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By L. C. McCabe

THE object of the present investigation was to discover a physical basis for rank differentiation of coals, particularly the coals of the Illinois basin. Vitrain1 was selected as the most appropriate coal material to use in the investigation, because of its homogeneity and ease of acquisition and handling. Previous Investigations.-Hoffman and Jenker2 have shown that their index of reflection is a characteristic of coal rank and that the Leitz slit microphotometer may he used in determining the different intensities of reflection. Zhemchuzhnikov3 measured the luster of several Russian coals with a color analyzer and found that the degree of luster was indic-ative of rank. Luster-volatile matter curves based on data from Sucan and Donetz coals were satisfactorily used for determining the rank or volatile content of other coals after the luster strength was determined. In 1934 Fisher4 reported refractive indices of 1.76 for bituminous vitrain and 1.87 for semibituminous vitrain. Investigation of Angle of Polarization.-Early in the present investiga-tion several determinations of the refractive indices of the vitrains were made by immersing the minus 150 plus 200-mesh powder in oils. It was found that all the samples fell within the range 1.6 to 1.8. However, difficulty was encountered in securing oils in this high index range that were closely enough spaced to separate some of the coals. The writers made a number of determinations of the angle of maxi-mum polarization from the polished surfaces of the vitrains and derived their refractive indices by the procedure described in the follow-ing paragraphs.

Jan 1, 1937

By A. M. Gaudin, D. W. Fuerstenau

IN concentration of certain ores by soap flotation, prevention of quartz flotation is desired; the contrary is true in treatment of some oxide iron ores. Experimental study of the flotation of quartz goes back at least a quarter of a century.' Clean quartz does not float with fatty acids or soaps but does float when activated by one of many metallic salts. Control of pH is important. Broadly speaking the problem of quartz flotation has been approached from the empirical side, as was the related topic of flocculation or dispersion of quartz suspensions? Empirical studies indicated the existence of critical relationships between the additions of collector and activator. These additions were not stoichiometric for the formation of soaps of the activator cation. For example, Gaudin and Rizo-Patrona found optimum quartz flotation at pH 10.6 using barium activation and oleate collection when the molar ratio of oleate to barium was 1 to 1 instead of 2 to 1, as would be called for formation of Ba(OL),. Cooke and Digre" ' found that if calcium is the activator, a minimum quantity of that agent is required for effective flotation when the pH is 11.5. In other words, if the concentration of Na' exceeds 10 -2.5 mols per liter or if the concentration of H exceeds 10-11 mols per liter, the concentration of Ca++ in solution required for quartz activation is increased. This suggests that H+ is much more effective than Na+ on 10-2.5 quartz, perhaps in the ratio ofp or 108. Schuh- mann and Prakash6 studied anew the activation of quartz by barium, calcium, aluminum, and ferric iron. Salts of these metals are activators provided they are in stoichiometric excess over the collector used with them. Alkaline-earth salts are effective only in alkaline circuits. Important as they are in giving data on the effect of various agents on quartz, all these studies fail to give information on the detailed structure of the quartz-solution interface. A beginning in this direction was made by Gaudin and Chang,? who measured the adsorption of radioactively marked barium and laurate ions at quartz surfaces, and by Gaudin. Spedden, and Laxen,8 ho measured the adsorption of radioactively marked sodium at quartz surfaces. Work has also been done by Bell0 n measurement of the adsorption of sodium ion and chloride ion at quartz-solution interfaces. In all these experimental measurements of adsorption, the solid was centrifuged or filtered from the bulk of the liquor with which it had been associated; and the composition of the solid surface was ascertained by analysis, after allowance was made for the ionic composition of the liquor included with the centrifuged solids on the assumption that it is identical to the bulk liquid. Adsorption measurements give only the total amount of collector adsorbed at the quartz-solution interface; they give no indication of the distribution of these adsorbed ions at the interfacial layer. It is the ionic structure of the solid-solution interface and its importance to flotation that is the subject of this paper. The structure of this interfacial layer can be investigated by means of electrokinetic methods so that by combining electrokinetic studies with adsorption measurements, a more complete picture of the quartz surface may be obtained. The following studies were made to ascertain how electrolytes used in the soap flotation

Jan 1, 1956

By Walter Miller

ALTHOUGH confident of its ability to meet any demands which may be made, the petroleum refining industry is not complacent about the situation and realizes that the quantities of petroleum products to be furnished are so enormous and so far beyond what was previously estimated that the full co-operative effort of the industry must be exerted. Establishment by the President in May of the Office of Petroleum Coordinator for Defense with Secretary of the Interior Ickes at its head, plus the formation of the Petroleum Industry Council for Defense, in November, provide the channels for united endeavor within the industry and the means for gearing that endeavor within the industry and the means for gearing that endeavor in full harmony with the nation?s needs. Great strides have been made and a rapid understanding of the situation and the magnitude of the task is being attained by all concerned.

Jan 1, 1942

By Louis A. Carapella, Ralph Hultgren

WHEN F. Heusler1 found in 1898 that certain alloys containing only copper, manganese, and tin were ferromagnetic, the discovery excited a great deal of interest and led to numerous investigations. It was early found that tin could be replaced by aluminum, arsenic, antimony, bismuth, or boron without destroying the ferromagnetic nature of the alloys.2 Copper may also be replaced by silver.3 All these alloys have come to be known as "Heusler alloys." The aluminum alloys apparently were the most magnetic and have been most extensively investigated. However, no agreement has yet been reached as to the source of the ferromagnetism arising from these nonferromagnetic elements. Absence of reliable quantitative data makes speculation hazardous. The value of much of the earlier work was vitiated by lack of necessary precautions against contamination, and by lack of close control of heat-treatment. It was only recently established that in aluminum Heusler alloys" the ferromagnetism arose from a single phase, an ordered body-centered-cubic structure. With modern methods of preparation, heat-treatment, and X-ray examination, it is possible to prepare these alloys without contamination, to heat-treat them intelligently, and to determine what phase or phases are present in the finished sample. In the present investigation, a series of pure alloys in the comparatively neglected copper-manganese-tin system have been prepared, which consist of a single, body-centered-cubic structure (the beta phase) and whose compositions vary within wide limits. The magnetic saturation values of these single-phase alloys have been quantitatively determined, so that considerable data on the effect of composition on the ferromagnetism have been made available. In the course of the investigation some information on the extent of the stability of the beta phase and the nature of phases in adjacent regions of the ternary diagram has been accumulated. Anomalies in earlier data have been explained, and alloys have been prepared that are much more strongly magnetic than any previous Heusler alloys. PREVIOUS WORK In the original work of F. Heusler1 and coworkers,2 a maximum magnetic saturation value of I = 107 was found at the composition Cu6Mn3Sn, while a value for Cu2MnA1 of I = 443 was early measured. Ross and Grays found a second maximum at the composition Cu2MnSn, which was much more magnetic than Heusler's original alloy. F. Heusler6 then reinvestigated the system, confirmed their results,

Jan 1, 1941

By Paul F. Kerr

The insufficiencies of our mineral resources are becoming well known, and the national political conscience seems to be troubled at last by our dependence upon mineral commodities which must come from other lands. This realization places increased responsibility upon the industrial, educational, and governmental groups whose task it will be to solve the problems of mineral supply. As we all know, from the time that man first sought mineral deposits until recent years, prospectors have been largely responsible for mineral discoveries. Today the era of the prospector is almost over. The human ants that have literally examined all accessible outcrops and have tested the gravels of nearly all stream beds in the United States have left undiscovered few worthwhile mineral deposits within the scope of their recognition. The pages in the history of mineral exploration are now being turned from the era of the surface prospect to the era of the hidden de- posit.

Jan 1, 1949

By AIME AIME

HEREWITH is presented a preliminary report of a special committee, consisting of Erle V. Daveler, Paul D. Merica, and C. H. Mathewson (chairman), dealing with sundry matters of which many are of vital interest to all members of the American Institute of Mining and Metallurgical Engineers. As the report states, the initial purpose of the investigation was to determine ways and means to stimulate "the welfare and growth" of the Institute of Metals and Iron and Steel Divisions. However, it soon became apparent to the committee that most of the problems and possible correctives were of no less vital concern 1o members of the other Divisions and to the "unattached" group of members. Consequently, the Committee has authorized publication of the report and invites written comment from any member on the specific recommendations or on any other phase of the broad subject.

Jan 1, 1943

By E. W. Wagy

The year 1927 witnessed numerous developments of significance in California. The State's shut-in production increased from an average of 58,000 bbl. daily in January to a maximum of 93,000 bbl. daily in August, and a total of about 25,000,000 bbl. was withheld from the market during the year. This not only lessened the effect of large production at Hunt-ington Beach, Seal Beach and Alamitos Heights, but also was a most effective conservation move. Since 1922, it is estimated that approximately 100,000,000 bbl. of oil that would otherwise have been produced have been held in the ground. I. Outstanding Field Developments of 19271 1. Long Beach Deep Sand. 2. Rincon (Seac1iff)Discovery. 3. Alamitos Heights Discovery. 4. Ventura Avenue Extension. 5. Round Mountain Discovery. 6. Mt. Poso Extension. 7. Potrero (Cypress) Discovery. 8. Buttonwillow Gas Development. 9. Goleta Discovery. 10. Union Avenue, Edison and Fruitvale Areas. (See Fig. 1.) II. Crude Production The most important factor in new crude production in 1927 was the Seal Reach field with its adjacent Alamitos Heights townlot area. Production increased from about 10,000 bbl. daily in January, to a peak of 66,000 bbl. in June. Huntington Beach finished the year 1926 with a production of 102,000 bbl. daily, which declined to 60,000 bbl. by the end of 1927. Due to production in these three areas and the tempering effect of shutting in numerous wells, the California production curve for 1927 was held at a fairly even level. Fig. 2, shows the State's production in 1927 and 1926 as compared with 1923, which was the year of excessive

Jan 1, 1928

By E. Rudy, St. Windisch

The only complete phase diagram investigation of the Ti-W system is by Maykuth and coworkers,&apos; Fig. 1. Although previous work by Gonser2 indicated complete miscibility, later investigations3°5 essentially confirmed the diagram depicted in Fig. 1. The present study was undertaken because preliminary results on metal-rich ternary Ti-W-C alloys indicated complete solid solubility between 0 titanium and tungsten at temperatures above 1300°C—in contradiction to the presently accepted diagram. The powdered elements, as well as crystal bar titanium and tungsten sheet, were used in the preparation of the experimental alloys. The iodide titanium, obtained from Foote Mineral Co., Exton, Pa., had a total impurity content of less than 410 ppm, of which 150 ppm were interstitials (H, O, N, C). The overall purity of the titanium powder (Var-Lac-Oid Chemical Co., New York) was better than 99.7 pct. Major contaminants, in ppm, included: 0, 800; N, 10; H, 1500; Fe + Co + Ni + Cu + Zn, 50; C1, 200. The measured lattice parameters of the titanium were a = 2.94A and c = 4.68,A. The tungsten sheet and the tungsten powder (Wah Chang Corp., Albany, Ore.) contained the following impurities (in ppm, values in parentheses refer to the sheet tungsten): Mo, 50 (70); 0, 140 (110); Fe, 20 (60); Ni, 20 (not determined); N, 110 (not determined); sum of other impurities, <60 (<100). Samples from the iodide titanium bar stock and from tungsten sheet were prepared by repeated melting of the chipped materials in a nonconsumable electrode arc furnace under high-purity helium. The melted alloys were heavily cored, and homogeneity of the alloys could only be achieved after prolonged heat treatments at subsolidus temperatures. The majority of the alloys were therefore prepared by cold compacting the well-mixed powders in steel dies and pre-homogenizing the compacts for 6 hr at 1300°C in a tungsten-element furnace. The vacuum was better than 10"6 Torr, but for additional protection the sample container was wrapped in zirconium foil. Both preparation methods led to identical results. The measurements of the solidus temperatures were carried oat in the Pirani-type furnace described in a previous paper.6 Incipient melting in alloys containing between 20 and 90 at. pct W was rather difficult to detect visually, and therefore a photoelectric transducer system7 was employed to indicate the phase change. For the investigation of the solid-state equilibria, the specimens were first homogenized for 2 hr at slightly subsolidus temperatures in the Pirani fur- nace and then reequilibrated at, and rapidly cooled (-100°C per sec) from, the selected equilibrium temperatures. After the runs, the alloys were analyzed microscopically and by X-ray diffraction. With the exception of spot checks for oxygen and nitrogen in processed alloys, no other chemical analyses were performed. However, as the weight changes of the alloys during processing were within 0.05 pct and the lattice parameters of indeqendently prepared alloy series agreed within 0.0015A, it is reasonable to assume that no significant concentration shifts with respect to the nominal compositions had occurred. The measured solidus temperatures, shown together with literature data in Fig. 2, ascend smoothly from

Jan 1, 1969

By Carl Altstetter, Emmanuel deLamotte

The influence of an external stress and plastic deformation on the allotropic transformation of single crystals of a Co-30.5 pct Ni alloy was investigated. Experimental results were obtained from dilatometry, X-ray diffraction, and optical and electron microscopy. The effects of stresses could be conveniently divided into three stress ranges. In range I, from 0 to about 400 g per sq mm, the specimens exhibited a multi-variant phase change on cooling and a considerable amount of retained cubic phase. In range II, from 400 g per sq mm to the elastic limit, hexagonal regions of a given orientation grew in size and the cubic phase disappeared with increasing stress level. In range III, just above the elastic limit, specimens transformed into hexagonal single crystals. It was found that plastic deformation, not applied stress, was the factor which determined whether a single-crystal product was formed. The observed macroscopic shear directions were mainly (112) on cooling, but the behavior was more complicated on heating under stress. To explain these properties of the phase change, a model based on the nucleation of partial dislocations is proposed. IT is well-known1 that, on heating, hcp cobalt transforms into an fcc arrangement by shearing on close-packed planes. The crystallographic orientation relationship of the phases is as follows: the habit plane is (OOO1)hcp ?{lll}fcc and a (1010)hcp direction is parallel to a (112)fcc direction. The temperature at which the transformation occurs in pure cobalt is around 420.C 1,2This temperature decreases with increasing nickel concentration: and at about 30 pct Ni it reaches room temperature. However, many of the transformation characteristics remain essentially the same, particularly the crystallographic features.495 A convenient way of studying the transformation is to alloy cobalt with nickel, thus avoiding the difficulties of doing experiments at the high temperatures needed to transform pure cobalt. Due to the hysteresis of the transformation it is possible to choose a Co-Ni alloy with an Ms temperature below room temperature and an A, temperature above room temperature. Either structure of such an alloy could then be studied at room temperature, depending on whether it had just been heated or cooled to room temperature. The choice of nickel is further favored by the small difference in lattice parameters between cubic cobalt and nickel and the similarity of their physical, chemical, and electronic properties. Co-Ni alloys are reported to have neither long- nor short-range order.6 The main purpose of this work was to investigate the influence of an external stress on the transformation characteristics of Co-Ni single crystals. It may be expected that slip, twinning, and transformation should have many features in common in cobalt, because the (111) planes of the cubic phase operate as slip planes when plastic deformation by slip occurs, they are the twinning planes, and they are the habit planes for the transformation. Many previous investigators7-&apos;6 have concluded that dislocations must play an important role in the nucleation and propagation of the transformation, just as they do for slip and twinning propagation. An external stress will affect their motion, and a study of its influence should yield further information about the atomic mechanism of transformation. The present work extends that of Gaunt and christian17 and Nelson and Altstette18 in both qualitative and quantitative effects of stress. The basic concept underlying all the present theories of the transformation of cobalt and Co-Ni alloys is the motion of a/6<112> partial dislocations over {1ll} planes of the cubic lattice. The ABCABC... stacking of the close-packed planes of the cubic phase can be changed into the hexagonal ABABAB... stacking by the sweeping of an a/6 <112> partial on every second plane. Twinning, on the other hand, requires a shear of a/6 <112> on each close-packed plane. The reverse transformation can be effected in a similar way by a/3 (1010) dislocations moving over every other basal plane of the hexagonal phase. Transformation theories2, 7- 12,14 differ in the details of the nucleation of the transformation and the propagation of the partial dislocations from plane to plane. EXPERIMENTAL PROCEDURE Nickel and cobalt rods supplied as 99.999 pct pure were induct ion-melted together under a vacuum of about 10-5 torr in a 97 pct alumina crucible. An alloy containing 30.5 pct Ni was found to have the desired transformation range, with an Ms near -10°C and an j4s in the vicinity of +10O°C. The ingots were swaged to &--in. rod and electron beam zone-leveled in a 10-6 torr vacuum. This procedure resulted in 12-in.-long single fcc crystal rods (designated I to VII) from each of which several tensile specimens of identical orientation were made. Chemical analysis of the bar ends indicated no contamination or gross segregation and no micro segregation was seen in electron micro-probe scans. Tensile specimens with a 9/32-in.-sq by 1-in.-long gage section were spark-machined from the rods and then electropolished or chemically polished to remove the machining damage and to provide a flat surface

Jan 1, 1970

By A. M. Nicholas

WHEN attempting to lift mill pulp containing a considerable percentage of wolframite, in an ordinary bucket elevator, difficulty was encountered from the tendency of the tungsten minerals to settle, on account of their high specific gravity. Lifts not exceeding 20 ft. (6m.) could be accomplished without particular difficulty, because there was insufficient time for consolidation of the heavy minerals in the bottom of the bucket; but with higher lifts, the heavy tungsten minerals would settle so solidly that when the bucket turned over at the top of the elevator the contents could be only partially dumped. In this case it ,was necessary to lift the material a distance of 34 ft. (10m.); hence some means had to be adopted to prevent settling, at least to such an extent that the material could be dumped from the buckets. To reduce the carrying time to a sufficient extent would have required a belt speed of 475 ft. (144.7m.) per minute, which was not feasible. It was decided to try, by vibrating the belt about midway of its span, to keel) the material sufficiently agitated during elevation to prevent settling. Underneath the rising side of the belt was placed a 12-in. (30.48-cm.) idler pulley, 18 ft.-(5.5 in.) up in the total lift of 34 ft. The idler pulley was set eccentric by 3/4 in. (19 mm.) and it was hoped that the vibration thus imparted to the belt, running at a speed of 280 ft. (85 m.) per minute, would prevent settling in the buckets. It was found that the pressure of the belt on the idler, due to the small inclination of the elevator, was not sufficient to overcome sliding on the idler, and the agitation was insufficient to accomplish the desired purpose. The idler was then connected to the drive shaft of the elevator through an intermediate pulley, gearing down to a speed of 20 r.p.m., so that a positive vibration was imparted to the belt; this imparted enough motion to the belt to prevent settling and the contents of buckets clumped satisfactorily.

Jan 2, 1918

By John E. Caffrey

The Federal Coal Mine Health and Safety Act of 1969, Title III, Interim Mandatory Safety Standards for Underground Coal Mines, is devoted to protection of workmen from hazards of electricity, roof, ribs, fire, and explosions. The Rules and Regulations, promulgated through the Federal Register, provide the criteria by which the law would be administered. Certain aspects of the law involve features that could be summarized under entrapment. These are sections 303 (y)(1), (y)(2) and 317 (f) (4). This paper is intended through the use of the figures to describe how these features of the law affect mine ventilation design, what are the problems, and possible solutions to them.

Jan 1, 1974

By Eckhard Nembach

The phase diagram of the system Pb-In has been investigated between -27° and + 40°C, using nzainly X-ray dijfraction. In accordance with t her mo dynamic measurements by Heumann and Predel, a segregation occurs at low temperatures, though not in the form of a nziscibility gap. THE phase diagram of the system Pb-In has been the subject of extensive investigations,1&apos;1 but recently Heumann and prede13 concluded from their thermodynamic data that a new feature should occur below room temperature. These authors observed that the maximum values for the enthalpy and entropy of mixing, which occurred at a composition of 50 at. pct Pb, were +400 and —1.7 cal per g-atom deg, respectively. From this the authors estimated that a miscibility gap should occur below 30°C, centered at 50 at. pct Pb. Resistivity measurements seemed to support this view. These authors proposed the phase diagram outlined in Fig. 1. Three phases exist at 30°C: the tetragonal indium phase with c/a > 1, the tetragonal intermediate phase a, with c/a < 1, and the fcc lead phase. During an investigation of the superconducting properties of Pb-In alloys. it has been observed4 that aging a specimen with 50 at. pct Pb for 14 days at -18°C decreased the superconducting transition temperature about 0.13"K and tripled the transition width. In this paper, the results of an investigation of the Pb-In phase diagram in the temperature range from — 2T to +40°C are reported. Superconductivity and X-ray methods have been used. 1) SPECIMEN PREPARATION The materials were provided by the American Smelting and Refining Co. According to the manufacturer their purity was 99.999 pct. The weighed amounts of the constituents were sealed in quartz tubes under an atmosphere of 10 torr helium, mixed for 24 hr in a rocking furnace at 380°C, quenched in ice water, and homogenized at 20" to 30°C below the solidus line, established by Heumann and Predel. The annealing times were 144 hr for specimens containing Less than 30 at. pct Pb and 36 hr for the remainder. 2) SUPERCONDUCTIVITY EXPERIMENTS The specimens were quenched from the homogeniza-tion treatment into ice water and their superconducting transition temperatures T, measured. The procedure used has been described in Ref. 4. The transition was detected by the change of the mutual induc- tance of two coaxial coils containing the sample. T, was defined as the temperature at which 50 pct of the total change in inductance had occurred. The repro-ducibility with which T, could be measured was i0.002"K. Then the specimens with lead contents between 38 and 75 at. pct were aged for 7 days at temperatures between -30" and 40°C. If this treatment caused T, to change by more than 0.005"K or the width of the transition to increase by more than 0.002"K, it was concluded that the specimen had undergone a phase change and no longer consisted only of the fcc lead phase: as it did immediately after homogenizing. The result is shown in Fig. 2. From this one can estimate at what temperatures and concentrations phase changes occur. The X-ray measurements were based on these preliminary results. 3) X-RAY EXPERIMENTS Because of the softness of the material, relatively coarse powders. 75 p, had to be used, which were filed in a helium atmosphere from homogenized specimens. The powders were annealed at least 30 min at temperatures between 120" and 16OJC, depending on their concentration, and quenched in ice water. Then their X-ray patterns were taken at -178°C with a Picker diffractometer, model 3488K, and a cold stage. on which the specimen was in thermal contact with a liquid-nitrogen reservoir. In this way the following relation was established for the fcc lead phase: a = 4.697 + 0.00247C for 40 5 C 5 75 11 where n is the lattice constant (A) and C is the at. pct of lead. The coarseness of the powder made it impossible to use lines with 0 > 75 deg; therefore n was averaged from lines with 45 deg 5 0 5 75 deg. The results were reproducible to within i0.05 pct. Relation [I] is very similar to the one found by Heumann and Predel at room temperature. Following this, homogenized specimens with compositions between 15 and 56 at. pct Pb were aged for at least 10 days at temperatures between -27" and

Jan 1, 1970

By D. W. Mitchell

While pure magnesium does not corrode rapidly the presence of even very small quantities of certain other metals accelerates corrosion remarkably. Because magnesium is such an electropositive metal (E° = +2.34 volts)&apos; the presence of substances that permit galvanic activity is extremely undesirable. It is stated that as little as 0.017 pct of iron in magnesium causes a marked increase in the corrosion rate.2 Magnesium and its alloys are commonly melted in iron or steel pots; consequently the commercial metal has the opportunity to pick up iron if it has that tendency. Quantitative data on the solubility of iron in magnesium are of practical as well as of academic interest. Some magnesium alloy castings tend to have large grain size unless suitable treatment is given to the liquid metal just prior to casting. One method of grain refinement consists of "superheating" the metal just prior to casting. "Superhcating" is heating to a temperature 100 to 200°C above the casting temperature and holding for a short period of time. Superheated metal has a much finer grain than unsuperheated metal. A satisfactory explanation of this phenomenon has not been forthcoming. One hypothesis attributes the grain refinement in the superheated metal to precipitation of some phase that is mis-cible at the temperature of superheat but not miscible just below the casting temperature and which is thought to provide nucleating centers for crystallization. This phase, if the foregoing hypothesis is correct, would probably be a metal or an intermetal-lic compound. Of the metals likely to be found in magnesium alloys, iron is one of the most likely candidates for the role of grain refiner for iron occurs in small quantities in all commercial magnesium and magnesium alloys. A. Beck³ states that magnesium, in either the liquid or the solid state, cannot dissolve iron and that iron exists as a finely divided suspension which does not settle out because of its extreme fineness. Beck also presents a micrograph showing a large iron dendrite in magnesium but does not comment on the crystallization of iron from a solution supposed to contain none. It is doubtful that dendrite formation from suspended iron -would be possible. This suspension theory is the basis of patents4 covering the removal of iron from magnesium by allowing the iron particles to act as nuclei for the formation of primary magnesium crystals which can be separated by segregation. Also covered by patents is the removal of iron by the addition of another metal to form an intermetallic compound with the iron which, because of its increased particle size, is able to settle out of the molten metal. Here, too, quantitative information on the extent of iron solubility in liquid magnesium is of more than theoretical interest. M. Hansen,5 in his critical collection of the data on binary alloys, states that iron is not soluble in liquid magnesium. W. R. D. Jones% ho studied the physical properties of low iron magnesium alloys observed a 57°

Jan 1, 1949

By B. B. Rath, Hsun Hu

In wedge-shaped bicrystals of zone-refined aluminum it is observed that (111) pure tilt boundaries migrate under the driving force of their own inter-facial free energy. The boundary velocity is a power function of the driving force. The driving force exponent decreases with decreasing angle of misorien-tation. For example, at 64O°C, the exponent decreased from 4.0 for a 40 deg to 3.2 for a 16 deg tilt boundary. An evaluation of the driving force acting on the boundaries during their motion indicates that for low driv-forces, up to about 2 x l03 ergs per cu cm, the velocity is relatively independent of misorientation, whereas at higher driving forces a 40 deg tilt boundary exhibits the highest velocity. The measured activation energy for boundary migration approaches that for bulk self-diffusion at low driving forces, decreasing from 33 to 27 kcal per mole as the driving force is increased from 1 x l0 to 5 x l03 ergs per cu cm. These results are compared with current theories of grain-boundary migration. In previous experimental studies of grain boundary migration the driving force has been limited to a difference in stored energy across the boundary. This stored energy has been introduced into the crystal either by prior deformation1-3 or by grown-in lineage structure. A part of the energy stored in the deformed crystal is released by recovery either prior to or concurrently with grain boundary migration, thus introducing an uncertainty as to the magnitude of the driving force responsible for grain boundary migration. The grown-in lineage structure, though thermally stable during annealing, neither provides conditions under which different levels of energy may be stored in the imperfect crystal nor provides a control of orientation difference across the migrating boundary of a growing grain. Furthermore, because of variation in the lineage structure, it is difficult to determine accurately the energy stored in the imperfect crystal. Several investigations of grain boundary migration during normal grain growth have also suffered from difficulties in estimating the driving force because of uncertainties in the principal radii of curvature.~ In the present investigation the velocity of pure tilt boundaries in zone-refined aluminum bicrystals of selected orientation (40, 30, and 16 deg around the [Ill] tilt axis) has been measured in the absence of a dislocation density difference across the moving boundary, thus eliminating the previous experimental difficulties. The driving force for boundary migration is derived from a gradient of the total interfacial free energy of the migrating boundary in wedge-shaped bicrystals. A similar method was attempted by Bron and Machlin in a study of grain boundary migration in silver. However, they found that one of the crystals was deformed and consequently the motion of the boundary was partly due to a difference of stored energy across the boundary. The observed behavior of boundary velocities as affected by the driving force is examined in the light of the predictions of the current theories of grain boundary migration.7"10 The effect of boundary misorientation on velocity is compared with the theory of " which is based on a dislocation core model for high-angle boundaries. EXPERIMENTAL METHOD Seed-oriented bicrystals of zone-refined aluminum, 2.5 cm wide, 0.5 cm thick, and 12 cm long, containing tilt boundaries with a common (111) axis, were grown from the melt in the direction of this axis. Spectro-graphic analysis, reported earlier,&apos;&apos; indicated the purity of the crystals to be 99.999+pct. Three such bicrystals containing 16, 30, and 40 deg tilt boundaries were used. Wedge-shaped specimens were prepared from these bicrystals by spark cutting followed by electrolytic polishing. The angle of the wedge was usually 40 deg and the specimens were usually 0.25 cm thick. The intercrystalline boundary was located within 0.2 to 0.5 cm from the tip of the wedge. Fig. 1 shows a section of an oriented bicrystal containing an outline of a wedge-shaped specimen. The crystallographic directions shown in Fig. 1 represent the orientation of one of the crystals (the larger section of the bicrys-tal); the orientation of the other crystal differs only by rotation around the common [lil] axis. The parallel faces of the wedge always corresponded to the common (171) planes in both crystals, whereas the orientation of the side faces varied, depending on the misorientation angle. The bicrystal orientations were determined

Jan 1, 1970

By David W. Mitchell

WHILE pure magnesium does not corrode rapidly the presence of even very small quantities of certain other metals accelerates corrosion remarkably. Because magnesium is such an electropositive metal (E° = +2.34 volts)&apos; the presence of substances that permit galvanic activity is extremely undesirable. It is stated that as little as 0.017 pct of iron in magnesium causes a marked increase in the corrosion rate.2 Magnesium and its alloys are commonly melted in iron or steel pots; consequently the commercial metal has the opportunity to pick up iron if it has that tendency. Quantitative data on the solubility of iron in magnesium are of practical as well as of academic interest. Some magnesium alloy castings tend to have large grain size unless suitable treatment is given to the liquid metal just prior to casting. One method of grain refinement consists of "superheating" the metal just prior to casting. "Superheating" is heating to a temperature 100 to 200°C above the casting temperature and holding for a short period of time. Superheated metal has a much finer grain than unsuperheated metal. A satisfactory explanation of this phenomenon has not been forthcoming. One hypothesis attributes the grain refinement in the superheated metal to precipitation of some phase that is miscible at the temperature of superheat but not miscible just below the casting temperature and which is thought to provide nucleating centers for crystallization. This phase, if the foregoing hypothesis is correct, would probably be a metal or an intermetallic compound. Of the metals likely to be found in magnesium alloys, iron is one of the most likely candidates for the role of grain refiner for iron occurs in small quantities in all commercial magnesium and magnesium alloys. A. Beck&apos; states that magnesium, in either the liquid or the solid state, cannot dissolve iron and that iron exists as a finely divided suspension which does not settle out because of its extreme fineness. Beck also presents a micrograph showing a large iron dendrite in magnesium but does not comment on the crystallization of iron from a solution supposed to contain none. It is doubtful that dendrite formation from suspended iron would be possible. This suspension theory is the basis of patents4 covering the removal of iron from magnesium by allowing the iron particles to act as nuclei for the formation of primary magnesium crystals which can be separated by segregation. Also covered by patents is the removal of iron by the addition of another metal to form an intermetallic compound with the iron which, because of its increased particle size, is able to settle out of the molten metal. Here, too, quantitative information on the extent of iron solubility in liquid magnesium is of more than theoretical interest. M. Hansen,5 in his critical collection of the data on binary alloys, states that iron is not soluble in liquid magnesium. W. R. D. Jones6 who studied the physical properties of low iron magnesium alloys observed a

Jan 1, 1948

By E. L. Tucker

PREVIOUS investigations of E. L. Tucker and R. E. Head&apos; related in particular to the effect of cyanogen compounds on galena, sphalerite, and pyrite, and their behavior in the presence of such com- pounds. The present contribution deals with the float- ability of the copper minerals and of pyrite. All experiments were performed on minus 200-mesh material, the method of preparation being the same as that described in the previous article. Flotation tests were made in a small mechanically agitated machine of 50-g. capacity designed in this laboratory by Gates and Jacobsen." General Naval Stores pine oil No. 5 and potassium xanthate were used in constant amount in all of the experiments; these agents were selected because of their present wide use in the flotation of copper minerals. Lime additions were varied to secure four &apos;final hydrogen ion concentrations, namely, neutral, 0.0005 per cent CaO, 0.003 per cent CaO, and 0.02 per cent CaO. The variation in lime addition was introduced to include the range of alkalinities employed in actual flotation practice.

Jan 1, 1926

New York Meets first Wednesday after first Tuesday of each month. DAVID H. BROWNE, Chairman. PERCY E. BARBOUR, Vice-Chairman. A. D. BEERS, Secretary, 55 Wall St., New York, N. Y. C. A. BOHN, Treasurer. Boston Meets first Monday of each winter month. W. E. C. EUSTIS, Chairman. - R. L. AGASSIZ, Vice-Chairman E. E. BUGBEE, Secretary-Treasurer, Mass. Inst. of Technology, Boston, Mass. ALBERT SAUVEUR, H. L. SMYTH. Columbia Holds four sessions during year. Annual meeting in September or October. STANLY A. EASTON, Chairman. FREDERIC KEFFER, Vice-Chairman. LYNDON K. ARMSTRONG, Secretary-Treasurer, P. O. Drawer 2154, Spokane, Wash. D. C. LIVINGSTON. FRANK A. ROSS.

Jan 12, 1916

By N. A. D. Parlee, E. M. Sacris

OVER 55 years ago, Sieverts and Hagenacker1 and Donnan and shaw2 made determinations of the solubility of oxygen in liquid silver, over a rather short range of temperatures (973° to 1125°C), using quartz bulbs, mainly at 1 atm. From the results of their investigations, Mizikar, Grace, and parlee3 plotted % O vs 1/T and obtained the following straight-line equation for solubility at 1 atm: log % O = 723.7/T - 1.0949 Recent work on the kinetics of the Ag-O2 system394 indicated there might have been some error due to reaction with the direct heated silica bulbs. Thus it became important to redetermine the solubility with the silver contained in a better refractory such as alumina, and by induction heating where the walls of the container were not so strongly heated. It was also desirable to extend the temperature range. A modified Sieverts apparatus of fairly standard type was used except that a special type of reaction tube was employed, Fig. 1. Dried argon with a guaranteed purity of 99.9 pet, and dried medical-grade oxygen with a guaranteed purity of 99.6 pet containing a little nitrogen, were the gases used. The measuring system consisted essentially of a manometer and a water-jacketed 100-cc gas buret with an open-end vertical tube parallel to the buret. This tube has the same diameter as the buret in order to give the same capillary effect on the mercury. A screw leveling device was used with the buret leveling bulb to help provide accurate pressure readings. A 2-mm ID capillary line connected the buret to the reaction chamber, helping to reduce the dead volume, which was determined with argon. The heating medium was a 2.5-kw output induction furnace. The induction coil was made of a 3/16-in. copper tubing with eight turns and an inside diameter of 4 cm. The reaction bulb was made of a quartz tube 18 cm long and 3 cm in inside diameter, Fig. 1. Inside the quartz tube were two alumina crucibles (Mor-ganite Triangle RR, XN10 and XN5) one inside the other. Below these two was an alumina disk. The disk prevented the corners of the outer crucible from expanding against the quartz tube. The solid sample (99.994 + pet Ag), which had been previously cleaned by air oxidation and repeated removal of scum, was placed inside the inner crucible. An alumina disk with a hole at the center covered the two crucibles. In order to decrease the dead volume, an evacuated quartz "filler" tube was placed on top of the crucible cover. The part of the reaction tube above the spherical joint was made up of Pyrex glass with a flat glass top. It was here that a prism was placed to facilitate the use of an optical pyrometer, previously calibrated at the freezing point of silver. This type of reaction bulb and furnace assembly was specially designed for this work, and used in preference to the relatively new water-

Jan 1, 1965

By F. F. Aplan

INTRODUCTION Coal is a solid combustible mineral substance resulting from the alteration of vegetable matter largely in the absence of air. It occurs in nature with varying percentages of mineral matter associated with and incorporated into the coalified material. If the amount of this inorganic mineral matter is sufficiently small, and if selective mining can be practiced so as to avoid the incorporation of ash- bearing material from adjacent strata and/or parting seams, the coal can be used as-mined. Otherwise, it must be given a preparation treatment. In 1980 the bulk of the approximately 525 coal preparation plants were located in the eastern half of the U.S., largely in the Appalachian and to a lesser extent in the midwest coal fields (1). Only 17 of these preparation plants were located in the west; these were in Colorado, New Mexico, Utah, Washington and Wyoming. In the past, however, a great many more preparation plants were operated in these and other western states. The upsurge in both the domestic and world- wide demand for quality coking and steam coal will certainly lead to an increase in the number of preparation plants in the west. In fact, there has been a massive development of coal mines and their associated preparation plants across our northern border in Alberta and British Columbia, largely to serve the export coking and steam coal market. Most of the tremendous increase in newly-mined coal in the western U.S. has come from thick seams of inherently low-sulfur, low- ash coal, easy to mine selectively without significant contamination with ash-forming minerals and requiring no preparation. Because of

Jan 1, 1983

By George M. Fowler

DURING 1937 the subject of mining geology was probably given more attention and more mining geologists were usefully employed than at any previous time. Of the many contributing factors the most important were: (1) a higher degree of prosperity in many countries, (2) a. better understanding of geologic phenomena, and (3) the apparently diminishing reserves of several important minerals. Mining companies have come to look upon geology with a growing appreciation of its aid in the more effective exploration and exploitation of mineral deposits. Most of the larger and more active companies have one or more geologists permanently attached to their staffs and some have well organized and efficiently managed geological departments. Even the smaller companies, who feel they cannot afford to employ a geologist on a permanent basis, are seeking the advice of competent men in this field with increasing frequency. One of the most significant trends has been the growing tendency to base exploratory work on more thorough geologic studies instead of empirical "hunches,"on which so much off the work in the past has relied. Likewise, mining companies are apparently more willing to expend larger sums on the basis of geologic possibilities in a district.

Jan 1, 1938