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By J. F. Wolff

EXPLORATION of Lake Superior iron ores is done principally by drilling. The soft iron ores are churn drilled and the harder ores are diamond drilled. In exploratory work in the harder formations, where the diamond drill is used, the sample comprises both core and cuttings. The care given in handling and preserving the core depends on the im-portance that may be attached to certain characteris-tic strata in different formations. The following instructions for the care of core samples are issued by the Oglebay Norton Co. for diamond drill work done for them on the Gogebic Range of Michigan: The driller shall be careful upon removing the core from the core-barrel to keep the core in exact order. Not only should the pieces of core be kept in exact relation to each other, but care should be used not to turn them end for end. Core should be placed in the core-box from left to right in each row. Each drill should be furnished with small, hinged cover core-boxes, and each drill should be well supplied with empty boxes. Core remaining at the drill when the drillers are not working should be locked up. The practice of picking sample pieces of core and carrying them away from the drill to be examined in better light, or shown to someone else, is unnecessary and prohibited. The reason for this is that these pieces are seldom returned to the core-boxes and valuable information or "markers" may be lost. If the inspector suspects that a critical point is reached in the drilling and he cannot determine at the drill, he should remove the entire core-box and see that the drill is immediately furnished with an empty core-box. It is customary to split the core longitudinally so that one-half may be ground to a pulp for analysis and the other half may be kept for future inspection. The core should be filed in permanent core-boxes, properly labelled, if the core is to be kept in exact order as taken from the core-barrel. Otherwise, it is often filed in tin boxes inn the way that sludge samples are filed. To obtain the average analysis, the core and cutting samples obtained in the same run are analyzed separately and the analyses are combined in the proper ratio.

Jan 9, 1922

It took the US coal industry 55 years to increase domestic coal production by about 11%-from 568 million tpy in 1920 to today's level of about 630 million tpy. With such a growth record, it would take a few hundred years to double coal production. FEA planners think that it can be doubled in 10 years. "With all the obstacles continuously imposed on coal, the industry's real problem is not growth but survival," says Ray Albrechtsen, board chairman of Mountain States Resources Corp., and "we should consider ourselves lucky if, by 1985, the coal industry won't have been legislated and regulated out of existence."

Jan 5, 1975

By M. S. Enders, L. M. Rogers

The Little Rocky Mountains host epithermal gold-silver bearing vein and stockwork deposits in a syenite intrusive complex. Pegasus Gold Ltd. is currently mining these oxidized deposits by open-pit methods and recovering gold and silver by heap-leach processes. A geologic program has been designed to effectively determine the basic ore characteristics; 1) mineralization; 2) oxidation; 3) structural setting; 4) lithology; 5) alteration; and ultimately, 6) the leachability of the ore. Geologic mapping, sampling, drilling, assaying, and testing are routinely used in exploration, development, production control, mine planning, and ore reserve estimations. Timely and accurate assay results are essential for the program's success.

Jan 1, 1984

By Russell W. Dayton

The metallurgical polarization microscope has been utilized in several researches in the last few years, thus attaining a fair degree of prominence, but little has been written in a manner suitable to a metallurgist concerning the theory of this instrument. In this investigation the theory was carefully studied, and the results are presented here in a detailed manner, yet as simply as possible. The theory is discussed with particular reference to the three chief functions of the instrument: (1) determination of anisotropy; (2) effect of strain; and (3) identification of inclusions. Each of these is investigated experimentally, with especial attention to the mechanism of producing any effect. Where possible, the discussion is supplemented by photomicrographs. The instrument used had numerous defects as a polarization microscope; these and their remedies are discussed. In the microscopic study of transparent mineral sections (chalcography) the use of polarized light has aided tremendously in the identification of a mineral. The determination of strain in transparent substances (photoelasticity) by the use of polarized light has lately become a commercial process, used in testing finished glass articles. The success of the use of polarized light with opaque materials has not been so great. The magnitude of the effects obtained is much less than that of the corresponding effects with transparent materials, and the mechanical difficulties are much greater. Königsberger,"' i in 1909, was the first to apply polarized light to the microscopic study of opaque substances; Endell and Hanemann(2) were the next, in 1913. In 1919 and 1920, Wright(3,4) prepared two papers on the subject. In the first he developed the detailed mathematical theory from the viewpoint of the electromagnetic theory of light, and in the second described the various methods in use, giving improvements of his own. Schwarz(5)

Jan 1, 1935

By Russell W. Dayton

The metallurgical polarization microscope has been utilized in several researches in the last few years, thus attaining a fair degree of prominence, but little has been written in a manner suitable to a metallurgist concerning the theory of this instrument. In this investigation the theory was carefully studied, and the results are presented here in a detailed manner, yet as simply as possible. The theory is discussed with particular reference to the three chief functions of the instrument: (1) determination of anisotropy; (2) effect of strain; and (3) identification of inclusions. Each of these is investigated experimentally, with especial attention to the mechanism of producing any effect. Where possible, the discussion is supplemented by photomicrographs. The instrument used had numerous defects as a polarization microscope; these and their remedies are discussed. In the microscopic study of transparent mineral sections (chalcography) the use of polarized light has aided tremendously in the identification of a mineral. The determination of strain in transparent substances (photoelasticity) by the use of polarized light has lately become a commercial process, used in testing finished glass articles. The success of the use of polarized light with opaque materials has not been so great. The magnitude of the effects obtained is much less than that of the corresponding effects with transparent materials, and the mechanical difficulties are much greater. Königsberger,"' i in 1909, was the first to apply polarized light to the microscopic study of opaque substances; Endell and Hanemann(2) were the next, in 1913. In 1919 and 1920, Wright(3,4) prepared two papers on the subject. In the first he developed the detailed mathematical theory from the viewpoint of the electromagnetic theory of light, and in the second described the various methods in use, giving improvements of his own. Schwarz(5)

Jan 1, 1935

By Charles S. Barrett

There is a road into the microscopic realm that has remained untraveled through all these years of intense activity with high-power optical and electron microscopy. The road is worthy of careful scouting by metallurgists and other investigators, for it leads into relatively new country and it makes some areas accessible that heretofore could be reached only by very indirect paths or by the use of imagination. And when the road passes through familiar territory it frequently permits a new view of commonplace things that should prove of value from time to time. An accepted way to interest people in new sights such as this is to present an illustrated travelogue. This I propose to do, using many pictures taken in my recent exploration of this road. In the manner of travelogues, I shall touch briefly upon a large number of different subjects in physical metallurgy and shall attempt to give an exhaustive treatment of none, for the objective is to provide a means for further research, to interest others in it, and to indicate what appears at the moment to be profitable directions for it to take. The method I shall present involves X-rays, but does not make use of the usual accompaniments of X-ray research such as reciprocal lattices, Fourier series, or the stereographic projection. The method is so simple in its fundamentals that it could have been developed 2o years ago, or perhaps even 30 years ago. It is well to have a destination for our travels, so that when we are through we shall have explored some region of importance, despite our preoccupation with the novel means of transportation and our interest in the sights to be seen along the way. So let us name the Cold-worked State as our destination, and make side trips into the territories known as Recovery, Recrystallization, and Precipitation-hardening. A great many investigations have been made of the nature of cold-worked metal, and a great variety of methods used, many of which are indirect, such as X-ray line intensities, X-ray line widths, calori-metric measurements, and magnetic measurements. Since comprehensive reviews of these investigations have been published in recent years, they need not be discussed here. The investigations that were the direct forerunners of the present work should be first mentioned. In 1931 I became interested in the structure of individual spots in X-ray diffraction patterns.l When a crystal is placed in the narrow pencil of X-rays in a Laue camera, the spots recorded on the film are not always uniformly black, but may have an internal structure. The meaning of this may be understood from Fig. I, which represents a narrow beam containing X-rays of many wave lengths (''general radiation") penetrating a crystal in the direction of the arrow and forming a pattern on the vertical film at the right.

Jan 1, 1945

By T. D. Yensen

AGING is a term that connotes a slow change in properties under ordinary operating conditions. It can be accelerated by increasing the temperature and by mechanical straining. The magnetic properties of iron and some of its alloys have for many years been known to be subject to such a change. But the cause of the change was not recognized until a few years ago after mechanical age-hardening in non-ferrous alloys of the "duralumin" type had been definitely shown, by means of solid solubility curves, changes in electrical resistance and microanalysis, to be caused by slow precipitation of one or more con-stituents from the solid solution. The similarity between the solid solubility curves of such alloys (Fig. 1) and those for iron-nitrogen (Fig. 2) and iron-carbon alloys (Fig. 3) below the Al transformation point suggested at once that magnetic aging of iron might be caused by a similar process; namely, by the slow precipitation of carbon and nitrogen in the form of Fe4N and Fe3C at ordinary temperatures because of a cooling rate that had been too rapid to permit complete precipitation according to equilibrium conditions. This suggestion has since been amply confirmed, particularly by the comprehensive work of Köster1 on the effect of nitrogen and carbon. Typical curves are shown in Fig. 4 for the relationship between aging temperature and coercive force. Previous to the establishment of the precipitation-hardening theory it was thought that the effect of nonmetallic elements like C, N, 0, etc., on the magnetic properties of iron was greatest when these elements were retained in solid solution, atomically dispersed throughout the interstitial spaces of the iron lattice2.

Jan 1, 1935

By E. J. Lintner

CLAY mining in the 'United States is by no means a small industry for approximately ten million tons of shale and clay are recovered yearly. The bulk of this tonnage enters into the manufacture of paving, building and refractory brick, draintile, pots, sewer pipe, stoneware, and wall and floor tile. This group of manufactures is commonly known as the heavy clay products industry. The winning of the raw materials for this industry constitutes merely a step in the manufacturing process because the manufacturer usually owns and operates his own source of supply. The mining of kaolin and the whiteware and chinaware claps, however, is usually a separate industry.

Jan 1, 1936

By George Hunt

THE first practical treatment of wood to prevent decay was devised early in the 19th century. At that time the oaken navy of England, when the nation was fighting for its very existence, seemed doomed to annihilation by the swift ravages of decay. The acute situation inspired a desperate search for preventive measures and resulted in the development of the Burnett, Bethel and Kyan processes for impregnating wood with zinc chloride, coal-tar creosote and mercuric chloride, respectively. In the century that has elapsed, their use has spread throughout the world and the three original preservatives are used today in enormous quantities. Meanwhile, improved processes have been developed, new preservatives discovered, and the practice of impregnating wood to make it last longer has attained a position of major importance in the field of structural materials. USE OF PRESERVATIVES BY THE RAILROADS In the application of wood preservatives in the United States the railroads have been the leaders for the past 50 years or more. Having found that decay is the chief cause of the early destruction of wood and that preservative treatment is the remedy, they have treated their ties and timber in increasing amounts(1)?-in 1925 about 220;000,000 cubic feet. By preservative treatment the Santa Fe Railroad saves annually 1,500,000 ties in its 18,000 miles of track, and many other railroads effect similar savings. (2) In like manner the life of wooden bridges and trestles,(3) poles, marine piling, water tanks and other wooden railroad structures has been greatly increased, reducing the amount of timber required annually to maintain them.(5),(7)

Jan 1, 1927

By D. B. Robinson, J. Lukacs

A knowledge of the equilibrium water content of hydrocarbon systems under pressure is important to the natural gas industry. The information available on the solubility of water in hydrocarbon, hydrogen sulfide, and carbon dioxide systems is reviewed in this paper and the influence of the more important variables such as temperature, pressure and molecular structure on solubility in liquids and gases is discussed. A suitable cbromatographic technique has been developed for determining low concentrations of water. Tailing of the water peaks has been elim inated by adding water to the carrier gas stream The method is applicable for both gas or liquid samples and is effective in the presence of hydrogen sulfide. The experimental study of water solubility in methane-hydrogen sulfide systems at a temperature of 16oF has shown that the presence of hydrogen sulfide causes only a modest increase in water content at pressures up to 1,400 psia. Theoretical considerations and data on pure hydrogen sulfide and carbon dioxide suggest that the effect of both these compounds will be greater at higher pressures and in the liquid phase. INTRODUCTION Before transporting or processing natural gases and gas condensates, it is usually necessary to dry them using suitable dehydration equipment. The design and operation of this equipment requires a knowledge of the amount of water present in the fluid at the reservoir and operating conditions. This is influenced by temperature, pressure and composition, particular1y when certain non-hydrocarbon components are present. Field experience indicates that hydrogen sulfide and carbon dioxide, for example, alter the usual water solubility relationships appreciably. However, an extensive search of the literature does not reveal any quantitative data on such systems. For sweet natural gases, generalized empirical correlations such as the one proposed by Katz, et al,6 can be used to predict water solubility with confidence at most temperatures and pressures of interest. However, existing theoretical relationships do not permit a calculation of the deviation from these curves when polar substances like hydrogen sulfide are present in the system. Thus one must resort to an experimental approach to obtain the necessary information. The fact that laboratory experimental methods frequently involve the use of mercury which reacts with hydrogen sulfide in the presence of water, and that hydrogen sulfide interferes with many chemical reactions specific for water has contributed to the difficulty of studying water solubility in systems containing hydrogen sulfide. In this investigation the water content of a limited member of methane-hydrogen sulfide mixtures was determined using a special technique with gas chromatography. REVIEW OF PUBLISHED DATA Experimentally determined water solubility data have been reported for methane, 14 ethane, 15 propane, 9 n-butane, 16 1-butene, 11 hydrogen sulfide 18 and carbon dioxide. 19 These studies report the effect of pressure, temperature and molecular structure on water solubility in single component gases and liquids. Fig. 1 compares experimentally determined water solubilities in several hydrocarbons, carbon dioxide and hydrogen sulfide at l00F as taken from this

By R. R. Hawkins

PEoperly designed tubing strings make it possible to continue the flowing life of wells beyond the stage where ordinarily they would be put to pumping. Wells no longer able to flow through 2-in. tubing can be made to produce through smaller tubing if conditions within the well are carefully studied and correctly designed strings are installed. In this way, pumping expense may be postponed and in some pools it is within reason that the entire recovery may be obtained by natural flow if maintenance of pressure is practiced. Infrequent tubing changes would be necessary but their cost would be much less than that of installing and maintaining pumping equipment. If small wells are to be made to flow naturally, careful consideration must be given the actual lifting mechanics within the string, so that fairly accurate knowledge of reservoir conditions, especially pressure, is essential. Wells producing between 5 and 25 bbl. daily are classified here as "small wells." Exponential Flow A maximum of the energy contained in the expanding gas must be employed to do useful work if natural flow is to be continued. It is evident that adiabatic expansion would defeat this purpose, therefore the velocity of the gas must be held down to a minimum in order that isothermal expansion may be approached. Of course, true isothermal expansion would not be obtainable in an oil well, hence the use of the term "exponential." 1 Obviously the closer the approach to isothermal expansion, the more efficient the lift. Experiments by the U. 8. Bureau of Mines² have shown that for isothermal expansion to take place in a gas well where water is being produced, a definite relationship exists between the depth of the well and the minimum operating pressure. The latter must be such that the tubing fill-up, if static conditions prevailed, would be equivalent to 14 per cent of the distance between the top of the fluid inside the tubing and the tubing head. It has been observed that variations in this essential ratio

Jan 1, 1932

By W. L. Zeigler

THE gravity concentrator of the Hecla Mining Co. was originally constructed in 1888 by the Milwaukee Mining Co., which was operating the Gem of the Mountains mine. It was purchased by the Hecla Mining Co. in 1900, and placed in operation 2 years later. At that time FIG. 1.-HECLA MINING CO. GEM CONCENTRATOR, GEM, IDAHO. the capacity was only about 200 tons a day, but many additions and changes in equipment have been made so that the present capacity is about 800 tons. One of the outstanding improvements made was the substitution of Callow flotation cells for vanners, which occurred in 1915. The recent building of a flotation plant for treating jig tailings, and the construction of a modern surface plant at the mine, following the

Jan 1, 1927

By W. J. Houk, F. C. Hull

To clarify interpretations of grain structures and to assist in calculations of spatial grain size distributions, plane distribution curves have been determined for random sections through four regular polyhedrons approximating the shapes of metal grains. The characteristics of the distribution curve for the average metal grain are predicted. IT was realized early in the history of metallurgy that metals are polycrystalline aggregates and that the size and shape of crystals affects the properties of the material. Reaumur1 in 1722 employed the microscope to examine the fractured surfaces of steel and of white and gray cast iron and suggested a polyhedral arrangement of the crystals. The first extensive investigation of the form of crystal grains was carried out by Desch.2 He examined the disintegrated grains from a ß brass sample and noted that the number of faces per grain ranged from eleven to twenty and that the number of edges per face varied from three to eight and the maximum occurred at five. While it has been found practical to examine isolated grains only in exceptional cases, it is always possible to make a plane section through the metal and examine the shape of the grain sections on the plane of polish. Desch2 tried to determine the relation between the form of a polyhedron and that of its plane sections for comparison with distribution curves of numbers of sides per grain section of actual metal samples. The polyhedrons investigated were the rhombic and pentagonal dodecahedrons and the orthic tetrakaidecahedron. However, the frequency distributions of the number of sides of plane intersections were not sufficiently characteristic to decide which polyhedron most closely approximated the average grain in a metal. Determination of Statistical Shape of Grain in Space Scheil3 was interested in the problem of calculating the distribution of grain sizes in space from the easily measured distribution of grain section sizes on the plane of polish. Assuming that the grains were spheres and using the plane distribution curve for a sphere shown in Fig. 1, he employed a successive subtraction method to calculate the spatial distribution. In order to evaluate the accuracy of these calculations, Scheil and Wurst4 determined the actual distribution of grain sizes in space in their sample of ingot iron by polishing off successive layers and following every individual grain in a series of micrographs. From curves of mean radius of intersection of a given grain vs thickness of metal removed in polishing, Scheil and Wurst attempted to derive the statistical shape of a grain in space. Their calculated plane distribution curve for this shape is compared with the distribution curve for a sphere in Fig. 1. A table of values based on this curve was prepared for calculating spatial distributions of grains. The calculated and measured spatial distributions of their sample then agreed much better than when a spherical shape had been assumed. In the present paper, an attempt has been made to learn something about the average metal grain by studying in detail the effect of the shape of regular polyhedrons on the plane distribution of areas and shapes of areas produced by random sections through them. From the data presented below, it can be concluded that the plane distribution curve for the average metal grain differs in three fundamental respects from the curve derived by Scheil and Wurst. Polyhedrons Selected for Study The polyhedrons selected for the statistical study are illustrated in Fig. 2 and consisted of a cube, a figure formed by cutting off the corners of a cube at the midpoints of the original edges, a tetrakaidecahedron, and a pentagonal dodecahedron. The length of edge on any one figure is a constant. For the above models the edge lengths were 3.50, 4.00, 2.00, and 2.08 in., respectively. A cube was selected for one of the polyhedrons because of its simple geometry, because it is a form that by repetition can completely fill space, and because it represents a convenient degree of departure from compactness beyond which the shape of

Jan 1, 1954

By T. D. Yensen, N. A. Ziegler

AGING is a term that connotes a slow change in properties under ordinary operating conditions. It can be accelerated by increasing the temperature and by mechanical straining. The magnetic properties of iron and some of its alloys have for many years been known to be subject to such a change. But the cause of the change was not recognized until a few years ago after mechanical age-hardening in nonferrous alloys of the "duralumin" type had been definitely shown, by means of solid solubility curves, changes in electrical resistance and microanalysis, to be caused by slow precipitation of one or more constituents from the solid solution. The similarity between the solid solubility curves of such alloys (Fig. 1) and those for iron-nitrogen (Fig. 2) and iron-carbon alloys (Fig. 3) below the Al transformation point suggested at once that magnetic aging of iron might be caused by a similar process; namely, by the slow precipitation of carbon and nitrogen in the form of Fe4N and Fe3C at ordinary temperatures because of a cooling rate that had been too rapid to permit complete precipitation according to equilibrium conditions. This suggestion has since been amply confirmed, particularly by the comprehensive work of Köster1 on the effect of nitrogen and carbon. Typical curves are shown in Fig. 4 for the relationship between aging temperature and coercive force. Previous to the establishment of the precipitation-hardening theory it was thought that the effect of nonmetallic elements like C, N, 0, etc., on the magnetic properties of iron was greatest when these elements were retained in solid solution, atomically dispersed throughout the interstitial spaces of the iron lattice2.

Jan 1, 1935

By Kichizo Niwa

A LTHOUGH studies on the roasting of ferrous A sulfide have been carried out by several investigators, some disagreements still remain among those results. Schwab and Philinis1 have measured the rate of oxidation by a precise thermobalance and have concluded that the rate is controlled by diffu-

Jan 1, 1958

By Robert H. Richards

The adaptation of European methods of concentrating ores to suit the conditions of this country has followed the lines that simplify machinery, diminish labor and increase capacity. Noteworthy instances are the substitution of hydraulic classifiers for the last one or two trommels in the series, and the substitution of a distributing-tank for the slimes in the place of the Spitzkasten. The question may be fairly asked, At what point do losses become serious in consequence of these changes? It is to study this question that the investigation herein described has been undertaken. After the losses are located and the methods of stopping them are pointed out, it will then lie with the individual mill to decide whether or not the plans proposed will save suficient value to warrant their adoption. In the discussion of sorting followed by sizing, as the terms are used in this paper, me have to deal with the preparation of slimes by the Spitzkasten for subsequent washing upon the slime-table. The Spitzkasten, or pointed box, is an inverted hollow pyramid, generally of wood, usually with four faces or sides coming together in a point below. The sides can have, according to Rittinger, a minimum angle of slope of 50" with the horizontal. The feed-water carrying fine slimes (less than 0.01 inch, or 0.25 mm. in diameter) for treatment is fed at one end and carefully distributed over the whole width. The outlet is over the opposite end. The water-current passes direct from inlet to outlet, and has usually been regarded as a surface-layer pass-

Jan 1, 1898

By N. A. Ziegler

IN every research it is desirable to eliminate as many variables as possible and to leave only a few to be investigated one at a time. Metallurgical problems are no exception. Some of the variables that are difficult to control are the size, the distribution, and the orientation of the grains in a metallic test piece. It is therefore very desirable to obtain isolated metallic grains (single crystals, as they are commonly called) large enough to enable one to study their mechanical and physical properties. The present investigation is a part of magnetic research work on iron and iron alloys, undertaken to obtain, if possible, the magnetic properties of pure iron (Fe). This paper will deal primarily with the preparation of single crystals of iron and their mechanical properties, while another paper, by T. D. Yensen, now in preparation, will deal specifically with their magnetic properties. The work with "single crystals" is attracting more attention every year among the investigators in metallurgy. Van Liempt1 gives an interesting summary of the work done and the different methods used in the preparation of metallic single crystals. Briefly stated, the four principal methods used are the following: 1. The cooling of a liquid metal in such a way that the crystallization would start at one point only, causing the entire liquid to solidify as one crystalline unit. This method can be successfully applied to the majority of the metals that do not have any allotropic transformations in the solid state. It has been used and described by a number of investigators,2 but it has never been successfully applied to iron on account of allotropic transformations.

Jan 1, 1930

By C. C. Harris

The characteristics of some common size distribution equations are critically discussed. A generalized form of several well-known size distribution equations is obtained from a differential equation describing statistical distributions. The equation contains three parameters and can describe the major features of size distributions in the fine and the coarse size regions. A graphical method for its implementation is provided. The application of this and other equations to sets of data are compared both for the quality of fit and from a comminution kinetics viewpoint. If a narrow size range of a brittle material is broken sufficiently to obliterate the feed sizes, but not so severely that excessive secondary breakage occurs, a plot of cumulative fraction by weight undersize (Y) vs. sieve size (X) on a log log grid (sometimes called the Gates-Gaudin-Schuhmann plot)1-3 gives a straight line of slope ~ 1 over much of its range. On closer inspection, deviations in the extreme coarse range covering perhaps 10 to 30% of the total sample may be apparent (frequently, a change in slope from ~ 1 to a value different from unity) together with over-all slight irregular departures from a smooth line. One model of breakage postulates that the same fracture pattern persists throughout all size ranges.4 The fracture pattern is characterized by the slope of the line on a log log grid. Accordingly, a distribution of sizes broken in the manner specified earlier is expected to produce a size distribution having the same slope as that of a broken narrow size range. Additionally, the slight irregularities mentioned above should even out in the summation process, giving a smooth straight line of slope ~1 on a log log plot. This idealized state of affairs does not, however, describe the distribution of a multi-event process such as that for a tumbling mill product. On the average, these curves (plotted again log log) tend to have a slope in the fine region different from and usually less than unity,5 while the coarse size region curves with increasing slope for cases of mild reduction, and with decreasing slope when moderate or severe size reduction has occurred. In addition, there are usually slight irregular deviations from a smooth curve. Most curves display two distinct regions — fine and coarse — and a few curves show one or more intermediate regions. Feed size studies6,7 show an effect which theory is required to explain. For the same material, mill loading and other operating conditions, and the same time of grinding, plotting the dimensionless ratios Y vs. X/(feed size) does not reduce the size distribution data to the same curve. Y vs. X does not correlate the coarse region, but it can provide a crude correlation of the fine region which improves as size diminishes and as grinding time increases. The size distribution in the coarse region is somewhat more dependent on the feed size than is the distribution in the fine region wherein the degree of dependence diminishes as time proceeds; the distribution of sizes in the fine region are determined largely by the nature of the material and the comminution conditions. A comprehensive model of comminution must recognize that several different patterns or modes of breakage can occur in a mill; 5,8,9 that there can be some selection in that some size ranges are broken more than others; and that, while some particles may be the product of a single fracture event, or may even remain unbroken, others result from multiple rebreak-age. Thus, breakage in a tumbling mill is more complex than the Schuhmann4 model admits in that several different types of comminution micro-events* occur rather than just one type, and these events, though different in size scale, are of the same overall pattern as that which is visualized by the model. The concept of an average comminution micro-event has, therefore, a mathematical rather than a physical connotation, at least for tumbling milling. Equations with which to describe particle size distributions have been sought for over half a century.10-13 No equation presently in general use was first derived from an analysis of the statistical mechanics of breakage; whatever theoretical basis the existing

Jan 1, 1969

By A. M. Gaudin, C. S. Chang

Adsorption was measured for barium ion and laurate radical, using radioactively marked agents, over wide range of concentrations. Laurate adsorbed in absence of barium fails to float. With barium, flotation-effective laurate coating needs not exceed 5 pct of monolayer. Barium adsorption then is several fold larger. No barium laurate coating is obtained. IN general, fatty acids or their alkali salts do not cause clean quartz to float. However, the presence of multivalent ions, such as the alkaline-earth metal ions and heavy-metal ions, can activate quartz and thus make it respond to soap flotation. The mechanism of activation and soap flotation of quartz has been studied.'-' The problem was attacked by making flotation tests rather than by careful adsorption measurements on suspensions of ground quartz in solutions containing the activator and the collector. Attempts have been made to determine the adsorption of barium ion and calcium ion on quartz. The results have only qualitative value as the analytical methods were not adequately precise. Artificial radioactivity and progress in radioactivity detection have introduced a new analytical tool, which can have a sensitivity several orders of magnitude greater than that of other methods."-" In the experimental work described in this paper the radioactive tracers, barium 140 and carbon 14, were employed. Lauric acid was synthesized, having a radioactive carbon atom and was used with Ba" to study the adsorption of barium and laurate ions from aqueous solution on ground quartz. Flotation tests, using the vacuum flotation technique,' were run in conjunction with the adsorption experiments. The object of this investigation was to understand better the reaction mechanism of barium activation and soap flotation of quartz. Methods and Materials Quartz Sample Preparation: Lumps of hand-picked quartz, washed free of stains, were reduced in size to —20 mesh in laboratory crushers. The product was boiled in concentrated hydrochloric acid to remove the abraded iron. The cleaned product then was ground dry in a laboratory porcelain mill, using siliceous pebbles, to pass through a 200 mesh screen. The ground product was deslimed by sedimentation at 37 microns. This —200 mesh +400 mesh material was subjected again to boiling with concentrated hydrochloric acid, followed by washing with distilled water and further desliming. The cycle was repeated until no trace of iron could be detected in the wash liquor. During the final washing, the pH of the wash water was checked to insure the complete removal of the acid from the mineral. The quartz then was rinsed with conductivity water. The resulting product was dried in a drying oven and stored in mason jars. The impurities (spectrographic) were as follows: Al, 0.01 to 0.001 pct; Li, Mg, Mn, Na, each less than 0.001 pct; Fe and Cu not detected. The specific surface of the quartz sample was determined by the krypton gas adsorption method.' The average of two measurements was 881 sq cm per g. The calculated specific surface for 37/74-micron quartz particles, using a surface factor of 1.96; is 900 sq cm per g. This is in good agreement with the measured value of 881 sq cm per g. Beta-Counting Method: The radioactive isotope of barium used in the experimental work was barium 140. It has a sufficiently long half-life, 12.8 days, emits high-energy beta particles (up to 1.0

Jan 1, 1953

By A. M. Gaudin, C. S. Chang

Adsorption was measured for barium ion and laurate radical, using radioactively marked agents, over wide range of concentrations. Laurate adsorbed in absence of barium fails to float. With barium, flotation-effective laurate coating needs not exceed 5 pct of monolayer. Barium adsorption then is several fold larger. No barium laurate coating is obtained. IN general, fatty acids or their alkali salts do not cause clean quartz to float. However, the presence of multivalent ions, such as the alkaline-earth metal ions and heavy-metal ions, can activate quartz and thus make it respond to soap flotation. The mechanism of activation and soap flotation of quartz has been studied.'-' The problem was attacked by making flotation tests rather than by careful adsorption measurements on suspensions of ground quartz in solutions containing the activator and the collector. Attempts have been made to determine the adsorption of barium ion and calcium ion on quartz. The results have only qualitative value as the analytical methods were not adequately precise. Artificial radioactivity and progress in radioactivity detection have introduced a new analytical tool, which can have a sensitivity several orders of magnitude greater than that of other methods."-" In the experimental work described in this paper the radioactive tracers, barium 140 and carbon 14, were employed. Lauric acid was synthesized, having a radioactive carbon atom and was used with Ba" to study the adsorption of barium and laurate ions from aqueous solution on ground quartz. Flotation tests, using the vacuum flotation technique,' were run in conjunction with the adsorption experiments. The object of this investigation was to understand better the reaction mechanism of barium activation and soap flotation of quartz. Methods and Materials Quartz Sample Preparation: Lumps of hand-picked quartz, washed free of stains, were reduced in size to —20 mesh in laboratory crushers. The product was boiled in concentrated hydrochloric acid to remove the abraded iron. The cleaned product then was ground dry in a laboratory porcelain mill, using siliceous pebbles, to pass through a 200 mesh screen. The ground product was deslimed by sedimentation at 37 microns. This —200 mesh +400 mesh material was subjected again to boiling with concentrated hydrochloric acid, followed by washing with distilled water and further desliming. The cycle was repeated until no trace of iron could be detected in the wash liquor. During the final washing, the pH of the wash water was checked to insure the complete removal of the acid from the mineral. The quartz then was rinsed with conductivity water. The resulting product was dried in a drying oven and stored in mason jars. The impurities (spectrographic) were as follows: Al, 0.01 to 0.001 pct; Li, Mg, Mn, Na, each less than 0.001 pct; Fe and Cu not detected. The specific surface of the quartz sample was determined by the krypton gas adsorption method.' The average of two measurements was 881 sq cm per g. The calculated specific surface for 37/74-micron quartz particles, using a surface factor of 1.96; is 900 sq cm per g. This is in good agreement with the measured value of 881 sq cm per g. Beta-Counting Method: The radioactive isotope of barium used in the experimental work was barium 140. It has a sufficiently long half-life, 12.8 days, emits high-energy beta particles (up to 1.0

Jan 1, 1953