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By H. C. Gatos, J. T. A. Pollock

It is well known that the superconducting critical current densities of many alloy superconductors may be increased by cold working and in some cases further enhanced by a short heat treatment. This latter enhancement has been attributed to the redistribution of dislocations into cell-like networks' and to the precipitation of second phase particles,2'3 which act as flux pinning centers. In a manner analogous to dislocation pinning in precipitation hardening alloys,4 it is expected that here also a critical distribution of the pinning centers should result in maximum pinning effect. Concentration inhomogeneities exist in most or all commercial alloys yet there have been only a few attempts made to determine their effect on critical current capacity in the absence of cold working. Sutton and Baker,5 and Kramer and Rhodes6 have found that the complex precipitation processes occurring during the aging of Ti-Nb alloys can result in critical current density enhancement. Livingston7-10 has clearly shown, for lead and indium based alloys, that the distribution of precipitated second phase particles is of critical importance in determining magnetization characteristics. However, these '(soft" alloys age at room temperature and the time involved in specimen preparation prevents metallographic examination in the state in which the superconducting measurements are made. Thus results with such alloys are expected to be biased towards larger precipitates and interpar-ticle spacing. The present study of Ta-Zr alloys was undertaken to examine the influence of second phase precipitation, as controlled by heat treatment, on the critical current capacity of well annealed polycrystalline material. A study of the published phase diagram11 indicated that annealing supersaturated samples containing up to 9 at. pct Zr at suitable temperatures would result in the precipitation of a zirconium-rich second phase. It was MATERIALS AND PROCEDURE The alloys were prepared from spectrochemically pure tantalum and zirconium. Analysis was carried out by the supplier. Major impurities in the tantalum were: 12 pprn of 02, 17 pprn of N2, 19 pprn of C, and less than 10 ppm each of Mo, Nb, Al, Cr, Ni, Si, Ti. The crystal bar zirconium was pure except for the following concentrations: 15 pprn of 02, 17 ppm of C, 23 ppm of Fe, 11 ppm of Cu, and less than 10 pprn each of Al, Ca, N2, Ti, and Sn. Samples were prepared in the form of 8 to 10 g but-tons by arc melting using a nonconsumable electrode on a water-cooled copper hearth in a high purity ar-gon atmosphere. Each button was inverted and re-melted three times to ensure an even distribution of the component elements. The samples were then homogenized at temperatures close to their melting points for 3 days in a vacuum furnace maintained at 5 x 10-7 mm Hg. After this treatment the buttons were cold rolled to sheets approximately 0.020 in. thick from which specimens were cut, 0.040 in, wide and 1 in. long suitable for critical current density (J,) and critical temperature (T,) measurements. These strips were then recrystallized and further grain growth was allowed by an additional vacuum heat treatment at 1800°C for 60 hr. Some second phase precipitation occurred during cooling of the furnace and a solution treatment was necessary to produce single phase supersaturated samples. This treatment was successfully carried out by sealing the samples together with some zirconium chips in quartz tubes under a vacuum of 5 x 10-7 mm Hg, heating at 1000°C for 5 hr and then quenching into water or liquid nitrogen. The samples were then heat treated at either 350" or 550°C and quenched into water or liquid nitrogen. All samples which were heat treated at 350°C were quenched in both cases by cracking the capsules in liquid nitrogen. The samples treated at 550°C were quenched by dropping the capsules into water. Analysis for oxygen in randomly selected samples indicated that the oxygen content was in the range of 175 to 225 ppm. Values of Tc were determined by employing a self-inductance technique. Jc measurements were made at 4.2oK by increasing the direct current through the wire in a perpendicularly applied field until a voltage of 1 pv was detected with a null meter. The risk of resistive heating at the soldered joints during these latter measurements was reduced by first plating the ends of the wires with indium and then soldering to the copper current leads using tin. Metallographic examinations were performed after mechanical polishing of the same samples and etching in a 4H20:3HN03 (conc):lHF(conc) solution.

Jan 1, 1970

By John V. Beall

TOO early spring may be the explanation for the poor turnout of mining and metallurgical engineer candidates at a large New York guidance conference, but it would be wiser to take a more serious view of this occurrence. Held a few weeks ago, the meeting was preceded by weeks of preparation and publicity in which many engineering societies participated. The meeting was the First Greater New York University downtown campus for splitting up anticipated to draw about 20,000 high school students from the New York area and environs. Seven of the theatres in the Paramount chain were avail- able to hold the audience for a panel program on career opportunities which was to be televised and piped into the theatres. Following the morning theatre session, students were to adjourn to the New York University downtown campus for splitting up into workshop sessions devoted to seventeen different branches-of the profession.

Jan 5, 1953

By Robert D. Pehlke, Robert G. Blossey

The solubility of nitrogen in liquid iron alloys containing chromium and nickel has been measured in the temperature range 1550° to 1700°C at nitrogen pressures to 1 ah. The solubility surface has been determined for the iron corner of the liquid metallic ternary to 21 pct Cr and 11 pct Ni. The nitrogen solubility increases markedly with increasing chromium concentration. The effect of nickel and the bilinear effect of chromium and nickel are less pronounced. The solubility data are presented, and interaction coefficients are determined from them. THE solubility of nitrogen has been determined in liquid Fe-Cr-Ni binary and ternary alloys. The work in this laboratory has been directed toward a relatively limited composition range, that is to 20 pct Cr and 10 pct Ni. Humbert and Elliott1 studied the entire ternary; but their investigation was, understandably, limited in this region. The region considered here is of the greatest commercial interest. Knowledge of the solubility in these alloys is important for accurate control of the nitrogen levels in various stainless alloys. Also, the solution behavior is of theoretical interest because of its deviations from ideal dilute solution rules at moderate chromium levels. The nitrogen solubility in the iron binaries has been reviewed extensively by Pehlke and Elliott,2 particularly with respect to the dilute solution interaction parameters. More recently, there has been some interest in accurate descriptions of solute interactions in non-dilute solutions. Most of the investigators have adopted a power series fit to accommodate any non-linearity of the data. The Taylor series expansion is adopted here, using Scimar's notation3 for the interaction coefficients. An alternate method, instead of requiring higher-order expansions, is to restrict the range of the composition variables. A planar solubility surface may be fitted to the data and its range of validity determined. If the axes of this region are displaced from the usual origin—the solvent pure iron—a change in standard state is required for the solution reaction. The standard state for nitrogen in iron is commonly taken as the hypothetical 1 wt pct solution of nitrogen in pure iron. However, for an alloy of appreciable solute concentration, e.g., 13 pct Cr or 18 pct Cr-8 pct Ni, it would be convenient to use that base composition as the solvent and redefine the solution reaction in terms of that particular solvent. A brief derivation follows, defining the free energy of solution in an alloy solvent. Following the treatment by Darken and Gurry,4 for a nitrogen pressure of 1 atm: N (pure component) = N (1 wt pct in solvent) [l] AG=RT ln100/ wt pct N in solvent Taking this reaction for an alloy solvent less the same reaction for a pure iron solvent the relation between nitrogen in pure iron and an alloy is: N (1 wt pct in Fe) = N (1 wt pct in alloy) [2] AG = RT[ln(wt pct N in Fe) - ln(wt pct N in alloy)] Adding ½ N2(g) to each side and subtracting N (1 wt pct in Fe) = ½N2(g), the total free energy for solution of nitrogen in an alloy, referred to nitrogen at infinite dilution, is given by: ½N2 (g) = N (wt pct in alloy) L3] AG°3 = -RT ln(wt pct N in alloy )PN =1 atm Interaction parameters have their usual meaning when ?G°/RT is differentiated with respect to the proper composition coordinate. If desired, the dilute alloy treatment may be utilized with the new reference composition as the solvent. This has. indeed, been done by Small and pehlke5 in their analysis of nitrogen solution in liquid 18-8 alloys. The Sieverts' technique was used for this investigation on an apparatus previously described.6 The materials used in this program were: Ferrovac-E iron, 99.95 pct, Crucible Steel Co.: chromium, 99.95 pct, Union Carbide Metals Co.; nickel, 99.9 pct, International Nickel Co. Recrystallized alumina crucibles were used with no evidence of crucible-melt reaction. RESULTS The locations of the ternary compositions investigated are shown in Fig. 1. The data of Turnock7 and small8 have been alluded to in other papers.5'6 There were no departures from Sieverts' law observed for

Jan 1, 1969

By Leroy U. Gardner

EVERY reader of this paper is well aware of the fact that the prolonged inhalation of large amounts of free silica dust results in fibrosis of the lungs, and that other inorganic dusts, except those of asbestos and the mineral poisons, are thought to be relatively harmless. But probably few have had opportunity to visualize the effects of silica, asbestos and other minerals upon living tissues. The ideal demonstration would be based upon sections of lungs from human beings that had inhaled com- parable concentrations of different dusts for a unit period of time. Such material is generally difficult to obtain and in some instances is of questionable value because the subject has been exposed to more than one kind of dust. A demonstration could be prepared from the lungs of animals. However, so many months or even years are required to complete the exposure to each kind of dust that enough material has not been accumulated. For a general survey of the action of different types of dust, I am therefore compelled to use the tissues of animals that have been injected with suspensions of dust particles. The injection method offers certain advantages. The quantity, the particle size and the state of dispersion can be controlled with sufficient accuracy so that the tissue responses to different minerals can be accurately compared. The method insures contact between the tissues and the mineral particles; protective mechanisms, which may prevent the inhalation of certain types of foreign body, never come into play. If the pathway of injection be one that minimizes nonspecific injury, the tissue responses may simulate those produced by inhalation but they develop somewhat more rapidly. It should always be remembered that injection methods merely demonstrate the capacity of various kinds of minerals to provoke reaction in the tissues; whether the same substances are inhaled from atmospheric suspension and accumulate in the lungs in dangerous quantities can be demonstrated only by inhalation. The reactions that I shall discuss first took place not in the lungs but in the liver. For the purpose in hand this is quite immaterial for we are merely seeking to discover whether these minerals are capable of produc-

Jan 1, 1938

By Clarence E. Sims

DURING the past several years the steel casting industry has made studies of heavy castings in which the test bar has been taken from heavy sections rather than from attached or separately cast coupons. It has been noted that the ductility properties of these heavy sections are often lower than those normally expected. Such lowered ductility is usually accompanied by a spotty test bar fracture and the ductility values often can be greatly improved if a low-temperature aging treatment is given to the casting. A loss of ductility of this type is considered "abnormal," since it is not accompanied by an increase of tensile strength or hardness, and "temporary" when the ductility can be restored by aging. The cure of such an abnormal condition represents a real improvement in the quality of the steel. Some hundreds of previous investigations, largely qualitative in nature, have established beyond reasonable doubt that hydrogen is normally present in newly manufactured steel and that this gas, in small amounts, can cause a temporary abnormal loss of ductility. The commonly observed association of high gas content and low ductility has given strong evidence for the presumption that hydrogen, possibly assisted by other gases, is the primary cause of the low ductility observed. Accordingly, the Steel Founders' Society of America has, since Nov. 1, 1944, sponsored investigations at Battelle Memorial Institute whose primary objective is to obtain quantitative information on the relation of the amount of hydrogen and nitrogen in steel, together with associated methods of steelmaking and treatment, to low-ductility effects and porosity.

Jan 1, 1947

By R. Maddin, C. H. Mathewson, W. R. Hibbard

According to conventional crystal mechanics, a face-centered cubic single crystal slips on the system {111} <110> which receives the highest shear stress in terms of the stated orientation of the stress axis of the crystal.l However, in brass, the slip process is never as simple as this conventional analysis indicates. There is always a second cooperating plane which contains the same slip direction as the primary plane.2&apos;3 There is still another cooperating slip system commonly called the conjugate system3 previously observed to function with considerable lag only after the rotation due to the action of the first plane had produced a symmetrical condition of equal shear stress on the two systems. In the 1943 Campbell Lecture,4 a slip mechanism was outlined in which the {111) planes moved step-wise in two adjacent <112> directions integrating into the <110> slip direction. "... the slipping process would be visualized as a succession of steps 30" to the right and left of the resultant, microscopically observed, slip direction; a first step setting up the twinned configuration in the single spacing involved and an ensuing slip returning the atoms to the untwinned configuration while completing a fully integrated <110> movement."4 This process is shown diagrammatically in Fig 1 which shows two close packed layers of atoms at a slip site. A movement of the full circles through the "valleys" into the adjacent sites would produce a twin configuration with respect to the open circles. The term, "twin fault," seems most appropriate to define this faulted condition of the lattice. Annealing twins in face-centered cubic metals may arise from preformed nucleii which could be described as twin faults produced by the first movement of this two stage slip process. However, it is clear that this kind of slip does not take place so as to embrace a measurable number of adjacent planes because careful X ray examination has not conclusively shown the existence of ponderable twin lamellae (as in the case of Neumann bands in the body-centered ferrite). In view of the imponderable character of these hypothetical twin faults, the search for evidence of their existence seems restricted to indirect methods. The most obvious experimental technique serving this purpose is the determination by micrographic and X ray methods of the alignment of the composition planes of annealing twins with the former slip planes in axially strained and recrystallized single crystals. In previous attempts of this sort not all of the annealing twins could be traced to slip planes known to be operative in the conventional sense and hence evidence appeared negative or inconclusive. With the discovery of additional slip systems2&apos;3 operating in conjunction with&apos; the major system of highest resolved shear stress in axially strained brass it became apparent that the simple technique outlined above might be re-employed with more gratifying results. If, on annealing single crystals of alpha brass previously strained in tension, twins are found with their composition planes parallel to all three operative slip planes and with no participation of the fourth plane there is good evidence in favor of the existence of twin faults and of the two stage slip process. Experimental Procedure and Resuits Single crystals of alpha brass of the 70-30 composition were grown by solidification from the molten state.

Jan 1, 1950

By A. Mitchell, M. Etienne

VARIOUS&apos;-3 reports on the electroslag remelting process refer to the "thin skin of slag" existing around the slag pool and the solidifying ingot, but none considers the various mechanisms by which this layer forms and thus influences the surface quality of the ingot. A vertical section4,5 of the Cao-CaF2-Al2O3 diagram is shown in Fig. 1 between CaF2 and 6Al2.CaO3 From this, it is seen that a typical "70:30" CaF2:A1a3 slag will solidify to produce 6Al2O3.CaO primary phase in a eutectic matrix. The commercial slags contain sufficient CaO to produce* this composition by both the

Jan 1, 1969

By P. Nicholls

PATENT records show that the attempt to improve the burning of fuel by mixture or pretreatment with chemicals dates back to the early years of the last century. By 1845 English and French patents had included the specific beneficiations of elimination or reduction of smoke, soot and clinker; reduction of the ashes; elimination of sulphur fumes; increase of the rate of burning; increase of the time a given charge of fuel would last; and, in most patents, a saving of fuel. The earlier patents specified additions up to 80 lb. or more per ton of fuel, but after 1860 the quantity was seldom more than 4 lb. There is no record of the extent to which these patents were commercialized, but after 1874 many American patents were assigned to companies specializing in treatment of coal, so it is probable that the products were marketed on a considerable scale at least as early as that date. From 1900 on, many proprietary products were marketed under the general name of "fuel savers," the principal sales being in small packages for the use of householders; savings of from 10 to 40 per cent of the coal were promised. Starting with 1927, the use of proprietary or other mixtures of chemicals was extended to power plants and to treatment of coals at the mines, the claims of saving of fuel being subordinated to those of general improvement and, in particular, to reduction of clinkering. Such expectations are attractive and a number of companies experi-mented with or adopted the practice. There were reports of improved operation, but, apparently, few were confident enough that these improvements were due to the salts to publish the results of tests or their records of operation. There are no data on the yearly tonnage of coal treated but indirect reports suggest that it has been relatively large. Since its establishment in 1910, the U. S. Bureau of Mines has con-tinually received inquiries about these products. At the request of. other governmental departments it made tests in 1910, 1916 and 1930, using certain proprietary products applied according to the instructions of the vendors; these tests were made with eastern coals in domestic and

Jan 1, 1937

By Severn P. Brown

Search for ore continued at a feverish pace-as can be attested to by anyone who has tried to arrange for extensive diamond drilling. The stakes are high, and so is the cost as was indicated by Selco Exploration Ltd. when they announced discovery of base metal sulfides at Uchi Lake in northwestern Ontario. It was apparently their first commercial find after 15 years of exploration at a cost of more than $10 million. For the first time in many, many years the big exploration news has come from east of the Mississippi River. In January, the New Jersey Zinc Co., in an unusually worded press release, stated that they had made a major zinc discovery of 13-50 million tons of ore averaging 5-10% Zn. New Jersey&apos;s holdings are said to embrace 500 sq mi. The ore was discovered in eastern Tennessee in the upper part of the Knox dolomite of early Ordovician age. Reportedly the mineralization is at depths of 900 to 2000 ft. Currently about 20 diamond drills are working the area for New Jersey. At least nine other major companies are prospecting the region, which now includes parts of Kentucky. Five hundred thousand acres are said to be under lease. Greatest activity is clustered around Carthage, Tenn. In Missouri, the St. Joseph Lead Co. announced plans to develop a new mine in the Brushy Creek area of the "New Lead Belt." copper and zinc concentrates will be by-products.

Jan 1, 1970

By C. E. Bailey

In this our fifth year of actual mining, a resume of our methods of mining may prove of interest. Our conditions are radically different from those of other districts; and we are just commencing to be able to draw conclusions regarding the systems in use. The ore-bodies of the range lie in a blanket-formation varying in width from 200 or 300 feet to over half a mile, and in length from 500 feet to more than 2 miles. It is practically horizontal in bedding, but in places has a dip of as much as 7 feet in 100 for a quarter of a mile. The top of the ore is in most cases nearly level, although local rolls make the back (or top of the ore) vary to the extent of 10, or in rare cases 20 feet, and very frequently there is a general slope of the top of the ore, as well as the bottom, which makes it impossible to mine it all from one level. Taking the average of long stretches, the side-walls may be described as quite regular; but local deflections make it necessary to prospect for the wall-rock, and in drifting underground it is common to drive along the sidewalls, uncovering them almost continuously, and thus making sure that no large pockets of ore are missed. The dip of the side-walls varies greatly, but an average is probably between 45&apos; and 60°, sloping inward at the bottom, making the general shape of the ore-body not exactly a basin, but more nearly a trough, usually with a longitudinal trend and sloping sides, and ore much the deepest at the center. As to rock-occurrences inside the ore-body, the properties most largely worked may be said to be particularly free from rock, although much trouble is occasioned by bunches or small masses. In most cases these are not properly described as " horses" of rock, since they have neither continuity nor regularity of trend, but are offshoots connected with the side-walls or bottom.

Jan 1, 1898

By J. T. Norton, Pekka Rautala

The phases and equilibria in the W-Co-C system have been studied by X-ray diffraction methods, metallographic technique, and thermal analysis. In addition to the 7 phase, two double carbides, called 8 and have been revealed. The compositions correspond to CO3 W6C2 and Co3-W10C4. The reactions leading to these phases have been explained and tentative diagrams of stable and metastable equilibria proposed. The basic reactions in sintering cobalt cemented tungsten carbides are discussed. THE W-Co-C system is of fundamental importance in practical carbide manufacturing as well as for the understanding of the sintering mechanism. Surprisingly little is known about this system, for the probable reason that all the important alloys are of two-phase structure and that the diagram Co-WC has been treated as a quasi-binary. This obviously is incorrect, because WC decomposes before melting. One ternary phase, 7, of composition Co3W3C has long been known. It was first studied by Adelskold, Sundelin, and Westgren,1 although the isomorphous iron-tungsten carbide was known earlier. There have been in the literature several reports of two 7 phases.&apos; " Also the 7 phase has been considered unstable by Takeda4 and Westgren.1 The Co-WC diagram has been studied by Wyman and Kelley5 and a quasi-binary diagram has been published by Sandford and Trent.2 Takeda has published a tentative Co-W-C diagram, considering both metastable and stable equilibria. However, the lines of two-fold saturation are shown only partially and it seems impossible to complete the diagram without violating the phase theory. Therefore it seemed desirable to examine the system in more detail. Experimental Procedure The alloys used in the present investigation were made of powders of tungsten, tungsten monocarbide, cobalt, and carbon and were of the grade used in manufacture of commercial cemented carbides. The powders were ground and mixed in small stainless steel ball mills, using balls of the same material. Benzene was used as a dispersing agent. The mixing period was 1 hr, since this was shown to give suffi- ciently good mixing of the powders without too great a contamination from the mill. After ball milling, the specimens were pressed in cylindrical or rectangular dies. No paraffin or other lubricant was used and the small compacts had sufficient green strength to be handled without difficulty. Several sintering furnaces were employed. The most satisfactory arrangement was a vacuum furnace based on the Arsem principle which employed a graphite helix as the resistance heating element. Specimens were placed on graphite stands and there was generally a slight carburization or decarburiza-tion of the specimen surface, depending on the carbon content of the alloy. The evaporation of the cobalt at a sintering temperature of 1400°C was not significant, but became severe at 1500°C and higher. The sintering time was 1 hr at 2000°C and 2 to 4 hr at lower temperatures. It was not possible to quench the specimens, but the cooling rates were rather fast, greater than 300°C in the first minute. In the system under investigation, the reactions are sluggish, and it is believed that the high temperature structures are satisfactorily retained. The principal method of investigating the sintered specimens was X-ray diffraction by the Norelco recording spectrometer. Approximate determinations of the phase boundaries were made by the disappearing phase method. Ternary Phases To study the phase formation in W-Co-C system, a series of specimens was sintered at 1400°C. In this experiment two ternary phases, called here ? and k were formed in addition to the well-known 7 phase. The 7 phase, which has been completely described by Westgren: showed a range of homogeneity from 7 to 20 pct C and from 38 to 48 pct Co. At 1400°C the 7 phase was found to be in equilibrium with monotungsten carbide, 8, tungsten, 8, #?, and liquid. The boundaries toward #? and liquid were difficult to determine and appeared to be very temperature sensitive. The other boundaries are believed to be well fixed. The homogeneity range of 7, as measured in this work, is considerably smaller than the one

Jan 1, 1953

By Ernest J. Stocking

ENGINEERS are the key men in our war program today. Upon the technical knowledge and skill of the engineer and upon his administrative and executive abilities rests the entire success for the production of vital materials of the war. Naturally the work load of the engineering examining unit of the U. S. Civil Service Commission has increased greatly since our active participation in the war. At present, over 550 separate requests for certification of eligibles are received by the engineering unit per week. These represent more than a fourth of the total requests received for personnel by the Commission&apos;s central office at Washington and represent a recruitment work load of three to four times that carried by the whole Commission previous to January 1940. These requests represent a minimum of a thousand vacancies to be filled each week, while an average week will produce, at present, approximately 1400 vacancies and a weekly maximum may approach well over 2000 vacancies.

Jan 1, 1942

By Catherine T. Aimone

Specimens of copper-bearing quartz monzonite were subjected to a plane shock wave simulating high compressional stresses in the proximity of a borehole wall. Fragmentation was studied as a function of stress levels between 1.6 GPa (23 x 104 psi) and 7.3 GPa(105.8x104 psi) and pulse durations ranging from 1.1 µs to 6.9 us. Both explosive pressure and pulse duration were shown to have a strong effect on particle size distribution. While the effect of pressure is well recognized, the effect of pulse duration indicates that ultimate fragmentation increases with the time of application of a plane wave pulse. At high pulse durations, degree of fragmentation is more sensitive to changes in pressure than at low pulse durations.

Jan 1, 1984

By F. A. Crossley

The key to disagreements between Blackburn&apos;s findings and mine is the word equilibrium". My work attempted to define the equilibrium diagram of the titanium-rich end of the Ti-A1 system. It can readily be shown that Blackburn&apos;s conclusions are based primarily on the examination of structures substantially removed from equilibrium. The diagram presented in Fig. 16 is properly labeled a "phase diagram". However, it appears that Blackburn either does not understand or does not accept the difference between "phase diagram" and "equilibrium diagram" as defined in the Metals Handbook.17 The conflict lies not in Blackburn&apos;s data but in his interpretation of it, and his use of "transformation", "phase diagram", and "equilibrium diagram" as synonymous terms. I share his view that the light microscope is much inferior to the transmission electron microscope for the study of transformations; but this fact does not render the light microscope useless or untrustworthy. The difficulties experienced with the Ti-A1 system have not been due to the limitations of the light microscope, but rather to the extreme sluggishness in achieving equilibrium at temperatures below 1000° C. Were it not for the light microscope employed with polarized light, the twin phase syndrome&apos; might still be unrecognized and, as a consequence, still adding to the confusion of Ti-A1 investigations. (Ref. 1 should read ... Contract No. N161-25952 ... vol. 236.) Other, more sophisticated techniques, including electron transmission, simply confirm the erroneous tentative conclusions drawn from observations of structures due to the twin-phase syndrome. By the standards of most of the investigations of the Ti-A1 systems, seven of the fifteen compositions investigated by Blackburn were seriously contaminated with oxygen. The writer has found that 0.1 wt pct 0 shifts the a + Ti3A1 boundary to 1 at. pct lower A1 content at 700°C. At constant aluminum content, this corresponds to a temperature shift of the boundary of +25°c.18 Blackburn advises that the first group of alloys contained 0.1 to 0.15 wt pct 0, bur he does say whether the analyses were performed on as-received material or on specimens in their final state of heat treatment. This is especially important considering the 20-mil-thick starting materials. If specimens had been annealed in the two-phase a + 6 region it would have provided an indication of the final degree of oxygen contamination since up to about 12 at. pct A1 the boundaries of this region are well-defined for low-oxygen alloys. Blackburn questions the capability of light microscopy in determining phase boundaries in the Ti-A1 system. I submit that the a/a + Ti3A1 boundary in Fig. 1 of Ref. 1 over the composition range from 10 to 18 at. pct A1 was determined by dilatometry and supported by electron diffraction. Specimens of alloys containing 8, 10, 12, and 14 at. pct A1 were aged at 550°C for 1000 hr (under stress of 5000 psi to accelerate the tendency to equilibrium) and then fractured in tension at room temperature. Collodion was applied to the as-fractured (unetched) surface and, when stripped, carried away particles identified by electron diffraction as Ti3A1. Perhaps Blackburn will explain why these electron diffraction data were ignored. At this time, a technique for revealing or indicating

Jan 1, 1969

By T. M. Daulton, Chester F. Lee

The Atlin Mining District is in the northwest corner of the Province of British Columbia. Ruby Creek, where the operation to be described is situated, is 17 miles east of the town of Atlin and about 18 miles south of the south line of Yukon Territory (Fig. 1). Gold was discovered in the district in January, 1898, and the production to date from placer mines has been $4,518,000, according to the reports of the Minister of Mines for the province. Geology The essential points in the regional geology are given in the following paragraphs. Long erosion produced a plane-like surface slightly above sea level with a few peaks and ridges.&apos; A gradual uplift followed and erosion increased, the streams cut deeper, the cuts so made being afterward increased by glaciation. The ice straightened and planed the slopes of the main valleys and widened and lowered their floors, in some cases flooring the valleys with silt, sand, gravel, and clay. As the glaciers rapidly retreated, lakes were formed. As to the origin of the gold, J. C. Gwillim says? "The Surprise granite has been carried northward toward Gladys Lake and Teslin, and the granite of the great plateau on the Taku trail was found in blocks on the opposite range across Hurricane River 10 miles north of its original position. Otherwise there is little evidence of far removed material, the boulders of the lake shore and creek beds being of local appearance. This appears to strengthen the opinion that the placer gold had its origin within the drainage basins where it is now found." In the gold-bearing creeks of the Atlin district there are two "runs"

Jan 1, 1917

By J. Leja, J. H. Schulman

FROTH flotation is usually effected by the addition of a collector agent and a frothing agent to an aqueous suspension of suitably comminuted mineral ores. The action of collectors is to adsorb onto the surfaces of minerals to be separated, sensitizing them to bubble adherence. The action of frothers has, in the past, been accepted as that of froth formation only, brought about by a lowering of the air/water interfacial tension. Substances capable of producing froth are classed1a,b according to their relative capacities for production of froth-volume and froth stability in the simple frother-water system. The purpose of this paper is to show that the surface active agents acting as frothers become effective only when there is a suitable degree of molecular interaction taking place between collector molecules and frother molecules at the air/water and solid/ water interfaces. Further, the discussion will demonstrate that the actual mechanism of adherence of an air bubble to a suitably collector-coated particle is due to the molecular interaction collector-frother. This leads to the formation of a continuous interfacial film of associated molecules, anchored to the mineral by polar groups of the collector, and enveloping the whole bubble. The tenacity of adhesion mineral-to-bubble results from the strength and the visco-elasticity of this mixed film. Some 20 years ago Christman2 postulated mutual dependence of collector and frother in effecting flotation. This view was, however, strongly opposed by Wark,3 who pointed out that an addition of frother had no effect on the value of contact angle once this was established in the solution of collector. More recent work by Taggart and Hassialis&apos; indicated that the presence of frother, namely, cresol, leads to the immediate establishment of a contact angle on sphalerite, partially coated with xanthate, whereas an air bubble fails to make contact in potassium ethyl xanthate solution alone, even after 60 min induction time. Wrobel5 raws attention to the selectivity of frothers in flotation. Many instances of antagonistic effects of certain mixtures of frothers (or collectors and frothers) on flotation froth have been known to flotation operators and have been reported in literature. Taggart6 and Cooke7 give several examples of incompatibility of certain ratios of frothers and collectors, e.g., oleate and long-chain sulphates, pine oil and soaps. Monolayer Penetration. Properties of insoluble films produced by molecules of surface active agents orientated at the air/liquid interface are conveniently studied by the Langmuir trough technique, described fully by Adam.&apos; Using the trough technique Schulman and Hughes" and Schulman et al.10a. b, c, d,e established the existence of molecular interactions occur- ring between certain types of surface active agents. Their experiments revealed the phenomenon of penetration of an insoluble monolayer (e.g., a film of a long-chain alcohol) by a soluble agent (e.g., sodium alkyl sulphate) injected into the substrate (water or salt solution). The degree of molecular interaction taking place on penetration is determined by changes in the surface pressure of the resulting film, changes of its surface potential and its mechanical properties (viscosity and rigidity). When the interaction takes place between both polar groups and both hydrophobic groups of the two participating amphipathic molecules a molecular complex is formed. Complexes formed on penetration of the monolayer at interfaces are not necessarily true chemical compounds: they are labile in solution, the activity and reactivity of individual components are greatly different from those of the molecularly associated complex, and on crystallization they usually separate out into components. However, when formed in the orientated state at interfaces they are found to be very stable, although some mixed films spread as monolayers of stoichiometric complexes can show further penetration by subsequent additions of the soluble component injected into the substrate.&apos;" The degree of association between two or more types of surface active agents is very sensitive even to small changes in electric (dipole) moment of the polar groups of the amphipathic molecules as influenced by magnitude and position of neighboring ions or dipoles, their size, concentration, and stereochemistry. In addition, the molecular association is greatly influenced by concentration and type of inorganic salts in the substrate, by its pH, and by temperature. The nonpolar groups of interacting molecules greatly affect the stability of molecular complexes. Progressive shortening of the aliphatic chain of one of the reacting molecules weakens (at an increasing rate) its tendency to form stable complexes. Similarly, introduction of a double bond of cis-form into one of the reacting chains, which changes the straight hydrocarbon chain into a kinked one, or introduction of a branched chain, reduces the stability of the associated complex. Monolayer Adsorption. Using the trough technique and injecting metal ions into the substrate (water or salt solution) underlying insoluble films of fatty acids, alkyl amines, and sulphates, Wolsten-holme and Schulman11a,b,e. &apos; and Thomas and Schulman" have established conditions, namely, pH, concentration. and steric factors, under which molecular interactions take place between the polar groups of the surface active agents and the metal ions. These interactions are marked by great changes in the solubility and mechanical properties of the monolayer of the agent; no surface pressure increases are observed as in monolayer penetration experiments. The results of these adsorption studies, correlated with flotation experiments, indicated that in the case of fatty acids and alkyl sulphates their adsorption onto minerals of base-metals takes place by a similar

Jan 1, 1955

By Craig R. Smith, Warren Pfefferle

Tests were conducted utilizing large flat jack devices placed in a vertical slot for high pressure loading of rock to measure in-situ properties of a rock mass. The high pressure flat jack devices were used as a site investigation tool to obtain rock mass properties. Tests were conducted before and after a 100 ton surface high explosive detonation test to assess explosive effects on the rock. It was conclusively demonstrated by these tests that meaningful flat jack tests could be successfully accomplished; also, a significantly different response of the rock medium was measured as larger areas of rock were loaded. Surface jointing was severely disturbed by the explosion.

Jan 1, 1971

By M. F. Goudge, R. V. Tomkins

Sodium sulfate is an important chemical raw material that is being used in ever increasing quantities in modem industry. It comes on the market mainly in three forms: (1) Salt cake (Na2SO4), a relatively crude form of the anhydrous salt containing up to 3 pct impurities, and comprising about three-quarters of the North American production; (2) anhydrous sodium sulfate (Na2SO4), a refined form containing less than 0.3 pct impurities; (3) Glauber&apos;s salt, the decahydrate (Na2SO4.10H2O) containing 55.9 pct water of crystallization. Competing with salt cake from natural sources is byproduct salt cake from a number of industrial operations. For instance there is Mannheim cake resulting from the manufacture of hydrochloric acid by the reaction of salt (NaCl) and sulfuric acid in Mannheim furnaces; rayon cake, a high-quality product, resulting from the process of making rayon by the viscose process; chrome cake from the processing of sodium chromate to dichromate; phenol cake from the manufacture of phenol; also byproduct sodium sulfate resulting from the conversion of lithium sulfate to lithium carbonate; from the processing of sodium tetraborate to boric acid; from converting sodium formate to formic acid; and in the manufacture of cellophane. Sodium sulfate is also obtained as a byproduct in the manufacture of isosebasic acid. In addition strong competition has resulted from imports of byproduct salt cake from the chemical industries of a number of highly industrialized European countries. However in recent years due to technological changes the output of byproduct salt cake is rapidly diminishing and the natural deposits are becoming the most important source of sodium sulfate used in North America. For instance, the production of hydrochloric acid in Mannheim plants has become obsolete and thus the greatest single source of byproduct salt cake will disappear. Also viscose rayon is meeting strong competition from nylon and other synthetic fibers and production of byproduct salt cake from this source may do little more than remain at the present level. These factors together with increasing demand for sodium sulfate point to increased production from natural sources. In 1958, 36 pct of the total United States production was derived from natural sources and in addition 97,000 short tons was imported so that over 40 pct of the total consumption was supplied by natural sources whereas in 1953 the proportion was only 24 pct. The rapid growth in production is shown in Table 1. Principal Sodium Sulfate Minerals There are many minerals in which sodium sulfate is a constituent but those of commercial importance at the present time, and consisting wholly of sodium sulfate in either the hydrous or anhydrous states, are mirabilite and thenardite. Minerals of potential importance but consisting in part of compounds other than sodium sulfate are glauberite in which sodium sulfate is combined with calcium sulfate, and blödite in which sodium sulfate is combined with magnesium sulfate. Mirabilite (Na2SO4.10H2O) the decahydrate, consists of 24.8 pct SO3, 19.3 pct Na2O, and 55.9 pct H20. It is a colorless to opaque, soft, water-soluble mineral with a slightly bitter taste. It has a hardness of less than 2 and a specific gravity of 1.48. It forms long needle-

Jan 1, 1960

By D. M. Wyslouzil

Standard testing methods are described that are presently used for the selection of grinding equipment. Correlation between laboratory batch grinding tests and pilot plant continuous tests are established by means of particle size distributions and flotation results. Conventional and autogenous grinding circuits are discussed showing the relationships of the controllable circuit parameters.

Jan 1, 1982

By Otto H. Henry

The purpose of this investigation was to determine the equilibrium diagram of the lithium-magnesium pair as a first step in studying the possible usefulness of these alloys as ultra-light structural materials. Review of the Literature The behavior of lithium towards magnesium was first investigated by Masing and Tammann.(1)† In order to prevent oxidation the alloys were made in iron tubes under an atmosphere of hydrogen; temperatures were measured with a glass-protected thermocouple. These investigators found that lithium and magnesium form two series of solid solutions separated by a miscibility gap between 85 and 95 per cent magnesium; that the alloys with 81 and 95 per cent magnesium showed a homogeneous structure under microscopic examination, while the alloy with 89 per cent magnesium contained two distinguishable crystallites; that the curve indicating the beginning of crystallization rises from the melting point of lithium to that of magnesium; and that no compounds of lithium and magnesium are formed. The equilibrium diagram was not plotted because no definite data were obtained for determining the solidus and the position of the miscibility gap in the solid state. The difficulties encountered in this investigation were: (1) that it was necessary to heat them as high as the melting point of magnesium in order to obtain homogeneous melts; at such temperatures the alloys attacked the glass protecting the thermocouple; and (2) that at temperatures above 400" C. the lithium united with the hydrogen to form lithium hydride, thus contaminating the alloys. By applying the same methods as those used in the lithium-magnesium system, Masing and Tammann determined the equilibrium diagram of the

Jan 1, 1934