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By C. O. Swanson

In the iron ranges of northern Michigan, magnetic data have been used as an aid in geologic field work since the time of the earliest surveys. The presence of complex structures containing magnetic formations, and the general scarcity of exposures, guided the early work into this line of attack, and later field studies tended to place more and more emphasis upon this geophysical relationship, until, at present, the collection of magnetic data is a matter of routine in any areal survey. At first, horizontal deflections of the compass needle were the only data collected. In subsequent surveys, greater dependence was placed on dip-needle readings, which record variations in the intensity and inclination of the earth's magnetic field. Recently the trend has been toward adjusting the instrument so as to reduce the influence of changes in inclination, and using a more sensitive modification, called the Superdip,' in weakly magnetic areas. To a minor extent, the magnetometer has also been employed. The object of this paper is to present the writer's experience with magnetic data in this region. The conclusions are based on work covering a period of 10 years, and spread over nearly all of the iron ranges and a large part of the intervening areas. The viewpoints expressed are purely geological ones. In other words, any opinion as to the usefulness of a certain relationship is based upon the writer's experience with it as a guide in interpreting the structures of this region, and not upon its soundness theoretically, nor its usefulness under other conditions. A very brief summary of the conclusions is as follows. The most important step is that of collecting the magnetic data. This requires a suitable adjustment of the dip needle, and sufficient readings to accurately portray the variations in the magnetic field, which are apt to be irregular. Once the readings are taken and plotted in some clear fashion, the interpretation of them is usually merely a matter of observing their relation-

Jan 1, 1934

By Joseph E. Pogue

The past year in the petroleum industry was one of overproduction, rising inventories, low prices, and meagre to vanishing profits. This outcome was the result of a long period of intensive and uncompensated effort on the part of both financial and industrial interests, to stimulate supply on the theory that the primary problem facing the petroleum industry was the development of an adequate reserve of raw material to protect a large and ever-growing investment. The stimulus was applied in various forms and through diverse channels: capital had long flowed into the industry in excessive amounts under the attraction of large expected profits; the price level for crude petroleum had persistently been influenced by speculative considerations, with the result that prices declined slowly in periods of flush production and were quick to advance in anticipation of statistical improvement, thus maintaining a superfluous degree of stimulus on wildcatting and on drilling; speculation in inventories had led to the unsound, or at least unusual, business practice of accumulating huge stocks of oil; and, above all, the industry had directed the potent force of technology to the expansion of supply and achieved radical results in accelerating oil discovery, speeding up the rate of oil extraction, and enlarging the recovery of gasoline and lubricating oils from the raw material. In short, the economic conditions of 1927 were exactly those to which the objectively driven enterprise of the petroleum industry had long been directed; and the undesirable financial consequences arising therefrom reflected no lack of success in what had been set out to be achieved, but rather the failure to have established concurrently the necessary means of economic control to prevent the immediate conversion of reserves into current supply, and likewise the oversight in neglecting to apply the technological force to the enlargement and diversification of the market for petroleum products. Perhaps, when viewed in its longer perspective, 1927 will stand out as the turning point in the economic policy of the petroleum industry, when the technique of rationalizing production made its initial claim for recognition.

Jan 1, 1928

By George A. Colligan, John M. Lo

Electrical resistivity as a function of temperature was investigated in undercooled gallium and under-cooled Ga-In alloy of eutectic compositian to examine structural changes in undercooled melts. A continuous linear extension of the resistivity was determined for 99.999 pct pure gallium when undercooled below the stable Ga(l)-liquid, and the metastable Gafl)-liquid equilibria. In icndercooled Ga-In, a significant continuous negative departure from linear resistivity behavior was observed below the eutectic temperature. All resistivity measurements were made by the four-point probe technique. ThE temperature range for investigations into the physical properties of liquids before freezing has been greatly extended with the undercooling of massive melts of pure metals and alloys. Experimental determinations of thermal and transport properties and diffraction patterns in undercooled systems should throw further light on the structural behavior of liquids. Many measurements showing prefreezing anomalies in viscosity1'5 have been regarded677 as evidence for structural groupings in the liquid state. However, the majority of viscosity results,~)~-~~ conforming to the law 17 =A exp(~/RT), do not support theories of atomic aggregation. For the system Cd-Sb, which exhibits a metastable solid phase, Fisher and Phillipsg reported that, in undercooled alloys, the activation energies for viscous flow below the stable liquidus are much higher than those above it. Similarly, Miller et a1." observed a doubling of the activation energies for electrical conductivity in undercooled Cd-ib alloys. These effects were suggested as indicative of atomic association and clustering in the liquids at lower temperatures. With the recent establishment of metastable phases in pure gallium22 and its alloys,23 attempts were made during this investigation to undercool bulk samples and to determine the temperature dependence of electrical resistivitv. Pure gallium, when undercooled below -17°C at atmospheric pressure, can crystallize to either a stable Ga(1) phase (mp, 29.78"C) or a metastable phase identi-

Jan 1, 1967

By J. C. Febles

The use of iron for the precipitation of copper was known at least as early as the fifteenth century. Both Paracelsus and Basil Valentine refer to it in their writings, as early as 1500 A. D. It was used in Peru for this purpose prior to 1637, and at Rio Tinto, Spain, as early as the sixteenth century. The statement has been made repeatedly that in the early history of the mining industry at Butte, the practicability of this method of recovering copper from solution was overlooked, and that enormous quantities of copper-bearing water were allowed to go to waste, the copper in which might easily have been recovered at small cost; and that this oversight on the part of the mine operators was due to ignorance of this method of recovering copper. As a matter of fact, very little copper-bearing mineral was encountered in the mines of Butte until a depth of 400 or 500 ft. had been reached, and in many cases much greater depths were necessary to reach the copper-bearing zone. The water encountered in the upper levels (although in most cases quite highly mineralized) contained little or no copper, and it was only after considerable areas of copper-bearing ore had been uncovered and developed that copper sulphate began to appear in the mine water in any considerable quantity. In fact, the first water that was observed to contain copper carried it in such small amounts as to be of little or no importance. It was only after years of underground work had opened extensive areas of stopes, drifts, and other underground workings, these being subsequently filled with waste, nearly all of which contained small copper values, which became oxidized by exposure to the air and were acted upon by the slowly percolating mineral water, that the recovery of copper from mine water became commercially important.

Jan 1, 1914

By G. L. F. Powell

Bulk samples of silver have beat undercooled lo a large degree in contact with crystalline siliceous and ceramic oxide materials, indicating lhat stable oxides and oxide compounds are not the heterogeneous nucleants which normally catalyze cryslallization within a feu degrees of the equilibrium freezing point. Since 400-g samples were undercooled 250°C in contact with cristobalite, it is concluded that the undercooling required for homogeneous nucleation of sil11er is greater than 250°C. Undercooling was Jacilitated by precleaning the crucibles with a high-fires -sure blast of gas. IN numerous experiments on the undercooling of metal melts it has been assumed that a solid glassy surface, being non crystal line, will have no effect in catalyzing crystal nucleation from the melt. Conversely, it is usually accepted that any crystalline surface, in contact with a metal melt, will catalyze nucleation of metal crystals from the melt at degrees of undercooling less than that at which homogeneous nucleation will occur. Both these assumptions were implicit in the claim that homogeneous nucleation was observed in experiments1'2 on the undercooling of small metal droplets (10 to 100 mp diam). The droplets were thought to be freed of suspended crystalline particles which would otherwise catalyze heterogeneous nucleation. They were supported on flakes of silica glass which were assumed to be amorphous, and therefore incapable of acting as substrates for heterogeneous nucleation. In later experiments, large samples of molten metal were undercooled to temperatures similar to those achieved by the droplet technique by melting in a fused-silica crucible3 or a boro-silicate glass slag.4 Since these samples were usually fully enclosed in glass at the moment of freezing, it seemed possible that nucleation was homogeneous when maximum degrees of undercooling were achieved, despite the large size of the samples (up to 500 g). In experiments on the undercooling of silver5 the metal was contained in vitreous silica crucibles, the

Jan 1, 1968

By Henry G. Granger

It still rains in the Choco! I well remember one evening a dozen years ago, while traveling toward the town of Negua in a small champa or dug-out canoe, the rain fell so heavily that I had to work my hardest to bail out the water with a large totuma or gourd in order to keep the canoe afloat, the native boatman meanwhile plying his paddle in the stern. If any one thinks bailing is easy work, let him scoop out a quart or more at a stroke, 40 times a minute for half an hour, and I venture that he will change his opinion. These small canoes required only one paddler to make the 3 miles an hour which is the standard rate of aquatic progress on the Choco. Another time, on the Atrato river, about six o'clock in the afternoon, the rain fell so heavily that an empty gourd, 9 in. in diameter and 4.5 deep, was filled to the brim in 90 sec., timed by a watch. Such downpours are typical, but unless caught in one it is not specially noticed. These downpours seldom last more than an hour, and frequently cover only a limited area, occasionally falling on one bank of a river and not on the other. During the night-time, the rain, if gentle, will usually last until dawn, and sometimes an intermittent drizzle will keep up all day as well, although, as a rule, it rarely rains during the day. The rise of the rivers, due to the rain-fall, varies from a few inches to several feet. One night in August, 1899, the spuds of the dredge Margaret, operating on the Atrato river, showed a rise of 16 ft., and for 3 days thereafter occurred the greatest flood known in that district for 32 years. The dredge had all three spuds down, and the 2-yd. shovel dragging 011 the bottom. A 0.75-in. cable fast to a stout tree, 700 ft. away, stretched tight

Jan 1, 1909

By Arthur B. Cummins

POWDERED nonmetallic minerals and rocks of many different types are used extensively in industry for incorporation in compositions and manufactured products The term "mineral filler" is commonly employed to designate a material that is used for a specific purpose but not as an essential or reactive component Such a definition is not without objections, and it is indeed difficult to define fillers in any fully satisfactory manner, since the term has come to have so many different meanings and to cover such a wide range of uses. A filler is defined, for the purposes of this chapter, as a substantially inert material not specifically employed as a reactive or essential component, the primary function of which is to modify the properties or processing of a composition of matter or fabricated article Emery1 has emphasized that fillers change the properties of the product but are themselves unchanged in compounding or use The term "filler" appears to be rather general when referring to usages m bituminous compositions, rubber, composition floorings, fertilizers, plastics, textile finishes, and some others. In paper manufacture, in the paint industry and with insecticides, other terms are frequently employed, as is indicated, herinafter By placing emphasis on the function of the material used in modifying the properties of the composition or article, it is believed that a more useful classification of filler products and their applications may be derived. FUNCTIONS OF MINERAL FILLERS All of the manifold functions of mineral fillers cannot be listed in a summary review. A survey of the uses for these materials, however, shows that in nearly all cases the powders are employed to modify the properties of a composition of matter or those of a fabricated article, or to perform some useful function In the manufacture of either. A generalized list of these useful functions may be given is follows 1 To Modify Optical Properties Color Surface texture Opacity Brightness and gloss (as in paper and plastics) Flatness (as in lacquers and paints)

Jan 1, 1949

By Albert Sauveur

AT the New York meeting of the Institute, February, 1914, Professor Hopkinson and Sir Robert Hadfield presented an important paper entitled Research with Regard to the Non-Magnetic and Magnetic Conditions of Manganese Steel.1 Any contribution on manganese steel by its discoverer necessarily carries with it much weight and is entitled to serious and close consideration. The momentous discovery of that alloy by Sir Robert Hadfield some 30 years ago was the signal for great activity in the field of alloy steels; and the remarkable results obtained in the last two decades probably constitute the most important modern advance in the metallurgy of steel. The authors of the paper referred to above are unable to reconcile with the allotropic theory the interesting results obtained by them in heat treating manganese steel. When they speak of the allotropic theory, however, I understand that they have more especially in mind the existence of beta iron. It is not my understanding that they question the occurrence of iron in the two allotropic varieties known as gamma and alpha. If I am wrong, I trust they will correct me. A careful consideration of the experimental results reported and discussed by the authors leads me to believe that on the contrary they can be very satisfactorily explained in terms of allotropy and that, in the light of our present knowledge, they cannot be accounted for in any other way. The physical properties of non-magnetic manganese steel described by the authors are those pertaining to iron-carbon alloys in which iron is present in the gamma condition, or, in other words, to austenite. The metal is then characterized by great tenacity and ductility and low elastic limit, while its hardness, mineralogically speaking, is not excessive, but of a special kind termed "tough hardness" by the authors. Even when subjected to the restraining influence of a large amount of manganese and of considerable carbon, however, relatively rapid cooling

Jan 9, 1914

By George S. Evans

CERTAIN American operators believe that desulphurizing in the ladle offers a means of increasing blast-furnace and open-hearth yields with the possibility of improvements in quality of the steel. In fact, several producers have experimented with practically all of the known desulphurizing agents, including both standard grades of the alkalies and special preparations that have been offered from time to time during the past several years. Some of these are regularly being used today in large-scale commercial operations, with good results. Also, it is the practice to treat off-sulphur casts in the blast-furnace ladle at a number of plants. It is not known, however, that anyone in the steel industry (American) has ever adequately equipped a plant for desulphurizing blast-furnace metal in an efficient manner as regular operating practice. The purpose of this paper is to illustrate the importance of correct equipment and proper handling for obtaining uniform and efficient results. As will be shown, at the temperature of molten iron the alkalies are instantly neutralized by any free slag present, dissipating their desulphurizing value. Entrained silicates are rapidly washed out of the metal bath by the highly basic soda slags and will be satisfied ahead of desulphurizing reactions with FeS. More or less of the reagent will always be used up through reactions with the refractory lining. Desulphurization will be limited to the action of the free alkali then remaining in the slag. Causes for the erratic results generally found with desulphurizing tests in blast-furnace transfer ladles would include, among other things, variations in the quantity of furnace slag coming down with the metal, and differences in the percentage of kish and entrained silicates in the different casts. As the alkalies instantly unite with any free slags or silicates present, these, with any kish coming off, both dilute the reagent and reduce the surface contact between the slag and metal, thereby retarding the desulphurizing reactions.

Jan 1, 1938

By Charles R. Austin, Carl H. Samans

In an earlier serics of studies on 18-8 stainless steel at 600º, 700º, and 800ºC.l one pretreatment was used throughout; viz., 15 min. in hydrogen at 950°C., followed by an air quench. Several manufacturers of this alloy since have expressed doubt as to the suitability of the temperature employed, recommending instead the more customary Strauss treatment as promising superior results. In this subsequent investigation on the effects of the temperature of pretreatment several interesting points have arisen, which are described in this paper. Previous work on our equipment had shown a marked difference between alloys of "similar chemical composition" that had been manufactured by different companies. Accordingly, one mill-bar length was selected from which to prepare all specimens. It could then be assumed that any marked differences in creep characteristics would be due to effects resulting from variations in the pretreatment of the alloy. The material was furnished by the Allegheny-Ludlum Steel Co. in the form of 5/16-in. dia. rod, finished by air cooling from a mill anneal at 1950°F. (1066°C.). It was analyzed only for the elements shown: carbon, 0.07 per cent; chromium, 18.73; nickel, 9.46; manganese, 0.40. Three pretreating temperatures were chosen, the specimens being held for 15 min. in hydrogen at either: (1) 1150°C., to conform to the recommended Strauss treatment; (2) 950°C., to compare with the results of previous tests; or (3) 75Q°C., to initiate precipitation of carbides in the material before testing. As the test cross sections were only 1/8-in. dia., air cooling followed the annealing treatment. These treatments permitted two direct comparisons: (1) between the 1150" and 950°C. treatments to indicate the effect of grain size when all carbides were probably in solution at the start of the test; and (2) between the 950" and 750°C. treatments to indicate the effect of carbide "nucleation" for similar grain sizes.

Jan 1, 1940

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 Carl H. Samans, Charles R. Austin

In an earlier serics of studies on 18-8 stainless steel at 600º, 700º, and 800ºC.l one pretreatment was used throughout; viz., 15 min. in hydrogen at 950°C., followed by an air quench. Several manufacturers of this alloy since have expressed doubt as to the suitability of the temperature employed, recommending instead the more customary Strauss treatment as promising superior results. In this subsequent investigation on the effects of the temperature of pretreatment several interesting points have arisen, which are described in this paper. Previous work on our equipment had shown a marked difference between alloys of "similar chemical composition" that had been manufactured by different companies. Accordingly, one mill-bar length was selected from which to prepare all specimens. It could then be assumed that any marked differences in creep characteristics would be due to effects resulting from variations in the pretreatment of the alloy. The material was furnished by the Allegheny-Ludlum Steel Co. in the form of 5/16-in. dia. rod, finished by air cooling from a mill anneal at 1950°F. (1066°C.). It was analyzed only for the elements shown: carbon, 0.07 per cent; chromium, 18.73; nickel, 9.46; manganese, 0.40. Three pretreating temperatures were chosen, the specimens being held for 15 min. in hydrogen at either: (1) 1150°C., to conform to the recommended Strauss treatment; (2) 950°C., to compare with the results of previous tests; or (3) 75Q°C., to initiate precipitation of carbides in the material before testing. As the test cross sections were only 1/8-in. dia., air cooling followed the annealing treatment. These treatments permitted two direct comparisons: (1) between the 1150" and 950°C. treatments to indicate the effect of grain size when all carbides were probably in solution at the start of the test; and (2) between the 950" and 750°C. treatments to indicate the effect of carbide "nucleation" for similar grain sizes.

Jan 1, 1940

By O. George Specht, Carl A. Zapffe

IN recent print, some remarkably contradictory statements have appeared regarding the importance to be attached to sponge iron,1-6 a metallurgical commodity whose history goes back at least to the time of Diodorus Siculus in the fourth century B.C. This disagreement, however, expresses the lack of a satisfactory method for producing sponge iron rather than defection in the commodity. The blast furnace is admitted to have certain inherent disadvantages, such as a general unsuitability for magnetite and the heating and blowing of vast quantities of undesirable nitrogen, so that a workable sponge-iron process remains attractive. In this respect, low-temperature gaseous reduction shows especial promise; but confusion persists regarding the factors involved. The present paper, therefore, has three principal divisions: (I) an exhaustive examination of all previous work on low-temperature gaseous reduction, (2) experimentation on the reduction of a magnetite with hydrogen, and (3) development of certain thermodynamic relationships in reduction, with a summarized depiction of the factors in the general process. PREVIOUS INVESTIGATIONS Gaseous media used in the reduction processes under discussion can be classified in three types: (I) H2, (2) CO, and (3) other gases. In the second, the CO is often admixed with H2. The third principally comprises hydrogeniferous gases, such as natural gas and producer gas, and in addition includes chlorine. Because hydrogen therefore features in all three, a study of hydrogen reduction based on investigations using pure hydrogen alone may be incomplete. The present paper reviews the three groups of investigations in the listed order, paying particular attention to hydrogen reduction. For the benefit of future workers, an exhaustive bibliography has been prepared and similarly classified. GROUP I: REDUCTION WITH HYDROGEN Equilibria Although the present problem is specifically one of kinetics, a first consideration is the equilibrium of the system, since the reactions to be studied comprise that equilibrium, and their direction and end points are defined by it. The historic development of these researches is interesting and informative.

Jan 1, 1946

By W. E. Remmers

The fact that gray iron increases in volume, cracks and distorts upon repeated heating and cooling is rather conlmon knowledge. In ingot molds, Diesel engine pistons, carburizing boxes, continuous furnace parts, grate bars, stoker parts, and all castings that are subjected repeatedly to high and low temperatures, the phenomenon of growth presents a vital problem. Ingot molds distort and produce cracks which result in seams or laps and later appear as defects in the finished product. The heads of Diesel pistons frequently fail by cracking in a stellar shape. This is attributed usually to the result of permanent growth. Distortion and change of dimension of furnace parts frequently renders them entirely unusable. In chain grate stokers, mechanical difficulties frequently are caused by the growth of the links. In proper operation these links should never attain a temperature sufficiently high to start growth; nevertheless, some have grown in. on an 8-in. length when improperly operated. Even though the phenomenon is generally known there still exists a deficiency in the explanation of the mechanism of this growth. The field of investigators of this subject has a decided variation in opinion concerning the causes. The problem is of sufficient importance therefore to warrant further consideration. Review of Published Work Since the published work, particularly the European, contains much detail, only the outstanding results and conclusions of the investigators will be reviewed. The pioneering investigations of Outerbridge in 1904 and 1905 brought forth the conclusion that growth was not a function of chemical or crystallographic changes but was a result of the formation of fine hair cracks. These cracks are supposedly due to a nonuniformity of thermal expansion and contraction which ruptures the structure of the material. More recently Benedicks and Lofquist presented a purely mechanical theory, which is similar to that of Outerbridge. These investigators believe the temperature gradient from the outside to the center of the cast piece causes a contraction of the outer layers on passing

Jan 1, 1931

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 David W. Brunton

From the old-fashioned " grab-sample " to the modern timing-device, which takes a machine-sample with mathematical precision, there is a wide gap, which was only crossed by many years of toil and unremitting endeavor. Even to-day, notwithstanding the advancement in the art, " grab-sampling " is still practiced—sometimes to afford the unscrupulous mine-promoter a basis for fairy-tales with which to entrap the too-gullible investor, and often by milling and smelting companies to determine the amount of moisture in custom-ores. The latter practice is almost as reprehensible as the former, and it causes more trouble and ill-feeling between seller and buyer than all other factors put together. -NO reputable concern to-day would think of attempting to determine by grab-sampling the amount of gold, silver, lead, or copper contained in an ore, and yet many buyers expect the miner to accept the results of grab-sampling in the determination of the amount of water contained in the ore, forgetting that accurate results are just as necessary here as in the determination of the metals, because the result determines the percentage of weight of the ore which shall be excluded and considered to have no value whatever. Samples for the determination of moisture should be taken with as great care as samples for the determination of metallic content, and in order to avoid the extra expense of a separate operation moisture-samples should be taken from the sample-safe. As the sample reaches the sample-bin in a smaller stream and by a more circuitous route than the " reject" travels in its path to the outgoing car, it loses more moisture en route, and a constant should be added to compensate for this difference. Carefullg ,con ducted experiments have shown that the differ.elice in loss of moisture between the two routes does not exceed 10 per cent. in summer and 7 per cent. in winter. For instance,

Jan 1, 1910

By Rex B. McLellan

Studies of the eyuilibrzum between ferrite and austenite with gas mixtures (CO + CO2 and H2 + CHe) have been used as a means of deducing the energy and vibrational entropy of carbon atoms in dilute interstitial Fe-C solutions. A simple model for dilute interstitial solutions is given which enables a solubility equation for the equilibrium between the gas mixtures and the solid to be deduced. This solubility equation is used to estimate the partial In this work measurements of the equilibrium between dilute solid solutions of carbon in iron and gaseous mixtures of CO2 + CO and CH4 + Hp have been analyzed using theoretical solubility equations deduced from a knowledge of the thermodynamic parameters of the gas mixtures and an appropriate model for the solid solution. The solubility equations are deduced by equating the chemical potential of carbon atoms in the gas thermodynamic functions of dilute Fe-C solutions from the measured equilibrium between the solid and the gas mixtures. It is shown that the vibra-tional entropy of a carbon atom in a and y iron is smaller than the corresponding entropy 01. a nitrogen atom in solid solution inferrite or austenite and that there is little difference between the vibrational entropies of both nitrogen and carbon atoms in ferrite and austenite. and solid phases. The chemical potential of carbon in the gas is found from a simple statistical mechanical analysis of the gas mixtures utilizing spec-troscopic data while that for carbon in the interstitial solution is found from a model in which the carbon atoms act as bound oscillators distributed in a random fashion in the solution. The solid solution is dilute enough to enable solute-solute interactions to be ignored. Thus the configurational entropy of the solution is ideal but the mixing entropy contains additional excess terms due mainly to the vibrational changes occurring on solution formation. The partial excess entropies (and the partial energies) do

Jan 1, 1965

By O. George Specht, Carl A. Zapffe

In recent print, some remarkably contradictory statements have appeared regarding the importance to be attached to sponge Iron,1-6 a metallurgical commodity whose history goes back at least to the time of Diodorus Siculus in the fourth century B.C. This disagreement, however, expresses the lack of a satisfactory method for producing sponge iron rather than defection in the commodity. The blast furnace is admitted to have certain inherent disadvantages, such as a general unsuitability for magnetite and the heating and blowing of vast quantities of undesirable nitrogen, so that a workable sponge-iron process remains attractive. In this respect, low-temperature gaseous reduction shows especial promise; but confusion persists regarding the factors involved. The present paper, therefore, has three principal divisions: (I) an exhaustive examination of all previous work on low-temperature gaseous reduction, (2) experi- mentation on the reduction of a magnetite with hydrogen, and (3) development of certain thermodynamic relationships in reduction, with a summarized depiction of the factors in the general process. PREVIOUS INVESTIGATIONS Gaseous media used in the reduction processes under discussion can be classified in three types: (I) H2, (2) CO, and (3) other gases. In the second, the CO is often admixed with H2. The third principally comprises hydrogeniferous gases, such as natural gas and producer gas, and in addition includes chlorine. Because hydrogen therefore features in all three, a study of hydrogen reduction based on investigations using pure hydrogen alone may be incomplete. The present paper reviews the three groups of investigations in the listed order, paying particular attention to hydrogen reduction. For the benefit of future workers, an exhaustive bibliography has been prepared and similarly classified. Group I: Reduction with Hydrogen Equilibria Although the present problem is specifically one of kinetics, a first consideration is the equilibrium of the system, since the reactions to be studied comprise that equilibrium, and their direction and end points are defined by it. The historic development of these researches is interesting and informative.

Jan 1, 1947

By O. George Specht, Carl A. Zapffe

In recent print, some remarkably contradictory statements have appeared regarding the importance to be attached to sponge Iron,1-6 a metallurgical commodity whose history goes back at least to the time of Diodorus Siculus in the fourth century B.C. This disagreement, however, expresses the lack of a satisfactory method for producing sponge iron rather than defection in the commodity. The blast furnace is admitted to have certain inherent disadvantages, such as a general unsuitability for magnetite and the heating and blowing of vast quantities of undesirable nitrogen, so that a workable sponge-iron process remains attractive. In this respect, low-temperature gaseous reduction shows especial promise; but confusion persists regarding the factors involved. The present paper, therefore, has three principal divisions: (I) an exhaustive examination of all previous work on low-temperature gaseous reduction, (2) experi- mentation on the reduction of a magnetite with hydrogen, and (3) development of certain thermodynamic relationships in reduction, with a summarized depiction of the factors in the general process. PREVIOUS INVESTIGATIONS Gaseous media used in the reduction processes under discussion can be classified in three types: (I) H2, (2) CO, and (3) other gases. In the second, the CO is often admixed with H2. The third principally comprises hydrogeniferous gases, such as natural gas and producer gas, and in addition includes chlorine. Because hydrogen therefore features in all three, a study of hydrogen reduction based on investigations using pure hydrogen alone may be incomplete. The present paper reviews the three groups of investigations in the listed order, paying particular attention to hydrogen reduction. For the benefit of future workers, an exhaustive bibliography has been prepared and similarly classified. Group I: Reduction with Hydrogen Equilibria Although the present problem is specifically one of kinetics, a first consideration is the equilibrium of the system, since the reactions to be studied comprise that equilibrium, and their direction and end points are defined by it. The historic development of these researches is interesting and informative.

Jan 1, 1947

By E. Miller, J. M. Eldridge, K. L. Komarek

Activities of magnesium in liquid Mg-Sn alloys have been determined between 5 and 90 at. pct Sn and 990" and 1290°K by an improved isopiestic method wherein tin specimens, heated in a temperature gradient and contained in crucibles of special geometry, were equilibrated with magnesium vapor in a closed titanium system. The crucibles were designed so that the equilibrium compositions of the specimens were satisfactorily preserved on termination of the experimental runs by quenching. The activity values are in excellent agreement with those predicated on the phase diagram and allowed a delineation of the solidus curve of the compound Mg2Sn near its melting point. EQUATIONS have been recently derived relating the chemical potentials of the components to the liquidus and enthalpy data for binary systems exhibiting one congruently melting compound.' The liquidus curve of the Mg-Sn system between the eutectics was carefully redetermined and the thermodynamic properties thus calculated were in reasonably good agreement with values derived from electromotive-force measurements of an,' but differed greatly from the iso-piestically determined values of Ashtakala and Pid-geon.3 The present study was initiated: a) to resolve the discrepancies; b) to develop a method for measuring activities in systems having volatile (and possibly highly reactive) components; and c) to use the method in a general investigation of the thermodynamic properties of the homologous series of Mg-Group IVb systems, i.e., Mg-Pb, Mg-Sn, Mg-Ge, and Mg-Si. This paper describes the results for the Mg-Sn system. An isopiestic technique, originally developed by Herasymenko 4 and adapted for alloys having a component of high reactivity and low volatility,5-8 was modified in this study by using crucibles designed to preserve the equilibrium composition of highly volatile liquid specimens on quenching from high temperatures. Tin specimens, contained in tightly covered graphite crucibles and heated in a temperature gradient, were equilibrated with magnesium vapor of fixed pressure from a magnesium reservoir kept at constant temperature in a previously evacuated and sealed titanium tube. During equilibration magne-

Jan 1, 1967