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By Gordon V. lewis

The Penjom gold mine treats highly preg-robbing carbonaceous ore by using relatively inexpensive gravity and hydrometallurgical methods. The mine is a joint venture between Avocet Gold Limited, a subsidiary of Avocet Mining PLC, a U.K listed mining company with interests in gold and tungsten, and the Pahang State Development Corporation (PKNP) who receive a 2% royalty. The operating team at Penjom embarked on a programme of innovation during 1998 following a realisation that almost all of the primary ore in the gold deposit was highly carbonaceous in nature. Earlier attempts at desliming and leaching the deslimed product through a normal CIL circuit had failed, and through shear necessity, the team turned to new technologies which were considered most suited to the ore characteristics indicated from pre­feasibility testwork. Between April and September, 1998, the mine introduced three key processes, which combined represent the elements of "The Penjom Process". The gravity circuit was boosted to maximise the capture of leachable sulphide and free gold from the relatively carbon free cyclone underflow stream, kerosene and diesel blanking was introduced to treat the cyclone overflow and RIL (resin-in­leach) technology utilised to replace the existing CIL (carbon-in-leach) circuit. Further experimentation with selective resin in partnership with Mintek of South Africa yielded a significant improvement to the process during 1999. Minix­Dowex resin was introduced mid year to replace a non-gold selective resin, which had been used in a flotation/batch leaching circuit for about nine months. Lower carbon levels in the feed at that stage led to the abandonment of flotation and the introduction of continuous RIL, which has been adopted as the major chemical process at the Penjom gold mine since September, 1999. Given the proven performance of the circuit to date, this process may be considered as a low cost option for the treatment of highly carbonaceous ores, particularly those which are not refractory and contain a reasonable percentage of free gold.

Jan 1, 2000

By R. W. Heins, N. Street

Recently Hiller1 reported results on the impairment of the strength of quartz glass rods through wetting, indicating that there was general agreement with the prediction of the Griffith formula in that for the liquids used the rods were weakest in water i.e. the liquid which probably had the greatest free energy of immersion. The Griffith equation predicts that the tensile stress necessary to propagate a crack of length c is where ? is the interfacial free energy, E Young's modulus. Since for a solid immersed in a liquid of surface tension ?L and contact angle 8 at the solid-liquid-gas contact, ?s - ?SL = ?L cos ? where ?s is the surface free energy of the solid. Hence comparison between ?L cos 0 and strength impairment should be possible. In a study of the usefulness of the Kuznetsov pendulum2 as a means of studying rock drillability we have determined the effects of various liquids on the pendulum hardness of Bavarian limestone. The pendulum used had diamond points (Burgess Vibro-graver), a period of 1.14 sec and a total on sample weight of 1191 g. The decline of the pendulum oscillations was recorded by a light beam on light sensitive paper carried on a kymograph. Rehbinder's expression relating hardness to amplitude attenuation as a function of time can be written In A = - (1/H) t + In Ao where A, A, = amplitude at time t and initial amplitude respectively, H = hardness parameter, and t = time. The line of best fit to the experimental points was determined using the IBM 7090 electronic computer, the computer also gave A, by extrapolation to zero time. The results for the various liquids tested are given in Table I and Fig. 1. The limestone surfaces were highly polished before testing and each reported hardness value represents the average of at least ten separate determinations of the pendulum decline curve. On each newly prepared surface the water value was again determined (also

Jan 1, 1964

State of Indiana, Department of Conservation, Division of Geology, Indianapolis, Ind. W. N Logan, State Geologist A list of the publications will be sent upon request. A series of yearly reports have been issued, with a few early exceptions, since 1869, up to and including the 41st (1916) Five of these are issued free, 18 are out of print, and the rest may be obtained at a quoted price. Beginning in 1917, the administrative reports of the State Geologist have been published in the Indiana Year Book. In 1919, the Department of Geology and Natural Resources became the Division of Geology in the Department of Conservation and separates of later reports in the Year Book are available, as follows. 3rd Report (1921), Gold in Indiana, 4th (1922), The New Albany shale, peat deposits of Indiana; 5th (1923), Petroleum conserva¬tion, 6th (1924), Conservation of natural gas; 7th (1925), Coal losses of Indiana, 10th (1928), Geological conditions in the Siosi oil field, 11th (1929), The mineral fuel resources of Indiana, 12th (1930), Oil and gas developments in 1930. (Titles of lesser interest are omitted ) The following Special Reports have been printed as publications of the Department of Conservation: Special Report 6, Kaolin of Indiana (1919), free; 21, Handbook of Indiana geology (1922), $5 to nonresidents and $3 to residents, 42, Geologic conditions in the oil fields of southwestern Indiana (1924), 75 cents to non-residents and 50 cents to residents; 55, Geology of the deep wells of Indiana (1926), $1; 75, Geology of the Silurian rocks of northern Indiana (1928), $1, cloth bound, 8125, 78, Indiana oolitic limestone map of Monroe-Owens counties (1928), $1, 79, Indiana oohtic limestone map of Lawrence County (1928), $1; 90, The geologic history of the vertebrates of Indiana (1929), $1, cloth bound, $125, 91, The ceramic materials of Indiana (1929), free, 98, The Borden (Knobstone) rocks of southern Indiana (1931), $1 25, cloth bound, $150, 101, Insoluble residue studies of Mississippian limestones in Indiana (1931), 25 cents

Jan 1, 1933

By H. R. Page, A. E. Jr Lee

A. E. LEE, JR. (author)—In addition to the paper we should like to make a few remarks. First, the seriousness of bending of the clay retort cannot be overemphasized. Not only did bending limit the length of the vessel, but it permitted corrosive fluid slags to concentrate in the belly of the retort and thus increased the possibility of boring. Bending also practically prohibited the use of cleanout machines and increased the danger of excessive fume losses by allowing furnace gases to escape around the top of the retort mouth. It will be noted that the Blackwell pottery practice places considerable emphasis on careful drying of retorts. Perhaps it is another smelter superstition, but traditionally the aging of retorts beyond a reasonable drying period has been considered important to long life. We are unable to give a good explanation of why aging should improve retorts. During the past fall in an attempt to prove a theory that the combined water in the clay decreased during aging, about 50 samples of wet retort collars were placed in a dry room when it was closed. Loss of weight, combined water and free moisture were measured each week over the 100 day drying period. The affinity of the dried retort for moisture makes difficult the accurate measurement of free water; however, there was a clearly defined free moisture change from about 12.5 pct when freshly made to about 2 pet at the end of 18 days, then a gradual loss to about 0.25 pet at 70 days and an apparent equilibrium near this figure through the 100th day. There was no appreciable change in the combined water. The change in weight of the average sample was, however, rather unusual, there being consistently a loss of weight throughout the entire 100 days. From the 63rd day on this leveled off to about 0.03 pet per week. These were small samples and certainly should have dried

Jan 1, 1950

By Ernest Darby

WHEN bronze is melted in open-flame furnaces a considerable amount of slag is formed during the melting operation. This slag may be incidental to the melting practice or it may be formed intentionally by slag-forming constituents added to the furnace charge to provide a covering for the melted metal. When this slag is removed from the furnace, it contains, in addition to the free metal carried with it by the skimming operation, a considerable amount of metal as oxide either combined or mechanically mixed with it. By the usual crushing and washing methods this metallic oxide generally goes to the tailings pile, so diluted by other foundry waste that its recovery is economically impossible. If this furnace slag is not mixed with other foundry waste, practically all of the metal oxide as well as the free metal may be recovered by some form of smelting operation. The first side of the problem to be considered is the amount of slag produced. It may not be true that the majority of foundries have no record of the amount of slag made, but it is certainly true that a very great many either have no record or pay little attention to it. Usually the collection of furnace slag for one normal week's run will be sufficient to determine the advisability of its being handled in a different manner from the crushing and concentrating generally employed. If a large representative sample of the accumulation is crushed and concentrated and the recovery compared with the results of a careful assay, it will be found that a large percentage of the total metal content was lost in the washing process. The percentage of loss will be greater than the metallic oxide content, as some free metal in extremely fine particles always is carried away in grains of slag. From such a comparison, it may be determined whether or not the slag should be melted, sold or treated as before. An example of an actual test of this kind is given below.

Jan 1, 1928

By Ionel Gardescu

IN connection with some of the experiments carried out by the writer on the behavior of gas and oil in a sand reservoir,1 an interesting phenomenon was observed which may throw some new light on the problem of recovery of oil from a natural reservoir. The experiments are intended to show the effect of the surface area of the occluded gas masses, originally present in a reservoir, on the further evolution of gas from the oil and its consequent effect upon the rate of production of oil. The apparatus used in the experimental work is shown in Fig. 1. It consists primarily of a sand reservoir R and a displacement chamber D, which is used to induce small variations in volume. The reservoir and displacement chamber form a unit, and a lowering of the plunger D is equivalent to increasing the volume occupied by the oil and gas in the reservoir. The reservoir was first filled with dead oil and maintained under pressure until it was ascertained that most of the free gas had gone into solution. The volume of free gas present in the reservoir was computed from the coefficient of compressibility of the fluids by means of the dis-placement chamber D, reading to 0.005 c.c. and a special gage J reading to 0.02 lb. per sq. in. The oil was saturated with gas under pressure in reservoir S by circulating the oil for a long period of time through the gear pump B. Subsequently, the saturated oil was circulated through the sand reservoir following the circuit S6, B, S5, R4, the sand reservoir R, R1, R2, F4, F1, back to reservoir S. In the following experiments the sand reservoir R was filled with gas-saturated oil at a pressure of 415 lb. per sq. in. with no free gas present. This was ascertained by. closing off all the outlet valves, and determining the coefficient of compressibility of the system by means of the dis-placement chamber D.

Jan 1, 1932

By M. A. Rigdon, R. E. Grace

The dissociation of cupric oxide to cuprous oxide and oxygen was studied with a microbalmce technique at 700" to 750°C. In this temperature range the dissociation pressure of the reaction 2CuO= Cu2O + 1/2 O2 was: The theory of near-equilibriwm reaction rates predicts a linear relationship between reaction rate and the Gibbs free-energy change for small values of AF/RT. This correlation is found to be valid for AF/RT = -0.1 or approximately 200 cal per mole away from equilibrium. THE theory of reaction rates near equilibrium as developed from classical thermodynamics suggests a small range of linear behavior between the overall reaction rate and the free-energy change accompanying the process. The extent of this linear correlation is generally unknown, even to the order of magnitude. The idea of linearity is also found in the formal mathematics of coupled transport phenomena, e.g., chemical diffusion, thermal diffusion, thermoelectricity, and so forth. The linear array of forces and fluxes which leads to various main and cross coefficients is predicated upon linearity between reaction rates and the bulk thermodynamics which govern the process. The general case in reaction kinetics is well-known: the magnitude of the free-energy change does not cor- relate with observed reaction kinetics, irrespective of whether the process occurs by diffusion or chemical reaction or both. The real need is to investigate specific reaction paths near equilibrium in order to learn of the limitations in attempting to correlate reaction rates and thermodynamics. It is the main purpose of this paper to examine the dissociation kinetics of cupric oxide under conditions of known driving force where the dissociation process is likely to occur by chemical reaction. A secondary objective is to obtain equilibrium data for the CuO-Cu20-O2 system. In a prior paper Edmiston and race' investigated reduction kinetics of wustite in H2-H2O gas mixtures. The present study was carried out in oxygen according to the following reaction:

Jan 1, 1969

By Ernest Darby

WHEN bronze is melted in open-flame furnaces a considerable amount of slag is formed during the melting operation. This slag may be incidental to the melting practice or it may be formed intentionally by slag-forming constituents added to the furnace charge to provide a covering for the melted metal. When this slag is removed from the furnace, it contains, in addition to the free metal carried with it by the skimming operation, a considerable amount of metal as oxide either combined or mechanically mixed with it. By the usual crushing and washing methods this metallic oxide generally goes to the tailings pile, so diluted by other foundry waste that its recovery is economically impossible. If this furnace slag is not mixed with other foundry waste, practically all of the metal oxide as well as the free metal may be recovered by some form of smelting operation. The first side of the problem to be considered is the amount of slag produced. It may not be true that the majority of foundries have no record of the amount of slag made, but it is certainly true that a very great many either have no record or pay little attention to it. Usually the collection of furnace slag for one normal week's run will be sufficient to determine the advisability of its being handled in a different manner from the crushing and concentrating generally employed. If a large representative sample of the accumulation is crushed and concentrated and the recovery compared with the results of a careful assay, it will be found that a large percentage of the total metal content was lost in the washing process. The percentage of loss will be greater than the metallic oxide content, as some free metal in extremely fine particles always is carried away in grains of slag: From such a comparison, it may be determined whether or not the slag should be melted, sold or treated as before. An example of an actual test of this kind is given below.

Jan 1, 1928

By N. H. Murlenberg, T. M. Drown

It is often a tedious matter to get a solution of pig iron or steel, for the determination of phosphorus, which is absolutely free from silica. Where pig iron rich in silicon is dissolved in hydrochloric or nitric acid in the usual procedure, it is necessary, not only to evaporate the solution to complete dry ness, but to heat the dry residue for some beam in an air-bath to a temperature of about 120° C. The oxide of iron is thus rendered insoluble in nitric acid, and is only slowly dissolved by hydrochloric acid. In the method of determining silicon by nitric and sulphuric acid, described in the Transactions of the Institute, Vol. VII, page 346, arid Vol. VIII, page 508, we obtain in one or two hours a solution of the iron in the form of ferric sulphate entirely free from silica, and containing free sulphuric acid. It occurred to Us that this solution might be made available for the determination of the phosphorus by the molybdate method. The following experiments mere tried with unsatisfactory results. 1st. The iron was precipitated by ammonia, the precipitate filtered, washed, and dissolved in nitric acid. 2d. The iron was precipitated as basic acetate and dissolved in nitric acid. 3d. The solution was neutralized by ammonia, and nitric acid added in small excess. In all these cases the phosphorus obtained by precipitating by ammonium molybdate and magnesia-mixture was too low. The following method was then tried with success. The filtrate from the silica and graphite was evaporated to small bulk and heated in a porcelain dish on a sand-bath. until fumes of sulphuric acid ceased to escape. The dry residue was taken up with dilute nitric acid and the solution precipitated by ammonium molyldate. The phosphorus was weighed as magnesium pyrophosphate. The results were satisfactory. To save time, the original solution of the iron in nitric and sulphuric acids was evaporated to dryness and heated as before until

Jan 1, 1882

By N. H. Muhlenberg

IT is often a tedious matter to get a solution of pig iron or steel, for the determination of phosphorus, which is absolutely free from silica. Where pig iron rich in silicon is dissolved in hydrochloric or nitric acid in the usual procedure, it is necessary, not only to evaporate the solution to complete dryness, but to heat the dry residue for some hours in an air-bath to a temperature of about 120° C. The oxide of iron is thus rendered insoluble in nitric acid, and is only slowly dissolved by hydrochloric acid. In the method of determining silicon by nitric and sulphuric acid, described in the Transactions of the Institute, Vol. VII, page 346, and Vol. VIII, page 508, we obtain in one or two hours a solution of the iron in the form of ferric sulphate entirely free from silica, and containing free sulphuric acid. It occurred to us that this solution might be made available for the determination of the phosphorus by the molybdate method. The following experiments were tried with unsatisfactory results. 1st. The iron was precipitated by ammonia, the precipitate filtered, washed, and dissolved in nitric acid. 2d. The iron was precipitated as basic acetate and dissolved in nitric acid. 3d. The solution was neutralized by ammonia, and nitric acid added in small excess. In all these cases the phosphorus obtained by precipitating by ammonium molybdate and magnesia-mixture was too low. The following method was then tried with success. The filtrate from the silica and graphite was evaporated to small bulk and heated in a porcelain dish on a sand-bath, until fumes of sulphuric acid ceased to escape. The dry residue was taken up with dilute nitric acid and the solution precipitated by ammonium molyhdate. The phosphorus was weighed as magnesium pyrophosphate. The results were satisfactory. To save time, the original solution of the iron in nitric and sulphuric acids was evaporated to dryness and heated as before until

Jan 1, 1882

By C. F. Austin, J. K. Pringle

In view of the many large differences in structure and physical properties between metals, plastics, and most rock materials, a continuing experimental petrodynamics program has been established at the U. S. Naval Ordnance Test Station. Part of this program has been to test the concepts of scabbing and corner fracturing in a typical coarse-grained rock. The results of this experimental program have shown very interesting differences between the formation of fractures in rock and the formation of fractures in other materials such as metals and plastics which are often used as models for rock behavior studies. The gross behavior of coarse-grained brittle solids subjected to impulsive loading has undergone abundant empirical investigation by mining organizations and by mineral research agencies. However, the fundamental response of coarse-grained brittle solids to impulsive loading has received little detailed study in recent years. The various organizations and agencies interested in rock-like brittle materials have broadly applied the stress wave interaction concepts of the impulsive failure of metallic samples to the behavior of granular brittle materials 1,2,3,4,5,6 Using the metallic sample approach for stress wave induced fracturing, an understanding of the fracture behavior of brittle materials which perhaps is not always appropriate has been established in the open literature. An excellent summary of the metallic sample approach is provided by ref. 7 which summarizes the general beliefs prevalent at present regarding the impulsive behavior of brittle solids: "In the blasting process, rock breakage occurs primarily from tensile slabbing, beginning at a free face and proceeding back toward the explosive charge. The tensile waves formed by the reflection of incident compressive waves from two or more free faces will collide in the rock, resulting in large localized tensile stresses. Fractures formed by the interaction of these tensile stresses begin at the apex of the free face planes and progress back into the rock as shown...."

Jan 1, 1964

By J. M. Steininger

The mechanism of flotation of sphalerite with sulthydryl compounds of different acidities has been interpreted in terms of chemisorption of unionized collector molecules on hydroxylated zinc surface sites. At a constant collector concentration of 1.5 x 10 -4 M, the upper pH limit of flotation has been found to be directly and closely related to the negative logarithm of the collector acidity constant, pKa The experimental results indicate that flotation is prevented when about 95% of the collector is ionized. At low pH, collector adsorption decreases because of the reduction in number of hydroxylated zinc surface sites. These two effects explain why sphalerite does not float with the more acidic sulfhydryl compounds. Typical anionic collectors for sulfide minerals are short chain xanthates or dithiophosphates which are nearly completely ionized in the generally alka- line flotation circuits.1,2 Flotation mechanisms have therefore been usually interpreted in terms of ionic collector adsorption and competition with ionic depressants of the same sign as the collector. A few attempts have been made, however, to consider adsorption of neutral collector molecules. Contact angle measurements obtained by Wark and cox3 have been interpreted by Cook and Nixon4 as representing adsorption of the free acid molecules on sulfide minerals such as pyrite, galena, chalcopyrite, and sphalerite. Cook and Nixon tried to show that the free acid concentration of the collector was substantially constant along the curves relating collector addition and minimum pH for bubble adherence. However, in a review of the subject,5 Sutherland presented new data on the flotation of pyrite with mercaptobenzothiazole which did not support the hypothesis of constant concentration of either collector ions or collector free molecules. He further showed that, with the assumption of constant occupation of surface sites, both theories lead to relations between pH and collector addition having similar mathematical expressions. In fact, with the more likely assumption of variable occupation of surface sites which results in more complex relationships, it appears impossible to

Jan 1, 1968

By Anson G. Betts

A solution of lead-fluosilicate, containing an excess of fluosilicic acid, has been found to work very satisfactorily as an electrolyte for refining lead. It conducts the current well, iseasily handled and stored, non-volatile and stable under electrolysis, may be made to contain a considerable amount of dissolved lead, and is easily prepared from inexpensive materials. It possesses, however, in common with other lead electrolytes, the defect of yielding a deposit of lead lacking in solidity, which grows in crystalline branches toward the anodes, causing short circuits. But if a reducing-action (practically accomplished by the addition of gelatine or glue) be given to the solution, a perfectly solid and dense deposit is obtained, having very nearly the same structure as electrolytically-deposited copper, and a specific gravity of about 11.36—that of cast-lead. Lead-fluosilicate may be crystallized in very soluble, brilliant crystals, resembling those of lead-nitrate and containing four molecules of water of crystallization, with the formula PbSiF,,4H20. This salt dissolves at 150 C. in 28 per cent. of its weight of water, making a sirupy solution of 2.38 sp. gr. Heated to 60° C., it melts in its water of crystallization. A neutral solution of lead-fluosilicate is partially decomposed on heating, with the formation of a basic insoluble salt and free fluosilicic acid, which keeps the rest of the salt in solution. This decomposition ends when the solution contains, perhaps, 2 per cent. of free acid; and the solution may then be evaporated without further decomposition. The solutioi~s desired for refining are not liable to this decomposition, since they contain much more than 2 per cent. of free acid. The electrical conductivity depends mainly on the acidity of the solution. My first experiments were carried out without the addition of gelatine to the fluosilicate solution. The lead-deposit con-

Jan 1, 1904

By George S. Evans

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

Jan 1, 1938

By George S. Evans

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

Jan 1, 1938

By C. H. P. Lupis, R. Hocine, G. Bernard

The necessary and sufficient conditions for the stability of a multicomponent phase with respect to infinitesinzal fluctuations are derived and transformed to be written in terms of activity coeffcients and mole fractions rather than in terms of the customary second deritlatives of the free energy. NECESSARY conditions for the stability of a multi-component system were derived by Gibbs as early as 1876.' However, as the usefulness of these conditions is greatly enhanced by the simplicity of their translation in terms of functions of common usage, the present contribution establishes these conditions in terms of activities or activity coefficients-and mole fractions. It was shown in another article2 that not only may these conditions be used for the prediction of the appearance of new phases, but they may also provide a check on the orders of magnitude of the interaction coefficients involved. "Spinodal" decomposition is said to occur when, at constant temperature and pressure, the system is unstable with respect to infinitesimal fluctuations in composition. As a result, the "phases" which appear may be attained through continuous changes in the system rather than discontinuous ones, and, consequently, the free energy of these phases may be described by a unique continuous free-energy function. For a binary system, the familiar curve of Fig. 1 illustrates the case we wish to extend to a multicom-ponent system. The conditions to be written pertain to the decomposition of a system of n moles into moles of phase moles of phase v, ...hen moles of phase 9, where the phases a, ...v, ...9 are—at least initially-arbitrarily close in composition to that of the original phase. Each A, is positive and since the total number of moles n in the system remains constant: Each phase v contains hv(nl +dnY) moles of component (I), ...xV(ni +dny) of component + dnk) moles of component (m). The total number of moles ni in the system remaining also constant, it is clear that:

Jan 1, 1968

By R. D. Pehlke, J. F. Elliott

The equilibrium pressure of nitrogen gas over pure silicon metal and silicon nitride has been measured in the temperature range 1400° to 1700°C. From the experimental data, the standard free energies and enthalpies of formation of Si3N4(a) have been calculated as functions of temperature over the above temperature range. Utilizing data in the literature and the results of this investigation, the specific heat, molar enthalpy, molar entropy, standard enthalpy of fornation, and standard free energy of fornation are estimated for the temperature range 298° to 1400°C. THE high-temperature thermodynamic properties of many metallic nitrides are not well established at present. This is a serious deficiency because nitrogen and nitride-forming metals are important alloying additions to steels, and knowledge of the interaction between nitrogen and these elements is essential to a better understanding of the behavior of steels. Metallic nitrides also are used as refractory materials. Consequently, the investigation reported here was undertaken to provide more complete information on the standard entropy and free energy of formation of silicon nitride. The experimental technique provided a direct measurement of the equilibrium pressure of nitrogen gas in the range of 1413 to 1700°C for the reaction: 3 Si(1) + 2N2 (g) = Si3N4 (a) [ 1 ] and below 1413oC for the reaction: 3Si(c) + 2N2(g) = Si3N4(a) [2] APPARATUS The experimental system consisted of a crucible assembly, a reaction chamber, and a gas supply and vacuum system. The Crucible Assembly which contained the equilibration specimen and molybdenum radiation shields with a susceptor for induction heating is shown in Fig. 1. Two covered, high-purity alumina crucibles, one nested within the other, contained the susceptor, shields and specimen. Central openings in the upper shield and crucible covers permitted on optical pyrometer to be sighted into the central cavity of the specimen. The specimen itself was a 5/8 OD by 1-in.

Jan 1, 1960

By George S. Evans

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

Jan 1, 1938

By I. E. Odom

An electron optical and microprobe study was made to determine the physical and chemical nature of the silica minerals that occur as natural impurities in bentonite and montmorillonitic fuller&apos;s earth clay products (both granular and powder) and that occur in <10-µm dusts from plants that process these products. The purpose of the study was to determine if discrete "free" silica minerals, such as quartz, could be observed using SEM and EDS methods. No “free" silica minerals could be observed in the SEM images of the granular and powdered products, either among or on the surfaces of the particles. Also, no “free" silica could be identified by either SEM or EDS analyses of the dusts, even though quantitative X-ray diffraction analysis indicated that trace amounts of quartz occurred in all samples. It was determined that these quartz and other silica minerals were encapsulated or coated by montmorillonite. Vigorous washing, however, removed some of the clay coatings, so that small amounts of silica minerals could be seen by SEM and EDS analysis. It was found that all primary crystalline quartz grains in the bentonites have diagenetic overgrowths consisting of a mixture of montmorillonite, opaline silica and possibly microcrystalline quartz. Detrital quartz grains in the fuller&apos;s earth have thin diagenetic overgrowths of opaline silica, also containing montmorillonite. The clay encapsulation of the silica minerals in the products studied, as well as in the potentially respirable (<10-µm) dust produced during manufacturing of bentonite and montmorillonitic fuller&apos;s earth clay products, is considered to be an important factor influencing the potential health effects (e.g.. silicosis) of the contained silica. Even if clay dust containing silica should be inhaled, the montmorillonite encapsulating the quartz and other silica minerals would prevent direct contact of the silica with lung tissue. The clay encapsulation of quartz, as well as the highly hydroscopic nature of montmorillonite, may explain why not a single confirmed case of silicosis has ever been reported among plant workers in more than 65 years of production.

Jan 1, 1998

By Gökhan Çevikbilen, Ümit Karadoğan, Sevde Korkut, Berrak Teymur

This study proposes a methodology for dewatering of mine waste using a multistage process, combining geotextile tubes and anionic polyacrylamide (PAM), which accelerates the recycling process of water for aggregate mine waste facilities. For this purpose, waste from a rock quarry located in Istanbul was investigated. Flocculation tests revealed that the use of anionic PAM at an optimum dosage reduced sedimentation time and decreased turbidity. The compatibility of geotextiles and mine waste conditioned with different dosages of the effective PAM was evaluated by rapid dewatering tests, considering the water content of the filter cake, amount of infiltrated solid content, and rate of filtration. Geotextile dewatering tests were also performed on PAM-free and conditioned suspensions. The dewatering process was optimized by the use of a geotextile tube in two stages: (i) on the unconditioned suspension and (ii) on recovered PAM-conditioned leachate. Directing PAM-free non-hazardous soil-based material obtained in stage i to alternative beneficial uses is suggested, to minimize the volume of waste. Furthermore, recycling of the effluent obtained at the second stage of the proposed method will ensure more efficient water reuse

Sep 29, 2022