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By Donald E. Cummings

Certain dusts are dangerous when inhaled, but most hazardous of all dusts are quartz or other forms of pure crystalline silica. The inhalation of dusts containing silica in combination with other elements gives rise to changes in the lung which differ from those produced by pure silica. As a generality, silicates are less dangerous than pure crystalline silica and vary greatly among themselves in harmfulness. Repeated analyses have shown that approximately 70 per cent of the total number of particles involved in any dust-producing operation are below 1 to 2 microns in diameter. (A micron is approximately 1/25,000 in.) Similar studies of dusts recovered from silicotic lungs post mortem have demonstrated essentially the same size frequency distribution, except that the upper limit of size retained in the air sacs is approximately 10 microns. Experiments carried on by Gardner and the author have further demonstrated that greater changes were produced by a fixed weight of very fine quartz particles (2 to 3 microns and smaller) than by the same weight of slightly larger particles (8 to 10 microns). Any attempt to control a dust hazard should therefore be directed toward the removal from the working atmosphere of particles less than 10 microns in size, and particularly those below 3 microns. All industrial hygienists agree on this matter, but there remains considerable dispute as to the lower limit of particle size capable of causing injury. It has been generally conceded, however, that particles of harmful dusts smaller than 1/4 to 1/2, micron are not essentially concerned in the development of pulmonary fibrosis. This opinion is partly substantiated by the existence of large numbers of these small particles in practically all atmospheres that are not associated with any known hazard. Such particles are so small that they have very little mass, fail to settle even in quiet air, and probably are not easily retained in the lung. Until further research proves that they are involved in the dangers provoked by the inhalation of certain dusts, engineers will generally agree that it is better to disregard them.

Jan 1, 1937

By G. V. Smith, R. F. Mehl

The decomposition of austenite in steels, because of its immerse practical importance, has been subjected to extensive study in recent years from the point of view of the mechanism of the process.1"3 Although much information has been acquired, a number of questions, principally of theoretical interest, remain. One is that of the atomic-crystallographic mechanism by which each of the various reaction products forms. The isothermal reaction products of the eutectoid decomposition in plain carbon steels (to which this study is restricted) have conveniently been classified in three general groupings—pearlite, bainite, and martensite. Of these several products, pearlite and martensite have been studied extensively, but bainite has received only scant attention. -As a result, the mechanism of the formation of pearlite and that of martensite are now fairly well understood while a great deal of uncertainty exists regarding bainite. Pearlite Pearlite forms from austenite by the precipitation of alternate platelets of cementite and ferrite, which grow into the austenite matrix.2--5 The rate of reaction may be described in terms of a rate of nucleation and a rate of growth.2.3 Mehl and Smith6 have attempted to determine the lattice relationships existing between the ferrite in pearlite and the' parent austenite. Using a pole-figure method of analysis, it was found that a limited number of ferrite orientations resulted from the decomposition of a single grain of austenite; it was not possible, however, to decide between two assumed ideal relationships, both of which appeared to account for the experimentally determined pole figure. It was definitely shown, however, that the relationship obtaining was quite different from that determined for the proeutectoid separation of ferrite.7 No attempt was made to determine the habit plane (matrix plane to which the precipitate lies parallel) of the pearlite lamellae. Belaiew8 earlier had stated that the number of directions assumed by the pearlite lamellae in a single grain of austenite was 12 (no details were given) and concluded wrong!:!, as Mehl and Smith6 have pointed out, that the lamellae delineate the {2I0} planes of ferrite.* Martensite It is known that martensite is a transiti0nal constituent of body-centered tetragonal lattice,' and that it forms suddenly

Jan 1, 1942

By R. F. Mehl, G. V. Smith

The decomposition of austenite in steels, because of its immerse practical importance, has been subjected to extensive study in recent years from the point of view of the mechanism of the process.1"3 Although much information has been acquired, a number of questions, principally of theoretical interest, remain. One is that of the atomic-crystallographic mechanism by which each of the various reaction products forms. The isothermal reaction products of the eutectoid decomposition in plain carbon steels (to which this study is restricted) have conveniently been classified in three general groupings—pearlite, bainite, and martensite. Of these several products, pearlite and martensite have been studied extensively, but bainite has received only scant attention. -As a result, the mechanism of the formation of pearlite and that of martensite are now fairly well understood while a great deal of uncertainty exists regarding bainite. Pearlite Pearlite forms from austenite by the precipitation of alternate platelets of cementite and ferrite, which grow into the austenite matrix.2--5 The rate of reaction may be described in terms of a rate of nucleation and a rate of growth.2.3 Mehl and Smith6 have attempted to determine the lattice relationships existing between the ferrite in pearlite and the' parent austenite. Using a pole-figure method of analysis, it was found that a limited number of ferrite orientations resulted from the decomposition of a single grain of austenite; it was not possible, however, to decide between two assumed ideal relationships, both of which appeared to account for the experimentally determined pole figure. It was definitely shown, however, that the relationship obtaining was quite different from that determined for the proeutectoid separation of ferrite.7 No attempt was made to determine the habit plane (matrix plane to which the precipitate lies parallel) of the pearlite lamellae. Belaiew8 earlier had stated that the number of directions assumed by the pearlite lamellae in a single grain of austenite was 12 (no details were given) and concluded wrong!:!, as Mehl and Smith6 have pointed out, that the lamellae delineate the {2I0} planes of ferrite.* Martensite It is known that martensite is a transiti0nal constituent of body-centered tetragonal lattice,' and that it forms suddenly

Jan 1, 1942

By C. E. Reistle, G. L. Nye

The East Texas field is in Smith, Rusk, Gregg, Upshur and Cherokee counties, Texas. The discovery well was completed Sept. 8, 1930, near the eastern limit of the field. Within less than one year the new field became the dominant factor in the world production of crude oil. On Aug. 16, 1931, eleven months after completion of the discovery well, there were 1644 wells in the field, and the average daily production was 584,475 bbl. Since that time the number of wells has increased to 8195 on Oct. 1, 1933, and the field has produced 385,979,691 bbl. of oil. The geology of the East Texas field has been discussed by Lahee,1 Levorsen,2 Minor and Hanna3 and others, and it will not be discussed in detail here. The field is a structure of the monocline type on the westward dipping homocline between the Sabine uplift and the East Texas geosyncline. Production is obtained from the Woodbine group, which has been truncated and then sealed by the Austin chalk, which rests unconformably upon it. The oil-saturated part of the sand lies bettween a sub-sea depth of 3050 ft. on the east side of the field, where the Woodbine sand stops and the Austin chalk rests directly upon older formations, and a sub-sea depth of 3320 ft., which was the average depth of the water table in the sand at the time the field was discovered. The field is about 40 miles long and has an average width of approximately 4 1/2 miles. The area within the proven limits of the field is close to 116,580 acres and the normal Woodbine water underlies nearly 62,000 acres on the western side of the field at the present time. The field is unusual in several respects: (1) the tremendous size of the reservoir system and the quantity of oil in place; (2) the large area of the oil and water contact, which makes water movement possible into the oil-bearing part of the structure; (3) the absence of free gas within the main producing sand of the field. Changes in the reservoir pressure during the production history of the field have been greatly affected by

Jan 1, 1934

By Tracy C. Jarrett

The alloying of various elements with gold to produce different colors is an old art, but the effect of each element or combination of elements is not generally known. Investigations have been made in this field by F. E. Carter,' E. M. Wise,2 and L. Sterner-Rainer.3 It is the intent of this paper to present in schematic diagrams the effects of various elements upon the color and the melting point of gold alloys. In this investigation 2-oz. melts made in a high-frequency inductiorl furnace were used for all tests. The melting points were determined by the use of a calibrated chromel-alumel thermocouple sealed in a thin-walled alundum tube. The couple was then submerged in the molten metal and the freezing and melting points were determined by using a Leeds and Northrup potentiometer. By checking several melts using copper, zinc and gold, it was found that the accuracy of determining the melting point was within ± 5" F. To determine the differences in colors and to classify them, a wet tissue paper was placed over the polished samples and examined under a uniform white light. The 2 by 45 by 0.045-in. samples were cut from 50 per cent cold-worked strip. The original ingot was 3 by % by % in. This visual comparison, although not scientifically exact, served as a quite satisfactory means for determining and classifying these differences. The base alloys, or "hardeners," were first made up and analyzed, after which the gold and silver were added. This method of making up the alloys was chosen so that the same base alloy could be used for the gold alloys of different karats. The first series consisted of gold, copper, zinc and nickel, the copper comprising from 85 to 65 per cent of the content of the "hardener" and the zinc and nickel replacing copper. The second scries consisted of gold, silver, copper, zinc and nickel, the copper comprising from 85 to 65 per cent of the content of the hardener with the silver, nickel and zinc replacing copper. There was no particular reason for choosing these combinations, except that they gave a color range from red-pink to white.

Jan 1, 1940

By Tracy C. Jarrett

The alloying of various elements with gold to produce different colors is an old art, but the effect of each element or combination of elements is not generally known. Investigations have been made in this field by F. E. Carter,' E. M. Wise,2 and L. Sterner-Rainer.3 It is the intent of this paper to present in schematic diagrams the effects of various elements upon the color and the melting point of gold alloys. In this investigation 2-oz. melts made in a high-frequency inductiorl furnace were used for all tests. The melting points were determined by the use of a calibrated chromel-alumel thermocouple sealed in a thin-walled alundum tube. The couple was then submerged in the molten metal and the freezing and melting points were determined by using a Leeds and Northrup potentiometer. By checking several melts using copper, zinc and gold, it was found that the accuracy of determining the melting point was within ± 5" F. To determine the differences in colors and to classify them, a wet tissue paper was placed over the polished samples and examined under a uniform white light. The 2 by 45 by 0.045-in. samples were cut from 50 per cent cold-worked strip. The original ingot was 3 by % by % in. This visual comparison, although not scientifically exact, served as a quite satisfactory means for determining and classifying these differences. The base alloys, or "hardeners," were first made up and analyzed, after which the gold and silver were added. This method of making up the alloys was chosen so that the same base alloy could be used for the gold alloys of different karats. The first series consisted of gold, copper, zinc and nickel, the copper comprising from 85 to 65 per cent of the content of the "hardener" and the zinc and nickel replacing copper. The second scries consisted of gold, silver, copper, zinc and nickel, the copper comprising from 85 to 65 per cent of the content of the hardener with the silver, nickel and zinc replacing copper. There was no particular reason for choosing these combinations, except that they gave a color range from red-pink to white.

Jan 1, 1940

By M. S. King

A series of cross-hole acoustic measurements have been performed in a columnar-jointed basaltic rock mass around an underground opening mined by the drill-and-blast method. The purposes of the test program were: to evaluate the rock mass characteristics around the opening; to determine the zone of blast damage; and to evaluate seismic methods for anomaly detection ahead of mining in this type of rock. The cross-hole measurements were made between four 76-mm diameter horizon- tal boreholes diamond-drilled 12 m into a wall of the underground opening. Repetitive pulses of compressional (P) and shear (S) waves of frequencies in the range 3 kHz-100 kHz were propagated from a transmitter sonde through the rock mass to a receiver sonde, both of which were clamped hydraulically to the borehole wall. After amplification the received P- and S-wave signals were digitized at the surface by a digital oscilloscope and stored on floppy discs. The results indicate considerable reductions in P- and S-wave velocities at distances less than 2 m from the face. Clearly these low values are associated with blast damage. Beyond 2 m, the velocities in a vertical direction indicate almost constant values. The velocities in the horizontal direction beyond 2 m appeared erratic, but showed a general tendency to increase as a function of distance from the face. Their maximum values remained, however, still lower in value than the corresponding velocities in the vertical direction. Near the face, the differences in velocities were considerably greater: with horizontal velocities considerably lower in value than those vertical. Results of the spectral analyses of the received signals indicated that Q-values were strongly influenced by the vertically- oriented sets of joints. Only for waves travelling in the vertical direction was the effect observed of the blast-damaged zone immediately around the opening. The acoustic data obtained are clearly indicative of an anisotropic jointed rock mass, with a greater intensity of jointing for travel paths in the horizontal than the vertical direction. The vertical, columnar joints are probably less tightly closed than those oriented in the horizontal plane.

Jan 1, 1984

By William A. Longacre

In a previous paper the author discussed the problem described by the title of this paper, outlining and reviewing the Gish-Rooney method, with comparison and brief analysis of the interpretation techniques of Roman2 and Tagg.3 Some aspects of the simple type of two-layer system were reviewed from various sources.4, 5, 6 The Two-layer Problem For the configuration shown in Fig. I, and for any electrode separation A, the SurfAce of earth p, DepthH i P2 Infinite depth Fig. i.—Two-Layer system. apparent resistivity is a function of the relative depth the overburden resistivity pl, and a factor K defined by the equation P2 + P1 where p, is the resistivity of the lower bed. Thus, by the known theory of electrical images, p = pi [1+ */(*-7)] where The Multilayer Problem As the number of isotropic, homogeneous, horizontal layers increases, the difficulties of interpretation multiply. The theory becomes much more involved, and in view of the state of our knowledge, the general problem is virtually impossible of exact solution. However, certain types of multilayer problems can be worked out in terms of two-layer theory. Humme1,7 Pirson,8 Tagg,3 Watson,9 and others have pointed out the possibility of building up approximations of multilayer resistivity curves with suitable combinations of two-layer curves. Many three-layer curves can be constructed in this way to a good degree of accuracy, and special types of four-layer curves can be approximated. It is very likely that as the number of layers increases, the method of combination will not give good approximations except in very special cases. In the analysis of actual field data, the author has found that many obviously multilayer curves can be solved partially with a good degree of accuracy, using the theory that thin adjacent beds may be considered as one layer or zone, and applying two-layer theory to the extremities of the field curve. Modified Tagg Method of Interpretation Tagg's second method, though superior to his first, necessitates a large number

Jan 1, 1946

By William A. Longacre

In a previous paper the author discussed the problem described by the title of this paper, outlining and reviewing the Gish-Rooney method, with comparison and brief analysis of the interpretation techniques of Roman2 and Tagg.3 Some aspects of the simple type of two-layer system were reviewed from various sources.4, 5, 6 The Two-layer Problem For the configuration shown in Fig. I, and for any electrode separation A, the SurfAce of earth p, DepthH i P2 Infinite depth Fig. i.—Two-Layer system. apparent resistivity is a function of the relative depth the overburden resistivity pl, and a factor K defined by the equation P2 + P1 where p, is the resistivity of the lower bed. Thus, by the known theory of electrical images, p = pi [1+ */(*-7)] where The Multilayer Problem As the number of isotropic, homogeneous, horizontal layers increases, the difficulties of interpretation multiply. The theory becomes much more involved, and in view of the state of our knowledge, the general problem is virtually impossible of exact solution. However, certain types of multilayer problems can be worked out in terms of two-layer theory. Humme1,7 Pirson,8 Tagg,3 Watson,9 and others have pointed out the possibility of building up approximations of multilayer resistivity curves with suitable combinations of two-layer curves. Many three-layer curves can be constructed in this way to a good degree of accuracy, and special types of four-layer curves can be approximated. It is very likely that as the number of layers increases, the method of combination will not give good approximations except in very special cases. In the analysis of actual field data, the author has found that many obviously multilayer curves can be solved partially with a good degree of accuracy, using the theory that thin adjacent beds may be considered as one layer or zone, and applying two-layer theory to the extremities of the field curve. Modified Tagg Method of Interpretation Tagg's second method, though superior to his first, necessitates a large number

Jan 1, 1946

By A. Lawley, H. W. Schadler

TWINNING has long been recognized as a possible mode of deformation in crystalline solids and has been studied in a wide variety of crystals.&apos; Recently, deformation markings which have the topographical characteristics of twins have been seen in tungsten" and the body-centered cubic alloys of tungsten and molybdenum with rhenium.3-7 These markings have been identified as twins because: 1) they are visible after polishing and etching;2,3 2) their formation is accompanied by an audible click and a drop in load;4 and 3) the habit plane is {112}, the plane which has been identified as the twinning plane for several body-centered cubic metals.&apos; However, there has been no published evidence for the specific determination of the twinning direction in rhenium alloys of tungsten and molybdenum, because usually the deformation twins were not broad enough to be detected with a conventional X-ray beam. Consequently, [111] is inferred as the twinning direction since the latter must lie in a plane of symmetry perpendicular to the twinning plane (112). As Sims and Jaffee3 and Lawley and Maddin4 have shown, the addition of rhenium to molybdenum and tungsten increases the ductility of the alloy over that of the pure metal, but twinning is much more profuse in these alloys than in the pure elements, particularly at Mo-35 pct Re*and W-30 pct Re. Since twinning is often associated with brittle fracture in iron8 and the silicon-irons,9 direct experimental proof that the deformation markings in tungsten and molybdenum alloys of rhenium are twins seemed to be needed. Using the Laue back-reflection technique, the deformation markings in a Mo-35 pct Re alloy are shown to be deformation twins. The twins have a (112) habit plane and the twinning direction is <111>. The Mo-35 pct Re specimen used was taken from a 0.060-in. zone-refined single crystal deformed 6 pct in tension at 78°K. The Laue back-reflection technique, with a film to specimen distance of 2 cm, and white radiation from a copper target were used.

Jan 1, 1962

By Lester C. Uren

With the depletion of our older, and relatively shallow, oilfields and the necessity for securing new production from deeper horizons, much attention is being given to the improvement of oil-well pumps in order that they may function satisfactorily under the more difficult conditions imposed by increased depth. Until recently, practically all of the world&apos;s petroleum was secured from wells less than 3000 ft. deep, whereas horizons are now being explored to depths of from 5000 to 7000 ft. in some of the more prolific fields, and it seems probable that the greater part of the future supply must come from depths in excess of 3000 ft. While much of the early production in a new field is obtained by natural-flow methods, when the stimulus of high gas pressure fails, recourse must be had to some method of pumping. The perfection of a pump capable of economically and efficiently lifting oil from depths ranging from 3000 to 7000 ft. is therefore a matter of prime importance to the oil-producing industry. This paper is offered as an estimate of the present state of development of the oil-well plunger pump and as a review of the general principles involved in its operation in deep-well pumping. A design for a new type of oil-well pump embodying several novel features, is also described. Essential Parts of Oil-well Plungeb Pump The pump commonly used in lifting oil from wells in American practice is of the simple displacement type, in which a plunger equipped with a working, or traveling, valoe is given a vertical reciprocating motion in a stationary working barrel. The latter is suspended from the surface by tubing, submerged in the well fluid, and is equipped at its lower end with a stationary standing valve; Figs. 1 and 2 illustrate two common types of oil-well pumps. The simple cup-leather packed plunger of Pig. 1 has its counterpart in the long, hollow, cylindrical, polished steel plunger of Fig. 2; otherwise the two types are identical in the form and arrangement of their essential parts. Fig. 2 shows the additional feature of a "garbutt

Jan 1, 1927

By Albert F. Schneider

The peculiar conditions under which lead and silver ores are now smelted in Salt Lake Valley, Utah, render it advantageous to make slags that are siliceous and carry a high percentage of lime. The ores treated come from Utah, Idaho, Montana, and Nevada; nine-tenths coming from Utah. These ores are siliceous, and contain but little fluxing material; the iron present scarcely sufficing for the sulphur and arsenic. Formerly ores high in iron were furnished from Cottonwood Canons, but this supply is meagre. The ores from Idaho, Montana, and Nevada are high grade galenas, more or less impure. They generally require a large amount of iron for the sulphur, arsenic, and antimony. In the winter and spring of 1880—&apos;81, we were treating at the Germania Works principally Bingham Canon lead ores and silver ores from Tintic. The former contained 15 to 30 per cent. silica, and only 4 to 5 per cent. iron (generally as iron pyrites); they ranged high in lead and low in silver, and carried more or less alumina; the lead was present chiefly as carbonate. The silver ores from Tintic contained sulphides, and ran as high as 80 per cent. silica. We had been running on a slag approximating 40 per cent. FeO, 20 per cent. CaO, 10 per cent. other bases, and 30 per cent. SiO2, which had heretofore been very satisfactory; but with the class of ores then coming in it was of the utmost advantage to use less iron and more lime, especially as the iron ore (50-55 per cent. iron and 5-7 per cent. silica) cost four times as much as the limestone (50-55 per cent. lime, 3-5 per cent. silica). The large amount of alumina in the slag influenced them for the worse; the addition of lime to the charge helped them, and after many experiments regarding the proportion of FeO, CaO, and SiO2, a slag approximating 35 per cent. FeO, 25 per cent. CaO, 5 per cent. other bases, and 35 per cent. SiO2 seemed to answer

Jan 1, 1883

By George Hallerman, R. J. Gray

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

Jan 1, 1964

By R. G. Davies

Isothermal annealing of quenched Fe3Al reveals that the superlattice forms by the nucleation and growth of ordered domains. The activation energy for isothermal ordering and initial domain growth is -29 keal per mole, which is thought to he the activation energy for vacancy migration. Domain growth, in the absence of excess vacancies, has an activation energy of -100 keal per mole. A maximum in the hardness is observed when the structure consists Of ordered domains, -35-4 in size, growing into a short-range ordered matrix and, also as a function of degree of order, S, with an infinite domain size at S = 0.4 to 0.5. It is proposed that both maxima are due to a transition from deformation by unit dislocations to deformation by superdislocntions. FE-AL alloys containing more than -23 at. pet Al, when quenched from above the critical temperature for the Fe3A1 type of order, always contain the maximum possible amount of FeAl (B2) type of order&apos; (see Fig. 1). Thus when the Fe3A1 superlattice forms, in a 25 at, pet A1 alloy, it does so from an imperfect FeAl structure. The formation of the Fe3Al superlattice has been the subject of several recent X-ray,1, 2 electrical-resistivity,3"6 and dilatometric3 investigations. McQueen and Kuczynski3 concluded that the isotherma1 ordering of Fe3Al, after quenching from 800°C (T,, the critical temperature for order, is 55O°C), takes place by the nucleation and growth of ordered domains. However, Feder and Cahn4 found that the isothermal ordering was complex but more like a homogeneous nucleation process than a nucleation and growth process. Lawley and Cahn2 reported that the degree of order is a continuous function of temperature which is a characteristic of a homogeneous nucleation process. Thus, the evidence is conflicting as to the nature of the Fe3Al ordering reaction. Lipson7 was the first to suggest that ordered domains should exist in the Fe3A1 structure since, as

Jan 1, 1964

By S. M. Runke, R. G. Meara, O&apos

The Bureau of Mines has been charged by Congress to investigate processes for the production of alumina from low-grade bauxite, alunite, and clay. As one part of the program, an investigation of the application of ore-dressing methods to improve the grade of high-silica bauxite is in progress at the Mississippi Valley Experiment Station at Rolla, Mo. This paper summarizes data obtained so far and presents detailcd results of tests on four typical samples. Mineralogy of Batjxite The name bauxite originally was used to designate the dihydrous aluminum oxide (A1203.2HzO). The designation has been retained, although the existence of a specific mineral of such composition has been disproved. The term is now applied to ores of aluminum consisting of various mixtures of the minerals gibbsite (AlzOa.3H20), diaspore (A120a.H20), and boehmite (Alr-03.H20). The predominant hydrous aluminum oxide in most American bauxite, however, is gibbsite. In some instances bauxite may be amorphous mixtures of the hydrous aluminum oxides that approximate the composition of dihydrous aluminum oxide (A1203.2Hz0). The proposed name for this material is cliachite. Gibbsite and boehmite, the trihydrate and monohydrate, are soluble in a solution of sodium hydroxide at elevated temperature and pressure, whereas diaspore is practically insoluble. The solubility of these two minerals is the basis of the Bayer process of alumina extraction. All bauxites contain certain impurities, the commonest of which, in the order of their importance, are: silica, principally as a constituent of kaolinite, and to a lesser extent as quartz; iron, as hematite, limonite, and siderite; and titanium, as ilmenite, rutile and leucoxene. Minor impurities are zircon, cobalt and nickel. Bauxite is produced commercially in Arkansas, Alabama, Mississippi, Georgia and Tennessee, but the most important deposits in the United States are in Arkansas, in the vicinity of Little Rock. History of Batjxite Beneficiatjon The literature on bauxite beneficiation is limited, but the reports of Gandrud and DeVaneyl and Clemmer, Clemmons, and Stacy2 show the possibilities of flotation as a means of beneficiating bauxite. Their work has also developed reagent combinations that are satisfactory for flotation of gibbsite.

Jan 1, 1944

By Henry M. Howe

The data which are collected in Table 1 show that the ferrite of low-carbon steel and of electrolytic iron, like the network of hypo- and hyper-eutectoid carbon steel, inherits, either absolutely or relatively, the grain size of the mother austenite from which it is born in cooling through the transformation range. This evidence is so abundant and concordant as to cast doubt on Prof. Jeffries&apos;l hypothesis of what might be called reversed inheritance, by which he explains Mr. Ruder&apos;s observation2 that a grain in a "slug of pressed pure electrolytic iron powder" was coarser, perhaps 1,500,000p2, aftcr a 3-hr. exposure to 1000" C. than after a 3-hr. exposure to 1250-1300°, when the grain size was about 35,000µ2. His explanation implies a natural tendency of coarser austenite grains to yield finer ferrite ones than spring from finer austenite grains, so that the inheritance is reversed. What seems to me a simpler explanation is that the enormous grains which followed the 1000" heating were not inherited from the mother austenite, but were formed by the process of natal coarsening, by means of which Stead and Carpenter developed grains of this same order of magnitude in this same kind of material, on heating to 950" or to 1000°, the temperature used by Mr. Ruder, provided the exposure was not unduly prolonged, and it does not seem to have been in Mr. Ruder&apos;s case. That their coarsening was natal and not through inheritance is shown first by the fact that their grain coarseness was out of all proportion to their relatively low temperatures and short periods, and hence was very far in excess of the grain size which the mother austenite must have had, and second and more cogently by the fact that the shape of these coarsened grains was evidently determined by the temperature distribution which existed during and immediately after the Ar3 transformation, that during the passage from the gamma to the non-gamma state. In discussing this subject, we must remember that coarse ferrite grains, whether those formed in cooling from the molten or those induced by

Jan 1, 1918

By S. D. Michaelson, Eric Sinkinson

Many of the magnesite ores of the western part of the United States contain such large amounts of silica and hydrous silicate minerals that the value of the ores is either low or nominal. Expensive and carefully controlled mining methods are necessary to prevent excessive dilution of the higher grade ores by introduction in mining of small pieces of the hanging walls or footwalls of the deposit. This difficulty is further complicated by the various states of decomposition of the country rock of the deposits in which many of the ores occur. The problem the authors attempted to solve arose from a request to float an impure magnesite containing varying proportions of siliceous gangue with calcium carbonate. The ore is normally enclosed in serpentine masses, somewhat decomposed, and in mining it wall rock is incidentally added, so that variable amounts of siliceous material occur in the samples. The silica, alumina, and iron oxide are so closely associated with the magnesium carbonate in the magnesite that ordinary mechanical separation at coarse mesh sizes is of no avail. It is well known that calcium carbonate can be floated by suitable reagents, therefore it seemed reasonable to suppose that magnesium carbonate minerals would behave in a similar manner, but experimental trial proved that this supposition was unfounded. Therefore the first step in the problem was to find out what differences of behavior there were between magnesium and calcium carbonates under flotation conditions, or when suspended in water. In water at 18" C. magnesium carbonate is slightly more soluble than calcium carbonate; in fact, MgCO3 is soluble to the extent of 0.0106 grams in 100 c.c. of water at 18" C. and CaCO3 to the extent of 0.0013 grams. However, magnesium carbonate in water gradually changes to the basic carbonates of a composition (3MgCO3.Mg(OH)23H2O) or (4MgCO3.Mg(OH)25H2O), depending upon conditions, and calcium carbonate to calcium hydroxide, Ca(OH)2. The relative solubilities of these hydroxides in water are the reverse of the solubilities of magnesium and calcium carbonates. The range in published figures for solubility

Jan 1, 1938

By S. D. Michaelson, Eric Sinkinson

Many of the magnesite ores of the western part of the United States contain such large amounts of silica and hydrous silicate minerals that the value of the ores is either low or nominal. Expensive and carefully controlled mining methods are necessary to prevent excessive dilution of the higher grade ores by introduction in mining of small pieces of the hanging walls or footwalls of the deposit. This difficulty is further complicated by the various states of decomposition of the country rock of the deposits in which many of the ores occur. The problem the authors attempted to solve arose from a request to float an impure magnesite containing varying proportions of siliceous gangue with calcium carbonate. The ore is normally enclosed in serpentine masses, somewhat decomposed, and in mining it wall rock is incidentally added, so that variable amounts of siliceous material occur in the samples. The silica, alumina, and iron oxide are so closely associated with the magnesium carbonate in the magnesite that ordinary mechanical separation at coarse mesh sizes is of no avail. It is well known that calcium carbonate can be floated by suitable reagents, therefore it seemed reasonable to suppose that magnesium carbonate minerals would behave in a similar manner, but experimental trial proved that this supposition was unfounded. Therefore the first step in the problem was to find out what differences of behavior there were between magnesium and calcium carbonates under flotation conditions, or when suspended in water. In water at 18" C. magnesium carbonate is slightly more soluble than calcium carbonate; in fact, MgCO3 is soluble to the extent of 0.0106 grams in 100 c.c. of water at 18" C. and CaCO3 to the extent of 0.0013 grams. However, magnesium carbonate in water gradually changes to the basic carbonates of a composition (3MgCO3.Mg(OH)23H2O) or (4MgCO3.Mg(OH)25H2O), depending upon conditions, and calcium carbonate to calcium hydroxide, Ca(OH)2. The relative solubilities of these hydroxides in water are the reverse of the solubilities of magnesium and calcium carbonates. The range in published figures for solubility

Jan 1, 1938

By Tracy Jarrett

IN making gold alloys possessing certain physical properties, such important factors as corrosion resistance, color, hardness and melting points must be considered. All of these requirements depend directly upon the composition. It is possible to obtain the same colored gold alloy by using different compositions, but in doing so one may bring in some undesirable property. Other investigations have been carried on in this field by F. E. Carter,1 E. M. Wise,2 and L. Sterner-Rainer.3 To make a complete study of the effect of composition upon these properties, a systematic investigation was carried on involving a range of copper content from 85 to 65 per cent. Elements such as zinc, silver and nickel were used to replace in part the copper content. The gold content in all the alloys remained constant. Only 10-karat gold alloys of those containing 41.6 per cent gold will be considered. All of the alloys were made in an induction furnace. Each alloy was cast in a 3 by ¼ by ¾ -in. ingot. The method of obtaining the melting points and making color determinations was described in a previous paper.4 The Rockwell B scale with the ball and 100-kg. weight was used for all hardness determinations. The submersion of test pieces in concentrated nitric acid is one of the standard corrosion tests used in the optical trade. A test piece in the 50 per cent cold-worked condition, ½ by 2 by 0.043 in., is blanked from a strip using a. die, and the weight, loss per square inch of surface is taken as a means of comparison. The time for this test is 2 ½ hr. of actual sub-mersion of the test piece in the acid. This standard test was applied to all of the 10-karat gold alloys discussed in this paper. The tensile tests were made upon strips of the dimensions shown in Fig. 1. The test pieces after blanking were annealed at 1300° F. for 20 min. and cooled in air. The "drop of the beam" method was used in determining the yield point, as there was a very marked "drop" when the yield point was reached.

Jan 1, 1939

Victor G. Hills, Cripple Creek, Colo. (communication to the Secretary): In continuation of the subject of the perform ance of "baby machine-drills," presented by Mr. Thane, I sub mit the following records of work done with these drills in the Cripple Creek district of Colorado. Two years ago, the Anchoria-Leland mine began to use baby drills ; and, to make the experiment more complete, began by purchasing two machines, of the same size, but of different make. The little drills were first used for stoping and up raising, in which they achieved at once an unqualified success. Soon after, they began to be used for the smaller branch-drifts and prospecting cross-cuts, while the large two-man drills were still used for the main drifts. Now they have almost entirely superseded the large drills, since it has been found that they will do any ordinary work in the mine at less cost, both for labor and for powder, per ton of rock broken. The large drills, of course, make more rapid progress; but it is only where time is a specially important factor that they are now used. The Portland mine, where, until within a year, only the large machines were used, is now using some small drills for stoping, and also for drifting. Mr. Thane speaks of having two men to operate a baby-drill; but in this district the baby-machine is always worked by one man without help. Again, in Prof. Christy&apos;s postscript, the quoted extract from a letter of Mr. L. T. Seymour, the South African engineer, mentions a " 2 1/2-inch Little Giant," as though that were the smallest machine used in that region. These statements leave some doubt as to just what Mr. Thane means by a " baby-drill." To avoid any such uncertainty as to the present communication, I will say that the large or two-man drill in common use at Cripple Creek has a 3 1/8-inch cylinder; while a few mines employ a 3-inch, and a few, in running large tunnels, a 3 1/2-inch drill. What we call a baby-drill here has a

Jan 1, 1900