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By A. W. Fahrenwald

The function of the c1assifier in modern fine-grinding practice is to remove a finished product from the grinding-mill discharge, leaving material that needs further comminution. The classifier, therefore, makes two products: (1) "finished" product, which overflows the rim of the classifier tank, sometimes referred to as "slimes" or as "classifier overflow," and (2) "unfinished" product, which settles to the sloping bottom of the classifier tank and is removed by dragging or raking. This product is generally referred to as "sands" or "oversize." One of the outstanding features of the closed-circuit classifier is its ability automatically to return the unfinished product of the ball-mill discharge to the feed end or scoop box of the ball mill. This is a distinct advantage because it avoids dilution of the ball-mill feed, and, furthermore, the particu1ar method of removing the settled sand, by raking it up the inclined bottom of the classifier, gives a classifier discharge containing a minimum of water. This leads to maximum classifier efficiency, in this type of classifier, because the maximum volume of water is displaced upward by the settling sands. The closed-circuit classifier is required to deliver a finished pulp of closely specified density requirements, therefore added hydraulic water generally is not permitted. Relation of Classifier Efficiency to Grinding Efficiency The energy of crushing, and therefore the cost, according to Rittinger's Law,l is proportional to the new surface exposed in crushing. Since the new surface produced in crushing is nearly proportional to the reciprocals of the diameters crushed to, it is obvious that the cost of crushing in the finer sizes is tremendously greater than in the coarser sizes for equal ratios of reduction. High circulating load of finished sand in the circuit of the classifier and grinding mill is therefore obviously expensive practice. It is the classifier's function to reduce this to a miniMum.

Jan 1, 1930

By W. M. Weigel

The first successful use of the wire saw in slate quarrying in the United States was late in 1926, at the quarry of the Colonial Slate Co. near Wind Gap, Pa. This installation was sponsored and supervised by the United States Bureau of Mines in collaboration with the National Slate Association.' The success of this trial resulted in other installations of wire saws, so that 27 were in operation at Pennsylvania slate quarries2 by October, 1928. Marble Quarrying with a Wire Saw Until recently, little or no attempt has been made to use the wire saw in the quarrying of other stone, but it is believed that its successful use in slate will be followed by attempts to take advantage of its possibilities in other quarrying operations. An example of such a trial is the recent installation of a wire saw at the marble quarry of the Saint Clair Marble Co. near Guion, in the Ozark region of northern Arkansas. This quarry is in a comparatively new district and the decision to open and develop it had to be made in the face of many unknown factors. For this reason, it was essential that the development costs be held at a minimum, and as a wire saw could be installed more cheaply than standard channeling equipment, it was decided to try it out. One factor Largely controlling the decision was that the location was peculiarly adapted to this method. The point of development selected was on the rather abrupt end of a ridge formed on the south by an almost perpendicular bluff along the White River and on the north by a rather steep slope with little or no overburden. By taking advantage of this topography it was possible to place the supporting standards for the sheaves at both the outer and driving end without the necessity of drilling or excavating openings to receive them, and to locate the motive power in line with these standards, which made it unnecessary to deflect the sheaves.

Jan 1, 1931

By D. J. Dunn, J. L. Huiatt, T. E. Norman

Corrosion studies in laboratory ball mills and grinding environment simulations produce corrision rates and total metal removal rates much lower than those recorded in operating production ball mills. The corrosion component of ball metal loss in many mills probably represents less than 10% of the total loss, judging from AMAX experience and recent US Bureau of Mines (USBM) tests. Such small absolute losses are consistent with ball metal loss measured in production ball mill marked ball wear tests to determine effects of corrosion and abrasion resisting properties of alloys in operating mills. These indicate that metal hardness and microstructure determine relative metal loss rates of a given situation. The combination of ore characteristics and grinding process dynamics determine metal loss severity. Alloying for corrosion resistance and modification of the milling corrosion environment yield relatively small metal loss reductions. Alloying and heat treatment to produce high hardness and microstructures of high carbon martensite and, for cast irons M7C3 carbides, produces the lowest metal losses in typical wet grinding applications.

Jan 1, 1986

By Harold B. Foxhall

THIRTY per cent of the mineral wealth of the United States is obtained from seven states: Arkansas, Kansas, Louisiana, Missouri, New Mexico, Oklahoma, and Texas. This area, which produced 84,727,156,000 worth of minerals in 1948, constitutes an almost complete economic unit in relation to mineral resources essential to industry. All of these states are producers of fuels and some of metallics, but in the field of important nonmetallic industrial minerals the picture is near perfection-a mineral any one of the seven states lacks, one of the others has in quantity.

Jan 5, 1951

The income of the Institute is derived from dues, subscriptions to MINING AND METALLURGY and sale of publications. These sources are fortunately supplemented by the interest from invested funds now amounting to over $500,000, a considerable portion constituting endowments for especial purposes. Aside from the medal funds the principal endowments are the James Douglas Fund for support of the Library, the Rocky Mountain Fund and the Seeley W. Mudd Memorial Fund. The income from the two last named is available for the support of research and a variety of other purposes. It is allocated by the Board of Directors upon recommendation of standing committees in each case. 'An active effort is being made to increase the endowments of the Institute, it being felt that unusual opportunities exist for research and public and professional service through the organization.

Jan 1, 1934

By W. W. Norton

THE gradually increasing proportion of sulphide ores which lead smelters of to-day are called upon to handle has caused the roasting problem to become one of ever greater importance. We may look back a score of years or so and recall the old hand roasters, some of which turned out a finely divided roasted product, and others fashioned with a "fuse-box" wherein the roasted ore was slagged. Then came mechanical furnaces of several types, the Brückner cylinder, the Brown-O'Harra, the Ropp, and others, all designed to cut out the cumbersome hand labor of the old reverberatories. Roasting costs were thereupon reduced and tonnages stimulated to a gratifying extent. However, it seems to have been early recognized that this very feature of a greater amount of roasted sulphide ore as compared with oxide ore brought with it a train of difficulties at the blast furnaces. The mechanically roasted ore was fine physically, the blast furnaces were choked and the troubles of the smelterman were not at an end. Then the Huntington-Heberlein pot system of roasting appeared upon the scene, and later on the Dwight-Lloyd machines were invented, and inasmuch as both of these processes were designed not only to roast the ore but to agglomerate it as well, it was apparent that distinct steps in advance has been achieved. At the Murray plant, modern up-to-date roasting practice is fully exemplified and there are now in successful operation roasting furnaces or devices of several sorts: namely, Godfrey revolving-hearth furnaces, Wedge multiple-hearth mechanical roasters, Dwight-Lloyd. sintering machines, and Huntington-Heberlein pots. Godfrey and Wedge furnaces will properly handle material high in sulphur, say ores with 25, 30, and 35 per cent. of that element; D. &.L. machines and H. & H. pots will positively not treat efficiently ores or mixtures containing anywhere near the sulphur content mentioned, but are confined to charges containing in the neighborhood of 15 or 18 per cent. In passing, it may also be explained that, so far as the knowledge of the writer goes, Godfrey and Wedge furnaces do not economically eliminate sulphur to an extent

Jan 8, 1914

By J. Th. G. Overbeek, R. Schumann, P. L. De Bruyn

THE technique of concentrating valuable minerals from lean ores by flotation depends upon the creation of a finite contact angle at the three-phase contact, mineral-water-air. If the mineral is completely wetted by the water phase, contact angle zero, there is no tendency for air bubbles to attach themselves to the mineral. However, when the contact angle is finite, the surface free energy of the system, water-air bubble-mineral particle, can be diminished by contact between the bubble and the particle, and if not too heavy the mineral will be levitated in the froth. With a few exceptions, all clean minerals are completely wetted by pure water. Thus the art of flotation consists in adding substances to the water to make a finite contact angle with the mineral to be floated, but to leave the other minerals with a zero contact angle. The contact angle concept and experimental measurements of contact angles have played important roles in flotation research for several decades.1-3 Nevertheless, there remain unanswered some basic questions as to the scientific significance of the contact angle and the nature of the processes by which flotation reagents affect contact angles.

Jan 5, 1954

By Philip Drinker, R. M. Thomson

In the mining and metallurgical industries, numerous problems arise requiring determinations of solid and of liquid particles suspended in air. Frequently, these problems are of local interest and involve purely economic or operating difficulties; on the other hand, toxic effects from the inhalation or the ingestion of substances suspended in air may be a matter of concern. For checking up process improvements or for determining ventilation efficiencies in problems of this general nature, various methods have been proposed. .Although simpler methods are often satisfactory, precipitation combines several desirable features that other methods lack. This paper is, therefore, devoted to a discussion of portable alternating-current precipitators applicable to the quantitat,ive determination and microscopy of dusts, fumes, and smokes in air. Small particles suspended in gases, such as air, are referred to in the literature as aerosols or suspensoids. Of these terms, suspensoids appears to be preferable as being more nearly in keeping with words in everyday use. In problems involving air pollution by small particles—by suspensoids—it is convenient to distinguish three broad classes based on the size, the degree of dispersion, and the method by which the particles become suspended in the air. Dusts.—Particles or aggregates of particles, 150 to 1 micron in diameter, that are thrown into the air by mechanical agencies are termed dusts. Examples are silica; talc; cement; organic dusts such as hard rubber, starch, and cocoa; flocculated fume, and smoke products. Fumes.—Particles, 0.2 to 1 micron in diameter, formed from chemical or physicochemical reactions are known as fumes. Examples are ammonium chloride, lead and mercury, zinc and magnesium oxides, fogs, and acid mists. Smokes.—Particles, less than 0.3 micron in diameter, formed by incomplete combustion of carbonaceous and other substances are called smokes. Examples are the particles formed from burning tobacco, oil, tar, and gas.

Jan 1, 1925

By P. Sanchez-Mejorada

GEOLOGISTS who are acquainted with the mines of northeastern Mexico realize that the most important lead-silver replacement deposits of the province are confined to a single formation. But since the formation is several hundred meters thick, the author has determined the relative position of the lead mantos in the belief that this information will prove useful in the search for new mines. This article describes the stratigraphic location of lead-silver replacement deposits known in several mines situated in a region comprising part of the states of Coahuila and Nuevo Leon. The area studied extends for 200 km* (125 miles) from east to west and 70 km (45 miles) north to south.

Jan 1, 1958

By C. Alstetter, V. Kerlins

By using alloys with subzero Ms temperatures, this investigation demonstrates that the amount of decomposition of martensite during the quench from austenite may be considerable and especially so in specimens of large cross -sections and high Ms temperatures. The activation energy for decomposition as measured dilutometrically is PREVTOUS investigations of the initial decomposition of Fe-C system martensite have invariably been limited to alloys having M, temperatures above a function of the amount of transformation which has taken place. The amount of transformation is a linear finction of log time. A correction term to the activation energy is derived for dilatometric measurements in which no end-point of the transformation is detected. room temperature. In such alloys the martensite is tempered during the quench to an extent dictated by the quench rate and temperature of formation. This tempering, called quench-tempering, Q-tempering, self-tempering, or auto-tempering, although frequently acknowledged, has not been studied or treated quantitatively. To do so one should obtain absolutely untempered martensite and study its decomposition. This as-formed martensite could be obtained either by extremely rapid quenching, requiring very thin specimens, or by lowering the martensite formation temperature range. The second alternative is more effective, because

Jan 1, 1963

By C. E. Stafford

and tougher, and will carry double the tonnage of any of Dr. Dud ley's soft mils. C. E. Stafford, Steelton, Pa.: I must confess my high ap preciation of Dr. Dadlq's conscientious and painstaking work, and of his scientific methds in obtaining the data; but with his method of handling these results and with his conclusions drawn therefrom 1 canuot agree. The reasons for this difference of opinion I will endeavor to explain. It is apparent on inspecting his Plates 6 and 7 that the majority of the slower-wearing rails are from the north track, and generally have a longer time of service, a greater average tonnage per rail, and a smaller avernge tonnage per year per rail than the faster wearing, the majority of which are from the south track, and gener ally have a shorter time of service, a smaller average tonnage per rail, and a greater average tonnage per year per rail. Have these facts any significance Have these different of conditions to which they are subjected any baring on the relative wearing capacity of these rails I venture to say they have. I think, after a study of Table I (page 676), (an arrangement of linee 17 and 18 of Plate a), in connection with Plates 6 and 7, we will find that the slower wear of the 32 best rails is only partly due to qualities inherent in the rails themselves, but is principally due to external conditions favorable to slower wear. In regard to the north and south track, we know that over the rsoiith track come the loaded cam from the West, and that over the north track these cars return, most of them, empty. It is evident that this means for the north track a less average tonirage per rail per year; or, in other words, a lower wheel tonnage. When the load per wheel is less, the resistance and consequently the wear must, necessarily, be less, other things being equal. Time of service, alee, has an important bearing on the question in hand. It has been only within the last five or six years, as Dr. Dudley has pointed out, that the roadbed of the Pennsylvania Rail road has reached its present admirable condition. Before this time the njadbrd was more elastic, more yielding (and probably not uni tbrmly so) than at present. These circumstalices might cause a sofier rail to be more durable than a harder one, owing to the fact that it ulonId yield rnore or less to the bending force of the passing load and would thus get a bearing on each cross-tie. The harder rail, on the other hatid, being stiffer and more. unyielding, would not

Jan 1, 1881

By Henry J. Welge

Laboortory apparatus has been devised which permits study of the displacement of oil from cores by water and by gas. The cores used contained interstitial brine as well as oil. Experiments were run to determine the comparative effect of varying the properties of the fluids used. No great effect was noted on the maximum displacement achieved. This observation made it unnecessary in initial work to use fluids in their exact reservoir conditions. Consequently, the displacements were run at near-atmospheric pressure in Pyrex glass equipment, using stripped crude oils. Introduction and Theory The chief object of this work has been to determine the efficiency of gas and water as primary agents for displacing oil from reservoir rock under laboratory conditions in which capillary phenomena were predominant. To this end the maximum displacement of oil from cores has been ascertained. This maximum displacement may not be equal to the maximum displacement from a reservoir; but it will be a close approxirnation to it sometimes, and other times the laboratory information will be useful in reservoir engineering predictions. It is] believed that the laboratory experimental maximum represents the upper limit for the reservoir recovery. The experiments were carried out by obtaining cores of interest from the reservoir, and filling the pores with interstitial brine and oil with the restored state tech- nique.1 Then the oil was displaced from the core as described later, either by brine from below, or by gas from above. The former type of displacement suggests analogy to production by water drive, but not to water flooding, for reasons discussed below. The latter type of displacement is believed to simulate production by gas cap displacement. The displacements were performed by what may be termed the capillary-pressure method. The cores are placed in capillary contact with an oil-wetted membrane which has very small pores (about I micron in diameter). Pores of this size will transmit oil but Prevent the Passage of gas or water, unless the Pressures used are higher than the capillary Pressures employed in this work. Accordingly, use of the membrane makes it possible to apply a capillary pressure differential between the displacing phase and the oil in the core. AS in the displacement of brine toward that condition of oil and water distribution existing originally in the reservoir,' it may not always be desirable to reduce the oil saturation in this experiment to an absolute minimum. With reservoirs having small productive closure, it is preferable to evaluate and use a displacing pressure no higher than the capillary pressure, Ap, which will ultimately become available for displacement in the reservoir. This pressure may be calculated from a knowledge of the density of the oil-in-place, do, the density of the displacing phase, dl, and Ah, the vertical distance between the section of the

Jan 1, 1949

By D. B. Masson

THE martensitic transformations occurring in ,B AgCd as a result of cold working at room temp.. a-ture and cooling below room ten1erature have been reported by Masson and Barrett.1 These authors found that simple cooling to 127°K caused body-cen-tered-cubic AgCd containing 53.0 at. pct Ag to transform to an orthorhombic structure, while mechanical deformation at room temperature was found to induce a hexagonal structure. Furthermore, they observed that the temperature at which martensite first appeared on cooling, Ms, and that at which the transformation was complete, MI, as well as the corresponding temperatures for the reversion on heating, As and Af, could be ascertained to ± 1°K, although they report these temperatures only for the alloy containing 53.0 at. pct Ag (51.96 wt pct). In the work reported here the temperature range of the transformation on cooling was studied as a function of composition, and further consideration was given to the relationship between the original bcc structure and the transformation-induced hexagonal and orthorhomic structures. EXPERIMENTAL PROCEDURE All samples studied were in the form of annealed 300-mesh powder and were prepared from the constituent metals in the manner described previously.1 The compositions in weight and atomic pct are listed in Columns 1 and 2 of Table I. Method of determination of transformation temperature was the same as utilized previously1—measurement of the intensity of X-rays diffracted by the transformation product. A diagram of the low-temperature sample mount is shown in Fig. 1. This mount was made to fit a GE model XRD-3 X-ray diffraction unit. The powder sample was varnished to a flat surface on a copper sample holder at A. This sample holder was soldered to a brass rod, B, which was in turn soldered to a second copper rod, C. Rod C could be cooled to 78°K by inserting it into a reservoir of liquid nitrogen, D. A heater coil of nichrome wire was wound at E on the sample holder, and by varying the current through the heater a thermal gradient could be maintained along brass rod B. Sample temperatures from 78°K up could be attained and held as long as needed. The sample holder and nitrogen reservoir were insulated by Styrofoam, F, and the sample itself was protected by two radiation shields, G. The X-ray beam entered and left the sample chamber through windoys in the supporting container at H and I. Sample temperatures were measured by a calibrated copper-constantan thermocouple varnished to the sample holder just out of the beam at A. The low-temperature structure had been found to possess orthorhombic symmetry1 and the expected positions of the diffraction maxima were known. Therefore the sample was aligned in the X-ray beam and the Geiger counter of the spectrometer set to receive the most intense orthorhombic reflection without an adjacent interfering cubic reflection. This

Jan 1, 1961

By R. S. Wagner, H. Brown

Criteria for nucleation with the aid of twin planes during crystal growth from the melt are discussed. It is shown experimentally that bismuth crystals can grow from a subercooled melt in a twinned bismdtic form. A mechanism of growth based on the presence of at least me twin plane is proposed. It is well known that faceted growth can be observed in crystals grown from the vapor phase, dilute solutions, or from the melt. Faceted growth, in which the crystal is bounded by its slowest growing faces, will occur if the growth rate is strongly orientation dependent. The addition of atom layers on a facet plane can only occur by two-dimensional surface nucleation or with the aid of an imperfection. Nucleation with the aid of dislocations was proposed by rank' and observed to be of particular importance in crystal growth from the vapor phase. Nucleation with the aid of two-dimensional imperfections, notably twin planes, was suggested by stranski2,3 and Frank.4 A twin plane, terminating at the growth interface, can form a reentrant step at which nucleation can occur at a much smaller super-saturation (or supercooling) than required for two-dimensional surface nucleation. Nucleation by a twin plane usually results in a fast growth rate along a crystallographic direction parallel to the twin plane. Such a nucleation mechanism, based on the presence of a twin plane, has been used by Dawson5 to explain the growth and morphology of sheet-like crystals of paraffin n-hectane. In recent years more evidence was found that nucleation by twin planes occurs frequently in crystal growth from the vapor phase and from dilute solutions, for example, in cadmium,' barium titanate,7 silver,8 silicon9 and gallium arsenide.10 In crystal growth from a supercooled melt, however, nucleation by twin planes has so far only been observed in materials with the diamond or zinc blende structure. Bennett and Longini11 were the first to recognize the important role a single twin plane plays in the growth of germanium dendrites. Subsequently, it was found that a prerequisite for continued propagation of germanium dendrites is the presence of two parallel twin planes which form a self-perpetuating system of nucleation sites.12 Sili- con and some III-V compounds such as InSb also grow dendritically by twin plane nucleation. It appears that the following criteria must be satisfied in order that nucleation with the aid of twin planes can occur: A) The growth form of the material must be faceted." B) The formation of twin boundaries, by a fault in layer sequence during growth, by plastic deformation, or by an accidental meeting of properly oriented crystals, must be possible. C) Twinning must form a reentrant step where the twin boundary terminates at the faceted growth interface. D) These three conditions are necessary, but in certain cases not sufficient for continued crystal growth with the aid of a twin plane. Depending on interface morphology, a combination of more twin planes is sometimes required to form a self-perpetuating system of nucleation sites. This investigation was carried out with the idea in mind that nucleation with the aid of twin planes is a more general phenomenon and should occur in those materials, grown from a supercooled melt, which satisfy the criteria outlined above. It has been found that crystals of high-purity bismuth grown from a supercooled melt can grow by the aid of a twin plane. In the first two sections the faceted growth form and the twinning elements of bismuth are discussed. In the last section prismatic crystals of bismuth, which appear to grow with the aid of a deformation twin are discussed.

Jan 1, 1962

By G. A. Collins

Being much interested in efficiency-work in general, and an ardent reader of writings on this subject by Frederick W. Taylor and others, as applied to manufacturing-plants, and having served my apprenticeship from mucking to the engineering design of ore-dressing and underground plants, I hope that this paper will lead others to investigate the field more fully, to the improvement of general mine- and mill-operations, as well as the advancement, intellectually, physically, and financially, of the employee and his relations with the employer. If a man who is prepared to look closely and observe broadly starts in Canada and zig-zags from camp to camp to southern Mexico, taking time casually to inspect mines, mills, and smelters, he will be pitifully impressed by the great difference in customs, and the general waste of labor, time, and money throughout the country. He will so seldom observe a dollar's worth of results given in exchange for a dollar spent that he will form a poor opinion of operating-efficiency and management. This highly-scientific department, requiring an amount of skill and executive ability equaled in few, if any, of the professions, certainly falls short of the standard established in our greater manufacturing industries. It is easily said that this is due to the diversity of conditions in mining, milling, and smelting. But on second view it must be admitted that there is room for tremendous improvements in nearly every mining-organization. The proposal of such improvements is often met by the argument that any mine is but a temporary affair, yielding such profits as to make efficiency-work of no consequence; but any business which is profitable and worth doing at all is worth doing on a basis which gives the greatest return on the investment.

Jan 1, 1913

By Robert K. Warner

When a new mine is opened, and often when an operating mine must adapt itself to physical or economic changes, a mining system must be selected in complete detail. In the past the plan chosen was usually the product of the local staff alone, however limited the training and experience of that staff might be, which often resulted in the introduction of methods that were familiar to the staff, but not so well suited to the conditions as others unknown to the local men. A new management, noting the difficulties with the existing layout, might make modifications or complete changes, so that many mines in their history have seen a whole series of mining systems, each somewhat laboriously grafted on to its predecessor. This should not be interpreted as a condemnation of the older staffs for sticking to the tried systems, such as open square-sets in the early days at the Homestake, because they knew it would work after a fashion, nor does the statement apply to the technically trained, and usually broadly experienced staffs of most present-day properties. The older miners did not have the variety of tools and methods, nor the present freedom of transfer of information as to what the other man is doing, and so did the best they could under the circumstances. Finally, the higher grade of the ores made the choice less vital. The ever-increasing need to mine low-grade orebodies, with a fixed or even lower price for the metal produced, has caused an increasing need for low-cost mining. In most new mines this has simplified the problem of selection by eliminating from consideration all of the high-cost systems, but it has also complicated the choice by the necessity for refinement in detail and a close adjustment of the plan selected to all the conditions at the property. In these low-cost problems any textbook division of mining systems as applied to "beds, veins or masses" avails little as a guide. It should be realized at the outset that to be successful under modern competitive conditions a system of mining must be worked out with elaborate detail, with careful time scheduling and control of the various elemental operations, and that after it is introduced it must be run with a large amount of technical direction.

Jan 1, 1934

By R. J. Mechin

IN the early part of 1934, the St. Joseph Lead Co. purchased from the Kadco Corporation three dust-removal units, two suitable for raise work, and the other for drifting operations. The equipment was installed at the Balmat mine, in St. Lawrence County, New York. The Kadco dust-control system can be briefly described as one in which hoods, through which the drill steel is drawn, control the dust at the drill hole, the dust is conveyed through rubber hose or pipe to a collector, where it is removed from the air stream, and the air is then available for recircula-tion in the working place. As during the last few years a number of studies had been completed for the purpose of determining whether or not the dust was effectively removed by the Kadco system, and as the dust counts taken in these tests apparently indicate that it was, the St. Joseph Lead Co. was only inter-ested in obtaining data to show the efficiency of drilling, expressed in terms of minutes per foot drilled, when -using Kadco equipment, in comparison with the former method of drilling dry in a raise and drilling wet in a drift. Comparative dust counts were taken at Balmat, however, by the Metropolitan Life Insurance Co. to show the difference in the dust content of the air in which the operators worked when drilling dry, wet, or with the Kadco equipment.

Jan 1, 1935

By W. H. Adams

Among the persistent experimenters of the present century no one man is more widely and favorably known in the metallurgical world than the late Peter Spence of Manchester, England, to whom we are indebted for many of the successful processes in the manufac ture of acids and alkalies, and for much of that perfection in me chanical detail which goes so far towards insuring success. For the past twenty-five years—a period covering the greatest changes in soda-processes and a revolution in acid-manufactures ef fected by the substitution of pyrites for brimstone—Mr. Spence was constantly engaged in perfecting the plant for the economical treat ment of pyritous ores; and no text-book has been complete without reference to his many inventions, patented or otherwise. The results of his labors for the past six years were not given to the public, by reason of the active competition existing among man ufacturers on the continent of Europe and in Great Britain ; but it was well known and conceded that the crowning triumph of his .life had been achieved in the successful working of his automatic desulphurizing furnace, which mechanically calcined "smalls" or finely crushed pyrites—the bugbear of all chemical manufacturers. That he was met by many delays and disappointments, and that

Jan 1, 1885

By Harold A. Linke

The following article presents notes and data compiled and computed by the writer for use in the determination of: size and slope of mill launders, details of junction boxes and downspouts, and distribution of pulp. It also includes pulp formulas, volume of discharge through bushings, paths of discharging streams, banking of turns and curves. In the design of a concentrating mill, the draftsman usually considers launders to the extent of providing ample "head" for transmission of pulp from one department of the mill to another. The superintendent of construction aims to build his launders wide and deep, and on a slope steep enough to ensure positive flow. So launders are laid generally on too steep a slope, with the result that the repair gang works to maintain launder bottoms and sides against the erosive action of the conveyed pulp. To this end many kinds of liners have been devised: concrete, mastic, white iron, glass, rubber. True, the reduction of slope to the point where a pulp will flow with minimum wear, will minimize labor and expense; but when the desired slope is not predetermined, the millman hesitates to readjust his launder slopes by cut-and-try methods. To the end that the desired size and slope may be found readily, the writer has: (1) conducted experiments with pulps of different specific gravity, screen analysis and dilution; (2) gathered a few graphic data from standard reference works (such as Peele's Mining Engineer's Handbook and Taggart's Handbook of Ore Dressing); (3) computed several tables; and compiled results that have proved dependable for Utah Copper ore. It is quite possible that the following tables and graphs may not be applicable to all ores, but it is hoped that they may prove helpful, even in slight degree, in alleviating a portion of the trouble and migraine of some other millman. Launder Slopes The main object in the study of launder slopes is to provide grade steep enough to prevent "sanding" by a safe margin, and to avoid

Jan 1, 1943

By Harold A. Linke

The following article presents notes and data compiled and computed by the writer for use in the determination of: size and slope of mill launders, details of junction boxes and downspouts, and distribution of pulp. It also includes pulp formulas, volume of discharge through bushings, paths of discharging streams, banking of turns and curves. In the design of a concentrating mill, the draftsman usually considers launders to the extent of providing ample "head" for transmission of pulp from one department of the mill to another. The superintendent of construction aims to build his launders wide and deep, and on a slope steep enough to ensure positive flow. So launders are laid generally on too steep a slope, with the result that the repair gang works to maintain launder bottoms and sides against the erosive action of the conveyed pulp. To this end many kinds of liners have been devised: concrete, mastic, white iron, glass, rubber. True, the reduction of slope to the point where a pulp will flow with minimum wear, will minimize labor and expense; but when the desired slope is not predetermined, the millman hesitates to readjust his launder slopes by cut-and-try methods. To the end that the desired size and slope may be found readily, the writer has: (1) conducted experiments with pulps of different specific gravity, screen analysis and dilution; (2) gathered a few graphic data from standard reference works (such as Peele's Mining Engineer's Handbook and Taggart's Handbook of Ore Dressing); (3) computed several tables; and compiled results that have proved dependable for Utah Copper ore. It is quite possible that the following tables and graphs may not be applicable to all ores, but it is hoped that they may prove helpful, even in slight degree, in alleviating a portion of the trouble and migraine of some other millman. Launder Slopes The main object in the study of launder slopes is to provide grade steep enough to prevent "sanding" by a safe margin, and to avoid

Jan 1, 1943