Search Documents

By K. H. G. Ashbee, J. W. Heavens

One consequence of the distribution in orientation of Bragg diffracting planes in an elastically bent foil is that simultaneous diffraction occurs from ±g pairs, where g is the reciprocal lattice vector to a diffracting plane. If such Bragg contour pairs are indexed, then the variation in orientation with respect to the incident electron beam is known. This note describes a construction by means of which Bragg contour pairs may be indexed by inspection. Referring to Fig. 1, the Ewald sphere radius is l/h, where is the wavelength of the electron beam, and the half spacing of first-order reciprocal lattice planes is l/d, where d is the corresponding spacing in direct space. The angle subtended by the zero and first-order planes at the center of the Ewald sphere is a = sin-' Thus, to represent a pair of first-order Bragg contours on a stereographic projection, measure ±a from, and along the normal to, the zero-order plane. The traces of the required Bragg contours pass through these points and parallel to the zero-order trace. In practice, it is desirable to enlarge a stereographic projection of the zero-order planes before making the construction. As an example, a stereographic projection of first-order Bragg contours up to line 27 for an fcc crystal is given in Fig. 2; if required, higher-order contours can easily be added. Fig. 2 is, of course, a map of first-order Brillouin zone boundaries. One use of this construction is the measurement of large elastic fields in electron microscope specimens. Fig. 3(a) shows a pattern of Bragg contour pairs due to lattice distortions near a large precipitate. This particular example is of a T-phase precipitate in Hidu-minium 54 (A1 + 6 wt pct Cu, 0.5 wt pct Mn). Foil buckling is produced by annealing during observation and may be evidence for evaporation from the precipitate.' Comparing Figs. 2 and 3(0), it is evident that the axis of high symmetry in Fig. 3(a) is [lll]. The strain in a bent foil is approxinlately t/2r, where / is the foil thickness and ? the radius to which the foil is bent. From the projections of grain boundaries and of helical dislocations, it was estimated that ( - 3000A, and values for ? were obtained from the

Jan 1, 1968

By R. L. Stone

None of the currently used methods of testing bentonites as binders for strengthening iron ore pellets is entirely adequate by itself. Since more knowledge was needed about 1) which properties of bentonite most affect pellet strength, and 2) the precise mechanism by which strengthening is produced, attention was paid to possible new techniques for rating bentonites. With the structural nature of bentonites — in particular, the montmorillonite component — the possibility of rating bentonites on the basis of zeta potential was investigated. These bentonites were also rated by conventional tests and measurements, including colloid content, barrel yield, pH, chemical analysis and physical tests on green and dry pellets. A mechanism for pellet bonding based on electro-kinetic forces between the bentonite and the iron ore concentrate appears to be feasible. In pelletizing, from 6 to 18 lbs of bentonite is added per ton of concentrate to give strength to the green and dry pellets. In some operations even more bentonite than is required for strengthening purposes must be added for moisture adsorption to pennit balling of the concentrate. Since bentonite is thus a major item in pelletizing, more knowledge about the way in which bentonites act as binders and better ways of rating this ability would help in the difficult job of selecting the right bentonite for a given concentrate. The fact of the matter is that although several methods are in current use for testing bentonites, none of these methods are consistently foolproof. For example, a given bentonite may rate high by several standard tests yet turn out to be a poor binder, and of course the reverse also occurs. Actually, more knowledge is needed about 1) which properties of bentonite most affect pellet strength, and 2) the precise mechanism by which strengthening is produced. In this study attention is therefore paid to possible new techniques for rating bentonites. With the structural nature of bentonites as a starting point, we investigated the possibility of rating bentonites on the basis of the zeta potential, i.e., the electrokinetic ootential on the montmorillonite colloids — the main component of bentonite binders. The zeta potential technique was applied to a range of commercial bentonites from several areas in the U.S. and abroad. These bentonites were also rated by conventional tests and measurements, including:

Jan 1, 1968

By Will Mitchell, T. G. Kirkland, C. L. Sollenberger

R. S. Handy (Santa Rosa, Calif.)—It would be interesting to learn the comparative results of treating the Korean scheelite ore described in this paper according to the following procedure: I—Follow the procedure described in the paper to the recovery of the sulphides by flotation. 2—Dilute the residue from the sulphide flotation strongly with water and disperse the contained colloids by adding a mixture of 75 pct sodium silicate and 25 pct quebracho to dispersion point. 3— Settle the dispersed pulp and decant the supernatant colloids. 4—-Dilute, settle, and decant the pulp until the settled residue is crystalline. Not over 10 pct of the tungsten minerals should follow the colloids. 5—Treat the settled residue by flotation, having established the proper pH. Oleic acid homogenized with cresylic acid or kerosene is more selective for scheelite than is oleic acid alone. (The recovery of the contained tungsten minerals should be practically complete in this operation.) 6—Deflocculate the tungsten concentrate from step 5 with the same dispersion agents as in step 2 and treat the deflocculated pulp by gravity. The minerals that tend to float with scheelite are generally of low specific gravity and the separation is efficient. The heavier contaminants, such as pyrrhotite and magnetite can be removed magnetically, leaving a practically pure scheelite. E. J. Pryor (Imperial College of Science and Technology, London)—It occurred to me that instead of using temperature as a differentiating control, more precision might be obtained with a reagent of a type we developed here for the flotation of high grade fluorspar in cold pulps. This reagent, which is manufactured on a modest scale in England, is based on oleic acid, which has been modified by our patented process to ensure complete stable dispersion at any desired concentration in water. It thus becomes possible to utilise unimolecular layers with good selectivity. In the fluorspar flotation for which we developed it, it is possible to hold a tight control on depressing quebracho for the calcite without substantial loss of flu-orite, and recovery exceeding 99 pct is not uncommon in the mill where it is in use, even under wintry conditions. No attempt has been made yet to extend the use of the reagent, as we have not completely overcome

Jan 1, 1952

Discussion of the paper of DWIGHT T. FARNHAM, presented at the Pittsburgh meeting, October, 1914, and printed in Bulletin No. 93, September, 1914, pp. 2357 to 2364. DAVID T. DAY, Washington, D. C.-Do you know anything about the character of that clay as to organic matter? H. RIES, Ithaca, N. Y.-No; it is a dark brownish clay, sandy in its nature. The brownish coloring is probably due to organic matter. Some lignite is also present. DONALD W. Ross.*-I have worked at the plant under consideration. I have not seen Mr. Farnham's paper; but in answering the question as to the organic matter, I might say there is practically no organic material scattered through the shale. There are, however, several layers of carbonaceous shale and rather low-grade coal interbedded with the formation. There are two very serious drawbacks-one which threatens to shut down the plant and another which merely means the expenditure of money. The first is taking care of the sediment from the washing away of the overburden. The government is doing extensive work at different points about Lake Washington with a view to creating a fresh-water harbor for Seattle. I understand that they keep at the Denny-Renton people to keep the channel of Cedar River clear. The Denny-Renton Co. can hardly help filling up the channel so long as they continue their hydraulic work, so this is probably one of their most serious problems. The other is this: There is a large percentage of what I should call micaceous shale or sandstone-a sandstone which contains a large amount of light-colored mica. Of course only a limited amount of this can be used in the manufacture of paving brick. As they shoot down the bank after the overburden of gravel and loam is washed away, these large boulders of micaceous sandstone come down. The strata have apparently been crushed where the clay pit is located so that the exact formation cannot be readily determined. These pieces of sandstone, 5 or 6 ft. in diameter, have to be blasted and removed from the shale. They bother both in the open pit and in the tunnel mining. In the tunnel mining of the shale blocks frequently cover the holes in the roof of the tunnel through which the shale is loaded into cars.

Jan 4, 1915

Discussion of the paper of S. E. Bretherton, presented at the Butte meeting, August, 1913, and printed in Bulletin No. 80, August, 1913, pp. 1481 to 1487. S. E., BRETHERTON, San Francisco, Cal.:-Since preparing my paper, our chemist, F. L. Wilson, has been experimenting with Leadville, Colo., oxidized zinc ore and Leadville zinc sulphides containing lead, operating upon 40-1b. lots at a time. His results on Leadville sulphides are as follows: The raw ore contained a trace of gold, 5.04 oz. of silver, 19.1 per cent of zinc, and 7.24 per cent of lead. After roasting the ore contained a trace of gold, 5.72 oz. of silver, 0.75 per cent of copper, 21.7 per cent of zinc, and 8.29 per cent of lead. The loss in weight by leaching was 38.8 per cent. The extraction was 42.8 per cent of the copper, 80.6 per cent of the zinc, 7.1 per cent of the lead, 0.64 per cent of the silver, and no gold. The little .silver that is extracted would be thrown down with the copper when precipitating it from the zinc and both thrown hack into the residue to be smelted. There would be no trouble in smelting the residue with nearly all the sulphur eliminated and containing less than 7 per cent. of zinc. On zinc carbonates containing silicates the results are not satisfactory. H. O. HOFMAN, Boston, Mass. (communication to the Secretary*) :¬The paper by Mr. Bretherton upon the application of ammonia and carbonic acid to the recovery of zinc as oxide from roasted sulphide ore is of interest to me, as the first installation of the Schnabel process for the extraction of zinc from a mixture of zinc oxide, lead oxide (with some cupric oxide), and pellets of enriched lead, produced in steaming liquated zinc-silver-lead crust of the Parkes process, was made at Lautenthal, Harz mountains, where I was chemist. In that capacity I carried out numerous experiments on the Schnabel process, was active in the erecting of the plant, and later had charge of it. After the Lautenthal plant had been in operation for some time a similar one was built at Hoboken-les-Anvers, but both have been abandoned, as the wet process could not compete with the distillation of the liquated zinc-silver-lead crust, now used universally in the Parkes process.

Jan 11, 1913

By R. Kerby, T. R. lngraham

The rates of cadmiuln cementation from buffered solutions were studied on both the cylindrical and circular faces of a rotating zinc disk. The activation energies are equivalent on both surfaces, but the rate is more rapid on the cylindrical face. At higher temperatures and at pH values above 6.4, the rate of deposition increases because of an increase in the cathodic area of the deposit. The rate may also be increased by decreasing the thickness of the diffusion layer by rapid stirring. The presence of small amounts of copper, cadmium, lead, iron, or aluminum in the zinc does not affect the cementation rate, but when srnall amounts of copper, cobalt, and arsenic were present in the solution cadmium deposition ceased shortly after it started. Small amounts of copper in solution become cemented with the cadmium to form a coarse deposit of Cd3Cu. When zinc ores containing cadmium are processed for electrolysis, the cadmium appears with the zinc in the leach liquors. Because of the discharge potential of the cadmium ion and the hydrogen overvoltage on metallic cadmium, the cadmium ion must be removed prior to zinc electrolysis to prevent its codeposition. Cadmium is usually removed from acidic zinc sulfate solutions by cementation on zinc. When zinc sheets are used with the appropriate conditions of pH and temperature, a finely divided, high-purity cadmium powder is obtained; it floats to the surface with attached hydrogen bubbles and, after careful washing, may be processed directly to a marketable product.' The reaction on zinc sheets is relatively slow because of the limited amount of exposed cathodic area on the sheets. A much more rapid reaction is obtained when zinc powders are stirred into the solution, but this procedure does have a potential disadvantage: some unreacted zinc may be trapped in the cemented cadmium and thus lower its grade.1 The equilibrium constant at 25°C for the displacement of cadmium by zinc is of the order of lo", which indicates that at equilibrium the displacement would be essentially quantitative and no back reaction need be considered. This indication is not entirely true, however, because in the presence of oxygen any loose cadmium which is out of contact with metallic zinc tends to redissolve after cementation.' The overall effect is much the same as that to be expected if the equilibrium constant were much smaller. Previous experimental work on cementation reac- tions3 is in general agreement that the rates of cementation usually follow first-order kinetics. The metal on which cementation occurs is considered to consist of anodic areas from which metal dissolves and cathodic areas onto which the reactive metal is cemented. For the reaction to continue, the cemented deposit must remain open and porous for the removal of ions. Usually, the deposited metal influences the rate of cementation; when it blocks the pores in the deposit, the rate of cementation will be decreased. Alternatively, when the cemented metal grows as den-drites or as coarse powder the cathodic area is correspondingly increased and the rate of cementation increases,3 Thus, it is only during the initial stages of cementation, prior to the development of deposit effects, that the kinetic behavior of the reaction may be studied without ambiguity. In this paper, experiments will be described for cementation of cadmium from dilute solutions onto the surface of a rapidly spinning zinc cylinder. The effects of ionic concentration, disk rotation speed, temperature, and impurities will be described. APPARATUS AND PROCEDURE The apparatus used for the experiments was described in a previous paper.4 It consisted of a 2-liter vessel in which the contents were protected, against oxidation, by a stream of prepurified nitrogen. The vessel was immersed in a water bath which controlled

Jan 1, 1970

By W. Bonfield

The microstrain characteristics of a polycrystal-line Cu 1.9 wt pet Be precipitation-hardening alloy have been determined for various conditions of aging. The friction stress remained constant for all the conditions investigated, whereas the microscopic yield stress (the stress to produce a plastic strain of 2 x 10-8 in. per in.) and the three-stage stress-strain curve in the microstrain region were sensitive to changes in dislocation and precipitate distribution. Correlations between the measurements of microplasticity and electron-nzicroscope observations of substructure are considered. ALTHOUGH the macroscopic mechanical properties of Cu 1.5 to 2.0 wt pet Be precipitation-harden ing alloys were established' in some detail, there has been no previous investigation of the nature of microyield-ing in these alloys. This paper describes a high-sensitivity extensometer determination of microplasticity in polycrystalline Cu 1.9 wt pet Be, in which the friction stress, the microscopic yield stress (the stress to produce a plastic strain of 2 x 10-6 in. per in.), and the rate of strain hardening in the micro-strain region were measured for various conditions of precipitation. The structural changes accompanying aging in this alloy were examined using transmission electron microscopy, a study which differed from previous investigations as, in order to minimize grain boundary precipitation effects,' the solution-treated alloy was cold-rolled to 40 pet reduction prior to aging. Hence the extent of recovery and recrystalliza-tion, as well as the variation of precipitate morphology and distribution, were assessed. From these results possible correlations between the microstrain characteristics and the observed precipitate and dislocation structure are considered. EXPERIMENTAL PROCEDURE The material investigated was a commercial copper beryllium alloy (Berylco 25), which had a com- position of 1.9 wt pet Be and 0.2 wt pet Co. The alloy was solution-treated at 800°C, quenched in water, and then cold-rolled to 40 pct reduction. Tensile specimens of gage length 1 in. and rectangular cross section of 0.18 by 0.06 in. were prepared from the solution-treated, cold-rolled material and aged for 15 min, 2, 24, and 100 hr at 315°C and 24 hr at 425°C to produce a range of precipitate structure. The hardness values associated with these conditions are listed in Table I. It can be seen that a maximum value is obtained after 2 hr at 315oC, which decreases with continued time at temperature to a minimum after 24 hr at 425°C. For comparison some as-solution-treated specimens were also aged for 2 hr at 315°C. The specimens heat-treated to a given condition were examined in two ways. First, the nature and distribution of the precipitate and dislocation structure was characterized using transmission electron microscopy. Thin foils were obtained from the specimens by electrolytic polishing in a 30 pet nitric acid-alcohol solution at -20oC, and were examined in an RCA EMU 3 electron microscope. Second, the mi-croplastic behavior of the specimens was measured with a Tuckerman strain gage, using the load-unload technique previously described2, 3 to determine the friction stress, the microscopic yield stress, and the variation of plastic microstrain with stress. RESULTS 1) Structural Changes During Aging. a) Annealing Processes. The solution-treated, cold-rolled Cu 1.9 wt pet Be had an irregular dislocation-cell structure,

Jan 1, 1968

By Randolph C. Specht

A two year study was made of the waste disposal of the pebble rock phosphate industry. Solid slimes are impounded in large settling areas and the process water is re-used. Clear effluent was not found to be toxic to fish or animal life in field tests or in controlled experiments. Survey: The pebble rock phosphate mining and washing operations in Florida (fig. 1) are along the river basins of the Alafia to the west and the Peace to the east. The elevation of the area varies between 40 and 170 ft above sea level. Effluents from the operations find their way into one of the two river systems (fig. 2), the Peace River which flows into Charlotte Harbor and the Alafia into Tampa Bay, both along the Gulf of Mexico. There are no major industries along these rivers below the phosphate operations. On the Peace River, the town of Arcadia, approximately 50 miles below the phosphate operations, obtains its water from the river. No other communities along the rivers use them as a source of water supply. Small communities, farms, and ranches are located along the rivers and both rivers drain vast swamp areas. Complaints had been received at the office of the Chief Sanitary Engineer, of the Florida State Board of Health,' that both rivers were turbid at various times and that fishing in the Alafia River was "not as good as it used to be." Tests made by another agency on the dissolved oxygen content of the Alafia River revealed that the oxygen content, at times, was comparatively low.= However, it was not shown that the phosphate wastes had any effect upon the oxygen content of the stream. The river waters are normally brown in color due to drainage from vast swamp areas and are very shallow, from 2 to 6 ft in depth. Turbid waters have been noted in streams coming from the present phosphate operations and also from streams along which there are no operations at the present time. It was learned from "old timers" that, when many more companies than at present were operating along both the Alafia and Peace Rivers forty or fifty years ago, no attention was paid to prohibiting the disposal of slimes along the river basins. During dry periods now in some of the river swamps where drainage ditches have been dug, it is indicated clearly that phosphate slimes were disposed of directly into the river swamps for many years past. Places have been observed where there were alternating strata of phosphate mud, leaf mold, and quartz sand. The former practice of indiscriminate disposal of wastes accounts for some turbidity, particularly after heavy rains and washouts and during clearing of land and digging of drainage ditches. During a six months' period in which a large tract of land was being cleared and drainage ditches dug, a small stream (Six Mile Creek), which previously had been clear, showed a turbidity of 600 ppm and remained turbid until the clearing was completed; after which the stream again flowed clear. An interview with the operator of the municipal water plant, which is about 50 miles below the phosphate operations on the Peace River and which used this river as a source of supply, revealed that there had been no taste in the water for the past ten years, other than that occasionally encountered from increased growth of algae. The operations of each of the cooperating com-

Jan 1, 1951

By Randolph C. Specht

A two year study was made of the waste disposal of the pebble rock phosphate industry. Solid slimes are impounded in large settling areas and the process water is re-used. Clear effluent was not found to be toxic to fish or animal life in field tests or in controlled experiments. Survey: The pebble rock phosphate mining and washing operations in Florida (fig. 1) are along the river basins of the Alafia to the west and the Peace to the east. The elevation of the area varies between 40 and 170 ft above sea level. Effluents from the operations find their way into one of the two river systems (fig. 2), the Peace River which flows into Charlotte Harbor and the Alafia into Tampa Bay, both along the Gulf of Mexico. There are no major industries along these rivers below the phosphate operations. On the Peace River, the town of Arcadia, approximately 50 miles below the phosphate operations, obtains its water from the river. No other communities along the rivers use them as a source of water supply. Small communities, farms, and ranches are located along the rivers and both rivers drain vast swamp areas. Complaints had been received at the office of the Chief Sanitary Engineer, of the Florida State Board of Health,' that both rivers were turbid at various times and that fishing in the Alafia River was "not as good as it used to be." Tests made by another agency on the dissolved oxygen content of the Alafia River revealed that the oxygen content, at times, was comparatively low.= However, it was not shown that the phosphate wastes had any effect upon the oxygen content of the stream. The river waters are normally brown in color due to drainage from vast swamp areas and are very shallow, from 2 to 6 ft in depth. Turbid waters have been noted in streams coming from the present phosphate operations and also from streams along which there are no operations at the present time. It was learned from "old timers" that, when many more companies than at present were operating along both the Alafia and Peace Rivers forty or fifty years ago, no attention was paid to prohibiting the disposal of slimes along the river basins. During dry periods now in some of the river swamps where drainage ditches have been dug, it is indicated clearly that phosphate slimes were disposed of directly into the river swamps for many years past. Places have been observed where there were alternating strata of phosphate mud, leaf mold, and quartz sand. The former practice of indiscriminate disposal of wastes accounts for some turbidity, particularly after heavy rains and washouts and during clearing of land and digging of drainage ditches. During a six months' period in which a large tract of land was being cleared and drainage ditches dug, a small stream (Six Mile Creek), which previously had been clear, showed a turbidity of 600 ppm and remained turbid until the clearing was completed; after which the stream again flowed clear. An interview with the operator of the municipal water plant, which is about 50 miles below the phosphate operations on the Peace River and which used this river as a source of supply, revealed that there had been no taste in the water for the past ten years, other than that occasionally encountered from increased growth of algae. The operations of each of the cooperating com-

Jan 1, 1951

By O. D. Sherby, J. E. Dorn

For elevated temperature-constant load creep tests of a solid solution alloys, the creep strain is a function of a temperature-compensated time parameter 0 = je H/RT dt. The activation energy H is equal to o constant of about 36,000 cal per mol. The substructures resulting from a given creep stress condition are functions of the creep strain independent of temperature. Each new creep stress gives a new unique set of grain substructures; this is one of the factors responsible for the failure of the mechanical equation of state for creep. IN this report an attempt is made to correlate the creep properties of dilute a: solid solutions in aluminum with the subgrain structures that are developed during creep. The possibilities of such correlations have already been suggested by Wood et al. and others1-" who demonstrated that the subgrain structures are functions of the creep stress, creep strain, rate of creep, and temperature. Investigations by Sherby and Dorn' have shown that the creep strain, E, at constant load for dilute a solid solutions of aluminum is given by the functional relationship: e = f(8,u,) [1] where: 0 equals te-AH/RT = temperature-compensated time; t, time; AH, activation energy, - 35,800 cal per mol; R, gas constant; T, absolute temperature, above 400°K; and u,, initial creep stress. Consequently, it was anticipated that the subgrain structure that develops during a constant load creep test should also correlate with any two of the three significant variables C, 8, and Another possible correlation between the subgrain structure and the creep variables is obtained by differentiating Eq. 1 with respect to time, whence the creep rate, 2, becomes: = (2L) (2) =f (, u,) e-AHRT [2] or: e = F (c e H/RT, 0) [3] For the minimum creep rate, ;,, 8 is solely a function of U, as revealed by Eq. 1. Consequently, at the minimum creep rate Eq. 3 reduces to: = F (eAH/RT) [41 Correlations between U, and i, eAH/RT were found valid for solid solution alloys of aluminum where AH was a constant of about 35,800 cal per mol. The parameter ;, eH/RT is identical to the Zener-Hollo-mon parameter8," used by them in evaluating the tensile properties of copper and other metals. Eq. 4 suggests that the subgrain structure developed during secondary creep might be correlatable with either of the two variables 2, e H/RT or u,. Some of the solid solution aluminum alloys which were discussed in an earlier report' were also used in the present investigation. Sheets of these alloys were homogenized, cold rolled from 0.100 to 0.070 in. in thickness and then recrystallized to about the same grain size. Their chemical composition and grain size are recorded in Table I. Creep specimens were selected with their tensile axes in the rolling direction. The details for creep testing have been described10 and will not be repeated here. All creep tests were performed under constant load conditions. Experimental Results and Discussion Metallographic Structure of Creep Specimens: In order to obtain a preliminary concept of creep on the metallographic structure of high purity aluminum, the various ruptured specimens previously used to obtain the creep data for pure aluminum were polished and etched electrolytically in a dilute solution of fluoroboric acid. Oblique illumination was used to reveal the substructures which, for convenience, are shown in correlation with the vs. ;, eH/RT curve in Fig. 1. It is necessary to emphasize that the data for the curve refer to the various secondary stages of creep whereas the micrographs refer to the fractured creep specimens. Nevertheless a regular and systematic correlation is observed between E, eAH/RT (or the creep stress) and the micro-structure at fracture. For In (e, eAH/RT) = 42.3, which refers to creep at a high creep rate and a low creep temperature, the fractured aluminum specimen, as shown by the micrograph in the upper right-hand corner of Fig. 1, exhibited extensive deforma-

Jan 1, 1954

[NORTH AMERICA UNITED STATES Alabama BIRMINGHAM BURROWS, WILLIAM C. CORD, RICHARD H. COSTON, OTIS D. JR. FAIRHOPE RUFFLES, WILLIAM R. HUNTSVILLE WAGGONER, JERRY B. MOBILE PETROUTSON, PETER C. SELMA JONES, JAMES J. JR. UNIVERSITY CUDWORTH, JAMES R. JONES, WALTER B. RICHARDS, EDWARD F.]

Jan 1, 1961

By Leonard Grimshaw

THE idea of bonding two dissimilar ferrous metals, and making use of both, is an old one. Tips have been brazed onto tool shanks for many years. The bonding of larger pieces to form whole bars and sheets has also been accomplished, but has received little attention in the technical literature, although a number of patents have been issued covering various methods for its accomplishment. There are three main motives behind the manufacture of composite steels. One is that the physical properties of one steel may supplement those of another; a useful, but at the same time, hard, brittle steel may be backed by a soft ductile one, or a stainless steel may be backed by a steel possessing greater strength. Another motive is direct lowering of cost; an expensive steel may be backed by a less expensive one, bringing down the cost of the piece as a whole. The third motive is an indirect lowering of cost, as when a useful steel is backed by a steel that is easier to machine, so that machining cost on a finished product is lowered considerably. Often more than one of these motives lead to a decision to use a com-posite steel.

Jan 1, 1936

By Arthur L. Walker

In June, 1893, while I was with the Old Dominion Copper Co. at Globe, Ariz., I received an offer to take charge, as manager, of the Baltimore Electric? Refining Co. which had recently built a plant at Baltimore, Md., having a capacity of about 1200 tons of electrolytic copper per month, using the Hayden series system. This was a very large output, for in those days the plants were small and the art was in its infancy. At the beginning of 1893 there were 11 electrolytic refineries in the United States, most of them using the multiple system. The Hayden series system was used at Baltimore and Bridgeport and the Smith series system was in operation at the Electrolytic Copper Co. at Ansonia, COM., and at the Pennsylvania Salt Co. at Philadelphia. In the latter system the plates were placed in a horizontal position, but the operating difficulties were so numerous it was soon discarded. The total production of these 11 plants in 1892 was very small; I have not been able to discover reliable figures of production. There were about thirty electrolytic copper refineries in the world that year, according to Titus Ulke, and the entire production of these

Jan 1, 1932

By C. A. Heiland

MEASUREMENTS of gravity with gravimeters have come into increased use in this country and abroad in the past five years. Probably 100 to 125 gravimeter parties are working in the United States alone. In oil exploration, gravimeter methods have relegated the gravity pendulum definitely to second place, if not third, and now closely rival and possibly surpass the torsion balance in many applications. Gravimeters have lately been applied in mining, although it is doubtful whether they will ever replace electrical or magnetic methods in this work. Notwithstanding the widespread application of gravimeters, there has been no article covering the entire field in the domestic or foreign literature. The purpose of this paper is to meet the demand for com-prehensive engineering information on the subject. The working principles of a number of gravimeters will be, illustrated and treated in relation to the action of corresponding seismometers and astatization methods. The mathematical discussion of theory has been confined to the most necessary fundamentals and been given in as ele-mentary form as possible. A description of calibration methods con-stitutes the last part of the paper. The symbols shown at the top of page 2 will be used in equations throughout the paper.

Jan 1, 1939

EXECUTIVE COMMITTEE OF THE BOARD OF DIRECTORS L E Young. Chairman -. Donald H McLaughlan, Vice-Chairman A B Kinzel Earle E Schumacher John R Suman FINANCE COMMITTEE OF THE BOARD OF DIRECTORS Erle V Daveler, chairrnan Phillip Kraft Clyde E Weed

Jan 1, 1949

By AIME AIME

The Following List Comprises The Names Of Those Persons Elected As Members Or Associates, Who Accepted Election During May And June, 1908 MEMBERS. William H. Bainbridge Searchlight, Nev. William N. Brown, . Gainesville, Va. Willis S. Caypless, .. . . . . Denver, Colo. William B. Clark, Baltimore, Md.

Jan 7, 1908

[University of Alaska College, Alaska Mining Society TOM CHRISTENSON, President MARY ANN KISER, Secretary H. G. WILCOX, Faculty Sponsor WM. FACKLER, Counselor University of California Berkeley, California Mining Association JOHN W. COOK, President LORETTA A. RICHTER, Secretary W. S. WEEKS, Faculty Sponsor]

Jan 1, 1946

By F. S. Crawford

IRON and copper are mined in the Lake Superior district. The iron mines of the district have the best safety record for that industry in the country as a whole, while the copper mines of the district rank second in two of the four years recorded (Table 1). In Utah copper comes mainly from open-pit mines, which enables that state to lead easily in safety. All of the Michigan production comes from deep under-ground workings. About 60 per cent of the iron miners in St. Louis County, Minnesota, are employed at open-pit mines; this favorably affects the combined open-pit and underground accident-frequency rate, as this county pro-vides most of the Minnesota-mined iron ore. In Michigan, however, there are few open-pit mines, the bulk of the production coming from underground mines, while all of the Wisconsin production, just across the state line from Michigan, is from underground mines. In spite of the fact that fewer mines in Michigan use the safer open-pit method, the iron-mining industry of that state maintained a consistently low record from 1931 to 1934; however, it was many points behind its nearest com petitor, Minnesota, with its much greater production from open-pit mines.

Jan 1, 1939

Redetermination of the Chromium and Nickel Solvuses in the Chromium-Nickel System by C. J. Bechtold and H. C. Vacher, p. 14 The text of pages 16 and 17 is in improper sequence. The correct version will appear in the bound volume.

Jan 1, 1962

By H. B. Pulsifer

ABOUT 15 varieties, or modifications, of the best magnesium available were prepared and subjected to etching tests, then examined for microstructure. Of the 30-odd etching reagents that were tried, nearly half, mostly ammonium salts, etched the metal satisfactorily. The surfacing and etching of magnesium is shown to be a very simple and quick operation. The density and hardness of magnesium were determined. The most interesting new observations relate to the finding of the hexagonal etch figures, the crystal laminations, and the fact that the metal is plastic, cold, when restrained or quickly deformed. Under slowly applied pressure cold metal deforms slightly, then shears to fracture without plastic flow. The chief structural features of magnesium are presented in two reduced photographs and 30 photomicrographs. MATERIALS TESTED There are only two sources in the United States from which new metal can be procured: the American Magnesium Corpn. and the Dow Chemical Co. No pronounced structural or property differences in the metals from these two companies were disclosed by the work of this investigation. The following materials were obtained from the manufacturers: 1. Massive crystals of distilled metal (American Magnesium Corpn.). 2. Rods of hot-extruded metal, ½ -in. squares and 5/8-in. rounds (American Magnesium Corpn.). 3. Sheet magnesium, 0.005-in. thick (American Magnesium Corpn.). 4. Cast stick metal, 1 3/8-in. dia. (Dow Chemical Co.). 5. Magnesium-aluminum alloy, hot-rolled plate, ½ in. thick (American Magnesium Corpn.). From these materials, were prepared: 6. Sections from a furnace-cooled ingot made from distilled crystal. 7. Cold-strained pieces from (6), (4) and (2). 8. Pieces cold-squeezed to fracture from (6), (4) and (2). 9. Hammer-struck pieces from (6), (4) and (2). 10. Steam-hammer struck pieces from (6), (4) and (2). 11. Sections from furnace-cooled ingot of the magnesium-aluminum alloy.

Jan 1, 1928