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

Jan 1, 1930

By C. F. Smart

SINCE their comparatively recent development, the alloys of cadmium with silver and copper or nickel, and of cadmium with nickel alone, have been used somewhat extensively as liners for connecting rod bearings and main bearings of internal-combustion engines. In applications where, owing to high hearing loads and elevated operating temperatures, the life of hearings made from tin-hale or lead-base alloys has been undesirably short, cadmium alloys have demonstrated considerable advantage. In applications where, because of deflection of the crankshaft or bearing supports, copper-lead bearing metals have resulted in scored shafts, cadmium alloys have been operated successfully. The somewhat serious drawback to these alloys in hearing service has been that they, in common with copper-lead and certain lead alloys, are susceptible to corrosion in the presence of lubricants containing organic acids. These acids may be fatty acids (such as oleic acid) derived from animal or vegetable oils that sometimes have been compounded with engine lubricants, or they may be compounds of an acid nature developed by the oxidation of some petroleum oils under operating conditions. The result of such acid attack on hearings is illustrated by the photograph, Fig. 1. The petroleum oils that are most readily oxidized to a corrosive condition, and the operating conditions under which such oxidation most readily occurs, are now rather well known among the technical organizations of both the petroleum and automotive industries. While means have been developed for inhibiting petroleum oils against such acid formation, the knowledge that this condition may be encountered has been a factor in restricting the wider use of cadmium alloys as engine bearings. It has appeared, therefore, that their value and use would be enhanced if they could be made corrosion-resistant to a degree compatible with the most severe operating requirements. Investigation, undertaken with this in view, indicated that the addition of fractional percentages of the metal indium to the cadmium bearing

Jan 1, 1938

By Noel H. Stearn

To the successful functioning of the geomagnetic method of exploration in engineering and geological practice there are two prime prerequisites : the measurability and the interpretability of significant magnetic anomalies. A magnetic anomaly may be defined as a permanent distortion of the earth's magnetic field, in order to distinguish it frog the distortions, either cyclic or irregular, which vary with time. So far as known, time fluctations have no directly assignable geologic significance in terms of rock formations, while anomalies may be considered to be directly caused by the difference in the magnetic properties within and between the formations of the substances that make up the earth's outer shell. As is effectively pointed out by L. B. Slichter,1 the effects which these differences produce on the magnetic field may be extremely minute or extremely great, depending upon the magnetic properties of the formations. Thus the actual anomalies may range from the infinitesimal to a magnitude considerably greater than that of the earth's field. The geomagnetic method of exploration has shared in the deluge of experimental effort which has lately swept geophysical prospecting to its present important place in engineering and geologic practice. But to date more of this effort has been expended upon the measurability of anomalies than upon their interpretability. The tendency has been to strive for the development of instruments and especially field techniques capable of measuring minute anomalies with a precision far beyond that for which there can be any hope of adequate interpretation other than as interesting phenomena having numerous possible causes. Such efforts, of course, are highly commendable in the field of so-called pure science, which includes the accumulation of undigested detailed observations and admits of interpretation by multiple hypotheses, but in engineering practice the factor of economy must enter. Those instruments and techniques are most desirable which can most rapidly measure the interpretable range of anomalies with the precision necessary

Jan 1, 1932

By Sydney H. Ball

MINERALS used primarily for personal adornment and decorative purposes are called precious stones. To be so prized, the stones must possess beauty of color, must not be too common, and must be hard enough to withstand ordinary wear. If transparent, they must have brilliancy and fire. Almost one hundred minerals have been used as precious stones, the noble gems being the diamond, emerald, ruby, and sapphire; pearls are frequently included by courtesy. These gem stones, however, are sometimes equaled in beauty by fine opals, aquamarines, ourmalines, spinels, chrysoberyls (both cat's-eye and alexandrite), and spodumenes (hiddenite and kunzite). The Greeks, Romans, and medieval Europeans grouped together gem stones according to color and degree of transparency, and only as the niceties of mineralogy began to be known, about a century ago, was it realized how many different minerals have the beauty required of gem stones. Pliny, for example, did not distinguish between rubies and the red varieties of spinel and garnet, although he conjectured that the beryl and emerald were one mineral. GENERAL SURVEY Early man treasured bright colored berries, attractive shells, white teeth of wild animals and brightly colored pebbles, and used them as personal ornaments. In the eastern hemisphere, the earliest stones used were members of the quartz family (100,000 to 75,000 B.C.); then obsidian and amber (50,000 to 25,000 B.C.); the jade minerals, fluorspar and jet (22,000 to 7000 B.C.); turquoise (7000 to 3400 B.C.); lapis lazuli and garnet (prior to 3500 B.C.) ; emerald (2000 to 1800 B.C.) ; sapphire, ruby and diamond (800 to 500 B.C.). Indeed, gem mining is the oldest form of mining, and before any metals were known primitive man recognized about 18 gems and decorative stones. At first he sought them in stream gravels and residual deposits but by 3400 B.C. the turquoise mines of the Sinai Peninsula were operated. This was the world's first important hard-rock mining enterprise. The Afghanistan lapis lazuli mines may

Jan 1, 1949

By Fred C. Bond and

This paper is a continuation of two earlier papers,12 and presents new data on the grindability of various ores and other materials—the results of several years of intermittent research work on the nature of grinding and interpretation of test results. It is divided into five parts: 1. The tabulated results of several hundred grindability tests on a wide variety of ores. 2. A method of correcting screen analyses and calculating from them the surface and other properties. 3. A description of a new method of measuring the "surface energy" of an ore by pendulum impact tests. 4. Test results. 5. A general discussion of the test results and their application to grinding problems. 1. GRindability of Various Ores This part is a continuation of the paper listed as reference No. 1. The method of testing is described in detail in that paper. The sample to be tested is crushed to all through 6 mesh in rolls set at 1/16-in. opening in closed circuit with a screen. Of this sample 700 C.C. is ground dry in a laboratory ball mill under constant conditions of mill speed and ball charge in closed circuit with a screen of the desired size at 250 per cent circulating load. The mill is cylindrical, 12 by 12 in., and rotates at 70 r.p.m. It contains a charge of 285 iron balls weighing 20,125 grams and ranging from 1½ to ¾ in. in diameter. Each test is continued for a sufficient number of periods to establish equilibrium at 250 per cent circulating load, or until the composition of the circulating load is constant for successive periods. Tests are conducted at the mesh size to which the ore is to be ground in practice, and the results are expressed as the net production in grams of screen undersize per revolution of the mill. This is designated as the

Jan 1, 1939

By C. F. Smart

Since their comparatively recent development, the alloys of cadmium with silver and copper or nickel, and of cadmium with nickel alone, have been used somewhat extensively as liners for connecting rod bearings and main bearings of internal-combustion engines. In applications where, owing to high bearing loads and elevated operating temperatures, the life of bearings made from tin-base or lead-base alloys has been undesirably short, cadmium alloys have demonstrated considerable advantage. In applications where, because of deflection of the crankshaft or bearing supports, copper-lead bearing metals have resulted in scored shafts, cadmium alloys have been operated successfully. The somewhat serious drawback to these alloys in bearing service has been that they, in common with copper-lead and certain lead alloys, are susceptible to corrosion in the presence of lubricants containing organic acids. These acids may be fatty acids (such as oleic acid) derived from animal or vegetable oils that sometimes have been compounded with engine lubricants, or they may be compounds of an acid nature developed by the oxidation of some petroleum oils under operating conditions. The result of such acid attack on bearings is illustrated by the photograph, Fig. 1. The petroleum oils that are most readily oxidized to a corrosive condition, and the operating conditions under which such oxidation most readily occurs, are now rather well known among the technical organizations of both the petroleum and automotive industries. While means have been developed for inhibiting petroleum oils against such acid formation, the knowledge that this condition may be encountered has been a factor in restricting the wider use of cadmium alloys as engine bearings. It has appeared, therefore, that their value and use would be enhanced if they could be made corrosion-resistant to a degree compatible with the most severe operating requirements. Investigation, undertaken with this in view, indicated that the addition of fractional percentages of the metal indium to the cadmium bearing

Jan 1, 1938

By George S. Rice

Ten years ago: October, 1914, the author had the privilege of giving an illustrated address on investigations of coal-dust explosions1 to this Institute at one session of its fall meeting in Pittsburgh, Pa,. On the following day, the members had the opportunity of seeing a large-scale explosion test at the Experimental Mine near Bruceton, in which the explosion was made to follow a predetermined path by means of rock-dust barriers of various types, which had prevented the explosive waves from reaching the outlets of the mine by the shortest paths.2 There was also shown a ((home-made" rock-dusting machine discharging the dust from a flexible nozzle, and a cement gun operated for the quick erection of a fire or ventilation stopping, such as might be put up after an explosion. Following that paper, there was presented a paper by J. Taffanel, Director of the Lìévin testing station in the Pas de Calais, which reviewed the French coal-dust investigations.3 A paper4 by Howard N. Eavenson contains lists of explosions that occurred in North America and Great Britain, from early in the 19th century to 1912; in France to 1903, and Belgium to 1909. Although explosions still occur, we are hopeful that we have entered a happier freedom from these visitations, as the result of increased knowledge of the causes and means of prevention. Looking back over coal-dust investigations, there appear to have been periods of advance and of stagnation. Coal-dust Investigations From the earliest times of coal mining, which chiefly affected Great Britain as the first nation to take up coal mining on a large scale, to the beginning of the 19th century, no one thought of coal dust as an explosive agency; firedamp was the cause dreaded. It was believed, when Sir Humphrey Davy invented his safety lamp in 1815, that a solution had been found for the prevention of mine explo-

Jan 1, 1925

By F. L. Bosqui

INTRODUCTION The history of the development of gold metallurgy in South Africa is divisible into two periods: That preceding the introduction of the cyanide process on a commercial scale in 1890; and the 24 years intervening between that important event and the present time. The period between the discovery of the banket reefs of the Witwatersrand and the year 1890 was one of phenomenally rapid progress in mining development, but of no special interest to the metallurgist. There were no strikingly original or distinctly local advances in the treatment of gold ores. Californian practice in stamp milling and amalgamation prevailed, in mills ranging in equipment between 5 and 50 stamps, operating within a wide range of efficiency, and under the trying conditions usually en¬countered in a new and isolated field. The somewhat incomplete records of gold output of that period show that in December, 1887, there were 20 producing companies in the Witwatersrand district, of which 10 had mills, the largest being of 20 stamps. The only official record of returns for May, 1887, was that of the Wemmer mine, whose modest achievement with a 5-stamp, mill was 100 tons crushed, producing 887 oz. 3 dwt. of gold. This is interesting in view of the .present-day output of this field, which in 1913 reached 8,430,998 oz. The rapid increase of production during this first period (May, 1887, to January, 1891) is shown by the following summary for the year 1890:1 Total tons crushed 702,828 Number of stamps in operation 1,046 Average number of tons crushed per stamp per day 2.36 Yield of gold, ounces 494,817 Yield per ton, pennyweights 13.36 The stamp duty ranged between 1 ½ and 4 tons per day, according to weight of stamp, fineness of screen, and operating skill available. The prevailing weight of stamp was about 900 lb., and the screen, 900 meshes to the square inch.

Jan 5, 1915

By Charles T. Baroch, Corbin Allardice

Nuclear energy probably has greater potentialities for changing the world's way of life than any other recent discovery. The atomic-bomb bursts over Hiroshima and Nagasaki suddenly changed the concepts of war. Peaceful uses of nuclear energy are advancing so rapidly that no study of economic trends is complete without giving them consideration. The minerals specialist, especially, must be aware of this new force in our lives, as minerals and metals are essential in harnessing the new force, and atomic energy itself is rapidly improving its competitive position in the energy field. Future historians may chronicle December 2, 1942, as the beginning of the Atomic Age. On that day Enrico Fermi and his co-workers at the University of Chicago produced and controlled the first self-sustaining nu- clear chain reaction. Like many inventions, the first application of nuclear energy was as a weapon of war. However, its potential usefulness in man's work and welfare far outweighs in economic importance its destructive use in war, unless its military effect would be considered so great and all-embracing that no major power will hereafter chance a world conflict. Recognition of this potential has generated a vast international effort to exploit the atom for peaceful beneficent purposes. Like its physical manifestation, the advent of nuclear energy has unleashed chain reactions that have pervaded the political, social, and economic environments of the world. The impact of nuclear developments in one of many fields is exemplified by the uranium mining industry. Uranium was discovered in 1789 and in the next century and a half it found only an insignificant use as a ceramic coloring agent; in fact, in the latter part of that period, it was a largely unsalable by-product of the radium and vanadium industries. Up to 1940 the total quantity of uranium metal produced was not more than a few grams, of doubtful purity. Thus the production of 12,400 pounds of pure

Jan 1, 1959

By Richard McCaffery

WHEN we began the study of blast furnace slags we limited our work at first to a study of those slags containing only lime, alumina and silica. In our paper1 on some of the results of this first work, the solubility of. sulfur in slags containing no magnesia was reported and the question of sulfur solubility and slag viscosity discussed. There has been, for a long time, a very great difference of opinion among metallurgists as to .the effect of magnesia in blast furnace slags, and the literature is full of expressions of the most contrary opinions on the subject. As a result, our next publication2 developed the constitution of slags considered as a four-component system, silica-alumina-lime-magnesia, and advanced an explanation of slag structure which accorded with the facts and with scientific theory. The present paper continues our study of the general subject of slags. As blast furnace slags are included in the silica-alumina-lime-magnesia system, which is a particular case of four-component solutions, we have determined that there are 22 components (Table 1), which may enter into the silica-alumina-lime-magnesia system and that 10 or 12 of these components may be present in blast furnace slags which are within the ordinary ranges of composition. To have a very definite conception of the behavior of these components in a slag, we have developed the theory of the cooling of a four-component solution from the liquid state to the solid and the conclusions that we obtained have been made use of in this paper. On account of the importance of the four oxides and 18 compounds which enter into the silica-alumina-lime-magnesia system, some method of calculating the percentages of the various compounds that are present in the slag when the percentages of the oxides are given, seemed very desirable and we develop a method later herein for doing this, and finally we give illustrations of

Jan 10, 1926

By E. A. Trager, A. W. McCoy, H. R. Shidel

Sampling of the fluid from oil wells for percentages of oil, emulsified oil, and water during the last two years has brought out some interesting facts concerning oil-water emulsion. This result led to a laboratory investigation of emulsion, which substantiated the conclusions made from the field observations. The purpose of this paper is to present the information collected, the laboratory experiments, and our interpretation of the same. In order to define emulsified .oil exactly, give its synthesis and origin, and to show how and when it is formed in the wells, the work was necessarily divided into two separate lines—laboratory work and field observations. It is hoped that this study may lead to a discussion of such points so that the petroleum engineer, geologist, or technologist may be benefited by its practical bearing on oil-field management. Special credit is due Mr. Everett Carpenter, chief geologist of the Empire Gas & Fuel Co., for his assistance and cooperation in this work. Labobatory Investigations on Emulsified Oil Laboratory investigations were conducted in an attempt to learn the composition and some of the properties of emulsified oil, or B. S., as it is more commonly called, also to demonstrate, by laboratory methods, how B. 5. may be formed under conditions similar to those existing at the time a well is being pumped, and how it may be broken down. Literature bearing on this subject is widely scattered and very limited in scope. Bacon and Hamor define B. S., or bottom settlings, as "earthy matter, inert organic matter, or, in the case of Pennsylvanian petroleum, an emulsion of paraffin wax and water, which accompanies crude oil." In this discussion we will limit the term B. S. to that heavy, dark-brown emulsion, composed of a physical mixture of water, oil, and air with some included inert matter, either organic or inorganic. Possibly the first step in a description of this product should be a description of its physical properties, but since most operators are quite

Jan 1, 1921

By John B. Dilworth

In September, 1930, H. N. Eavenson, then Chairman of the Coal Division, appointed a Committee on Methods of valuing Coal Propelvties, with John B. Dilworth as chairman. The latter prepared a schedule' of features for consideration under the general headings of Undeveloped and Developed Coal Properties. These subjects were divided among the members of the committee and during the next year written discussions of his allotted subjects were received from each member. Mr. Grimes and Mr. Eavenson discussed the entire list,. These discussions were mimeographed and a set sent to each member before the meeting of the Institute in February, 1932. There was a general discussion at that meeting. At the meeting in February, 1934, Mr. Dilworth submitted a report12 which summarized the accumulated opinions and data and presented the conclusions of the committee as a whole on the subjects embraced in it's schedule. Members of the committee expressed the desire that some of the individual opinions be published for reference. Mr. R. Damon Hall's abstracts of these papers arc therefore presentrd herewith.3 Personnel of Committee John B. Dilworth (Chairman), Consulting Mining Engineer, Edward V. D'Invilliers Engineering Co., Philadelphia, Pa. Eli T. Conner, Consulting Mining Engineer, Seranton, Pa. W. G. Duncan, Jr., Superintendent, W. G. Duncan CoaI Co., Greenville, Ky. Howard N. EAveNson, Consulting Mining Engineer; Eavenson, Alford & Hicks. Pittshurgh, Pa. George Watkin Evans, Consulting Mining Engineer, Seattle, Wash. J. A. Garcia, Consulting And Constructing Engineer, Allen & Garcia Co., Chicatgo. III. John Alden Grimes, Valuation Engineer, Bureau of Internal Revenue, Washington, D. C. Otto Herres, Assistant Manager, United States Fue1 Co., Salt Lake City, Utah. J. R. Hicks, Consulting Mining Engineer, Eavensorl, Alford & Hicks, Pittsburgh, Pa. Robert D. Reeder, Mining Engineer, U. S. Bureau of Mines, Washington, D. C. Samuel, A. Taylor, Consulting Engineer, Pittsburgh, Pa. Bleeckee L.. WHeeler, Mining Engineer, Ford, Bacon & Davis, New York, N. Y.

Jan 1, 1934

By J. Bulina, J. T. Brown

SINCE the inception of vacuum cold-hearth arc melting of high-temperature alloys (about 4 years ago) it has been theoretically reasoned and qualitatively found that better mechanical properties are often obtained from alloys which have been melted by this practice. Mechanical properties are emphasized in this evaluation because of their importance in design. Vacuum-arc melting has an intrinsic advantage in that it creates an ingot grain structure which is easier to forge and thus leads to greater yields for the finished product. The greater yield naturally gives the process an economic basis when the cost per pound of alloy is rather high. However, the question stressed here is, does the process create an alloy with inherently better properties? There are several theoretical reasons for suspecting that it does. One is the vacuum refining which should permit lowering the content of harmful residuals with high vapor pressures. A second is the vacuum process which should preclude the formation of harmful distribution of oxides, nitrides, or carbo-nitrides, by keeping the amount of such constituents formed to a minimum. A third is the vacuum-arc cold-hearth method which prevents the possibility of pick-up of harmful elements from a refractory crucible since none is used. Fourth, the rapid solidification rate, induced by having a cold mold and only small amounts of molten metal at any one time, minimizes the segregation of elements like titanium, aluminum, and molybdenum from the top to the bottom of the ingot. This rapid solidification rate also decreases the tendency of the above elements to form undesirable phases by segregating locally. Another less frequently considered vacuum-arc melting advantage is the inherently finer-grained ingot structure which can be produced. Finer initial grain size leads to better forgeability, and means that after relatively small reductions to billets or final forged products a finer-grained material is obtained, which, by virtue of its finer grain size, would usually have greater stress-rupture ductility.

Jan 1, 1960

By F. E. Smith, David R. Mitchell, B. M. Bird

DENSE-MEDIA processes utilize the familiar laboratory float-and- sink procedure on a commercial scale. Just as wood chips float on water and sand sinks, ,so coal floats and refuse sinks when placed in a medium intermediate in specific gravity between the coal and refuse. Liquids intermediate in specific gravity between coal and refuse used in commercial plants are of four types: (1) Organic liquids of high specific gravity-halogenated hydrocarbons; (2) dissolved, salts in water; (3) pseudo liquids obtained by suspending solids, such as sand, in water, and (4) fluidizing a mass of sand or other solids by air currents. Those most widely used for cleaning coal are solutions of calcium chloride in water and a suspended-sand pseudo liquid. Laboratory float-and-sink testing is an intermittent operation during which every opportunity is given for particles lighter than the medium to float and particles heavier to sink. Commercial processes are continuous, vertical and horizontal currents of the separating medium occur as either part of the process or unavoidably produced by the introduction of feed and withdrawal of products, so that the exact separation of the laboratory technique is not duplicated by commercial processes. However, separations close to the theoretical are obtained in commercial machines by careful technical control of the process. Most machines in commercial installations are crowded to get as much out of the equipment as possible, so that careful technical control is necessary to get the recoveries and grade of product desired. Sizes usually cleaned are plus 3/16-in. or plus 1/8-in. in the United States and plus 1/16-in. in Great Britain: Coal as small as 1 mm. has been cleaned in some experimental installations. The separation of coal from refuse in sizes finer than about in. is made difficult by viscosity' effects and hence at the present time cleaning is confined to the coarser sizes. Technical advances in the art of cleaning coal by dense-media

Jan 1, 1943

By Charles T. Baroch, Charles J. Baroch

Nuclear energy probably has greater potentialities for changing the world's way of life than any other recent discovery. The atomic-bomb bursts over Hiroshima and Nagasaki suddenly changed the concepts of war. Peaceful uses of nuclear energy are advancing so rapidly that no study of economic trends is complete without giving them consideration. The minerals specialist, especially, must be aware of this new force in our lives, as minerals and metals are essential in harnessing the new force, and atomic energy itself is rapidly improving its competitive position in the energy field. Future historians may chronicle December 2, 1942, as the beginning of the Atomic Age. On that day Enrico Fermi and his co-workers at the University of Chicago produced and controlled the first self-sustaining nuclear chain reaction. Lie many inventions, the first application of nuclear energy was as a weapon of war. However, its potential usefulness in man's work and welfare far outweighs in economic importance its destructive use in war, unless its military effect would be considered so great and all-embracing that no major power will hereafter chance a world conflict. Recognition of this potential has generated a vast international effort to exploit the atom for peaceful beneficent purposes. Like its physical manifestation, the advent of nuclear energy has unleashed chain reactions that have pervaded the political, social, and economic environments of the world. The impact of nuclear developments in one of many fields is exemplified by the uranium mining industry. Uranium was discovered in 1789 and in the next century and a half it found only an insignificant use as a ceramic coloring agent; in fact, in the latter part of that period, it was a largely unsalable by-product of the radium and vanadium industries. Up to 1940 the total quantity of uranium metal produced was not more than a few grams, of doubtful purity. Thus the production of 12,400 pounds of pure

Jan 1, 1964

By C. F. Smart

Since their comparatively recent development, the alloys of cadmium with silver and copper or nickel, and of cadmium with nickel alone, have been used somewhat extensively as liners for connecting rod bearings and main bearings of internal-combustion engines. In applications where, owing to high bearing loads and elevated operating temperatures, the life of bearings made from tin-base or lead-base alloys has been undesirably short, cadmium alloys have demonstrated considerable advantage. In applications where, because of deflection of the crankshaft or bearing supports, copper-lead bearing metals have resulted in scored shafts, cadmium alloys have been operated successfully. The somewhat serious drawback to these alloys in bearing service has been that they, in common with copper-lead and certain lead alloys, are susceptible to corrosion in the presence of lubricants containing organic acids. These acids may be fatty acids (such as oleic acid) derived from animal or vegetable oils that sometimes have been compounded with engine lubricants, or they may be compounds of an acid nature developed by the oxidation of some petroleum oils under operating conditions. The result of such acid attack on bearings is illustrated by the photograph, Fig. 1. The petroleum oils that are most readily oxidized to a corrosive condition, and the operating conditions under which such oxidation most readily occurs, are now rather well known among the technical organizations of both the petroleum and automotive industries. While means have been developed for inhibiting petroleum oils against such acid formation, the knowledge that this condition may be encountered has been a factor in restricting the wider use of cadmium alloys as engine bearings. It has appeared, therefore, that their value and use would be enhanced if they could be made corrosion-resistant to a degree compatible with the most severe operating requirements. Investigation, undertaken with this in view, indicated that the addition of fractional percentages of the metal indium to the cadmium bearing

Jan 1, 1938

By John Hays Hammond

The Transvaal comprises about 120,000 square miles (nearly • the size of the United States Territory of New Mexico). Besides the famous Witwatersrand, which will here be de scribed in detail, there are two quartz-mining districts of some importance, viz., Lydenburg and De Kaap. The Lydenburg district first attracted attention in 1876, when the alluvial deposits of that section began to be exploited. At a later period vein-rnining was started, and at the present time several companies are operating in that district. The product in 1898 of five companies, running 137 stamps, was 154,560 tons of ore, yielding 108,884 crude ounces of gold (an average of 14.09 dwt. crude gold per ton) valued at £392,378. The De Eaap gold-fields were discovered in 1884. In 1898, seven companies, running 200 stamps, produced 89,760 crude ounces of gold, valued at £314,792. I. Mining Titles in the Transvaal. The mining laws of the Tranuvaal are most excellent in char acter, and while the claims cover every square foot of land for an area of nearly 40 miles long by from 2 to 3- miles wide, there have been practically no conflicts over extra-lateral rights. Notwithstanding the change in the political status of the Transvaal likely to follow the present war, it may be coufi dently assumed that the main features of the mining law of the South African Republic will be retained, and certain op pressive featureu of monopolies, etc., bearing with special weight on the mining industry, will be abolished. The dynamite mo nopoly was one that bore most heavily on the mining industry; and, according to the Reports of the State Mining Engineer, explosives, including fuse and detonators, amounted to nearly 10 per cent. of the total working costs of the mines. Further more, it was impossible to obtain the proper quality for the most economical working, and often 80-per-cent. or 40-per-cent. gelatine had to be used- in many instances where 60-per-cent.

Jan 1, 1902

By H. W. Weart, D. J. Mack

SINCE the first recognition of eutectic solidification as the simultaneous formation of 2 solids from one liquid,1 many complex structures thus produced have been observed. Despite many attempts to ascertain it, however, the detailed mechanism by which these structures develop remains obscure. In an attempt to clarify the origin of eutectic structures, the study described in this paper was undertaken. The broad objective of the study was to investigate the effect of different solidification conditions on the structure of single eutectic grains. It was expected that the eutectic structure would thereby be isolated for study, but preliminary experiments revealed another structure within each grain. When a literature surveye revealed only 1 previous mention of the subgrain structure,' it was decided to determine the origin of the structure and to study its response to various growth conditions. Before presenting the details of the investigation, it is apropos to distinguish carefully among the 3 structures produced during eutectic solidification. This is especially desirable in view of the apparent confusion existing in the literature concerning the structures in a eutectic specimen. The confusion is due largely to the existence of the subgrain structure noted above which is easily mistaken for the grain structure. In the following paragraphs, an effort is made to distinguish the 3 structures by briefly describing their origin during solidification, even though the results are thereby anticipated slightly. The 3 structures produced during eutectic solidification are the grain structure, the colony structure, and the eutectic structure, each one contained by the one preceding it. The grain structure is analogous to the polycrystalline structure of a metal or inle-phase alloy in that each grain grows from a single nucleus. A somewhat broader interpretation is needed here, however, because of the presence of 2 phases in each grain. Since in most eutec-tics particles of 1 phase are dispersed in a matrix of the other, a grain may be taken to be the region in which the matrix phase is monocrystalline.*

Jan 1, 1959

By H. Biloni, G. F. Bolling

The microsegregation in tin specimens containing 0.2, 0.5. or 1 wt pct Pb has been studied m detail. The specimens were grown from the melt in a controlled fashion and exhibited a well-developed cellular substructure. In general, a severe microsegre-gation can be observed in all the photomicrographs presented. Some observations of special interest are: the distribution of a second phase, the presence of a eutectic in several forms, the evidence for dif- THE Smialowski or cellular substructure which forms during solidification has been extensively studied during the past decade.'* Many of the im- *Most references to the cellular substructure except for the last 2 years are reviewed by Winegard.' portant characteristics of this substructure, such as its occurrence and variability with growth conditions, its association with the phenomenon of constitutional supercooling, and its effect on dislocation production and mobility, have received quantitative fusion of solute in the solid, and the enhancement of segregation at a dislocation subboundary network ("striations"). On the basis of the metallographic observations, it can be deduced that the segregation observed is representative of the solute segregation produced during crystal growth. Some deductions are also made about the interplay of the two substructures, cells and striations, and about the mode of cellular growth. investigation both experimentally and theoretically. However, the concentration profile of the solute segregated during crystal growth has not been examined in detail. Tin crystals grown from melts containing various concentrations of lead have been most extensively studied. In a recent investigation of Sn-Pb alloys, Kramer et a1.2 were able to measure the effective solute distribution coefficient, k,, at the most advanced points of the solid-liquid interface, over a large range of growth conditions, finding it to approach the value of k,, the equilibrium distribution coefficient. As will be shown, this must lead to drastic segregation. Another recent study of several Sn-Pb alloys was made by Plaskett and winegard3 who investigated the variation of growth conditions

Jan 1, 1963

By F. E. Smith, David R. Mitchell, B. M. Bird

DENSE-MEDIA processes utilize the familiar laboratory float-and¬-sink procedure on a commercial scale. Just as wood chips float on water and sand sinks, so coal floats and refuse sinks when placed in a medium intermediate in specific gravity between the coal and refuse. Liquids intermediate in specific gravity between coal and refuse used in commercial plants are of four types: (1) Organic liquids of high specific gravity-halogenated hydrocarbons; (2) dissolved salts in water; (3) pseudo liquids obtained by suspending solids, such as sand, in water, and (4) fluidizing a mass of sand or other solids by air currents. Those most widely used for cleaning coal are solutions of calcium chloride in water and a suspended-sand pseudo liquid. Laboratory float-and-sink testing is an intermittent operation during which every opportunity is given for particles lighter than the medium to float and particles heavier to sink. Commercial processes are con¬tinuous, vertical and horizontal currents of the separating medium occur as either part of the process or unavoidedly produced by the intro¬duction of feed and withdrawal of products, so that the exact separation of the laboratory technique is not duplicated by commercial processes. However, separations close to the theoretical are obtained in commercial machines by careful technical control of the process. Most machines in commercial installations are crowded to get as much out of the equipment as possible, so that careful technical control is necessary to get the recoveries and grade of product desired. Sizes usually cleaned are plus %6-in. or plus 3-in. in the United States and plus 36-in. in Great Britain. Coal as small as 1 mm. has been cleaned in some experimental installations. The separation of coal from refuse in sizes finer than about % in. is made difficult by viscosity effects and hence at the present time cleaning is confined to the coarser . sizes. Technical advances in the art of cleaning coal by dense-media

Jan 1, 1943