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By Paul M. Tyler

YEAR after year, the kaolin industry of the United States has been setting new production records and making better products. High-grade paper, pottery, and rubber clays are produced in this country mostly in the South. Georgia alone contributes over 70 pct and South Carolina almost 20 pct of the total domestic output. Residual kaolin is mined in North Carolina, highly plastic but naturally sandy Tertiary (Eocene) potting clays are worked in north central Florida, and good white clays are produced in several other states, but the main sources of kaolin or china clay have been numerous deposits in the Tuscaloosa (Upper Cretaceous) formation. This formation of generally sandy sediments is called the Middendorf member in older geologic reports and corresponds in age with some of the New Jersey clays. As shown in fig. 1, it crops out almost continuously in a generally southwesterly direction across South Carolina and Georgia and into Alabama. Clay is mined from this formation in all three states but the principal producing centers lie within about 10 miles of a straight line drawn between Aiken, S. C., and a point about 10 miles south of Macon, Ga. The white kaolins of the South were recognized and used prior to the Civil War but suitable treatment processes were not introduced until World War I when imports, chiefly from England, were curtailed. Although imports of high-grade clays were resumed after 1918, the domestic industry managed to treble its prewar production record during the early 1920's and has continued to grow. Whereas the 1909 to 1913 average total production in the United States was only 132,104 short tons valued at $705,352 f.o.b. mines, the output in 1948 was 1,568,848 tons worth $19,756,738.

Jan 6, 1950

By Leland L. Mink, Roy E. Williams, C. Daniel Kealy

The passage by Congress of Public Law 92-500 (the 1972 Water Pollution Control Act amendment) has placed a new emphasis on the need for methods to minimize the escape of water from tailings ponds. Presumably tailings pond seepage will fall under the jurisdiction of the act. This paper is designed to explain some of the problems caused by leakage from tailings ponds and to present a method by which leakage can be minimized if not eliminated. Ground-water pollution in one case studied by the authors results from leaching of old jig tailings that are intermixed with the upper part of a sand and gravel aquifer. Anomalous concentrations of zinc, lead, and cadmium occur in ground water and soil samples taken from the portion of the sand and gravel aquifer containing the old jig tailings. Analysis of water samples from a tailings pond located in the area indicates that the pond water is not the source of the heavy metal concentrations found in the down-gradient ground water. However, leakage from the pond and water from the pond's decant system combine with natural ground water to compound the problem by raising the water table into old jig tailings which cover the upper portion of the aquifer. The ground water which discharges from this aquifer causes a statistically significant decrease in the quality of the receiving stream water. The shallow ground water contains oxygen; therefore, corrective measures include lowering the water table to depths below the old jig tailings which cover the aquifer at ground level. This, in turn, implies elimination of ground-water recharge by subsurface leakage from the pond. A laboratory study and a mathematical model study have revealed that seepage from such ponds can be minimized by a carefully designed and managed peripheral tailings discharge system. The process involves maintaining the slime zone and the free-water surface near the center of the pond so that the slimes retard downward and semilateral movement of pond water. The free-water surface must not be allowed to extend out over the nonslime portion of the tailings during or after pond operation. Mathematical model output reveals that this method can hold the subsurface discharge rate to as little as 110 gpd per acre of pond water area. The technique should be applicable to any tailings pond system in which the loss via seepage of poor quality water must be minimized or where recharge of ground water by losses from a tailings pond must be minimized, regardless of the reason.

Jan 1, 1974

By P. C. Johnson, B. A. Stein

This paper describes a study of the effects of combined heat treatment and explosive loading on the mechanical properties of high-strength steels. nis program investigated two distinct areas: 1) the effect of shock waves, without gross irreversible defmmution, on a 3-Cr steel at various stages of heat treatment; and 2) the effect of rapid deformation (explosive forming) on H-11 and D6-AC steels in the metastable austenitic state. The mechanical properties of these steels were improved, in some cases markedly, as a result of these treatments. ,AUSFORMWG, which requires the plastic deformation of metastable austenite, is a process which can appreciably improve the properties of selected alloy stee1s.l,2 The Ausform process significantly increases the strength of these steels without decreasing their ductility. The properties at high temperatures are also improved through a change in the response of the steels to tempering. Although the mechanism by which ausforming alters the properties of these steels is not fully understood, it appears that the dislocation arrays produced by deformation of the metastable austenite influence the structure of the martensite on subsequent transformation. This, in turn, affects the strength, ductility, and tempering response of the martensite. This research used chemical explosives to deform steels at various stages in their heat treatment in order to improve the properties of these steels. The explosive energy is used in two ways; 1) high-pressure shock waves are propagated through the steel to produce extensive microscopic shear strain without causing a large irreversible change in shape, and 2) explosive energy is used to cause extensive macroscopic plastic strain in the metastable austenitic state (explosive forming). I) AUSFORMING WITH INTENSE SHOCK WAVES The steel used in this phase of the research was an alloy having a nominal composition 0.43 pct C, 3.0 pct Cr, 1.5 pct Ni, and 1.5 pct Si. The steel was subjected to intense shock waves in three conditions: 1) in the metastable austenitic state, 2) in the tempered mar tens itic state, and 3) in the tempered martensitic state after ausforming by conventional techniques. The specimens were in the form of disks 2.75 in. in diam and 5/16 in. thick. These were incorporated into a specimen assembly consisting of two disks pressed into a 5 by 5 by 1 in. block of stainless steel, Fig. 1. Spalling (or scabbing) is confined to the front disk. The specimen is protected from oxidation and decarburization by the surrounding metal. The temperature of the assembly is monitored by a thermocouple inserted into one side of the stainless steel block. The assembly is positioned over an oil reservoir which serves both as a means of catching the disks and as quenching medium for the disks shocked under ausforming conditions. Plane shock waves are introduced into the assembly by a metal driver plate impacting the top surface of the block. The driver plate is accelerated by a chemical explosive sheet supplied by E. I. du Pont de Nemours & Co. All the specimens were subjected to plane shock waves having a peak pressure of approximately 430 kbar. The pressure is that quoted by G. E. Dieter for the plane wave generator used in this work.' The driver plate used was 1/4 in. thick, so that the initial pulse was essentially a l/2-in.-wide square wave. The attenuation of the peak pressure during the subsequent 1/4 in. is estimated to be less than 5 pct. The shock front induces a temperature rise, a portion of which is irreversible. Rough estimates (+25 pct) of this temperature rise have been made for iron shocked at room temperature.4 For a 500-kbar shock wave, the temperature rise in the shock front is about 700°F, and is held for a time of the order of microseconds. The irreversible temperature rise, which remains after the shock wave passes, is about 450°F.4 The disks are quenched to room temperature within a few seconds of the shock treatment. It should be emphasized that the temperature rises given above are estimates for pure iron at room temperature, and are not necessarily true for the tests made in this work. The disks shocked at temperatures in the metastable austenitic range were austenitized in the stainless steel assembly in a furnace protected from the firing area. The assembly was removed from the furnace and placed over the recovery reservoir. The plane wave generator was then positioned and

Jan 1, 1963

By C. E. Reinhard

A useful accelerated weathering test should be capable of placing any series of metals quantitatively in the same order of endurance as that noted under a particular set of actual exposure conditions. The development of such a test must necessarily depend to a considerable extent upon data obtained from a wide variety of exposures. This paper offers preliminary data from exposure tests on nine metals placed in 11 locations in the Lehigh Valley, within a radius of 20 miles from Palmerton. The exposure conditions vary from a severe industrial atmosphere to a pure rural atmosphere. The data are offered as evidence of the necessity for the identification and evaluation of the variables of corrosion and as illustration of some of the variations to be considered in the development of a useful accelerated test. It is quite clear, from this evidence, that a useful accelerated test must be versatile to the extent of showing the probable variations of corrosion resulting from differences in atmosphere as well as from differences in the metals. The paper is presented solely with the object of pointing out the wide variations in relative merits of several common metals in resisting corrosion and without any thought of initiating controversy regarding the merits of particular metals. For this reason the metals are designated only by symbols in the tables and no key is given to these symbols. Test Procedure Specimens, 4 by 6 in., were cut to accurate dimensions from each of the following metals or alloys: aluminum, ascoloy, copper, copper steel, galvanized iron, and zinc. Additional grades of these metals bring the total to nine types. Since it was impossible to obtain the required number of copper-steel specimens having equal surface conditions of rust and scale, it was thought advisable to pickle these specimens in a hot solution of 10 per cent. sulfuric acid. All other specimens were carefully cleaned in ether and alcohol and weighed just prior to exposure. Four specimens of each type of metal were mounted on a test rack by means of porcelain insulators. The racks were so constructed that

Jan 1, 1929

By C. E. Reinhard

A useful accelerated weathering test should be capable of placing any series of metals quantitatively in the same order of endurance as that noted under a particular set of actual exposure conditions. The development of such a test must necessarily depend to a considerable extent upon data obtained from a wide variety of exposures. This paper offers preliminary data from exposure tests on nine metals placed in 11 locations in the Lehigh Valley, within a radius of 20 miles from Palmerton. The exposure conditions vary from a severe industrial atmosphere to a pure rural atmosphere. The data are offered as evidence of the necessity for the identification and evaluation of the variables of corrosion and as illustration of some of the variations to be considered in the development of a useful accelerated test. It is quite clear, from this evidence, that a useful accelerated test must be versatile to the extent of showing the probable variations of corrosion resulting from differences in atmosphere as well as from differences in the metals. The paper is presented solely with the object of pointing out the wide variations in relative merits of several common metals in resisting corrosion and without any thought of initiating controversy regarding the merits of particular metals. For this reason the metals are designated only by symbols in the tables and no key is given to these symbols. Test Procedure Specimens, 4 by 6 in., were cut to accurate dimensions from each of the following metals or alloys: aluminum, ascoloy, copper, copper steel, galvanized iron, and zinc. Additional grades of these metals bring the total to nine types. Since it was impossible to obtain the required number of copper-steel specimens having equal surface conditions of rust and scale, it was thought advisable to pickle these specimens in a hot solution of 10 per cent. sulfuric acid. All other specimens were carefully cleaned in ether and alcohol and weighed just prior to exposure. Four specimens of each type of metal were mounted on a test rack by means of porcelain insulators. The racks were so constructed that

Jan 1, 1929

By R. C. Edwards, T. G. Kirkland, Will Mitchell

A scrubber of new design has been invented for the beneficiation of glass and chemical sands. The machine is described and its capacity and metallurgical efficiency compared with the performance of other sand cleaning devices. THREE years ago, when the Process Research Laboratory at Allis-Chalmers Manufacturing Co. sought a remedy for the increasing cost of disposing of great quantities of spent sands from foundries, R. C. Edwards developed a continuous inclined paddle scrubber which removed a substantial amount of the charred coatings from the grains with a surprisingly small amount of degradation of the sand itself.' The satisfactory results obtained on foundry sand, using this piece of equipment in conjunction with classification, suggested that a similar procedure could probably be applied to the cleaning of other sands, such as those required by the glass and chemical industries. This paper describes the flowsheet and the results of tests performed on impure natural sands. The four materials tested were silica sands obtained from widely separated geographical areas. Three of the sands tested contained various amounts of iron oxide and the fourth an excessive amount of calcareous bonding material. The iron oxide was present predominantly in the form of grain coatings, which were scuffed by the paddle scrubber, and in all cases a product was manufactured which would meet one of the sets of specifications imposed by the glass industry.' The Edwards paddle scrubber used in these tests consists of a rubber-lined steel cylinder 18 in. in diam and 48 in. long, mounted on a frame so that its slope can be varied 5" to 35" from horizontal. This variable slope permits controlled flow of material through the machine. Rubber paddles rotate inside the cylinder and are secured to a center shaft 2 in. square, which extends through the entire length and is turned at both ends so that it can be supported by sleeve bearings centrally fixed in the end plates of the shell. At the upper or feed end it extends through the bearing on the end plate into a sheave, to which the motor drive is connected by means of Texrope transmission. The four sets of paddles mounted on the shaft, two in each set, are made of rubber belting, 1/4 in. thick, 9 in. wide, and 16 in. long. The two paddles in each set are secured on opposite sides of the square shaft, but in the same longitudinal position along the shaft axis. In other words, the two paddles in the set operate 180" apart. Each successive set is mounted 90" from the preceding one. One end of each paddle is bolted to the square shaft and the other weighted by a steel bar, lx1 1hx9 in. long, which is attached about Yz in. from the outer tip of the paddle. By centrifugal force at proper shaft speed, these weights force the paddle surface to rub smoothly against the rubber lining of the cylinder. During operation, the sand forces its way between the paddle face and the surface of the cylinder, providing the necessary abrading action as the pulp flows by gravity down the length of the cylinder. The capacity of the machine is limited by the amount and the hardness of the coating material and by the quality of product desired. The degree of scrubbing is governed by the retention time in the scrubber, which in turn may be changed by varying the feed rate, water content of the feed, and

Jan 1, 1953

By R. C. Edwards, T. G. Kirkland, Will Mitchell

A scrubber of new design has been invented for the beneficiation of glass and chemical sands. The machine is described and its capacity and metallurgical efficiency compared with the performance of other sand cleaning devices. THREE years ago, when the Process Research Laboratory at Allis-Chalmers Manufacturing Co. sought a remedy for the increasing cost of disposing of great quantities of spent sands from foundries, R. C. Edwards developed a continuous inclined paddle scrubber which removed a substantial amount of the charred coatings from the grains with a surprisingly small amount of degradation of the sand itself.' The satisfactory results obtained on foundry sand, using this piece of equipment in conjunction with classification, suggested that a similar procedure could probably be applied to the cleaning of other sands, such as those required by the glass and chemical industries. This paper describes the flowsheet and the results of tests performed on impure natural sands. The four materials tested were silica sands obtained from widely separated geographical areas. Three of the sands tested contained various amounts of iron oxide and the fourth an excessive amount of calcareous bonding material. The iron oxide was present predominantly in the form of grain coatings, which were scuffed by the paddle scrubber, and in all cases a product was manufactured which would meet one of the sets of specifications imposed by the glass industry.' The Edwards paddle scrubber used in these tests consists of a rubber-lined steel cylinder 18 in. in diam and 48 in. long, mounted on a frame so that its slope can be varied 5" to 35" from horizontal. This variable slope permits controlled flow of material through the machine. Rubber paddles rotate inside the cylinder and are secured to a center shaft 2 in. square, which extends through the entire length and is turned at both ends so that it can be supported by sleeve bearings centrally fixed in the end plates of the shell. At the upper or feed end it extends through the bearing on the end plate into a sheave, to which the motor drive is connected by means of Texrope transmission. The four sets of paddles mounted on the shaft, two in each set, are made of rubber belting, 1/4 in. thick, 9 in. wide, and 16 in. long. The two paddles in each set are secured on opposite sides of the square shaft, but in the same longitudinal position along the shaft axis. In other words, the two paddles in the set operate 180" apart. Each successive set is mounted 90" from the preceding one. One end of each paddle is bolted to the square shaft and the other weighted by a steel bar, lx1 1hx9 in. long, which is attached about Yz in. from the outer tip of the paddle. By centrifugal force at proper shaft speed, these weights force the paddle surface to rub smoothly against the rubber lining of the cylinder. During operation, the sand forces its way between the paddle face and the surface of the cylinder, providing the necessary abrading action as the pulp flows by gravity down the length of the cylinder. The capacity of the machine is limited by the amount and the hardness of the coating material and by the quality of product desired. The degree of scrubbing is governed by the retention time in the scrubber, which in turn may be changed by varying the feed rate, water content of the feed, and

Jan 1, 1953

By R. C. Edwards, Will Mitchell, T. G. Kirkland

A scrubber of new design has been invented for the beneficiation of glass and chemical sands. The machine is described and its capacity and metallurgical efficiency compared with the performance of other sand cleaning devices. THREE years ago, when the Process Research Laboratory at Allis-Chalmers Manufacturing Co. sought a remedy for the increasing cost of disposing of great quantities of spent sands from foundries, R. C. Edwards developed a continuous inclined paddle scrubber which removed a substantial amount of the charred coatings from the grains with a surprisingly small amount of degradation of the sand itself.' The satisfactory results obtained on foundry sand, using this piece of equipment in conjunction with classification, suggested that a similar procedure could probably be applied to the cleaning of other sands, such as those required by the glass and chemical industries. This paper describes the flowsheet and the results of tests performed on impure natural sands. The four materials tested were silica sands obtained from widely separated geographical areas. Three of the sands tested contained various amounts of iron oxide and the fourth an excessive amount of calcareous bonding material. The iron oxide was present predominantly in the form of grain coatings, which were scuffed by the paddle scrubber, and in all cases a product was manufactured which would meet one of the sets of specifications imposed by the glass industry.' The Edwards paddle scrubber used in these tests consists of a rubber-lined steel cylinder 18 in. in diam and 48 in. long, mounted on a frame so that its slope can be varied 5" to 35" from horizontal. This variable slope permits controlled flow of material through the machine. Rubber paddles rotate inside the cylinder and are secured to a center shaft 2 in. square, which extends through the entire length and is turned at both ends so that it can be supported by sleeve bearings centrally fixed in the end plates of the shell. At the upper or feed end it extends through the bearing on the end plate into a sheave, to which the motor drive is connected by means of Texrope transmission. The four sets of paddles mounted on the shaft, two in each set, are made of rubber belting, 1/4 in. thick, 9 in. wide, and 16 in. long. The two paddles in each set are secured on opposite sides of the square shaft, but in the same longitudinal position along the shaft axis. In other words, the two paddles in the set operate 180" apart. Each successive set is mounted 90" from the preceding one. One end of each paddle is bolted to the square shaft and the other weighted by a steel bar, lx1 1hx9 in. long, which is attached about Yz in. from the outer tip of the paddle. By centrifugal force at proper shaft speed, these weights force the paddle surface to rub smoothly against the rubber lining of the cylinder. During operation, the sand forces its way between the paddle face and the surface of the cylinder, providing the necessary abrading action as the pulp flows by gravity down the length of the cylinder. The capacity of the machine is limited by the amount and the hardness of the coating material and by the quality of product desired. The degree of scrubbing is governed by the retention time in the scrubber, which in turn may be changed by varying the feed rate, water content of the feed, and

Jan 1, 1953

By R. C. Edwards, Will Mitchell, T. G. Kirkland

A scrubber of new design has been invented for the beneficiation of glass and chemical sands. The machine is described and its capacity and metallurgical efficiency compared with the performance of other sand cleaning devices. THREE years ago, when the Process Research Laboratory at Allis-Chalmers Manufacturing Co. sought a remedy for the increasing cost of disposing of great quantities of spent sands from foundries, R. C. Edwards developed a continuous inclined paddle scrubber which removed a substantial amount of the charred coatings from the grains with a surprisingly small amount of degradation of the sand itself.' The satisfactory results obtained on foundry sand, using this piece of equipment in conjunction with classification, suggested that a similar procedure could probably be applied to the cleaning of other sands, such as those required by the glass and chemical industries. This paper describes the flowsheet and the results of tests performed on impure natural sands. The four materials tested were silica sands obtained from widely separated geographical areas. Three of the sands tested contained various amounts of iron oxide and the fourth an excessive amount of calcareous bonding material. The iron oxide was present predominantly in the form of grain coatings, which were scuffed by the paddle scrubber, and in all cases a product was manufactured which would meet one of the sets of specifications imposed by the glass industry.' The Edwards paddle scrubber used in these tests consists of a rubber-lined steel cylinder 18 in. in diam and 48 in. long, mounted on a frame so that its slope can be varied 5" to 35" from horizontal. This variable slope permits controlled flow of material through the machine. Rubber paddles rotate inside the cylinder and are secured to a center shaft 2 in. square, which extends through the entire length and is turned at both ends so that it can be supported by sleeve bearings centrally fixed in the end plates of the shell. At the upper or feed end it extends through the bearing on the end plate into a sheave, to which the motor drive is connected by means of Texrope transmission. The four sets of paddles mounted on the shaft, two in each set, are made of rubber belting, 1/4 in. thick, 9 in. wide, and 16 in. long. The two paddles in each set are secured on opposite sides of the square shaft, but in the same longitudinal position along the shaft axis. In other words, the two paddles in the set operate 180" apart. Each successive set is mounted 90" from the preceding one. One end of each paddle is bolted to the square shaft and the other weighted by a steel bar, lx1 1hx9 in. long, which is attached about Yz in. from the outer tip of the paddle. By centrifugal force at proper shaft speed, these weights force the paddle surface to rub smoothly against the rubber lining of the cylinder. During operation, the sand forces its way between the paddle face and the surface of the cylinder, providing the necessary abrading action as the pulp flows by gravity down the length of the cylinder. The capacity of the machine is limited by the amount and the hardness of the coating material and by the quality of product desired. The degree of scrubbing is governed by the retention time in the scrubber, which in turn may be changed by varying the feed rate, water content of the feed, and

Jan 1, 1953

By Donald B. Evans, Robert D. Pehlke

The solubility of nitrogen in liquid Fe-A1 alloys has been measured up to the solubility limit for formation of aluminum nitride using the Sieverts method. The activity coefficient of nitrogen decreases slightly with increasing aluminum content in the range of 0 to 4 wt pct Al. Based on a nitride composition, AlN, the standard free energy of formation of aluminum nitride from fhe elements dissolved in liquid iron has been determined to be: ?F" = -59,250 + 25.55 T in the range from 1600º to 1750ºC. The solubility of nitrogen in liquid iron alloys and the interaction of nitrogen with dissolved alloying elements in liquid iron have been the subject of a number of research investigations.' Most of this work, however, has been reported for concentrations well below those necessary for the formation of the alloy nitride phase. Data in the concentration region near the solubility limit of the alloy nitride, particularly for systems exhibiting stable nitrides, are important in evaluating the denitrifying power of various alloying elements. They are also useful in determining the stability of a given nitride if it is to be used as a refractory to contain liquid iron alloys. In view of the importance of aluminum as a deoxidizing agent in commercial steelmaking and the fact that its nitride, AIN, is a highly stable compound and has merited some consideration as an industrial refractory, the following investigation was undertaken. The use of the Sieverts technique provided a measurement of the equilibrium nitrogen solubility in liquid Fe-A1 alloys as a function of nitrogen gas pressure up to 3.85 wt pct A1 in the temperature range of 1600º to 1750°C. The values obtained by the Sieverts method were checked by means of a quenching method in which liquid iron was equilibrated with an A1N crucible under a known partial pressure of nitrogen gas, and the solubility of A1N in liquid iron determined by chemical analysis. EXPERIMENTAL PROCEDURE The theoretical considerations involved in determining the solubility product of a solid alloy nitride phase in liquid iron by measuring the point of departure of the nitrogen gas solubility from Sieverts law have been discussed by Rao and par lee.' The principal problem is to determine the variation of nitrogen solubility in an alloy as a function of the pressure of nitrogen gas over it with sufficient precision to establish the break point in the curve at the solubility limit of the alloy nitride phase. A fairly large number of data points are required to do this. A second problem is the determination of the composition of the precipitated solid nitride phase. This is necessary in order to define completely the thermodynamic relationships. The Sieverts apparatus used to make the nitrogen solubility measurements in this investigation is of essentially the same design as that described by Pehlke and E1liott.l The charge materials were Ferrovac-E high purity iron supplied by Crucible Steel Co. and 99.99+ pct pure aluminum. Recrystal-lized alumina crucibles were used, and were not attacked by the liquid alloys. The hot volume of the system which was measured for each melt ranged from 46 to 50 standard cu cm and was found to decrease linearly with decreasing pressure and with increasing temperature. The temperature coefficient of the hot volume at 1 atm pressure of argon gas was essentially constant for all experiments at a value of -6 X 10-3 cu cm per "C. The melt temperature was measured with a Leeds and Northrup disappearing filament type optical pyrometer sighted vertically downward on the center of the melt surface. The temperature scale was calibrated against the observed melting point of pure iron taken as 1536°C. The emissivity of all melts was assumed to be that of pure iron, taken as 0.43. The charge weights ranged from 110 to 140 g and the range of aluminum contents covered was from 0 to 3.85 wt pct. Aluminum additions were made as 12 to 15 wt pct A1-Fe master alloys previously prepared in the system under purified argon. The compositions of the master alloys were checked by chemical analysis and found to be in agreement with the charge analyses. Vertical cross sections of the master-alloy ingots were used as charge material for the equilibrations in order to minimize the effect of any segregation which might have occurred during solidification of the master alloys. Determinations of the solubility product of

Jan 1, 1964

By H. W. Turner

In addition to the deposits mentioned by Mr. Lindgren? the following may be noted: 1. In the " Dardanelles quadrangle," of the map of the U. S. Geological Survey, 3 miles NW. of Tower Peak, there is a considerable mass of quartzite, marble, and dark, fine-grained. gneiss. At the edge of the coarsely crystalline white marble, having a width of about 400 ft., is a white schistose rock, which,

Jan 1, 1904

By John B. Hastings

The occurrellce of such a large amount of gold in the Hart-eel granite, even though the surmised existence of similar areas is not new, brings freshly to mind the pegmatite type of mag-matic differentiation lately brought again to attention by occurrences at Silver Peak, Nev., described by Spurr; and in Alaska, described by both Spurr and Brooks. In both localities granitic rocks or dikes are thought to pass into metalliferous quartz-veins. An interesting association in this connection is the occurrence of diamonds in residual pegmatitic clay of Sail Juao de Chapado, Brazil, described by Derby :' (P. 142) "Bodies of pegmatite are quite common in the older rocks of Brazil, both in the diamond regions and elsewhere, occurring not only in the gneiss and granite, but in the schistose series as well. Those that have been examined are dike-like in their mode of occurrence and granitic in composition.'' (P. 143) '" The question of the eruptive or secretionary origin of pegmatites has long been a subject of discussion among geologists.... The recent studies .. seen] to have clearly established that most if not all of them are essentially eruptive masses, though possibly modified in some way by aqueous agencies. Even before becoming acquainted with the literature of the subject this view had seemed to me to be the only acceptable one as regards the typical pegmatites of Brazil." What is pegmatite ? J. F. Kemp says :2 "... veins or dikes—it is an open question which is the more correct term— are met formed of very coarsely crystalline aggregates of the same minerals that constitute granite. These are called pegmatite and in them is the home of graphic granite, the curious intergrowth of quartz and feldspar, such that a cross fracture of the blades of quartz suggests cuneiform characters.... In regard to the larger veins or dikes it seems improbable that true igneous fusion could have afforded such coarsely crystalline aggregates, and so we are forced to assume such abundance of steam and other vapors, i.e, mineralizers, as to almost, if not quite, imply solution."

Jan 1, 1909

By S. K. Tarby, W. O. Philbrook

The rate of FeO and MnO reduction from silicate and aluminate slags by carbon-saturated iron is dependent on both slag composition and temperature. Owing to variable stirring rules during- the course of reaction, the reduction processes occur in two stages in stationary graphite crucibles. In the first stage the slirring caused by CO evolution results in forced convection conditions in the slag. As the boiling action subsides during reduction, the flow conditions within the system become those defined by natural convection. Analysis of the data by an unsteady-state penetration model indicates that the rate of reduction is controlled by the rate of cocur-rent flow of' cations and anions from the bulk slag to the interface during both stages of reduction. The hearth reactions of the blast furnace have been extensively investigated from the viewpoint of equilibrium by deductions from controlled laboratory experiments. However, the literature contains relatively few studies that have been directed toward the area of slag-metal reaction kinetics, and the majority of these have been concerned with the rate and mechanism of sulfur transfer between iron and slag. More recently, attention has turned to the kinetic factors in the reduction of oxides from liquid slags. One of the first investigations in this field was conducted by Dancy1 on the reduction of pure liquid FeO and pure liquid Fe3O4 by carbon-saturated iron. The integrated form of the rate equation indicated that the reduction of FeO was of the first order up to 80 pct reduction. Over the initial 30 pct of reduction, the magnetite reaction was also interpreted as a first-order process. The rates of reaction were extremely rapid as indicated by a 30 pct reduction of the liquid magnetite in a time interval of about 1 to 2 sec. Phil-brook and irkbbride' studied the reduction of FeO from a lime-alumina-silica slag by carbon-saturated iron and solid graphite in stationary crucible assemblies. With the use of the differential form of the rate equation, the rate of the reduction reaction was found to be proportional to the second power of the concentration of the reactant FeO for both the slag-metal and slag-graphite reactions. These authors presented a number of comments in an effort to explain the difference between the molecularity of the above reaction and the observed second-order relation. One such argument, recently extended by Wagner,3 was that the rate-limiting step may well be one of transport control. A complete discussion of the proposed mass-transport control mechanism of this reduction reaction will be presented in a later section of this paper. Kinetic studies of the reduction of other oxide species, namely chromous oxide, titania, and silica, have also been reported. McCoy and philbrook4 used rotating crucible assemblies to investigate chromium reduction from Ca0-SiO2-A12O3 slags. First-order kinetic law was obeyed for the slag-metal reduction reaction as determined by the integration method of data analysis. Due to scatter of the data, any dependence of the rate constant on temperature or slag composition was obscured. Concentration-time data for the reduction of titania from blast-furnace type slags under reducing conditions were obtained by Delve, Meyer, and Lander.' The data were too few, however, for a formal kinetic interpretation. Kinetic data for the very slow reaction of silica reduction have been observed by McCoy and Philbrook6 and Fulton and chipman.7 The former experimenters found the reaction-rate constant for silica reduction by carbon-saturated iron to be 20 to 60 times less than the rate constant for chromium reduction. In their work on the reduction of SiO2 in mechanically stirred systems, Fulton and Chipman also found small values for the specific reaction rate and derived a high value for the energy of activation for the reaction. In both of these investigations, the reduction process was assumed to follow first-order behavior. schuhmann8 proposed that the rate-limiting step in this reaction is the diffusion of oxygen from the interface through a boundary-layer film to the bulk metal phase, and Rawling and Elliott9 have reported experimental confirmation of this hypothesis for temperatures below 1600°C. Turkdogan et a1.10 have also concluded that the rate of reduction of silica is a slow process and controlled by the diffusion of oxygen in the metal, but only in the absence of carbon monoxide bubbles at the slag-metal interface. In the presence of bubbles, achieved either by injecting carbon monoxide at the slag-metal interface or by blowing it through the metal and slag, these investigators found a rather rapid reduction of silica which appeared to be controlled by an interfacial reaction involving the de-sorption of silicate ions from the slag-metal interface to the metal phase as silicon and oxygen atoms. In view of the unresolved nature of the kinetics of FeO reduction and the lack of kinetic data for the manganese reaction,

Jan 1, 1968

By Edward Sayre

IN shaft sinking for coal mines, the cost item greatly influences the method adopted. This holds true especially when soft material must be traversed. The average life of a coal mine is short. This is clue either to the limited area of the coal basin or to the great expense of maintenance and haulage underground when the entries are extended a considerable distance from the hoisting shaft. Therefore, the engineer in opening a coal mine is confronted with the fact that the cost must be kept within certain bounds else the venture will prove unprofitable. For this reason he may be prohibited from adopting certain safe, but expensive, methods that are used in sinking caissons for foundations, driving transportation tunnels, or other work of permanent construction. A common method of sinking through difficult ground employs the aid of a steel shoe pushed ahead of the shaft timbers. Another is the drop-shaft method. These two methods were used in sinking the main shaft and the air shaft of the Eagle No. 3 mine, at Des Moines, Ia., and the following data show the relative success and cost of the two methods of sinking under the same conditions. A drill log of the material to be penetrated was as follows (see Plate 1, Fig. .1)

Jan 9, 1916

By W. L. Austin

THE advance made in recent times in this branch of metallurgy is indicated y the attention the subject is receiving from important American copper-producing companies. Reference to the files of publications devoted to the mining industry discloses that some 20 American companies are actively investigating the amenability of their ore, or other material, to leaching methods, and that plants of varying capacities up, to 10,000 tons per day are under construction or are projected. Several leaching works are in commercial operation. It has been frequently pointed out that no method of leaching is universally applicable, for the reason that each ore differs in some particular from apparently similar ore found elsewhere, and also because local conditions are rarely the same even where the ore closely approximates in character that being worked at some other point. For this reason the older companies are approaching the matter in a conservative manner, experimentally determining for themselves the salient features in each instance. In considering a leaching proposition three factors at once fix the attention: (1) disengaging the metal from mineralized forms in Which it is found in nature; (2) recovering the metal in a commercial state after it has been dissolved; (3) the apparatus best adapted to carrying out the several operations.

Jan 8, 1914

By Reed W. Hyde

SOME information has been published on the sulphur dioxide concentration of gases from Dwight-Lloyd machines sintering lead ores but most of this relates to the customary practice in which the charge is relatively high in lead and is sintered in two passes over the machine. It is thought, therefore, that the following observations on sintering in one pass a low-lead, low-sulphur charge may be of interest. The data were obtained in sintering lead sulphide flotation concentrates mixed with minus 20-mesh oxide ore, the mixture carrying 16.8 per cent Pb and 5.3 per cent S. No returns were used because of the limited amount of sulphur available as fuel, but the mixture pelletized readily to make a satisfactorily permeable bed on the sintering machine. As there was a possibility that the SO2 might be utilized, a series of runs was made to determine the concentration of S02 in the gases at different points along the wind box, and the effect on this concentration of changes in the wind-box vacuum. Several runs each were made with vacuums (as measured in inches of water at the wind box) of (1) 2 to 1 1/3 in., (2) 4 to 3 1/2 in. and (3) 6 to 5 1/8 in. The averages of the determinations from each series are platted on the graph (Fig. I). The vertical scale shows the percentage by volume of SO2 (as determined by the Reich method), and the horizontal scale shows the time expressed as percentage of the total sintering time. Sintering was considered to be complete when no S02 could be detected in the gases. In all cases the depth of bed was 4 ½ in. and the weight of dry charge per square foot of hearth area was 45.2 lb. Other data are given in the table. The volume of gases corresponding to the several points along the wind box at which S02 determinations were made could not be measured, but has been calculated from the S02 content and sulphur elimination on the assumption that the volume is uniform throughout the sintering period. This is not strictly true, as with a given vacuum the volume will usually drop slightly toward the middle of the period and increase toward the end. However, this assumption is a reasonable approximation. Several interesting features are brought out by these data. In general, the published data on S02 concentration in sintering under ordinary conditions show a high S02 concentration in the early stages followed by a rapid decrease in concentration and with relatively little SO2 in the gases from the last half or third of the operation. In other words, the greater part of the sulphur elimination is obtained in the first third or half of the period. In these runs, the 6-in. vacuum, which approximates the usual operating condition, gives a curve that follows this customary pattern. Maximum S02 concentration is obtained 2 ½ min. after

Jan 1, 1942

By A. C. Halferdahl

DURING a study of reactions involving iron sulfides, it became desirable to know approxi-mately the heat of decomposition of pyrite. The values given for the heats of formation of pyrite and ferrous sulfide are 35,500 calories and 23,070 calories respectively. For the reaction 2FeS2= 2FeS+S:, the heat effect would be-24,860 calories. But pyrite gives sulfur and pyrrhotite upon heating and the latter is a solid solution of sulfur in ferrous sulfide. The only meas-urements of this decomposition are those of Allen and Lombard1 of the Geophysical Laboratory who have measured dissociation pressures of both covellite and pyrite and have carefully reviewed the literature. They give a table of values for covellite as determined by Preuner and Brockmoller2 and by Wasjuchnowa3 and compare these values with their own measurements. The conclusion is that the measurements of Preuner and Brockmoller are seriously in error, while Was-juchnowa's values fit in well with those of Allen and Lombard. Wasjuchnowa's measurements were made by a dynamic method, while Allen and Lombard em-plowed a static method on both covellite and pyrite. Tables I and II reproduce the measurements of Wasjuchnowa and of Lombard and Allen on covellite and pyrite.

Jan 11, 1927

By Reed W. Hyde

SOME information has been published on the sulphur dioxide concentration of gases from Dwight-Lloyd machines sintering lead ores but most of this relates to the customary practice in which the charge is relatively high in lead and is sintered in two passes over the machine. It is thought, therefore, that the following observations on sintering in one pass a low-lead, low-sulphur charge may be of interest. The data were obtained in sintering lead sulphide flotation concentrates mixed with minus 20-mesh oxide ore, the mixture carrying 16.8 per cent Pb and 5.3 per cent S. No returns were used because of the limited amount of sulphur available as fuel, but the mixture pelletized readily to make a satisfactorily permeable bed on the sintering machine. As there was a possibility that the SO2 might be utilized, a series of runs was made to determine the concentration of SO2 in the gases at different points along the wind box, and the effect on this concentration of changes in the wind-box vacuum. Several runs each were made with vacuums (as measured in inches of water at the wind box) of (1) 2 to 1 3/4 in., (2) 4 to 3 1/2 in. and (3) 6 to 5 1/8 in. The averages of the determinations from each series are platted on the graph (Fig. I). The vertical scale shows the percentage by volume of SO2 (as determined by the Reich method), and the horizontal scale shows the time expressed as percentage of the total sintering time. Sintering was considered to be complete when no SO2 could be detected in the gases. In all cases the depth of bed was 4 1/2 in. and the weight of dry charge per square foot of hearth area was 45.2 lb. Other data are given in the table. The volume of gases corresponding to the several points along the wind box at which SO2 determinations were made could not be measured, but has been calculated from the SO2 content and sulphur elimination on the assumption that the volume is uniform throughout the sintering period. This is not strictly true, as with a given vacuum the volume will usually drop slightly toward the middle of the period and increase toward the end. However, this assumption is a reasonable approximation. Several interesting features are brought out by these data. In general, the published data on SO2 concentration in sintering under ordinary conditions show a high SO2 concentration in the early stages followed by a rapid decrease in concentration and with relatively little SO2 in the gases from the last half or third of the operation. In other words, the greater part of the sulphur elimination is obtained in the first third or half of the period. In these runs, the 6-in. vacuum, which approximates the usual operating condition, gives a curve that follows this customary pattern. Maximum SO2 concentration is obtained 2 ½ min. after

Jan 1, 1942

By David White

Attention has been given to the sources and supply of the raw vegetal matter and the conditions of its submission to the process of sedimentation. An original and most valuable review has been made of the more important or significant chemical compounds originally contained in the organic dct,ris, and of the biochemical changes undergone by the latter during deposition. Consideration also has been given to the factors controlling the selective biochemical decomposition, in whole or in part, of this debris, and the deposition, as sediments, of the undecom-posed plant structures and compounds, together with more or less of the so-called "ulmic," or "humic," organic decomposition products in colloidal so1ution. Biochemical Changes End in Peat Formation The biochemical process terminates in the peat stage of coal formation, and with the cessation of this process organic sedimentation is completed. All subsequent changes result from geological causes and conditions. The deposits are in the form of peats of different types, organic muds, oozes, etc. They are essentially uncompressed and are wholly uncon-solidated, and their water content is great, amounting to over 85 per cent, near the surface of the deposit. Many of the chemical compounds remain as in the once living organisms; others are biochemically broken down and new ones formed. Geochemical and Geophysical Changes in Buried Deposits Subsequent Changes " Dynamochemical" The changes which subsequently take place through dehydration, lithification, and simultaneous progressive chemical alteration, by which organic sediments are advanced to brown lignite, subbituminous, bituminous, semianthracitic, and graphitic ranks, are geochemical and geophysical, and the process, which really is metamorphic,2 takes place under dynamic influences. In fact, the essential changes, including loading,

Jan 1, 1925

By C. E. Lundin

The Ce-H system was investigated in the temperature range, 573° to 1023°K, and the pressure range, 10-3 to 630 Torr, as a function of 'composition up to 72 at. pct H. Families of isothermal arid isopleth curves were plotted from the pressure-terr~perature-composition relationships. From these curves the solubility relationships were determined for the system. The isopleths are analytically represented by equilibrium dissociation pressure equations. The relative partial molal enthalpzes and entropies of solution of hydvogen in the systerrz were calculated fronz the dissociation pressure equulions and are tabulated. The integral free energies, enthalpies, and entropies of mixing in the Ce-H system were determined from the relative partial quantities and are also tabulated. The standard free energy, enthelpy, and entvopy of reaction of the dihydride phase at kcal per kcal per mole H2, and ?S° = -34. 1 cal per deg mole H2, respectively. The equilibrium dissociation pressure equation in the two-phase region is: UNTIL recently very little was known of the detailed solubility and thermodynamic relationships of the Ce-H system. Two previous investigations1,2 are noteworthy. However, significant discrepancies and omissions exist on analyzing them. The work of Mulford and Holley1 on cerium did not clearly delineate the boundaries of the two-phase region, Cess - CeH2-x. The plateau partial pressures were not thoroughly defined and were considerably displaced in pressure compared to those from the work of Warf and Korst.2 These latter authors concentrated their studies primarily from 823° to 1023°K in the pressure range of 1 to 760 Torr. No data were determined to outline the regions of primary solid solubility and the hydride phase. Also the establishment of the plateau partial pressures was rather limited in scope. In neither work was a treatment conducted of the relative partial molal enthalpies and entropies of solution of hydrogen in the single-phase regions and the integral thermodynamic quantities of mixing throughout the system. Therefore, it was the objective of this research to determine the complete equilibrium solubility relationships and thermodynamic data for the system by pressure-temperature-composition studies. EXPERIMENTAL PROCEDURE The cerium metal for this study was donated by the Reno Metallurgy Research Center of the Bureau of Mines. Total impurity content was 0.13 pct with only 60 ppm O. The metal was checked metallographically and contained only minor amounts of second phase compared to cerium from other sources. Specimen preparation was done in a dry box flushed with argon gas. The surface of a small rectangular piece of cerium (about 0.2 g) was filed with a clean, mill file. Final weighing was done in a tared enclosed vial containing argon gas. The specimen was then loaded quickly into the reaction chamber which was purged several times with high-purity hydrogen gas and then allowed to pump to about 10-6 Torr. The furnace was heated to the reaction temperature and the run started. The equipment used to conduct the hydriding was a Sievert's-type apparatus. Basically it consisted of a source for pure hydrogen, a precision gas-measuring burette, a heated reaction chamber, a McLeod gage, and a mercury manometer. Pure hydrogen was supplied by the thermal decomposition of uranium hydride. The 100-ml precision gas burette was graduated to 0.1-ml divisions and was used to measure the quantity of gas and admit it to the chamber. The reaction chamber was a quartz tube. Prior to each run, the cerium specimen was wrapped in a tungsten foil capsule to prevent reaction of the cerium with the quartz. Control of the temperature was achieved within ±1°K. Pressures in the manometer range were measured to ±0.5 Torr and in the McLeod range (10-3 to 5 Torr) to ±3 pct. The compositions of hydrogen in cerium were calculated in terms of hydrogen to cerium atomic ratio. These compositions were estimated to be ±0.01 H/Ce ratio. The technique used to study the equilibrium pressure-temperature-composition relationships of the Ce-H system was to develop experimentally a family of isothermal curves of composition vs pressure. The range of pressure through which each isotherm was developed was from 10-9 to about 630 Torr in the temperature interval, 573° to 1023°K. RESULTS AND DISCUSSION The hydriding characteristics of cerium are iso-morphous with those of the elements of the light-rare-earth group (lanthanum, cerium, praseodymium, and neodymium) wherein the region from the dihydride to trihydride is continuously single phase.' The structure of this phase is fcc.3 The heavy rare earths form a trihydride,2 which is hcp, separated by a two-phase region from the fcc dihydride phase. The Ce-H system is represented by the family of experimental isotherms in Fig. 1. Due to the small scale required to draw the curves, the experimental points are omitted; however, a total of 240 experimental data points were taken to prepare these curves. The solubility relationships can be deduced therefrom. Three distinct regions of partial pressure and composition can be seen. The region of cerium solid solution is represented by the rapidly rising isotherms in the dilute composition range. In accordance with Gibbs Phase Rule only one solid phase, the cerium solid so-

Jan 1, 1967