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By Philip D. Anderson, Ralph Hultgren

Heat contents of extremely pure iron were measured over the range 300"to 1433"K, using a diphenyl ether calorimeter. Results from three samples containing widely differing impurities agreed with one another and with Previously reported results at higher temperatures (1184 ° to 1809°K) by Olette and Ferrier. From these data a table of heat contents of iron has been Prepared which is believed to be more accurate than those previously available. CP values have been derived which are consistent with these heat contents, with the best experimental Cp data, and with the thermodynamic conditions of equilibrium between bcc and fcc iron. The opinion is expressed that low-temperature extrapolations of presently known Cp values for y-Fe are not reliable. It would seem that the thermodynamic properties of iron, which is by far our most important metal, should have been well established long ago. This is not the case, however. As discussed by Olette and Ferrier,' there is objection to every earlier heat content measurement. While the best true Cp determinations agree well at temperatures below the Curie point, there is wide divergence at higher temperatures. Several investigators have examined available data and attempted to calculate thermodynamic functions for iron that are consistent with the two equilibrium temperatures of bcc and fcc iron. The two primary efforts were those of Austin' in 1930 and Darken and smith3 in 1948. The recommended values differ considerably; integration of Austin's Cp values leads to a heat content at 1100°K which is 300 cal per g-atom higher than the value recommended by Darken and Smith. The compilation of Fisher4 in 1949 was based on the selection of Austin. In 1956, Weiss and Tauer obtained yet another set of values by resolving Cp values into components due to dilation, lattice vibration, electronic excitation, and magnetism. The magnitude of contribution by each component and its dependence on temperature was estimated by semiempirical means. Their values are not self-consistent in that they do not form smooth curves when plotted vs temperature; moreover, their calculations cannot easily be repeated since they do not give the values of some of the parameters used. Clearly, experimental values for iron were in a most unsatisfactory state. The presently described measurements of the heat content of iron were therefore undertaken, covering temperatures as high as 1433°K. While the work was in progress, the high-temperature (1193" to 1789"K) heat content measurements of Olette and Ferrier' were published; in the region of temperature overlap the present results agree with Olette and Ferrier well within experimental accuracy. It is believed that the present results, combined with those of Olette and Ferrier, provide for the first time a reliable set of heat contents of iron from room temperature to the melting point. From these data, guided by available Cp measurements, it proved possible to derive Cp, entropy, and free energy function values for @-iron from room temperature to the melting point, and for y- iron in the temperature region of its stability. Exhaustive study led to the conclusion that extrapolations of y-iron functions to room temperature were not reliable enough to be useful; hence these have been omitted from the tables. EXPERIMENTAL Materials. Three samples of extremely high purity iron from different sources, containing widely different impurities, were measured. The first of these, designated "Chipman", was kindly supplied by Dr. K. K. Kelley of the U. S. Bureau of Mines from a lot which was made many years ago by Dr. John Chipman of the Massachusetts Institute of Technology. The second, designated6'Teddington", was supplied by the National Physical Laboratory, Teddington, England, from a lot zone-refined by them. The third sample, designated "Irsid", was supplied by the Institute de Recherches de la

Jan 1, 1962

By S. S. Nosseir

INTRODUCTION General Quebec Cartier Mining Co. (QCM) , Canadian subsidiary of U . S. Steel Corporation, operates two iron ore concentrators at the North Shore of Quebec, Canada. In its own operation at Mount-Wright, over 45 million tons per year of crude ore are ground, fully autogenous in six 32' x 11-1/2 Dominion Engineering mills. At Fire Lake/Lac Jeannine operation, property of Sidbec Normines Incorporated (SNI), over 11 million tons per year of crude ore are now ground, fully autogenous, in twelve 18' x 5' Hardinge mills. The Lac Jeannine concentrator was originally constructed by Q.C.M. in 1960 and. was since operated, in beneficiating the Lac Jeannine ore deposit until fully depleted in 1977, at an annual capacity of 18 million tons of crude per year. In 1976, the new company, Sidbec Normines, was incorporated by Sidbec Corporation, British Steel Corporation and Quebec Cartier Mining Co., in proportional holding of approximately 51 to 41 to 8 percent respectively. Since the acquisition of the Fire Lake ore deposit and Jeannine concentrator by the new company, QCM has continued managing the mine and concentrator operaions for S idbec Normines Inc . Flow-Sheet Design Jeannine concentrator comprises twelve identical mill lines grinding the ROM from 8" top size to 14 mesh nominal size range. Driven by 600 H.P. motor at 13.4 RPM corresponding to 73% critical speed, each mill is operated in a closed circuit with two 5' x 12' vibrating screens dressed with 2.5 x 25 mm slot opening cloth. The ground product or screen undersize at an average grade of 33.4% Fe is beneficiated by gravity separation to produce 66.5% Fe concentrate grade at 42.7% weight recovery. At the rougher stage, each mill line con-tains 128 Humphrey 13- 1/2" pitch spirals which produce a final tailing, middling and concentrate products. The rougher concentrate - so produced - is classified by 64 Humphrey pocket sizers into an underflow, which is a final concentrate product and an overflow which is further upgraded by 64 cleaner spirals. The cleaner concentrate together with the pocket sizer 's underflow are dewatered on a 13'[6] horizontal filter. The rougher middling together with the cleaner tailing are recycled in a closed circuit with the spirals. The rougher tailing after dewatering by hydrocyclones is disposed of by a

Jan 1, 1982

By E. M. Wise, T. E. Kihlgren, N. B. Pilling

SYSTEMATIC data are presented on the relation of composition of nickel silvers to color, tarnish resistance, hardness and liquidus temperatures, for alloys containing up to 30 per cent nickel and 50 per cent zinc, further modified at certain nickel and zinc contents by 0 to 8 per cent of tin and 0 to 10 per cent of lead. Attention has also been directed, using a still more limited range of alloys, toward a study of tensile properties and such casting properties and characteristics as fluidity, shrinkage and pressure tightness. In some of these, rather broad ranges of composition are dealt with; in others, it has been expedient to focus attention on the Federal Specification 20 per cent nickel silver casting alloy, WWP-541.

Jan 1, 1935

The Library of the above-named Societies is open from 9 A.M. to 10 P.M. on a11 week-days, except holidays, from Sept. 1 to June 30, and from 9 A.M. to 6 P.M. during July and August. The Library contains about 55,000 volumes, including sets of technical periodicals and the publications of scientific and technical societies. Members of the Institute, with few exceptions, are forced to spend a portion of their time in localities isolated from sources of information. To these the Library can render valuable service through correspondence; letters requesting information will receive special attention. The Library is prepared to furnish references and copies of articles on mining and metallurgical subjects; to determine the existence of mining maps, and to furnish general information as to the geology and mineral resources of all countries. All communications should be made as definite as possible so that the information received may be what is desired and not include collateral matter which may not be of interest. The time spent in searching for such collateral matter will be saved, and the information will be sent more promptly and in more usable shape. The members of the Institute can be of service to the Library by for- warding copies of mining reports, maps privately issued, and similar material, which will be classified, indexed, and made available to other members. Suggestions for additions to the Library, either by purchase or personal solicitation as gifts, will be welcomed. It is hoped that members while in the city will use the Library freely, and assurance is given that most careful service will be rendered to them.

Jan 8, 1916

By H. B. Treweek, V. R. Degner

Current mineral industry trends toward handling the high tonnages of lower grade ore and tailings retreat lead to a continuing need for large volume flotation cells. The benefits which accompany the larger cell flotation circuit include reduced capital cost, less mill floor space, reduced operational complexity, and less maintenance, provided the metallurgical performance and solids suspension capability of the cell are not compromised. This study reviews development considerations pertinent to large mechanical air induction type flotation cells from the standpoint of cell internal hydrodynamic characteristics and metallurgical performance. While the importance of process related factors such as chemical usage, pH control, solids size and loading, and circuit arrangement cannot be denied, this study will emphasize the relationship of cell size (volume), mechanism geometry (impeller diameter), and mechanism operating conditions (rotor speed and submergence), to air transfer, liquid circulation, liquid "rise velocity" and mechanism power draw. Specific hydraulic performance maps for large capacity 300 and 500 cu ft flotation cells will be reviewed in terms of the relationship between the operational variables and the air and liquid flow conditions within the cell. Metallurgical results, obtained under plant operating conditions for 300 and 500 cu ft cells, are included to illustrate the metallurgical performance similarity of flotation cells which follow hydrodynamic scale-up criteria set forth in this investigation.

Jan 1, 1976

By W. S. Tower

STEEL is the basic metal, the main metallic prop of the modern industrial world, a good gage for measuring the state of our complex economy. Any who had doubts on that score should have had them dispelled by the many evidences of public concern over the affairs of the steel industry in recent months. I do not need to relate the various criticisms of the industry, nor the questions about its policies and performance which have come in a rising flood, especially from unthinking and irresponsible sources. But judged from the standpoint of production, or from plans to improve and expand facilities, or from technical progress, the facts about the steel industry are proof of

Jan 1, 1948

ROBERT PEELE, * New York, N. Y.-I should like to ask Mr. Neale how the members of the production committees at the individual mines, who came from the mine workers themselves, were chosen or appointed; also from what classes of employees they usually came? J. B. NEALE.-In the union fields, they were chosen by a local. In the non-union fields, they were chosen either by the men in mass meeting or by the company officials. The last way was very unsatisfactory because it gave the men an opportunity to say that they were going to be passed upon as to whether they were slackers or not, by men chosen by the company. When they were chosen by the locals or at mass meetings of the workers, the appointments have been very much more satisfactory. R. D. HALL, ? New York, N. Y.-The matter of inefficiency on the part of the operator is one that I think we may well take into account, because there is a very large inefficiency on the part of the coal operator; it has arisen from reasons almost beyond his control and will continue for these same reasons. It is no use arguing a moral responsibility on the part of the operator, when you make efficiency very largely a loss to the operator who puts it in force. If you ask a man working on a clay wage to work with more efficiency. he says, "Well, I may do it or I may not," it all depends how he feels, but he does not lose anything financially by not working hard. If you ask the man who is working by the ton to put out more tons, he makes a profit by putting out more tons. How is it with the operator? If he gives a man all the cars he needs and all the power he needs, if he runs after his working men and waits on them, he does not get his coal out any cheaper than before.. He gives the man a better chance and there is more efficiency, but at the same time he has increased his expenses all along the line. At the end of the year he finds that his profits have been less than if he had had less efficiency. The efficiency is really against him in many ways. Because he gets a larger tonnage, he reduces the overhead to a certain extent; but hiss tonnage may not be any greater because he may work fewer days. As Mr. Taylor remarked some tine ago, supposing he puts in a machine that is very much more effective than any he had before, he has the same scale; the miner gets out more coal, but he himself does not get any benefit out of it because he has a scale fixed, so much per ton.

Jan 4, 1919

By C. M. Wayman, J. F. Breedis

The crystallography of the martensitic transformation in the Fe-30 Ni alloy was reinvestigated. The scatter in the habit Plane as determined from measurements on the mid-rib plane was smaller than reported previously, and the orientation relationship was determined from a martensite plate having known direction cosines. From agreement with crystallographic theory and from observations of the morphnlogy of the martensite plates, it is suggested that the mid-rib plane represents the starting region of the transformation. THE crystallography of the martensitic transformation in the iron-nickel system has been the subject of many investigations.&apos;-7 However, for iron alloys containing approximately 30 wt pct Ni, a wide scatter in the reported habit planes exists. In only one instance has a Laue determination of the orientation relationship been made, but the habit plane of the martensite plate studied was not determined experimentally. Because the most successful thermodynamic and kinetic analyses8 of the martensite transformation have been based on Fe-30 Ni alloys, it was considered desirable to reinvestigate the crystallographic features of the transformation in this alloy. Lieberman9 suggested that the most significant information for use in a theoretical treatment involves the determination of all the crystallographic observables from a single plate of the product phase. This was first done in essence by Greninger and Troiano10 for Fe-22 wt pct Ni-0.8 wt pct C, and is the method followed in this investigation. Some theoretical approaches11-13 in describing the martensitic transformation consider the overall transformation distortion to be comprised of a Bain distortion, or lattice deformation (PI, which produces the structure change, and a lattice invariant deformation (G), such as twinning, which together leave the interface or habit plane un-distorted. The incorporation of a rigid body rotation (R) results in a transformation distortion (E) such that the interface plane is left both undistorted and unrotated. In matrix notation, E = RPG where the lattice invariant deformation has "taken place" in the austenite. Bowles and Mackenzie14-16 in formulating a theoretical approach proposed an adjustable scaler quantity, denoted as 6, which represents a uniform dilation in the interface plane. This dilation acts to adjust the lattice spacings of the parent and product structures at the plane of contact. Using the dilation parameter as a variable, these authors were able to account for a continuous variation of habit planes in steels along a curve in the stereogram between {225}A and {259}A. she invariant line strain14 of the transformation is 6 RP, and the corresponding transformation distortion is E/6.) With the dilation parameter known, the invariant line is computed as the triple coincidence of the habit plane, the shear plane of the lattice invariant deformation, and the initial Bain cone.14 The contraction axis for the Bain distortion can be taken9&apos;17 as [010]A, and the correct permutation of the habit plane indices used. Kelly and Nutting 18 have established the shear plane (of twinning) in the tetragonal martensite of Fe-22 Ni-0.8C to be {112)M by means of transmission electron microscopy. The reasonable shear system is then {112}M which is equivalent to {011}A <01l>A. The as-

Jan 1, 1962

By C. Y. Garber

INTEREST in the sink-float plant operated by the Bunker Hill and Sullivan Mining and Concentrating Co. at Kellogg, Idaho, has recently been largely confined to the preparation and reconditioning of the galena medium. The ease and simplicity of these operations in a concentrating mill producing a flotation lead concentrate has occasioned enough comment to possibly justify a brief description. The subject is treated from an operator&apos;s viewpoint only; no effort is made to discuss it in a theoretical or technical manner. PLANT AT BUNKER HILL The sink-float plant was first operated in December 1941. It was built for the purpose of quickly increasing mill capacity with a minimum of equipment. It is the Huntington-Heberlein sink and float process using galena medium and is operated under license from the Sink and Float Corporation, New York city. Lead-zinc ore from the Bunker Hill mine is crushed to pass a I ¼ in. screen and is then washed and separated on vibrating screens having 4 ½ -mm. round-hole punched plates. The screen undersize, amounting to 33 per cent of the mill feed, is dewatered and sent to the ball-mill feed bins. The screen oversize goes to the sink-float plant, where 50 per cent of the oversize, or 33 per cent of the mill feed, is float, which is washed free of medium and disposed of as a tailing. The remaining 33 per cent is sink, which, after washing, is crushed to pass ½ in. and joins the undersize in the ball-mill feed bins. The normal plant capacity is 1700 tons per 24 hr. About 1.7 per cent of the total lead and 3.3 per cent of the total zinc in the feed is lost with the sink-float tailings (Table I). [ ] More complete descriptions of the H. H. process and Bunker Hill sink-float plant are given in several recent articles, listed at the end of the paper. PREPARATION OF MEDIUM AT BUNKER HILL New medium is made intermittently as needed, usually 12 hr. in each 6 days. A small portion of the current mill flotation concentrate is diverted from the lead cleaner cells to a I-in. vertical sand pump and pumped to a two-cell 36-in. Agitair flotation machine, where NaCn and ZnSO4 are added and the grade of concentrate is improved as shown in Table 2. Tailing from this operation is returned by gravity

Jan 1, 1946

By Pradeep K. Rohatgi, David N. French, Surendar M. Jain, Clyde M. Adams

The effect of solute concentration and diffussivity on dendritic solidification of dilute binary aqueous solutions has been investigated; chlorides of sodium, potassium, lithiurn, and hydrogen were used as solutes. Dendrite spacings were measured in spherical droplets and in unidirectionally solidified specimens. In the droplets, the freezing rate is uniform over the entire specimen and remains constant from the beginning to the end of solidification. In the unidirec-tionally frozen specimens the freezing rate varies within a given volume of liquid during the solidification cycle; in addition, it varies with location uithin the specimen. Mass transport analysis has been used to calculate the supersaturation, AC, supercooling, AT, and transcerse growth velocity, V , of ice dendrites during solidijication from the dendrite spacings measured in the droplels. The ice dendrite spacing in a given solute increases lineary with the solule concentralion at a fixed freezing rate. The ualues of AC, AT, and V increase with an increase in solule concentration. The value of AT in the aqueous solution is of the same order of magnitude as in Al-Cu alloys of the same concentration; the dendrite spacings in Al-Cu alloys also increase with an increase in solute concentralion. For the jamily of aqueozrs solulions incestigaled, the dendrite spacing increases linearly with solute diffusivity at fixed values of concertralion and freezing ,rate. The values of ?C and ?T decrease, whereas the value of V increases with an increase in solule diffusicity. The measured dendrite spacings , L, can be expressed by the relatiun: L = K;(dfa/db) 4 K2C +K3D - K4 where dfs/d? is-change in fraction solid with time (freezing rate), C is solute concentration, D is solute diffusivit K1 = (14 * 4)pmin1&apos;2, K2 = (70 ± 10) pl (moles)- K3 = (24 r 3) . l05 psec (cm)-~. K. = -132 ± 10) 1. FREEZING of solutions is almost always an ehunmix-ing" process because the composition of crystallizing solid generally differs from that of the parent liquid. " Solute concentration and transport are therefore in]portant considerations in solidification of solutions. The influence of these factors on the dendritic solutions produced from metallic solutions is of practical significance since the properties of the solid aggre-gate are often strongly influenced by dendrite spacing.&apos;&apos;&apos; Alexander and Fthines3 found that dendrite spac- ings generally increase with solute concentration in several metallic systems. Michael and Bever1 have observed an increase in a aluminum dendrite spacings in dilute A1-Cu alloys. Rohatgi and AdamsJ have reported a linear increase in a aluminum dendrite spacings with increasing copper contents up to 28 pct in A1-Cu alloys. Bolling and Tiller"&apos; have theoretically examined the effects of solute concentration and diffusivity on the growth of cells and dendrites. Their analysis of dendritic growth assumes a steady-state growth and the maximum possible velocity for dendrite propagation. In addition, the quantitative analysis is restricted to dendrites of rotational symmetry and is therefore not directly applicable to the plate-shaped dendrites of ice obtained in the present study. There are practically no experimental observations of the effect of solute diffusivity on dendrite spacings in metallic systems. The reason appears to be the lack of experimental data on solute diffusion coefficients in liquid metallic solutions. The present work is concerned with the effect of solute concentration and diffusivity on dendritic solidification of dilute aqueous solutions: the solutes examined are potassium chloride. sodium chloride, lithium chloride. and hydrogen chloride. There were several reasons for selecting these solutes. The variation of dendrite spacing with freezing rate in these solutiolls is similar to that observed in A1-Cu alloys.8 These aqueous solutions have almost identical phase diagrams at dilute concentrations. Fig. 1. and the diffusion coefficients show very little variation with solute Concentration.9,10 Dendrite spacings were measured as a function of freezing rate. solute concentration. and solute diffusivity. Dendrite spacings were measured in two different types of freezing systems. droplet and unidirectional, respectively. In the droplet freezing system

Jan 1, 1970

By C. F. Frey, P. J. Ahern, J. F. Wallace

THE high affinity of molten titanium for oxygen and nitrogen has resulted in considerable difficulty in developing a satisfactory melting procedure. It has been found necessary to perform melting operations either in a vacuum or inert atmos-phere, and failure to obtain a satisfactory crucible material has necessitated the use of special melting techniques. These techniques have included cold-mold arc-melting utilizing both consumable and nonconsumable electrodes, skull-melting, drip-melting, and levitation melting.&apos; It has been recognized generally that the melting of both titanium sponge and titanium scrap would be expedited by the use of induction-melting procedures but the lack of a crucible capable of containing molten titanium without objectionable contamination thus far has prevented the use of induction-melting procedures. An extensive investigation: which included the common refractory materials was not successful in developing a satisfactory crucible for induction-melting. Some success in induction-melting has been attained with the use of a graphite crucible material, but in all instances sufficient carbon contamination was encountered to cause an appreciable reduction in the optimum mechanical properties of the titanium or titanium alloys. These investigations"" report an increase in the carbon content from approximately 0.3 to 1.0 pct. A serious reduction in the tensile and forming properties has been observed as a result of this carbon contamination. The development of a satisfactory induction-melting procedure for titanium without undue contamination undoubtedly would have considerable economic significance. Such a process would be particularly useful in melting the large quantities of low-cost scrap now available that can only be reprocessed at considerable expense and difficulty by the more elaborate techniques referred to previously. In addition, the process could provide a satisfactory method of melting and alloying of bri-quetted sponge for forging ingots.

Jan 1, 1959

By Howard S. Bryant

FROM the viewpoint of the oil producer, the oil refiner, the oil marketer, and the investor, in oil securities, a brief picture of the crude oil supply and demand in the present critical season of the year will be timely and interesting. Although crude oil production has been in a comparatively poor statistical position this year, increased sales and sustained refinery and crude oil prices have allowed increased profits for many oil companies. The large amount of crude oil going into storage during the present period of peak consumption, just previous to the major yearly fall decline in consumption, has caused oil producers to make plans to leave the oil in the ground for the present in several of the areas of large flush production. The present moment is looked on as the turning point in the current year.

Jan 1, 1929

By T. D. Lynch, N. B. Pilling

The development of a proper treatment for shells in conncction with war contracts has brought to our attention the fact that the temperature of the liquid bath in which steel is quenched has a decided influence on the speed of cooling in the case of some liquids and very little in the case of others. Widely different physical results have been obtained by the use of water spray, water immersion, and oil immersion and further experiment has shown that the quenching effect of water used as a spray or an immersion varies greatly with the temperature of the water. The present experiments were undertaken with the idea of obtaining information of a quantitative nature regarding the quenching properties of a number of liquids used commercially in hardening steel. The general features of such cooling media are common knowledge and in the literature may be found records of numerous attempts to evaluate the cooling power of a liquid when used as a quenching bath. Much, if not most, of the data given on this subject is in the form of a simple statement of the time required for a certain heated mass to cool between two arbitrary temperatures when immersed in the liquid, quite regardless of the path of the temperature change. Our own purpose has been somewhat different. We have attempted to isolate that property of these liquids having to do with their ability to absorb heat rapidly, as distinct from the behavior of a considerable mass when exposed to different thermal environments. More specifically, from the data obtained through autographically recorded cooling curves of a small standard mass quenched under various conditions, we have tried to analyze the mechanism of heat absorption by the several liquids, measure the changes in its rate as a function of the temperature of the surface of transference, and ascertain the influence of the temperature of the liquid itself upon both. Without attempting an exhaustive citation of the literature, mention may be made of some of the more important contributions, notably the pioneer work of Le Chatelier,&apos; followed by the extensive investigations

Jan 1, 1920

By T. L. Joseph, G. Bitsianes

The gaseous reduction of dense iron ore is a topochemical process in which reduction takes place at distinct interfaces between solid phases or layers. Under normal conditions, these interfaces remain parallel to the exterior surface of the ore body as they move inward. Certain conditions, such as cracking, high porosity, impurities, entrapped residual oxides, may cause departures from normal topochemical behavior. THE gaseous reduction of dense iron ore proceeds at interfaces between several solid phases or layers.&apos;,&apos; Under normal conditions, these interfaces progress inward and remain parallel to the exterior surface of the ore body. This topochemical behavior is clearly illustrated in Fig. 1 which shows partially reduced specimens of natural and synthetic hematite. Using a coordinated sequence of macro, micro, and X-ray examinations, the authors1-&apos;2 found that the number of interfaces and participating phases was in agreement with the Fe-0 system. Above 570°C, reduction of the ore involved a maximum of three common boundaries between four solid phases: iron, wiistite (Fe,O), magnetite (Fe,O,), and hematite (Fe,O,). Below 570°C, reduction proceeded through two interfaces between three phases: iron, magnetite (Fe,O,), and hematite (Fe,O,). The decrease in the number of phases below 570°C was due to the instability of wiistite below this temperature. The sequence of phases was also consistent with the equilibrium requirements. For example, the layers of iron oxides that were formed in topochemical fashion were always orientated in the order of increasing oxygen content. Thus, in Fig. 1 an outer layer of metallic iron is followed in turn by a thick intermediate band of black wiistite, by a thin layer of light magnetite, and finally by a relatively large core of hematite. This arrangement of the oxide layers was due to restrictions in reducing conditions which were imposed by the physical structure of the solid. The highly reducing gas on the outside of the particle gradually lost its reducing power as it penetrated into the specimen. On a macro scale, the layers of the various oxides appeared to be sharply defined and uniform in composition. Microexamination of the sections, however, revealed that the interfaces did possess measurable widths which varied with the porosity and chemical activity of the oxide phase undergoing reduction. For example, Fig. 2 shows three interfaces in a dense hematitic ore which was partially reduced at 850°C. At the iron-wiistite interface where the greatest porosity developed, the reaction proceeded over a zone 25 to 30 microns in width. Toward the interior, the interfaces became progressively narrower until at the magnetite-hematite boundary the reaction zone was about 1 micron wide. In this region the structure was exceedingly dense; the hematite possessing a porosity on the order of 3 pct. A careful micro study across polished layers of the various oxides revealed generally homogenous and single-phase structures. As reported in a previous paper,&apos; the wiistite layer was characterized by an increase in oxygen content with depth of penetration. The topochemical behavior of reduction was studied in six types of ore of different origin, composition, and physical structure. In most cases, reduction proceeded at the boundaries of well defined layers or phases, and this behavior may be regarded as normal for most dense fine grained ores. Deviations from Ideal Topochemical Behavior A number of deviations from the normal topochemical behavior were noted. In these cases, the continuity of the reduction interfaces was disrupted in one of four ways: 1—Cracking of the specimen interrupted the geometric configuration, and the interfacial advance was no longer parallel to the exterior surface. 2—As a result of high porosity, the interfaces were spread over an appreciable distance and all but obliterated. 3—Impurities in the ore promoted a variety of deviations, including cracking. 4—A residual oxide phase was entrapped in the reaction product and left behind the advancing macro interface. Results from Cracking: A crack leading into the interior of an ore specimen presents a path of least resistance for the counter-flow of reducing gases and gaseous reduction products. Higher reducing conditions can be maintained along such cracks and reduction accordingly will propagate well ahead of the normally advancing reduction interfaces. Cracking was caused by a number of factors, one of which was the thermal spalling of impurities in the massive form. A more general type of cracking was due to reduction and was found in all dense varieties of natural and synthetic hematite, particularly in the temperature range of 500" to 700°C. The effect is shown clearly in Fig. 3. In this case, a dense sphere of pure hematite was partially reduced at 650°C for 100 min. The macrosection shows that one large reduction crack had penetrated the specimen and disrupted the normal topochemical advance of the interfaces. The outer layer of iron was only slightly affected but the thin dark layer of wiistite, adjacent to the ferrite, had widened perceptibly as it progressed along the crack. Farther inward, the magnetite layer was greatly disrupted and had penetrated irregularly to form islands of unaltered white hematite. A great deal of internal cracking is evident in the magnetite phase. From a practical point of view, the cracking of dense ores in the blast furnace could lead to desirable as well as undesirable effects. The general result

Jan 1, 1956

By A. G. Paithankar, G. B. Misra

Although certain physical mechanical properties of rocks have been claimed to give an estimate of penetration rate in percussive drilling, the authors&apos; work shows that the correlation of penetration rate with individual rock properties is Poor. The authors have developed a good correlation between penetration rate and a set of rock properties but the relation is complex. Energy per unit volume has been used as a measure of penetration rate in percussive drilling by Hustrulid and Fairhurst; however, their test setup is large wing a full size drill bit. The authors determined the minimum energy for unit volume Ev min for any rock at the optimum index angle in a simple laboratory drop tester wing a sharp microbit with a tip angle of ll0°. This Ev min has been found to correlate well with penetration rate obtained in controlled laboratory drilling in different rocks for different stages of bit wear. A comprehensive relation has been developed between penetration rate and Ev min.

Jan 1, 1981

By E. S. Leaver

The authors of the paper above mentioned have sent the following statement to correct erroneous com-ments and implications in their article with the re-quest that it be published: "In the above mentioned article the reference to Bendelari jigs is used in the generic sense as applying to the mechanically driven diaphragm jigs. No attempt was made to dif-ferentiate between the various machines as installed on different dredges. The Natomas Company use a jig of their own manufacture. The Yuba Company installed the Placer jig as manufactured by the Pan American Engineer-ing Company. "The Pan American Engineering Company also manufactures the Crangle jig under their own name. This is a diaphragm jig in which the pulsations are produced by intermittent flow of water through the patent Crangle Valve and it has no driving mechanism."

Jan 1, 1937

By Frank C. Smith

The following article covers the history of a metallurgical campaign, commenced in March, 1905, at the mines of the Socorro Bold Co., in the so-called desert region of Yuma county, Arizona. The results obtained were simply a function of necessity, as will be seen from the description of the local economic conditions and the character of the ores treated. The mines and mill of the Socorro Gold Co. are located near the small village of Harrisburg, about 60 miles from Congress Junction, Ariz., which, at the time this work was undertaken, was the nearest railroad station, and from which all supplies were brought by wagon through the desert, at a cost varying from $10 to $15 per ton in addition to the railroad freights. Wood, the only available fuel, cost $7 per cord. Water for all purposes was pumped to the plant from a well in the valley about 4 miles away. Under the Arizona law, a working-shift is 8 hr. Wages were $6 per day for foremen and mill-men, $4 per day for blacksmiths and engineers, $3.50 per day for miners, and $3 per day for shovelers and trammers. The ore consisted of quartz, in which, above the 250-ft. level, the iron-minerale were largely oxidized and some free gold was visible; below that level few traces of oxidation occurred, and pyrite constituted the principal mineralizer in the quartz, together with occasional pockets of galena and a few eccentric specks of covellite. The 20-stamp mill was equipped with plates for amalgamation, and three Standard tables for concentration. The tails from the tables mere elevated by a centrifugal pump to a launder, by which they were conveyed to a 60-ton cyanide-mill for further treatment. The cyanide-mill was erected at so great a distance from the stamp-mill that a separate crew of workers and a separate power-plant were necessary. No arrangement had been made for the treatment of the concen-

Jan 1, 1907

By Yuri D. Tretyakov, Robert A. Rapp

The stoichiometry ranges ofNiOl+y and LiFe,O,-d were established by high-temperatwe electrochemical meas7rements in a stabilized-zirconia electrolyte cell. The results were consistent with doubly ionized cation vacancies in NiO,+y and interstitial lithium or iron ions in . The defect structure of the ternary ferrite was derived from the consideration of equilibration with respect to oxygen between the solid and the gas phase. The absolute magnitudes of defect concentrations were calculated. Pavtial molar enthalpies of oxygen in the compounds were calculated and interpreted in terms of the enthalpy of defect formation in these crystals. NICKEL oxide (NiO,,?) is a metal-deficient, p-type, extrinsic semiconductor whose properties are consistent with a structural model based on the presence of cation vacancies as the predominant ionic defect at sufficiently high temperatures and oxygen activities. A survey of previously reported conductivity studies and the presentation of some more recent conductivity measurements will be given in a later paper.&apos; The absolute magnitude of the equilibrium vacancy concentration in NiO has been reported from combined conductivity and thermogravimetric data of &apos; However, disagreement exists concerning the state of ionization of the nickel vacancies in NiO. Some authors3-&apos; have proposed that the predominant defects in NiO are singly ionized nickel vacancies and positive holes (h&apos;) formed by the reaction where, accorhng to the notation of Kroger and Vink,6&apos;7 Oq represents an oxygen ion on its normal lattice site. Other authors"27E have proposed that doubly ionized nickel vacancies (V{i ) and positive holes are predominant and are formed by the reaction One purpose of the present investigation was to establish the nature of the predominant defect in NiO,+? as well as its equilibrium concentration and thermo-dynamic properties at elevated temperatures and known oxygen activities. To accomplish this purpose, the coulometric titration of oxygen into and out of NiO was accomplished using a galvanic cell involving the calcia-stabilized zirconia electrolyte. The ternary oxide, lithium ferrite (LiFe50,-6) is ferromagnetic and has the inverse spinel structure LiFe,O,-d Thus, in the ideal stoichiometric XY204 lattice, Fe3 ions occupy one-eighth of the tetrahedral (A) sites, and i&apos; and Fe3&apos; ions share at random one-half of the octahedral (B) sites within the fcc sublattice of oxygen ions.g The structure and thermodynamics of the spinel structures have been comprehensively decribed.&apos;-&apos; A recent compilation of literature for lithium ferrite is also available. 15 Oxygen-excess LiFe50sis not expected to exist because both i&apos; and 17e3& ions are in their highest normal valency states (positive hole formation is not favorable). As will be discussed, equilibration of the ferrite crystal with oxygen of a surrounding gaseous phase will result in the introduction of equilibrium concentrations of ionic and electronic defects. In the Results and Discussion section a defect model for LiFe50,-d is proposed. This defect model is tested by high-temperature coulometric titration experiments. EXPERIMENT The oxygen activities in nonstoichiometric NiOl+, (and also LiFe,O,-d) were measured by means of coulometric titration with the high-temperature galvanic cell The critical characteristic of a suitable experimental cell is the complete isolation of the phase to be investigated in a minimum sized chamber which is free from extraneous sources and sinks for oxygen (leakage). Then oxygen is only admitted to the chamber or removed from it in known amounts by coulometric titration, which involves the passage of oxygen ions through the solid electrolyte with electrochemical oxidation and reduction reactions at the platinum contacts to the electrolyte. The experimental cell is shown in Fig. 1. The cap of the cell was the tip from a closed-end alumina tube, which was found to be leak-free from a helium leak-detector test. This alumina cap was about 1.2 cm OD and about 1.5 cm high. A Zircoa calcia-stabilized zirconia tablet (crucible lid) of 1.5 cm diam and 0.3 cm thickness served as the solid electrolyte. A Pyrex ring of about 0.1 cm thickness was placed between the electrolyte and the cap. The electrolyte tablet was painted with platinum paste on the entire outer face and on that part of the inner face which would be within the enclosure; these electrodes were further prepared by heating in air at 1000°C for 2 hr. Nickel oxide powder, listed as 99.999 pct pure, was purchased from Leico Industries, Inc. Pills of the NiO were cold-pressed and sintered at 1050°C for 3 hr in a platinum crucible. This poorly sintered NiO was crushed, and chunks were wrapped in 52-mesh Pt gauze (to catalyze the solid-gas exchange) for place-

Jan 1, 1970

By Carl S. Westerberg

Coal preparation practice and trends follow, among other factors, production trends in any given area. Considering an area the size of a state, some broad predictions may be made after a review of the annual production records. As this paper is concerned with coal cleaning in Utah, data on its production record are pertinent. Table 1 shows the percentage relation of coal production in Utah to the national total as a single figure up to 1935 which includes all recorded production. From 1935 through 1947 these data are presented by years. It is evident from these data that the production of Utah coal is ascending. The reason for this trend is industrial growth in the West resulting in a population shift which accounts for more people than the normal increase would supply together with Utah&apos;s relatively fortunate geographical location and its abundance of good-quality coal. Utah is also hopeful of supplying more coal in the future for West Coast power generati0n.l

Jan 1, 1949

By O. P. Dolph

SPANIARDS were probably the first to mine the rich surface ore in the veins cutting the rhyolite capping that outcrops on the hills of La Mazata, oil the Allyones side of the Magdalena valley in Jalisco, Mexico, although the name comes from a word of Indian origin meaning "deer". The camp is about 12 km. west of Magdalena, a town on the Southern Pacific Railroad, and about 17 km. north of Etzatlán, on the Mexican National Railroad, at an elevation of 4500 ft. The climate is subtropical with no extremes of heat or cold, the rainy season beginning in June and ending in October.

Jan 1, 1938