by F. M. Becket, at whose suggestion and under whose general direction this investigation was made, a statement of the outstanding features of the work and a brief explanation of the factors that led to its inception. It is not possible, in a paper of this character, to record all of the operating and test data collected, which includes the production of more than 350 heats of steel. The difficulty of a complete presentation is increased by the fact that several lines of experimentation are too incomplete to warrant publication of the results at the present time. In addition to the methods of manufacture and test employed in the work, there is described experimental evidence on which are based certain definite conclusions regarding the remarkable effects brought about by the presence in steel of relatively small percentages of zirconium. When added to a molten steel bath, zirconium combines chemically with dissolved oxygen, nitrogen, and sulfur, in the order named, and is capable of neutralizing the embrittling effect of phosphorus in whole or in part; although in the case of phosphorus there is no evidence so far of actual chemical combination. These effects arc not in the nature of suppositions supported by theory, nor is their existence deduced merely on the basis of analytical evidence. In each phase of its relation to or reaction with the four impurities mentioned, zirconium affects beneficiauy the mechanical properties of the steel to which it is added, in a manner which it is one of the purposes of this paper to explain in terms of a tentative working theory.

Jan 1, 1923

By Alexander L. Field

This paper contains an account of experimental results obtained in an extensive investigation of steels containing zirconium. There recently appeared' an announcement by F. M. Becket, at whose suggestion and under whose general direction this investigation was made, a statement of the outstanding features of the work and a brief explanation of the factors that led to its inception. It is not possible, in a paper of this character, to record all of the operating and test data collected, which includes the production of more than 350 heats of steel. The difficulty of a complete presentation is increased by the fact that several lines of experimentation are too incomplete to warrant publication of the results at the present time. In addition to the methods of manufacture and test employed in the work, there is described experimental evidence on which are based certain definite conclusions regarding the remarkable effects brought about by the presence in steel of relatively small percentages of zirconium. When added to a molten steel bath, zirconium combines chemically with dissolved oxygen, nitrogen, and sulfur, in the order named, and is capable of neutralizing the embrittling effect of phosphorus in whole or in part; although in the case of phosphorus there is no evidence so far of actual chemical combination. These effects arc not in the nature of suppositions supported by theory, nor is their existence deduced merely on the basis of analytical evidence. In each phase of its relation to or reaction with the four impurities mentioned, zirconium affects beneficiauy the mechanical properties of the steel to which it is added, in a manner which it is one of the purposes of this paper to explain in terms of a tentative working theory.

Jan 1, 1923

By E. Swartzman, G. C. Behnke

THE free-swelling index, a numerical value for the free-swelling properties of coal, is being used to an increasing extent in specifying coal for burning in various types of equipment. The empirical standard ASTM method for determining this index uses, as a source of heat, a gas burner which requires frequent calibration because gas pressures are not constant, relatively small changes in gas pressure resulting in rather wide variations in the temperature attained in a crucible and thus in the resultant size of the coke button. Furthermore, the quartz crucibles specified for the test are not standard equipment, and relatively small variations in dimension and wall thickness from those specified often result in rather wide variations in the resultant size of the button. A method of analysis to be satisfactory not only for a scientific laboratory but also for use in industrial control laboratories under varying conditions should employ equipment which is rugged, easily calibrated, and readily replaceable by standard materials. Gas is not universally available as is electricity, and it is generally easier to calibrate and control a simple electric furnace or heater than a gas burner, the voltage not usually fluctuating to the degree that gas pressure does. Quartz crucibles are fragile, and the size specified in the test is not normally used for any other purpose in the laboratory. Although more expensive, the 15-cc platinum crucible, available in all laboratories where volatile matter in coal is determined by the standard ASTM method, is sturdy and standard and easily replaced. Because of these considerations, a modification of the standard method has been developed which employs a standard laboratory 350-w cone heater and standard 15-cc platinum crucibles. The results of numerous tests conducted with such apparatus show conclusively that the free-swelling index values as judged by the buttons produced with this equipment are exactly the same as those obtained by the standard gas burner method. Thus it is suggested that this electric cone heater method employing standard 15-cc platinum crucibles be considered as an alternative to the ASTM method, Designation: D720-46. The free-swelling index of coal is determined by means of the ASTM method, D720-46. This method, which is an adaptation of the crucible swelling test for coal of the British Standards Institution, consists of heating 1 g of coal in a special covered quartz crucible in a regulated gas flame for a period of not less than 2.5 min in which time the temperature of the inner surface of the bottom of the crucible reaches a temperature of 82025°C. The residual coke button is then compared in size and shape with a series of standard profiles shown in Fig. 1 and designated by number from 1 to 9 in increasing order of size. As the method is empirical, it requires rigid standardization of the apparatus and repeated calibration of the gas burner. The dimensions of the low form quartz crucible recommended must be rigidly adhered to as small variations in diameter or wall thickness result in variations in the rate of heat transmission and thus in the resultant size and shape of the coke button. The gas burner must be calibrated almost every time a new set of determina-

Jan 1, 1952

By Mowry Bates

THE following example of the practical application of engineering geology is of interest in that it demonstrates the advantage of keeping accurate records of all wells, whether drilled by one's self or by others, together with the advantage gained by gathering such data during the process of development. The fault described was found in the autumn of 1915, during the hurried development caused by the discovery of the famous Gusher Bend pool in Red River Parish, Louisiana. The writer was at the time employed by one of the operating companies as geologist, and the example is a portion of the routine work. LOCATION The oil fields of northern Louisiana and east Texas are located in Caddo, Bossier, De Soto and Red River Parishes, Louisiana, and Marion County, Texas. A very narrow strip of the eastern portion of the latter is productive. The producing oil pools are known as the Caddo Field, in the northern part, and the De Soto-Red River Field, in the southern. The two fields are 60 miles apart. There are several gas fields between then, but no important supply of oil has been found, though there are several producing wells in the Anona chalk, locally called the chalk rock, in the Elm Grove gas field in Township 16 North, Range 11 West (see Plate 1).

Jan 5, 1918

By L. F. Engle, M. A. Hewedi

SUMMARY Initial interest in using solutions of ammonium salts to leach native copper was documented in notes from an AIME meeting in 1871; By 1916-1917, application of the NH3-CO2-H2O system to recover nonferrous metals attained commercial significance, when it was used as a process for copper recovery by Kennecott Copper Corporation and Calumet & Hecla Mining Company. The Caron work in the early 1920s, Freeport Sulphur Company’s achievements leaching Cuban laterites during World War II, out- standing accomplishments in both eastern and western Canada, recovery of manganese related to the work of Dean -- all serve as landmarks as this One Century Review surveys a base for future technology. Current emphasis on compatibility of metals-producing systems with the need to meet environmental protection criteria provides special encouragement to researchers and engineers to find accept- able ways of recovering metals. The ever-present demand of management to design, build and operate facilities on a profitable basis provides additional impetus to apply information from the technical literature to that need. Examination of the general approach to this paper will reveal much that is firm and positive with respect to empirical results -- extractions, recoveries, amenability to familiar proven equipment and materials of construction common to the industry. Although there are many references, there are gaps in the basic scientific data that if filled could lead to even more usefulness; the paper attempts to indicate where further information is needed.

Jan 1, 1973

By AIME AIME

The following acts of the Directors are reported for the information of members:¬ At a meeting held November 3, 1905, Messrs. Henri Le Chatelier, of Paris, France, and Andrew Carnegie, of New York, N. Y., having been nominated by a large number of members, and recommended by unanimous vote of the Council, were unanimously elected Honorary Members, in recognition of their distinguished services to the arts and professions represented by the Institute. At a meeting held February 7, 1,906, Dr. James Douglas, of New York, N. Y., having been" nominated by a large number of leading members, and recommended by unammous vote of the Council, was unanimously elected an Honorary Member, in recognition of his distinguished services to the practice and the literature of mining and metallurgy, his zealous and loyal devotion to this Institute, his fraternal generosity towards professional colleagues, and his effective advocacy, by public utterance and private example, of the free communication of technical knowledge and experience. At the same meeting, By-Law IV., which now authorizes the Secretary to appoint an '1 Assistant Editor," was amended by substituting the words, " Assistant with the title of Editor." At the same meeting, the resignation of Mr. Theodore Dwight, as Assistant Secretary and Assistant Treasurer of the Institute, was presented and accepted, and the Secretary was instructed to express to Mr. Dwight the thanks of the Board for his loyal and efficient services, and its regret that he could not continue in that position. . [SECRETARY'S NOTE.-Mr. Dwight's resignation, dictated solely by the demands of private business, covers only his immediate management of this office. He is still a Director and Councilor, and a representative of the Institute in matters connected with the new Carnegie Building, etc.-R. W. R.] At the same meeting, the Secretary and the Treasurer reported respectively their appointment of Mr. Henry WT. B. Howard as Assistant Secretary and Assistant Treasurer, to fill

Mar 1, 1906

By Geoffrey Gilbert

The material that forms the basis of this paper was collected in the spring of 1922, during a ten-day visit to Ducktown by the writer in the company of Prof. L. C. Graton. The time available for the work was far too short to allow anything like a thorough study of the deposits, and structural and stratigraphic questions, though they have an important bearing on the origin of the primary ores, were necessarily left untouched. Attention was focussed on the zone of oxidation and enrichment; and by devoting most of our time to the upper levels, open pits, and old workings, and examining the deeper levels only thoroughly enough to obtain a fair idea of the nature of the primary sulfide ore, we were able to make a reasonably complete survey of the various orebodies. With this field work for a background, the writer later made a study, in the Harvard laboratories, of the specimens obtained during the visit. As some of the facts brought to light by this study appear to be new, it seems worth while to set forth the outstanding features and a proposed explanation of them. Much of the Ducktown material that is obviously of greatest significance, as regards oxidation and enrichment, is soft and crumbly. Notwithstanding the desirability of gaining from such material all possible information as to its mineral composition and textural relationships, but little has heretofore been learned regarding it; but, by suitable preparation of this material in connection with the present study, it has been possible to examine it under the microscope without any disturbance of its texture and about as satisfactorily as if it were hard, fresh ore. The information thus gained has contributed measurably to the results set forth in this paper.

Jan 1, 1924

By William E. Harris

Time and experience have demonstrated that by means of the Waelz process zinc, lead, cadmium, arsenic, antimony, bismuth and tin can be volatilized satisfactorily. In this way difficult gold ores are being treated to allow for the recovery of the precious metal. Iron ore containing zinc is being treated to remove the zinc and recover the iron. In Germany, thallium is being recovered in commercial quantities from the zinc oxide fume; indium, germanium and gallium are also concentrated to a degree warranting recovery, even though these rare metals are only recognizable in the ore by means of the spectroscope. The physical, chemical or mineralogical condition of the raw material affects very little the applicability of the process. The name Waelz is derived from the German word Waelzen, meaning a "trundling motion," which very aptly describes the movement of the charge through the slowly rotating kiln. The recovery of zinc and lead by volatilization in a rotary kiln has its origin in a process patented in 1910 by Edward Dedolph, of British Columbia. The Dedolph patent was taken over by the Metallgesell-schaft of Frankfurt-on-Main, Germany, which in cooperation with the Griesheim-Elektron, now a part of a large industrial combine, introduced certain improvements (Ohlmer, Specketer patents), but without bringing the process to a state suitable for large-scale operations. The war temporarily stopped all work on the process, and it was not until after the war that the Krupp Grusonwerk, of Magdeburg-Buckau, Germany, quite independently of the Metallgesellschaft, instituted research work in this field of metallurgy, which in 1923 led to the Waelz process proper. The Krupp Grusonwerk and the Metallgesellschaft A.G. later on collaborated, and by their joint efforts further developed and perfected the Waelz process, which they are marketing together as "Waelz-Gemeinschaft." The process is capable of treating a varied type of material; for instance, oxidized and sulphide zinc ores, calamine (zinc carbonate ore) waste dumps, jig tailings, jig slimes, table concentrate slimes, brass ashes, zinc-bearing iron ores (where the iron sinter is the real objective and the zinc oxide a by-product), electrolytic-zinc leach residues, zinc muffle residues and works sweepings, lead-furnace slags, tin ores and slags, anti-

Jan 1, 1937

By J. E. Tiffany, S. S. Lubelsky

For blasting in coal mines the U. S. Bureau of Mines recommends that permissible explosives be used exclusively, that these shall be fired electrically, and that where feasible the working place shall be cut or sheared. These recommendations are made to promote safety and prevent mine explosions. Although permissible explosives are not flameless, their lower flame temperature and shorter duration of flanie make their use safer than that of nonpermissible explosives. Mixtures of air with both methane and bituminous coal dust, which are liable to occur in coal mines, may be ignited by coming in contact with any type of flame or spark of sufficient temperature and duration or by the firing of a blast. In a working place where a blast is to be fired, in addition to the use of permissible explosives, adequate ventilation for the dilution and removal of accumulations or outbursts of flammable gas should be provided. Bituminous coal mines should be rock-dusted as a means of rendering the coal dust harmless The efficient use of permissible explosives depends upon the proper preparation of the working place, standardized drilling, the strength characteristics of the explosive, and the use of a proper weight of charge. Experienced shotfirers should load, tamp and fire all holes. The major part of the information and data here presented is based on the results of efficiency tests made in large producing mines of Pennsylvania and Illinois. Bureau of Mines Report of Investigations, Serial No. 2697, describes how a standard method of blasting was worked out and put into operation in a mine in southern Illinois.' This paper contains a description of the methods worked out subsequently in another mine in that district. Descriptions of tests in two Pennsylvania mines are given in Bulletins 11 and 19 of the Carnegie Institute of Technology.2 These tests

Jan 1, 1928

By S. W. Zanolli

The history of labor relations in the coal industry of the United States is a study of its collective bargaining. This study of collective bargaining is largely the history of the United Mine Workers of America and its contractual relations with the various coal mining employers who have produced this country's coal over the years under a free enterprise system. There have been other unions in the picture from time to time and some coal miners have mined coal without representation by any union. Even today some 25% of the nation's coal is produced outside of the collective bargaining relationship with the UMWA. However, more than 100,000 coal mine wage employees - well over 75% of the total in the industry - are covered by labor agreements negotiated for them by the UMWA. Practically all of these work in bituminous mines.

Jan 12, 1972

By C. A. Mitke

During September, 1911, the fire area in the Lowell mine continually increased and gases resulting from the fire came through the upcast shaft. These gases contained such a large percentage of sulphur dioxide that the men were unable to go up and down on cages, and, within a comparatively short time, repairs in the shaft mere found to be necessary. Since the fire was in sulphide ores and extended into certain timbered sections, the gases contained varying amounts of SO2, CO2, and perhaps, at times, CO. The temperature in the shaft was generally about 97", and the relative humidity from 97 to 99.5 per cent. The corrosive action of the fumes became apparent when the cables had to be changed more often than usual, the heads of lag screws in the guides of the shaft disappeared, and the cages needed frequent repairs. It also became necessary to repair two compartments of the shaft by putting in 150 ft. of new guides between the 600 and 800 levels and lag screws in nearly all the old guides from the surface to the 800 level. 2. Ordinary Methods of Testing Helmets which were Unsatisfactory. These conditions required all work to be done by men wearing oxygen helmets. The Draeger type was tried, and was used until all repairs were completed. At first the helmets were tested for air circulation and air tightness and the injector mas tested by water gauge according to the methods recommended by the Draeger Oxygen Apparatus Co. Six arrangements, covering these different tests, are illustrated in the catalogue and circulars of the company. After the above tests had been made on the oxygen apparatus, the men still complained about leaky helmets. Small quantities of gas entered the helmets and could not be detected by these methods. The

Jan 1, 1914

By Charles F. Park

Mining in the Pacific Coastal Region has passed through three stages of development. First came the gold rush days, a period when gold and silver were the objects of intensive search. Second was the development of the high-grade base-metal deposits and of the smaller and more refractory precious metal deposits. And third was the modern period that covers the discovery and development of the rarer metals, of large low-grade deposits, and of the industrial and nonmetallic minerals. Brief discussions of the salient geologic features of the region and of a few of the better known mineral deposits are given. The regional geology is favorable for continued exploration and discovery of new deposits and districts.

Jan 1, 1968

By Joseph Pogue

THE writer visited the Muzo emerald mines in July, 1915, and spent six days in their study. This paper embodies the results of his observations, plus information personally communicated by Robert Scheibe, FIG. 1.-SKETCH MAP SHOWING APPROXIMATE LOCATIONS OF ALL IMPORTANT EMERALD MINES AND PROSPECTS IN COLOMBIA. (Data in part supplied by Robert Scheibe, July, 1915.) Professor of Geology in the Mining Academy of Berlin, who at the time of the visit was completing a detailed field investigation of nearly a year's duration of the emerald deposits of Colombia. An elaborate account of this valuable work may be expected at a future date from the pen of Professor Scheibe.

Jan 5, 1916

By S. A. Allison, N. P. Finkelstein

After a brief consideration of the properties of zinc sulfide minerals, their flotation characteristics, and their reactions with thiol collectors, the literature on the activation of the minerals by cupric ion, their deactivation by cyanide, and their depression is reviewed in detail. The distinction between deactivation and depression is stressed. The contradictions in the published results and theories are discussed and attempts are made to resolve them. It is concluded that, whereas all aspects of the subject require further investigation, the study of depression is most likely to yield benefits in practice.

Jan 1, 1976

By J. D. Runkie, A. G. Lyle, G. A. Gillies

Tar evaluation of data obtained by selective flotation from even a simple ore is a very difficult process, and when the ore tested is complex the process becomes extremely difficult and cumbersome The authors, in the course of an investigation into the selective behavior of various flotation reagents on nonmetallic minerals§ were confronted with an aggravated form of this difficulty, owing to the large mass of data that had accumulated over a period of years They finally devised a method whereby the results of the various flotation tests could be correlated and interpreted by means of graphs representing recoveries and rejections of the component minerals in the ore This method of graphical analysis proved so useful in nonmetallic flotation that it was afterwards applied to sulphide flotation, where it yielded equally satisfactory results Since this method of analysis leads to very definite conclusions as to the effect of changes in reagents and flotation procedure, it is felt that a wider application of the method might assist the industry by reducing the amount of test work required, and possibly increase the accuracy of the final analysis GRAPHS In Fig I, four curves are plotted on the same graph with cumulative percentages as ordinates and cumulative weights as abscissas In this instance the four curves are named, respectively the barite-recovery curve, the limestone-rejection curve, the silica-rejection curve, and the summation curve In these tests barite was the mineral concentrated, therefore a barite concentrate was produced Definitions Before explaining the curves in detail it might be advisable to define several new terms, such as "percentage rejection," "summation index," and "summation curve," as well as the word "test," which has been used in a special sense. A "test" will include all the operations performed upon a batch of ore from the time it is placed in the rod mill until the last product has been assayed Thus a test may be a comparatively simple procedure producing only one concentrate and a tailing, or it may be a very complicated procedure producing five or more concentrates of a specific mineral as well as a tailing The number of concentrates produced will depend entirely upon whether the collector was added to the pulp in the flotation cell in one lot or was added in five or more portions Percentage Rejection-The ability of a selective flotation collector to reject an undesired mineral is just as important as its ability to collect the desired mineral The percentage rejection curves shown on the graphs give this factor due consideration and its value is calculated as follows Suppose a concentrate contains 5 per cent of an undesired mineral This indicates

Jan 1, 1942