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By J. D. Wright

INTRODUCTION The Endako deposit was first explored in 1926, but development waited until the early nineteen sixties. It first came under the control of Placer Development in 1963, and early in 1964 a decision to bring it into production was reached. The deposit is located near the geographic center of British Columbia, and is served by an east-west communication system including a paved highway, mainline railway and good telephone, teletype, and computer facilities. The plant area is shown in Figure 1. The operation is known as the Endako Mines Division of Canex Placer Limited of Vancouver. First production was achieved in June, 1965, at a nominal rate of 10,000 tons per day, but it soon was closer to 15,000 tons per day. In 1967, two new grinding and flotation, sections brought capacity to the present rate of approximately 27,000 tons per day. With mill heads of around 0.15 percent MoS2, production is about 14,000,000 pounds of molybdenum per year. A flowsheet of the operation is given in Figure 2. A legend for this flowsheet is given in Table 1. Published ore reserves are estimated at 214,500,000 tons at an average grade of 0.143 percent MoS2. PRIMARY CRUSHING The 85 or 100-ton haulage trucks dump over a grizzly into a 42 inch x 65 inch C.A.C. (Canadian Allis Chalmers) gyratory crusher. The

Jan 1, 1976

By Samuel B. Christy

The present paper is a continuation of a study of the reductionworks of New Almaden, the first part of which was published under the title " Quicksilver-Reduction at New Almaden," in the Transactions of this Society, vol. xiii., p. 547.* Frequent reference will be made to some of the data there given. The following is an outline of the contents of this paper: I. Condensing appliances used at New Almaden: a. Brick condensers, b. Iron condensers—flues and " water-backs," c. Glass and wood condensers, d. Friction-coudensers—filters and revolving screens, e. Flues, towers, and chimneys. II. Analysis of condensing-systems. III. Temperature of condeusers. IV. Product of condensers. V. Treatment of soot. VI. Losses of treatment: a. Nature of losses, b. Composition, weight, and volume of dry gases, c. Volume of wet gases, d. Specific weight of quicksilver vapor, e. Vapor-loss at various temperatures. VII. Comparison with New Almaden practice. VIII. Comparison with results at Idria, Austria. IX. Comparison with results at Almaden, Spain. X. Future improvements in quicksilver-condensation. I. Condensing Appliances. The complete condensation of mercurial fumes in a large way presents numerous practical difficulties, familiar to all who have had to retort amalgams. In condensing the quicksilver-fumes discharged

Jan 1, 1886

By William Kelly, F. H. Armstrong

The object of this paper is to describe the electric equipment at the iron-ore mines of Penn Iron Mining Co., Vulcan, Mich. and of Republic Iron Co., Republic, Mich.; to give the results of tests; and to discuss the methods in use from an operating as well as from an efficiency standpoint. Electricity was introduced at the Penn mines for pumping, hoisting, and compressing air in the spring of 1907, upon the completion of a hydro-electric plant built by that company on the Menominee river about 4 miles from the mines. This plant was described in a paper1 presented before the Lake Superior Mining Institute. A paper2 presented at a meeting of the same Institute describes some of the operating features, and the safety devices of the electric hoist at the Curry shaft were briefly described in the Proceedings of the First Co-operative Safety Congress held under the auspices of the Association of Iron and Steel Electrical Engineers at Milwaukee, Wis., Sept. 30 to Oct. 5, 1912. Generating PoweR Plants After the success of electrical operation was assured, a second set of water wheels and generator was installed at the falls, for which provision had been made in the original design and in the construction of the foundations, and later three additional wires were added to the main transmission line, doubling its capacity and reducing the line loss. The general conditions of this installation are particularly favorable for hydro-electric operation. In the neighborhood of three-fourths of the power used is for mine pumping, which in the main is regular and continuous. For air compressing, power is used for about 18 hr. a day for five days, and 9 hr. for one day in the week, though occasionally when shaft sinking is going on a very small amount of compressed air may be

Jan 1, 1915

By E. A. Gulbransen, W. S. Wysong

THE behavior of tungsten and its surface oxides in oxidizing and reducing atmospheres and in high vacua at elevated temperatures is a question of considerable technical importance. The use of tungsten as a metal or as an important component in alloys in high temperature oxidizing atmospheres has been limited because of the unprotective nature of its oxide film and the volatility of its oxide. This paper will present results of a microbalance study1,2 of the following problems: (I) the oxidation behavior in the temperature range of 25 to 550°C (2) the reduction with pure hydrogen of thin oxide films formed on tungsten, and (3) the volatility of thin oxide films on tungsten. Tungsten is an interesting metal to study for the following reasons: (1) although the oxide to metal volume ratio is greater than one, the oxide is not considered protective, (2) the metal readily oxidizes at temperatures from 300° to 550°C (3) the oxides W02 and WO3 are reduced at temperatures as low as 500°C. by hydrogen, and (4) the oxide W02 is volatile at temperatures from 800 to 1100°C. LITERATURE The oxidation of tungsten in its thin film range has not been studied critically. In the thick film range Dunn3 has made the only systematic study. He found the oxidation rate to obey the parabolic rate law in the temperature range of 700 to 900°C. The temperature variation of the oxidation rate constant was found to follow an exponential law of the Arrhenius type. An inflection was noticed in the temperature plot of the rate law constant at 850 to 900°C. This was attributed to a phase change in the oxides. Scheil4 has studied the oxidation rate at 500 and 700°C over long periods of time and found a linear rate law. This result was interpreted as evidence for the presence of a nonprotective film. Pilling and Bedworth5 analyses of the oxide volume to metal volume ratio would indicate that a compact protective film should form. McAdam and Geil6 have studied the oxidation of tungsten in the thin film range using the interference color method. A parabolic rate law was found. Their curves showed that tungsten oxidizes faster than nickel but more slowly than iron. The lattice structures found in the oxidation of tungsten surfaces have been studied by Hickman and Gulbransen.7 They have reported that W03 is the stable oxide in contact with the metallic substrate up to approximately 600°C while W02 forms first at 700°C. Hägg and Magneli8 have recently reported a study of the lattice structures observed in the tungsten oxides using the X-ray diffraction method. In addition to an a-phase W03 and a d-phase W02, they reported the existence of two new phases. A ß' phase, homogeneous between

Jan 1, 1947

By Henning Nielsen

SIX weeks ahead of schedule, the International Nickel Co. of Canada Ltd. has brought a 30-mile rail line into the newly born town of Thompson, Manitoba. Its construction spurs the development of a rich new mining region slated to become the world's second largest nickel-producing area-exceeded only by Inco's Sudbury, Ont., workings. Two mines, the Thompson and the Moak Lake, will be opened to meet International Nickel's scheduled annual production goal of 385 million lb of refined nickel by 1961. Accomplishment of this aim will mean an additional 75 million lb of the metal available to consumers. In addition, stepped-up out- put of Inco's Sudbury holdings may increase this figure by another 25 million lb. (For an earlier report on these developments see MINING ENGINEERING News, January 1957).

Jan 12, 1957

By Sidney Powers

CONTENTS PAGE Distribution of fields 4 History of development 6 Origin of oil 7 Structure,, accumulation and migration 8 Reservoir rocks 9 Methods of drilling and exploration to Oil-field statistics 12 Description by regions: United States: Appalachian region 12 East-central states 17 Kansas 18 Oklahoma 19 Texas 24 Arkansas 32 Louisiana 33 Mississippi -.. 34 Rocky Mountain region 34 California : 37 Canada 41 Mexico 43 Cuba 46 Bibliography 46 THE purpose of this brief account of the occurrence of petroleum in North America is to make available to those who have a knowledge of geology, but who are not engaged in the petroleum industry, a few salient facts about the location of oil and gas fields, their productivity, the important structural types of accumulation and the age of the rocks containing petroleum. A few useful data and statistics are furnished, yet not complete statistics that are available elsewhere. Geology has been treated in simple terms because the reader is presumed to have little interest in the names of formations and of oil sands. Mineral deposits are more or less analogous. Whether oil or metals, minerals are found in rocks, largely in sedimentary rocks which carry water or have at one time carried it. A genetic or accumula-

Jan 1, 1931

By T. W. Bossert

MELTING is the initial step in the fabricating of all aluminum and aluminum-alloy products. Its function may be considered as threefold: to improve the metal quality, to adjust the composition, and to change the form to that required for subsequent fabrication. Because the melting operation is generally somewhat removed from the final product fabrication, its importance is frequently overlooked. Melting equipment and melting procedures can reflect materially on fabricating procedures as well as on quality and cost of final product. The selection of equipment and the establishment and control of melting procedures, therefore, should be given careful consideration. It is the purpose of this paper to present the various factors that should be considered in establishing melting procedures and in selecting melting equipment. Certain of these are the result of the inherent characteristics of aluminum and can be treated rather specifically. Others depend on the particular production requirements and hence will have to be considered more generally. This paper is intended to cover only the melting of solids, as differentiated from fines, such as borings, turnings, and sawdust. The melting of fines, in many respects, is a subject that should be treated by itself, and practices for melting fines are by no means as standardized as are those for melting solids. The melting of fines is today the subject of considerable developmental interest; hence practices discussed today may soon be replaced by new or improved ones. CHARACTERISTICS OF THE METAL THAT AFFECT MELTING Aluminum and aluminum alloys possess several inherent characteristics that affect the melting problem. Of the physical properties, density, heat content, thermal conductivity, emissivity, and melting temperatures are important because of their effect on equipment design. A list of such properties for commercially pure aluminum is given in Table r, compared with similar properties for iron and copper. The low density of aluminum as well as of the aluminum alloys is of material advantage in the design of melting equipment, in that such equipment can be considerably lighter than similar equipment for handling the heavier metals. The density, however, particularly of the molten metal, is not greatly different from that of the oxides and other nonmetallic materials that develop or become part of the melt during the melting process. Separation of such nonmetallics is not as rapid a process as with some of the other metals, and consideration of this must be made in establishing melting procedures. Sufficient holding time to permit such materials to separate out and, in some cases, fluxing treatments to aid the separation, are required. Since some of these nonmetallics settle to the bottom of the melt, provision should also be

Jan 1, 1946

NEW MEMBERS The following list comprises the names of those persons who became. members during the period Sept. 10, 1918, to Oct. 10, 1918. ADDISON, HERBERT, Vice-pres. and Mgr., Big Horn Collieries Co., 412 Colorado Bldg., Denver, Colo. ALLAN, .ANDREW, JR A. Allan & Son, Harrison, N. J. AMI, HENRY M., Charge of War Metals and Minerals, British Embassy, Washington, D. C. ALTHAR, HOMER C., Mill. Engr., The Lorain Coal & Dock Co., Bridgeport, Belmont Co., Ohio. BASER, JOHN T Pres., J. T. Baker Chemical Co., Phillipsburg, N. J. BARBA, W. P., Lieut. Colonel, Ordnance, U. S. A., 2301 Connecticut Ave., Washington, D. C. BENSON, JOHN PATS Min. Engr., Aurora Cons. Mines Co., Aurora, Nev., BOSWELL, H. F Resident Inspector, Southern Railway System, St. Louis, Mo. BRAUCHER, PETERS., Foundry Mgr., Philadelphia & Reading Ry. Co., Sixth & Perry St., Reading, Pa.

Jan 11, 1918

By H. H. Campbell

Many attempts have been made to write a formula by which to calculate the strength of steel from its chemical composition, but most of these endeavors have failed because there were too many disturbing conditions. It is idle to collect from the pages of trade-papers, books, or the proceedings of scientific societies, a multitude of observations. The combination of such results will simply show that steel of the same composition will vary in tensile strength through wide limits—a fact that has been known for generations. That cold-working, overheating, and many another form of heat-treatment alter fundamentally the strength of steel, is ancient history, although it is only recently that the microscope has pointed out the road to an explanation of the phenomena. It mag be urged that the microscopic structure must betaken into consideration in any formula giving the ultimate strength, but from the standpoint of the present investigation this is unnecessary. We are trying to determine primarily, not what changes in ultimate strength may be made by variations in the condition of carbon, but what effect is produced by changes in the amount of carbon, when its condition remains constant. For such an inquiry, in order that the condition of the carbon should remain as nearly uniform as possible, it is essential that all testrpieces be made under the same conditions; and it is believed that the tests described in this paper satisfy that requirement. The investigations were made at the works of the Pennsylvania Steel Company, Steelton, Pa.; the ingots from which the tests were made were 6 in. square in every case; they were heated in the same furnace and forged at the same ham-

Jan 1, 1905

By E. C. W. Perryman

The recovery of X-ray line broadening, hardness, and electrical resistivity from cold worked AI-Mg alloys has been investigated. The results, together with those from density measurements, suggest that magnesium atoms freeze in the excess vacancies formed by cold working, and that this affects the climb of dislocations during the recovery process. PREVIOUS work1, " has shown that while 1 pct Mg increases the activation energy for recrystalliza-tion, it decreases the activation energy for the recovery of mechanical properties and decreases the subgrain size both after cold working and annealing. A similar result has been reported by Varley2 for an A1-2 pct Mg alloy. With plastic deformation at high temperatures, McLean and Farmer' and Rachinger have found that magnesium appears to retard the motion of dislocations and, furthermore, they find little or no effect of magnesium on the size of subgrains formed during high temperature deformation. In view of the apparent contradictions as to the effect of magnesium on subgrain size, the recovery process in Al-Mg alloys has been investigated more thoroughly by studying the annealing out of X-ray line broadening, hardness, and electrical resistivity from alloys cold worked at room temperature. Material Used—The chemical analyses of the alloys are given in Table I. Fabrication—The material used was cold rolled 20 pct at room temperature, the grain size prior to the last cold rolling operation being similar to that used in previous work; i.e., 230. The experimental procedure for annealing, determination of X-rav half-veak breadth. hardness measurement, electEica1 resistivity, and density and metallographic examination was exactly the same as previously described." Variation of X-Ray Half-Peak Breadth with Annealing Time—Isothermal annealing curves at 100°, 200°, and 250°C were obtained for material cold worked 20 pct. The half-peak breadth of the (333) Ka, line directly after cold working is shown as a function of magnesium content in Fig. 1. Only with the 2.87 pct Mg alloy was overlapping of the a, and n.. reflections observed to any appreciable extent. To separate these, Rachinger's method' was used. Typical isothermal annealing curves are shown in Figs. 2 and 3 for 100" and 200°C, respectively. These curves are similar to those obtained previously for super-purity aluminum except that the

Jan 1, 1957

Jan 1, 1929

By W. D. Forgeng, D. Beregekoff

In the routine examinatlion of a wide variety of metal specimens it is sometimes necessary to have special methods of polishing in order to retain and reveal certain details in each specimen. Among such special cases is the retention of graphite in malleable and gray cast irons, the preservation of all types of non metallic inclusions in both hard and soft steels, obtaining a scratch-frec surface with soft metals, and avoiding the usual relief effects with very hard specimen. such as tool metals c3o1ltaining various carbide and nitride phases. It, is the purpose of this paper to give an account of some of these special polishing methods in use at the Union Carbide and Carbon Research Laboratories. The polishing procedures outlined have been found to give uniform results. It is obvious that only general rules and the most important working details can be given here. Following these rules, the polisher can obtain satisfactory results if he possesses the necessary patience and has a sincere desire to give as nearly perfect a finish as possible to his work. Procedure The specimen is flattened with considerablecare on a file or sharp cutting sanding belt, since the initial production of a flat surfacc greatly facilitatcs subscqucnt polishing. The polishing motors have two speed., 600 and 1200 r.p.111. ,It higher speeds specimens arc likely to he over-Ileated, therefore the high speed is used only when a saving of time is important. The following abrasive papers are used consecutively: Yo. 2, So. 1, No. 0, No. 00 and No. 000. The final wet polishing is done oil a cloth-covercd metal disk. Woolen broadcloth of the best quality and capable of resisting severe pressure is most commonly used on the last lap. . polishing felt of the type used for polishing optical glass has been found equally satisfactory and is much stronger than broadcloth. For retaining inclusions and graphite, a hard cloth with very little residence, such as

Jan 1, 1939

By D. Beregekoff, W. D. Forgeng

In the routine examinatlion of a wide variety of metal specimens it is sometimes necessary to have special methods of polishing in order to retain and reveal certain details in each specimen. Among such special cases is the retention of graphite in malleable and gray cast irons, the preservation of all types of non metallic inclusions in both hard and soft steels, obtaining a scratch-frec surface with soft metals, and avoiding the usual relief effects with very hard specimen. such as tool metals c3o1ltaining various carbide and nitride phases. It, is the purpose of this paper to give an account of some of these special polishing methods in use at the Union Carbide and Carbon Research Laboratories. The polishing procedures outlined have been found to give uniform results. It is obvious that only general rules and the most important working details can be given here. Following these rules, the polisher can obtain satisfactory results if he possesses the necessary patience and has a sincere desire to give as nearly perfect a finish as possible to his work. Procedure The specimen is flattened with considerablecare on a file or sharp cutting sanding belt, since the initial production of a flat surfacc greatly facilitatcs subscqucnt polishing. The polishing motors have two speed., 600 and 1200 r.p.111. ,It higher speeds specimens arc likely to he over-Ileated, therefore the high speed is used only when a saving of time is important. The following abrasive papers are used consecutively: Yo. 2, So. 1, No. 0, No. 00 and No. 000. The final wet polishing is done oil a cloth-covercd metal disk. Woolen broadcloth of the best quality and capable of resisting severe pressure is most commonly used on the last lap. . polishing felt of the type used for polishing optical glass has been found equally satisfactory and is much stronger than broadcloth. For retaining inclusions and graphite, a hard cloth with very little residence, such as

Jan 1, 1939

By A. W. Peake, F. O. Prior

Considering the great advance in the development and application of electricity, it is not strange that eventually a big field for its use has been found in oil-field operations. So far as is known, the first electric drive in oil-field operations was in the Russian field of Baku in 1900. The first application in this country was made by the South Penn Oil Co. near Folsom, West Va. in 1903. In 1916, electric power was first used in the Burma fields of India for drilling and pumping. Between 1916 and 1922, The Empire Gas & Fuel Co. made the first large electrical installation in the Mid-Continent fields. But although the first application was made 27 years ago, it is only within the last 10 years that oil companies have begun to look upon its use with much favor. Within the last few years, there has been a steady increase in the use of electricity in the oil fields. The first application of electricity for oil-field operations in Wyoming was in the Lander field in 1919; the second was in 1924 in Salt Creek; and the third, and last to date, was made by the Continental Oil Co. in the Big Muddy field during 1926. Lander Field The electrification of oil-field operations in Wyoming was initiated by J. W. Steele, superintendent of the Producers & Refiners Oil Corpn., in the Lander field in 1919. At that time, 32 wells were being pumped from five band-wheel powers, with oil engines as the prime movers. Eight barrels of fuel oil were used for power per day and at the price of 90 c. per bbl. the fuel bill was $36 per day. It was decided to try a 15 to 35-hp. oil-field motor on one of these powers. Electric power was generated with steam at the old Wind River refinery station. This test was so successful that in 1920 all five powers were equipped with 15 to 35-hp. oil-field motors, the power being obtained from the Sinks Canyon hydroelectric station. Four of these powers pumped wells at an average depth of 1450 ft., and the fifth pumped wells at an average of 2100 ft. In 1920, the average production per day from the 32 wells was 325 bbl. The power bill on the

Jan 1, 1928

By Sidney Powers

CONTENTS PAGE Distribution of fields 4 History of development 6 Origin of oil 7 Structure, accumulation and migration 8 Reservoir rocks 9 Methods of drilling and exploration 10 Oil-field statistics : 12 Description by regions: United States: Appalachian region ; 12 East-central states 17 Kansas 18 Oklahoma : 19 Texas : 24 Arkansas : 32 Louisiana 33 Mississippi ....... 34 Rocky Mountain region : 34 California 37 Canada 41 Mexico 43 Cuba 46 Bibliography 46 THE purpose of this brief account- of the occurrence of petroleum in North America is to make available to those who have a knowledge of geology, but who are not engaged in the petroleum industry, a few salient facts about the location of oil and gas fields, their productivity, the important structural types of accumulation and the age of the rocks containing petroleum. A few useful data and statistics are furnished, yet not complete statistics that are available elsewhere. Geology has been treated in simple terms because the reader is presumed to have little interest in the names of formations and of oil sands. Mineral deposits are more or less analogous. Whether oil or metals, minerals are found in rocks, largely in sedimentary rocks which carry water or have at one time carried it. A genetic or accumula-

Jan 1, 1931

By R. B. Muter, W. C. Grady, T. D. Wheelock, D. G. Chedgy

INTRODUCTION Topics of special interest, such as preparation plant flowsheets and noise pollution, are described in this chapter along with a discussion of non- state-of-the-art processes such as chemical cleaning, high intensity magnetic separation, and bacterial oxidation. PREPARATION PLANT FLOWSHEETS by RICHARD B. Muter In determining the layout or combination of unit operations to be utilized in a modern preparation plant several factors must be taken into account.

Jan 1, 1979

NEW MEMBERS. The following list comprises the names of those persons who became members during the months of July and August, 1913: Members. ALDERSON, VICTOR C., Prest. of Colorado School of Mines :.Golden, Colo. ALLEN, JOSEPH W., Secy. & Treas. International S. & R. Co;, 42 Broadway, New York, N. Y. AMMON, ROBERT, Chief Sampler B. & M. Reduction Wks., Anaconda Copper Min.Co., Great Falls, Mont. BARBER, RAYMOND J., Min. Engr 234 Newbury St., Boston, Mass. BARDWELL, EARL S., Genl. Concen rator Foreman Boston & Mont. Reduction Plant, Great Falls; Mont.

Jan 9, 1913

By Rodney P. Smith

The diffusivity of carbon (0.1 wt pct C) in Fe-Nz alloys (0 to 100 pct Ni) has been determined for the temperature range 860° to 1100°C. As a function of nickel content, the diffusivity has a maximum near 60 pct Ni (the maximum diffusivity being about 1.3 times that in the absence of nickel); the activation energy has a maximum between 40 and 50 pct Ni and a maximum between 80 and 90 pct Ni. The difference between the minimum activation energy and that in iron is about 3000 cal pev g-atom; Do has a minimum between 40 and 50 pct Ni and a maximum between 80 and 90 pct Ni. The results cannot be rationalized by an approximate thermodynamic treatment. THE diffusivity of carbon has been determined in a number of iron alloys over a limited concentration range. It seemed desirable to investigate a system which allows an extended range of alloy composition within a single-phase region. The Fe-Ni system is ideal in this respect, in that all alloys from 100 pct Fe to 100 pct Ni are fee in a convenient temperature range.&apos; The carbon diffusivity was determined by a decar-burization method. The experimental procedure was identical with that used to determine the diffusivity of carbon in y Fe-Co alloys.2 The experimental data are given in Table I. A small correction (order of a few percent) has been made to the measured carbon loss to correct for the carbon lost from the ends of the cylinders.&apos; Since the diffusivity of carbon varies with carbon content the measured diffusivity is an average value for a carbon content between zero (surface) and that at the center of the sample at the end of the decarburization periods. In making the correction in D to 0.1 wt pct C it is assumed that the measured D corresponds to the arithmetical mean of the carbon content at the surface and at the center of the sample at the end of the decarburization period.3 Since this correction is small (<4 pct in D) and since for our decarburization times the changes in carbon content at the center of the sample was small the mean carbon content could have been taken as half the initial value. It is further assumed that the change in D with carbon content for the alloys is the same as that for the diffusion of carbon in iron. From the data of Wells, Batz, and Mehl4 and of smith5 the correction of D from the mean carbon content to 0.1 wt pct C is 0.3 (0.1 - mean wt pct C). The results for iron are given in Ref. 2. Within the experimental error log Do.l%C for each alloy is a linear function of 1/T; the constants for the equation determined by the method of least squares are given in Table I. The deviations of the experimental points from the least-squares line are of the order of 2 pct in D. A comparison of our results for the diffusivity of carbon in nickel with those of other investigations is shown in Fig. 1. The lower curve in Fig. 1 is a linear extrapolation of values calculated* from the equation of Diamond6 for the relaxation time (temperature range 100° to 500°C). The results indicate a small increase in the activation energy over the temperature range 100° to 1400°C; however, it is difficult to say whether the change in Q is real or experimental error. Certainly the change in Q is less than the variation of 5 kcal per g-atom in the diffusivity of carbon in a iron.6 The experimental data for all the alloys are plotted in Fig. 2. As a function of nickel content the diffusivity has a maximum near 60 wt pct Ni at all temperatures investigated and possibly a minimum between 80 and 90 wt pct Ni for temperatures below 1000°C. The activation energy, Q, and log Do are plotted as a function of the nickel content in Fig. 3. Due to the limited temperature range of our experiments neither Q nor Do can be determined precisely; the activation energies appear to be consistent to ±0.3 kcal per g-atom; however the deviation from the absolute values may be considerably larger, see Table II. The Do values probably have little significance. The solid line for Do in Fig. 3 represents the values required to reproduce the experimental values for D when Q has values represented by the upper solid line The diffusivity of carbon may be expressed in terms of the mobility B22, the activity coefficient r2,

Jan 1, 1967

By Harvey Brooks

Jan 1, 1963

By J. V. Emmons

It has long been known that the outside skin of tool steel frequently exhibits properties widely different from the interior of the mass.

Jan 1, 1915