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By Shiou-Chuan Sun

SHIOU-CHUAN SUN (author's reply).-Thanks are extended to Professor Hassialis for his recognition of the usefulness of a new tool, the cataphoretic cell, as an adjunct to the bubble machine and the abstraction test. His questions concerning adsorption, dielectric constant, floatability, activation, and depression are interesting and worthy of discussion. I According to Mueller,28 it is questionable that any of the present formulas gives absolute values of zeta potentials which are completely accurate. The problem is further complicated by the question" of whether the "dielectric constant" has any meaning at all for such a microscopically thin layer. With these in mind, the results in this paper should be considered in the relative sense as a first approximation and not as absolute quantities. Adsorption Referring to item a of Fig. 8, the dielectric constant and the viscosity of the xanthate solutions are the same for galena, sphalerite and quartz. If dielectric constant and viscosity (but not the adsorption) were the first-order variable of the cataphoretic system, as claimed by Professor Hassialis, then the magnitudes of zeta coefficient of galena, spha)erite and quartz would have been similar to each other. These are not. The big difference of zeta coefficient of these three minerals in the same xanthate solutions is not altogether unjustified to be attributed to their difference in adsorption of xanthate ions. This is supported by the results of chemical abstraction tests reported by Ince.14 Again, the big difference of zeta coefficient between wollastonite, calcite, and fluorite in the same laurylamine hydrochloride solutions (p. 118, Figs. 58, 59, and 60 of ref. r5) also indicates that the cataphoretic system is not governed chiefly by the dielectric constant. Beside the data shown in Fig. 8, other experimental evidences15 which support the idea of correlation between adsorption and zeta coefficient are: (I) there is a qualitative parallelism between the zeta coefficient curve and the chemical abstraction curve of sphalerite in solutions of various concentrations of sodium cyanide, (2) there is a qualitative parallelism between the zeta coefficient curve and the chemical abstraction curve of sphalerite in solutions of constant concentration of copper sulphate at different pH values, and (3) there is a qualitative parallelism between zeta coefficient curve and chemical abstraction curve of quartz in solutions with constant concentration of barium chloride at different pH values. The above mentioned experimental results are generally in agreement with Gouy's double layer theory,1-5 and support this idea that the concentration and the kind of ions adsorbed at the mineral surface and in the adjacent surrounding liquid chiefly govern the electrokinetic phenomena. Dielectric constant and viscosity of the liquid medium may be of somewhat lesser importance. It follows that the correlation between the coefficient and adsorption as claimed in this paper is justified. Dielectric Constant The term "dielectric constant " was first introduced into the electrokinetic equations by Perrin.30 In a footnote of his publication he states that Holmheltz has forgotten to include the dielectric constant. The conversion of the moment29 to the zeta potential involves an additional difficulty and confusion not involved for the moment, namely, assigning a value to the dielectric coefficient. This is conventionally assumed to be constant and equal to the dielectric constant of the bulk liquid. 21 The published literature 10, 12 indicates that the values of dielectric constant for dilute chemical solutions have been assumed as those of pure water.

Jan 1, 1947

By Everette Lee DeGolyer

FIFTEEN thousand barrels of oil daily, the production of the United States 75 years ago, amounted to more than 90 per cent of world supply. Russia and Romania, neither of which produced as much as one thousand barrels daily, were the only other suppliers in substantial quantity. The adolescent oil industry of the United States, a dozen years old in 1871, was still confined to the Appalachian region. Wells were drilled by cable tools; many of them were "kicked down" by manpower with a spring pole; and depths were measured in hundreds rather than thousands of feet-a 1000-foot well was a deep well. Casing was an innovation, come into general use only a few years previously and still so new as to be subject to bitter patent litigation. Crude oil was packaged in wooden barrels and shipped by flat boat and barge on the creeks and rivers and by railroad. Such pipe lines as existed were only a few miles long. There were many refineries. Pittsburgh, Cleveland and the Atlantic seaboard were refining centers. Refineries were very small, however, and their operations consisted essentially in simple fractionation by distillation and treating for quality. The products in demand were burning oil or kerosene and lubricating oils. Oil was not yet used as fuel and gasoline was a nuisance to the refiner.

Jan 1, 1947

By James E. Mills

In the work of exploring certain gold-bearing gravels in the American Valley, Plumas Co., California, entrusted to my charge by Prof. A. Agassiz, of Cambridge, and Q. A. Shaw, Esq., of Boston, it became necessary to sink a shaft through loose materials containing in some layers large quantities of water, and I have been compelled to devise a new method which has proved successful and may be of service elsewhere.

Jan 1, 1885

By W. P. Sykes

IN an earlier paper1 the composition-temperature limits of the gamma iron phase in the iron-tungsten system were reported as approximated Fig. I.-DIAGRAM OF ALPHA-GAMMA LOOP AS DETERMINED BY MICROSTRUCTURE AND THERMAL ANALYSIS. by thermal analyses. At that time no attempt was made to develop metallographic evidence of the coexistence of two phases in the iron-rich solid solution at temperatures between 900° C. and 1400° C.

Jan 1, 1931

By Wilson Blake

A mathematical model based on the finite element method of stress analysis has been used to describe the behavior of the western wall of the Kimbley Pit as its slope was steepened from 45° to 57°. Theoretical stress changes because of slope modification are slight except at the toe of the modified slope. Magnitudes of stress created are small when compared with the strength of a competent rock. Resulting displacement patterns point out the need for determining the in-situ state of stress at a site prior to excavation or modification. A comparison of model results with field measurements shows that, in general, the model has described the measured behavior of the west wall of the Kimbley Pit remarkably well. The Bureau of Mines and the Kennecott Copper Corp. began joint research on open-pit slope stability at the Kimbley Pit, Ely, Nev., in 1961. The initial or planning phase of this research dealt with a detailed geologic study of the Kimbley Pit, determination of in-situ stresses in the district, laboratory and field tests to determine rock properties, and the design of a full-scale experiment to study the behavior of this pit as its western wall was steepened from 45° to 57°. Fig. 1 shows a cross-section of the original pit outline, the steepened pit outline, major geologic features, and the two instrumentation adits. After the final or slope modification phase of the research began, a laboratory research program was initiated to develop a mathematical model that would analytically describe the behavior of the pit as its western slope was steepened. This theoretical model study of the slope modification at the Kimbley Pit was conducted with the finite element method of stress analysis. The results are described in this report.

Jan 1, 1969

By G. B. Craig, B. Ramaswami

The temperature and strain rate dependence of the flow stress ratio and the stvain rate dependence qi the flow stress of annealed polycrystalline a zirconiur were determined over the temperature range 30 0" to 1000°K. Some evidence was found for strain aging and discontinuous flow in the temperature ranges 520" to 650°Kand650" to 760°K, respectively. The Cottvell-Stokes relationship was obtained when deformation occurred by twinning as well as slip. The flow stress ratio showed a strong dependence on temperature and strain rate above 800°K. The expevirnental evidence indicated that the rate-controllitzg mechanism for the deformation of a zirconium above 800°K was dislocation climb, and that the deformation was not thermally activated in the range 520" to 800°K. The stacking-fault energy of a zirconium was estimated to be about 250 ergs per sq cm. A knowledge of the temperature and strain rate dependence of the applied stress necessary to deform a crystalline solid is essential for understanding the thermally activated processes occurring during deformation.' Several experimental techniques have been developed for studying these processes.273 One of the techniques is the deter mi nation of the strain rate dependence of the flow stress at constant temperature. In close-packed crystals, it has often been observed that the change in stress due to a change in the strain rate varies linearly with the flow stress, (~1,' This relationship, known as the Cottre ll-Stokes law, is obeyed when deformation occurs by glide alone. However, when deformation occurs by twinning as well as glide, there is disagreement among different investigators on whether the Cottrell-Stokes law is observed. Whereas Thornton et ~1.~find departures from Cottrell-Stokes law when twinning occurs in copper, ~avis~ and sasinski? find that Cottrell-Stokes law is obeyed when deformation occurs by twinning as well as slip in cadmium and magnesium, respectively. One of the main objectives of this study is to determine whether the Cottrell-Stokes law is obeyed when deformation occurs by twinning as well as slip. The second technique that has been used extensively to study the thermally activated deformation of crystals is the determination of the ratio of the flow stresses, at identical dislocation structures and con-

Jan 1, 1968

By Charles M. Rolker

It is not my purpose to present a complete description, still less a thorough discussion from a theoretical stand-point, of the Leadville ore-deposits. Hence I have given to this paper the more modest name of " Notes;" since it is little more than a record of observations made three or four years ago, and now published from my original memoranda, with the view of preserving the facts rather than of

Jan 1, 1886

By Robert B. Kistler, Ward C. Smith

The borate industry is one of the few sectors of the mining and mineral-processing industry which the United States still dominates. Since about 1927, the United States has supplied over half of the world's total boron and borate raw materials, and many of the chemical derivatives as well. Chiefly responsible for this record are companies producing sodium borates from two large deposits in southern California, at Boron (Kramer) and Searles Lake. The sodium borates, or products derived from borax and borax-containing brines, are the preferred borates for industry because they are soluble in water and combine readily with most other chemicals. Calcium borates are required for certain end uses, and these are produced from smaller colemanite-ulexite-probertite bodies. Sodium-free borate compounds also are produced from boric acid, which can be manufactured from either sodium or nonsodium borate minerals. During the past hundred years, the use of boron compounds throughout the world has risen from a few tons per year to the equivalent of over a million tons of B2O3. Leadership in supplying borates shifted from country to country and from region to region during this period, generally as the result of the development of newly discovered deposits that were better in quality, more accessible, or more economically exploitable than previous sources (Table 1). Primary Products and End Uses The principal borate products offered by primary producers in the United States are listed in Table 2. In general, these products are utilized worldwide by almost all consumers, regardless of the original source of the primary borates, In the United States, the primary borates all originate in southern California. Colemanite is produced as crude or processed crude ore from the Death Valley area and is utilized by the fiber glass and ceramic industries without further treatment. Production from Searles Lake, CA is from brines that are processed in chemical plants where borax and other compounds are recovered and the principal borate products are produced. At Boron, CA, the world's leading producer is mining a deposit of mineral borax and operating a chemical refinery. The mineral borax is mined together with included clay, and refined borax or "10-mol" is one of the refinery products. The mineral and the chemical compound are identical, Na2B4O7 • 10H2O. In addition to ship¬ping all major refined borate products from [ ]

Jan 1, 1983

By Sterry Hunt

The American Institute of Mining Engineers, and American science in general, have sustained a great loss in the death of Prof Benjamin Silliman, deceased at New Haven, Connecticut, on the 14th of January, 1885, at the age of sixty-eight. But a month has passed since, as one of the pall-bearers, I paid the last tribute to the remains of my old friend and honored master.

Jan 1, 1885

By John M. Dealy, Robert D. Pehlke

This note presents a summary of the available literature on activity coefficients at infinite dilution in binary metallic solutions, Table I. These data should prove useful in not only examining the therm-odynamic properties of binary metallic solutions, but also in predicting the activity of a component in a complex alloy. The relationship proposed by wagner1 for expressing the activity coefficient in dilute solution is of the form:

Jan 1, 1963

By Cyril Stanley Smith

For many years sulphur and its congeners selenium and tellurium have been regarded as very harmful elements in copper and copper-rich alloys. Like many similar prejudices, this has been found to be partly wrong. All three of these elements actually have no great effect on the working properties of copper and its alloys, and are desirable additions in that they considerably enhance the machinability of alloys in which they are present. Because of their possible commercial importance, a study of the machinability and other properties of the pure binary alloys was made, as described in this paper, and the effect of selenium on a large number of copper alloys was determined. The current opinion regarding the deleterious effects of elements in this group undoubtedly arose because of occasional failures of tough-pitch copper containing unusually high tellurium, and because of the well-known fact that sulphur causes spewing and unsoundness in tough-pitch copper. Siebe,1 also Deretchey and Margolina,2 studied the effect of sulphur on copper and showed that in the absence of oxygen it was present in the form of copper sulphide, which was less harmful to the properties than an equivalent amount of copper oxide. No data have been published on selenium and tellurium, although the statement is often made, following Eggleston,3 that tellurium makes copper hot-short. Copper specifications call for only traces of these elements. Skowronski and Mosher4 give data on the effect of selenium and tellurium on the conductivity of tough-pitch copper. In private communication Mr. Skowronski says that the samples were hot-forged from small castings and drawn to 0.081 in. diameter, but it should not be inferred from this that these elements are harmless to the working properties of wirebars and commercial shapes. Constitution and Microstructure Constitution.—Sulphur, selenium and tellurium exist in their alloys with copper in the form of copper sulphide, selenide or telluride. These compounds are practically insoluble in the solid state and possess limited

Jan 1, 1938

By Cyril Stanley Smith

For many years sulphur and its congeners selenium and tellurium have been regarded as very harmful elements in copper and copper-rich alloys. Like many similar prejudices, this has been found to be partly wrong. All three of these elements actually have no great effect on the working properties of copper and its alloys, and are desirable additions in that they considerably enhance the machinability of alloys in which they are present. Because of their possible commercial importance, a study of the machinability and other properties of the pure binary alloys was made, as described in this paper, and the effect of selenium on a large number of copper alloys was determined. The current opinion regarding the deleterious effects of elements in this group undoubtedly arose because of occasional failures of tough-pitch copper containing unusually high tellurium, and because of the well-known fact that sulphur causes spewing and unsoundness in tough-pitch copper. Siebe,1 also Deretchey and Margolina,2 studied the effect of sulphur on copper and showed that in the absence of oxygen it was present in the form of copper sulphide, which was less harmful to the properties than an equivalent amount of copper oxide. No data have been published on selenium and tellurium, although the statement is often made, following Eggleston,3 that tellurium makes copper hot-short. Copper specifications call for only traces of these elements. Skowronski and Mosher4 give data on the effect of selenium and tellurium on the conductivity of tough-pitch copper. In private communication Mr. Skowronski says that the samples were hot-forged from small castings and drawn to 0.081 in. diameter, but it should not be inferred from this that these elements are harmless to the working properties of wirebars and commercial shapes. Constitution and Microstructure Constitution.—Sulphur, selenium and tellurium exist in their alloys with copper in the form of copper sulphide, selenide or telluride. These compounds are practically insoluble in the solid state and possess limited

Jan 1, 1938

By C. Chu

An investigation has been made of the radial heat-wave process using a mathematical model in two-dimensional cylindrical coordinates. This model considers combustion, convection and conduction inside the reservoir, but only conduction in the bounding formations. From a study of the general features of the process, an important phenomenon has been revealed, namely, the feedback of heat into the reservoir on the trailing edge of the heat wave. The effects of various process variables on the performance characteristics of the process have also been investigated. It was found that up to the time when the combustion front reaches a given point, the per cent heat loss, provided it is not higher than 40 per cent, is approximately directly proportional to the square root of thermal conductivity arid fuel content, but inversely proportional to the square root of gas-injection rate and oxygen concentration. The effecr of reservoir thickness is more pronounced, since halving the thickness doubles the per cent heat loss. The most decisive factor in determining the center-plane peak temperature is the fuel content of the reservoir. Within the temperature range investigated, doubling the fuel content doubles the peak temperature in the early stage, but the rate of decline of the peak temperature is high. Reservoir thickness is also a very influential factor. The peak temperature is lowered when the thickness is reduced; however, the effect of thickness becomes less pronounced when the thickness is high. Reduction of oxygen concentration increases the peak temperature in the early stage but lowers it afterwards because of the higher rate of decline of the peak temperature. Increase in gas injection rate or decredse in thermal conductivity geives a higher peak temperature which stays high for a longer period. The propagation range of the heat wave is chiefly governed by the fuel content of the reservoir. An increase of 0.2 1b/cu ft in the fuel content increases the propagation range by 100 per cent. The propagation range is more than doubled by doubling the gas injection rate, or reservoir thickness, or by reducing the thermal conductivity by 50 per cent. Comparatively, oxygen concentration has less effect on the propagation range. INTRODUCTION Several investigators have conducted theoretical studies of a radial heat wave. Vogel and Krueger1 studied a system with a moving cylindrical heat source of constant temper- ature, considering conduction in the radial direction only. Ramey2 included conduction in the vertical direction in his studies. Bailey and Larkin2 attacked a more general problem where initial well heating, vertical heat losses and arbitrary frontal velocities were included. In all these studies, however, conduction was considered to be the only means of heat transfer. Bailey and Larkin in a later paper included the effects of convection in a study involving both linear and radial geometries. Vertical heat losses were neglected in the radial case. Katz5 studied a similar problem in a one-dimensional radial model, using a heat-loss coefficient to account for vertical heat losses. Selig and Couch6 mployed a cylindrical model and investigated two limiting cases. In one case they considered no heat loss from the reservoir whereas in the other they assumed a constant temperature at the interface between the reservoir and its bounding formations. Thomas' studied a more general case but assumed a permeable bounding formation so that the convection effect is not confined to the reservoir. In the present work a more realistic and more generalized model is used. It involves a two-dimensional cylindrical system with combustion, convection and conduction inside the reservoir, but only conduction in the bounding formations. The purpose is to establish the temperature distribution both inside and outside the reservoir, to study the general features of the radial heat wave process, and to investigate the effects of various process variables on the performance characteristics of the process. THEORY We fist consider a circular porous reservoir of thickness H extending vertically from y = — H/2 to y = + H/2. The reservoir extends from a well bore radius r, to an external radius re. A stream of oxygen-containing gas is introduced into the reservoir through the wellbore. The oxygen-containing gas reacts with the fuel contained in the reservoir and forms a combustion front wherever the prevailing temperature can support the combustion. It is here assumed that this combustion front constitutes a cylindrical surface source of heat having an infinitesimal thickness in the radial direction and extending vertically throughout the whole thickness H. This is designated as Region I. We next consider a Region II corresponding to the upper and lower formations bounding the reservoir, extending from y = — - to y = — H/2 and from y = + H/2 to y = + m. Since r, is very small, we may assume that the two bounding formations have the same dimensions, symmetric with respect to the center plane of the reservoir. In this way, we may take the upper half of the system alone into consideration. In contrast with

By Ancel St. John

During a session on coal and coke at the February, 1926, meeting of the American Institute of Mining and Metallurgical Engineers, the writer called attention to the important work on the X-ray analysis of coal1,2 being carried on in England by C. Norman Kemp and his associates. This aroused so much interest that a paper on the subject was requested for the October meeting. It has seemed advisable to make this paper a preliminary survey of the present status in the application of X-ray methods to coal problems and to follow it from time to time with further articles as the art develops. A survey of this sort naturally divides itself into two parts, radio-scopic analysis of the distribution of constituents through the body of the coal, and diffraction analysis of the state of association of the elementary components. In this article the subject matter concerning radioscopic analysis has been drawn almost entirely from the writings of Kemp and his associates and the illustrations have been sptcially furnished by him. It is a pleasure to record here a great indebtedness for this courtesy and cooperation. The subject matter and illustrations concerning diffraction analysis are taken from the author's unpublished researches. Nature and Properties of X-rays Before proceeding it is well to recall the nature and some of the properties of X-rays, as well as our present conception of atomic structure According to the accepted theory atoms are composed of electrically-charged particles. A positively-charged center, called the nucleus,

Jan 1, 1927

By W. B. HILLHOUSE

AN excerpt from the Alabama State Mining Law, pertaining to, transporting men' into and out of the mines, reads as follows: "A trip of empty cars may be operated for the purpose of taking employees into and out of the mine, where the distance to and from their work exceeds one mile." The State Mining Department of Alabama includes in its inspection the transportation of men into and out of the mines, also studying and noting improvements, or progress made, that would tend to create a greater assurance of safety in this practice. Everyone is familiar with the original safety methods employed in man-trip transportation, such as passing a rope around the trip of cars, or through the cars, fastened in the conventional manner, and with the usual "clog," commonly called a drag, on the rear end. Also there is a more advanced method of transporting men, such as the double-rope system, which is feasible on slopes used exclusively for this purpose, and is very satisfactory. However, for the past eighteen months; the Republic Steel Corp. and the Tennessee Coal, Iron & Railroad Co. have adopted a practice that shows

Jan 1, 1935

This discussion was prepared by members of the Phelps Dodge Corpn. staff who were designated to review the minutes. It is confidential but permission has been granted to distribute copies among those who attended the Conference. The minutes of the above conference contain numerous references to the plants and practices of Phelps Dodge Corporation. As many of these references are inaccurate, the following notes are made covering such points: Construction Magnesite Brick in Reverb. Arch (1) An.18" arch, 20 feet long, was built on one furnace with 5 feet on each side of magnesite brick, the center portion .being of silica brick. The furnace was put in operation February 13, 1930 and on April 23rd after 68.8 days' operation it was replaced due to failure of the silica brick forming the center of the arch. At this time, while the silica brick had completely gone, there was 14" of magnesite left. Bridgewall Tapping (2) Tapping matte through the burner wall was first tried at the Copper Queen Smelter in April, 1925. At that time, a copper casting with 1 ½ extra heavy pipes for water cooling cast in it, and having one taphole block was used. Later, on the other (old) furnaces, similar castings, but equipped with two tapholes, were used. We found with these furnaces that we could tap through the burner wall at the beginning of a campaign, but would subsequently have to go back to side wall tapping. This was the case until sometime in 1926. The new furnaces, that went in operation at the beginning of 1927, each had water. cooled castings with two tapholes. These have been used entirely and have been quite successful. Sometime after the furnaces were put into operation sidewall tapholes were put in, simply for the removal of any accumulation of matte that might be temporarily retained at the front end by bridges or dams in the furnace formed by overcharging locally.

Jan 1, 1930

By G. Baralis, P. Gondi, I. Tangerini, G. Scandola

The precipitation behavior of Zn-0.5 pct A1 alloy single crystals was studied by means of electrical resistivity measurements and by optical and electron microscopy. The single crystals for the resistivity measurements were prepared by an original method in - 100-p -thick sheets. The order of the precipitation kinetics ranged between 1 and 1.5. The dislocations play a relevant role in the first-order kinetics. Precipitation always occurs both on dispersed particles and on dislocations. Statistical examinations have shown that the first-order kinetics can have two different activation energies; i.e., the precipitation can have dz;fferent mechanisnrs which could not be identified, however, in the course of the research. During the tnetallographic exanzination of the precipitation structures a specific process of dislocation decoration was obsereed. The main purpose of this work was to study the contribution of dislocations to the precipitation. A number of authors have observed precipitation on dislocations and reference might be made to several monographs on the ubject.'' The possibility that dislocations also accelerate precipitation has been considered by Turn-bull3 and Fischer et al.4 The studies described in the present paper were carried out on zinc, chosen as a base metal owing to the ease with which dislocations can be introduced into it and because of the absence of excess vacancies after quenching in conditions where phenomena of accelerated precipitation still occur. Aluminum was preferred as alloying element because of the accelerated precipitation phenomena that resulted in a preliminary reearch. EXPERIMENTAL METHODS The observations refer to a Zn-0.5 pct A1 alloy. The zinc was 99.995 pct pure; a typical spectroscopical analysis is given in Table I. As a rule the alloy was subjected to homogenization, quenching, or slow cooling and annealing. Homogenization was carried out by heating at 390" to 410°C for 24 hr. From the homogenization temperature, some specimens were quenched and some slowly cooled at a rate of 2°C per sec. At this rate no precipitate was detectable under the optical microscope just after cooling. Quenching was carried out simply by dropping the specimens into water, aqueous ethylene glycol solution at -30" c, or liquid-nitrogen baths placed close to the homogenization oven. Vaseline oil baths were used with a thermal stabilization of 10-20 for both the aging treatments and the measurements; aging was generally carried out at 90" or 130°C. To avoid oxidation phenomena during heating, the vaseline oil baths had to be frequently renewed. The precipitation kinetics were studied by means of electrical resistivity measurements, using ans potentiometric method (reproducibility ± 5 x 10 5 v, that is 0.5 pct of the total voltage decreases on the specimens during precipitation). First, various types of specimens were tested, i.e., polycrystals, single crystals grown in capillary quartz tubes, and thin single-crystal sheets prepared by means of an original method requiring no container except for the natural oxide. Even if fully annealed, the polycrystals and the capillary grown single crystals showed resistivity in -creases, most probably due to dislocations introduced in the course of the measurements. Similar resistivity increases in pure zinc were noticed by another author. Only the single-crystal sheets showed no resistivity change; thus they were chosen for the subsequent tests. As already mentioned, these single crystals were obtained by using, as a container, the natural oxide on the zinc surface; the oxide strength is sufficient to maintain the original shape during melting with sheets up to 500 p thick. An initial zone melting and subsequent zone leveling, which led also to formation of the single crystals, were thus carried out on rolled sheets of the required thicknesses (- 100 p) and shape, lying on a flat silica surface. The resistivities were first evaluated by measurements at the liquid-nitrogen temperature. This method gave poor reproducibility, however, and this was attributed to the thermal cycles which had to be operated. To avoid cycles and handling, it was therefore decided to make measurements directly in the annealing oil baths; this required thermal stabilization at ilo-' "C. In this way only the resistance changes were measured. Specimens of pure zinc and of completely annealed alloy were always examined as controls together with those under consideration; only those measurement runs were taken into account where the reference samples showed no resistance increases. Again, the main inconvenience was due to oxidation and this was avoided by renewing the oil baths; even so data reproducibility was poor and the observations were therefore carried out on a large number (many hundreds) of specimens so as to provide indications of statistical value. For the transmission observations under the elec-

Jan 1, 1969

By Thomas T. Read

THE fact that certain types of ore-deposits have attained their present condition through the action of descending surface waters was, perhaps, first clearly pointed out by Posepny.1 The oxidizing effects of such waters were discussed by Penrose,2 and many papers dealing with this phase of the subject have subsequently appeared. That secondary enrichment of sulphide ores, however, might be produced by descending surface waters was not clearly understood until after the copper-bearing veins of the Butte district, Mont., had been carefully studied by the geologists of the U. S. Geological Survey, al¬though De Launay3 had suggested that sulphides might be transported from point to point and re-deposited in the zone above the level of ground-water. As a result of the study of the Butte district, two papers by geologists engaged in the work appeared within a short interval. The first by Weed,4 dealing with the enrichment of veins by later metallic sulphides: and the second by Ernmons,5 treating of the secondary enrichment of ore-deposits in general. In the latter paper it was pointed out that a typical vein of sulphide ores which has been subjected to the action of descending surface waters exhibits four zones,-an upper or surface zone, in which the changes have been mainly of removal, the products being typically oxides; a second zone of oxide enrichment, in which the less soluble metals brought from above have been precipitated as carbonates or oxides; a third zone of sulphide enrichment,

Mar 1, 1906

By C. F. Cockrell, H. E. Shafer, J. W. Leonard

A significant technological development is discussed for the processing of certain power plant flyashes that are a problem because they contain a high water-soluble mineral content and yield inferior flyash-based brick. This development is based on the addition of hydrochloric acid to the flyash-bottom ash-sodium silicate blends used for the production of flyash-based structures. Favorable changes are evi-dent in sodium silicate consumption, where about half the amount used for making brick from normal flyash is required, processing costs, and strength and appearance of the resulting freshly formed green and fired structural products. In some high cost in-stances (above the $30 or less per thousand brick estimated for normal flyash), hydrochloric acid additions can replace or reduce other costly additives normally required for problem flyashes. This results in savings of as much as $9 per thousand brick. These developments offer promising possibilities for utilizing problem flyashes as well as flyashes which may come into contact with water soluble sulfur as a result of the eventual application of certain experimental air pollution control processes. Much of the research datal-6 accrued through work by the Coal Research Bureau of West Virginia University for the Department of Interior's Office of Coal Research on converting waste power coal ash to valuable brick and other structural products, can be categorized as follows: (1) general ash-to-brick tech- nology; (2) specific ash-to-brick optimization; (3) pilot plant progress; (4) production cost estimates. A summary of the progress on bench-scale experiments indicates that coal ash can yield two types of brick. An acceptable brick is obtained by mixing 73.6% fly-ash, 23.5% bottom ash and 2.9% sodium silicate solution (dry basis). Depending on the flyash and bottom ash used, optimum brick can be manufactured by mixing 72-77% flyash, 20-25% bottom ash and 2.3-3.0% sodium silicate (dry basis) with Na2O : SiO2 ratio varied according to the composition of the flyash used. These blends are thoroughly mixed and mechanically formed into green brick shapes at pressures ranging from 1000 to the more usual 3000 lb per sq in. The green shapes then are dried and fired at temperatures ranging from 1975-2150°F using clay brick cycles that are shorter than standard. Other findings reported to date indicate that when making optimum brick, it is necessary to carefully control the top size of the moisture-releasing bottom ash so that it falls between 8 and 30 mesh, depending on the flyash used. Moreover, the chemical composition of bottom ash and flyash have been found to be of little significance with the exception of a few problem flyashes which are the subject of this paper. Finally, the pilot plant, which was previously reported under construction, is now in operation. This will indicate, among other things, the cost of brick production, which was earlier estimated for non-problem flyashes at $30 or less per thousand brick. The foregoing bench-scale technology is applicable to all the initially tested ashes as well as to the majority of ashes examined during the course of research. However, a few of the ashes yield green and fired products that may be structurally inferior or unacceptable, necessitating excessive and diverse reagent addition, and/or may be coated with unsightly surface deposits. These problem ashes generally originate in certain areas of Illinois, western Ken-

Jan 1, 1969

By A. C. Rubel

WHAT does management expect of W and from an engineer? First and foremost, it expects that he should become, and therefore should fit himself in every way to be, a part of management so that he may assume as much and as many of the responsibilities of management as his ability and the opportunities of the job permit. Let me make clear at the start that the profession of pure, technical engineering offers but limited opportunities at the top levels because of the inherent organization of engineering work. The line of succession to top jobs may be likened to a cone with a broad base and an extremely sharp point. Consider any oil company, large or small, or any operating function of that company, and you will find few top engineering jobs in the organization. This is true by the nature of the work handled. There will be a few district engineers depending on the spread of operations, a chief petroleum and production engineer, perhaps a few research engineers, possibly some technical executive assistants, and that is usually all. The road to these jobs is a long one and the competition is tough. The larger the organization the greater the opportunity, but always the ratio of engineers to top engineering jobs is only a small one.

Jan 1, 1947