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By C. G. Dunn, J. L. Walter

COULOMB' and Coulomb and Lacombe2,3 have recently discussed secondary recrystallization in soft iron (99.5 pct Fe). They found that the appearance of this phenomenon was dependent on both the presence of impurities and the thickness of sheet specimens. They concluded that impurities such as carbon, sulfur, and oxygen in the soft iron stabilized the matrix structure and allowed growth of a few grains of specific orientations. They also found that secondary recrystallization ceased when the final thickness was small and attributed this complete inhibition of growth in thin sheet to the restraining action of thermal grooves. When purer iron (99.99 pct Fe) was used, normal grain growth but not secondary recrystallization was obtained. On the other hand it is known that the necessary stabilization of the matrix structure for secondary recrystallization in high-purity silicon iron probably does not depend on impurities but more likely results from the specimen thickness effect of Beck et al.,4 according to evidence and ideas advanced by Walter and Dunn,5,6 and Detert.7 Furthermore, Mullins8 has indicated that if a gas-metal surface energy difference exists across a grain boundary equal to or greater than about 3 pct of the grain boundary energy, then such a grain boundary should not become stuck. Similarly, Walter and Dunn have estimated that any increase in restraining force due to increased thermal grooving with decrease in

Jan 1, 1962

By D. W. Breck

Zeolites were first recognized as a new group of minerals by Cronstedt with the discovery of stilbite in 1756. The word zeolite was coined from the two Greek words meaning "to boil" and "a stone" because of the loss of water when heated in the mineralogist's blowpipe (Breck, 1974). In 1845 it was discovered that certain soils lave the power of retaining ammonium salts Way, 1850). These were the first ion exchange experiments. Later it was discovered that it was the hydrated silicates in the soil that produced this phenomenon. Several years later a paper was published dealing with the action of dilute salt solutions on silicates which showed that this base-exchange principle, which we now call cation exchange, is reversible. The quantitative cation exchange behavior of zeolite minerals, such as chabazite, was studied. As a result any aluminosilicate which exhibited the property of ion exchange was referred to as a "zeolite," even today the term has been applied to clay minerals as well as synthetic organic ion exchange resins.

Jan 1, 1975

Roof Bolts An expansion shell and plug Westinghouse roof bolting assembly made for use with threaded steel rods and large flat washers or steel channel employs a plug larger in diameter than those for trolley wire service. The notched plug helps prevent shell and plug from turning. The unit is shipped complete. Circle No. 1 Fan The Jeffrey Mfg. Co. Aerodyne Midget fan is a self contained blower or exhauster for auxiliary ventilation through tubing. Operating rating with 5 hp motor is 6.5 in. maximum static pressure, and 6200 cfm free delivery volume. Weight is 340 to 475 lb and it may be furnished in open or permissible form. Circle No. 2 Heavy-Density Initial installation in the Mesabi Range country of the Wilmot-Daniels heavy-density concentrating system was a 175 ton per hour plant at the [ ] Skubic Bros. Virginia, Minn., operation. This Wilmot Engineering Co. unit has a separatory vessel providing unidirectional medium flow and as the only moving part uses a standard drag-line conveyor for lifting sink out of the bath. Circle No. 3 Portable pH Meter A low priced battery-operated portable pH meter of utmost simplicity announced by the Photovolt Corp. uses only 3 ordinary radio batteries which give over 2000 hours of service. Accuracy of 0.03 pH is claimed by the manufacturer for the model 125, and AC power line supply is available. Circle No. 4

Jan 1, 1952

By Y. J. Wang

A graphical technique by which the operating points for a two-fan ventilation system can be represented as the intersection of the modified fan curves is described. In constructing the diagram, the air quantities associated with the fans are considered to be independent variables and used as the axes of a rectangular coordinate system. The diagram may include, in addition to the modified fan curves, contour lines for resistances, pressures, and air powers. Procedures for drawing the diagram are discussed and illustrated with an example of the ventilation system.

Jan 1, 1986

By Lynn C. Jacobsen

Among the unforeseen consequences of the 1973 Arab oil embargo has been a considerable array of new or increased taxes on the so-called energy minerals. These taxes will be the subject of this report. Both Federal and State taxes have been enacted, but I will be concerned mostly with state severance taxes and particularly those on uranium. Severance taxes are considered to include all taxes having the distinctive feature of being applied on a natural resource at the stage of extraction. The tax may be based on units of production or on value, and if on values it may be on gross value or on gross value less either arbitrary or cost-related deductions. The tax has a number of aliases - resource excise tax, conservation tax, privilege tax, mining excise tax, ad valorem production tax, and more - and this makes comparison of tax burdens among states difficult. The windfall profit tax on oil is an example of a severance tax at the Federal level. Severance taxes are an established feature of state tax systems, but they continue to be a controversial issue, and proposals to raise or modify existing severance taxes are regularly submitted to the legislatures of the Western energy producing states. No concensus exists as to what is a reason- able and proper level of severance taxation or to the form it should take. The taxes which have been adopted by the various states reflect the interaction of a variety of interests and the specific circum- stances in each state. What follows is a summary of theoretical, practical, and emotional viewpoints and arguments that surface in any statehouse in which a severance tax bill has been introduced. The New Mexico experience will be heavily relied upon. THE ECONOMISTS Marginal effects. A severance tax which is based on a gross percentage of revenue or on units of production is a constant addition to variable costs, and to the mine operator has the same effect as any other increase in operating costs. The direction of these effects is straightforward: the tax will cause the property to have a lowered present value, to be mined at a lower rate than without the tax, raise the minimum grade that will be mined, lead to lower total recovery, make marginal properties sub-marginal and discriminate in favor of richer, more profitable operations (Lockner, 1965; Steele, 1967). In the short run, production facilities are fixed and imposition of a severance tax will have little effect on production levels. In the longer term, capital is mobile and investment and exploration expenditures will shift from minerals and jurisdictions with high taxes to those with low taxes. Over a considerable range of taxation the effect will be to change the relative position of the taxing state, but an overly optimistic evaluation of the capacity of mineral producers to absorb a tax can bring an industry to a halt. It is generally acknowledged that imposition of high severance taxes on taconite in Minnesota stopped development completely, and that only the adoption of a constitutional amendment limiting the amount of taxes that could be imposed in the future brought the firms back and encouraged them to make the huge investments required (Weaton, 1969). A tax which is a percentage of the net operating income (gross revenue less cash operating costs) does not influence the cut-off grade for recovery nor change the time preference for extraction, and hence, is free of the negative features of the tax applied to gross revenues or units of production. In theory it is a more efficient tax but relative administrative complexity and inherent difficulty in predicting revenue have discouraged its use. The Wyoming severance tax on uranium, which uses grade of ore as well as price in establishing taxable value, is the most cost related, and hence, the most neutral and efficient of the various state severance taxes on uranium. Economic rent. Despite the discrimination and the anti-conservation aspect inherent in most severance taxes, economists generally endorse their use because they are seen as a vehicle to appropriate rents - that is, returns greater than the long-run competitive supply price. Conspicuous examples of supposed economic rents are the returns to oil producers because of the OPEC cartel, the returns of the uranium producers under AEC buying contracts in the 19501s, and the high prices obtained by the uranium producers for contracts entered into in the 1976-1979 period. Mining of coal in the Western states is believed by some to generate huge economic rents because of the OPEC caused increase in price of a competitive fuel (McLure, 1978, p. 261), and possibly because of clean air regulations favoring the burning of low-sulfur coal. In theory, such surplus returns could be taxed completely away without affecting supply. In practice, the situation is more complex (Steele, 1967, pp. 234-236); economic rent of mineral production is an elusive quantity involving as it does replacement costs, and technical and market risk, and it, like beauty or pornography, probably exists mostly in the eye of the beholder. Rent may also be perceived to be present in the upper portion of a cyclic market which also has a downside. Where rent exists, it is almost certain to be short-lived - cartels self- destruct, government subsidies end, competitive adjustments occur - but the taxes imposed to capture it tend to be immortal. There is little doubt that the perception of un- usual and undeserved (obscene) profits in the mid- and late 1970's was a major factor in the adoption of energy mineral taxes strikingly higher than had been previously considered. At the New Mexico legislature of 1977 supporters of a moderate tax were repeatedly confronted with some variant of the statement, "You can't expect me to believe that a

Jan 1, 1982

By C. H. Li, R. J. Stokes, T. L. Johnston

A portion of the Ni3Cr-Ni3Al phase dzagram has been investigated, including the precipitation of 1 (Ni3Al) as well as the existence of ordered Y (Ni matrix), Extensive metallographic studies by electron microscopy have been carried out and X-ray diffraction diagrams have been taken at both elevated and ambient temperatures, No long-range ordering of the phase was found above 893°C (1639°F) in the compositional range investigated. The high rate of formation of the ordered ?1 phase upon quenching has been confirmed, a phenomenon which up to the present Lime has retarded the understanding of this phase diagram, Specimens with controlled amounts of ?1 exhibited up to a six-fold improvement in yield and creep strength compared with single-phase Ni-Cv-A1 alloys. MOST of the important high nickel heat-resistant alloys are related to the nickel-chromium-aluminum system. One of the important functions of the aluminum, often accompanied by titanium, is to produce a precipitate of the very fine ?1 phase (Ni3A1, X) where X may be Ti, Cr, or other elements. A number of investigators1-" have demonstrate the presence of y' in these alloys but most of their materials contained large amounts of other elements resulting in appreciable amounts of con- fusing phases such as carbides. Further clouding of the precise role of y' has been the suspected existence of an ordering reaction in the y matrix itself, ro-3,12-17 It appeared from these investigations that aluminum in Ni-Cr alloys would raise the ordering temperature of the matrix from 540°C at NisCr to 1300°C at Ni,Al. In support of this possibility, the matrix phase in the parallel Ni-Fe-A1 system is ordered to very high temperatures.1 OBJECTIVES OF THIS RESEARCH From this survey of the literature it appeared desirable to conduct an investigation of the simple Ni-Cr-A1 system using the alloys of the highest available purity to avoid the complication of foreign phases and thereby isolate the structures in the Ni-Cr-A1 system. Procedures were developed to study ? - ?o and ? - ?1 equilibria. Preliminary mechanical tests at elevated temperatures were also conducted.

Jan 1, 1962

By W. G. Matteson

In 1915, the State of California passed a law of great scope and importance. This law has been in successful operation for a year and may be briefly described as an act " establishing and creating a department of the State Mining Bureau for the protection of the natural resources of petroleum and gas from waste and destrucbion through improper operations in production; providing for the inspection of petroleum and gas wells; requiring all persons operating petroleum and gas wells to make certain reports" and providing the necessary officers and assessments to carry out the provisions of the act. The statute provides for a separate department of the State Mining Bureau, under the general supervision of the State mineralogist, with a staff composed of a "state oil and gas supervisor" and four deputies. It rules that all petroleum and natural gas wells shall be drilled, operated or abandoned under the supervision of the State supervisor, who shall order such tests or remedial work as seems to him necessary to protect the interests of property owners and the general public. It also provides for a board of arbitration to consider orders given by the supervisor which are not acceptable to the well owner. Section 18 of the act, which is the provision that is directly related to this paper, requires ('the owner of any well referred to in this act to keep a careful and accurate log of the drilling of such well," and further requires that this log shall show the character and depth of the formations passed through or encountered in the drilling, particularly the location and depth of the water-bearing strata; the character of the water encountered (so far as ascertained); whether the water was shut off, and, if solat what point; that it shall show completely the amounts, kinds and size of casing used; the depth at which oil-bearing strata are encountered; the depth and character of the strata, and whether all water was successfully and permanently shut off so as to prevent percolation or penetration into the oil-bearing strata. This log is to be kept in the local office of the owner or operator, subject to the inspection of the supervisor or any of his deputies at any

Jan 1, 1917

By M. R. J. Wyllie

Eight laboratory-prepared aqueous base drilling muds representing common mud types, and 15 aqueous base drilling muds sampled in the field, have been used in an experimental investigation of the relationship between the streaming potential developed across a mud filter cake and the differential pressure causing filtrate flow. It has been established that the relationship is of the form, ES = kPy, where Es is the streaming potential, P the differential pressure and k and y are constants for any particular mud system at constant temperature. Beyond a certain minimum thickness this relationship is independent of filter cake thickness. Experiment has shown that both k and y are temperature dependent parameters and that in certain mud systems there is a critical value of P above which the simple relationship Es = kPY ceases to hold. The constant k tends to be a function of the mud resistivity at 77ºF, but the exponent y has not been found to be related to any commonly measured mud property. Certain field experiments are described which serve to demonstrate that the total SP (self potential) developed opposite a formation may be quantitatively accounted for as the algebraic sum of an electrochemical potential and an electrokinetic potential. A chart to permit the simple use of mean solution activities in the interpretation of electrochemical SP data is given and its use described. Various field methods for computing the electrokinetic SP component of the total SP are considered and rejected as being unduly complicated and inaccurate. It is shown that the employment of low resistivity drilling muds is essential if optimum accuracy is desired in the use of the S.P. curve for the purpose of computing connate water salinities by the electrochemical SP method. The use of such low resistivity drilling muds is accordingly recommended. INTRODUCTION In a previous paper' a quantitative analysis of the electrochemical compovent of the SP (self potential) curve was made and it was shown that the electrochemical* emf, E, could be expressed as E = ZtRT/F In a,/a,, where t is the transference number of the chloride ion, R is the gas constant, T the absolute temperature of the formation water and mud, a, the mean activity of the connate water (assumed to be sodium chloride) and a, the mean activity of the mud (as sodium chloride). The essential accuracy of this expression was confirmed by an investigation 2 of the SP kicks opposite sands of known water salinity. The logs examined had been routine runs in oil wells in a number of Mid-Continent states. Further confirmation of the original analysis of the electrochemical SP is implicit in the paper by Tixier3 wherein a relationship between the SP and the ratio of connate water and mud resistivities, based only on field data, is given. Allowing for the fact that mud and connate water resistivities were used instead of activities, and that electrokinetic effects were ignored, the constant reported by Tixier is essentially 2tRT/F. The error involved in the universal substitution of resistivities for activities will receive further reference below. Possible reasons for the fact that the electrochemical properties of shales do not appear to be significantly dependent upon either the nature or the quantity of cation exchange materials, such as clays, they contain has been considered at some length by Wyllie and Patnode.4 In the same paper, the probable effects of shale thickness and compaction on electrochemical efficiency, and hence the inherent difficulty of obtaining reliable laboratory-scale data, were also pointed out. However, it is

Jan 1, 1951

By M. R. J. Wyllie

Eight laboratory-prepared aqueous base drilling muds representing common mud types, and 15 aqueous base drilling muds sampled in the field, have been used in an experimental investigation of the relationship between the streaming potential developed across a mud filter cake and the differential pressure causing filtrate flow. It has been established that the relationship is of the form, ES = kPy, where Es is the streaming potential, P the differential pressure and k and y are constants for any particular mud system at constant temperature. Beyond a certain minimum thickness this relationship is independent of filter cake thickness. Experiment has shown that both k and y are temperature dependent parameters and that in certain mud systems there is a critical value of P above which the simple relationship Es = kPY ceases to hold. The constant k tends to be a function of the mud resistivity at 77ºF, but the exponent y has not been found to be related to any commonly measured mud property. Certain field experiments are described which serve to demonstrate that the total SP (self potential) developed opposite a formation may be quantitatively accounted for as the algebraic sum of an electrochemical potential and an electrokinetic potential. A chart to permit the simple use of mean solution activities in the interpretation of electrochemical SP data is given and its use described. Various field methods for computing the electrokinetic SP component of the total SP are considered and rejected as being unduly complicated and inaccurate. It is shown that the employment of low resistivity drilling muds is essential if optimum accuracy is desired in the use of the S.P. curve for the purpose of computing connate water salinities by the electrochemical SP method. The use of such low resistivity drilling muds is accordingly recommended. INTRODUCTION In a previous paper' a quantitative analysis of the electrochemical compovent of the SP (self potential) curve was made and it was shown that the electrochemical* emf, E, could be expressed as E = ZtRT/F In a,/a,, where t is the transference number of the chloride ion, R is the gas constant, T the absolute temperature of the formation water and mud, a, the mean activity of the connate water (assumed to be sodium chloride) and a, the mean activity of the mud (as sodium chloride). The essential accuracy of this expression was confirmed by an investigation 2 of the SP kicks opposite sands of known water salinity. The logs examined had been routine runs in oil wells in a number of Mid-Continent states. Further confirmation of the original analysis of the electrochemical SP is implicit in the paper by Tixier3 wherein a relationship between the SP and the ratio of connate water and mud resistivities, based only on field data, is given. Allowing for the fact that mud and connate water resistivities were used instead of activities, and that electrokinetic effects were ignored, the constant reported by Tixier is essentially 2tRT/F. The error involved in the universal substitution of resistivities for activities will receive further reference below. Possible reasons for the fact that the electrochemical properties of shales do not appear to be significantly dependent upon either the nature or the quantity of cation exchange materials, such as clays, they contain has been considered at some length by Wyllie and Patnode.4 In the same paper, the probable effects of shale thickness and compaction on electrochemical efficiency, and hence the inherent difficulty of obtaining reliable laboratory-scale data, were also pointed out. However, it is

Jan 1, 1951

By R. G. Fenish

THE B-Ni system was chosen for this study because of the great interest being shown in boron-fiber-strengthened composite materials. Boron fibers were obtained from Texaco Experiment, Inc. They average 4.2 mils in diam with a 0.5-mil tungsten wire in the center. In order to make the diffusion couple, the fibers were included in the nickel matrix by electroforming. The samples were placed in a preheated furnace for the desired temperature and length of time. Sectioning and polishing the samples revealed concentric rings as shown in Fig. 1. The average penetration distance, X, was calculated by measuring the radius of the second phase (the white shell in Fig. 1) and subtracting the original radius. The second phase was identified as NiB by X-ray diffraction. This allows the kinetics of the formation of the phase NiB to be calculated by Eq. [I], which is taken from Hoffman:"

Jan 1, 1967

By J. B. Hess, R. L. Dietrich

IN the mechanical twinning of magnesium on the {1012} planes the crystallographic deformation is such that, in the direction of the hexagonal axis [0001], twinning is possible only under tension stress, while in the directions perpendicular to the hexagonal axis, twinning is possible only under applied compression. Thus in extruded magnesium and magnesium alloys where the extruded textures are best described as either [1010] or [ 1120] fibers,1 the basal planes are all nearly parallel to the extrusion axis and such material is susceptible to {1012 } twinning by compression in the direction of the extrusion axis. In order to explain the results of cyclic stressing in alternate tension and compression upon the tangent elastic modulus in such material, Dorn and Thomsen2 have postulated that, following twinning under applied compression, a retwinning or untwinning occurs as a result of residual microtensile stresses immediately upon removal of the applied compressive force. Recently, Carapella and Shaw3,4 have used this supposition of untwinning in magnesium in discussing their results on indentation hardness and on cold drawing of MI sheet. In trying to confirm this hypothesis by suitable direct experiments, the authors have been unsuccessful in detecting any evidence whatsoever that untwinning follows the release of applied compression and are forced to conclude that this hypothesis is improbable or, at least, that the quantity of material involved is small. For the experiments, small cylindrical specimens 0.040-in. diam. X 0.120- to 0.140-in. long were etched from 0.0625-in. extruded rod. The ends of the specimens were accurately faced off parallel in a jeweler's lathe. The compression jig was simply an ordinary set of micrometer calipers with an anvil interposed between the spindle and the specimen. The anvil was free to move axially but restrained from rotating so that the rotation of the spindle would not introduce a twisting stress on the specimen. With this arrangement the compressive strains could be estimated to 0.0001 in. and X ray pinhole photographs could be taken with or without load as required. Fig 1 is the pattern of an uncompressed specimen of AZ31 alloy, showing the approximate [1010] extrusion fiber. The X ray beam is normal to the extrusion axis; in this position it is particularly sensitive in detecting twinning if one directs his attention to the diffraction ring from the basal plane. Since twinning on {1012} planes produced an 86° reorientation of the crystal lattice, the original basal reflections occur at the 3 and 9 o'clock positions while the (0002) reflections from any twinned material will occur at the 6 and 12 o'clock positions. Fig 2 shows the same specimen compressed 3.0 pct, photographed while still under load. This strain has been just enough to produce a detectible amount of twinning and the sensitivity is roughly indicated by the fact that no alterations were produced in the intensities or maxima of the other diffraction rings. A strain of

Jan 1, 1948

By M. A. Scheil, S. L. Hoyt

About three years ago eight standard steels were prepared for the cooperative investigation of methods for oxygen analysis, sponsored by the Iron and Steel Division of the American Institute of Mining and Metallurgical Engineers and by the National Bureau of Standards. A preliminary report of the results was made at the annual meeting of the A.I.M.E. in February, 1936. † This report showed the reliability of vacuum-fusion methods and further brought out certain advantages of the fractional vacuum-fusion method. The results obtained by the authors with the latter method will be discussed here, with some comments on the procedure for those who are interested in determinations of gases in steel. Some additional comments are offered on the use of the polarizing microscope for identifying the inclusions in the steel to check and amplify the findings of the fractional vacuum-fusion analysis. For details of the fractional method, see the paper by L. Reeve1. Degassing the Crucible One of the sources of error in vacuum-fusion methods has been the blank gases evolved from the graphite crucible after preliminary out-gassing. We have used 1750" C. as the outgassing temperature. This gives a base pressure at that temperature of less than 0.030 mm. after one hour and of 0.004 mm. on dropping the temperature to 1575" C. At lower extraction temperatures the base pressure is 0.001 mm. at 1050" C., 0.002 mm. at 1170" and 0.003 mm. at 1320' C. Because of the size of our induction coil we are limited to this temperature, although it 'would be advantageous to use 1950" to 2000" C. Hamilton2, after outgassing at 1850" C. for 100 min., was able to reach a base pressure of 0.001 mm. for a temperature of 1700' to 1725" C. This would give a blank corresponding to less than 0.00015 per cent 02 and 0.00005 per cent H2. Chipman and Marshall outgas at 2000" C. for one hour by using a special construction

Jan 1, 1937

By K. L. Young

The general energy equation, including change in kinetic energy, was solved by numerical integration and used to evaluate simplifying assumptions and application practices over a wide range of conditions. When extreme conditions were encountered, sizable errors were caused by large integration intervals, application of Simpson's rule and neglecting change in kinetic energy. A maximum error of only 1.31 percent was caused by assuming temperature and compressibility constants at their average value. It was discovered that a discontinuity can develop in the integral for the injection case. This discontinuity indicates a point of zero pressure change and is an inflection point in the pressure traverse. INTRODUCTION When a pressure in a gas well is to be calculated, one of the first decisions is to select a method of calculation. In many instances, this selection becomes a problem because the literature, at best, provides an evaluation of any method for only a limited range of conditions. Once a method has been selected, a question often arises as to the size of the calculation interval which should be used. The question regarding calculation interval arises because an analytic solution is not obtainable and approximate solutions must be used. This paper presents an evaluation of major assumptions and application practices of probably the two most widely used methods for calculating steady-state single-phase gas well pressures. The two methods are Cullender and Smith1-" (numerical integration), and average temperature and com-pressibility. The Cullender-Smith method assumes that change in kinetic energy is negligible and is normally applied in two steps with a Simpson's rule correcton. The average temperature and compressibility method, in addition to neglecting kinetic energy change, asumes that temperature and compressibility are constant at their average values. This method is normally applied for wellhead shut-in pressures of less than 2,000 psi, and in one step. Computer programs were written to compute bottom-hole pressure with and without the assumptions, using various approaches. Values of input parameters investigated are shown in Table 1. Flow rate was limited to a maximum of 5,000 and 10,000 Mcf/D for tubing sizes of 1.610 and 1.995 in. ID, respectively. Flow rate was also limited to 10,000 Mcf/D for a tubing size of 2.441 in. ID when wellhead flowing pressure was 100 psia. These limitations were imposed on flow rate so as not to exceed sonic velocity. The z factor routine available necessitated limiting bottom-hole temperature to 240F and wellhead pressure to 3,000 psia. Pressures were compared on the basis of percent deviation from the trapezoidal integration of Eq. l or 2 at 100-ft intervals. A preliminary investigation indicated that a 1,000-ft interval solution would differ from a 50-ft interval solution by less than 0.25 percent; therefore, the 100-ft interval was chosen for a base. For the purpose of comparison, deviations less than 1 percent were considered insignificant. where 111.1 qeC2/d p = kinetic energy term. Eqs. 1 and 2 can be evaluated numerically at specific depths using the trapezoidal rule as shown by Cullender and Smith. If change in kinetic energy is neglected and temperature and compressibility are assumed constant at their average values, Eq. 1 can be integrated to give the average temperature and compressibility equation,

By J. R. Eickmeier

By R. L. Stone

None of the currently used methods of testing bentonites as binders for strengthening iron ore pellets is entirely adequate by itself. Since more knowledge was needed about 1) which properties of bentonite most affect pellet strength, and 2) the precise mechanism by which strengthening is produced, attention was paid to possible new techniques for rating bentonites. With the structural nature of bentonites — in particular, the montmorillonite component — the possibility of rating bentonites on the basis of zeta potential was investigated. These bentonites were also rated by conventional tests and measurements, including colloid content, barrel yield, pH, chemical analysis and physical tests on green and dry pellets. A mechanism for pellet bonding based on electro-kinetic forces between the bentonite and the iron ore concentrate appears to be feasible. In pelletizing, from 6 to 18 lbs of bentonite is added per ton of concentrate to give strength to the green and dry pellets. In some operations even more bentonite than is required for strengthening purposes must be added for moisture adsorption to pennit balling of the concentrate. Since bentonite is thus a major item in pelletizing, more knowledge about the way in which bentonites act as binders and better ways of rating this ability would help in the difficult job of selecting the right bentonite for a given concentrate. The fact of the matter is that although several methods are in current use for testing bentonites, none of these methods are consistently foolproof. For example, a given bentonite may rate high by several standard tests yet turn out to be a poor binder, and of course the reverse also occurs. Actually, more knowledge is needed about 1) which properties of bentonite most affect pellet strength, and 2) the precise mechanism by which strengthening is produced. In this study attention is therefore paid to possible new techniques for rating bentonites. With the structural nature of bentonites as a starting point, we investigated the possibility of rating bentonites on the basis of the zeta potential, i.e., the electrokinetic ootential on the montmorillonite colloids — the main component of bentonite binders. The zeta potential technique was applied to a range of commercial bentonites from several areas in the U.S. and abroad. These bentonites were also rated by conventional tests and measurements, including:

Jan 1, 1968

By R. Neilson M. E. Clark

(with map on plate I.) THE coal-beds of Canyon City are situated six miles below the town, upon the Arkansas River. At this point the Rocky Mountains have thrown out from their main ridge two spurs. The one to the north, containing Pike's Peak and Cheyenne Mountain, is known as part of the "Rim Range;" the one to the west and south is known as the `1 Green¬horn Range." Against these syenitic mountains, the later rocks are piled and uplifted; at right angles to the direction of this main uplift is the axis of a lesser plication. On the north, west, and south, the pitch is steep, gradually flattening as it approaches the centre of the basin and rising again to the east at a pitch of about 5°, thus forming a perfect basin, the centre of which is only three miles east of the base of the Greenhorn Range.

Jan 1, 1873

By Y. J. Wang

A critical path approach is presented for the problem of mine ventilation networks where regulators and fans are employed to control the airflow distribution. The problem is a classic one arising in mine ventilation planning. By identifying the analogy between the network for controlled flow and that for critical path method (CPM), the applications of the well known CPM technique to the ventilation problem become straightforward. The mathematical formulation of the problem is presented and the solutions are illustrated with examples. The cutset operation is introduced and employed for obtaining alternative solutions. The effects of booster fans on the total air power of the ventilation network are also discussed.

Jan 1, 1983

By H. A. Buehler

The Ozark region occupies a large part of the southern half of Missouri, the northern portion of Arkansas and comparatively smalll areas in northeast Oklahoma, southwest Kansas, and southern Illinois. It is a roughly elliptical plateau which has been deeply dissected by stream erosion, and which slopes imperceptibly into the prairie regions to the north, east, and west, but which terminates rather abruptly along the Arkansas River on the south and Tertiary lowland to the southeast. The Boston Mountains extending for a distance of some 200 miles (321 km.) along the Arkansas River rise to an elevation of 2000 ft. (609 m.), forming the most prominent topographic feature of the region. The so-called St. Frangois Mountains in St. Frangois, Madison, and adjoining counties in southeast Missouri, form a prominent but more restricted topographic feature, the highest point rising to an elevation of 1800 ft. (548 m.). The remainder of the region is largely a plateau area varying from 800 to 1500 ft. (243 to 457 m.) in elevation. Stratigraphy The region is underlain chiefly by sedimentary formations, which outcrop in roughly concentric bands around a comparatively restricted area of igneous rocks in the St. Frangois Mountain district. Although located geographically near the eastern edge of the Osarks, the St. Frangois Mountains have apparently suffered the greatest orogenic movement and the lowest formations of the succession are exposed in their immediate vicinity. The various sedimentary formations of the region do not show any considerable metamorphism and have suffered little change since consolidation. With the exception of a few basic intrusions in Ste. Gene-vievg County and a pegmatite dike in Camden County, Missouri, there is no evidence of igneous action, since the first sedimentary beds were deposited.

Jan 1, 1918

By H. E. Strauss

The short-time tensile-strength test, while it has not attained the practical importance of the creep test at elevated temperatures, has the advantage of being rapid and is satisfactory for determining relatire strengths. For platinum and its alloys, which frequently are used at high temperatures under ill-defined conditions, the short-time test provides useful data that aid in the selection of the most promising alloy for each use. Measurements have been made upon 13 alloys, using wire 0.0031 in. in diameter, the choice of alloys and of wire size being determined by the requirements of a practical problem. Later the measurements were extended to higher temperatures by the use of heavier wire, 0.010 in. in diameter. Apparatus The use of fine wire made the necessary equipment very simple, since no effort was made to measure the elongation. A small platinum-wound horizontal furnace was used, 1/2 in. in internal diameter by 1 ft. long, with the wire threaded through it. The wire, clamped at one end while the other ran over a ball-bearing pulley, of a total length of 29 in., was loaded directly by running sea sand into an attached basket, making the rate of loading and not of elongation constant. The sand flowed from a funnel, under a head of 3 in., into the basket 3 in. below the orifice, at the rate of 170 grams per minute. Pulley friction and bending resistance of the wire as well as the force of impact of the sand could be neglected, being 3 grams and 0.5 grams, respectively. Furnace temperature was uniform within ±5° C. over a length of 3 in., although a drift with time occurred, the largest amount being 20" C. No provision was necessary for a controlled atmosphere. In making the measurements, the furnace was brought to equilibrium before being used, and the temperature was measured with a platinum platinum-10 per cent rhodium thermocouple and a high-resistance pyrometer before and after all the tests at one temperature. The wire sample, after being threaded through the furnace and attached to the

Jan 1, 1940

By H. E. Strauss

The short-time tensile-strength test, while it has not attained the practical importance of the creep test at elevated temperatures, has the advantage of being rapid and is satisfactory for determining relatire strengths. For platinum and its alloys, which frequently are used at high temperatures under ill-defined conditions, the short-time test provides useful data that aid in the selection of the most promising alloy for each use. Measurements have been made upon 13 alloys, using wire 0.0031 in. in diameter, the choice of alloys and of wire size being determined by the requirements of a practical problem. Later the measurements were extended to higher temperatures by the use of heavier wire, 0.010 in. in diameter. Apparatus The use of fine wire made the necessary equipment very simple, since no effort was made to measure the elongation. A small platinum-wound horizontal furnace was used, 1/2 in. in internal diameter by 1 ft. long, with the wire threaded through it. The wire, clamped at one end while the other ran over a ball-bearing pulley, of a total length of 29 in., was loaded directly by running sea sand into an attached basket, making the rate of loading and not of elongation constant. The sand flowed from a funnel, under a head of 3 in., into the basket 3 in. below the orifice, at the rate of 170 grams per minute. Pulley friction and bending resistance of the wire as well as the force of impact of the sand could be neglected, being 3 grams and 0.5 grams, respectively. Furnace temperature was uniform within ±5° C. over a length of 3 in., although a drift with time occurred, the largest amount being 20" C. No provision was necessary for a controlled atmosphere. In making the measurements, the furnace was brought to equilibrium before being used, and the temperature was measured with a platinum platinum-10 per cent rhodium thermocouple and a high-resistance pyrometer before and after all the tests at one temperature. The wire sample, after being threaded through the furnace and attached to the

Jan 1, 1940