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By J. J. Stokes

Literature on the electrolysis of aluminum from cryolite melts and on the structure of these melts is surveyed critically. Data on density, freezing point, and other properties are reviewed. Theories of the electrolysis are examined in the light of these data. Two theories are presented which account equally well for the observations. ALTHOUGH the production of aluminum is a large-scale industrial process, consuming approximately 3 pet of all of the electric current generated in this country, the mechanism of the Hall Process remains a 70-year-old mystery. It is a remarkable fact that the aluminum industry, which was established largely through research and owes much of its growth to research, still employs as its basic process the one developed by Charles Martin Hall while he was still a young man working in a woodshed. There are, of course, modifications in detail and a tremendous expansion of the size of the units used, but basically the process employs carbon anodes and a carbon-lined iron vessel as a cathode for the electrolysis of alumina dissolved in molten salt. Of the almost infinite variety of salts available, the relatively minor Greenland mineral, cryolite, 3NaF.A1F3, is still the only one which gives good performance in the electrolysis. In the early days, the process was thought of as a simple one. The dissolved alumina dissociated and, during the electrolysis, the aluminum was carried to the cathode where it was discharged and collected in a pool of metal. The oxygen was carried to the carbon anode where it reacted to form primarily carbon dioxide together with some carbon monoxide. About the only virtue that can be claimed for this hypothesis is that of simplicity. The actual mechanisms must be tremendously more complex. This paper is devoted to a rather narrow part of the whole subject, namely, what ions are present in the bath, and by what mechanism the current is carried. The complexity of the literature on this system is demonstrated in Table I, which shows the ions postulated as being present during the process. This system is not easy to investigate. Cryolite melts at about 1000°C, so that all the investigations are at relatively high temperatures. Molten cryolite fumes in air, particularly if excess aluminum fluoride is present. The cryolite changes composition on heating at 1000°C, principally by reaction with moisture in the air, but apparently also by reaction with oxygen. Cryolite reacts with most of the customary materials of construction, and those that are not attacked by cryolite seem inevitably to react with molten aluminum. Graphite is the only common material that is inert to the electrolytic bath. Pure cryolite can be held in platinum. There is hope that some of the newer refractories will stand up in bath, and their development for this purpose would be a major advance in the field. The techniques to be discussed, then, are not the most advanced ones. Rather, they are examples of old standardized methods applied under difficult conditions. The principal methods that shed real light on the mechanism are density, electrical conductivity, freezing-point lowering, transport number, viscosity measurements, and reactivity of bath with carbon dioxide. The first measurement to be discussed is density. This procedure is relatively straightforward. A hollow platinum bob is suspended by fine platinum wire from an analytical balance into the melt being investigated. Density1-4 of the system sodium fluoride-aluminum fluoride is shown in Fig. 1. There is a maximum in the density near the cryolite composition, but actually the maximum is on the NaF-rich side of cryolite, close to the composition NaF - Na3AlF8. Density measurements are also useful in giving a clue to the nature of cryolite-alumina melts.1, 4 On the first addition of alumina, density decreases, Fig. 2, although the density of alumina, either solid or liquid, is higher than that of cryolite. These density results indicate that the systems are not simple. A great deal of effort has been spent in measuring the electrical conductivity of molten cryolite and of cryolite with various additives. Conductivity measurements are quite easy for fused salts that can be measured in a dip cell, but no successful dip cell has been made available yet for cryolite. Recourse is had

Jan 1, 1959

[A AALSETH Earl P (M 51) Consult Geol Engr 2019 Eldorado Dr, Billings, Mont ABADIE Henry G (M 43) Asst to. Supt of Oper Long Beach Oil Dev Co 925 Harbor Plaza, Long Beach 2, Calif. ABBET Waldo (A 56) Asst Diet Oper Supt Sun Oil Co P 0 Box 66, Stowelt, Tex ABBOTT Clifton T (A 60) Apartado 677, Maracaibo, Venezuela ABBOTT Fred E Jr (M 59) Abqaiq Diet Mgr Arabian American Oil Co Dhahran, Saudi Arabia ABBOTT J L (M 56) Partner Pritchard & Abbott 1010 Ft Worth Natl Bk Bldg, Fort Worth 2, Tex ABBOTT Richard H (J 51) Partner Abbott & Howard 422 W Hermosa, San Antonio 12, Tex ABBOTT William G (M 50) Div Mgr Rice Engrg &. Operating Inc Box 1142, Hobbs, N. M. ABDERHALDEN Ronald R (J 59) Prod Engr Continental Oil Co Box 100, Carml, 111]

Jan 1, 1961

By Rodolfo V. de la Cruz

The accurate assessment of the in situ deformability of rock masses is very important in the de and construction of underground openings for mining and geotechnical engineering applications. This paper presents a method and device for determining the in situ deformability of rock masses by relating the borehole jack load to the diametral displacements at a number of orientations around the borehole wall. The method called mu1tiple measurement method include the steps in which: a) diametral displacement sensors are installed at different orientations around the borehole to measure the changes in length of various diameters of the borehole; b) a uniaxial load is applied on two opposed octants of the borehole wall, and; c) using elastic theory and assuming a reasonable value for the Poisson's Ratio of the rock mass, the in situ deformability of the surrounding rock materials is determined from the measured diametral displacements and applied unidirectional load. The multiple measurement method has a significant advantage over existing methods since it provides several independent data in a single test from which to calculate the in situ deformability of the rock mass. The multiple data provide a check and counter check on the reliability and accuracy of the various measurements. The multiple data would also provide a means of quantifying the degree of fissuring on the borehole wall. Information on the degree of fissuring is very important in numerical modeling of rock masses.

Jan 1, 1984

By E. S. Machlin, A. A. Hendrickson

Use was made of a recently developed surface-accumulation diffusion technique to measure the self-diffusivity of edge-type dislocation singular lines (Burgers vector along <110>) in a bent and polygonized single crystal of silver. Two factors are involved in obtaining a number for the diffusivity. One factor, the dislocation-line density, was measured by a microscopic technique recently developed, and the value of the other parameter, the effective "diameter" of a dislocation pipe, was estimated. With these parameters equal to 7.3 X 106 dislocations per sq cm and 10-7 cm, respectively, it was found that the self-diffusivity along edge-type dislocation lines was a factor of about two times the average grain-boundary self-diffusivity. The dislocation-pipe diffusivity is about 7x10-7 sq cm per sec at 450°C. THE possibility of short-circuit diffusion through imperfections in crystals has been recognized for some time. It was only recently, however, that concerted effort has been expended to obtain values of diffusivity for grain-boundary short circuits. The work, for example, of Hoffman and Turnbull1 on silver, Fisher&apos;s&apos; analysis of the grain-boundary dif-

Jan 1, 1955

The following is an incomplete list of members and guests who called at Institute headquarters between Nov. 10 and Dec. 10, 1917. Harlan H. Bradt, Duluth, Minn. Lt. Geo. H. Morgan. Albert Burch, San Francisco, Cal. F. W. Osborn, Ajo, Ariz. J. A. Daniel, Institute of Mining & Metal- J. C. Ray, 2d Lt., 0. M. C., N. A. lurgy, London. A. E. Ring, Creede, Colo. Martin Fishback, Benson, Ariz. Geo. B. Rodgers, Dobbs Ferry, N. Y. E. L. Foucar, San Francisco, Cal. Forest Rutherford, Pueblo, Colo. I. A. L. Henderson, Institute of Mining & J. G. Scrugham, Reno, Nev. Metallurgy, London. A. F. Shurick, Forest Hills, L. I., N. Y. Jerome A. Hilbert, Santa Monica, Cal. Arthur C. Spencer, Washington, D. C. B. B. Hood, Chrome, N. J. Robert C. Sticht, Mt. Lyell, Tasmania. J. C. Hoyt, Jerome, Ariz. A. Perry Thompson, San Francisco, Cal. A. F. Kennedy, Duluth, Minn. J. B. Tyrrell, Toronto, Canada. Paul S. King, Wilmington, Del. Thor. Warner, Phoenix, Ariz. Alfred C. Levis, Golden, Colo. S. F. Wellman, Cleveland, 0. A. F. Lucas, Washington, D. C. Gardner F. Williams, San Francisco, Cal. B. E. McKechnie, Sharon, Pa. W. G. Woolf, Salt Lake City, Utah.&apos; A. N. Mackay, Barranquilla, Colombia. C. W. Merrill, San Francisco, Cal. P. G. Beckett expects to be located in New York for some time, and may be addressed care of the Phelps, Dodge Corporation at 99 John Street. Corey C. Brayton and E. R. Richards have temporarily closed their San Francisco offices in order to give more time to their operations at Midvale, Utah.

Jan 1, 1918

By C. H. Samans, G. F. Tisinai

HARDENING and embrittlement of the ferritic chromium stainless steels at temperatures near 885 °F have been known for a long time.&apos; However, no satisfactory explanation has been given. Both ordering and precipitation hardening have been suggested. Fisher, Dulis, and Carroll2 discovered a chromium-rich body-centered-cubic precipitate in embrittled alloys. Subsequently, Williams&apos; and Wright4 also have found evidence of this body-centered-cubic constituent. William&apos;s hardness, electrical resistance, and magnetic studies led to his proposal of a new constitutional diagram for the Fe-Cr alloys. The new feature of this diagram is the eutec-toidal decomposition, below about 970°F, of the s phase into two stable body-centered-cubic solid solutions, one rich in iron and the other rich in chromium. An observation of Heger5 that the amount of s phase has increased and the amount of chromium-rich body-centered-cubic phase decreased in the interval 5000 to 32,600 hr at 900°F, even though the alloy increased in hardness, casts some doubt on this diagram. If precipitation hardening causes the embrittlement, the precipitate probably is always coherent with the matrix, since no evidence of overaging has been reported. It cannot be stated positively, however, that Fisher&apos;s body-centered-cubic constituent is the embrittling phase. According to Preston&apos;s data,6 such a chromium-rich phase should have a parameter less than about 0.5 pct larger than that of the iron-rich matrix lattice. Moreover, the constitutional relationships whereby Fisher&apos;s constituent forms, and whether it is stable, metastable, or a transition phase, are not yet completely clear. The recent studies of Wright4 and of Lommel,7 as well as the earlier studies of Becket8 and of Hochmann,9 have shown that 885°F hardening occurs in relatively pure Fe-Cr alloys. No evidence of its occurrence or absence in chromium itself has been reported. The rate of hardening in high purity alloys seems appreciably slower than that in alloys containing larger amounts of impurities (chiefly carbon and nitrogen). This may be due merely to the absence of hardening and straining effects from precipitated carbides and/or nitrides. These observations on high purity alloys make it seem unlikely that 885 °F hardening is caused by a constituent containing other than iron and chromium atoms, e.g., carbides and/or nitrides. Wright,4 Lommel,7 and Lena and Hawkes10 emonstrated the accelerating effects of a finely dispersed precipitate of (probably) chromium nitride on the hardening reaction. This appears to be evidence that lattice straining increases the rate of nucleation of the hardening constituent. Some new observations on 885°F hardening are reported here. They show an effect of preheat treatment that should contribute to a better understanding of the 885°F hardening phenomenon. They also clarify a discrepancy which exists in the literature. Some investigators have reported most rapid hardening at 885", whereas others have reported it at 930°F. The present work also shows that 885°F hardening does not occur in electrolytic chromium, and that any long range ordering type of reaction affecting any sizeable part of the volume is unlikely. Materials Studied Table I shows the currlposition of the alloys used in this investigation. In these alloys carbon and nitrogen are present in roughly similar amounts. Presumably both elements precipitate, as carbides and/or nitrides, during the heat treatments given.

Jan 1, 1958

By Raynor Linzey, Karl M. Busen

The formation of thin films of silicon oxide by anodic oxidation of silicon and the subsequent removal of these films by an etch is a process often used for the evaluation of concentration distributions Profiles) in silicon layers by the differential sheet conductance method. The accuracy of the resulting profile is very strongly influenced by the uniformity of the thickness of the reacted silicon. Normally, it would be expected that for a constant number of coulombs passed the thickness would be the same from oxidation to oxidation. Investigations show that in certain electrolytes, for a given number of coulombs passed through an n-type silicon sample, the thickness of the reacted silicon increased with increasing resistivity. Even for the same resistivity the thickness varied sometimes by a factor of 1.5. When an electrolyte was used which consisted of 10 pct water by volume in ethylene glycol with 4.0 g KNO per 1000 ml of solution, anodiza-tion at 5 ma per sq cm led to satisfying results. Short-time anodizations gave oxide layers of a higher apparent density than those experienced from thermally gown silicon oxides. THE functioning and the electrical characteristics of semiconductor devices are based upon the incorporation of "impurities" into a single-crystalline body of suitable material and on the concentration distribution (profile) of this impurity. The incorporation can be achieved by well-known processes as, for example, by diffusion, epitaxial growth, alloying, or ion implantation. Often the profile resulting from these processes is not known. A powerful tool to learn about a concentration distribution is given by the method of differential sheet conductance which employs successive four-probe measurements on a layer subjected to stepwise removal of thin sublayers. Differential sheet conductance vs position (or penetration depth) of a sublayer is plotted and a smooth curve is drawn through the data. From this curve the profile is then calculated. When the semiconductor material is silicon, the sublayers are removed suitably by anodic oxidation of the silicon and subsequent dissolving of the formed silicon oxide by an etch. The accuracy of the resulting profile is very strongly influenced by the uniformity of the sublayer thickness. Normally, it would be expected that, for a constant number of coulombs passed, the thickness would be constant from oxidation to oxidation. Investigations showed that for sublayers several hundred angstroms thick the reproducibility can be rather poor. Therefore, efforts were made to obtain a reliable technique for uniform removal. The present paper describes such a technique and certain phenomena which were encountered during the investigations. APPARATUS AND TECHNIQUE The first report on the investigation of concentration distributions, where for differential sheet conductance measurements thin silicon sublayers were removed from a diffused layer by anodic oxidation, was given by Tannenbaum. The author reports the removal of sublayers which for the most part were 400 thick. More advanced device designs now require much narrower layers. When it was tried in these laboratories to determine profiles within such layers, difficulties were encountered with respect to sublayers which by necessity had to be thinner than the ones reported by Tannenbaum. The apparatus used for the investigations is sketched in Fig. 1. Two cylindrical containers connected by a wide tube are filled with an electrolyte. The left container receives the cathode whereas the right container is closed at the bottom end by a sample support consisting of a Teflon base and a copper pedestal. The silicon sample (1 by 1 cm) is mounted to the pedestal embedded flush in the Teflon base using silver paint (Degussa) for electrical contact. Pyseal is applied to the edges of the sample to protect the copper pedestal from the electrolyte. The base is mounted to the container using a water-tight silicon rubber gasket. Fig. 2 gives a view of the sample support. The copper pedestal is connected to the positive side of a power supply operating at a constant current output (Kepco Model ABC 425M). The electrolyte which has been reported by Duffek et al. consisted of either 2 or 10 pct water by volume in ethylene glycol and 4.0 g KNO3 in 1000-ml solution. The electrolyte is best prepared

Jan 1, 1967

By John S. Crandall

Occurrence: small crystals in alluvial sands from the eroding Belt Series mica schists. Flowsheet: dragline, trommel screen, jigs, drier, crusher, screens. Value: ground, $2.50 per cu yd, garnet sand gross $60. per ton. Costs: production and sales $48. per ton. Uses: blasting sand in aircraft plants, monumental works, foundries. Efficiency comparison: superior to silica sand. Future: possibilities only touched upon, research continuing.

Jan 1, 1950

By John F. Abel

"The most conservative persons I ever met are college undergraduates." Woodrow Wilson said that in 1905. No one is saying anything like it today. Chaos on the campus was a cliche of the sixties. Since 1905, education has expanded in every direction. Many more people are being educated for much longer periods of time. The school-leaving age has risen from 14 years to 20 years, on an average. Many are in school until after their 25th birthday. On the surface this situation appears all to the good. Our technical society needs a massive yearly infusion of semitrained (or educated, if you prefer) new blood. The efficiency of our economy and our standard of living are tied to high individual productivity which can be achieved only with an educated work force. Our democratic institutions are said to be founded on an educated electorate.

Jan 1, 1970

By AIME AIME

REGISTRATION and licensing of engineers is now being given consideration by a special committee of the Institute, authorized at the March meeting of the Board of Directors. The subject is one that has recently been or is now actively before engineering organizations in many of the States of the Union. In Washington, D. C., the Washington Society of Engineers and the local sections of ten national engineering societies, including the A.I.M.E., recently had a joint committee investigate the subject: this committee formulating a proposed law that has been presented to Washington engineers for their consideration. At the same time, the committee has summarized the reasons for and against registration of engineers in Washington, D. C. As many of these reasons are of more than local application, they are here reprinted so that all members of the A.I.M.E. may be informed on the subject. It is expected that some report of the Institute&apos;s Committee on Registration, State Councils and Professional Development will he made at some forthcoming meeting of the Board of Directors.

Jan 1, 1932

By Richard F. Hinds, F. O. Reudelhuber

Application of the conventional depletion drive calculation methods to volatile oil reservoirs results in erroneous estimates of ultimate recovery. In view of the increasing number and importance of volatile oil reservoirs, a special technique has been developed which will result in more realistic predictions using laboratory data obtained from reservoir fluid studies of a specific type. The experimental data are designed to permit continuous material accounting and, therefrom, provide the hy-clrocarbon composition of both the flowing oil and gas phases. The resultant well-stream composition data are then used directly in surface recovery calculations utilizing equilibrium ratios. A step by step procedure, specifically designed for routine use by the practicing reservoir engineer, is presented in an appendix. An actual study performed on a deep Mid-Continent reservoir is used ay an il-lustrathe example. INTRODUCTION It has been a practice for many years to utilize the conventional ma- terial balance methods in conjunction with relative permeability concepts for the prediction of recovery from solution gas drive reservoirs.&apos; Those who have performed such calculations recognize that compromises of several types are necessary in order to reduce the calculations to a reasonable degree of complexity. The most serious assumption involved results from the necessity of treating the produced oil and gas as separate fluids, independent of each other in their behavior. It is further assumed that the gas which is evolved in the reservoir as a result of pressure decline will not yield liquid upon the reduction of pressure and temperature resulting from production through surface equipment. Although these shortcomings have been recognized,&apos; it has been difficult to attempt refinement of calculation procedures since the laboratory data available normally were not of the proper type or extent to permit such calculations. Three general procedures have been available for depletion drive calculations when laboratory fluid data are of the conventional type. Differential Procedure The most simple, and most widely used, method requires use of the formation volume factor and gas sol- ubility data obtained from a differential liberation performed at reservoir temperature. This procedure ignores the differences existing between the fluid behavior in the reservoir and its behavior as it is produced through surface separation equipment. The errors introduced are not serious when dealing with very low volatility fluids and this method may be utilized if the laboratory data indicate only slight differences between the differential data and the flash data obtained from separator tests. Modified Differential Procedure This method was developed when it became apparent that medium volatility fluids evidenced a wide difference between the flash and differential data. The differential data are adjusted by changing from a residual oil basis to a stock tank oil basis. All that is required is multiplication of the differential data by the ratio of residual oil to stock tank oil relative volumes existing for the original reservoir fluid at the determined saturation pressure. This procedure generally results in increased calculated ul-timate recovery; however, such results should be viewed critically. Upon examination it may become apparent that the results are influenced by errors in reservoir liquid

Jan 1, 1958

By J. E. Johnson

The description of the machine which coilstitutes the subject of this paper is best iutroduced by a statement of the conditions which led to its construction, which may be briefly given as follows : The ore handled at the plant to be here described* is of the variety sornetimes called by those familiar with the brown ores of the South, " Mountain," as distinguished from the " Lime-

Jan 1, 1899

By A. W. Schlechten, W. J. Kroll

As this paper is written, the only method for the commercial production of lithium metal is by the fusion electrolysis of LiCl-KCl mixtures, as first proposed by Guntz.2 The details of the industrial process have not been made public but Osborg8 stated that an efficiency of more than go pct is obtained with a lithium metal recovery above 95 pct and that the metal is 99.5 pct pure. Pletenev9 gave a power consumption of 66 kw-hr per kilogram of lithium metal produced with a salt consumption of 9 kg of LiCl and 0.4 kg of KCI. Pletenev&apos;s figures indicate a somewhat lower recovery than that given by Osborg. In a recent report on German lithium plants, Motock7 gives figures that are also less favorable than those reported by Osborg. At the German plants the lithium recovery in electrolysis was only 83.4 pct, with a power consumption of too kw-hr per kilogram of lithium. The metal averaged only 97 pct pure, with sodium and potassium as the chief impurities. The presence of SO2, SO3, Si02, Ba, Ca, and appreciable amounts of Na and Fe2O3 were especially disturbing in the electrolysis, and it was necessary to run the cell for some time to eliminate most of these impurities and condition the bath. It may be noted here that most of these impurities do not interfere with a thermal reduction process. These facts show that the present method of producing lithium is fairly efficient and would suggest that other methods could not compete. However, fusion electrolysis has certain drawbacks, such as the necessity of supplying costly, low-voltage direct current and of collecting and processing the anodic chlorine if it is not to be wasted. An even greater disadvantage is that lithium chloride must be used for an electrolyte. It is one of the most expensive salts of lithium, since it cannot be produced in anhydrous form by precipitation from aqueous solution, as is done with LiF or Li2CO3. The reduction of lithium by a vacuum process similar to the ferrosilicon method for the production of magnesium would have certain advantages. Small units, such as Pidgeon retorts, would give flexibility of production to meet demand, and a small plant would require moderate capital outlay. There is a possibility of using idle Government-owned magnesium plants for such purposes. The raw materials needed for vacuum thermal reduction would not have to be extremely pure, especially with respect to the iron and calcium content. This paper describes a series of experiments to determine the effectiveness of various agents for the reduction of lithium compounds. The investigation is part of a program of vacuum metallurgy con-

Jan 1, 1947

By William P. Jones

THE consumption of sulphuric acid, one of the most important commodities in our modern industrial world, is often used as a barometer for industrial activity. The economics of acid manufacture are largely dependent upon the location of the place of consumption and the availability of raw materials in that locality. Sulphuric acid is made from SO2 oxygen from the air and water. Therefore the sulphur dioxide is the only raw material to be considered in an economic study. SO2 can be obtained from almost any material containing inorganic sulphur, such as elemental sulphur, pyrites, coal, sour gas and oil, metallurgical gases, waste gases, or gypsum and anhydrite. Many tons of acid can also be reclaimed by the recovery and concentration of spent acids. The aim of this paper is to present a guide to the economic aspects to be considered when the installation of an acid plant is contemplated. It must be remembered that 1 ton of elemental sulphur produces 3 tons of sulphuric acid and that the shipping of sulphuric acid by tank car is very costly. The size of the plant must also be given careful consideration. For instance, operation of a plant producing 5 tons of acid per day might be warranted in Brazil or Pakistan, whereas economics usually favor buying quantities up to 50 tons per day for use within the United States. Elemental sulphur, when available at the low price of 1 ½ ¢ per lb delivered at an acid plant, has always been the raw material most frequently used for sulphuric acid. All conditions favor its use at this price. The so-called sulphur shortage has been the subject of so many technical papers, magazine articles, and newspaper items during the past year that it hardly seems necessary to mention it again, but a very brief review of the matter will serve as a foundation for the discussion that follows. There is no shortage of sulphur. Only a shortage of low-cost Frasch-mined brimstone exists today. Other more expensive sulphur-bearing materials are plentiful, both in the United States and abroad. The low cost of Frasch-mined brimstone has discouraged the development of higher cost sources. However, the approaching depletion of Gulf Coast dome deposits and the greatly increased demand for sulphur here and abroad have made it necessary for industry to prepare for conversion to utilize sulphur in other forms. For future planning this situation must be considered permanent and not temporary. This conclusion is based on the fact that although sulphur demand will continue to rise, the production of Frasch-mined sulphur probably will not increase greatly beyond its present level of about 5,000,000 long tons per year. The International Materials Conference in Washington estimates 1952 requirements of the free world at nearly 7 ½ million long tons; and the Defense Production Administration has recently set a new goal for 8,400,000 long tons annual domestic production by 1955. The total sulphur equivalent produced in this country in 1950 was 6 million tons. What, then, are the alternatives for the manufacture of the vital chemical, sulphuric acid? Today about 85 pct of this country&apos;s sulphur, and nearly 50 pct of the world supply, comes from our Gulf Coast salt domes and is extracted from the earth by Frasch&apos;s hot water process. The Gulf Coast salt dome deposits have been the most important known natural deposits in the world, producing 90 million tons of sulphur during the past 50 years. However, at the present rate of extraction these deposits cannot be expected to last indefinitely. Pyrites Pyrites are, and have been for many years, the source of more than 50 pct of the world&apos;s sulphur requirements. The principal use, of course, is in the manufacture of sulphuric acid. The use of pyrites in the United States has diminished greatly because of the availability of low cost native sulphur, but pyrites have continued a major source of sulphur in many other countries. The most available pyrites for use in this country are in the form of lump pyritic ore and in mill tailings from flotation of other minerals such as lead, zinc, copper, gold, and silver. An important factor, when the use of pyrites for acid manufacture is being considered, is the disposal of calcine. A ton of sulphuric acid requires approximately ¾ ton of high-grade pyrite and results in ½ ton of calcine. If the calcine is a fairly pure oxide, free of harmful impurities, it can be used, after sintering, in an iron blast furnace burden. Its value might be as high as 15¢ per unit of Fe at the blast furnace; or possibly $10.00 per ton of sinter, if it assays 65 pct Fe. This might result in a credit of $4.00 per ton of acid if the sintering plant and blast furnace are both located adjacent to the acid plant. On the other hand, several factors must be considered before this credit can be realized, i.e., freight to blast furnace, availability of sintering facilities, methods of eliminating impurities, and the removal of valuable metal values. In some locations it would be most economical to dump the calcines.

Jan 1, 1952

By R. A. Young

Zinc metal production in the operating plants in the United States during 1948 was approximately equal to that of the year 1947, although new developments during the year assure higher output in 1949, if economic conditions are favorable. In the Western plants, the man-power shortage was almost completely overcome and new capacity has been or is in the process of being added to three plants; thus by December of 1948 daily zinc metal production had risen to the highest point since May of 1944 despite strikes in one large primary smelter and in one secondary plant.

Jan 1, 1949

By E. S. Leaver

The authors of the paper above mentioned have sent the following statement to correct erroneous com-ments and implications in their article with the re-quest that it be published: "In the above mentioned article the reference to Bendelari jigs is used in the generic sense as applying to the mechanically driven diaphragm jigs. No attempt was made to dif-ferentiate between the various machines as installed on different dredges. The Natomas Company use a jig of their own manufacture. The Yuba Company installed the Placer jig as manufactured by the Pan American Engineer-ing Company. "The Pan American Engineering Company also manufactures the Crangle jig under their own name. This is a diaphragm jig in which the pulsations are produced by intermittent flow of water through the patent Crangle Valve and it has no driving mechanism."

Jan 1, 1937

Note Any member who desires to be designated as being "Available for Consulting Work" can arrange it simply by sending a written request to the office of the Secretary of the Institute The following list of members is primarily arranged geographically, with secondary consideration to political subdivisions arranged alphabetically First, the states of the United States , then other North America, in order Alaska, Canada, Mexico, the West Indies, and Central America Then cones South America, Europe, Africa, and Asia, each including the near by islands associated with those continents Australia, the islands to the north, and the Pacific islands except Japan are grouped together under Oceania The various countries are indexed on the preceding page NORTH AMERICA UNITED STATES ALABAMA America -Dyar, G C Anniston -DePriest, S H Klugh, B G Lefforge, J W Auburn Poor, R S Bankhead -Armstrong, W D Bessemer -Beck, A IV, Jr Carnes, D Chabot, L S , Jr Creveling, J C

Jan 1, 1952

By D. H. Baldwin, R. E. Reed-Hill

WITH the polarized-light microscope, the basal-plane trace may be located on hcp crystal surfaces to an accuracy of approximately 1 deg. This determination can also be made on very small crystalline areas, approaching a micron in width. Measured basal-plane trace distributions on selected specimen surfaces can yield1,2 valuable texture information. However, the polarized-light microscope is probably best suited to orienting

Jan 1, 1965

By Marston G. Fleming

CRITICAL pH has been defined by Wark1 as that pH value below which a mineral will float and above which it will not float in solutions containing a given concentration of collector but free from other depressants or activators. - The relationship between mineral, collector concentration, and pH is expressed in the form of a critical pH curve determined by the captive bubble method and is generally regarded as being fundamental to the system involved. The mechanism of alkali depression is currently in dispute, two general theories having received authoritative support. The view expressed in Taggart&apos;s chemical theory of flotation2 is that in the presence of a critical concentration of hydroxyl ions, all the metal ions available at the surface of the mineral are present as anions of the form [M (OH)x]-y. The formation of the necessary metal xanthate is thus precluded and, furthermore, any metal xanthate coating previously formed, at a lower pH, will be dissolved. Gaudin3,4 and the Melbourne school under Ware hold that alkali depression is caused by the preferential adsorption of hydroxyl ions by the mineral surfaces. This paper describes an investigation of the mechanism of alkali depression in each of the three systems: cerussite-aqueous carbonate-xanthate, cerussite-xanthate, and galena-xanthate. Alkali Depression of Cerussite by Control of Carbonate Ion Concentration Wark and Cox6 have shown that in the presence of Na2CO3 a higher concentration of xanthate is required to effect bubble contact with a cerussite surface than in carbonate-free solutions. To examine this depression of cerussite by sodium carbonate, a series of captive bubble tests was carried out on cerussite specimens in solutions containing 100 mg per liter of potassium ethyl xanthate and varying concentrations of sodium carbonate. The pH was adjusted by the addition of dilute hydrochloric acid. For purposes of comparison a standard critical pH curve was determined for cerussite with potassium ethyl xanthate in solutions containing no added carbonate. In the latter case pH adjustment was made with sodium hydroxide. The experimental method employed in both series was broadly similar to that described by Wark and Cox;7-9 a number of refinements suggested by Sutherland10 were adopted, and the procedure was further developed and modified to suit the particular requirements of the investigation. The relationship between pH and the concentration of potassium ethyl xanthate necessary to induce bubble contact at cerussite surfaces is shown in Fig. 1. The relationship between pH and the concentra- [ ] tion of sodium carbonate necessary to prevent bubble contact at cerussite surfaces in the presence of 100 mg per liter of potassium ethyl xanthate is shown in Fig. 2. Comparison of the. two curves shows that at a collector concentration of 100 mg

Jan 1, 1952

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

Recent publicationsl.2 establishing the presence of cross-slip in strained metallic single crystals oriented wholly within the area of single slip as predicted from the generalizations of Taylor and Elam3 described these markings as they appeared during the initial stages of the deformation process. At that time, the plane having a common glide direction with the primary slipping plane was reported as the cross-slip plane although the specific direction was not confirmed. Consequently, in continuation of the research, it seemed advisable to investigate the micro-graphic appearance of cross-slip together with the Laue back-reflection X ray analysis and stress-strain data during the later stages of the deformation process. Accordingly, a single crystal of brass (72.75 pct Cu, 0.01 pct Fe, 0.01 pct Pb, 27.23 pct Zn) was polished mechanically and repolished electrolytically after the manner described in the earlier paper.&apos; Three pairs of flat surfaces, parallel to the specimen axis, and (1) perpendicular to the plane containing the pole of the primary glide plane and the specimen axis, (2) perpendicular to the plane containing the pole of the cross-slip plane and the specimen axis, and (3) perpendicular to the plane containing the slip direction and the specimen axis, were polished mechanically and repolished electrolytically, resulting in a final minimum gauge diameter of 0.4864 in. in a gauge length of 3.36 in. The specimen was elongated in tension and load-extension readings were taken following the method described in the initial investigation.&apos; Observed reorientations were obtained from a series of Laue back-reflection photograms at the center and ends of the gauge length and at various positions around the circumference of the specimen. These were interpreted after the manner of A. B. Greninger.4 Cross-slip (Fig 1 and 2) was found with the first appearance of the primary slip clusters and usually joined members of these clusters. In addition, a third set of entirely different markings (Fig 3) could be noted. The displacement of this third set by the primary slip lines was measured as 8300 at. diam (3.04 microns). Since the specimen was carefully observed at high magnifications before any deformation and no markings of any type could be noted, it would appear that this third set was formed during the deformation process prior to the initiation of classical primary slip. Additional extensions produced no unusual change in the appearance of either cross-slip or the third set of markings. The number of lines increased with increasing elongation and appeared, generally, in areas where earlier markings were present. The continuity of the clusters of cross-slip lines in Fig 4, 5 and 6 illustrates that they are neither noticeably displaced by nor do they displace the primary lines at this stage. In Fig 7, cross-slip appears in a long narrow localized band approximately 45 degrees from the stress axis. This somewhat resembles a twin band except for the lack of a sharp boundary. After a shear of 0.257, suffcient additional glide occurred on the cross-slip plane to displace the primary slip lines (Fig 8). Generally, where a large number of cross-slip lines could be observed in an area on one flat surface, few cross-slip lines appeared on the diametrically opposite position on the parallel flat (Fig 9). These, of course, were not matched observations on the same glide ellipses. It was extremely difficult to make such comparisons. The third set of markings (Fig 10) was extensively displaced by glide on the primary slip planes. A plot of the width of primary slip clusters versus their displacement of the third set of lines is shown in Fig 11. The slope and the linearity of the plot suggest that each primary glide plane slips to a constant maximum value of shear before further slip is transferred to another plane. A shear value of 0.28 was determined in this case. Heidenreich5 has presented a similar schematic representation of glide for aluminum. After the specimen had attained an elongation of 51.8 pct, corresponding to a shear of 0.973, cross-slip appeared very prominently in certain areas as shown in Fig 12, yet at diametrically opposite positions very little cross-slip could be noted, Fig 13. Classical conjugate slip was found at this advanced stage in the deformation, Fig 14, which corresponds to the axial location shown at 12 in Fig 15. It should be noted that cross-slip occurs within the conjugate slip clusters and on the same plane as the cross-slip associated with the closely spaced primary lines which constitute a background in less distinct focus. The third set of markings noted at all stages in the deformation of the

Jan 1, 1950