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By L. Leibowitz, M. G. Chasanov, L. W. Mishler

A drop calorimeter system is described for use in measuring enthalpies to 3600°K. Data are presented for tungsten between 2800" and 3600°K. The enthalpy of tungsten in cal per mole between 2000° and 3600°K can be represented by the equation HºT- Hº298 = - 1.7622 X 103 + 5.7772T + 8.9861 where T is in degrees Kelvin. A tabulation of com -puted values is presented for heat capacity, entropy, and free energy function. A drop calorimeter has been constructed to carry out enthalpy measurements at temperatures to 3600°K. Samples are heated by induction1 and dropped into a commercial adiabatic calorimeter, modified for this purpose. The experimental temperature is limited by the melting point of container materials and compatibility of the container and its contents. Several high-temperature drop calorimeters have been described in the literature1-5 but none has been used at temperatures as high as those in the present work; our measurements of the enthalpy of tungsten range from 2800" to 3600°K. DESCRIPTION OF EQUIPMENT An overall schematic view of the equipment is shown in Fig. 1. Power for the induction coil is supplied by a 25-kw 250 kHz Ther-Monic generator coupled to an iron core RF transformer. The Sample capsule is suspended in the work coil by 10-mil diam tungsten wires which are wrapped around a horizontal 5-mil diam tungsten wire. The horizontal suspension wire is clamped between two massive copper electrodes which are fixed in an x-y motion device that allows adjustment of the position of the heated capsule from outside the vacuum chamber. The copper electrodes are connected by flexible copper straps to a 1250-joule (5 kv, 100 pfarad) condenser bank. When it is desired to release the capsule, the condensers are discharged through the horizontal suspension wire causing it to vaporize rapidly. Very reliable and precise release of the capsule is achieved in this manner. Experiments have shown that no heat correction is required for this discharge energy. As part of the temperature measuring system, two prism holders have been incorporated in the apparatus. The upper prism holder is in the main vacuum chamber itself, whereas the lower one is in a side arm attached to the drop tube below the gate valve. The upper prism is mounted on a rotary vacuum feed-through, and may be moved under a protective shield when not in use. This prevents deposition of vapors on the prism surfaces when temperature measurements are not being made. Similarly, the lower prism is mounted on a push-pull vacuum feed-through, and when not in use may be pulled into its side tube. The prism mountings are fitted with guides and stops so that they may be moved precisely into the desired position. The aim throughout is to minimize the time the prisms are exposed to vapors from the hot samples. At the high temperatures reported in this paper, only the lower prism was used. The upper prism holder in these cases was fitted with an additional radiation shield. By using a prism and viewport, the lower surface of the samples can be observed by an optical pyrometer. The measurements discussed in this paper were obtained with a Leeds and Northrup 8622-C-S series manual pyrometer which is estimated to be accurate to 0.5 pct. Pyrometer calibrations and prism and window corrections were carried out in the conventional manner6 using tungsten strip lamps calibrated by the National Physical Laboratory, Teddington, England. Prism corrections were rechecked after each use. All work to date has been done in vacuum, and no measurable change has been observed in the prism correction below -2300°K for the upper prism and below -2800°K for the lower one. The total time of exposure of the prisms is about 50 sec per run. At high temperature, the final temperature reading is corrected by using the final A value for the prism; see Ref. 6 for details of this procedure. The calorimeter is a modified Parr Instrument Co. (Moline, lll.), Series 1230 adiabatic calorimeter with automatic jacket control. Other authors5 have used a similar calorimeter with good results. The calorimeter jacket cover and calorimeter cover are attached to the drop tube which contains a radiation shield. This shield is a gold-plated copper disc which can be operated manually from outside the calorimeter. The receiver is attached below the radiation shield and is lined with tungsten. In a typical experiment, the calorimeter and its jacket water temperatures were adjusted to 0.000°K temperature difference. The sample was allowed to equilibrate in the furnace at the desired temperature for about 20 min. The initial calorimeter temperature was then recorded, the sample dropped, and appropriate shutters closed. After about 3 min, the drop tube and receiver were filled with helium to 60 torr. The final calorimeter temperature was recorded after it had remained constant over a 5-min period. The equilibration time in the calorimeter was about 25 min. Thermistor probes are used to operate a hot and cold water supply system to maintain the jacket temperature equal to the calorimeter temperature. For actual measurements of the calorimeter temperatures, a quartz thermometer was used (Hewlett Packard Dymec Thermometer, Model #2801A). This thermome-

Jan 1, 1970

By M. S. Seltzer

In a previous paper1 it was shown that activation energies for steady-state creep in lead sulfide single crystals varied with the concentration of electronic defects. For n-type lead-excess crystals, values for the creep activation energy, Qc, decreased from 2.9 to 2.2 ev as the carrier concentration increased from 1017 to 1017 electrons per cu cm, while Q, increased from 1.6 to 2.3 ev for p-type sulfur-excess crystals as the concentration of holes increased from 6 X 1017 to 1018 per cu cm. It was also shown in Ref. 1 that the Q, values could best be correlated with the sum of the self-diffusion activation energies in PbS, i.e., for a given concentration of electrons or holes Q, = QPb + Qs, where Qpb and QS are the activation energies for diffusion of pb210 and s35 in PbS. This result suggests that creep rates are controlled by at least two atomic defects, one for lead migration and one controlling sulfur transport. It would be most desirable to interpret these creep energies in terms of an atomic defect disorder model for lead sulfide. Studies of creep rates as a function of sulfur pressure2 indicate that the defects controlling creep rates are singly ionized lead and sulfur vacancies, VPb and Vs. This hypothesis can be more firmly established by determination of Q, under conditions of constant atomic defect concentration rather than constant electronic defect concentration as has been previously done. Therefore, several measurements have been made of Q, on crystals whose con- centration of lead vacancies or sulfur vacancies has been fixed by equilibration under appropriate sulfur pressure and temperature. It was indicated in Ref. 2 that high-temperature isotherms are available which show how the concentrations of various atomic point defects in PbS vary with composition over the entire homogeneity range for the compound. Two such isotherms are shown in Fig. 1 for 900" and 1000°K. Utilizing these isotherms the concentration of a given defect, say Vbb, may be held constant over a particular temperature range by adjusting the sulfur pressure as the temperature is changed. Thus the concentration of one defect suspected of controlling creep rates may be held constant while other defect concentrations vary. The apparent activation energy for formation of these defects can be obtained from the isotherms giving their concentration as a function of sulfur pressure. Activation energies for creep obtained under conditions of constant defect concentration can then be compared with defect formation energies and certain possible atomic defects can be eliminated as creep-controlling species. We have performed creep experiments as a function of temperature at a stress of 244 g per sq mm under conditions which fixed the lead vacancy concentration, V', at 1016, 3.2 x 1016, and 3.2 x 1017 cm-3, and one were the sulfur vacancy concentration, Vs, was held at lo17 cm-3. The results are presented in Fig. 2 as creep rate, k, vs reciprocal of absolute temperature, 1/T. Specimens 34, 35, and 36 were deformed under constant lead vacancy concentration while specimen

Jan 1, 1969

By L. A. Bromley, A. W. Petersen

The van Arkel-deBoer method for producing ductile titanium by thermal decomposition of Til, vapor and deposition on an electrically heated filament is modified by film boiling Til liquid on a heated filament, resulting in similar titanium deposition on the filament and liberation of gaseous iodine. The deposition rate is higher and the energy requirement smaller than in the van Arkel process. Many problems must be solved before the process is commercially feasible. TITANIUM of 99.9 pct purity, called ductile titanium, has been produced by a modification of the van Arkel-deBoer&apos; method. In the van Arkel-deBoer method, an electrically heated wire is suspended from two electrodes, which are placed in a container holding TiI, vapor at a low&apos; vapor pressure (usually <5 mm Hg). The vapor diffuses to the hot wire, usually maintained at 1100" to 1600°C,&apos; and decomposes according to the reaction liberating gaseous atomic iodine and depositing solid crystalline titanium on the wire. Estimations based on the data of Runnalls and Pidgeon,&apos; indicate that the rate-control ling step is the diffusion of atomic iodine away from the wire. There appears to be nearly thermodynamic equilibrium at the wire with TiI, and iodine as the main gaseous species. TiI, is almost certainly an important gaseous species in the cooler regions.&apos; The liberated iodine diffuses to a heated source of crude titanium and reacts to form more TiI, vapor, which again diffuses to the hot wire and completes the cyclic process. The foregoing process may be modified by suspending the hot wire in liquid TiI,, instead of the vapor, and obtaining film boiling. This type of boiling is characterized by the formation of a continuous film of vapor over the wire surface. Since only vapor contacts the wire sul.face, the temperature of this surface may be raised as high as desirable, within the limit of mechanical strength requirements for the wire. By properly adjusting the input voltage. the temperature of the wire may be maintained above U0C"C; and by evacuating the vessel holding the liquid TiI, and maintaining a suitable condenser temperature, the vapor pressure of TiI, may be held low. Thus, the conditions of operation of the van Arkel-deBoer method may be approximated with film boiling; and hence, it is postulated that ductile titanium may be produced by this method. Preparation of Til, There are many methods available for the preparation of TiI,; that used in this research was prepared by the direct reaction of titanium sponge in controlled amounts with liquid iodine. Although no difficulty was encountered with this reaction, it has since been pointed out that this method is sometimes dangerous and should be used with caution. The resulting TiI, was purified by distillation. First Film Boiling Experiments Apparatus: The apparatus shown in Fig. 1 was used for film boiling TiI, on short wire filaments. The current to the filament was supplied through a bank of three 5 kva transformers connected in parallel. The current was controlled by adjusting the voltage over a 0 to 67.5 v range with a 7 kva variable transformer on the low voltage side of the bank of transformers. The current and voltage were measured by Weston meters. The sealed-in-glass tungsten electrodes were hard-soldered to the filament for the film boiling of TiI,. The bottom part of the reactor, containing TiI,, was wrapped with ni-chrome heating wires to maintain the TiI, in the liquid state. An ice or liquid nitrogen trap, for solidifying I, vapor and any TiI, not condensed, was attached to the low pressure side of the air-cooled condenser. A Megavac vacuum pump was used. Procedure: A 0.010 in. diam tungsten filament was hard-soldered to the tungsten electrodes. TiI, was melted (mp 156°C) and poured into the reactor chamber; the top of the reactor chamber, containing the electrodes, was replaced. Freezing of the TiI, was prevented by controlling the current to the ni-chrome wires wrapped around the reactor with a 1 kva variable transformer. The mechanical vacuum pump was started and the system evacuated to about 2 mm Hg TiI, vapor pressure. The current to the filament was turned on and the impressed voltage slowly increased with the variable transformer. A sudden drop in current at nearly constant im-

Jan 1, 1957

By J. E. Burke

RECENT investigations have elucidated many of the phenomena of the grain growth process, but have also revealed some conflicting and unexplained results. Beck and his co-workers1,2,3 have shown that grain growth continues with continued heating at one temperature until the average grain size approaches the thickness of the specimen, Plotting the logarithm of the average grain diameter, D, against the logarithm of the annealing time, t, they find the straight line relationship given by the equation: [D=Ktn [11] with possible small deviations at short annealing times. K and n are constants at constant temperature. On the other hand, Walker4 finds that, in alpha brass, the rate of growth falls off more rapidly than indicated by Eq I after long annealing, so that an equilibrium grain size is approached. Burke5 showed, using Walker&apos;s data, that time and temperature for grain growth are apparently related through an activation energy, H, according to the relationship: [t, Hr i &apos;_ III t„ = R \T, - ~) [2]] where t1 and t2 are the annealing times necessary for the average grain size to increase from Do to D at temperatures T1 and T2 and R is the gas laws constant. In the case quoted, H had the value 60,000 cal per mol. The apparent validity of this relationship, at least up to 700°C, and the approximate value of H were later confirmed by Beck.&apos; The results obtained by Beck, Kremer, Demer and Holzworth2 for aluminum and aluminum-magnesium alloys could not be satisfied by such a relationship, since the slope of the isothermal curves increased with increasing temperature. These data indicate and Beck, Holzworth and Hu6 later demonstrated experimentally that the only apparent factor controlling the rate of grain growth at constant temperature is the grain size. While many of the phenomena have been elucidated, a reasonably quantitative explanation of the process is lacking. There exists uncertainty even as to the primary driving force for grain growth, although there is a considerable body of indirect evidence that the interfacial energy of the grain boundary is responsible.7,8,10 Making implicit use of this assumption, several authors14,15 have pointed out that grain boundaries should migrate toward their center of curvature. Harker and Parker&apos; have advanced this concept furthest, and show that one can expect grain boundary migration to occur only when the grain faces are curved, or when they meet at non-equilibrium angles. When the face is curved toward a grain A, for example, the atoms in the surface of grain B, on the other side of the boundary, are on the average more surrounded by the atoms of their lattice than the atoms on the surface of grain A. Because of thermal motion, the atoms at the interface will sometimes be attached to grain A and

Jan 1, 1948

By E. A. Almond

An attempt is made to explain the effect of stress on strain aging by examining the mechanism of yielding for a group of aged dislocations. The experimental results on which the theory is based indicate that a linear relationship develops between the aging stress and the discontinuous yield effect in a low carbon steel THE discontinuous yield effect that occurs in bcc metals after strain aging is usually explained by the interaction of interstitial atoms with individual dislocations. Attempts have been made to interpret the kinetics of strain aging in terms of interstitial segregation to nonrandom groups of dislocations1-3 but apart from Li&apos;s4 work little or no effort has been made to examine the effect of groups of aged dislocations on mechanical properties. It appears likely that such groups can be stabilized if a positive load is maintained on the specimen during aging5 and, furthermore, that the enhanced strain aging effect associated with aging under load might be due to the stability of these aged groups. The effects associated with this latter phenomenon have been described by Almond and Hull, Ref. 5, Figs. 2 and 3, and it is found that the upper yield stress, the lower yield stress, and the yield point elongation are increased by aging under load. The yield point elongation reaches a maximum value but the enhanced effect persists in the upper and lower yield stress values even after extended aging treatments when the general level of the flow stress curve rises. The flow stress, as measured at 8.5 pct total strain, however, is independent of aging stress. Almond and Hull5 showed that it was unlikely that the differences in mechanical properties could be caused by stress enhanced diffusion and they suggested that the effect was in some way associated with the different dislocation distributions that are obtained when specimens are aged with and without an applied stress. At that time no explanation was offered for the strengthening effect produced by stabilized dislocation distributions but additional tests have been performed to establish a quantitative relationship between aging stress and mechanical properties, and also to examine more closely the effect of varying the procedure for applying the aging stress. EXPERIMENTAL The material used was an iron wire containing 0.015 wt pct C, 0.002 wt pct N, and 0.006 wt pct 0. Tensile specimens with a 1 cm gage length and 0.08 cm diam were annealed at 850°C for 1 hr in vacuum to establish a grain diameter of 0.032 mm and then aged at 200°C for 24 hr. After this treatment the amount of carbon left in solution would be less than 10-4 wt pct, and ni- as aging time is increased. It is suggested that this observation, and effects that arise from varying the method of applying the aging stress, can be explained by a strengthening mechanism whereby dislocations are more difficult to move when they are aged in piled-up groups. trogen would be the main cause of strain aging. Tensile tests were performed in a hard beam machine at a constant crosshead speed of 0.02 cm per min and the specimen chamber was immersed in a temperature controlled silicone oil bath at 32" * 0.05"C. RESULTS All specimens were prestrained 5 pct before aging under stress and the results in Figs. 1 to 5 show the effect of aging time and aging stress on the following parameters ?UY = auy — ?F(5); i.e., the difference between the upper yield stress after aging,?uy, and the flow stress after prestraining 5 pct, ?f(5). ?LY = sly —sf(5); the difference between the lower yield stress after aging, ojy, and the flow stress after prestraining 5 pct. s8.5 = the flow stress at 8.5 pct total strain after aging at 5 pct strain. Varying the Loading Procedure. Three variations in the procedure for applying the aging stress were examined; i) After prestraining, the specimen was unloaded to a stress of 18 kg mm-2, aged at that stress, and then tested. ii) After prestraining, the specimen was unloaded to 2 kg mm-" then reloaded to 18 kg mm-&apos;, aged at that stress, and tested. iii) After prestraining, the specimen was unloaded to 18 kg mm-&apos;, aged at that stress, then unloaded to 2 kg mm- before testing. Specimens were unloaded or reloaded by decoupling a clutch in the drive transmission of the tensile machine. This enabled the crosshead to be driven manu-

Jan 1, 1970

By John J. Croston

In the closing months of 1936 the copper industry gave every evidence that it was at last on the threshold of an improved era. At the beginning of the year prices stood at 91/4c, which in itself was a great improvement over prices prevailing for the three previous years. Industry generally was showing signs of moving forward in this country, and business was definitely good in certain foreign quarters. The threat of war and preparations for rearmament in Europe and Asia acted as a further stimulus to purchasing. By midsummer the situation had so improved and stocks had been so reduced that the cartel of foreign producers (including American producers with foreign mines) decided to increase the production quota to 75 per cent on Aug. 1. Large-scale buying gave continued strength to the price and by Oct. 1 the quota was increased to 80 per cent, and again on Oct. 15, to 85 per cent. Notwithstanding this the price of copper continued its advance and on Nov. 1, with stocks declining continuously, the cartel increased operations to 95 per cent, then to 105 per cent on Nov. 5. In the meantime the domestic producers, because of the great increase in home consumption, had increased their production by nearly one-half. At the close of the year copper sold at 126 per pound, and since the turn of the present year has reached 17c. This rapid increase has not been wholly justified. Much of the increase was due to the legitimate demands of recovering industry, but rearmament orders plus accumulation of reserve stocks in case of war, purchases in anticipation of labor strikes and purely speculative activities on the London Metal Exchange accounted for the balance. Certainly in view of the state of industry and the general world price level, it appears unnecessarily high. Talk of a copper shortage is sheer nonsense, the recent condition in the market being created by overbuying, leaving but a small volume for speculative supplies. It takes some months for an increase in mine output to reach the market, but production is again overtaking apparent consumption, stocks have begun to increase, and this, together with the reopening of many small

Jan 1, 1937

By H. L. Barr

THE following report covers the history of the development of the mine, present equipment, methods and costs of mining and milling. In addition, a description of the ore deposit is given with emphasis on the origin of the fractures, mode and types of ore occurrence, and mechanics of granite emplacement. An endeavor has been made to present a complete and accurate statement of the San Mauricio mine, the highest grade gold mine in the Philippine Islands. Credit is gratefully acknowledged to the mine staff for descriptions and details regarding their particular field of work. All analyses were made by Mr. T. A. DeVore, head chemist, San Mauricio Mining Co. Messrs. Edward Wisser, J. E. Fyfe, A. F. Skerl and W. B. Meek, geol-ogists, have contributed geologic information and ideas, for which thanks are extended. The Executive Committee of Marsman and Co., Inc., Managers of the Company, has kindly given permission for publication. Mr. J. B. Stapler, Division Manager, Marsman and Co., has had the courtesy to read the manuscript and to give critical and helpful suggestions.

Jan 1, 1940

By E. J. MCOAUSTLAND

THE behavior of steel after overstrain and at moderate temperatures is fairly well known. It has been made the subject of much investigation, and our knowledge is clear and definite on many points. The ultimate raising of the elastic limit, after moderate overstrain, and the consequent lowering of the ductility, seem to be well established. It is also well understood that the immediate effect of overstrain is to lower the elastic limit, possibly to zero, but that if not interfered with, this limit will subsequently rise higher than before. The "tests after moderate temperature," reported in this paper, were undertaken to verify the above statements for the particular steel under investigation, and also to determine, if possible, the total time required for complete recovery from this state of overstrain. The behavior of overstrained steel at temperatures at or below 32° F. is not so well known. Tests made by Prof E. G. Coker, at McGill University,&apos; show that steel, overstrained and subjected to cold, will remain in a state of overstrain for an indefinite period. I am not aware of any other published results of tests along this particular line. The effect of time and temperature on the recovery of steel from overstrain was made in 1902-3 the subject of sortie investigation in the laboratories of the College of Civil Engineering of Cornell University. A general plan was outlined in connection with the regular courses of instruction in testing of materials; but the press of routine work and the demands of the schedules on the time of the students were so great as to presage long delay in the completion of the work. Not much had been accomplished up to 1904-05, when Messrs. E. C.

May 1, 1906

By A. S. Keh, H. A. Wriedt

The Precipitation of nitrides in quenched Fe-N alloys, aged between 25° and 200°C, was studied by transmission electron microscopy. Different dislocation substructures were introduced into the materials by recrystallization, cold working, and by Phase transformation prior to the introduction of nitrogen. It was found that the precipitated nitrides, tentatively identified as Fe16N2, have (100) habit planes. Nucleation takes place Preferentially at dislocations and at subboundaries. It sometimes occurs in the matrix, probably on vacancy clusters, but rarely on high-angle boundaries. The process of nucleation on dislocations and subboundaries is very temperature dependent. At room temperature there is no particular orientation relationship between the dislocations involved and the (100) planes on which the nitride Particles formed. With increasing temperature, the nucleation sites tend to become restricted to those dislocation segments lying in (100) planes. The change of yield stress of the 0.022 and 0.043 pet N alloys during quench aging can be correlated semiquantitatively with the change in particle distribution. Strain aging in quenched alloys can be separated into two stages. The early stage is attributed to nitrogen segregation to dislocations and the later stage is associated with precipitation. When previously quench-aged specimens were strained and aged, no additional Precipitates could be seen, although a considerable amount of strain aging occurred. DURING the past two decades, the precipitation of nitrides from a iron has been extensively studied by various techniques. It has been established that two types of nitride exist. The stable nitride, Fe4N, forms at temperatures above 250oC and Fe16N2, the

Jan 1, 1962

By W. H. Bassett, J. C. Bradley

In their paper on the directional properties in cold-rolled and annealed commercial bronze,&apos; Phillips and Samans suggest that cupronickel, under distinctly different treatments, shows both "45" ears" and "90" ears. Fig. I shows the ears on some cupronickel cups made some 17 years ago for bullet jackets for small arms ammunition. In this case the material heated to 425° C. had "45" ears, while that annealed at 950°C. showed long "90" ears" when drawn with the same tools. The method of cupping, the shape of cupping tools, etc., were found to have very little influence on the earing tendency, but the deeper the cup was drawn, the higher the ears would be. Method of Manufacture Cupronickel cast bars were 1 in. thick. Ordinarily, they were rolled with numerous passes to a thickness of 0.4 to 0.2 in., according to conditions. They were then given a single intermediate anneal, and rolled to finish thickness, frequently 0.032 in. After a last anneal the material was cupped with a "cut and draw" operation. Progress of this is indicated in Fig. 2, illustrating five different stages at which the drawing

Jan 1, 1933

By A. Patton, F. N. Speller

The use of roll scale in the Bessemer process dates back, to the best of our knowledge, at least 20 years. It was first used by the Ohio Steel Go., Youngstown, Ohio (now the Ohio Works of the Carnegie Steel Co.) under the direction of Sam McDonald, Superintendent of the Bessemer Department at these works. Two 10-ton vessels and one blowing engine capable of blowing one heat at a time were employed. The object of using the scale was to shorten the length of the blow, or in other words, to increase the production with the same equipment. Various means were tried out for introducing the roll scale into the bath of molten iron: It was shoveled into the vessel before the heat was charged, so that the metal would flow over the scale; it was shoveled into the bath after the vessel was turned up; it was dumped into the empty iron ladle by the wheelbarrow-load, and at times was dumped on top of the molten metal in the iron ladle. But the practice of introducing the scale into the iron ladle had to be abandoned on account of danger from explosions and of skulling the ladles. It was soon learned that the proper place to charge the scale was in the empty vessel, so that when the molten iron was poured into the vessel it flowed over the scale, causing a considerabIe reaction to take place before the heat was turned up. Eventually, cylindrical chutes similar to those now in use were installed. Into these chutes the scale is dumped and carried into the empty vessel. Before this convenient means of introducing the scale was adopted, the Ohio Works had satisfactorily demonstrated that roll scale would increase production, by blowing 107 heats in one 12-hr. turn (1,087 tons) with one blowing engine, blowing one heat at a time; whereas, prior to the use of scale, the best practice at these works was about 80 heats under the same conditions. In using roll scale and other oxides of iron to facilitate and control the refining of pig iron in the converter, the Bessemer plant has borrowed one of the most active agencies used in the open-hearth process with, as would be expected, much the same results. The effect of such additions to the Bessemer charge may be discussed as to the influence of this practice on quality, production and cost.

Jan 1, 1917

By John S. Johnson, Thomas Fraser

SIZING is the process of separating mixed particles into groups of particles all of the same size, or into groups in which all particles range between certain definite maximum and minimum sizes. In coal preparation, sizing is generally accomplished by passing the coal over screens. Separation by differential settling in air or water currents has been adapted to the special field of separating very fine sizes, and these processes are in commercial use to a relatively small extent in the coal industry. Separation with screens is a very old industrial practice. Agricola described the use of screens for ore treatment in the middle ages. In the literature of the British coal industry references were made to the screening of coal as early as 1589, but the practice of extensive sizing for the market did not become general until the last half of the nineteenth century. In America, the practice of sizing developed first in the Pennsylvania anthracite region, beginning with the use of rakes in the mine working places to recover coarse coal. This mining procedure left the fines in the mine. Preparation outside the mine started with the installation of stationary cast-iron plates with 4 to 6-in. square holes. The run-of-mine coal was dumped upon the platforms, the large pieces of rock were picked out by hand, and the large lumps of coal were broken with hammers. The term "breaker," which still applies to the anthracite-preparation plant, originated with this practice, but the term is no longer descriptive of the entire function of the plant. In 1884, the first power-operated anthracite coal breaker was erected by Gideon Bart at his colliery at Wolf Creek near Minersville, Pa. This plant utilized a system of rolls for breaking the coal and revolving screens for sizing. The plant was driven by a steam engine. It could handle coal at the rate of 200 tons a day. By 1860, revolving screens were in wide use in the Pennsylvania anthracite field. Shaking screens were introduced in the Pennsylvania anthracite region in the 90&apos;s and they rapidly displaced the lower-capacity revolving screens.

Jan 1, 1950

By Alwyn Birchmore Cox, Ian William Wark

Different parts of the world in which mineral separation by flotation is practiced experience vastly different natural temperatures, and in some districts there is a big difference between summer and winter temperatures. It will be shown in this paper that the temperature is of considerable importance where it is desired to separate pyrite or arsenopyrite from other minerals. It is probable that some of the differences obtained in the flotation of these minerals at plants working under otherwise similar conditions are due to temperature variations. The influence of temperature on the flotation of galena, chalcopyrite and sphalerite by xanthates is less marked than its influence on pyrite flotation. Experimental Method The methods used have been described previously.l-4 In each test the clean mineral specimen was immersed in a solution prepared by adding the reagents in the following order: (1) sodium carbonate and hydrochloric acid as necessary to buffer the solution and to give approximately the pH value desired, (2) sodium cyanide, (3) copper sulphate, (4) ethyl xanthate, followed by (5) a final adjustment of pH value. After ½ hr. the mineral was tested for a xanthate film by bringing a bubble of air into apparent contact with the submerged polished surface. If true contact (spreading) was not obtained within ½ min. and after cleaning the surface by wiping with a small linen pad, it was concluded that the adsorption of a xanthate film had been prevented. Following the method already described (ref. 2), curves have been constructed such that for a solution composition corresponding to any point below the curve, contact between mineral and air is possible, whereas for a solution composition corresponding to any point above the curve, contact is impossible.

Jan 1, 1939

By Ian William Wark, Alwyn Birchmore Cox

Different parts of the world in which mineral separation by flotation is practiced experience vastly different natural temperatures, and in some districts there is a big difference between summer and winter temperatures. It will be shown in this paper that the temperature is of considerable importance where it is desired to separate pyrite or arsenopyrite from other minerals. It is probable that some of the differences obtained in the flotation of these minerals at plants working under otherwise similar conditions are due to temperature variations. The influence of temperature on the flotation of galena, chalcopyrite and sphalerite by xanthates is less marked than its influence on pyrite flotation. Experimental Method The methods used have been described previously.l-4 In each test the clean mineral specimen was immersed in a solution prepared by adding the reagents in the following order: (1) sodium carbonate and hydrochloric acid as necessary to buffer the solution and to give approximately the pH value desired, (2) sodium cyanide, (3) copper sulphate, (4) ethyl xanthate, followed by (5) a final adjustment of pH value. After ½ hr. the mineral was tested for a xanthate film by bringing a bubble of air into apparent contact with the submerged polished surface. If true contact (spreading) was not obtained within ½ min. and after cleaning the surface by wiping with a small linen pad, it was concluded that the adsorption of a xanthate film had been prevented. Following the method already described (ref. 2), curves have been constructed such that for a solution composition corresponding to any point below the curve, contact between mineral and air is possible, whereas for a solution composition corresponding to any point above the curve, contact is impossible.

Jan 1, 1939

By M. C. Flemings, F. R. Mollard

Conditions necessary for plane front growth of two-piwse solids from a single-phase melt are discussed. Alloys consideved are those from a simple binary system containing a eutectic, but are not, in general, of eutectic cornposition. It is concluded that: 1) plane front solzdification is favored by low growth rate, steep thermal gradient, and essential absence of convection; and 2) for steady-state solidification, the structure should resemble that of directionally solidified eutectics (lamellar, rodlike). Factors affecting THERE are many materials, including metals, available today with strengths in excess of 10&apos; psi when in whisker or fiber form. The challenge facing those interested in practical application of such materials has been, and remains, the economic production and incorporation of the whiskers or fibers into useful engineering composites. solute redistribution along the growth direction are described quantitatively, by numerical solution of the diffusion equation. Effects of variations in growtlz rate on average composition of the solidifying composite are significant. For alloys not too close to a single-phase region, the initial transient at constant gvowth velocity is the order of D/R where D is diffusion coefficient in the liquid and R is interface velocity. Composites consisting of the reinforcing phase within a metallic matrix have excited particular interest in recent years because of their potential for high strength at elevated temperature and for resistance to brittle fracture. Techniques employed to incorporate the whiskers or fibers in the metallic phase have included 1) liquid metal infiltration, 2) solid or liquid phase sintering, and 3) direct growth of composites from the melt, of rodlike or lamellar morphology, by directional solidification of eutectic alloys. Two recent books"2 have reviewed the status of this growing field. Concerning the last method, growth of eutectics, it has been shown that the reinforcing phase (e.g., rods)

Jan 1, 1968

By William Ian Wark, Alwyn Birchmore Cox

DIFFERENT parts of the world in which mineral separation by flotation is practiced experience vastly different natural temperatures, and in some districts there is a big difference between summer and winter temperatures. It will be shown in this paper that the temperature is of considerable importance where it is desired to separate pyrite or arsenopyrite from other minerals. It is probable that some of the differences obtained in the flotation of these minerals at plants working under otherwise similar conditions are due to temperature variations. The influence of temperature on the flotation of galena, chalcopyrite and sphalerite by xanthates is less marked than its influence on pyrite flotation. EXPERIMENTAL METHOD The methods used have been described previously.1-4 In each test the clean mineral specimen was immersed in a solution prepared by adding the reagents in the following order: (1) sodium carbonate and hydrochloric acid as necessary to buffer the solution and to give approximately the pH value desired, (2) sodium cyanide, (3) copper sulphate, (4) ethyl xanthate, followed by (5) a final adjustment of pH value. After ½ hr. the mineral was tested for a xanthate film by bringing a bubble of air into apparent contact with the submerged polished surface. If true contact (spreading) was not obtained within ½ min. and after cleaning the surface by wiping with a small linen pad, it was concluded that the adsorption of a xanthate film had been prevented. Following the method already described (ref. 2), curves have been constructed such that for a solution &apos; composition corresponding to any point below the curve, contact between mineral and air is possible, whereas for a solution composition corresponding to any point above the curve, contact is impossible.

Jan 1, 1938

By Charles W. Eichrodt

So much has already been wimitten on this vast subject of ground movement and subsidence, and so many data collected and commented upon, that in this paper the author proposes to confine himself to the submission of some plans showing what has actually occurred in the mining of several of the orebodies which have come under his direction during the last 20 years or so at Rio Tinto, Spain. Some notes are added for the purpose of describing the plans. The author does not attempt to give his opinion as to the reasons why the subsidences have occurred in the manner in which they are found, but confines himself to giving as true a picture as possible of the movements that have taken place. Effects of Excavation on Ground Movement Broadly, the effects of excavations on the overhead or adjacent ground can be classified under three headings, as follows: 1. Ground movements due to excavations made from surface only, such as those made in opencasts where no excavations underlie them. The stability and strength of the ground to resist movement must determine the slopes. 2. Ground movements due to underground excavations only; i. e., where the surface is not removed. 3. Ground movements due to a combination of both; i. e., from excavations taking place from the surface for the purpose of stripping an orebody and recovery of the ore to a certain horizon combined with excavations being carried out below, at the same time, for the winning of the ore below the horizon at which mining by stripping or opencasting under the specific conditions is no longer economical. Nos. 1 and 2 represent independent and distinct problems and No. 3 is a combination, which presents results much more difficult of explanation. The accompanying plans and sections give examples of what has occurred under the three conditions. Unfortunately, the class of ground is not exactly the same in them all, but the difference is not greater than is generally encountered over districts of equal area. Excavations from Surface To illustrate No. 1 three cross-sections are shown, of excavations made for the stripping and excavation from three different orebodies

Jan 1, 1930

By W. B. Hickman, J. J. Pickell, B. F. Swanson

Many physical properties of the porous media-immiscible liquid system are dependent upon the distribution of fluids within the pores; this in turn, is primarily a function of pore structure, liquid-liquiri interfacial tcnsion and liquid-solid wetting conditions. The cnpillary pressure hysteresis process provides a means of investigating the influence of pore structure upon fluid distribution for consistent sur/acc conditions. Invcstigntiot2s indicate that residual non-wetting-phase saturations /ollozuir,g the imbibition process (i.e.,wetting phase displacing nor2-wctting phase) are dependent upon both pore structure and initial non-raetting phase saturation and suggest that residual fluid is distributed as Discontinuous ,globules, one to a few pore sizes in dimension, thrnugh the entire range 01 pore sizes originally occupied. It clppears that air-mercury capillary pressure dala adequntely rellect the distribution of fluiris in a water-oil system when strong wetting condition preliczil. An oil-air counter-current imbibition technique has also been found to provide a rapid rneans of obtaining residual-initial saturation data. In a majority of cnses, rcsidual saturations detf-rniinecl from the oil-air or air-mercury process reasonably approximate residual oil saturation following water drive of a strongly water-wet medium. INTRODUCTION A reliable estimate of recoverable reserves depends not only on the amount of original oil-in-place but also on pore geometry and distribution of fluids within the pores. A critical parameter determining the recovery from a reservoir under waterflood, for example, is the amount and distribution of residual oil within the various rock types present. The purpose of this paper is to investigate the mechanism of capillary trapping and assess its importance in laboratory measureqents of residual oil saturation. The degree of wettability of a reservoir rock is recognized as an important factor in waterflood or imbibition experiments. In this paper, however, only the water-wet case has been considered. Considerable experimental evidence1 suggests that for water-wet rocks, capillary forces predominate in tile distribution of fluids and that viscous forces in the range normallv of interest in the reservoir have a minimum influence on residual oil saturation. It follows that if the ultimate recovery is controlled by pore geometry, a unique residual non-wetting phase saturation should exist for a given set of initial conditions. Two laboratory procedures.found to be extremely useful in the study of pore structure and degree of fluid interconnection at various saturations are decribed. Although air-nercury capillary injection curves have been used2 previously to characterize the drainage case, the withdrawal or imbibition case can provide valuable supplementary data. The air-mercury process, however, has several disadvantages; it is difficult to run in a sufficiently accurate manner, mercury does not always act as a strongly non-wetting liquid and in the air-mercury process the sample is rendered unsuitable for future analyses. An alternative process is described in which air is the non-wetting phase and naptha, hentane, octane or toluene is the wetting phase. INTERFACIAL TENSION AND CAPILLARY PRESSURE Interfacial tension between immiscible fluids is due to the difference in attraction of like molecules as compared with their attraction to molecules of the neighbouring fluid. This net attraction results in a tension at the interface. To extend the interface; thus, interfacial tension s can also be thought of as free surface energy. Interfacial tension is normally expressed as dynes/cm, and interfacial energy is measured in ergs/cm2 hence, both have dimensions ml A 2 and are numerically equal.

Jan 1, 1967

By Joseph P. Kittredge

At the time this matter first came up in 1912, the National Malleable and Steel Castings Co. had seven basic-bottom open-hearth furnaces in its plant at Sharon, Fa., using fuel oil, then costing about 2½¢ per gallon. The fuel was satisfactory but its cost fluctuated widely, therefore the use of pulverized coal, which had been successful in the cement industry and in some metallurgical furnaces, was suggested. After a thorough investigation, and an actual trial on one of the open-hearth furnaces, to be certain that the siliceous ash in the coal would not seriously affect the basic slags, the management of this company approved its adoption and a complete installation was started. The conclusion had been reached that the success of the operation depended on pulverizing the coal to greater fineness than had thus far been accomplished, and all equipment was chosen with this in mind. A coal drier was deemed essential, and one of ample capacity and efficiency was selected, which has done all that was expected of it, working without failure and with very small maintenance cost, and is still in operation. Pulverizers The company demanded a pulverization of at least 90 per cent through a 240-mesh screen, with consistent results, and a machine was chosen that was grinding other materials than coal to the fineness desired. The control of fineness was obtained through a vacuum separator, and was governed by the size of the separator and the number and construction of the valves necessary to expand and direct the air current. These valves can be set to obtain any degree of fineness desired, and the result is consistent. Two machines were installed, each capable of producing 2½ tons per hour, 95 per cent through 240 mesh. These machines have done everything expected of them, have run continuously, and are still in operation. An examination of some of our pulverized coal by elutriation and microscopic measurement disclosed that a 1-lb. lump of bituminous coal,

Jan 1, 1940

By Joseph P. Kittredge

At the time this matter first came up in 1912, the National Malleable and Steel Castings Co. had seven basic-bottom open-hearth furnaces in its plant at Sharon, Fa., using fuel oil, then costing about 2½¢ per gallon. The fuel was satisfactory but its cost fluctuated widely, therefore the use of pulverized coal, which had been successful in the cement industry and in some metallurgical furnaces, was suggested. After a thorough investigation, and an actual trial on one of the open-hearth furnaces, to be certain that the siliceous ash in the coal would not seriously affect the basic slags, the management of this company approved its adoption and a complete installation was started. The conclusion had been reached that the success of the operation depended on pulverizing the coal to greater fineness than had thus far been accomplished, and all equipment was chosen with this in mind. A coal drier was deemed essential, and one of ample capacity and efficiency was selected, which has done all that was expected of it, working without failure and with very small maintenance cost, and is still in operation. Pulverizers The company demanded a pulverization of at least 90 per cent through a 240-mesh screen, with consistent results, and a machine was chosen that was grinding other materials than coal to the fineness desired. The control of fineness was obtained through a vacuum separator, and was governed by the size of the separator and the number and construction of the valves necessary to expand and direct the air current. These valves can be set to obtain any degree of fineness desired, and the result is consistent. Two machines were installed, each capable of producing 2½ tons per hour, 95 per cent through 240 mesh. These machines have done everything expected of them, have run continuously, and are still in operation. An examination of some of our pulverized coal by elutriation and microscopic measurement disclosed that a 1-lb. lump of bituminous coal,

Jan 1, 1940