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By R. N. Orava, L. A. Rice

One of the difficulties encountered in the preparation of titanium specimens for transmission electron microscopy is the formation of a surface hydride phase during the thinning operation at ambient temperatures. This necessarily destroys contrast, obscures features of interest, and often leads to misleading results. By cooling the polishing solution to temperatures below 0°C this problem has been overcome in the past.' However, since the cooling procedure is somewhat inconvenient, a technique was developed at this laboratory for thinning titanium at room temperature. The material examined was A-70 grade commercial-purity titanium purchased from the Crucible Steel Co. of America. The mechanical and thermal treatments, described elsewhere,* yielded a recrystallized grain size of 4 to 5 p. A slice, 0.5 mm thick and 1.5 mm wide, was cut from a bulk specimen2 using a diamond cut-off wheel. The sample was then coated with paraffin wax. Two concentric holes, about 0.03 in. in diam, one at each broad face, were scribed through the wax to the surface of the metal. Subsequent polishing for several minutes resulted in a preferentially thinned or "dimpled" region. Thereafter, the wax was removed and the entire specimen polished to the point of breakthrough at the base of the dimple. Polishing was effected chemically in a solution comprised of 30 pct HF and 70 pct HN03 by volume, kept at room temperature (20" to 25OC). The specimens were mounted in a stereo holder and examined at 100 kv in a Philips l00 B Electron Microscope. A micrograph from a foil prepared in this way is shown in Fig. 1. Several points are noteworthy. This electron micrograph shows neither evidence for the formation of a hydride phase due to specimen preparation nor, moreover, any obvious surface contamination in electron-transparent areas of a freshly prepared foil. Localized variations in foil thickness observed in some specimens seem to be a characteristic of this chemical polish but do not seriously detract from foil quality. With care, the lifetime of a good specimen exceeded 2 hr in the beam. On the other hand, the exposure of a sample to air at atmospheric pressure, when still warm from the beam, clearly resulted in the deterioration of a formerly clean area just previously in the field of view. An example in Fig. 2 of a contaminated region reveals features, and "spots", not unlike those observed in much purer material by Yamane and Ueda. Consequently, one can conclude that: 1) titanium can be thinned satisfactorily in a solution at room temperature for transmission electron microscopy; 2) large-scale precipitates, >50A in diam, are absent in commercial-purity, recrystallized, furnace-cooled, A-70 titanium containing about 3800 wt ppm interstitials and the same amount of iron; 3) care must be taken not to attribute surface contaminants to precipitates. The authors are grateful to the Franklin Institute for financial support and permission to publish.

Jan 1, 1967

S. LE FEVRE, Forest Glen, N. Y. (communication to the Secretary*).¬F. L. Nason thinks I could not have studied Mr. Witherbee's paper and doubts the arithmetic used, but in his discussion arrives at practically the same conclusion. He says 10 ft. thickness of ore over a square mile should give 27,878,400 tons, allowing 10 cu. ft. per ton of ore. This is correct, but if he reads carefully he will see that this depth of ore was figured as covering one-tenth of the surface, which reduces the figures to those used by Mr. Nason. I did not say, however, that there were 2,300,000,000 tons of ore in New Jersey, but that applying the same method of computation as used by Mr. Nason, to the area of the iron ore-bearing gneisses in New Jersey, we would get a total of 2,300,000,000. I did say, "In this area are located 366 magnetite mines that have been worked more or less. These lenses may easily be capable of producing (on an average) 1,000,000 tons each, and there are probably double the number listed not opened up." Thus my estimate for New Jersey, as far as any was made, would be: Probable ore 366,000,000 Possible ore in addition 732,000,000 1,098,000,000 Mr. Nason's final conclusion of his personal estimate was one-half of what he erroneously read to be the estimate given in the paper, or half of 2,300,000,000, which equals 1,150,000,000. So the two estimates seem to differ less than 5 per cent., and we have the two sister States of New York and New Jersey on an equal footing of productive possibilities in magnetic ore.

Jan 6, 1917

By Frederick J. McGarry, Fred Moavenzadeh

An experimental investigation of the thermal and mechanical responses of rock materials to laser radiation is described. Specifically, the following three topics have been studied in detail: 1. Temperature measurements on thin discs subjected to laser radiation. 2. Strain measurements on thin discs subjected to laser radiation. 3. Observation and evaluation of cracking and spalling phenomena in constrained and unconstrained thin discs respectively, subjected to laser radiation. In conjunction with the experimental work done, use was made of a heat flow analysis and a stress analysis program developed for this purpose. It was possible to theoretically predict the thermal and mechanical responses of a rock specimen to laser radiation and then compare them with experimental observations. Good correlations were obtained.

Jan 1, 1971

By T. L. Joseph

A study is made of the amount of solution loss necessary to maintain the reducing power of the gas stream in the blast furnace. Curves are presented to show the effect of solution loss, moisture in the blast, and carbon dioxide from the flux on the nitrogen in the THE blast furnace process is based upon the counter flow of gases and solids. As CO, N, and H, flow upward from the combustion zones, oxygen is acquired from the descending charge. In the reduction of iron ore, a portion of CO is converted to CO, and similarly a portion of H, is converted to water vapor. The inert N,, from the air used in combustion, passes through the furnace with little change. Its concentration is, however, decreased by reactions such as direct reduction and solution loss which increase the volume of CO in the gas stream; Similarly the evolution of C02 from the limestone also dilutes the nitrogen. he purpose of this paper is to illustrate an idealized and simplified method of studying furnace processes by following changes in the gas phase between the tuyeres and the stock line. A more specific objective is to evaluate the effect of solution loss upon the CO/CO, ratio in that region of the furnace in which FeO is reduced to metallic iron. This last stage of reduction requires relatively high CO/CO, ratios to exceed the equilibrium requirements. Solution loss or the reaction of COZ with C to produce CO has a pronounced effect upon the ratio of the carbon gases and is necessary to maintain the reducing power of the gas stream if the consumption of coke is low. It will be explained later that indirect reduction followed by solution loss is stoichiometri-cally equivalent to direct reduction. Calculations will be made to show how the composition of the gas in the region of the mantle varies with coke consumption and with different amounts of solution loss. Such calculations show the condi- tions under which gasification of C with oxygen in the charge is needed to maintain the reducing power of the gas. Equilibrium conditions for FeO and the carbon gases will be used to establish a minimum CO/CO, ratio below which reduction will not proceed. The manner in which carbon is gasified in the furnace, at the tuyeres with oxygen in the air or above the tuyeres with oxygen from the charge, will be a basic feature of all calculations. It is hoped that greater interest in the use of top gas as a means of following furnace reactions will be aroused by the calculations and generalized curves which are presented. Bosh Gas Equations Subject to some alteration by the amount of moisture in the blast and by direct reduction, the gas leaving the combustion zones of a blast furnace has a definite composition. Because a relatively small amount of oxygen is acquired from the charge in the bosh and in the crucible, the products of combustion undergo little change until they enter the shaft. Bosh gas is, therefore, essentially the products of combustion of carbon in a deep fuel bed with air. The relative weights and volumes of reacting materials are expressed by the equation: 2~ + 0? + 3.76N, = 2C0 $ 3.76NZ [I] Air Bosh Gas -air = 79% N? = 3.76) 21% 02 Starting with a known mass of C consumed largely by air, Eq 1, but partly by water vapor, Eq 2, the volume and C + H2O = CO $ H? [21 composition of the bosh gas can be calculated and subsequent changes followed as reactions take place at various elevations in the furnace. As shown in

Jan 1, 1952

By Wilbur Nelson

THE year 1923 has been a dull period in oil development in Kentucky and Tennessee, with the exception of the Kettle Creek area along the Tennessee-Kentucky line, in Clinton and Cumberland Counties, Kentucky, and Clay County, Tennessee. The price of oil during the year has been so low that wildcatters have shown little interest in drilling. At the beginning of the year, light oil sold for $2.31 per barrel and medium oil for $2.06 per barrel. Prices increased to the highest point for the year in February, when light oil brought $2.86 per barrel and medium oil, $2.61. In April, prices had declined 35 c. while in May an additional decline of 25 c. went into effect. During June, prices declined 20 c. per barrel; during July, 45 c. per barrel; remained stationary during August and September, and dropped during November and December to the low price of $1.36 per barrel for light and $1.21 for medium oil. At present, an increase of 29 c. has brought the price of light oil up to $1.55, and indications are that the price will continue to increase during the coming months. It can readily be seen that during 1923 the price of oil was such as to prevent any drilling except that necessary to hold leases and to maintain production enough to take care of overhead expenses.

Jan 3, 1924

By T. N. Andersen, K. J. Richards, C. N. Wright

The kinetics of the important reactions occurring in an electrowinning cell have been determined. This information has been used to quantify relationships between the operating variables of current density, solution composition, agitation, and temperature and the resulting current efficiency and deposit quality. Analysis of these results has shown (1) the importance of dissolved iron in determining maximum possible current efficiency and corrosion rate at the cathode suspension loop, (2) the role of agitation, current density, inert salts and temperature in*determining deposit quality and (3) the effects of non-uniformity in the hydrodynamic conditions from the bottom to top of the cell. The significance of the results of this study to the operation of a commercial plant directly treating acid leach solutions is discussed.

Jan 1, 1973

By B. B. Kunkle

The history of this refinery has been one of expansion. It now has the capacity to produce 240,000 tons of cathodes annually. A general flowsheet and descriptions of the plant layout, operations involved, and equipment used at one of the world's largest and most modern electrolytic copper refineries are presented. THE El Paso copper refinery of Phelps Dodge Refining Corp. was originally constructed by the Nichols Copper Co., in association with Phelps Dodge Corp. and the Calumet & Arizona Mining Co., in order to refine anode copper produced at the smelters of the two latter companies. Initial production was obtained from the plant in January 1930 and its annual refining capacity was 100,000 tons of anodes. In order to keep pace with Phelps Dodge Corp.'s increasing copper production in the Southwest, it became necessary in 1937 to increase the El Paso plant's refining capacity to 160,000 tons of cathodes annually. This was accomplished by adding two sections to the electrolytic tank house, increasing the number of anodes placed in each commercial electrolytic tank from 33 to 37, and making changes in the dc circuits which made it possible to put three generators on each of the two circuits instead of two, thus increasing the amperage on each circuit from 10,000 to 14,800 amp. The capacity of the two furnaces from which refined shapes were cast was increased by raising the sidedoor bays on the furnaces 6 in. An increase of 70 pct in the productive capacity of Phelps Dodge Corp.s Morenci Branch in 1942 again made it necessary to expand refining capacity. In order to accomplish this, Defense Plant Corp. set up a project to increase the capacity of the El Paso plant to 240,000 tons of cathodes annually. This project consisted of enlarging the tank house approximately 50 pct, the construction of another wire- bar furnace, and corresponding increases in other departments where necessary. The engineering work on this expansion was begun in March 1942. Actual construction was under way by August 1942, and the work was completed by March 1944. These additional facilities were purchased from Defense Plant Corp. by Phelps Dodge Refining Corp. in August 1949. The plant is in El Paso about eight miies east of the center of the city and near Highway 80 and the main lines of the Southern Pacific and Texas & New Orleans railroads. The plant site covers approximately 494 acres of company-owned land that is ideally adapted for its use, being well-drained sandy soil and having enough slope so that a minimum amount of excavation was required when the plant was constructed. There is still ample room on the plant site for any future plant expansion. The plant is constructed on four different ground levels and so arranged that the unrefined copper is unloaded on the highest level at the north side of the plant and the refined copper is shipped out from the lowest level on the south side of the plant. The receiving or unloading platform, weighing and sampling rooms, main floor of the tank house, acid and condensate storage tanks, and the slimes and copper sulphate plants are on the first or highest level. The tank house basement, yard scales, charging and furnace bays, balloon flue and stack, brick-storage building, substation and power house, boiler feedwater treating plant and pump house, water storage tanks, and change houses are on the second level. This second level also contains ample yard area for setting-up furnace charges, and for storage of custom scrap, cathodes, scrap anodes, blister, coke, and poles. The casting wheels, inspection conveyors, cathode shears, wire-bar scalping machine, slag

Jan 1, 1952

By Strathmore R. B. Cooke, Iwao Iwasaki, C. S. Chang

PYRRHOTITE has long been considered a gangue mineral to be eliminated as tailing in the treatment of various sulphide ores. However, in recent years the world-wide lack of sulphur resources has called attention to this mineral as a potential source of both sulphur and iron. Its importance as an economic mineral, however, has not been particularly emphasized. For this reason very little is known about its response to flotation, except that it can be depressed easily in alkaline circuit, by long aeration,1,2 addition of oxidizing agents3 or by starch.4 The object of this work was to study the floatability of pyrrhotite. This includes the effect of oxidation by aeration, of copper activation, and of change in pH.

Jan 2, 1954

By Robert T. Ault

The nature of fracture in unnotched tensile and notched tensile sheet and round specimens and V -notched and precracked Charpy-type sheet specimens of both wrought stress -relieved and re-crystallized molybdenum was investigated over the temperature range of -78° to 300°C. The sharp rise in fracture stress, for unnotched tensile samples, as the temperature is increased above the brittleness transition temperature (Tb), is found to be a result of an increase in flow stress due to plastic constraint and an increased strain rate which results from the onset of necking at Tb . Quasi-brittle fracture in notched tensile samples is found to occur when the tensile stress at the elastic-plastic interface, beneath the root of the notch, reaches a maximum critical value, which is independent of test temperature over the range from —78° to 25°C, but dependent on microstructure. In the temperature range between 150° and 300°C, unnotched tensile and notched tensile samples alike are found to fracture by a ductile fibrous tearing process which is discontinuous in nature, as a result of the competition between the processes of tearing, through continued plastic flow, and local work hardening. Results from the V-notched and fatigue-cracked Charpy-type impact tests demonstrate that crack initiation is the governing factor in the low-temperature (-78° to 25°C) fracture process for molybdenum. In recent years, there has been considerable interest, and a commensurate number of investigations, concerning the duc tile-to-brittle transition in refractory metals. There has not developed, however, a satisfactory explanation for the uniaxial tensile fracture-stress transition which accompanies the well-known ductility transition. This matter therefore warranted investigation. In a similar manner, the increased importance of notched tensile strength values in evaluating materials and in design criteria requires a better understanding of the factors which control the fracture behavior of notched tensile samples. In a previous investigation1 of the nature of initial yielding and fracture in notched sheet molybdenum at room temperature, it was suggested that plastic constraint was the controlling factor in governing the fracture behavior of notched samples. The final portion of this investigation was concerned with the fracture toughness of molybdenum. Of particular interest was the comparison of effective surface energies for fracture in V-notched samples with fatigue-cracked, Charpy-type samples in order to ascertain the relative importance of the initiation and propagation phases of the fracture process. MATERIALS AND TEST PROCEDURE Sheet tensile, notched tensile, and V-notched Charpy specimens were prepared from 50-mil, stress-relieved molybdenum sheet.* Half of these specimens were vacuum-annealed for 1 hr at 1200°C and 7.5 x l0-5 Torr and furnace-cooled to produce a relatively uniform grain size of 0.30 mm diameter. Round notched and unnotched tensile specimens were prepared from warm-rolled and swaged 5/8-in.-diam bar.* These specimens were vacuum-annealed for 1 hr at 1350°C and 5 x lom5 Torr and furnace-cooled to produce a grain diameter of 0.11 mm. Material analyses in ppm were: C N O H Sheet 290 10 4 1 Bar 50 30 30 2 The unnotched tensile sheet specimens had a 1/4-in. gage width and a 1-in. gage length. The unnotched tensile round specimens had a 9/32-in. gage diameter and a 1-1/4-in. gage length. The sheet and round notch tensile specimens are shown in Fig. 1. All of the notched tensile specimens tested were tandem-notched in order to study the location and mode of fracture initiation. The tandem-notched specimens were carefully machined so that the largest variation in notch depth on a single specimen was 0.001 in. Thus, when fracture occurs, the extent of plastic deformation that exists in the un-fractured notch section is that which exists just prior to fracture. All of the tandem-notched sheet specimens were electrolytic ally polished and chemically etched prior to testing. The V-notched Charpy-type specimens machined from the 50-mil sheet material had the standard dimensions of 2.125 in. long, 0.394 in. deep, and a 0.010-in. root radius. The unnotched tensile and notched tensile tests were conducted over the temperature range of -78° to 300°C, in a 10,000-lb Instron Universal Testing Machine, at a constant crosshead speed of 0.020 in. per min. The V-notched Charpy-type

Jan 1, 1964

By William B. Plank

ENROLMENT data given in this report of the seventh study of the schools by the Mineral Industry Education Division reveals the critical situation in the mineral engineering schools of the United States. Complete figures for the year 1942-43 show that at that time, about one year after Pearl Harbor, the enrollment of mineral engineers was 6385 or 30 per cent less than in 199441. By October 1943, however, enrollment had dropped to 2050, as reported in the Journal of Engineering Education of January 1944. This was a further reduction of 68 per cent in one year, or 77 per cent in three years. With accelerated programs in effect during the current year, with many graduations since last October, and with the military forces taking practically all the high school graduates, the present enrollment is, of course, much lower than the 2050 above given. There are no late data on the exact situation. In Canada, the same situation exists in the mineral engineering schools, only

Jan 1, 1944

By AIME AIME

A PAPER prepared by James A. Adams, development engineer of the fitline & Smelter Supply Co., and presented at the last Annual Meeting of the A.I.M.E. in New York City, de- scribed a new automatic pulp density controller which has had a most favorable reception. Manual control has until now been the universal practice in spite of its shortcomings; samples of pulp for density determination were often improperly taken, and only at the operator's convenience, so that the trend in density changes was frequently missed, and the grinding circuit al- lowed to operate under something less than the most efficient conditions.

Jan 1, 1940

By H. J. Booss

THERE is a considerable lack of data on thermody-namic properties of hard-metal alloys. Only two papers 1,2 give mean values of specific heat in an unknown temperature range; more recently the author3 gave more detailed information on the mean specific heat in the temperature range from 20" to -190° C.. EXPERIMENTAL 1) Method—Experimental procedure followed a method suggested by Oelsen and coworkers.4 It requires samples of some 100 g of weight. The time of measurement is prolonged (30 min) but one run allows the measurement of a lot of positions on the heat-content curve. Results4 were found to be in good agreement with "best values" given by kelley,5 Kubaschewsky and Evans,6 etal.

Jan 1, 1960

By Charles R. Wilson, Thomas W. Doe, Jane C. S Long, Howard K. Endo

An approach to treating flow through fractured rocks is presented which involves (1) determining statistical distributions for fracture area, density, orientation, and aperture from field data, (2) computer generation of fracture systems from the statistical distributions, and (3) analysis of the permeability and porosity of the fracture systems. The fracture density and orientation data my come from core logging or mapping. The hydraulically appropriate apertures and areas of the fractures come from transient flow analyses of single fracture well tests. These tests my also yield information on fracture deformability. Analysis of flow through computer generated fracture systems shows that an equivalent porous medium permeability can be defined for some fracture systems if a large number of fractures is taken into account.

Jan 1, 1982

By F. H. Willcox

THE CHAIRMAN (HENRY D. HIBBARD, Plainfield, N. J.).-This paper is timely because of the changed conditions due to the great war, but apparently its scope is limited to oxidation process steels. Referring to the four numbered observations on page 199: No. 1 seems to ignore Johnson's discoveries about oxygen in cast iron. No. 2 ignores crucible steel. No. 3 ignores red short steel containing enough gas solvents to make it solid, while No. 4 assumes that a deoxidizer is necessarily a gas decomposer or solvent and vice versa, which it not always is. From these observations it is deduced. that the only hole-forming gas in steel is an oxide of carbon (CO presumably is meant), which is not true.

Jan 4, 1917

By G. R. Frank, R. E. Willett, E. H. Hollingsworth

The most generally accepted equilibrium diagram for A1-Fe alloys has a eutectic system on the aluminum side with an essentially insoluble constituent of the formula, FeAl,, as the second phase. In 1938, Bradley and Taylor1 did report a phase change of FeAl,, but this change has never been confirmed. According to them, FeA1, is the stable phase only at higher temperatures; at lower temperatures, it is converted into Fe2Al7 and aluminum. It has now been found that there is, in fact, a phase change of the Al-Fe constituent on the aluminum side of the equilibrium diagram. This change, however, is not the one reported by Bradley and Taylor. The alloys used were cast by continuous processes and had these analyses: Fe - 1.98 to 2.02 pct, Cu-0.01 pct, Si - 0.01 pct, Mn - 0.01 pct, Mg - 0.00 pct, Zn - 0.00 to 0.01 pct, Cr - 0.00 pet, Ti - 0.00 to 0.04 pct. The constituent in these alloys was identified by X-ray analysis with a Guinier camera and by chemical and X-ray powder diffraction analyses. Two procedures were used to separate constituent for the last two analyses. In one procedure, it was separated by treating a sample with a solution of methanol saturated with iodine. And in the other procedure, it was separated by first applying, at 12 amp per sq ft in 15 pct sulfuric acid at 70°F, an oxide coating to a sample, and then dissolving this coating in a solution of 35 ml of 85 pct H3PO4 and 20 g of CrO3 per liter. Several observations directed attention to a phase change of the A1-Fe constituent. Differences that appeared too great to be accounted for by micro-structure alone were found in the voltages required to apply the same thickness of an oxide coating to products from rapidly and slowly chilled ingot. Even more striking was the difference in appearance of the coatings themselves. One applied to a product from a rapidly chilled ingot was dark gray in appearance, in fact, almost black, while one applied to a product from a slowly chilled ingot was essentially white. Also, even a short period of thermal treatment at an elevated temperature of products from rapidly chilled ingot led to the same anodizing behavior as that of products from slowly chilled in-

Jan 1, 1962

By Walter L. Crow

MUCH has been published on highly technical phases of grinding. Very little has been written on how a mill man can improve his operations by determining the optimum size assortment of grinding balls that should be added as a makeup charge. This ball rationing is not to be confused with the ball ration used as an initial charge when the mill is started up. Ball rationing is considered for one or more of the following purposes: 1) to increase throughput of the mill, 2) to reduce the power required per ton of ore ground to the desired size, 3) to reduce steel consumption per ton of ore ground, 4) to improve product size, and 5) to lower retention time of ore in the mill.

Jan 7, 1957

By Meredith Johnson

THE year 1924 saw little change in the production of oil and gas it either Pennsylvania or New York. In the early months of the year the price of Pennsylvania crude oil, $4.00 to $4.50 a barrel, was sufficiently high to cause operators to lay plans for rather extensive drilling opera-tions. But when, in August, the price dropped to $2.85 a barrel, there was no inducement for new work and drilling was curtailed. In spite of the curtailment, however, the combined production of the two states for the year showed a slight increase over 1923, the production being 8;859,000 bbl. in 1923, and 8,901,000 bbl.1 in 1924. The increased production was due entirely to. the continued development of flooding operations in the Bradford field, all other oilfields showing a decline for the year. TABLE 1. Production of Crude Oil in Pennsylvania and New York for the Last Ten Years a Production, Barrels Production, Barrels Year Year Pennsylvania I New York Pennsylvania I New York 1915 7,838,000 888,000 1920- 7,438,000 906,000 1916 7,593,000 874,000 1921 7,418,000 988,000 1917 7,733,000 880,000 1922 7,425,000 1;000,000 1918 7,408,000 809,000 1923 7,609,000 1,250,000 1919 8,137,000 851,000 1924 7,535,0006 1;366,0006 a U. S. Geological Survey figures. b Estimated. Much of the drilling in the southwestern part of Pennsylvania was done in search of gas. Natural gas in Pennsylvania is fast being recognized at its true worth and the increased prices allowed 'the gas companies for their product induced quite a bit of new work. The relative importance of natural gas compared with manufactured gas is shown in Table 2.2

Jan 3, 1925

By Barry S. Epstein

Financing the acquisition of a going coal mine operation has not had the exposure other finance-oriented projects have had. Therefore, C.I.T. feels that coal mining people and financial people should improve their understanding of the factors involved in this important type of acquisition. The discussion consists of two major subjects: analysis of the acquisition of the property, and sources and terms of funding the acquisition. Source and Terms of Funding There is a need to keep the competent medium-sized independent operator in the coal business, especially in these times of energy shortage. The creation of a resale market for coal mines encourages new investment in the coal mining business by medium-sized operators and their financial backers. Who provides debt and equity financing to acquire going coal mine operations and on what terms?

Jan 9, 1975

By Castle. J. E., J. L. Gillson

In this chapter there is a wide difference in the meaning of some words used for rock and mineral names as defined by scientists and tabulated in the "Glossary of Geology and Related Sciences," published in 1957 by the American Geological Institute, and the meaning as used by the commercial producers of feldspar. It is necessary, therefore, to define these terms giving both the "scientific" and the "practical" definitions. There is no ambiguity about the name feldspar itself. This is a general term for a group of related minerals which are silicates of aluminum, combined with sodium, potassium and calcium. The feldspars are the most abundant minerals of the igneous rocks, and since these rocks make up the largest proportion of the earth's crust by volume (although not of the actual surface area of the continental land masses) the feldspars are the most abundant minerals of all. The igneous rocks themselves are classified on the basis of the variety of the feldspar present. The potash feldspars, which are called orthoclase and microcline, are the dominant minerals of the granites and syenites, and of their fine grained equivalents, the rhyolites and trachites. The plagioclase feldspars form an isomorphic series, of which the sodic endmember is called albite, and the lime endmember, anorthite. The members near the sodic end, albite, oligoclase and andesine are the characteristic feldspars of the granodiorites and diorites, and of their fine grained equivalents, the dacites, and andesites. These feldspars-orthoclase, microcline, albite oligoclase and andesine-are the feldspars used commercially. Labradorite, a member of the plagioclase group, in which the lime exceeds the soda in the chemical composition, is the common feldspar of the gabbros, anorthosites, norites, basalts and other so-called "basic" rocks. Although some attempts have been made to use labradorite as a commercial feldspar, none is now used except as an ornamental stone. The mineral anorthite is very rare. Since the feldspar in most of the common igneous rocks is relatively fine grained, and mixed intimately with other minerals, from which it can be separated cleanly only with difficulty, most masses of the common rocks cannot be used as sources for the feldspar contained in them. It is only the rarer types of rocks in which the feldspar is very coarse-grained, or ones containing very little of the iron-bearing minerals which are objectionable impurities in commercial feldspar, that are quarried to yield an acceptable product. The most widespread type of such a rock from which commercial feldspar can be produced, is that called "pegmatite." These rocks are dikes and bodies of irregular shape and of a size measured in feet or yards in most cases, rather than in miles. They are more commonly associated with granites, rather than with other coarse-grained igneous rocks. Many of them contain crystals of various minerals, including the feldspars, that are much larger than are found in the host rock, the granite, and in many there are large masses of feldspar that are sufficiently free from iron-bearing silicates so that products acceptable to the ceramic industry can be produced, in some cases simply by hand sorting. Most of this feldspar in pegmatites, however, does contain intergrown quartz up to 25 pct. Pegmatites are so important, not only as commercial sources of feldspar, but also of other minerals which are produced com-

Jan 1, 1960

By R. H. Brown

EARLY workers attempted to study the structure of alloys by measurement of equilibrium electrode potentials in aqueous solutions containing ions of the metals from which the alloy was made.1 The method was subject to such limitations (e.g., the difficulty in attaining electro-chemical equilibrium at low temperatures) that it has not been widely used by metallurgists. Recently, Seltz and co-workers have introduced a greatly improved method for studying alloys by measurement of equilib-rium electrode potentials in molten salts.2-4 The mathematical treatment is the same, of course, as for equilibrium potentials of amalgams in aqueous solutions.5 This method will probably find extensive use, since it makes possible not only the deter-mination of phase fields of equilibrium diagrams but also the determination of certain thermodynamic quantities which can be used advantageously in metal-lurgical calculations. However, the method presents difficulties. With many metallic and alloy electrodes, reversibility is not readily obtainable. Also, the difficulty of obtaining suitable material from which to make the cells is increased as the temper-ature is increased. Moreover, the necessity of carrying out measurements in a vacuum requires additional apparatus and intro-duces considerable difficulty, especially at the higher temperatures.

Jan 1, 1940