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By Fred C. Bond

MOST investigators are aware of the present unsatisfactory investigatorsstate of information concerning the fundamentals of crushing and grinding. Considerable scattered empirical data exist, which andare useful for predicting machine performance and give acceptable accuracy when the installations and materials compared are quite similar. However, there is no widely accepted unifying principle or theory that can explain satisfactorily the actual energy input necessary canexplain commercial installations, or can greatly extend the range of empirical comparisons. Two mutually contradictory theories have long existed in the literature, the Rittinger and Kick. They were derived from different viewpoints and logically lead to different results. The Rittinger theory is the older and more widely accepted.'TheRittinger In its first form, as stated by P. R. Ritted.'tinger, it postulates that the useful work done in crushing and grinding is directly proportional to the new surface area produced and hence inversely proportional to the product diameter. In its second form it has been amplified and enlarged to include the concept of surface energy; in this form it was precisely stated by A. M. Gaudin' as follows: "The efficiency of a comminution operation is the ratio of the surface energy produced to the kinetic energy expended." According to the theory in its second form, measurements of the surface areas of the feed and product and determinations of the surface energy per unit of new surface area produced give the useful work accomplished. Computations using the best values of surface energy obtainable indicate that perhaps 99 pct of the work input in crushing and grinding is wasted. However, no method of comminution has yet been devised which results in a reasonably high mechanical efficiency under this definition. Laboratory tests have been reported- hat support the theory in its first form by indicating that the new surface produced in different grinds is proportional to the work input. However, most of these tests employ an unnatural feed consisting either of screened particles of one sieve size or a scalped feed which has had the fines removed. In these cases the proportion of work done on the finer product particles is greatly increased and distorted beyond that to be expected with a normal feed containing the natural fines. Tests on pure crystallized quartz are likely to be misleading, since it does not follow the regular breakage pattern of most materials but is regularrelativelybreakage harder to grind patternat the finer sizes, as will be shown later. This theory appears to be indefensible mathematically, since work is the product of force multiplied by distance, and the distance factor (particle deformation before breakage) is ignored. The Kick theory4 is based primarily upon the stress-strain diagram of cubes under compression, or the deformation factor. It states that the work required is proportional to the reduction in volume of the particles concerned. Where F represents the diameter of the feed particles and P is the diameter of the product particles, the reduction ratio Rr is F/P, and according to Kick the work input required for reduction to different sizes is proportional to log Rr /log 2." The Kick theory is mathematically more tenable than the Rittinger when cubes under compression are considered, but it obviously fails to assign a sufficient proportion of the total work in reduction to the production of fine particles. According to the Rittinger theory as demonstrated by the theoretical breakage of cubes the new surface produced, and consequently the useful work input, is proportional to Rr-l.V f a given reduction takes place in two or more stages, the overall reduction ratio is the product of the Rr values for each stage, and the sum of the work accomplished in all stages is proportional to the sum of each Rr-1 value multiplied by the relative surface area before each reduction stage. It appears that neither the Rittinger theory, which is concerned only with surface, nor the Kick theory, which is concerned only with volume, can be completely correct. Crushing and grinding are concerned both with surface and volume; the absorption of evenly applied stresses is proportional to the volume concerned, but breakage starts with a crack tip, usually on the surface, and the concentration of stresses on the surface motivates the formation of the crack tips. The evaluation of grinding results in terms of surface tons per kw-hr, based upon screen analysis, involves an assumption of the surface area of the subsieve product, which may cause important errors. The evaluation in terms of kw-hr per net ton of —200 mesh produced often leads to erroneous results when grinds of appreciably different fineness are compared, since the amount of —200 mesh material produced varies with the size distribution characteristics of the feed. This paper is concerned primarily with the development, proof, and application of a new Third Theory, which should eliminate the objections to the two old theories and serve as a practical unifying principle for comminution in all size ranges. Both of the old theories have been remarkably barren of practical results when applied to actual crushing and grinding installations. The need for a new satisfactory theory is more acute than those not directly concerned with crushing and grinding calculations can realize. In developing a new theory it is first necessary to re-examine critically the assumptions underlying

Jan 1, 1953

By Robert A. Kinzie

PAGE Introduction.............334 Climate.............335 History............335 Geology.............341 Mining..............343 Shafts............343 Stations and Ore-Bins....345 Levels. Drifts. Cross-Cuts, Winzes. etc........347 Stoping Surface-Pits,......... 351 Underground Stoping........... 332 Chutes. Drilling. etc.....354 Tramming............. 358 Sampling. Maps and Assaying.........360 Labor.............361 Machinery.............362 Milling,..............362 Crushers.............366 Battery-Foundations...........368 Power (Water—Coal)...........373 Methods of Catching the Free Gold...374 Screens..............376 Apron-Plates,.......376 Concentration..........378 Clean-Up,.............378 Labor..............382 Costs..............382 Introduction. The Treadwell Group comprises five mines. four of which are situated on the northeast side of Douglas island. directly opposite the town of Juneau, and one about four miles back of Juneau. These mines are owned by four separate companies. but are all under the same general management. Those situated on Douglas island are : The Treadwell mine. owned by the Alaska Treadwell Gold Mining Co.. the Mexican mine. owned by the Alaska Mexican Gold Mining Co.; and the Ready Bullion and Seven-Hundred-Foot mines. owned by the Alaska United Gold Mining Co. The Juneau mine. owned by the

Jan 1, 1904

By E. S. Machlin

The possibility that formation of voids under creep-rupture conditions may take place by the condensation of vacancies has been investigated theoretically. It has been concluded that nucleation of voids under creep-rupture conditions by vacancy condensation is highly improbable. However, growth of pre-existant voids by vacancy condensation is probable. A number of predictions made in this theory have been verified by the data. It has been predicted and checked that the product of rupture life and steady-state creep rate for preannealed metals and single phase alloys is an approximately invariant quantity, independent of stress, temperature, and atomic number for a given type structure. The direction of the effect of cold work on this product has been predicted and found in agreement with experiment. A number of experiments to evaluate the vacancy condensation mechanism further are described. SEVERAL papers have appeared recently which speculate on the origin of voids formed at grain boundaries under stress.' ' The object of this paper is to examine quantitatively the proposition that the voids produced in a creep test are a result of vacancy condensation. A result of this paper is a theory of creep-rupture. Void Nucleation Application of standard nucleation theory" to the problem of void nucleation leads to the following conclusions: 1—Homogeneous nucleation of voids requires a supersaturation ratio (concentration of vacancies in supersaturated to that in saturated solution) of 400 for a reasonable surface energy of 1000 erg per cm-and 1.4 for the improbably low surface energy of 10 erg per cm. 2—Heterogeneous nucleation of voids at plane interfaces between two phases requires a supersaturation ratio of 2.5 for a typical contact angle of 145 3-—Void nucleation about a solid particle may be accomplished at a supersaturation ratio of 1.17 for a typical value of work of adhesion? of 60 erg per The work of adhesion is the surface work 10 replace two solid-vauor surfaces by a solid-solid interface. enr ' between an oxide and a metal in the presence of a surface active element such as sulphur. Estimates of the supersaturation ratio at which voids are produced in diffusion experiments yield a maximum of 1.01. Inasmuch as the foregoing mechanisms of void nucleation probably will not operate at this level—too low a surface energy is required—the investigatol. is led to the conclusion that voids must already exist. That is, nucleation of voids probably does not occur. Rather, existing submicroscopic voids grow out to visible size. Already existing voids might be produced during solidification or working. Supercritical sized parlicles which contain cracks may act as heterogeneous void nuclei. Gas pockets may act as void nuclei. Experiments are desired to determine the nature of the heterogeneous void nuclei which grow out to voids in both diffusion and creep experiments. Void Growth Void growth might occur in at least two possible ways, depending upon whether the already existing void nuclei are at grain boundaries or within the grains. In the case of a spherical void far from a crystal boundary, vacancies are generated during creep as a consequence of the migration of suitable dislocation jogs' and are also annihilated at sinks. Under these conditions, a steady-state concentration of vacancies is built up in the crystal, defined by the condition that for any differential volume the rate of generation of vacancies in that volume equals the rate of annihilation of those vacancies." This equality would lead to the development of a gradient of vacancy concentration radially outward from the void surface up to a radius where the vacancy lifetime becomes equal for all directions of vacancy migration. The distance over which this vacancy concentration gradient extends equals about 2vD,T* where D, is the vacancy diffusivity and T:' the vacancy lifetime in a crystal outside the gradient in a zone of constant vacancy concentration. The vacancies generated in the region over which the gradient exists will annihilate more often at the void than elsewhere. Approximately a little over one-half the vacancies generated in the gradient zone will annihilate at the void. Hence, the growth rate of the void is given by on where R is the radius of void in centimeters, is the atomic volume, and R is the rate of generation of vacancies, number per centimeter" per second. R D and T* may be estimated in terms of other physical parameters." In particular, R = n.j e/b [3] where n is the average number of vacancy produc-

Jan 1, 1957

By George Hallerman, R. J. Gray

In the customary method of studying age hardening, the process of aging is interrupted by cooling the specimen and measuring its room-temperature hardness. However, the aging process may be conveniently measured while it is occurring at an elevated temperature by a series of hardness measurements at suitable time intervals. The latter method gives data void of complications that might result from processes occurring during the quench, and the data may be more indicative of the alloy's properties at elevated temperatures. The elevated-temperature hardness tester1 used in the present study employed a dead-weight loading system with a synthetic sapphire Vickers-type in-denter mounted in a molybdenum holder. The tests were performed in a vacuum of l0 to 10 torr. Hardness impressions were made by applying a 2-kg load for 15 sec. Although the hardness impressions made in the tester at elevated temperatures were measured at room temperature, the correction for thermal contraction during cooling was insignificant and therefore neglected. The two methods of obtaining age-hardening data were compared using eighteen samples of Haynes alloy No. 25* which had been annealed for 2 hr at 2250°F (1232°C). The test surfaces of the 1 by 1 by 1/4-in. samples were ground and then polished on vibratory polishers2 prior to testing. Three groups of five samples were aged at 1400°, 1650°, and 1800°F (760°, 899", and 982°C) for 4, 16, 32, 64, and 100 hr and then water-quenched. Room-temperature hardness as a function of aging time for these samples is shown in the broken lines of Fig. 1. Only one sample for each of the three temperatures was necessary to determine the hardness of the alloy at the aging temperatures with the elevated hardness tester. The specimens were heated isothermally and hardness impressions were made after various time intervals up to 100 hr. The results of these determinations were represented by solid lines in Fig. 1. Comparison of the two sets of curves shows, as expected, the hardness values determined at the aging temperatures are lower than the room-temperature hardness of the quenched specimens and the hot-hardness values reflect a strong tempera-

Jan 1, 1964

By Hsun Hu

Based on Kurdjumoiv-Sachs orientation relationship for the fee bee transformation in metals, the jirzal crystal orientation resulting from successive transformations of bee-fee-bee has been analyzed mathematically. There are 528 different variants; many of ther are crystallograpyically equirvalent. Specific examples show that, for equal probability of all the variants, the principal crystallographic axes [100 ], [110], and [111] of the initial bcc crystal can be transformed into vairous axes in the fina1 crystal However, fur each of these principal crystallographic axes, a continuous range of orientation within certain regions of the unit triangle is completely avoided by the finctl Crystals. For uses of higher indices, the final orientations are more uniformly distributed throughout the unit triangle. Results from the PI-esent analysis are in good agreement with preferred Oientations Observed in a zone-meltecl iron bar. THE allotropic forms of iron are characterized by the unusual fact that at both high and low temperatures a bcc structure is stable, whereas at intermediate temperatures (1400" to 910°C) the metal is fcc. Hence, during cooling from its melting temperature, iron undergoes successive phase transformations ofd—? —a with corresponding changes in the crystal structure of bcc — fcc -bcc. while numerous studies have been made in the past of the 1 — a transformation in iron and in various iron-base alloys, no information is available in the literature as to the mechanism of 6 — l transformation and the lattice orientation relationship between these two phases. Experimental difficulties have apparently prevented researchers from undertaking these studies. The laltice orientation relationship between the parent and the new phases of iron resulting from

Jan 1, 1965

By Edgar M. Dunn

Part I. Determination oF Gases in Smelter Flues. General considerations. Regular methods for carbon monoxide, oxygen, nitrogen, moisture. Sulphur oxides-—Methods of Lunge and Hempel tried, and either modified or discarded, with reasons therefor. Gravimetric method developed at Anaconda. Description of apparatus used. Brief notes on Richter and Hawley methods for the direct cietermination of sulphur trioxide. Carbon dioxide, with complete notes on same. Arsenic trioxide. Table of percentages of flue gas constituents found at a Western smelter. Some final notations as to the value of flue gas analysis, in connection with an intelligent log of furnace operations. Part II. Notes on the Determination oF Dust Losses at the Washoe Reduction Works, Anaconda, Mont. Discussion of problem, with description of flue system. Various places and methods for determinations of velocity. Instruments used. Procedure in making determinations for velocity. Soundings of cross-section for depths of dust. Calculation of velocities and areas. Daily volume of gas, and plant operations during tests. Place for dust determinations. Apparatus and methods of 'sampling. Results obtained, with table of daily amount of dust losses. Analysis of dusts for values, from various sampling stations. Complete analysis of composite sample of stack emanation. Last analysis totaled to show form in which present. Discussion of recovery as a commercial proposition. References on Pitot tube and calculations.

Jan 1, 1914

By E. H. Bunce, E. C. Handwerk

The inherent difficulties of zinc smelting arise from the fact that metallic zinc is volatilized at the reducing temperature of zinc oxide and thus is liberated in the form of a vapor. This vapor must be subsequently condensed to obtain metallic zinc, first in molten and eventually in solid form. Zinc vapor is sensitive to oxidation not only by air but by combustion gases containing carbon dioxide. It is, therefore, necessary to carry out both the reduction and the condensation operations in a closed system consisting of an externally heated muffle with attached condenser from which extcrnal oxidizing agencies are excluded. However, the reoxidation of zinc vapor cannot be entirely prevented by excluding external sources of oxidation. Internal sources of oxidation are necessarily present when oxidic zinc ores are reduced by a carbonaceous reducing agent. The reduction reactions themselves involve, first, the production of carbon monoxide in an amount at least equal in volume to the zinc vapor produced in the reaction, and, second, the formation of carbon dioxide. Not all of the carbon dioxide is reduced again to carbon monoxide by the excess carbon in the time available, and the slightly oxidizing condition, which results, seriously affects the efficiency of the condensation of the zinc vapor to the metallic state. In the past the difficulties arising from these causes have limited practical zinc smelting on an industrial scale to the use of small retorts equipped with small condensers. The retorts had to be small, because a closed refractory container capable of excluding oxidizing gases from the heating chamber surrounding the retort could not be built in large dimensions. The size was also limited because ordinary refractories when thin enough to conduct heat readily are not capable of sustaining a heavy load of charge at high temperature. Moreover, a loose charge of zinc ore and carbonaceous reducing material such as fine anthracite coal or coke breeze is a poor conductor of heat, thus limiting the cross section of the retort. The operation of these small retorts requires arduous

Jan 1, 1937

By C. Feng, I. R. Kramer

A study was conducted to determine the influence of the surface on the yield point of fcc metals and high-purity iron. For the high-purity fcc metals, the yield Point produced by restraining a specimen may be eliminated by removing a sufficient amount of the layer. A yield point similar to that in fcc metals was found when iron specimens were pre-strained after a prior deformation. This yield point is not due to an aging effect but is associated with the surface layer. The yield points in age-hardenable aluminum alloy and those connected with "work softening" are not affected by a surface-removal treatment and are, therefore, caused by bulk-type dislocation reactions. The yield point which appears in previously strained fcc metals has been the subject of numerous studies. Several theories have been advanced to explain this "unloading-reloading" yield point. Cottrell and stokes,' from their study on the effect of temperature on plastic properties of high-purity aluminum, considered that it was the result of an avalanche "breakdown" of Lomer-Cottrell sessile dislocations. Haasen and Kelly2 extended this concept of dislocation-dislocation interaction to account for the yield point when unloading and reloading was carried out at the same temperature. On the other hand, strain aging was found to be responsible for the yield point in A1-Mg alloy by Westwood and Broom,3 and in aluminum alloys containing various amounts of alloying elements by Smallman, Williamson, and Ardley.4 In these cases, the yield point is considered to be associated with the locking of dislocations by impurity atoms. Birn-baum and filer5,6 and Takamura and muira7 reported that, when a high-purity copper specimen was prestrained, then held at a lower stress, and finally reloaded at the prestrain temperature, a larger yield point was observed. Such an increase was attributed to the locking of dislocations by point defects. In addition, Bolling8 suggested that both mechanisms, i.e., dislocation-dislocation interaction and strain aging, are responsible for the yield phenomenon, at least in a brass. Thus, there appears to be experimental evidence for both the strain aging and dislocation-dislocation interaction theories to explain the yield point in the fcc metals and alloys. In a previous article,9 one of the authors observed that, if sufficient amounts of metal were electrolti-cally removed after deformation of a high-purity aluminum single crystal, the yield point did not appear upon reloading. Continued pursuit in this area revealed that the effect of the surface on the yield-point phenomenon is not limited to one metal but affects a variety of metals of different lattice structures. Nor is the effect limited to the yield points produced by simple unloading-reloading at constant temperature; the surface exerts an important role on the yield point even when the temperature is changed at some stage during the test. It is the intent of the present article to give additional information regarding the effect of the surface on the yield-point phenomenon and to show the association between the yield point in both fcc and bcc metals and the existence of a heavy concentration of dislocation in the region near the surface of a deformed specimen.10 EXPERIMENTAL Materials. The single crystals used in this study had a nominal cross section of 0.125 by 0.125 in. and a 3-in. gage length and were prepared by a modified Bridgman technique. The initial purity for the metals was 99.997, 99.999, and 99.999 pct for aluminum, copper, and gold, respectively. Bar stock of these same materials was used in the preparation of the polycrystalline specimens of aluminum and copper. The iron specimens were machined from rods of "ferrovac", reported to have a purity of 99.98 pct. In addition, a precipitation-hardening aluminum alloy, containing 1.5 pct Cu, 2.5 pct Mg, and 5.5 pct Zn, was used. The polycrystalline specimens of iron, copper, and the aluminum alloy had a diameter of 0.17 in. and a gage length of 2 in. while the high-purity aluminum specimen had a nominal rec-

Jan 1, 1965

By Robert W. Hunt

HAVING devoted considerable time to the investigation of the Clapp-Griffiths converter and the metal produced in it, it may perhaps be of interest to the Institute to learn the conclusions which I have formed. Of course, it is well known that the stationary converter of small size is the very oldest type of vessel used in the pneumatic process. Hence it will be only necessary to call your attention to the points which are special features of the Clapp-Griffiths. This converter has a slag tap-hole, situated at such a height in relation to the metal under treatment that, when the cinder is formed and boils up as the blow progresses, it can run off and thus be removed from contact with the iron, and will also be out of the way when the decarbonized metal is tapped into the casting ladle and the manganiferous alloy added. The manner of shutting off the blast, when the process is completed and the metal is being tapped, is another distinctive feature. The tuyeres are situated around the sides of the vessel, and enter the interior some little distance above the bottom; they are provided with plugs through the centers of which there are small openings. When the blow is completed, these plugs are forced forward into the outer orifices of the tuyeres, thus shutting off the blast, excepting the small quantity' entering through the passages named. While this is sufficient to keep the metal from running into the tuyeres, it reduces to the minimum the action of the blast while the metal is being tapped. Of course, this is of great importance, as in an ordinary stationary converter any delay in getting open the tap-hole means overblowing, and even while the first part of the charge is running out the oxidation is in frill force. Duplicate or movable bottoms are used, thus more than doubling the possible output of the plant. The pressure of' blast is quite light, never ex-

Jan 1, 1885

By Henry M. Howe

Preparing the Metals.—Ordinary silver wire was hard-drawn to No. 23 Brown and Sharp gauge; it was cut in two, and one piece was carefully annealed in the ordinary way. The wire was prepared by Messrs. Guild and Delano, jewelers, Boston. The Ansonia Brass and Copper Co., Ansonia, Conn., kindly furnished me with some hard-drawn copper wire No. 31, A. W. G., and some of the same wire after annealing in the ordinary way.

Jan 1, 1885

By J. R. Stone, G. D. Storm

Design features and operating methods of ASARCO's new unit for the continuous melting and casting of tough pitch copper at Perth Amboy are described. Preliminary studies made for determinitzg economic feasibility and design details are also presented. Cathodes are preheated with oil and melted in an electric furnace at 40-ton per hr rate, from whence the molten copper is fed simultaneously to the wire bar casting wheel and the continuous casting of cakes and billets. In the early 1950's the copper refining furnaces at ASARCO's Perth Amboy plant reached a point where major expenditures would have to be made for replacement of the furnaces and the auxiliary equipment. The problem was whether to continue with the standard reverberatory furnaces or to consider continuous melting in electric furnaces. Reverberatory furnaces have been used for years in the copper industry and for some 50 years at the Perth Amboy plant. Reverberatory melting practice, however, imposes certain restrictions. First, labor costs are high, usually requiring three shifts per day. Secondly, they operate on a batch basis, the conventional operation being a 24-hr cycle including

Jan 1, 1961

By T. Sterry Hunt

Jan 1, 1891

By AIME AIME

THE Institute of Metals held a well rounded out symposium on the working of metals, distributed over two sessions. At the first session* four papers were presented, two dealing with the, cold working of metals and alloys and two with the hot working of non-ferrous alloys. The first paper by E. V. Crane, dealt with "Metal Working in Power Presses." Mr. Crane pointed out the empirical nature of engineering data available for use in calculating the probable stresses developed and power requirements, for the shearing, drawing, binding and other forming operations. He described the various operations, methods of determining stresses developed and presented data obtained. In the discussion C. F. Hammond took exception to Mr. Crane's objections to the rather too frequent. annealing operations in drawing of cartridge cases, pointing out that the material was-manufactured to meet specified structure and physical requirements, which could only be met by carefully controlled sequences of working and intermediate annealing operations.

Jan 1, 1931

By A. C. Boyle

PaGE I. Introduction.........68 II. Location of the District,....... • 70 .. III. Stratigraphy...........73 Description of the Rocks.......73 Triassic Eruptives (Andesite Flows and Tuffs) ....73 Triassic Sediments (Shales and Slates)..75 Areal Geology ............75 Structure...-.......76 Folds............. 76 Faults..........79 Shear ...........80 Intrusives..........81 Alaskite Dike.........81 Andesitic Intrusion.......82 IV. PetrogRaphy of thE Rock Types......83 Andesite Flows.........84 Tuff 8...........84 Andesite Tuff........84 Rhyolite Tuff.....-.......85 Alaskite-Porphyry.......89 Andesite Dike........91 V. Description of the Mines......92 VI. Metalliferous Deposits ........ 95 Character of the Ores...........97 Mineralogy of the Ores.......97 Metallic Minerals.......97 Microscopic Character of the Ores...98 Secondary Enrichment....... 103 Genesis of the Ores ...........104 VII. The Sulphate Deposits.......109 Gypsum ..... HO Anhydrite......... ,... 110 Barite............ 110 Origin. with special reference to Gypsum....111 VIII. Summary.............. 113 IX. BIblYogRaphY.............114

Jan 1, 1915

ALABAMA Anniston.-Bretz, J A Carnngton, F G Gerber, A B Ashland -Barton J Sturdevant, J C Bessemer -Abbott, C E Ball, T L Ferguson, V Salmon, H S Schaber, C F Thompson, N E Whatley, W J Birmingham.-Adams, J H -Aldrich, T H Aldrich, T H , Jr ALASKA Anchorage -Dyer, B W. Parker, H C Smith, S S Chichagof.-Baumann, H N , Jr Copper River.-Douglass, W C Cordova.-Hazelet, G C Fairbanks -Davis, J A Hyder -Pitt, D L Juneau -Jackson, G. T Murphy, R E R..11 ti At i

Jan 1, 1923

By E. L. Jr. Spain

THE deposits described in this paper occur over much of Wayne County and in the southeast portion of Hardin County, Tennessee, and in the northeast and northwest portions of Mississippi and Alabama respec-tively. The presence of tripoli in this region has been known for some time and descriptions of various occurrences in Tennessee have been made by Jewell1 and Miser2, while Hilgard3, Lowe4 and Logan5 have treated the deposits that occur in the adjacent portions of Alabama and Mississippi, but there has not been a general survey of the entire field summarizing completely the geology of the deposits with respect to their origin and stratigraphic relationships. During 1934, while engaged in surveys of mineral resources through this region for the Tennessee Valley Authority, the writer collected data with this in mind, and has assembled them in this report. He is indebted to H. S. Rankin and N. A. Rose, of the Tennessee Valley Authority Geology Division, for field assistance.

Jan 1, 1936

By Arthur A. Center

WAR demand- motivated developments in the zinc industry during 1942. Stocks of Prime Western were built up and High-Grade remained tight. The Prince The Prime Western stocks are expected to be cut down and the demand for High-Grade more easily filled as the Depue reflux plant of the New Jersery Zinc Co. increases - production. Subistition of steel for brass in artillery shell cases will have a considerable effect on the zinc situation of the country one estimate of the saving in zinc in 1943 by this substitution being a little under 100,000 ton, of metal. The metal saved will, of course be High-Grade. If the substitution occurs, the present tight situation in High-Grade may be entirely relieved as new production comes on the market and zinc may find itself approaching a situation as comfortable as that of lead provided the supply of zinc-hearing raw materials is sufficient to keep all reduction plants tip to capacity production. The premium price of the per pound of zinc over set quotas which went into effect early in 1942, helped to bring about the new lead-slag-fuming plant and other new sources of raw materials.

Jan 1, 1943

By George A. Miller

ALTHOUGH the Andean mountain belt, which contains almost all the metal deposits of the other South American nations, does not enter Brazil, this country is rich in mineral resources, for in area it accounts for half the continent and geologically it contains almost all of the Brazilian Shield. This great mass of ancient rocks has been relatively stable for a long time and forms a great area of plateaus and highlands interrupted only by the syncline which carries the Amazon River across it to the sea. Lowland Brazil - the great flood plains of the Amazon. Tocantins, Paraguay, and Parana Rivers-is of no interest to the miner, and in fact supports but a small proportion of the country's population. The highland area is divided into unequal parts by the Amazon River; the north half is underlain by the north lobe of the Brazilian Shield which extends into Venezuela as far as the Orinoco, and into the Guianas, and is known as the Guiana Highlands. Mineralization appears to have been weak in the Brazilian portion of these hills. In fact most of the ore deposits are to be found in the States of Minas Gerais and Bahia, although the neighboring states of Sao Paulo, Pernambuco, and Piauhy can also boast of some deposits. Goias and Matto Grosso are as yet incompletely prospected but are considered to contain reserves for the future.

Jan 1, 1945

By W. E. Horst

Flotation feed was hell constant for batch laboratory tests and continuous pilot and commercial plant tests on a spodumene ore to determine the relation.ship between flotation behavior and the size and type of flotation machine. Results. showed that additional retention time would be needed in the plant flotation circuit to duplicate laboratory or pilot plant performance when operating Dariables of the. plant flotation machines remained unchanged. During the past few years of operation at Kings Mountain, N. C., full-scale flotation has generally yielded poorer metallurgical results than those obtained in the laboratory or pilot plant. After 2 min in each size of Denver flotation machine in the spodumene rougher circuit, pilot recovery (41.7 pct) was almost three times that of the plant (13.6 pct) and about twice that of the laboratory (21.0 pct). Pilot and commercial plant data are based on continuous operation, and laboratory results on batch testing of rougher performance. The ore is a pegmatite containing spodumene, feldspar, quartz, mica, and amphibolite. Data were accumulated to evaluate the scale-up relationships between laboratory, pilot plant, and plant flotation cells. Flotation rate constants and dimensional analysis were used to define the relationship existing between flotation behavior and scale of operation. Measuring Flotation Rates: Efficiency of the rougher stage was measured by flotation rate, defined as the recovery that can be attained within a given time." • The problem of measuring flotation rates has been studied by many investigators, whose methods have varied. Published studies an flotation kinetics have been summarized recently by Gaudin.l When comparing flotation rates, it is more satisfactory to compare straight line relationships between recovery and flotation time than exponential curves resulting from plotting cumulative recovery vs cumulative flotation time. To convert the exponential curves into straight line relationships, rate equations were applied similar to those used in chemical kinetics to study the velocity of chemical reactions. Two rate equations have been used in this investigation to measure efficiency of the various cells: 1.5 order Rate Equation dR/dt=k (A-R)1.0 [Eq.1] Second Order Rate Equation dR ---- - K(A - R)2 [Eq. 2] dt Upon integration Eq. 1 becomes 1/(A-R)1/2=k/2 t+1/A1/2 [Eq. 3] and Eq 2 becomes: or fEq. 4] t/R=1/A2K+t/A [Eq. 4] where R = cumulative recovery [percent recovery of total value (spodumene) in flotation feed]. A = initial concentration, pct (100 pct of mineral to be separated). t = flotation time (minutes). k = flotation rate constant for 1.5 order rate equation [units: 1/(percent) 0.5 (min)1. K = flotation rate constant for second order rate equation [units: 1/(percent) (min) 1.

Jan 1, 1959

By P. E. Demmler

PHOSPHORUS combines with copper in various proportions, forming true alloys, some of which are of commercial importance. These materials find wide application as deoxidizers and as a means of introducing phosphorus into other alloys, as in phosphor-bronze. Phosphor-coppers containing 10 and 15 per cent. of phosphorus are the commercial grades that are most generally offered. Each has certain advantages when used in making other alloys. The 10 per cent. grade of phosphor-copper has an advantage over the 15 per cent. in that it has a much lower melting point and can be prepared by certain methods with a much lower loss in phosphorus. The 15 per cent. grade has the advantage of lower freight rates per unit of phosphorus and, by the method to be described, a uniform product can be prepared with practically no loss of phosphorus. Alloys of copper and phosphorus containing any desired percentage of phosphorus lower than 15 per cent. can be prepared by melting together the requisite amounts of copper and 15 per cent. phosphor-copper. Processes for making phosphor-copper may be divided into two classes as follows: (1) Those depending on the smelting of phosphate rock or superphosphate of calcium with copper or copper-bearing materials, and coal or other carbonaceous material; (2) those depending on the direct combination of metallic copper and elemental phosphorus. A number of formulas for preparing phosphor-copper according to the first method have been published. The Metal, Industry' gives-the following: Superphosphate of calcium, 60 lb.; granulated copper, 301b.; finely powdered coal, 10 lb. Similar formulas are given by Brannt2 and others, and detail 'variations are covered by patents, such as those of L A Jeffs3 and H A Webster.4

Jan 8, 1920