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By Paul Giesecke

Since most modern metallurgical plants are operated continuously and on a large scale, successful operation at maximum efficiency demands that an accurate knowledge of the performance at each stage of the process be available at all times. Quantitative analyses provide the most practical process guides, and it is essential to have analytical procedures that combine accuracy and speed. In continuous plant operations, large losses may occur if the time interval between the development of trouble at any stage and its recognition and correction is great. Many metallurgical plants are using rapid colorimetric and spectrochemical methods of analyses for control purposes. So-called "color coppers" may be cited as an example of the colorimetric methods, in contrast with- the routine use of the ultraviolet spectrograph for the analysis of steels.42 By means of this more refined spectrochemical procedure, a complete quantitative analysis of the molten metal is obtained every few minutes. During the past two years the Physics Division and the Ore Dressing Laboratory of the American Cyanamid Company's Stamford Research Laboratories have collaborated in a study of the use of spectrochemical methods for the analysis of various metallurgical products. New methods have been developed, which have proved of practical value in plant operation. The following pages give a general review of the principles of spectrochemical methods and also the details of several specific analyses. Principles of Spectrochemical Analysis In general, it can be said that a visible light spectrochemical analysis can be performed for any ion or molecule that is naturally colored, or that can be made to react with another to produce a colored salt or complex. Whereas transmission measurements in the ultraviolet and infrared portions of the spectrum are most useful for the analysis of organic molecules, * visible light measurements are of particular value for metal salts. Such elements as copper, manganese, cobalt, nickel, iron, molybdenum, vanadium, chromium, phosphorus, mercury, zinc, lead, and a great many others, can now be determined with a high degree of sensitivity, accuracy and dispatch. From the simplest of qualitative determinations, color analyses have been improved to such an extent that, at the present time, through the use of recording spectrophotometers, hundreds of accurate quantitative analyses can be performed by a single analyst during an 8-hr. day after the standardization curves have been established for the ions to be determined.

Jan 1, 1947

By D. R. Mitchell

FOR the second consecutive year, attendance at the Coal Division sessions far exceeded exoectations. Those in charge were continually faced with problems of finding seats and space for attending members. 115 seats were set - II~ for the annual luncheon meeting of the Division and approximately 175 members showed un. Since the hotel management would not serve more than the 115 it meant that 60 members were forced to eat elsewhere. This created hard feelings with some members. How- ever, officials of the Division were not able to obtain in advance any indication of this overflow crowd, but are suggesting to the New York Office that some means other than ticket sales be adopted to obtain an estimate of Division luncheon and dinner attendance. Members could be circularized prior to he meeting or they could be checked when registering as to the events they expect to attend. Under the inspiring leadership of Cadwallader Evans, Jr., Chairman, the Coal Division had a phenomenal growth during the year. Reporting at the luncheon meeting, Newel1 Alford stated that approximately 190 new members had been obtained. A few more years of continuing increase at this rate will make the Coal Division one of the largest Divisions in the Institute.

Jan 1, 1944

By JAMES H. McGRAW

P UBLZCLTY and engineers do not mix. In the very words of my subject, there is an apparent contradiction. In the past, publicity has been abhorrent to the engineer. It seems to be true that the engineer, because of his training or his background, has developed a state of mind which omits publicity. At any rate he has done a poor publicity job for himself. The average engineer is self-conscious; he ought to be class-conscious. If T should ask the men in this hall to get up one by one and tell who they are and what they have done, there would be an instinctive reaction in the mind of each man-a feeling that this was out of place. If I should ask each man to get up and tell something about his neighbor, I should find that each neighbor, once he got acquainted with the man next to him and understood what he was doing, would be as human and as generous-hearted in telling about his brother engineer as is any professional man.

Jan 1, 1920

By I. A. Ettlinger

DEPRECIATION allowances have become firmly rooted in our income tax structure both by legislation and by court decisions. Secretary of the Treasury Morgenthau has recently stated before the Ways and Means Committee of the House: A taxpayer who did not provide for depreciation of assets used in his business could not long remain in business and the income tax should be levied on the assumption that he will provide for such depreciation. The 1934 Revenue Act has now been enacted, the depreciation provisions of the 1932 Revenue Act having been carried forward without change. However, there has arisen, in connection with the preparation of this new Revenue Act, a determination by the Treasury Department to make certain changes in the future administration of the depreciation allowances that will affect all corporations, and mining companies in particular.

Jan 1, 1934

By W. C. Williamson, J. L. Shugert

DUST control is receiving considerable attention today by most companies as is evidenced by the many articles, papers, and books written on the subject. ~~~t of the larger mining companies have given this subject close study and have established standardized methods of control. W. C. WILLIAMSON and J. L. SHUGERT, Members AIME, are Assistant Ventilation Engineers, Anaconda Copper Mining Co., Butte, Mont. San Francisco Meeting, February 1949. TP 2705 A. Discussion of this paper (2 copies) may be sent to Transactions AIME before Feb. 28, 1950. Manuscript received Jan. 17, 1949. Permissible Limits: The question of permissible dust limits has been considered by medical commit-ties and various national conferences. Dr. Lanza, of the Metropolitan Life Insurance Company, Dr. Le-roy U. Gardner, of the Saranac Laboratory for the study of Tuberculosis, and Dr. Pancoast, of the University of Pennsylvania, have been members of these committees. A statement included in reports of some of these committees is as follows: Concentrations to which the dust must be induced in order to be safe have not been absolutely determined. There is evidence that a concentration of more than five million particles per cubic foot of a highly siliceous dust is dangerous. Therefore, it may be stated that it is desirable to avoid counts of more than five million particles of dust containing free silica to a high percent in working places. Table I gives the safe limits adopted by several state industrial codes. Table I. Safe Limits of Dust Concentration Limit Million Particles State Per Cu Ft Cal~fornia Silica (less rhdn 10 pct) 50 Silica (10 pct to 50 pcr) 10 Sllica (more than 50 pct) 5 New York Frcc silica less than 10 pet by weight of rock formation 100 Frec silica more than 10 Pct by weight of rock formation 10 Oregon Silica (over 40 pct) 5 Silica (20 to 40 pct) 10 Silica (10 to 20 pet) 20 Wisconsin 15 million particles, under 10 nicrons in longest dimension per cu ft of air, when the quartz content of the dust is 35 pct, variations in free silica content will make proportional inverse changer in this standard Close attention to dust concentrations has been given to mining operations, since these operations are frequently carried on at considerable distances

Jan 1, 1951

By J. L. Shugert, W. C. Williamson

DUST control is receiving considerable attention today by most companies as is evidenced by the many articles, papers, and books written on the subject. ~~~t of the larger mining companies have given this subject close study and have established standardized methods of control. W. C. WILLIAMSON and J. L. SHUGERT, Members AIME, are Assistant Ventilation Engineers, Anaconda Copper Mining Co., Butte, Mont. San Francisco Meeting, February 1949. TP 2705 A. Discussion of this paper (2 copies) may be sent to Transactions AIME before Feb. 28, 1950. Manuscript received Jan. 17, 1949. Permissible Limits: The question of permissible dust limits has been considered by medical commit-ties and various national conferences. Dr. Lanza, of the Metropolitan Life Insurance Company, Dr. Le-roy U. Gardner, of the Saranac Laboratory for the study of Tuberculosis, and Dr. Pancoast, of the University of Pennsylvania, have been members of these committees. A statement included in reports of some of these committees is as follows: Concentrations to which the dust must be induced in order to be safe have not been absolutely determined. There is evidence that a concentration of more than five million particles per cubic foot of a highly siliceous dust is dangerous. Therefore, it may be stated that it is desirable to avoid counts of more than five million particles of dust containing free silica to a high percent in working places. Table I gives the safe limits adopted by several state industrial codes. Table I. Safe Limits of Dust Concentration Limit Million Particles State Per Cu Ft Cal~fornia Silica (less rhdn 10 pct) 50 Silica (10 pct to 50 pcr) 10 Sllica (more than 50 pct) 5 New York Frcc silica less than 10 pet by weight of rock formation 100 Frec silica more than 10 Pct by weight of rock formation 10 Oregon Silica (over 40 pct) 5 Silica (20 to 40 pct) 10 Silica (10 to 20 pet) 20 Wisconsin 15 million particles, under 10 nicrons in longest dimension per cu ft of air, when the quartz content of the dust is 35 pct, variations in free silica content will make proportional inverse changer in this standard Close attention to dust concentrations has been given to mining operations, since these operations are frequently carried on at considerable distances

Jan 1, 1951

By RICHARD L. HUMPHREY

IT IS proper that there should be a brief accounting of the stewardship which was entrusted to the Joint Conference Committee by resolution adopted by the. Organizing Conference on June 4, 1920, in part as follows: RESOLVED, that it is the sense of this Organizing Conference that the Joint Conference Committee should be entrusted with making provision for putting the conclusions of this Conference of engineers into effect, etc. Pursuant to this authority, the Joint Conference, Committee has acted as an Ad-interim Committee has- prepared, a synopsis of the proceedings of the Organizing .Conference, has edited and published the Constitution and By-Laws adopted by this Conference, and. has issued an invitation to become Charter Members of The Federated, American Engineering Societies; to the list of organizations to whom invitations had been extended to attend 'the Organizing., Conference. The Committee in connection with this invitation offered to the extent of its ability, such assistance as might be-desired; and arranged in many cases for one or more of its members to be present when the matter of membership in The Federated American Engineering Societies was considered. . .

Jan 1, 1920

By AIME AIME

FEW indeed are the sections of the country where trained or partly trained workers have not already been hired by a war industry plant or will be within the near future. Yet right in the midst of the heavily industrialized East lies the anthracite area, home of a million people, whose productive power has persistently been by-passed either by private industry or by the Government Plant Site Board. The chief reason given for not locating war plants in the area is that it is not within the strategic zone, but in numerous instances elsewhere this rule has been waived. Furthermore, the anthracite region is well protected on all sides by mountains and is at all points more than 100 miles inland. Continued depression in the anthracite industry and a crippling blow dealt by the war emergency to the production of silk and rayon goods, the chief manufacturing activity of the area, have resulted in a heavy migration, particularly of trained young workers, into near-by industrial areas. At least 50,000 people are currently unemployed, with the likelihood of an increase in coming months, and as many families are on relief.

Jan 1, 1942

By AIME AIME

NOTWITHSTANDING the metropolitan appearance of M. L. Haider, the present Chairman of the Petroleum Division, he is not a native New Yorker, but was born at Mandan, N. Dak., Oct. 1, 1904. He began his travels at an early stage in life and after attending the University of Southern California for two years he spent two additional years at Stanford University and was graduated in 1927. After a few months as an analytical chemist for the Portland Cement Co. he became research engineer in the natural gasoline department of the Richfield Oil Co. where he remained for approximately two years before taking a position with the Carter Oil Co. in Oklahoma. He was chief engineer for this company for three years before being trans-

Jan 1, 1945

By Roger B. Alke

INTRODUCTION Request to Mine Beneath Bridge The Jakes Run Bridge is a reinforced Portland concrete arch filled bridge located on WV Route 7 near Pentress, WV. The bridge has a span of 22.9 m (meters) and a height of 4 m above normal pool elevation to the underside of the center of the arch (See Fig 1). The bridge is a two lane structure with a width of 6.86 m. The structure is over 50 years old having been built in 1929 and is owned by the Department (WV Department of Highways). [ ]

Jan 1, 1984

By William Kent

I DESIRE to place on record in our Transactions a recent innovation in blast-furnace practice, namely, the introduction at the Lucy Furnaces, in Pittsburgh, of four water-tube steam-boilers, of the Babcock and Wilcox pattern, aggregating 832 horse-power, builder's rating, or 9,568 square feet of heating-surface, utilizing the waste gases of the furnaces as fuel. The boilers are set in two batteries, each of 416 horse-power, and each battery occupying a ground-space of 22 feet 7 inches by 20 feet 4 inches. The accompanying dram-

Jan 1, 1885

By J. C. Bokros

At temperatures above 950°F, zirconium which has been strained a critical amount will experience critical recrystalli-zation. The large grain size thus formed can result in a reduction in the fatigue life by a factor of 2 to a factor of 9 at both high and low temperatures. The critical strains for zirconium vary from 15 pct at 900°F to about 2 pct at 1125°F, while those for zircaloy III vary from 15 pct at 1050°F to 5 pct at 1200°F. Zircaloy II ,experiences no critical recrystallization up to 1200°F. ZIRCONIUM has become increasingly important for nuclear applications and is being employed in reactors at temperatures where recrystallization can occur. Recent work' on the fatigue properties of zirconium has shown that coarse-grained structures developed in zirconium during recrystallization have much lower fatigue lives than fine-grained material. The development of these large grain sizes under such conditions is well known to be the result of critical recrystallization.2-4 Briefly, critical recrystallization occurs when a metal is strained a critical amount and annealed in the recrystallization range. The critical strain is defined as that minimum strain necessary to promote nucleation in the time unit and temperature considered. The maximum grain size occurs at the critical strain, since at this strain the fewest stable nuclei per unit volume grow into new grains. Recrystallization is not evident below this; strain since the nucleation rate is vanishingly lolw, and metal strained more than the critical amount has a higher nucleation rate per unit volume which results in a finer grained structure. This paper describes the critical recrystallization observed in reactor-grade zirconium, zircaloy 11, and zircaloy I11 as a function of annealing temperature and temperature of strain. EXPERIMENTAL The zirconium used was hafnium-free, double arc-melted sponge obtained from the Bureau of Mines. The ingots were forged and hot reduced to 0.08 to 0.10-in. sheet and subsequently cold reduced to 0.035-in. sheet with intermediate and final anneals at 1200 OF for 15 min. The zircaloy II and zircaloy III used were 0.035-in. sheets in the annealed condition. Compositions of these materials as tested are given in Table I. To determine the critical strain at a given temperature, tensile specimens having a0.065-in. taper in a 2-in. gage length were machined from the sheets parallel to the rolling direction. The specimens were polished, etched, and examined metallographically to ensure that all of them were strain-free, initially. Tukon indentations were made every half millimeter along the gage length of each specimen. These served as fiducial marks enabling the plastic strain to be measured with a microscope and micrometer stage. The specimens were pulled to failure at a rate of 0.002 in. per min in an Instron tensile-testing machine. Three temperatures were used for straining: room temperature, 500 ºF, and 900 ºF. The 500º and 900 ºF tests were run in an argon atmosphere. Since the rate of work hardening changes with temperature, a different critical strain was obtained for each temperature of strain. Specimens, prepared in the manner described, were annealed in vacuunl at various temperatures ranging from 900" to 1200 F for up to 1000 hr, after which they were examined metallographically. The critical strain and the recrystallized grain size as a function of strain were determined for each specimen. Results for the same temperature and time indicated that the critical strain measured was reproducible to within 5 pct of each other. RESULTS AND DISCUSSION Since increasing the time of anneal increases the probability of the nucleation of a new grain, the critical strain decreases with time at a decreasing

Jan 1, 1961

By W. Edeburn, H. R. Fife

An extended study of dustproofing Freeport-seam coal has emphasized several fundamental features in the successful treating of bituminous coals. The extent of the exposed surface area and its absorption propcrties for the dust-retaining film were found to be the most critical factors affecting the efficiency of fly-dust prevention. From recently published screen data and specific surface-area measurements on United Kingdom coals, an approximation of the surface exposed by mine-run coal and by 1-in. slack was made. The total surface area exposed by an average tori of this mine-run coal was estimated at 3768 sq. yd., while a ton of 1-in. slack represents a total surface area of 8779 sq. yd. with no additions for porosity. It is important in coal treating to consider that in mine-run coal the fraction above 1/4 in. in size represents 79.5 per cent of the total weight, but only 4 per cent of the total surface, while the fraction below 150 mesh contains 47 per cent of the total surface and only 1.2 per cent of the total weight. Also, one should appreciate that, in a 1-in. slack, the domestic stoker fraction (1 in. to 8 mesh) contains 76.3 per cent of the weight and 8.2 per cent of the surface, while the fraction below 150 mesh represents 3.3 per cent by weight and 54.8 per cent by surface area. Wax extraction data on 1-in. to 0 slack from mine-run treated Freeport-searn coal showed that the coating was distributed uniformly as a function of exposed surface; hence, nonuniformly on a weight basis. This distribution of the coating on mine-run coal therefore limits the extent of treating that is desirable on bituminous coal at this point in the preparation. The treatment of Freeport mine-run coal before it reached the tipple gave a 70 to 80 per cent reduction of fly-dust in the tipple, a satisfactory treated commercial slack coal, and an indicated change in the trend of tipple degradation. The premium-treated domestic sizes required a supplemental treatment for complete dustproofness. The actual cost of the pretipple and supplemental treatments was very low per ton of coal treated, while the net or true cost was sufficiently

Jan 1, 1938

By W. Edeburn, H. R. Fife

An extended study of dustproofing Freeport-seam coal has emphasized several fundamental features in the successful treating of bituminous coals. The extent of the exposed surface area and its absorption propcrties for the dust-retaining film were found to be the most critical factors affecting the efficiency of fly-dust prevention. From recently published screen data and specific surface-area measurements on United Kingdom coals, an approximation of the surface exposed by mine-run coal and by 1-in. slack was made. The total surface area exposed by an average tori of this mine-run coal was estimated at 3768 sq. yd., while a ton of 1-in. slack represents a total surface area of 8779 sq. yd. with no additions for porosity. It is important in coal treating to consider that in mine-run coal the fraction above 1/4 in. in size represents 79.5 per cent of the total weight, but only 4 per cent of the total surface, while the fraction below 150 mesh contains 47 per cent of the total surface and only 1.2 per cent of the total weight. Also, one should appreciate that, in a 1-in. slack, the domestic stoker fraction (1 in. to 8 mesh) contains 76.3 per cent of the weight and 8.2 per cent of the surface, while the fraction below 150 mesh represents 3.3 per cent by weight and 54.8 per cent by surface area. Wax extraction data on 1-in. to 0 slack from mine-run treated Freeport-searn coal showed that the coating was distributed uniformly as a function of exposed surface; hence, nonuniformly on a weight basis. This distribution of the coating on mine-run coal therefore limits the extent of treating that is desirable on bituminous coal at this point in the preparation. The treatment of Freeport mine-run coal before it reached the tipple gave a 70 to 80 per cent reduction of fly-dust in the tipple, a satisfactory treated commercial slack coal, and an indicated change in the trend of tipple degradation. The premium-treated domestic sizes required a supplemental treatment for complete dustproofness. The actual cost of the pretipple and supplemental treatments was very low per ton of coal treated, while the net or true cost was sufficiently

Jan 1, 1938

By R. I. Jaffee, C. M. Craighead, G. A. Lenning

The effects of increasing hydrogen content, introducing a notch, and changing the strain rate on properties of titanium and one of its alloys were investigated over a range of testing temperatures from —196° to 200°C. Both high purity and commercial purity A-55 titanium were used as representative a materials, while a commercial Ti-8 pct Mn alloy was used for an a-P alloy. It was found possible to analyze the data, using the ductile-to-brittle transition temperature concept. Increasing hydrogen, the presence of a notch, and increasing the testing speed raised the transition temperature for the a materials. The presence of hydrogen and notches raised the transition temperature of the a-B alloy also. However, increasing the testing speed generally decreased the transition temperature of the a-p alloy. IN previous papers, the authors have shown that hydrogen is most detrimental to the notch-bend impact toughness of a-titanium' and to the tensile ductility of a-B titanium alloys.' These general effects have been confirmed by Kessler and co-workers," and by Kotfila and Erbin." Kessler showed that the slower strain rate in notch-rupture tests was a more sensitive measure of hydrogen embrittle-ment of a-B alloys than the tensile test. In the present paper the authors cover, with tensile and notch-bend tests, the effect of testing speed, notches, and testing temperature on hydrogen em-brittlement. High purity and commercial purity titanium, examples of u materials, and a commercial a-,f3 Ti-8 pct Mn alloy were investigated. The purpose of the investigation was to correlate the factors producing embrittlement. Materials The high purity titanium for this investigation was obtained by arc-melting crystal bar from Foote Mineral Co. into 1 Ib ingots. As-cast hardnesses for these ingots ranged from 60 to 90 Brinell. The arc-melted ingots were forged to % in. diam rods at 1470°F. These rods were swaged to & in. diam at room temperature prior to machining of the specimens for hydrogenation and testing. The commercial A-55 titanium and the Ti-8 pct Mn alloy were obtained from Rem-Cru Titanium Inc., as % in. diam rod. The A-55 titanium was hot swaged to 1/4 in. diam at 1300°F prior to machining of the specimens for hydrogenation and testing. The a-p C-11OM alloy was hydrogenated prior to hot swaging to 1/4 in. roc1 at 1300°F. Hydrogenation prior to fabrication permitted testing of the a-P alloy in the equilibrated and stabilized condition. The equilibration and stabilization treatment used was an air anneal for 1 hr at 1300°F, followed by furnace cooling to 1100°F and then air cooling. Hydrogenation was done in a Sieverts apparatus described previously.' The hydrogenation treatment consisted of heating for 1/4 to 1/2 hr at 820 °C in purified hydrogen, slow cooling to 680"C, holding 1 hr for homogenization, and rapid cooling to room temperature. Intended hydrogen levels for the a-tita-nium materials were 0.05, 0.5, 1.0, 1.5, and 2.0 atomic pct—about 15 to 430 ppm. For the Ti-8 pct Mn alloy, the intended hydrogen levels were 0.05, 0.5, 1.0, 2.5, and 5.0 atomic pct—about 15 to 1100 ppm. The material for the 0.5 atomic pct level of hydrogen was vacuum annealed prior to hydrogenation to increase the accuracy of the addition. Vacuum annealing to remove hydrogen consisted of heating for 6 hr at 820°C, and resulted in a hydrogen content of about 10 to 15 ppm. When hydrogen contents were above 0.5 atomic pct—100 ppm—the hydrogen was added without prior vacuum annealing.

Jan 1, 1957

By Robert Laurich

Chuquicamata pit was opened in 1915 with steam shovels and steam locomotives brought down from the Panama Canal excavation project. With expansions in the early years, more steam locomo¬tives were brought into the mine. IMPROVED LOCOMOTIVES During the period 1927 to 1937, electric locomo¬tives were purchased and main line and bench tracks were electrified. Third rail was installed up to the working areas. At first, the locomotives were equipped with batteries for service at the shovels, but charge life was too short and they were con¬verted to use the third rail and a reel with 3000 ft of trailing cable for service in the loading area.

Jan 11, 1959

By P. W. Gilles, B. D. Pollock

THE pioneering work of Steinitz1 and Steinitz, Binder, and Moskowitz2 has shown conclusively the existence at high temperature of two additional phases in the molybdenum-boron system and thus brings to a total of six the number of structures appearing in this system. To the structures Mo2B, MOB, and Mo2B5 they have added MO3B2, a new -MOB form, and have shown that MOB,, which has the same range of composition as Mo2B5, is only a high temperature structure of the latter. This solid solution, interestingly enough, includes neither of the compositions corresponding to the stoichiomet-ric compounds, MOB, or Mo2B5, but rather at all temperatures has intermediate values of composition. These workers have also, in the course of their work, measured melting points, transition temperatures, eutectic and peritectic points in the system and have shown that Mo3B2, because of its dispro-portionation at low temperature to Mo2B and MOB, is stable only in a limited high temperature range. During the course of the present work on the vaporization properties of the molybdenum-boron compounds, a few transition temperatures were observed. When the report of the other workers appeared, it was decided to repeat, in part, their study of the system. As a result, considerable evidence has been obtained that substantiates the specific kinds of melting processes they report as well as the general features of their diagram. However, a marked difference was found between the temperatures they report and the ones observed in this study, with the latter being higher. The purposes of this paper are to present the evidence obtained in this laboratory that verifies their diagram of the system, to give some important temperatures in the system, to compare them with those previously published, and to seek an explanation of the difference. Samples The metal starting material was 400 mesh molybdenum powder with a purity stated by the manufacturer to be 99.9 pct. The initial treatment, designed to remove volatile contamination, consisted of heating in a vacuum for 10 min to a temperature of from 800" to 1000°C during which a loss of 0.3 to 0.4 pct occurred. An assay following this treatment showed it to be 99.4 pct pure, with the principal impurity probably being oxygen. The boron starting material was obtained from the Cooper Metallurgical Laboratories and the Fair-mount Chemical Co. as 325 mesh powder with manufacturers' analyses of 99 pct or better. Initial treatment consisted of heating in molybdenum in a vacuum at about 1700°C for 10 min. During this time a loss of 3.5 pct occurred. An assay following this treatment showed the different samples to have purities ranging from 95.5 to 99.0 pct with iron and carbon as the principal impurities. Following the initial treatment, the elements were combined to form stocks of Mo2B and MOB by heating pressed mixtures in a vacuum to 1100" to 1200°C to accomplish reaction and to 1500" to 1900°C for a few minutes to evaporate the more volatile impurities. Analysis of the two compounds for boron by a modification of the method of Blumenthal3 and for molybdenum by the lead-molybdate method indicated them to have purities greater than 99 pct. The individual samples to be studied had compositions in the Mo2B-MOB range and consisted of mixtures of the stock compounds. Procedure As is usually the case in high temperature work the selection of containers for the samples posed some problems. For vapor pressure studies tantalum crucibles, allowing little contact with the pressed samples, were used and some of the observations made during these experiments are pertinent to the study of the phase diagram. Most of the experiments, however, were performed in graphite containers, as were those of the previous authors. Two kinds of spectroscopic grade graphite crucibles were used. One was a % in. cylinder, 3/4 in. high, containing seven 3/16 in. holes drilled 1/2 in. deep into which were packed samples of the different mixtures weighing 250 to 500 milligrams. The other, consisting of separate crucibles, was prepared by drilling 3/16 in. holes, 1/2 in. deep into 1/4 in. graphite rods % in. long. The 7/8 in. cylinder was heated directly by induction while the small crucibles were packed in a tantalum heating element for induction heating. All heating was done in a high vacuum system in which the pressure was generally less than 1x10-5mm and never rose above 2x10-5mm when the samples were hot. The general pattern of the heating in graphite was to heat rapidly to a temperature somewhat below the desired one, then to raise the temperature slowly. The samples were held for 2 to 5 min at the maximum temperature, which in all cases was far higher than that needed to produce reaction. The short time was employed to reduce possible contamination by the crucible material and to reduce composition changes that would occur because of vaporization. After examination following the heating, the samples were reheated to a higher temperature. Temperatures were measured with a Leeds and Northrup disappearing filament optical pyrometer, certified by the National Bureau of Standards, by sighting through a window at the top of the vacuum

Jan 1, 1954

By Frederick N. Rhines, William A. Anderson

The investigations of Wymanl have demonstrated that copper deoxidized with several of the commonly used agents that confer immunily to ordinary hydrogen em-brittlement can still be embrittled if it is annealed alternately under oxidizing and reducing conditions. During the oxidizing cycle, oxygen diffuses into the copper and frequently deposits a subscale composed of the oxide of the residual deoxidizing agent. Upon subsequent reduction with hot hydrogen, the copper becomes ruptured along the grain boundaries to a depth sharply limited by the previous penetration of oxygen as delineated by the inner boundary of the subscale. Obviously the sensitivity to this kind of hydrogen embrittlement is engendered by the introduction of oxygen during the oxidizing anneal, but beyond this the mechanism of the process, and hence the controlling factors, remain obscure. There are several possibilities: (I) oxygen dissolved in the copper matrix of the subscale may, upon cooling prior to the hydrogen anneal, precipitate as cuprous oxide which is subsequently reduced by hydrogen as in the familiar case of hydrogen embrittlement; (2) oxygen in solid solution in copper may itself confer susceptibility to embrittlement by hydrogen; (3) the normally refractory oxides such as those of aluminum, silicon and titanium may themselves be reduced by hydrogen when in contact with copper; or (4) the precipitated oxides of the subscale may be complex compounds such, perhaps, as SiO2.Cu2O, which are partially reduced by hydrogen. These possibilities have been examined, and it has been concluded that the first three and possibly the fourth are operative collectively or individually under more or less predictable conditions. Effect OF Precipitated Cuprous Oxide and Dissolved Oxygen The literature provides no definite proof that oxygen in solid solution in copper can confer susceptibility to hydrogen embrittlement; indeed, the research of Leiter2 seemed to indicate the opposite—that to produce the effect, cuprous oxide must be present in massive form and in a more or less continuous network along the grain boundaries. To test this point, pure copper has been annealed in hydrogen under conditions designed to ensure the presence in various samples of: (I) precipitated cuprous oxide, (2) dissolved oxygen only, and (3) no oxygen in any form. Very pure copper" said to contain no oxygen and no spectro-scopically detectable traces of any other element (that is, no individual detectable impurity in quantity greater than 0.0001 per cent) was used. Strips of this material cold.-rolled 75 per cent to 1/8 in. in thickness were subjected to the following treatments, the results of which are noted:

Jan 1, 1941

By Frederick N. Rhines, William A. Anderson

The investigations of Wymanl have demonstrated that copper deoxidized with several of the commonly used agents that confer immunily to ordinary hydrogen em-brittlement can still be embrittled if it is annealed alternately under oxidizing and reducing conditions. During the oxidizing cycle, oxygen diffuses into the copper and frequently deposits a subscale composed of the oxide of the residual deoxidizing agent. Upon subsequent reduction with hot hydrogen, the copper becomes ruptured along the grain boundaries to a depth sharply limited by the previous penetration of oxygen as delineated by the inner boundary of the subscale. Obviously the sensitivity to this kind of hydrogen embrittlement is engendered by the introduction of oxygen during the oxidizing anneal, but beyond this the mechanism of the process, and hence the controlling factors, remain obscure. There are several possibilities: (I) oxygen dissolved in the copper matrix of the subscale may, upon cooling prior to the hydrogen anneal, precipitate as cuprous oxide which is subsequently reduced by hydrogen as in the familiar case of hydrogen embrittlement; (2) oxygen in solid solution in copper may itself confer susceptibility to embrittlement by hydrogen; (3) the normally refractory oxides such as those of aluminum, silicon and titanium may themselves be reduced by hydrogen when in contact with copper; or (4) the precipitated oxides of the subscale may be complex compounds such, perhaps, as SiO2.Cu2O, which are partially reduced by hydrogen. These possibilities have been examined, and it has been concluded that the first three and possibly the fourth are operative collectively or individually under more or less predictable conditions. Effect OF Precipitated Cuprous Oxide and Dissolved Oxygen The literature provides no definite proof that oxygen in solid solution in copper can confer susceptibility to hydrogen embrittlement; indeed, the research of Leiter2 seemed to indicate the opposite—that to produce the effect, cuprous oxide must be present in massive form and in a more or less continuous network along the grain boundaries. To test this point, pure copper has been annealed in hydrogen under conditions designed to ensure the presence in various samples of: (I) precipitated cuprous oxide, (2) dissolved oxygen only, and (3) no oxygen in any form. Very pure copper" said to contain no oxygen and no spectro-scopically detectable traces of any other element (that is, no individual detectable impurity in quantity greater than 0.0001 per cent) was used. Strips of this material cold.-rolled 75 per cent to 1/8 in. in thickness were subjected to the following treatments, the results of which are noted:

Jan 1, 1941

By Robert K. Warner

Is an accurate measurement of the efficiency of a screen under a given set of operating conditions valuable? If so, what is the efficiency of a screen and how can it be measured? Sizing, especially of the finer sizes of material, has increased in importance in the development of flow sheets as a result of the perfecting of the rapid vibrating screens. More consideration should be given screens in the preparation of ball-mill feed, where they permit the admission of a dryer feed than the classifier. Where possible, the introduction of a screen ahead of the primary ball-mill, and the diverting of ore below, say, 4 mm. to a secondary mill, might result in a greater overall economy because of the thicker feed and the better adjustment of crushing media and mill operation to the reduction demanded. With the present trend back toward a combination of gravity methods and flotation, rather than flotation alone, the accurate, economical sizing possible with the new screens makes fine jigging a method to be considered. W. o. Borcherdtl and John Bland= discuss the screening problem and also the value of close sizing in the concentration of some of the rare-metal ores. If a screen is to be used, it should be selected in competition with others; other things being equal, that screen which makes the cleanest oversize should be preferred. The quality of the screening and the tons handled per dollar together determine the choice and, therefore, both of these must be accurately measured if a correct decision is to be reached. Too frequently in mill design, the capacity has been considered almost to the exclusion of the completeness with which the undersize is separated from the oversize. It is, of course, possible to increase the aperture of the screen, and thus insure the removal of a sufficiently coarse

Jan 1, 1924