Search Documents

By David Hill

"End of panel longwall face recovery is almost certainly the most involved recurring geotechnical problem faced by operators, with major loss potential should problems occur. The paper presents Australian experiences and updates the outcomes of an industry sponsored research project on the geotechnical issues associated with conventional longwall recoveries.A number of critical features of the geotechnical environment, support design and mining geometry have a pronounced impact on ground control during face recovery. A model of roof behaviour at the take-off point has been developed and validated. Key geotechnical issues include low roof competency, an adverse weighting environment, geological structure, horizontal stress concentrations at the gate ends and the capacity and. integrity of the shields. All of these are identifiable either at the support design stage or, at worst, prior to the start of powered support removal, which is the critical stage of the recovery process.Key aspects of the geometry and process are the ability to maintain powered support resistance during bolt-up and recovery, the direction of shield removal, the impact of chutes and the speed of the shield removal process.The author presents case studies that illustrate these issues and the associated ground behavior.INTRODUCTIONEnd of panel face recovery is almost certainly the most involved recurring geotechnical problem faced by operators, with major loss potential should problems occur. However, unlike most geotechnical aspects of coal mining, very little research has historically been undertaken on the issue of conventional longwall recoveries. This is in marked contrast to the design of pre-driven recovery rooms, an issue which has attracted considerable research interest (Thomas, 2008). In 2006, Strata Engineering completed an Australian industry (ACARP) sponsored research project aimed at defining and minimising the geotechnical threats during longwall face recovery (Strata Engineering, 2006). The research project had the overall objective of developing guidelines for the specification of ground control strategies, so as to minimise the likely geotechnical threats relating to the safety, operational costs and production delays associated with the recovery of a longwall face."

Jan 1, 2010

By Hillary W. St. Clair

This report describes a mathematical procedure for analyzing size distribution data by the method of moments. The method was applied to Andreasen's data on a variety of grinding mill products. It was found that the observed size distributions could be represented by gamma and beta distribution functions over a wide range of sizes. A computer program, written in BASIC, is described for calculating moments, distribution parameters, and the weight fraction in any size range.

Jan 1, 1969

By B. K. Choi, G. E. Kim, S. Noh, T. K. Kim

Oxide dispersion strengthened (ODS) steel has been developed as the most prospective core structural material for next-generation nuclear systems because of its excellent high strength and irradiation resistance. In ODS steel, finely dispersed nano-oxide particles with a high number density in the homogeneous grains can be very attractive to achieve superior mechanical properties at high temperatures, and these favorable microstructures can be significantly changed using process parameters during the mechanical alloying procedures. In this study, the effects of mechanical alloying times on the microstructure of 10Cr-1Mo ODS martensitic steel were investigated. Pre-alloyed powders with Y2O3 powder were mechanically alloyed for various milling times using a high energy horizontal ball-mill apparatus (model: symoloyer CM20). Powder properties such as the mean particle size, size distribution, and crystallite size were evaluated. Uniaxial hot pressing was employed to consolidate the milled powders. The results of a microstructural observation after the MA and UHP processes indicated that the homogeneity of the martensitic structures was considerably increased with the longer milling time. It is thus concluded that the mechanical properties of the ODS martensitic steel are greatly dependent on the mechanical alloying times.

Jan 1, 2015

By Lashley Harvey

Ante la expansión de las industrias, los países desarrollados realizan un inventario de sus recursos hidráulicos en el que se revela la falta de suministro para un futuro crecimiento. En ese sentido, el presente texto describe los métodos de uso y conservación de agua subterránea para encontrar el más adecuado tratamiento de agua usada que restauren las cualidades de su estado original.

Mar 1, 1976

By A. Y. Senchenko, Y. V. Kulikov

"Different methods aiming at specific energy calculation and design of AG/SAG circuits are used in mining. They include JK DWT/SMC test, SAGDesign test and CWi/RWi/BWi tests. The simplest methods with no secret equations and giving energy required for grinding in kWh/t were proposed by F.?. Bond and J.H. Starkey. D.J. Barratt proposed to use results of CWi/RWi/BWi tests for AG/SAG mill sizing. The present paper gives an alternative for forecast of specific AG/SAG energy. The principle is similar to the theory proposed earlier and consists in cumulative AG/SAG energy calculation using indices of rod and ball grinding (RWi+BWi) without impact crushing index (CWi). Then total energy is divided between two grinding stages using special formulas based on extensive statistical information. The forecast indices of AG/SAG and ball grinding are similar to the SAGDesign testing results. Hereinafter the predicted indices are used for mill sizing of the whole grinding circuit. The method considered in the paper enables prediction of AG/SAG energy based on the test results according to Bond method. The proposed method version was not widely published earlier. The aim of the work was to elaborate cost-effective, reliable and accessible way to determine specific AG/SAG energy. At this stage of method development, it is recommended to use it only for works at preliminary Geometallurgy stage (Scoping, Pre-Feasibility). At design stage the obtained data should be confirmed by appropriate testing using alternative JK DWT/SMC and SAGDesign methods.INTRODUCTIONAppropriate crushing and grinding testing is required to design efficient comminution circuits. It is obviously important to obtain accurate information about ore hardness properties since the main energy consumption at the plant is associated with comminution processes. Moreover, it is required to apply the processes that make it possible to minimize operating costs and efficiently use capacity of the installed equipment installed.When studying ore hardness properties, it is required to take into account that breakage of the material is performed using different equipment. That is why accurate selection of the equipment and the circuit calculation without relevant testworks is impossible. Ideally, the testworks should provide answers to the following questions: determination of ore hardness properties, determination of specific energy consumption for comminution as well as obtaining of sufficient amount of statistically significant results from the tests. The results from crushability and grindability testworks in the first place provide assessment of ore hardness properties and in addition correlate with throughput of the respective equipment. The data obtained can be used for modeling of comminution circuits at the stage of the technology development"

Jan 1, 2016

By William Breeding

Cuando un ingeniero recibe información sobre el yacimiento de un dueño de la propiedad, su forma de investigar dependerá de los equipos que estén a su alcance y costo. En ese sentido, el texto señalará la evaluación técnica que el ingeniero técnico debe conocer para estimar las reservas que satisfagan las aspiraciones del interesado. Así, el evaluador que trabaje para una compañía estable y cuente con equipos y personal entrenado en la vecindad de la propiedad, tendrá una labor mucho más fácil que un evaluador en un sector remoto donde no haya equipos y personal entrenado disponibles. El primero podrá empezar el trabajo sin mucha demora, mientras que el segundo necesitará semanas o meses para prepararse.

Mar 1, 1978

By Peter G. Cooper

"During 1987, the feasibility of modernising the ER&S smelter at Port Kembla, NSW, Australia was studied. The selection of appropriate technologies to carry the smelter into the 21st century considered issues such as capital cost, existing infrastructure, feed mix, capacity, product quality, flexibility and potential for further development. Both hydrometallurgical and pyrometallurgical process schemes were considered. Some novel combinations were assessed but ultimately rejected. Final technology selections included proven smelting and anode furnace processes, pyrometallurgical slag cleaning and modifications to existing equipment. This process scheme balanced risk against development potential within the constraints imposed by the existing plant.BackgroundThe Electrolytic Refining and Smelting Company of Australia (ER&S) has operated a custom copper smelter at Port Kembla since 1908. Existing technology includes a sinter plant/blast furnace, three small Peirce Smith converters, two reverberatory anode furnaces and a conventional tankhouse. These process units were all installed prior to 1960 and have proven to be flexible enough to process the wide variety of domestic feed materials purchased by ER&S.However, by the early 1980s, threats to domestic concentrate supplies highlighted the need for major changes to reduce operating costs to world competitive levels. Various studies in the ensuing years failed to identify an economically attractive solution. Furthermore, pressures were increasing to improve the environmental performance of the smelter.During 1986 the options for redevelopment were again considered and by the end of 1987 technologies for the retrofit had been selected and a full feasibility study was completed."

Jan 1, 1988

By N. S. Tanious

This work was completed prior to the author's appointment with the Nuclear Regulatory Commission (NRC). Therefore the views and conclusions contained in this paper are those of the author and should not be interpreted as necessarily representing the official policies or recommendations of the NRC. Reference to specific brands, instruments, or trade names is made to facilitate understanding and does not imply endorsement by the author or the NRC.

Jan 1, 1987

By Paul W. Billwiller

Introduction In 1937, the Britannia Mining and Smelting Company, Limited, was carrying on an extensive exploratory diamond-drilling programme. Most of this drilling was done on the 4100 level, the lowest working level in the mine. One of the exploratory diamond-drill holes, at approximately 12,500 feet from the portal of the tunnel, encountered heavily mineralized stringers of chalcopyrite and sphalerite in silicified grey schist. The mineralization was encountered just to the hanging-wall of the green mottled schist at a point 350 feet south of the 4100 tunnel. To delimit this new orebody, drifts and cross-cuts were driven on 3500, 3800, and 4100 levels to the hanging-wall in the area of the projected mineralization. On the 3500 level, the top of the mineralized zone was encountered. The zone was thoroughly explored by drifting and diamond drilling. The mineralization, however, was not sufficiently concentrated to be of commercial grade. On the 3800 level, the zone was found to consist of disconnected stringers of chalcopyrite and pyrite. Drifting was continued to the west and a long lens-shaped area of grey schist containing fairly heavy stringers of chalcopyrite was delimited. This lens later proved to be very close to the top of the commercial mineralization of the No. 8 orebody. On the 4100 level, a diagonal cross-cut was driven to the footwall of the downward projection of the mineralized zone. Diamond-drill holes from this cross-cut indicated a zone of heavy mineralization. A drift was driven off the cross-cut parallel to the zone and some distance to the footwall of it. Further diamond drilling disclosed a mineralized zone approximately 300 feet long and 35 feet wide containing sphalerite, chalcopyrite, and pyrite. The foregoing development work indicated a fairly large lens of mineralization of sufficient concentration to be classed as ore between the 4100 and 3800 levels. To explore this mineralization at depth, long diamond drill holes, dipping at minus 57° and minus 80°, were planned from some point to the hanging-wall of the orebody. The 4100 level was not suitable for small development headings, due to wider gauge track and larger cars than on the levels above. Therefore, a raise was driven from the diagonal cross-cut on the 4100 level to a point some 70 feet above and just inside the footwall of the orebody. From the top of the raise, drifts were expanded east and west to delimit the ore zone. In addition, a long cross-cut was driven 350 feet to the hanging-wall, and drifts were opened east and west from the end of the cross-cut to provide diamond-drill stations for the exploration of the orebody at depth.

Jan 1, 1946

By Srinath Viswanathan, Adrian Sabau

"In general, the occurrence of microporosity during metal casting is due to the combined effects of solidification shrinkage and gas precipitation. The governing equations for fluid flow and hydrogen evolution indicate that porosity formation and fluid flow are strongly coupled. However, in most studies on microporosity, it is considered that the porosity formation does not influence the fluid flow in the mushy zone. In this study, a computational methodology is presented for the numerical simulation of interdendritic fluid flow and microporosity evolution. The solution algorithm presented includes a fully coupled, implicit treatment of microporosity and local pressure in the mushy zone. The effects of microporosity evolution due to the local pressure drop in the mushy zone, and pore expansion in casting regions where liquid feeding alone cannot compensate for the solidification shrinkage are also considered. It is shown that neglecting the effect of porosity formation on the pressure in the mushy zone yields higher pressure drops. By its growth, microporosity partially compensates for the solidification shrinkage, reducing the feeding demand. A reduced feeding demand requires less fluid flow to compensate for solidification shrinkage, and results in smaller pressure drops in the mushy zone. Therefore, in order to accurately describe casting defects, comprehensive models of fluid flow, heat transfer, and solidification must include the effect of microporosity as well.IntroductionIn the terminology commonly used by foundrymen, porosity is usually considered to be either ""hydrogen"" or ""shrinkage"" porosity. Hydrogen porosity is the term given to porosity that is generally rounded, isolated, and well distributed. Porosity that is interconnected or clustered, and of an irregular shape corresponding to the shape of the interdendritic region, is usually termed shrinkage. In general, the occurrence of microporosity in aluminum alloys is due to the combined effects of solidification shrinkage and gas precipitation [1]. Continuum models [1, 2- 7] have been used to predict the level of porosity in castings. A number of other studies have also attempted to understand the phenomena of porosity formation and pore growth [8-10] and pore morphology [11].The governing equations for fluid flow and hydrogen evolution indicate that porosity formation and fluid flow are strongly coupled. However, in most studies [4, 9, 10], it is considered that the porosity formation does not influence the fluid flow in the mushy zone. Kubo and Pehlke [3] presented a methodology for the prediction of microporosity distribution in shaped castings by considering the effects of both the hydrogen precipitation during solidification and the pressure drop in the mushy zone. In their approach, the local pressure and porosity were computed in an uncoupled manner based on a ""flux of interdendritic liquid"" criterion, i.e., either pressure or porosity was first computed using the other variable at the previous time step. Their approach has been used with little change in numerous studies [6, 12, 13]. Recently, Kuznetsov and Vafai [14] presented a fully coupled, one-dimensional model for the computation of pressure and porosity. They showed that neglecting the effect of porosity formation on the pressure in the mushy zone yields higher pressure drops and an over-prediction of final porosity. They also showed that the influence of porosity formation on the pressure is larger at lower pressures in the mushy zone."

Jan 1, 2001

By R. W. Coburn

The results of field experiments on wells which required stimulation indicated that engineered well-completions will cause an increase in ultimate recovery at reduced costs. Techniques and tools have been developed which can be used to establish well conditions most conducive to successful stimulation. Cementing, perforating and treating are bound together so completely that the success of one phase is completely dependent on the .effectiveness of the preceding phase. A method of determining the efficiency or effectiveness of any given well-stimulation treatment has been derived. Pressure behaviour during a treatment can be analyzed to yield the total percentage of the formation which has been treated.

Jan 1, 1960

By W. C. Brice

A cooperative study was undertaken by representatives of the environmental community, the mining industry, and state government to identify and resolve environmental issues associated with base and precious metal mining in a neutral atmosphere before a commercial mining development is announced. The study included testing Minnesota's as-yet-untried non-ferrous mining regulatory program using three hypothetical mining developments sited in environ-mentally sensitive areas where future mining could occur. Results include identification of critical paths for regulatory decision making, identification of particularly sensitive environ-mental issues that will need continued deliberation before resolution, and characterization of data necessary for environmental review and permitting decisions.

Jan 1, 1990

By J. J. Kramer, W. A. Tiller, G. F. Bolling

THE axial orientations of columnar crystals in unidirectionally solidified ingots of zone-refined zinc and tin have been examined using the techniques recently described by us.' Both metals had an initial purity of 99.999+ pct before zone refining and satisfied all qualitative guides for very high purity after zone refining. Fig. 1 presents the orientations of the columnar crystals for tin and zinc, respectively. For tin, there is a preference for grains growing in the [I101 direction, i.e., the dendrite direction.' For zinc, a weak preference for the [0001] direction is seen (a random population in the unit triangle would give equal density on either side of the 60-deg circle centered on [0001]).' There was no apparent evidence for dendritic growth in either metal. These results, and those previously reported,' confirm the recent investigation by Hellawell and Herbert of casting textures observed for zone-refined lead, zinc, and tin.4 The preferred casting orientations for these metals in both the impure and zone-refined states are given in Table I. In the experiments on zone-refined lead,' it was shown that two separate textures existed: a preferred (111) nucleation texture existed at the chill surface and a preferred (111) texture developed during solidification. Either effect is sufficient to produce the result recorded in Table I. Similarly the results recorded for tin and zinc may be attributable to either a preferred nucleation or a preferred growth phenomenon and additional experiments are required to separate these two possible explanations. Hellawell and Herbert' attribute their results to a preferred growth process and account for it on the basis of a "layer-growth" model proposed much earlier by one of the present authors.5 An equally satisfactory growth model would be that based upon anisotropic surface energies. However, both of these growth models would indicate that the preferred growth direction for very pure metals should be normal to the plane of closest packing in the metal. This is consistent for zinc but, contrary to the conclusion of Hellawell and Herbert, it is not consistent for tin since here the (100) is expected to exhibit a greater density of packing than the (110). Although tin is expected to exhibit an anisotropy of thermal conductivity, we would expect the thermal conductivity to be the same in the [1101 as the [l00]

Jan 1, 1963

By W. J. Taylor

Some eight years ago I became interested to a considerable extent in one of the well-known deposits of sulphury iron ore in New Jersey, and, as a consequence, soon became interested in the subject of the elimination of the sulphur. On investigation I found that no department of pig-iron manufacture had received less attention than that of roasting or calcining ores for the elimination of sulphur, carbonic acid, water, etc. My first devices to eliminate sulphur mere naturally in the limekiln line, with solid fuel mixed with the ore, in the same way = common lime is burnt with small coal. While this process will succeed tolerably well for carbonates or calcareous ores, even though they contain sulphur as sulphates, I soon found it would not answer for our magnetites, which are very hard and dense, carrying from 2 to 5 per cent. of sulphur as pyrites, and become very sticky as soon as any attempt is made to roast them at a high heat. Some laboratory experiments developed the fact that the nearer the gaseous current surrounding the hot ore approached in composition pure atmospheric air the more rapidly the sulphur was oxidized, while in an atmosphere composed largely of carbonic oxide, carbonic acid, and nitrogen, it seemed almost impossible to reduce the sulphur more than one-half, which was a confirmation of the well-known Pact that just one-half of the sulphur in pyrites volatilizes very easily, and that the trouble is mainly to remove the remainder. It was thus apparent that the atmosphere surrounding the ore was of as much importance as the temperature..• This led to the trial of a kiln to heat the ore by conduction through the brick. It was divided into ore-chambers, which were surrounded with flues, through which the products of combustion of gaseoua fuel passed without coming in contact with the ore. We did not, however, succeed by this arrangement in getting more than a cherry-red heat, which, of course, was too low to accomplish anything. I had at this point become convinced— 1st. That gaseous fuel only would accomplish the work successfully. 2d. That since a high temperature was required to insure a rapid oxidation of the sulphur, and also to make the ore open and porous,

Jan 1, 1881

By J. Doucet, C. Price

In an industrial setting, operational changes are continually introduced, driven by new technologies or changing economics. Because of day-to-day variability, quantifying the impact of these changes based on metallurgical performance requires long trial periods to achieve statistically significant results. Tools and techniques developed by the mineral processing group at McGill University have allowed for direct measurement of process variables (e.g., bubble size, gas and solid holdup). Two case studies are described where direct measurement techniques were used to evaluate: a) a new rotor stator mechanism; and b ), the introduction of a new frother type. Application of these methods has accelerated the evaluation of process changes and improved confidence in results.

Jan 1, 2009

By R. R. Sacrison

The Barrick Mercur Gold Mine lies in the Oquirrh Mountains of northern Utah. Limestone, sandstone, shale, and chert are the predominant rock types being mined. Recent expansion has encountered rhyolite. Lithology and structural attitudes control most mechanical behavior. Slope steepening, mine planning, and site selection are presented as means by which geological engineering has contributed to the economics of the operation. Geomechanics investments of approximately $700,000 have resulted in cost savings or additional production worth over $16,000,000.

Jan 1, 1990

By W. J. Taylor

SOME eight years ago I became interested to a considerable extent in one of the well-known deposits of sulphury iron ore in New Jersey, and, as a consequence, soon became interested in the subject of the elimination of the sulphur. On investigation I found that no department of pig-iron manufacture had received less attention than that of roasting or calcining ores for the elimination of sulphur, carbonic acid, water, etc. My first devices to eliminate sulphur were naturally in the lime-kiln line, with solid fuel mixed with the ore, in the same way as common lime is burnt with small coal. While this process will succeed tolerably well for carbonates or calcareous ores, even though they contain sulphur as sulphates, I soon found it would not answer for our magnetites, which are very hard and dense, carrying from 2 to 5 per cent. of sulphur as pyrites, and become very sticky as soon as any attempt is made to roast them at a high heat. Some laboratory experiments developed the fact that the nearer the gaseous current surrounding the hot ore approached in composition pure atmospheric air the more rapidly the sulphur was oxidized, while in an atmosphere composed largely of carbonic oxide, carbonic acid, and nitrogen, it seemed almost impossible to reduce the sulphur more than one-half, which was a confirmation of the well-known fact that just one-half of the sulphur in pyrites volatilizes very easily, and that the trouble is mainly to remove the remainder. It was thus apparent that the atmosphere surrounding the ore was of as much importance as the temperature. This led to the trial of a kiln to heat the ore by conduction through the brick. It was divided into ore-chambers, which were surrounded with flues, through which the products of combustion of gaseous fuel passed without coming in contact with the ore. We did not, however, succeed by this arrangement in getting more than a cherry-red heat, which, of course, was too low to accomplish anything. I had at this point become convinced – 1st. That gaseous fuel only would accomplish the work successfully. 2d. That since a high temperature was required to insure a rapid oxidation of the sulphur, and also to make the ore open and porous,

Jan 1, 1881

By Liugen Sun, Xingming Jiang, Weijiao Yang, Yihang Hu, Yongqiang Yang, Hua Wang

During the past decades, cyclone electrowinning (CE) has been regarded as a novel separation technology, which can be used for direct electrowinning of metals from low concentration solution. Recently, CE was proven effective for the treatment of antimonic gold concentrates. The experimental results of cyclone electrowinning of antimony show the current efficiency increases from 43.8 to 72.2% with the increasing current density (from 254.8 to 647.3 A/m2), and on the other hand, power consumption per ton antimony decreases from 6100 to 4200 kWh with the aforementioned increasing current density. The grade of the obtained cathode antimony could reach 98.6%. Compared with the traditional electrowinning using parallel-board electrodes, the economic profit of CE was 33.1% higher attributed to the high current efficiency of CE. In addition, CE could adapt to high current density. All these characteristics indicate the CE method can be implemented commercially for processing antimonic gold concentrates.

Mar 1, 2018

By Max Roesler

W. L. CUMINGS,* Bethlehem, Pa. (communication to the Secretary+). -In this discussion of Mr. Roesler's paper, I shall follow Kemp in using the term "granite" to refer to the acid rock called syenite by Kimball. Diorite, as I understand it, is the dark basic rock invariably closely associated with the orebodies. The types of rock of intermediate composition, mainly intrusives, are not under discussion. It is difficult for me to conceive that this granite is the ore-bearing agent, for the following reasons: 1. No isolated orebodies in the granite are known. It would seem that if this rock is the mineralizer, some small bodies, or at least patches and small masses of ore so situated would exist. 2. In 1909 the writer conducted explorations on the Pequena and Grande claims about 1 mile north of West Mine No. 5. This work was done after a very careful magnetic survey had shown a large and uniform area of attraction. As exploration progressed, it became evident that in this case the magnetic attraction was due to disseminated magnetite. Much ore of 40 per cent. Fe was found, but very little commercial ore was shown up. This ore was entirely in the diorite and no granite outcrops are near. The occurrence could easily have been described as "ore formation but very little ore." I cannot conceive how a remote granite intrusion could impregnate a diorite mountain with 40 per cent. of Fe, and prefer to believe that this 40 per cent. of iron was in its real home, rather than in a sort of dioritic "boarding house" after having been evicted by granitic parents. 3. The Ocaña mine, which has produced nearly 500,000 tons, shows no evidence that the granite is the mineralizer. This is admitted by Mr. Roesler on p. 1827. 4. I believe it will not be disputed that all the iron-ore deposits extending along the south coast for 60 or 70 miles are of a similar origin. Evidence available at other points might properly be referred to in discussing the article under review. At the La Plata mines, about 60 miles west of Santiago, the writer has also made explorations. No granite is in evidence. At one point in the bed of a creek is a small body of magnetite about 10 ft. long, entirely surrounded by a hard fresh diorite. To me

Jan 3, 1917

By J. B. Austin

It is now well established, chiefly through the work of Davenport and Bain,' that the influence of temperature upon the rate of transformation of austenite to ferrite at constant temperature is represented by a curve of the type shown in Fig. 5 on page 295 and the reasons for this general shape have been discussed by them in a qualitative way. Thus, the upper part, or nose, of the curve is the resultant of two factors of which the rate of change with temperature is not the same, and by analogy with other like cases it is almost certain that these factors are: (1) the chemical potential, or driving force, of the transformation, which is zero at the equilibrium temperature and increases rapidly as the temperature falls below this point; and (2) a factor analogous to viscosity, or resistance of the crystal lattice to a change in structure, which also increases as the temperature is lowered. Just below the equilibrium temperature this virtual "viscosity" of the metal is relatively low—that is, the metal offers little resistance to a change in lattice—but the driving force is also small, and the net result is that the reaction proceeds slowly. As the temperature is lowered the magnitude of both factors increases; but at first the driving force increases more rapidly than the resistance and the reaction is observed to proceed more rapidly. At lower temperatures, however, the resistance begins to increase faster than the driving force, and eventually, at the nose of the curve, overbalances it, causing the reaction to proceed more and more slowly thereafter. This concept is somewhat, though not completely, analogous to that employed in certain electrical cases where the precise factors are known and are separately measurable. The current I (in amperes or coulombs per second) flowing through a given wire is proportional to the impressed potential, or driving force E, and is inversely proportional to the resistance R of the wire; that is, I = E/R. Stated in a slightly different way, the time required for one coulomb to pass a given point (1/I) is equal to R/E. If the temperature of the whole circuit is changed, the resultant change in 1/I will depend on the relative rates of change of R and of E,

Jan 1, 1935