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Officials of the State Department have expressed their hope that a considerable number of technical men will take the examination for consular service. The Department recognizes that the interest of the United States will be served best if technical men are made available through these examinations for vacancies at points where their training will be of special value. Industrial engineers who have passed the con-sular examination will be assigned to industrial centers of Europe or South America. Mining engineers, chemists, electrical engineers, etc., will be assigned to industrial centers requiring special training.

Jan 11, 1919

By Shiou-Chuan Sun

THE effects of oxidation on the flotation behavior of sulphide minerals have been extensively studied,1-3 but no similar study has been made of coals. Coals of bituminous and lower rank undergo atmospheric oxidation during mining and storage, and their degree of oxidizing increases with temperature4,5 and time of exposure.6 The problem of recovering fine oxidized coal from culm piles, rivers, and streams by froth flotation has become increasingly important to the coal industry as well as to those concerned with air and stream pollution. This paper describes the flotation behavior of oxidized and unoxidized coals and carbons in the presence of oily collectors and presents the reagents found effective in the flotation of oxidized coals and carbons. Except where otherwise stated, flotation tests were performed in a 50-g Denver flotation cell. Solid feed for each test was 30 g, and the pulp dilution was kept at 8.5. The -65 mesh coal sample was wetted by agitation with water in the flotation cell for 6 min, then conditioned with a predetermined amount of collector for 2 min, and finally floated with pine oil as frother for 3 min.

Jan 4, 1954

The following is an incomplete list of members and guests who called at Institute headquarters during the period July 11, 1918 to August 11, 1918. John Carter Anderson, Tucson, Ariz. Edson S. Pettis, San Francisco, Cal. Lieut. Frank A. Ayer, Tyrone, N. M. Wm. H. Rettie, Yonkers, N. Y. W. R. Canton, McGill, Nev. J. T. Robertson, Port Richmond, S. I. Alden Crankshaw, Palmerton, Pa. Harry O. Robinson, Margarita, John Davenport, W. Norfolk, Va. Venezuela. A. Faison Dickson. C. K. Seng, Gilbert, Minn. F. A. Fahrenwald, Cleveland, C). E. S. Sheffield. L. Hall Goodwin, New York. H. G. Smith. W. H. W. Hamilton, Baker, Ore. Harry M. Spoor. Floyd D. James, St. Louis, Mo. H. H. Stoek, Urbana, Ill. George A. Laird. Arthur L. Tuttle, Copperhill, Tenn. J. W. McBride, Spokane, Wash. Thor Warner, Phoenix, Ariz. Arthur Notman, Bisbee, Ariz. Christopher G. Atwater, Manager Agricultural Dept., The Barrett Co., is in Washington serving the U. S. Navy Bureau of ordnance in connection with the Navy nitrate plant recently authorized by Congress. Edward Ludlam Blossom announces his marriage to Mabel Townsend, daughter of Mr. and Mrs. George Comings Mills, on Wednesday, July 17, 1918, at New York City.

Jan 9, 1918

By John A. Fagnant

At Elkol, Wyo., about 80 miles northeast of Ogden, Utah, the Kemmerer Coal Co. and the Utah Power and Light Co. are involved in a joint venture that will soon see 1 million tons of coal going "out by wire" to Ogden. Kemmerer, owner of a multi-seam strip mine, and the utility, now building a steam power plant adjacent to the mine site, expect to begin initial power generation by February 1963. Although capable of producing only 150,000 kw at that time, this plant is expected to be ultimately enlarged to 500,000-kw capacity which will require about 2 million tons of coal annually. The deposit consists of more than 30 seams of coal, usually varying in thickness from 2 to 40 ft, and separated by beds of sandstones and shales. In certain areas the aggregate thickness of all the coal seams measures 300 ft. The thickest and most spectacular of these seams is the lowest one, referred to as the No. 1 seam, which is 118 ft thick in some places.

Jan 8, 1962

LIST OF THE MEETINGS OF THE INSTITUTE AND THEIR LOCALITIES FROM ITS ORGANIZATION Transactions Number Place Date Vol Page 1 Wilkes-Barre, Pa May, ?71 1 3 2 Bethlehem, Pa August, ?71 1 10 3 Troy, N Y November, ?71 1 13 4 Philadelphia, Pa February, ?72 1 17 5 New York, N Y May, ?72 1 20 6 Pittsburg, Pa October, ?72 1 25 7 Boston, Mass February, ?73 1 28 8 Philadelphia, Pa May, ?73 2 3 9 Easton, Pa October, ?73 2 7 10 New York, N Y February, ?74 211 11 St Louis, Mo May, ?74 3 3 12 Hazleton, Pa October, ?74 3 8 13 New Haven, Conn February, ?75 3 15 14 Dover, N J May, ?75 4 3 15 Cleveland, 0 October, ?75 4 9 16 Washington, D C February, ?76 4 18 17 Philadelphia, Pat June, ?76, 5 3 18 Philadelphia, Pa October, ?76 5 9 19 New York, N Y February, ?77 5 27 20 Wilkes-Barre, Pa May, ?77 6 3 21 Amenia, N Y October, ?77 6 10 22 Philadelphia, Pa. May, ?78 6 18 23 Chattanooga, Tenn May ?78 7 3 24 Lake George, N.Y. Oct. ?78 7

Jan 1, 1923

By B. Wilshire, W. J. Evans

W. J. Evans and 8. Wilshire SEVERAL recent investigations1-6 have shown that the strain, c, during transient and steady-state creep is well-represented by the expression: € = e0 + et(l - e-mt) + Esl [l] where Eo is the instantaneous strain on loading, ET the total transient strain, C, the steady creep rate! and m a constant relating to the rate of exhaustion of transient creep. However, it has been noted6 that deviations from this equation occur over the first 10 to 15 pct of the transient stage, when the creep rate, (. decreases more rapidly than is predicted by this equation. This rapid decrease has been attributed to a large change in work-hardening coefficient. It 1s widely accepted that steady-state creep results from a balance between the rate of strain hardcning h and the rate of recovery r (=-s(st) as: dE/dt = Es = r/h [2] Comparison of values obtained for h at the end of the initial extension and during steady creep suggests that h increases several fold during the transient stage. which has the effect of reducing the creep rate proportionally.7 To examine the dependence, on r and h, of the deformation behavior during transient and steady-state creep. a series of constant-stress creep tests was carried out at 413°C at 6000 psi using 70-30 a brass. Prelinlinary investigation showed that. with this material. the transient stage constituted a significant portion of the total creep life (-0.4tf. where tf is the time to fracture). The alloy. obtained from Metals Research Limited. was made from high-purity copper, 99.999 pct. and zinc. 99.99 pct. Heat treatment at 675°C for 4 1/2 gave a uniform grain size of 5 mm-1. Details of specimen preparation and creep testing procedures have been given previously.6 Values of h (?s/?E) were determined by measuring the instantaneous strain. ?E. which occurred on increasing the stress during creep by a small amount. ?s. Similarly. v (= -?s/ ?t) was derived from the incubation period. At, after a small decrease in stress.' Several values of v and h were obtained throughout duplicate creep tests. using different stress increments in the range 300 to 800 psi. The accuracy with which Eq. [I] represents the present creep curves was established by determining the best value of the constants Es, Et, m , and 6, using a digital computer program based essentially on the graphical solution for this equation devised by Conway and Mullikan.9 About 40 strain/time readings were taken during transient and steady-state creep. Over most of the creep curve, the average difference between the measured reading and the calculated strain at the appropriate time was less than 0.0001. However.

Jan 1, 1969

By J. O. Nelson, C. J. Altstetter

Single crystals of hcp cobalt, 3 mm in diameter and up to 35 cm long, were grown using an electron-beam, zone-melting technique. The martensitic-phase transformation was studied in single-crystalline and polycrystalline specimens by making length-change measurements as a function of temperature under various elastic compressive stresses. Upon thermal cycling, single-crystalline or polycrystalline specimens repeatedly transformed almost entirely on the same variant of close-packed plane provided the maximum temperature did not exceed 600°C. Cycling to 1000°C resulted in transformation on more than one {111} variant. This behavior is termed multivariance. The multivariant transformation occurred very rapidly at an M, temperature 2° to 6°C lower than the M, of a transformation which would result in a single-crystal product. Elastic compressive stresses (up to 253 g per sq mm) tended to lower the A, and raise the M, temperatures, decreasing the width of the temperature vs dilatation hysteresis loop. The transformation habit plane and transformation shear direction of an as-grown single crystal were not grossly affected by elastic compressi?ie stress. This was evidenced by similar dilatations on the temperature us dilatation loops joy specimens with and without compressive stress. A dislocation mechanism is proposed to explain the observed results. IT has been shown that, on heating, cobalt transforms martensitically from the hcp to the fcc phase.' The transformation habit plane is (0001)hcp || (lll)fcc and the transformation shear direction is (1010)hcp || (112)fcc. The transformation involves a shear of 1g°28', which may be achieved by a shearing of a/6(112) of every two planes with respect to the plane beneath, thus changing the ABABAB stacking of hcp to the ABCABC stacking of fcc. Associated with the phase change is a 0.3 x 10"3 contraction in the habit plane and a 4.2 X 10"3 expansion perpendicular to the habit plane resulting in a 3.6 x X volume increase on heating.' On cooling, an identical volume decrease takes place. The temperature at which the fcc phase begins to form on heating (A,) is reported as 430°C, and the temperature at which the hcp phase begins to form on cooling from an elevated temperature (A&) is reported as 390oC1,3 Consequently, temperature vs dilatation plots have the form of a hysteresis loop. If heating or cooling is reversed during a transformation, a smaller hysteresis loop results. Upon heating, the transformation is always complete; whereas, fcc is often retained at room temperature as a metastable phase entrapped in the polycrystal-line hexagonal matrix.1,4,5 Two obstacles in the theory of the allotropic-phase transformation of cobalt have been: 1) a detailed knowledge of the product nucleus, and 2) a plausible method of propagation of the transformation. Bilby,8 christian, 7 and seeger 8,9 have suggested a "pole mechanism" as a means of propagation of partiai dislocations from plane to plane. A pole dislocation and a Shockley partial come together at a node. The a/6(112) Shockley partial rotates about the pole dislocation effecting the transformation shear. The pole dislocation must have a 2a/3(111) screw component which causes extension of the transformed region by two atomic planes with each full rotation of the Shockley partial. Bollmannl0 suggested, on the other hand, that transformation propagation occurs due to the stress fields of intersecting (111)-type stacking faults. As faults intersect, a stress distribution is set up about their intersection which is in turn reduced by the emergence of another fault on the second nearest plane. This process continues with the final result of a complete phase transformation. In view of the similarities between deformation and transformation in cobalt, the effect of stress on the transformation would, hopefully, yield valuable information concerning nucleation and propagation. In the present work single-crystalline and polycrystalline specimen length changes were measured as a function of temperature at various compressive loads. PROCEDURE Several orientations of single crystals of hcp cobalt in lengths up to 25 cm were grown by electron-beam floating zone melting from 99.95 and 99.999 pct, 3-mm-diam cobalt rod as supplied by Johnson

Jan 1, 1964

By L. F. Mondolfo

An investigation of the relationship between properties of the elements and type of binary diagram formed was conducted. It was found that, for each type of equilibrium diagram, the factors for the size, valence, electronegativity, period, melting point, entropies of fusion, and sublimation calculated for each pair of elements cover a range of values. However, these factors show sufficient relationship to the equilibrium diagram so that the correlation of several of them can be used to predict the type of diagram formed, or at least limit the choice to only a few types. ThE goal of the metallurgist concerned with alloy development has always been to find a method that predicts the properties that can be obtained when a certain metal is added to another one. In most cases a qualitative predictiton of properties can be made if the equilibrium diagram is known. However, this means that for new metals the alloy development has to start with the experimental determination of the equilibrium diagrams. Because this determination is at least as complicated and time-consuming as the determination of the properties themselves, most alloy development has taken place by trial and error, and the study of the equilibrium diagrams has followed rather than preceded the creation of new alloys. Alloy structures and properties depend on the interaction between electrons and a complete knowledge of these interactions would permit prediction of structure and properties of alloys. Unfortunately direct measurement of these interactions is extremely difficult and somewhat doubtful and only properties that depend on them can be measured easily and with certainty. Study of the relationship between properties of the elements and equilibrium diagrams is not new. Besides the well known Hume-Rothery rule of the necessity of an atomic diameter fit within 15 pct for extensive miscibility in the solid, and the wide knowledge of the effect of such factors as size, electronegativity, electron-atom ratio on solid state features,"' work relating to liquid state and liquid-solid reactions can be found in the literature. Of particular interest is the work by Axon,3 who investigated the effect of size and melting point on a selected number of eutectic and monotectic dia-

Jan 1, 1962

By C. A. Rowland, M. D. Flavel

There are seven basic comminution circuits that can be used to prepare beneficiation feed from the product of a primary crusher. This paper gives a comparison of these circuits based on average process and economical data. The paper is principally devoted to a discussion of the test work required to obtain the process data needed to evaluate each circuit. The results of the test work in conjunction with geographic and economic factors can be used to narrow down the choice of possible circuits to one, two, or three before making a detailed engineering study.

Jan 1, 1985

ABOUT 2 lb. of alumina (aluminum oxide) of high purity is required to produce a pound of metallic aluminum. Projected production of metallic aluminum in the United States is now seven to ten times the peacetime rate a few years ago. In the past, all the alumina for aluminum production in the United States has been obtained from bauxite. Part of the bauxite was mined in the United States--chiefly in Arkansas-and part was imported from Surinam. All of it was chemically treated in the United States to separate the greater part of the aluminum oxide from the bauxite, alkaline solutions being used, in a method known as the Bayer process. The ingredients of the bauxite other than alumina, such as the compounds of iron titanium, and silicon, constitute the tailings from the Bayer-process operation. This product contains sufficient iron to give it a red color and hence it is called "red mud." Lime and soda used in the processing, are also present. Varying amounts of alumina remain in the red mud, depending upon the characteristics of the bauxite, the effectiveness of the treatment, and in particular upon the amount of silica originally present in the bauxite. High-silica bauxites result in high alumina loss in the red mud.

Jan 1, 1942

By G. S. Coe, G. F. Bolling

The columnar-to-equiaxed transition (CET) has often been studied as a function of concentration, C, temperature gradient in the melt, G, and rate of solidification, R. Although it may not be immediately obvious it is sure that the CET, expressed as some ratio G/R necessary to suppress equiaxed nucleation for a given C,' cannot be a single-valued function of C. This restriction which is ignored in theoretical presentations is most trivially illustrated by the following simple reasoning. An ordinary casting is an unconstrained system where the thermal conditions change continuously with progressive solidification, and thus where the ratio G/R decreases from the outset. A CET occurring early in a casting (much equiaxed material) must then mean a higher value of G/R at transition, in comparison with the late CET which implies a more columnar ingot. Therefore, when we choose to experiment under constant superheat for all alloys across the simplest binary, and we find an inversion in the amount of equiaxed material, we shall find two values of C satisfying the G/R condition. However, in addition to this simple instance, the early experiments of ~orthcott' seem to show that the amount of equiaxed material in cast ingots may be a multivalued function of composition in a given binary system. In the present investigation, the CET has been examined in Pb-Sb, Pb-Ag, Pb-Sn, and Sn-Pb under several types of casting conditions. First, we have used the "bidirectional" ingot section Simulation;~ and we have used .'i~z situ" ingot solidification where a hot mold already filled with liquid is chilled so that there is no disturbance provoked by pouring. Differences in method are trivial to our purpose except for the fact that certain variations are more simply observed by one technique than by the other. Second, we have varied the mode of superheating from the simple extreme of casting all alloys from the same temperature regardless of composition to the careful casting at a standard superheat, calculated with respect to the alloy liquidus. Third, we have made provisions for decanting and interface observation, so that some "castings" were not completed. The results obtained with Pb-Sb are exemplary; some of these are shown in Fig. 1 along with explanatory captions. At 9 to 10 at. pct Sb, and thus above the solid-solubility limit Cs = 5.8 at. pct Sb and yet below the eutectic concentration Ceu = 17.5 at. pct Sb, there is a persistent anomaly in all the variations. Measurement was easy enough and standard enough so that we may forgo discussion of either method or possible error, in view of the forceful self-consistency shown by experiment. Solute distributions were measured along the bidirectional ingots in order to determine if a solute buildup had occurred at the CET. No anomalous changes in concentration were observed along the bars at either side of the solute anomaly of 10 at. pct Sb. The microstructures of the ingots were also examined across the range of composition investigated. At concentrations less than 9 at. pct Sb the micro- and macrostructures were typical of the cellular-dendritic growth usually reported for the columnar zone. Above the anomaly, both the columnar grain size and the amount of primary phase decreased. This microstruc-tural observation can be correlated with observations made of decanted interfaces. Below 9 at. pct Sb, the interface reveals the "normal" columnar dendritic structure; however above the anomalous concentration range, preferential growth of certain dendrites appears to form a "super dendrite" pattern. In Fig. 2 a microstructural view of the etched '(super dendrites'' shows their constitution both in terms of relative phase proportion and in terms of the ordinary smaller dendrites.

Jan 1, 1969

By G. E. Burpee

A COMPREHENSIVE study of insoluble residues in the productive Permian limestone in the Hobbs and Eunice fields, Lea County, N. M., has been conducted by Shell Petroleum Corp. engineers {luring the past two years. This study was prompted by the belief that the stratigraphy of the producing formation might be worked out in detail and that some relationship might be established between the permeable oil, gas, and water zones and correlatable lithologic horizons within the productive formation. As a result of the study, correlations have been established which have proved of great value to both an orderly development and corrective program.

Jan 1, 1935

By F. F. Lines

It is not the intention of the writer to enter into a discussion of the relative merits of the duplex process as compared with the straight scrap and pig iron process, working under the same conditions, but rather to present in a general way several modifications of the former process, and then describe the method adopted by the Maryland Steel Co., as best suited to local conditions, and also to meet the metallurgical problem presented in the removal from the iron of an unusual constituent— chromium. The principal factors to be considered in. deciding whether or not duplexing should be employed are: (1) Chemical constituents of pig iron. (2) Variety and quantity of steel to be produced. (3) Relative cost of pig iron and scrap. (4) Regularity of operation. (5) Capital to be invested. (6) An existing Bessemer plant. Having decided to adopt the duplex process, several combinations may be used, viz.: (1) Acid-lined converter with basic open hearth. (2) Acid-lined converter with electric furnace. (3) Basic-lined converter with basic open hearth. (4) Basic-lined converter with electric furnace. (5) Basic open hearth with electric furnace. The combination of an acid-lined converter with a basic open-hearth furnace is the one most commonly employed, and as it is the one best adapted to the conditions encountered at the plant of the Maryland Steel Co., we will briefly outline the advantages and disadvantages of the different methods of working. There are two general methods of blowing, as follows: (1) The charge is desiliconized and partly decarbonized in the converter. On account of the difficulty in regulating the percentage of car-

Jan 1, 1916

Executive Committee, Board of Directors C E Reistle, Jr, Chairman, H DeWitt Smith, Vice-Chairman, T B Counselman, Grover Holt, A W Thornton Finance Committee, Board of Directors Andrew Fletcher, Chairman, R B Caples, C R Dodson Investments Erle V Daveler, '57, Chairman, Henry Krumb, '59, John E Warren, '57, G F Moulton, ex officio as Treasurer, Andrew Fletcher, ex officio as Chairman, Fi¬nance Committee Endowment W W Mein, Jr, Chairman, N G Alford, E V Daveler, W J Coulter, J V N Dorr, R B Gilmore, J B Haffner, 0 H Johnson, Henry Krumb, D H McLaughlin, J R McMillan, J B Morrow, L F Reinartz, Wilfred Sykes, C E Weed Honorary Memberships Andrew Fletcher, Chairman, L F Reinartz and H DeWitt Smith, ex officio as Past Presidents, C E Reistle, Jr , ex officio as President, M L Rai¬der, '60, Henry Krumb, '58, D H McLaughlin, '57, P D Merica, '59

Jan 1, 1956

By J. H. Fletcher, S. M. Cassidy

Air has been cooled, heated, washed, humidified and dehumidified for many purposes and in many industries. At a number of metal mines air is conditioned to reduce the high humidity and unbearable heat found in deep workings, and at some mines air is washed to allay siliceous dust. Steam is introduced into the intake air at many coal mines, particularly in winter, for the purpose of keeping loose coal dust so moistened that the hazard of an explosion is lessened. This paper will describe a further successful application of air conditioning in a coal mine, where, for over three years, all intake air has been cooled to a constant temperature for the sole purpose of preventing roof falls. Effect of Warm Weather on Mine Roof It is generally known by mining men that some, if not all, coal mines have more trouble from bad roof during the warm summer months than in winter. Also, it has been observed that roof on intake airways is usually worse than on the return entries, after the air has circulated through the mine. Some mines and some coal seams are much more affected than others. In the Clinton district of Indiana, the No. IV coal seam has a good, firm, gray shale roof except during the summer months, when it deteriorates badly and falls in small slabs 1 to 6 in. thick. Timbering is not very efficacious during this period because in time the roof will shear around the supporting prop or crossbar and either dislodge the timber or leave it supporting only a few inches of crumbly shale (Fig. 1). This action is renewed each summer, choking airways with fallen slate, tearing down trolley wires, hampering haulage, endangering men and adding considerably to the deadwork cost. Only when mines have been worked for a period of years and have been advanced a long distance from the shaft do the active workings become comparatively free of this trouble, and even then the intake entries are still a source of much deadwork. Such was the annoying situation at the mine of the Saxton Coal Mining Co. operated in the No. IV coal just north of Terre Haute, Ind. During the months of warm weather it was possible to stand at any quiet spot in the mine and within 10 min. hear at least two or three falls,

Jan 1, 1931

By Martial P. Corriveau

Almost everyone agrees that coal and oil shale are the only fossil fuel resources in which the United States is self-sufficient. Of the two, only coal has a technology sufficiently developed to be of intermediate term benefit. Since it takes at least 20 years to bring advanced technology into practice, it seems logical that the major focus on energy developments should be aimed at coal. Meanwhile, we need to trade-off between actions to meet our immediate needs and the various political regulations and social demands that are disrupting the coal industry and the industries dependent upon it. The largest single user of coal is the electric power generation industry. Over 300 million tons of coal are presently being consumed each year. In view of the 5-to 7-years lead time to bring in a base-load fossil-fuel fired generating station, our requirements for double this tonnage in 1980 are already well forecast; that is, if the coal companies are allowed to mine and the utilities are allowed to burn the coal.

Jan 2, 1974

By W. L. Fink, M. S. Hunter, 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.' The method was subject to such limitations (e.g., the difficulty in attaining electrochemical 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 equilibrium 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 determination of phase fields of equilibrium diagrams but also the determination of certain thermodynamic quantities which can be used advantageously in metallurgical 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 temperature is increased. Moreover, the necessity of carrying out measurements in a vacuum requires additional apparatus and introduces considerable difficulty, especially at the higher temperatures. Apparently, no consideration has been given heretofore to the metallurgical use of irreversible electrode potentials that exist when a specimen is immersed in a suitable aqueous solution at room temperature. The apparatus and the method required for such measurements are very simple, and if the results of such measurements could be demonstrated to be reproducible they might be very valuable in studying the structure of alloys. The method would not have the scope of that developed by Seltz and his co-workers because no thermodynamic quantities could be calculated from the data. However, the utility and the simplicity of the method might warrant extensive use for the determination of phase fields and similar applications. Theory of Irreversible Potentials A brief review of the theory of irreversible potentials will be given before showing how to interpret the potential readings in terms of alloy structure. It is known that heterogeneity of a metal surface in an electrolyte will produce points of different potentials, with the result that current flows between these points and electrochemical reactions occur. The points at which oxidation reactions are localized are known as anodes, and those at which reduction reactions are localized are known as cathodes.6, 7, 8 For the benefit of those who are not familiar with the terms anode and cathode as applied to a primary cell, the potential difference between anode and cathode of such a cell can be measured when

Jan 1, 1941

By M. S. Hunter, W. L. Fink, 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.' The method was subject to such limitations (e.g., the difficulty in attaining electrochemical 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 equilibrium 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 determination of phase fields of equilibrium diagrams but also the determination of certain thermodynamic quantities which can be used advantageously in metallurgical 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 temperature is increased. Moreover, the necessity of carrying out measurements in a vacuum requires additional apparatus and introduces considerable difficulty, especially at the higher temperatures. Apparently, no consideration has been given heretofore to the metallurgical use of irreversible electrode potentials that exist when a specimen is immersed in a suitable aqueous solution at room temperature. The apparatus and the method required for such measurements are very simple, and if the results of such measurements could be demonstrated to be reproducible they might be very valuable in studying the structure of alloys. The method would not have the scope of that developed by Seltz and his co-workers because no thermodynamic quantities could be calculated from the data. However, the utility and the simplicity of the method might warrant extensive use for the determination of phase fields and similar applications. Theory of Irreversible Potentials A brief review of the theory of irreversible potentials will be given before showing how to interpret the potential readings in terms of alloy structure. It is known that heterogeneity of a metal surface in an electrolyte will produce points of different potentials, with the result that current flows between these points and electrochemical reactions occur. The points at which oxidation reactions are localized are known as anodes, and those at which reduction reactions are localized are known as cathodes.6, 7, 8 For the benefit of those who are not familiar with the terms anode and cathode as applied to a primary cell, the potential difference between anode and cathode of such a cell can be measured when

Jan 1, 1941

By Herbert H. Kellogg

In 1930, Taggart, Taylor and Knoll1 found that addition of various electrolytes to suspensions of ground minerals resulted in the stopping or starting of Brownian movement of the suspended particles. On the basis of the many new facts found, they rejected the " classical"† theory of Brownian movement and proposed an "ioniza-tion " theory. This new theory was further supported in later publications by Taggart.3,4 The acceptance of the ionization theory by men in the field of flotation may be judged by the mention given this theory in Gaudin's "Principles of Mineral Dressing,'16 Wark's "Principles of Flotation,"8 as well as in a recent paper by Fitt, Thomas and Taggart.7 The proponents of the ionization theory have gone further than the mere statement of the new theory. A parallelism between the Brownian movement of mineral particles and their behavior in flotation was reported.1,3,4 Likewise, the correlation between flocculation-dispersion of mineral particles and the Brownian movement of these particles has been investigated.' Bankoffl5 has suggested that "slime-coating" can also be directly correlated with the Brownian movement of the slime particles. In each of the instances mentioned it is the ionization theory of Brownian movement that has been used to "explain" the correlations that were found. The essential conflict between the kinetic theory and the ionization theory can be understood best by a brief description of each. The kinetic theory* proposes that Brownian movement is caused by the impacts of liquid molecules against the solid particles. At any instant of time, the molecular impacts on all sides of the solid particle will not balance, and the particle will receive a push in some direction. According to this theory, dl particles suspended in a liquid are in Brownian movement. However, if the particle is very large, the impacts on all sides will very nearly balance and the motion will not be noticeable. Another factor, besides the size of the particle, that affects the magnitude of the Brownian movement is the viscosity of the liquid—the greater the viscosity, the less the displacement of particles by Brownian movement. This theory has been verified experimentally by measurement of the velocity of Brownian movement, and by measurement of the compacting of suspensoid particles under the influence of gravity.2 The originators of the ionization theory found that he addition of various electrolytes to slime pulps caused cessation or commencement of Brownian movement, depending upon the chemical nature of the particle and the electrolyte. The Brownian movement of quartz particles was observed to stop upon the addition of Certain electrolytes, where the conditions of the experiment prevented flocculation

Jan 1, 1947

By Herbert H. Kellogg

In 1930, Taggart, Taylor and Knoll1 found that addition of various electrolytes to suspensions of ground minerals resulted in the stopping or starting of Brownian movement of the suspended particles. On the basis of the many new facts found, they rejected the " classical"† theory of Brownian movement and proposed an "ioniza-tion " theory. This new theory was further supported in later publications by Taggart.3,4 The acceptance of the ionization theory by men in the field of flotation may be judged by the mention given this theory in Gaudin's "Principles of Mineral Dressing,'16 Wark's "Principles of Flotation,"8 as well as in a recent paper by Fitt, Thomas and Taggart.7 The proponents of the ionization theory have gone further than the mere statement of the new theory. A parallelism between the Brownian movement of mineral particles and their behavior in flotation was reported.1,3,4 Likewise, the correlation between flocculation-dispersion of mineral particles and the Brownian movement of these particles has been investigated.' Bankoffl5 has suggested that "slime-coating" can also be directly correlated with the Brownian movement of the slime particles. In each of the instances mentioned it is the ionization theory of Brownian movement that has been used to "explain" the correlations that were found. The essential conflict between the kinetic theory and the ionization theory can be understood best by a brief description of each. The kinetic theory* proposes that Brownian movement is caused by the impacts of liquid molecules against the solid particles. At any instant of time, the molecular impacts on all sides of the solid particle will not balance, and the particle will receive a push in some direction. According to this theory, dl particles suspended in a liquid are in Brownian movement. However, if the particle is very large, the impacts on all sides will very nearly balance and the motion will not be noticeable. Another factor, besides the size of the particle, that affects the magnitude of the Brownian movement is the viscosity of the liquid—the greater the viscosity, the less the displacement of particles by Brownian movement. This theory has been verified experimentally by measurement of the velocity of Brownian movement, and by measurement of the compacting of suspensoid particles under the influence of gravity.2 The originators of the ionization theory found that he addition of various electrolytes to slime pulps caused cessation or commencement of Brownian movement, depending upon the chemical nature of the particle and the electrolyte. The Brownian movement of quartz particles was observed to stop upon the addition of Certain electrolytes, where the conditions of the experiment prevented flocculation

Jan 1, 1947