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By Richard H. Olson, Lawrence A. Roe

Talc, when it can be isolated as a pure mineral, has a composition of 63.36% Si02, 31.89% MgO, and 4.75% H20. However, as an industrial commodity, talc rarely approaches theoretical purity. Nevertheless, the impure talc products of commerce find a multitude of uses and few substitutes in many industrial applications. Minerals commonly associated with and sold together in talcose mixtures are tremolite, chlorite, dolomite, mica, and magnesite. Steatite was originally a mineralogical name applied to pure talc. In today's commerce steatite generally refers to the massive variety of talc suitable for electrical insulator manufacture. Block steatite ore can be machined into various shapes. Impure varieties of massive or block talc are still commonly referred to as soapstone. Soft massive talc, suitable for crayon manufacture, has been referred to as French chalk. It has been common practice to discuss talc, soapstone, and pyrophyllite under the same general heading. In the case of soapstone and talc, this is a natural thing since many different types of platy, soft minerals exhibiting a high degree of lubricity (commonly referred to as "slip") have been grouped together and called soapstone or talc. Further, there is a mineralogical relationship of pyrophyllite to montmorillonite and talc to hectorite. Thus, talc and pyrophyllite are sometimes referred to as clay minerals. When finely divided talc or pyrophyllite are combined with water in proportions to make a slurry, the end product does have the appearance of a clay-water mixture. Soapstone for utensils and ornaments was mined by prehistoric Indians on Santa Catalina Island, CA. In the mid-1800s, soapstone from deposits along the western foothills of the Sierra Nevada mountains was used by white settlers for building and ornamental stone and in the linings and foundations of furnaces (Anon. 1956). Previous to 1916, the annual recorded production in California did not exceed 2000 tons. In the period 1912 to 1918, output rose sharply when the Talc City, Western, and Silver Lake mines were put into operation. From 1916 to 1935, the state's annual output of talc was in the range of 9,000 to 20,000 tons. In the mid-1930s, the use of talc in wall tile grew rapidly. In California, the production of talc grew to 63,000 stpy in 1943. The post-war building boom helped California production to grow to 120,000 tons in 1951. In 1968, production was 165,000 tons, 1969 was 145,000 tons, 1970 was 185,000 tons, and 1972 was 155,000 tons. Talc mining in New York state dates to about 1878 when a Colonel Palmer and associates opened the first commercial talc mine on the Nelson Freeman farm near Talcville, New York. In 1893, this operation was sold to the International Pulp Co. which changed its name to the International Talc Co. in 1944. The company was acquired by R.T. Vanderbilt Co., Inc. in 1974. A new talc operation, the Gouverneur Talc Co. owned by the R.T. Vanderbilt Co., began operations near Balmat, NY, in 1948. The initial capacity of the processing plant was 200 stpd (Gillingham, 1950). Subsequent expansions have increased capacity to over 600 stpd. The Vermont talc industry began just after the start of the 20th century. Talc was discovered in the area of the present Johnson, VT, talc mine in 1902. The American Minerals Co. initiated plant operations at Johnson in 1904. The Magnesia Talc Co. opened a plant at Waterbury, VT, in 1913 (Burmeister, 1963; Trauffer, 1964) and acquired American Minerals Co. in 1923. The Waterbury mine has a long history as a producer of talc crayons. The Eastern Magnesia Talc Co. was formed in 1924 by a merger of the Eastern Talc, Co.

Jan 1, 1983

By Walter S. Weeks

THE process of cooling air by allowing it to expand and do work in an engine is well known, but the theory of obtaining cold air by free expansion without the aid of an engine operating with cutoff has been little discussed. Case 1 If compressed air is allowed to expand to the atmospheric pressure through an orifice in an sir line that is supplied by a running compressor, no cooling results except the negligible one due to the Joule-Thompson effect, which will not be considered in this discussion. The effect of moisture will also be neglected. Symbols P1 Absolute pressure in pipe line, lb. per sq. ft. P3 Atmospheric pressure, lb. per sq. ft. V1 Volume occupied by 1 lb. air in pipe. V3 Volume occupied by 1 lb. air at P3. Cv Specific heat of air at constant volume, B.t.u. per lb. per deg. F. Cp Specific heat at constant pressure, B.t.u. per lb. per deg. F. T1 Absolute temperature of air in pipe, deg. F. T3 Absolute temperature of air outside after expansion and mixing and coming to rest. J Mechanical equivalent of heat (778 ft. lb.) R Gas constant for air, ft-lb. per deg. F. = 53.3. Formulas Consider 1 lb. of air moving out of a pipe. The air behind it does work on it to the extent of P1V1 ft-lb. This work is really done by the thrust of the piston of the compressor and does not come from any energy that exists in the air in the pipe. The pound of air contains

Jan 1, 1937

By Richard D. Mills

Throughout the mining industry, many companies perform sophisticated business and financial analyses of proposed capital investments. However, once the project is approved, it is never reevaluated. At best, there is an attempt to control capital costs and minimize overruns. The post-installation appraisal, a formalized review of investment performance, may prove helpful. Typical Project Review A typical capital investment is approved after business and financial benefits have been reviewed with management.* The financial data shown to management often include a net income statement, cash flow analysis and summary economic data similar to those shown in Table 1 overleaf. These financials report the expected impact of the project on the corporation financial statements. This project is a rudimentary example of a capital investment decision. An actual project would undergo a more sophisticated analysis incorporating depletion benefits, deferred taxes and a detailed cost breakdown. The example project has several financial benefits that could result in management approval. For example, it provides an immediate net income benefit to the company, generates positive cash flows every year of the project life and has a discounted cash flow rate of return of 25 percent. However, it also has the disadvantage of a long payback period. A sensitivity analysis would show which areas of the analysis have the greatest impacts on profitability. Post-Installation Program Objectives The post-installation appraisal goes beyond the analysis shown in Table 1 by comparing actual results to those projected in the original economic analysis. The post-installation program has three primary objectives: 1. To provide a periodic performance review of major spending programs. 2. To review decision-making and evaluation procedures. 3. To provide a means of controlling individual project investments. The first major function of the post-installation program is the periodic review of actual performance of projects and investment programs, identifying those factors which proved critical to the health of investments. This review will serve to keep management abreast of progress, provide a comparison of actual performance against expectations, and provide valuable information that can be used for improving future economics. The second major function of the program is to perform a continuous review of the decision-making process. This includes testing of evaluation procedures, forecasting techniques, and logic used in making decisions. An information system should be set up whereby original evaluations and historical performance data gathered under the appraisal program are documented for use by evaluators and management when assessing past and future investment proposals. Such data should be particularly useful in evaluating new and developing types of operations and in activities where companies repeatedly reinvest. The primary purpose of this feedback system is to sharpen estimates to assure that they are realistic and attainable. The appraisal program also provides assurance that consistent evaluation procedures are being used throughout a company, leading to improved procedures

Jan 1, 1985

By I. N. Zavarine

Austenite is often defined as a solid solution of carbon or carbide in a nonmagnetic form of iron. Conversely, magnetic measurements are often used by investigators for the purpose of detecting the degree of austenite decomposition after an iron alloy has been subjected to certain thermal or mechanical treatments. Association of the magnetic state with the gamma-phase decomposition is often extended to the alloys of iron with elements other than carbon. Definition of austenite as a nonmagnetic solid solution cannot be accepted in the light of available information without certain reservations. The relation of magnetic transformations with the gamma-phase decomposition in the complex alloys of iron has never been rigorously proved. The present investigation deals primarily with the magnetic transformation that occurs in carbon steels during the quenching process. The work was further limited to a study of magnetic transformation in carbon steels quenched at such rates as are necessary to retain the product of austenite decomposition in a martensitic state. Peevious Work Considerable information has accumulated in the literature with respect to the magnetic transformation in alloys of iron, but nearly all of it relates to transformations under the conditions of equilibrium between the phases of the alloy. Earlier studies of Hopkinson,$(') Curie,(2) and Honda'~) are well known. Investigations of the magnetic

Jan 1, 1934

By W. T. Turrall, D. Porter

THE crystal laboratory, Dept. of Physics, Massachusetts Institute of Technology, was confronted with the problem of obtaining a supply of optical grade calcium fluoride (CaF2) for use in growing synthetic CaFe2 crystals. A search of the known fluorspar deposits did not indicate that any quantity of optical spar could be obtained. Even the best material had to be sorted by hand to remove impurities. The process for growing CaF2 crystals developed by Professor D. C. Stockbarger of the Dept. of Physics, M.I.T., necessitates very pure feed materials. Exclusion of impurities is required, even in amounts detectable only spectrographically. The impurities occurred as minute inclusions of SiO2, BaSO4, CaCO3, FeS2, water or air. Crystals up to 4 in. in diam and weighing several pounds are made by the Harshaw Chemical Co. in Cleveland. Since the time required to grow a 4-in. crystal is about one week, and since the cost of manufacture is high, removal of impurities by any concentration method appeared practical. The mineral engineering section of the Dept. of Metallurgy undertook to investigate the possibility of concentrating clear optical fluorspar, -4 mesh +10 mesh, from a feed containing over 99 pct CaF2. Various innovations of the known methods of concentration were considered, but in each case the minute amount of impurities associated with the crystal produced such extremely small differences

Jan 1, 1952

By A. Kenneth Schellinger

DURING the comminution of a brittle material in the presence of dry air, no known phase change or chemical reaction takes place. The energy changes associated with the comminution are those of the transformation of kinetic energy into heat energy and the energy absorption represented by the actual rupture of molecular and/or ionic bonds. The random nature of the actual grinding process in a tumbling-mill often precludes the effective application of a rupture force on each individual particle of brittle mineral present. The result must be a great deal of useless vibration on an atomic scale in both the brittle mineral and the grinding medium below the elastic limit, which vibration is eventually manifested as heat energy in the mill. The actual rupture of molecular, or ionic, bonds creates new surface on the brittle minerals; each square centimeter of this new surface then must possess a number of potential bonds, each of which could reform theoretically with the release of energy. The sum total of this potential energy of bonding per unit of new surface, minus bond satiation effects of the enclosing gas or liquid, must be the surface energy of the mineral. If the comminution of the brittle mineral were carried out within the chamber of a calorimeter, the energy released as heat could be determined rather accurately. Moreover, the total kinetic energy input to the comminuting mass (mineral and medium) conceivably could be derived by a suitable torquemeter and revolution counter if the whole calorimeter were revolved. The difference between these two energy figures should then represent the net energy (gross energy input—heat enerb output) used in creating new surface, gliding or slip on atomic planes, twinning, and possibly other lattice rearrangements within the mineral. If it be postulated further that with a hard, brittle crystalline material, such as quartz, the energy used to produce gliding, twinning, and other permanent lattice movements is a very small fraction of the total net energy absorbed, then this energy absorption within the grinding calorimeter can be ascribed to the creation of new surface energy alone. Such energy is, from the thermody-namic standpoint, the true effective work of the grinding device, in this case a tumbling-medium mill. The ratio of this effective work (in calories) to the total energy input (in calories) should express the thermodynamic efficiency of the comminution taking place under the conditions used in the grinding calorimeter. This approach to the measurement of the energetics of tumbling-mill grinding was suggested by some previous work by Fahrenwald and coworkers' with a laboratory ball mill and a thermometer. They measured the efficiency of grinding based on the formula: Pct Grinding Efficiency = Energy (calories) — Thermal Energy x 100 1npZ Output (calories) Energy input (calories) Efficiencies thus measured, while grinding quartz sand, ranged from 19.7 pct to 7.4 pct. Cook in 1915,' used this approach to the problem of grinding efficiencies in stamp batteries and obtained the energy input by stamp weights times drop distances and the energy output by means of thermometers and pulp flow rates. He calculated that 80 pct of the input energy to the stamp shoes was wasted as sensible heat in the ore pulp. No other studies of comminution by this method of energy differences came to the author's attention. Reasonable agreement as to the order-of-mag-nitude of comminution efficiencies in tumbling-media mills is lacking in the literature. There is a widespread impression among technical workers that the grinding efficiency of the industrial ball mill may be on the order of 1 pct, or even a fraction

Jan 1, 1952

By H. F. Seifert

The classification and preparation of non-ferrous scrap mctals is a subject of interest to every individual and corporation that employs in its processes of manufacture non-ferrous metals and alloys and accurnulates in such manufacture scrap from these materials for disposition in the form of turnings, borings, short ends, punchings, clippings, grindings, washings, etc. All too frequently the disposition of such scrap is left to indivitluals who have no knowledge of the subject either from a metallurgical or a commercial standpoint, or both. Much money is thus lost whicli with a little more intelligent effort might be saved, and in this day of fierce competition and small profits such an opportunity cannot be ignored. The Mineral Resources of the United States for the year 1925, the latest issue available (Part 1, page 221), gives the secondary non-ferrous metals of certain classes recovered in the United States for the year 1924 to 1925 as shown in Table 1. The figures are tabulated simply to give the reader some idea of the scope of the secondary non-ferrous metal industry. Approximately 900,000 tons of an annual value of $244,000,000 were recovered in the year cited. In 1916 (again using thc Mineral Resources of the United States as authority) the tonnage reclaimed was approximately 632,000 tons and the value, because of the high prices for metals prevailing at that time, amounted to $265,000,000. It is not the purpose of this paper to discuss smelting and refining operations or the feasibility of an organization, primarily engaged in some other activity, conducting smelting and refining operations to convert its own non-ferrous scrap metals and alloys. The classification and preparation of these non-ferrous materials is a preliminary step, regardless of what subsequent operations the material may pass through or where these operations may be conducted. For that reason the subject can he readily discussed without any reference to subsequent activities. Space must be provided, with suitable handling facilities, scales and the necessary storage bins where the material may be accumulated. The scope of the activity, the nature of the industry and the tonnage handled will determine, in a large measure, what preparation, if any, it rrlay he desirable to give these scrap materials to put them in the best niarketable condition. By preparation is rneant largely what, for the want of a

By R. J. Murphy, N. J. Grant, J. W. Dowding

A large number of blast furnace slag-metal tests were examined to determine if the manganese reduction could be used as a primary indicator of the degree of oxidation or reduction of the slag and of its desulphurizing power. Slag basicity and temperature were also evaluated. Two laboratory heats were made and sampled prior to reaching equilibrium to check blast furnace data. IN a recent investigation of the factors affecting desulphurization in the blast furnace, is was evident that manganese reduction appeared to parallel the course of desulphurization. Grant, Kalling, and Chipman1 pointed this out in a series of time studies utilizing closely controlled laboratory melts. Fig. 1 is a composite plot of sulphur removal and manganese reduction as a function of time under two slags of different basicity. Manganese reduction appears to approach equilibrium at approximately the same rate as does sulphur. It was also demonstrated that the addition of oxygen to the slag, as manganese oxide, caused a sharp reversal of sulphur from the slag to the metal.' It has been shown that "Excess CaO" was a primary factor in measuring the degree of desulphurization under ideal reducing conditions,1,2 the following reaction being representative of the process: CaO (slag) + S + C (solid) = CaS(slag) + CO (gas) It was also evident that a second reaction could drive the sulphur from the slag into the metal. A suggested reaction was' CaS (slag) + 0 = CaO (slag) + S Any change in the oxidizing power of the system would thus affect both the sulphur and the manganese without causing any change in the calculated basicity of the slag. "Excess CaO," "Excess Base," and other similar basicity values, under such oxidizing conditions, would therefore not be the best measure of desulphurizing power; instead, as was shown by and Chipman" he oxygen content of the slag at low oxygen levels would be the controlling factor. Unfortunately, the extent to which FeO is reduced in the blast furnace makes it difficult to utilize slag FeO as an accurate indicator of the degree of oxidation. By comparison, manganese reduction in the blast furnace proceeds more slowly and is generally only about 40 to 70 pct complete. manganese, which is present in significant amounts and is readily analyzed, offers an opportun-

Jan 1, 1954

By J. W. Harden

AT our meeting in October last we saw in operation at Pittsburgh, the comparatively modern process of the utilization of small coal by washing, by an arrangement similar to that of Berard or Morrison. The small coal washed was that of an old pile, the refuse of the mining of the Pittsburgh bed, and which had long lain uncared for. Value was thereby restored to it when it was converted into a very good coke. This circumstance led to comments on the mountains of broken coal lying wasted, and in its present condition worse than useless, in the neighborhood of the mines of the Wyoming Valley, though they are not confined to that district. Some things were said condemning the course which produced it, some were left unsaid. Of a system that destroys one-half the coal-bed in producing the other half there can, however, be but one opinion. Schemes have been suggested for the utilization of present accumulations which, if successfully applied, would in so Far be beneficial. More than ordinary attention is now being given to the same subject in England ; a Mr. Barker has invented a means by which he amalgamates the "dust," too fine to burn in ordinary grates, with a composition he calls "diamond cement," producing blocks of coal said to resist water, both hot and cold, and which a smart blow will only break to pieces, not cause to crumble. But any scheme less than the one which will prevent the wasting of coal, which still goes on, though that involves the aban- donment of the breaker, will only be one of expediency; and the latter can only be done by the aid of the consumer. But the wasting of coal is not alone with the breaker; much is made in the mine. The cause is not far to seek ; the remedy is with capitalist and owner. Owners and consumers then are alike interested, and they have it in their power, in the one case, to mitigate, in the other, almost entirely to remove the cause of the evil. Of consumers there is one in every

By R. J. Teitel

The Pb-U system has been investigated by X-ray, thermal, and microscopic analyses. Two pyrophoric intermetallic compounds were found; UPb3 and UPb. The crystallographic structure of UPb3 is reported. A phase diagram was drawn for the system showing three eutectic and one syntectic reaction. AS a result of the interest in uranium metallurgy, the Pb-U system has been investigated. Practically no quantitative data appears in the literature concerning this system. Chips were machined from bars of high-purity uranium obtained from Ames Laboratory and the lead was 99.9 pct high-purity grade from Bel-mont Smelting & Refining Co. The chips were pickled in a dilute solution of nitric acid, washed in water and then alcohol, and dried prior to use for alloy preparation. The lead was simply sheared from the pig with no chemical treatment. Lead and uranium were placed in graphite crucibles and loaded into an induction furnace. In order to insure good alloy formation, the lead was loaded above the uranium to wash the uranium chips into the melt. After the charge was held at the desired preparation temperature for 15 to 30 min, it was allowed to cool in the crucible. The entire melting operation was accomplished in an atmosphere of helium (double charcoal refined grade with no further treatment). The procedure was to outgas the furnace by first evacuating it to 10-% m Hg, admitting helium to 8 psi gage and sealing the furnace off. An optical pyrometer focused on the charge through a hole in the crucible cover was employed for thermal measurements. Usually a 50° to 70°C correction had to be added to the instrument value. The most suitable alloy preparation temperature range was found between 1220° and 1280°C. The reason for this is explained by the phase diagram, Fig. 7. Above this temperature range two liquids separate preventing alloy formation upon cooling at a reasonable rate. On the other hand, below this range the uranium was coated with a layer of both compounds and the rate of reaction was diminished by diffusion processes. The fastest reaction rate occurred in this narrow range of temperature because only UPb coats the uranium and it evidently does not protect the uranium as well as UPb,. Apparatus and Procedures The development of apparatus and techniques was determined by the peculiar properties of the alloys. All the alloys were pyrophoric, and, consequently, the alloys had to be protected from oxidation by handling them in a dry box or inert atmosphere furnaces. Other operations performed outside of this equipment had to be done as quickly as possible. Thermal analyses were conducted in a furnace and arrangement similar to that described by the author.' Graphite crucibles having a thermocouple well in the bottom were used to contain the prepared alloy, while a helium atmosphere protected the melt from oxidation. The furnace was outgassed by pumping a 10-3 mm Hg vacuum until the furnace had been heated to 400°C. Then helium was admitted and the furnace sealed under 8 psi gage pressure. Chromel-alumel thermocouples were used for thermal analysis and the accuracy of thermal measurements was judged to be k 5°C. At first, an attempt was made to use platinum-platinum-rhodium thermocouples, but evidently lead vapors attack it at high temperatures forming low melting alloys. These lead vapors had direct access to the thermocouple because the graphite crucible was porous. A differential temperature control was used to regulate thermal analyses. The thermal gradient across an alundum tube placed between the windings and the crucible was maintained constant by a controller.

Jan 1, 1953

By R. F. Stewart, A. W. Hall

A method has been developed for continuously measuring the moisture content of coal. The method is based on the thermalization of fast neutrons by hydrogen in the coal. Neutrons from a small radio-isotope source penetrate the coal, are scattered by hydrogen, and measured by a thermal neutron detector. The number of thermal neutrons counted can be directly correlated with the moisture content of coal. In a pilot-scale system, moisture was measured continuously within 0.2% in coal moving at rates up to 20 tph. The method is adaptable in industry for continuously measuring the moisture content of coal at high tonnage flow rates. Such an application would permit continuous recording of moisture in coal without sampling and facilitate quality control. An automatic and continuous method of measuring the moisture content of coal is needed by the coal industry. Automatic control of the coal quality would reduce the cost of coal preparation, improve the product, and thus indirectly increase the use of coal. Moisture in coal can be determined by several methods, but the time required to obtain samples and analyze them by existing methods makes it difficult, if not impossible, to control the quality of the product. Both producers and consumers need a method for continuous and instantaneous measurement of moisture content without sampling in order to regulate process equipment and keep the moisture content of coal within specifications. At the Morgantown, W. Va., Coal Research Center we are developing a nuclear method for continuous measurement of moisture in coal. This method is based on the thermalization of fast neutrons by hydrogen in the water and organic matter of coal. Neutrons from a small radioisotope source penetrate the coal, are scattered by hydrogen, and are measured by a thermal neutron detector. The number of thermal neutrons counted can be directly correlated with the moisture content of coal. Design of a moisture meter based on neutron thermalization depends on many variables, any or all of which can affect the sensitivity of the meter. These factors include those related to the nuclear aspect; type and size of neutron flux and source, type of detecting device, and background count; and those related to the coal being tested: rank, particle size, and ash content. A survey was initiated to eliminate the relatively insignificant factors and to ascertain the magnitude of the major effects. Such information was necessary to fully evaluate the technique and to establish design criteria. Coal contains a relatively large amount of hydrogen in the organic coal substance and the water of hy-dration of the shaly material as well as in the moisture. To apply this concept of moisture measurement to coal requires that the organic substance in coal from any one seam of a particular mine be uniform in hydrogen content. The difference in total hydrogen content of wet and dry coal is relatively small, so that a moisture measurement based on this concept requires a measurement between two large numbers to a high degree of precision. Thus, it was necessary to develop a highly precise instrumentation system for continuous measurement and to obtain a physical arrangement permitting measurement of moving coal with a minimum effect from density variation. EXPERIMENT WITH TRAYS OF COAL Tests were conducted with metal trays containing SO to 100 lbs of coal to develop an instrument system of high precision. A scaling system with a maximum instrument error of 0.2% was used to test different types of thermal neutron detectors. The most suitable type of detector was a boron-10-lined proportional counter tube. While this type of detector showed satisfactory stability, extensive testing disclosed a long-term count reduction probably due to some type of deterioration in the detector. However, development of an electronic system using dual detectors eliminated this deterioration as a serious problem. (The second detector would be used to measure a reference drum of dry coal — the difference in count rate between the wet coal and dry reference coal being a direct measure of moisture content.) Table I, column 1, shows typical results with a 1-curie plutonium-beryllium neutron source and a thermal neutron detector beneath a tray of coal and illustrates the precision of measurement. Consecutive measurements (indicated in Table 1, columns 2-5) of thermal neutrons at various times and positions be-

Jan 1, 1968

By M. F. McCarty, R. S. Olson

New organic flocculants of high-molecular weight are replacing lime, glue, and starch in liquid-solid separation. Of these synthetic materials, poly-acrylamides are outstanding. Polyacrylamides form a class of compounds varying widely in composition and activity. Separan 2610, one of the first of these flocculants' released to the mining industry in 1954, is described' as a high-molecular weight polymer of acrylamide with or without a copolymer material and with some replacement of amide by carboxylic groups. MECHANISM OF FLOCCULATION In practice, flocculation makes solids settle faster and filter better. But two opposing factors control it. The random motion that causes particles to collide favors Van der Waals' forces, which hold the particles together. The effect of zeta potential opposes this contact, and particles are mutually repelled. Flocculation can be achieved by reducing the magnitude of the zeta potential; this is the mechanism of flocculation by lime addition. The way in which polyacrylamides accomplish flocculation is not fully understood, but the action is undoubtedly comp1ex and probably varies considerably depending on the system. To begin with, the active groups of these compounds have an extremely high affinity for solid surfaces, probably by hydrogen bonding." Initially some active groups of the molecule attach themselves to the solids with a large portion of the molecule extending into the solution. Two particles can become tied together by long flocculant molecules in the following ways—by bonding between the active groups of two flocculant molecules on different particles, or by an extended molecule from one particle attaching itself directly to the surface of the other particles." These flocculant bridges prevent the particles from moving apart through random motion, but when such motion moves them together other active groups on the flocculant bridge bond to the solids, holding them in the closer position. This process is repeated until the particles are close together. Although bridging is probably a major flocculation mechanism, it is not the only phenomenon involved. Relatively neutral acrylamide flocculants reduce the magnitude of the zeta potential by increasing the viscosity of solution in the immediate vicinity of the solid surface which contains the mobile counter ions of the double layer. In other words, it moves the shear surface which bounds the zeta potential out into the solution containing counter ions which tend to neutralize the zeta potential. This effect is probably more pronounced during the initial adsorption period, before the flocculant molecules are pulled close to the solid. In some cases the slight charge of the polyacry-lamide molecule tends to neutralize a zeta potential. However, this is not a primary flocculation mechanism, as evidenced by the fact that the polyacrylamides will flocculate solids with either positive or negative zeta potential. Adsorption of polyacrylamide flocculants by a solid is substantially an irreversible reaction. Since the flocculant molecule is attached to the particle surface by many active groups of high bonding strength, desorption would require the simultaneous breaking of many bonds—an unlikely occurrence. UNIQUE PROPERTIES The irreversible adsorption of certain polyacrylamides, the flocculant's high affinity for solid surfaces and its rapid adsorption make it effective, but these unique properties require special techniques to achieve maximum flocculation. If flocculants of this type are added to a pulp as a relatively concentrated solution, the solids in the

Jan 1, 1960

By R. G. Ward

The temperature gradient in the subhearth metal or "salamandern of the iron bhst furnace results in the establishment of gradients in the concentrations of silicon, manganese, carbon, and sulfur. The temperature and compositional variations observed in three blast furnaces are analyzed according to irreversible thermodynamics and the systems appear to be close to the steady state condition. Apparent heats of transport, Q, for silicon, manganese, carbon, and sulfur are found to be respectively -17.5, -5, -2.1, and+22k cal per g mol. In conclusion the significance of thermal diffusion in extraction metallurgy is briefly discussed. INCREASING interest has been shown in recent years in the application of irreversible thermodynamics to metallurgical problems. In particular studies have been made of the transport of matter in thermal gradients1-' and under chemical gradients imposed by a binary solvent However, no detailed example in extraction metallurgy has been reported although gradients are the essence of many extractive processes. The case of the distribution of elements in molten blast furnace iron under a thermal gradient is discussed here. DATA In blast furnace operation the hearth bottom is often extensively destroyed by molten metal, and the metal may penetrate perhaps 10 ft into the furnace foundations forming a "bear" or "salamander". Several hundred tons of molten metal may thus exist beneath the level of the conventional tap hole and remain relatively undisturbed for several years under a thermal gradient. This system is subject to little convective stirring because the temperature decreases from top to bottom, and mechanical stirring due to movements in the stack and to tapping operations is unlikely to penetrate far into the metal. The system may thus be regarded as static

Jan 1, 1963

By H. F. Moore

Jan 1, 1936

By H. F. Moore

Jan 1, 1936

By G. T. Davis, C. C. Mattax, M. O. Denekas

The effects of crude oil cornponents on the wellabil-ities of sandstone and limestone were investigated. Fractions containing cornponents differing in molecular weight and molecular structure were obtained from crude oils by distillation, extration and chromatography. Individual fractions were then tested for their effects on rock wettability. Tests indicate that sundstone wetta-bility may he changed by a complex variety of surfactants varying both in molecular structure and molecular weight. Limestone appears to be particularly sensitive to basic, nitrogenous surfactants. INTRODUCTION Investigations in recent years have shown that petroleum reservoir rock wettability can exert a significant influence on the efficiency with which oil can be produced by water flooding. While most reservoirs are presumably water-wet, they niay range in their degree of water-wettability from near-neutral to strongly water-wet.'" Reservoir wettabilities other than strongly water-wet are likely to be induced by adsorption of surface-active components froni the crude oil on the pore walls of reservoir rock.:' Little is known, however, about the nature of the surface-active materials which are likely to be adsorbed by the reservoir rock. Due to the complexity of crude oils. attempts made in the past90 isolate these surface-active components have met with only limited success. It is probable that many different types of surface-active materials arc indigenous to crude oils and that many of these may be adsorbed to varying degrees by reservoir rock. This was cxolored in the studies discussed in this paper. The over-all objective in these studies is to ascertain whether the wettability of a given reservoir can be determined by examining the surfactant content of the reservoir crude. To this end, crude oils were examined to determine the variability of indigeneous surfactants with regard to chemical type and molecular weight. Crude oils were separated by distillation into fractions differing principally in molecular weight, by chroma-tography into fractions containing compounds differing in polarity, and by solvent extraction into nitrogenous and non-nitrogenous fractions. Individual fractions were then tested for their effects on the wettabilities of sandstone or limestone rock samples. EXPERIMENTAL PROCEDURES Fractionation of the Crude Oils Samples of Miocene, Eocene and Jurassic crudes were distilled at temperatures not exceeding 200°C. The final stages of distillation were completed in a molecular still at pressures down to three microns of mercury. Fifteen to 30 fractions were obtained from each crude oil. These cuts were sufficiently broad that separation can be considered to have been effected principally on the basis of the molecular weights of the constituents of the crude oil. A considerable portion (20 to 40 per cent) of the crudes would not distill under these conditions. The residues were recovered and tested with the other fractions. Fractions differing in polarity were separated from a crude of Pennsylvanian age and an extracted sample of Miocene oil by chromatography, using a solid adsorbent. Since surfactants are, for the most part, polar compounds, chromatography should separate many of the surfactants from the crude oil. Such a separation should provide fractions containing compounds differing in molecular structure. Nitrogeneous compounds were extracted from Miocene crude oil with a solution of sulfuric acid in meth-anol. The residual oil was further processed by chonia-tography. Each of the fractions obtained by thesc procedures was dissolved in a non-polar solvent (xylene) and diluted to its original concentration in the crude oil. No attempt was made to maintain an anaerobic atmosphere above the samples while they were being dissolved. These solutions of the fractions were then tested for their effects on the wettability of sandstone and limcstone as discussed in the next section. Measurement of the Effects of Crude Oil Fractions on Rock Wettability No entirely satisfactory method for measuring rock wettability has yet been developed. All methods used are empirical. The imbibition test was used in these studies. This test is based on the tendency of a rock to imbibe the wetting phase spontaneously. For example, if a strongly water-wet rock is first saturated with oil and then placed in water, the water will quickly invade the rock by capillarity and much of the oil will be displaced. If the rock is slightly water-wet, water irnbibition will proceed more slowly and, in many instances, considerably less oil will be displaced. A water-saturated, oil-wet rock will imbibe oil. The initial rate with which water (or oil) imbibition takes place indicates, qualitatively, the degree of water (or oil) wettability of the rock.

L. D. Ricketts, New York, N. Y.-In recent years the metallurgical field of the copper industry has expanded greatly, the copper ores have become lean and diverse in character, and we are obliged to treat such ores on a very large scale. On the commercial side, the operating and consulting staffs of ,the great mining companies have been enlarged and organized, and no great capital expenditure is decided upon until it has been investigated and recommended by a highly organized force of specialists as a committee. I believe that in the scientific field and in the most valuable proceedings of our various societies the old idea of one-man point of view and one-man treatment of principle and detail together has been. splendidly developed and should continue, but for the advancement of our art we should deliberately discuss subjects among ourselves in order to do away with the idiosyncrasies of the individual and to gain a composite view representing the best thought of many men. In the development of new ideas leading to the introduction of new methods, the societies could enlarge their present great field of usefulness if such discussion be had, and in my opinion further great good could be done if a number of men of different qualifications and experience would join in preparing a joint book, each dealing with his particular problem, but consulting the other men. In this way individualism would be preserved and various processes would be described, and if properly reviewed the paper would be palpably capable of analysis, and the student would have at his command the associated efforts of a group of qualified engineers.

Jan 4, 1915

By M. King Hubert

The growth of human knowledge is an evolutionary process. Historically our separate sciences came into existence as people became interested in various apparently unrelated domains of phenomena, and in this manner we acquired the sciences of physics, chemistry, astronomy, biology and geology. As various of these sciences became established, cognizance of them came to be taken by the universities and in this manner there arose the traditional departments of physics, astronomy, chemistry, biology and geology of our American universities. As there was no particular rationality in the boundaries separating the various sciences, in the university departments the jurisdiction of each has assumed quite arbitrary limits. In the domain of earth phenomena the first science to grow up was that of geology, which arose originally from the activities of the collectors of rocks, minerals and fossils. Thus geology evolved as a descriptive science dealing with directly observable terrestrial phenomena for which elementary rational explanations were offered. The traditional treatment of phenomena by the science of geology has rarely been with more than an elementary regard for the fact that these phenomena were also phenomena of physics and chemistry. Since the latter part of the nineteenth century, a new approach to terrestrial phenomena has been emerging and becoming of so great a significance that it can no longer be ignored. This approach has been made by people trained primarily in the sciences of physics and chemistry, who have investigated terrestrial phenomena as constituting phenomena of their respective sciences. In this manner we have acquired the so-called "borderland sciences" of geophysics, the physics of the earth, and of geochemistry, the chemistry of the earth. Neither of these fields is new, having arisen chiefly at the hands of European investigators during the latter part of the nineteenth century. The European universities have long since given official recognition at least to geophysics, by the establishment of departments or institutes of geophysics, which are on a par with the university departments of the other sciences.

Jan 1, 1940

By M. King Hubert

The growth of human knowledge is an evolutionary process. Historically our separate sciences came into existence as people became interested in various apparently unrelated domains of phenomena, and in this manner we acquired the sciences of physics, chemistry, astronomy, biology and geology. As various of these sciences became established, cognizance of them came to be taken by the universities and in this manner there arose the traditional departments of physics, astronomy, chemistry, biology and geology of our American universities. As there was no particular rationality in the boundaries separating the various sciences, in the university departments the jurisdiction of each has assumed quite arbitrary limits. In the domain of earth phenomena the first science to grow up was that of geology, which arose originally from the activities of the collectors of rocks, minerals and fossils. Thus geology evolved as a descriptive science dealing with directly observable terrestrial phenomena for which elementary rational explanations were offered. The traditional treatment of phenomena by the science of geology has rarely been with more than an elementary regard for the fact that these phenomena were also phenomena of physics and chemistry. Since the latter part of the nineteenth century, a new approach to terrestrial phenomena has been emerging and becoming of so great a significance that it can no longer be ignored. This approach has been made by people trained primarily in the sciences of physics and chemistry, who have investigated terrestrial phenomena as constituting phenomena of their respective sciences. In this manner we have acquired the so-called "borderland sciences" of geophysics, the physics of the earth, and of geochemistry, the chemistry of the earth. Neither of these fields is new, having arisen chiefly at the hands of European investigators during the latter part of the nineteenth century. The European universities have long since given official recognition at least to geophysics, by the establishment of departments or institutes of geophysics, which are on a par with the university departments of the other sciences.

Jan 1, 1940

By J. C. Cordell, C. F. Weinaug

A study of the behavior of retrograde condensation from gas mixtures was made in the presence and absence of sand in order to determine if the condensed liquid would re-vaporize in the Presence of sand. Methane-butane and methane-pentane mixtures that would form liquids by retrograde condensation when produced from a constant volume cell were used. The methane-butane mixtures of similar composition were produced by three different methods. The first two were charged into an empty cell and were produced in one case within a period of 9 hr and in the other within a period of 3 days. The third mixture was charged to a sand-packed cell and produced within a period of 9 hr. The curves relating composition of the produced gas to pressure obtained from these experiments show that equilibrium was maintained as long as liquid was condensing. However, during the portion of the pressure decline where the condensed liquid should be revaporizing, equilibrium was maintained only when the mixture was produced from the sand-packed cell. The methane-pentane mixture is produced only in the presence of sand. The data obtained for this system also show that equilibrium is maintained at all times during the pressure decline. These results indicate that revaporization is aided rather than prevented by the fact that the condensate "wets the sand." The significance to the petroleum industry of the behavior of hydrocarbons in the retrograde region is becoming increasingly important because a large percentage of reservoirs being discovered today arc of the gas-condensate type. The important characteristic of a gas-condensate reservoir is the retrograde condensation of a liquid phase throughout the reservoir if the pressure is allowed to decline. In order to prevent the loss of this retrograde liquid in some of these reservoirs, they are "cycled"; that is, the material produced from the reservoir is processed to remove the heavier hydrocarbons and the light fractions are returned to the reservoir to maintain the reservoir pressure. Another method of producing these reservoirs is Pressure depletion. There are other methods but they are not in general use. Although a large number of factors are involved in determining the optimum method of producing a reservoir, only the problem of whether the retrograde condensate resulting from pressure depletion will revaporize from sand at equilibrium conditions is considered in this paper. Also the data are limited to the methane-n-butane and the methane-n-pentane systerns at loo°F and one type of sand. Three types of tests were run in order to compare the revaporization of retrograde liquid formed in a cell with that formed in a sand-packed cell, and to establish the effect of time. The results of tests presented in this paper indicate that both time and the presence of sand promote the revaporization of

Jan 1, 1949