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The co-operation of the members of the Institute is earnestly sought by the Committee on Nominations, recently appointed by the Board of . Directors, in its work of formulating a ticket for officers and places falling vacant in the Board of Directors in February, 1916. The Committee must present the official ticket of nominations to the Board of Directors at its October meeting. Members are, therefore, urged to send promptly their nominations for officers and Directors in order that the Committee may have an opportunity to give them full consideration. The officers to be elected at the annual meeting in February, 1916, are: One officer, known as Director and President. Two officers, known as Director and Vice-President. Five officers, known as Director; The attention of members is called to Articles V and VII of the Constitution, and to By-Law XIII, which reads as follows: "The geographical districts to be considered by the Committee on Nominations shall he as follows, until otherwise ordered by the Board. District No. 1. New England, New York, and New Jersey, excepting New York City and district., which is provided for in the Constitution. (N. B.-New York City and district is designated District 0.) District No. 2. Pennsylvania. District No. 3. Ohio, Indiana, Illinois, Iowa, and Missouri. District No. 4. Minnesota, Wisconsin, and Michigan. District No. 5. Montana, North and South Dakota, Wyoming, Nebraska, Kansas, Washington, Oregon, Idaho, and Alaska. District No. 6. California and Nevada. District No. 7. Utah, Colorado, Arizona, and New Mexico. District No. 8. Louisiana and Texas. District No. 9. Other Southern States and District of Columbia. District No. 10. Mexico. District No. 11. Canada."

Jan 7, 1915

By J. W. Ristori

During the year 1940, production of crude oil in RiIexico totaled 43,914,000 bbl., or 2,776,000 less than in 1937, the year before expropriation. The 1940 output was I,2000,000 higher than in the previous year. In 1937, Poza Rica production accounted Declines in exports of Panuco crude, fuel oil and gasoline were recorded but these were more than offset by increased exports of 4,000,000 bbl. of Poza Rica crude, which was the approximate amount shipped to Sinclair during 1940 under the terms of the settlement. Over-all exports increased by 1,500,000 bbl. over the preceding year. The outstanding development regarding the destination of Mexican exports in 1940 was the increase of I0,000,000 bbl. in the exports to the United States. Exports to Germany ceased toward the end of '939 and to Italy in the second half of 1940. During the year 1940 the Sinclair interests and the Mexican Government settled their expropriation question. By the terms of the settlement Sinclair is to be compensated by cash payments and oil-purchase contracts. On Dec. I, 1940, Ada Camacho was inaugurated President of Mexico for a term of six years. Among his first acts following his election were: I. A proposal to change the Constitution to restore Supreme Court Judges' terms to life tenure. This has been ratified by both chambers of the Mexican congress and is now before the legislatures of the States of Mexico for ratification. The, taking away of the administration of the railroads from labor and restoration to the State.

Jan 1, 1941

An abstract of a paper from the Canadian Mining and Metallurgical Bulletin of August 1978 by E. Stamboliadis, J. McHardy, T. M. Salman, Department of Mining and Metallurgical Engineering, McGill University, Montreal, Quebec, states that: “The recovery of gold, silver and other heavy metal cyanides from mill solutions is technically possible using the ion exchange technique. However, the costs involved are greater than the costs of the zinc precipitation technique used for gold recovery. There are two main reasons for this: one, the fact that in gold ore cyanidation metal cyanides other than gold and silver occupy most of the resin capacity and hence reduce the adsorption efficiency of the resin for the Au and Ag cyanides; secondly, the high cost of the eluting agents.” Resin, therefore, cannot in most cases be efficiently used for recovery of precious metals. With copper in solution, only 1.47% of the resin capacity is used for gold and 0. 8970 for silver; the rest is occupied by unwanted metal cyanides, such as copper occupying 73.7%. On the other hand, although activated carbon will adsorb copper cyanides, they will be preferentially displaced by gold and silver cyanides. Ion exchange is by one or two orders of magnitude more expensive than the conventional method of zinc precipitation. The cost of removing impurities, such as copper from the resin, is greater than the cost of recovering gold. With an oxide ore amenable to cyanidation and with a low content of other metals, such as may occur with some of the Soviet gold deposits, ion exchange would be an efficient as Carbon-In-Pulp.

Jan 1, 1981

By J. W. Ristori

During the year 1940, production of crude oil in RiIexico totaled 43,914,000 bbl., or 2,776,000 less than in 1937, the year before expropriation. The 1940 output was I,2000,000 higher than in the previous year. In 1937, Poza Rica production accounted Declines in exports of Panuco crude, fuel oil and gasoline were recorded but these were more than offset by increased exports of 4,000,000 bbl. of Poza Rica crude, which was the approximate amount shipped to Sinclair during 1940 under the terms of the settlement. Over-all exports increased by 1,500,000 bbl. over the preceding year. The outstanding development regarding the destination of Mexican exports in 1940 was the increase of I0,000,000 bbl. in the exports to the United States. Exports to Germany ceased toward the end of '939 and to Italy in the second half of 1940. During the year 1940 the Sinclair interests and the Mexican Government settled their expropriation question. By the terms of the settlement Sinclair is to be compensated by cash payments and oil-purchase contracts. On Dec. I, 1940, Ada Camacho was inaugurated President of Mexico for a term of six years. Among his first acts following his election were: I. A proposal to change the Constitution to restore Supreme Court Judges' terms to life tenure. This has been ratified by both chambers of the Mexican congress and is now before the legislatures of the States of Mexico for ratification. The, taking away of the administration of the railroads from labor and restoration to the State.

Jan 1, 1941

By Robert H. Weber

INCREASING acceptance of perlite products, chiefly in the fields of lightweight structural aggregates and thermal and acoustic insulation, has led to expanding market demands that have encouraged many new producers to enter the field. In some instances, however, the failure of these producers to anticipate the variable response of perlite to conventional processing methods has led to difficulty in establishing an economical flowsheet by which a predictable specification product could be obtained. It is not the writer's intent to provide a solution to these problems, but rather to summarize their nature. It is to be hoped that members of the industry who have hurdled some of these obstacles will document solutions arising from their experience. In this treatment the term perlite will not be restricted to the petrographic definition but will apply to all volcanic glasses. Expansible obsidians and pitchstones are accordingly included in this broader industrial classification. Chemical Properties: Although perlite has been reported to range in composition from that of rhyolite to that of andesite, it is probable that most of the glasses have the composition of rhyolite. When recalculated to an anhydrous basis, the five analyzed glasses from New Mexico, representing five distinct physical types from widely separated deposits, show an amazingly uniform oxide composition. Water content is the only major compositional variable; total water ranges from a low of 0.37 pct (non-expansible obsidian) to a high of 8.95 pct (expansible pitchstone). The wide range in expansion characteristics exhibited by these samples cannot be related to significant variations in the composition of the nonvolatile fraction and has been only partially correlated with variations in water content.

Jan 1, 1956

By A. L. Titchener, M. B. Bever

FROM their investigation of the martensitic transformation in Cu-Zn alloys, Greninger and Mooradian' concluded that there was no critical temperature at which martensite formation began in this system. Recent unpublished work by Gen-evray With two compositions of brass revealed the existence of a critical temperature, which is a function of composition and stress. In the work reported here the temperature range of the martensitic reaction was studied as a function of composition in high purity Cu-Zn alloys. The specimens were about 4 in. long with a diameter of 1/16 in.; their compositions are given in Table I. They were heated under vacuum for 5 min at 5" to 10°C below the temperature of incipient melting, and quenched into brine at about — 10°C. Specimens of alloys C, D, E and F were obtained with little or no precipitated a phase. Many attempts yielded only three usable specimens of alloy B, and even these contained appreciable amounts of a. All efforts failed to preserve metastable p in alloy A (containing 38.02 pct Zn and 0.002 pct each of Pb and Fe). The transformation was studied by measuring the electrical resistance during continuous cooling and heating of each specimen at similar rates. The cooling media were alcohol with dry ice from room temperature to — 78°C and a bath of petroleum ether and methyl cyclohexane (75:25), cooled by liquid nitrogen, from —78" to about —150°C. Readings were also taken at —195 °C in liquid nitrogen. Fig. 1 illustrates a typical experiment. The relative resistance is obtained by assuming the known

Jan 1, 1955

By Max W. Ball

Our ever-increasing use of minerals has been the outstanding fact in our American economic development. The rise in our standard of living in the past century is without equal in human history. Nowhere in time or place has the man who works lived so well, or the man who cannot work been so well cared for. We live in a new world, even the poorest of us, that our forebears of 1849 could not have dreamed. That new world has come mainly from our use of minerals. Our per capita use of nonmineral products has grown too, but by only a modest amount. Food consumption per person has grown about 15 per cent in the past fifty years; lumber use per person ,has fallen 56 per cent and that of wood for fuel 65 per cent. Of all the products of field and forest, our use, per capita, may have increased by one fifth during the present century. In contrast, our per capita use of minerals has multiplied several times. Each of us uses 2% times as much steel and 16% times as much petroleum as our fathers used in 1900. In less than half a century our per capita consumption of all minerals has probably risen by 200 to 250 'per cent. Man once built with wood; today he builds mainly with brick and stone and steel. Once he traveled by the power of hay and oats; today he travels by the power of coal and oil. Rubber made from minerals is already better for some uses than rubber tapped from trees; before long it will be better for most and perhaps all uses. Even our ladies' graceful legs are clad in mineral fiber, where once animal or vegetable fiber would have covered them. Our high standard of living is a product of the machine.. The machine is made of minerals. The machine is driven by minerals. The machine age is a mineral age.

Jan 1, 1949

By Allan D. Taylor

INTRODUCTION From the designer's view, the installation starts with the first definition of the orebody, and progresses through a long and complex development. The design is affected not only by the characteristics of the ore, but by all of the personalities and events of the project during its development. The following discussion attempts to touch on the most important aspects which define the context in which the designer must work in apply the do's and don'ts. That context is the basis of the viewpoint. WHAT CAN GO WRONG The Project Is Going Over Budget This is a common and serious concern to the plant designer. The Project Falls Behind Schedule Another common and disturbing condition with which the plant designer must cope. Some Equipment Fails to Perform This can be due to either faulty equipment or operating deficiencies. It can be the result of a wide variety of causes, but the designer will be an interested party in the search for the cause and the cure. The Plant Isn't Flexible Enough Sometimes a plant will handle some or even most of the ore satisfactorily but is unable to treat another type properly. This can be a significant problem. An example might be a case where low capacity of a cyclone feed pump makes it impossible to accompany an increase in grinding mill throughput with a corresponding increase in dilution water. This could lead to an increase in cyclone feed density, and a loss in product grade or a limit on the plant capacity. Spillage And Cleanup Are Excessive This is one of the most common and annoying defects in metallurgical plants, and one for which the designer can rarely delegate blame. Maintenance Is Excessive Another common complaint in new plants, and also one for which the dedesigner must accept most of the responsibility.

Jan 1, 1982

By Thomas T. Read

AT this time of the year, engineering schools are releasing a group of young men who probably are, on the average, in much the same attitude of mind as a person arriving at the terminal station of a railway journey; namely, of having a general idea of his objective, but having to make a decision as to just where he is going and how best to get there. The man leaving the train can at first follow the crowd, but it soon breaks up, as one goes one way and one another, until he has to choose his own course. The recent graduate may do the equivalent of following the crowd by accepting the first position offered, but this only postpones a decision as to where he is going and how best to get there. So many young engineers ask for advice as to what to do that the following statement has been prepared as an attempt to make a general answer to such queries. The engineer taking his first job should realize two fundamental relations. The first is that in electing to be an engineer he has elected to be a hired man. A consulting engineer has more freedom than a man on a regular pay roll, but he is also a hired man; hired for briefer periods at a relatively high rate, but under the necessity of simultaneously doing his consulting work and developing new retainers. There is nothing derogatory in being a hired man (all doctors, lawyers and clergymen are hired men), but the tardy realization that he is one seems to give many an engineer a mental jolt that can be avoided if he accepts it from the beginning.

Jan 1, 1926

By Thomas L. Kesler

I all of the 14 million tons of kaolin produced in Georgia through 1949 had been mined from a single deposit 20 ft thick, it would represent a mined-out area of less than 1 sq mile. This measure of depletion is in such strong contrast with the large size of the area shown in Fig. 1, from which most of the output has come, that there has developed an optimistic outlook concerning future supplies of kaolin equal in grade to that already mined. Dozens of mines are widely but not evenly distributed within this area, which consists mostly of parts of Twiggs, Wilkinson, and Washington counties. There are scarcely half a dozen kaolin mines elsewhere in the state that have been appreciably productive, although the areas in which they occur may have good possibilities. Most of the efforts to find new deposits, therefore, will be confined to the area shown in Fig. 1, for it is here that the industry has established its facilities, and prospecting is encouraged by relatively numerous outcrops and opened deposits of kaolin. The Ocmulgee and Oconee rivers drain the area. They and their main tributaries have flat, swampy floodplains covered with alluvium and for the most part thickly wooded. The divides between these streams are intricately dissected by the minor tributaries, which are spring-fed in steep-walled, cirque-like heads. Gullying and under-cutting are active along the streams but are partly controlled by unusually dense vegetation. The mean altitude is about 350 ft above sea level, and locally the relief ranges up to 200 ft. The area is near the inner margin of the Coastal Plain, and is underlain by Cretaceous and Tertiary formations. Its general location is shown in black in Fig. 1. The division between the Coastal Plain and the Piedmont plateau is actually a very sinuous line, the fall line, marking the extent to which erosion has stripped the Coastal Plain sediments from the southeastward-sloping surface of the crystalline rocks of the Piedmont. Cretaceous Host Formation The kaolin deposits, which are described in the succeeding section, occur sporadically in lenslike bodies in a thick series of poorly sorted clayey sands constituting the lowermost of the Upper Cretaceous formations, the Tuscaloosa. The basis for this correlation has been reviewed by Cooke.1 The same formation has been termed the Potomac group by Ladd2 and the Middendorf formation by Smith' in reports on the kaolin deposits. In another report, Veatch4 called the formation the Tuscaloosa but correlated it with the Lower Cretaceous. The Tuscaloosa in this area consists of fine to very coarse sands, commonly cross-bedded, which contain widely different proportions of white, pink, and yellow kaolin and considerable white mica. A few of the coarser beds contain quartz grains up to 3 in. in length, with bodies of pure white kaolin of equal size that appear to have been formed by the weathering of feldspar grains in place. In the kaolin-producing area, gravel and cobbles occur mainly at the base of the formation. Fig. 2 shows the relations of the Tuscaloosa and its kaolin deposits to the adjacent formations. Its base, on the eroded surface of the crystalline rocks, dips southeastward 50 to 60 ft to the mile, according to LaMoreaux.5 The upper surface of the Tuscaloosa is also an unconformity,

Jan 1, 1952

By C. R. Wohrman

A melt of pure electrolytic iron with about 0.4 per cent. sulfur and 7 per cent. manganese was prepared in connection with a study of inclusions in iron. The alloy darkened rapidly when etched with a 10 per cent, alcoholic solution of nitric acid, and microscopic examination revealed the presence of a semimartensitic, semi-Widmanstättian structure (Figs. 1 and 2) closely resembling the structures found by Benedicks in his artificially prepared "meteoric iron."' The structures found by Benedicks were readily explained by the presence in his alloy of the two well-known iron-nickel solid solutions, taenite and kamacite, and of their eutectoid (?) aggregate, plessite. By analogy, one would infer the existence of similar phases in the iron-manganese alloy just described, such an inference being strengthened by the similarity displayed in many ways by nickel and manganese in their effects on iron. Iron-manganese Alloys are Regarded as Homogeneous Heterogeneity of iron-manganese alloys has not been recognized heretofore, judging from the data of standard metallographic books and those of original papers. In fact, iron and manganese are quite generally regarded as completely miscible in the solid state. Dr. Rosenhain,2 for example, writes: Alloys of group (a), of which those of gold-silver, iron-manganese, and copper-nickel are examples, when allowed to crystallize sufficiently slowly to attain their condition of final equilibrium, present a microstructure exactly similar to that of a pure metal—the homogeneous character of the molten solution is in that case so completely maintained that the microscope cannot detect the presence of any second constituent. Guillet and Portevin3 refer to the iron-manganese system as an example of the "case of metals completely miscible in the solid state."

By H. B. Pulsifer

.ABOut 1.5 varieties, or tnodifications, of the best rnagnesiurn available were prepared and subjected to etching tests, then examined for micro-structure. Of the 30-udd etching reagents that were tried, nearly half, mostly ammonium salts, etched the metal satisfactorily. The surfacing and etching of magnesium is shown to be a very simple and quick operation. The density and hardness of magnesium were determined. The most interesting new observations relate to the finding of the hexagonal etch figures, the crystal laminations, and the fact that the metal is plastic, cold, when restrained or quickly deformed. Under slowly applied pressule cold metal deforms slightly, then shears to fracture without plastic flow. The chief structural features of magnesium arc presented in two reduced photographs and 30 photomicrographs. Materials Tested There are only two sources in the United States from which new metal can be procured: the American Magnesium Corpn. and the Dow Chemical Co. No pronounced structural or property differences in the metals from these two companies were disclosed by the work of this investigation. The following materials were obtained from the manufacturers: 1. Massive crystals of distilled metal (American Magnesium Corpn.). 2. Rods of hot-extruded metal, ½-in. squares and 5/8-in. rounds (American Magnesium Corpn.). 3. Sheet magnesium, 0.005-in. thick (American Magnesium Corpn.). 4. Cast stick metal, 13/8-in. dia. (Dow Chemical Co.). 5. Magnesium-aluminum alloy, hot-rolled plate, ½-in. thick (American Magnesium Corpn.). From these materials, were prepared: 6. Sections from a furnace-cooled ingot made from clistilled crystal. 7. Cold-strained pieces from (6), (4) and (2). 8. Pieces cold-squeezed to fracture from (6), (4) and (2). 9. Hammer-struck pieces from (6), (4) and (2). 10. Steam-hammer struck pieces from (6), (4) and (2). 11. Sections from furnace-cooled ingot of the magnesium-aluminum alloy.

By Robert H. Richards

The extent to which sizing by sieves should be carried, as a preliminary to the separation, by jigging, of minerals of different specific gravities, has been a matter of controversy for many years. The subject has been investigated by several authorities, yet the ground does not seem to have been completely covered, nor are the questions involved entirely settled. For my present purpose I shall refer to but three investigators—Rittinger, Munroe, and Hoppe. In seeking additional light, I have gone over part of the old ground which has been considered satisfactorily settled; and since these preliminary tests have thrown light on some points, they have been included in this paper. In the investigations here described, I have confined myself, for several reasons, wholly to small sizes—grains of 0.1 inch in diameter and less. Rittinger's work was mainly done upon larger sizes, and there is much need among millmen of information concerning the smaller sizes. Moreover, these sizes brought the investigation within the means at my disposal. The laws that have been claimed as the laws of jigging by the several authorities are: 1. The law of equal-settling particles. 2. The lam of interstitial currents. 3. The law of acceleration. 4. The law of suction. The first of these has been considered by investigators, generally, to be the most important of all, and the larger part of the work of jigging is thought to be governed by it. But that it does not cover the whole of jigging is clear to all; and to account for the increased efficiency which we may call the extra jigging-catch, the other three laws have been advanced. The investigation described in this paper was undertaken to determine, as far as possible, to what extent each of the four laws con-

Jan 1, 1895

By Edmund S. Davenport

The production of thorium of high purity by the Ca-CaCl2 reduction has been described by Marden and Rentschler,1 who also reported some of the properties of the coherent, ductile metal obtained from this pure thorium powder. The present paper describes the properties of thorium produced by the Ca-CaCl2 process modified in some details to meet commercial conditions. The principal effect of these changes in process has been an unavoidable increase in the oxide content of the thorium. Materials and Methods The thorium employed in this investigation was made from pure thorium oxide (ThO2) by the Ca-CaCl2 reduction. The washed and dried metal powder was pressed into bars approximately 0.160 in. dia. and 10 in. long, at a pressure of 75,000 Ib. per sq. in. The bars were heat-treated in vacuum at 1175' C. for 1 hr. This treatment yielded ingots sufficiently dense and coherent for mechanical working. Thorium has been successfully worked without a protective metallic covering, but for the purposes of this investigation it was more convenient to inclose the ingots in soft iron tubes and swage or roll cold to the desired sizes. The iron sheath was dissolved with nitric acid, leaving the cold-worked thorium exposed. Chemical Analyses Analyses of typical samples of the material used in this work arc given in Table 1. Thorium powder oxidizes in moist air, even at room temperature; no unusual precautions were taken to prevent such oxidation of the material used in this investigation. A certain amount of oxidation probably takes place during pressing; certainly during heat-treating unless a very slow heating schedule is employed. These factors account

Jan 1, 1930

THE problem of reaction rates in the open-hearth process is essentially that of trying to form a fairly clear picture of the "chemical mechanisms" in the bath. Quantitative data on reaction rates would not be very useful even if they were available; however, what few , approximate data there are, can be used in combination with data given in Chapters XVI and XVII to sketch a picture of the "chemical mechanics" of the open-hearth process that is consistent with essentially all the present available evidence. The result may later be found incorrect in many details but even so it will illustrate certain useful methods for obtaining a clearer understanding of the process. As discussed in the last portion of Chapter XIII chemical reactions in general involve the following factors: 1. The reacting molecules are mixed together in space in such fashion as to favor collisions among them. 2. A certain number of collisions occur per unit time among the reagent molecules, depending on their concentration and on temperature. 3. A certain percentage of these collisions result in reaction, these being the collisions between those molecules possessing at the moment energy levels above certain minimum values. The temperature factor enters mainly through (3), and its effect is very marked. (What is called temperature is really the mean energy content of all the molecules of the substance involved; at any one temperature a certain proportion of the molecules will have much higher energy content than the mean value.) Various reaction rates measured at around room temperatures have been found to be speeded from 1.6 to 4.0 times by an increase of only 15 to 20°F., simply because increasing temperature produces a rapidly increasing percentage of molecules with energy levels above the minimum needed to produce chemical reaction in a collision.

Jan 1, 1944

By J. Chipman, T. P. Floridis

The equilibrium of gaseous H2O-H2, mixtures with liquid iron is used to establish the activity coefficient of dissolved oxygen as log f o = — 0.20 [%O]. Discrepancies in earlier work are explained or eliminated. Additions of cobalt, molybdenum, tungsten, and platinum increase the activity coefficient of oxygen whereas copper and gold decrease it. THE importance of dissolved oxygen as a refining agent in liquid steel has led to a number of studies of its thermodynamic properties. It is the purpose of this paper to examine the effects of a number of alloying elements on the activity of oxygen in the steel bath. As a preliminary to the study of the effects of alloying elements, it seemed desirable to examine certain minor discrepancies in the published data on the properties of oxygen in simple iron-oxygen solutions. The activity and free energy of oxygen in liquid iron were studied by chipman1 in 1933 by means of the reaction h2(g)+-o = H2O (g);K; = PH2O/PH2[% O] [1] The data were in fairly good agreement with calculations from results on the similar reaction CO (g) + O- = CO2 (g); K2 =P CO2/P CO [% O] [2] which had been obtained by Vacher and Hamilton2 as an incidental part of their study of the reaction of carbon with oxygen dissolved in the melt. It was found that the equilibrium ratio k1 was not a true constant but varied with the oxygen concentration in the manner shown in Fig. 1, which is copied from the original paper. This early observation has been refuted in subsequent work but is confirmed in the present paper, and an explanation of the discrepancy can now be presented. In Fig. 1, the two points on the extreme right were disregarded in drawing the

Jan 1, 1959

By Richard D. Harvey, Arthur M. Squires, Robert A. Graff, George Kan

Particles of half-calcined dolomite (CaC03 + MgO) that had undergone cyclic absorption of H2S and regeneration with C02 in laboratory tests reveal enlargement of the crystallite grain structure, reduction in the number of pores but enlargement in their size, and partial development of a relatively dense mosaic microstructure on outer surfaces of cyclically reacted particles. Scanning electron microscopy, X-ray microanalysis, microprobe analysis, and X-ray diffraction techniques were used to evaluate microstructural properties of particles after tests conducted at pressures of 1 and 21 atm and temperatures of 7000 to 9000 C. The tests conducted at 7500 C and 21 atm showed the most favorable absorption and regeneration capacities of the dolomite tested. The changes in structure and pores play a major role in reducing the sulfur reactivity of half-calcined dolomite particles. The mosaic microstructure forms more rapidly at 1 atm than at 21 atm pressure. Once it occurs it seals the surface of the natural pore channels that existed in the half-calcined dolomite and restricts further conversion of crystallites of CaCO3 within the particles. Although a relatively coarse, granular mosaic of crystallites is present on some particles cycled at 21 atm pressure after only three absorption-regeneration cycles, it does not completely cover the particles, and that is true even after 30 cycles. Individual crystallites of MgO were not resolved by the X-ray microanalysis, but we believe that during the tests the MgO occurs as crystallites no more than 0.1 um in diameter that are homogeneously distributed through the particles, and it remains essentially inert during the reactions. The MgO contributes to the maintenance of the original fine-grained and microporous structure of the particles, an effect that is most advantageous to absorption and regeneration.

Jan 1, 1976

By Carl R. Davis, J. L. Willey, S. E. T. Ewing

The first tube-mill on the Rand was put into operation in May. 1904, at the Glen Deep Mine. From that time onwards, tube-mills were added to various plants, although little was known regarding the capacity of a given tube-mill when working on banket ore. Within a few years, however, the so-called standard size (length of shell, 22 ft. 0 in.; diameter, 5 ft. 6 in.) was generally used until the last year or two. Practically the only exceptions were about 30 tube-mills having a length of 16 ft. and a diameter of 6 ft., and a few open-end mills of the roller-supported type. Most of the information obtained during the last 15 years has been obtained with mills of the standard dimensions. The adoption of the tube-mill as an accessory to the stamp mill was rapid; and where 3 tube-mills were working on the Rand at the end of 1904, 244 were in use seven years later.' By 1910, good practice provided 1 tube-mill for 20 stamps of 2000-lb. falling weight. The horsepower of the motors driving the tube-mills had increased from 80 to 100 and then to 125 at this date. Broadly speaking, current practice at that date aimed at a ha1 product of which 60 per cent. was suitable for sand treatment and 40 per cent. for slime. The sand grading was +60 mesh, 6 per cent.; +90 mesh, 25 per cent.; — 90 mesh, 69 per cent.; and the slime grading +200 mesh, 2 per cent.; —200 mesh, 98 per cent. It was recognized comparatively early that the tonnage of — 90-mesh product produced by a tube-mill per 24 hr. was a convenient measure of

Jan 1, 1925

By Claus G. Goetzel

PRESSING of powdered metal parts is best done in the direction of the shortest extension of the piece, to avoid too great a loss of pressing force through internal [ ] friction. As long as curved surfaces, recesses, or offsets occur only parallel to this shortest axis of pressure, no special difficulties arise: the cross sections, perpendicular to the pressure, do not vary, nor does the shape of the parts change during compression except for a gradually reduced thickness (Fig. IA). The problem becomes more difficult, however, when the curved surfaces or recesses are perpendicular to the shortest axis of the part (Fig. IB). Two processes for molding uniformly dense parts with complicated shapes from powdered metals are described in detail in this paper. Both can be employed successfully by those trained in the art. The first refers to curved parts; the second is especially adapted to parts having one or more recesses or steps. Both methods, as set forth here, are applied under the condition that presents the more difficult problem. For clarity, before description of the two practical methods, the variable factors in molding powdered metal parts will be reviewed, then an idealized procedure will be considered briefly. VARIABLE FACTORS IN MOLDING POWDERED METAL PARTS Compression Ratio Compression ratio is defined as the proportion of the final relative density of the compact to the apparent density of the powder. For iron powder of an apparent density of 3.0, for example, a compression ratio of 2 1/2 : I would be required to produce a compressed compact of 7.5 density; whereas for another iron powder having an apparent density of only I.5, a compression ratio of 5:I would be required to produce the same density. The lower the powder's apparent density, the greater must be the compression ratio for pressing compacts of high density.

Jan 1, 1945

By Oscar Marzke

STUDIES on the precipitation of a face-centered from a body-centered structure-a common occurrence in alloy systems-are essential to the development of a theory for the formation of segregate structures. The separation of the alpha phase from the beta of the copper-zinc system is an example of this type of precipitation. EARLIER STUDIES ON THE SUBJECT R. F. Mehl and 0. T. Marzke1 in 1931 presented a paper giving the results of some investigations carried out by them on the segregate structures produced when the alpha and gamma phases of the copper-zinc system and the alpha phase of the copper-aluminum system precipi-tate from the beta phases of these systems. They showed that the alpha phase precipitates as needles close to the [111] directions of the beta phase. In the discussion of that paper some doubt was expressed about the nature of the segregate. More investigations were undertaken to determine the character of the precipitate in the copper-zinc system and also the orientation relationship between the matrix and precipitate. The present paper gives the results of these investigations. Since the publication of the earlier paper, several other papers on this subject have been published in this country and abroad. Haneman and Schroder2 reported that the alpha phase precipitates as needles along the [111] directions of the beta phase and that these needles align themselves to form plates on the {111} planes of the matrix. Mathewson and Smith3 pointed out that the {111} plane does not contain the [111] direction and that it would be quite impossible, therefore, for needles in the [111] direction to form plates on the {111} plane. They suggested

Jan 1, 1933