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By A. E. Boone

"The paper presents critical areas in which improved coordination of effort by industry, government and sup-pliers will be essential to continue the growth record of the Canadian mining industry into the 'seventies'. The analysis includes: exploration, production, mining methods, research and development, markets, management and industrial relations. Performance objectives are suggested where tangible results can be measured. The author suggests the methods by which the 'seventies' can be the greatest decade in the history of Canadian mining. It is indicated that a national mineral policy is essential to the Canadian mineral industry."

Jan 1, 1970

By Bert C. Morrison

In 1961. American Smelting and Refining Company was conducting exploration for lead in southeastern Missouri using several geophysical methods. Electrical methods were used in almost every hole drilled during this period. These methods met with only limited success, with one exception. This paper deals with that exception: An Electrical Potential Method used at a single hole to indicate direction to better mineralization. This method was notably successful in the program.

Jan 1, 1970

By A. J. Barry

A practical method has been developed and field tested which provides an estimate of the bearing capacity of mine roof and floor. The relationship between penetration of the strata and imposed loads is determined by in situ tests. Information of this type is needed to determine the maximum allowable pressure that may be applied by self-advancing supports on roof and floor of a longwall face without causing a punching type of failure.

Jan 1, 1970

By Peter Hood

Data on worldwide geophysical activity in mining exploration programs is collected annually by the Geophysical Activity Committee of the Society of Exploration Geophysicists as part of a continuing service to the industry. The data is obtained by sending out questionnaires to all organizations (which are) known to be carrying out mining geophysical work; the organizations canvassed include mining companies, contractors, government departments and universities. The questionnaire is divided into three sections, namely ground methods, airborne methods and research. In 1968, 515 questionnaires were circulated throughout the non-Communist world and 283 replies were received which is a 55% return. A 67% return was received from the U. S. organizations surveyed so the statistics quoted in this report for the United States are reasonably reliable. This report is published in condensed form, but with emphasis on the United States statistics, with the permission of the Society of Exploration Geophysicists. It was presented at the 39th Annual International Meeting of the SEG in Calgary, Alberta, on September 15, 1969. Worldwide utilization of mining geophysical methods reached a new high in 1968 with total expenditures of United States $41.4 million, compared lo $32.3 million in 1967, representing a 28%, increase. The expenditure distribution by area and type of activity is shown in the graph on page 64. In terms of money spent, ground geophysical surveys accounted for 49% of the total, airborne survey's 36% and research 15%. The percentage of the money spent on ground geophysical surveys fell by approximately 7% from 1967, that for airborne surveys, increased by 5%, and for research the amount increased by 2%. Industry accounted for 79°1% of the total monies spent on mining geophysical activity in the world in 1968 and governments and universities 21 o%.

Jan 1, 1970

By P. D. Hanson, H. Colijin

"New procedures and techniques are now available for the design of bulk storage bins. These new methods have essentially eliminated guesswork in the gravity flow of bulk solids, and have provided a sound basis for the quantitative analysis of alternate designs of hoppers and bins. This paper will discuss the practical application of the Solids Flow Theory (Jenike & Johanson) and illustrate the required design procedure with a few examples of actual bin operations."

Jan 1, 1970

The phrase "Total-Energy" has, during the past few years, become widely used to describe a wide range of very different operations. However, if accurately described they all have one basic factor in common - energy usage is optimised with the prime mover being powered by gas or oil to generate shaft horsepower and the products of combustion being put to some use. The item which distinguishes a Total Energy system from any other engine or turbine driven project is that orate pains are taken to utilize the waste heat, whether this be in the form of exhaust gases and/or engine jacket ling water. n areas where grid supplies of electricity are readily available, the economics of most projects undoubtedly hinge upon the successful application of waste heat. However, there has been a growing awareness of other benefits, such as reliability of supply, which can be incorporated into the system. In particular these factors sway managements of hospitals and companies with complex computer facilities to examine closely the feasibility of Total Energy, Consequently, in America for example, where many systems have proved themselves the list of applications is wide - shopping centres, apartment blocks, office buildings, airline terminals, universities, schools, motels. And these do not cover the industrial sectors where the range is wider. The total number in North America is now approximately 500 and this to some extent-speaks for itself. In Australia, the real work involved in carrying out feasibility studies for Total Energy is only just beginning. 'in some quarters, the concept is not well received in that it is too new. Therefore, a typical approach is to play safe and wait until some other company has proved its operation "under Australian conditions". This is certainly a realistic approach when considering something revolutionary but as far as Total Energy.is"concerned all the individual components and sometimes combinations, (engines, generators, boilers, air-conditioning units) have been in operation for many years. The only innovation is that they are now all being brought together under one roof. This should not be forgotten when the question "where can I see something like this operating?" is asked.

Jan 1, 1970

By B. A. Eaton

The subject of many discussions and technical papers in the last 20 years has been the prediction of the well-bore pressure gradients that are required to induce or extend fractures in subsurface formations. The subject merits this attention because of the frequently recurring problems that arise from an inability to predict fracture pressure gradients. Encountered in several common types of operations in the oil industry are problems associated with the prediction of formation fracture pressure gradients. When wells are being drilled in both new and old fields, lost circulation is often a very troublesome and expensive problem. Complete loss of circulation has been disastrous in some cases. Many times, such disasters could have been avoided if techniques for calculating fracture pressure gradient had been employed in the well plans, and if casing strings had been set, and mud weight plans had been followed accordingly. In areas of abnormally pressured formations, the prediction of fracture gradients during the well-planning stage is extremely important. In fact, it is as important as the prediction of formation pressure gradients, which has received a great deal of attention in recent years. There are several published methods used to determine fracture pressure gradients. However, none of these methods appears to be general enough to be used with much reliability in all areas. In 1957, Hub-bert and Willis published a classical paper that included the development of an equation used to predict the fracture extension pressure gradient in areas of incipient normal fau1ting.l Overburden stress gradient, formation pore pressure gradient and Poisson's ratio of rocks were the independent variables that were shown to control fracture pressure gradient, the dependent variable. In 1967, Matthews and Kelly published another fracture pressure gradient equation that is different from that of Hubbert and Willis in that a variable "matrix stress coefficient" concept was utilized.3 Later the same year, Costley wrote about a similar idea.5 Goldsmith and Wilson used a least-squares curve-fitting technique and field data from the Gulf Coast area to correlate fracture pressure gradient with formation pore pressure gradient and formation depth.' They noted that the fracture pressure gradient increased with increasing depth while the pore pressure gradient remained constant. In each of these cases, the problem for which a solution was sought was to determine the bottom-hole pressure gradient required to initiate or extend a fracture. Results of the previous work show that fracture pressure gradient is a function primarily of overburden stress gradient, pore pressure gradient, and the ratio of horizontal to vertical stress. There is argument for a fourth variable in that in many cases breakdown fracture pressure gradient is greater than the fracture extension pressure gradient. However, if the fracturing fluid is able to penetrate the formation through the pores or existing cracks, there is very little

Jan 1, 1970

By C. M. Romanowitz

This report deals with the factors which should be considered in evaluating a placer deposit and selecting a dredging system for mineral recovery. Overall dredging feasibility and the design of dredging systems are reviewed. Excavation methods, each with its advantages and disadvantages, are compared. Direct operating costs, both original and updated, of gold dredges with bucket capacities of 6 to 18 cubic feet are included. Costs vary with digging depth, changes in environmental conditions, and physical characteristics of the placer, all of which affect excavation rate and recovery. The costs, updated with appropriate indexes, should be used only as guidelines to evaluate potential dredging projects with similar characteristics. The relation of direct dredging costs to annual production is graphically illustrated by a family of curved envelopes that span dredge sizes from 2-112 to 18 cubic feet. A curve fitted to the data expresses the relation of direct costs to annual production for 151 dredge-years.

Jan 1, 1970

By Arcy P., D&apos Banister

Several gold-antimony geochemical anomalies were outlined near Stibnite, Idaho, using the humus sampling technique. Several hundred reconnaissance humus samples were collected and analyzed by a combination fire-assay atomic absorption method. The results partially outlined several gold-antimony anomalies and are very encouraging for further work in this part of Idaho.

Jan 1, 1970

By E. I. Gordon

The electronic pickup tube is the image-to-video signal-converter or transducer in tele vision-like systems. Images may relate to visible light or IR excitation as in conventional TV systems, X-ray excitation as in some medical and production control applications, or electron excitation as in electron microscopy. The latter process is also important in some forms of light or X-ray sensitive pickup tubes as an intermediate step. In virtually all of these devices the image ends up as a stored charge pattern on a suitable target electrode and the video signal is created by periodically scanning the target with a low energy electron beam and removing the stored charge. In a major group of tubes radiation induced conductivity creates the charge pattern. In others, photoemission is used. In this paper an attempt is made to illuminate some of the device requirements placed on materials exhibiting radiation induced conductivity, some of the materials and techniques that are used, and the problems. The emphasis will be on visible light and IR sensitive targets although some attention will be given to X-ray and electron imaging. Photoconducting films as well as diode arrays will be discussed. ELECTRONIC pickup tubes find their greatest use in commercial, entertainment television, and in industrial and educational closed-circuit television. Video telephone systems, such as AT&T's PICTURE-PHONE System will become eventually the greatest user. Military use is also very important. Nevertheless the use of electronic pickup tubes in technology, science, and medicine is assuming ever greater relevance and demands the greatest diversity and perfection in the pickup tube art. Commercial television and closed-circuit television use requires visible light response, high resolution, low lag, and uniform response. Video telephone use requires the same plus extreme reliability, stability, and low cost. Military use emphasizes, in addition, sensitivity, IR response, and ruggedness. (Devices for far IR response will not be considered here.) The use of pickup tubes in medicine and biology emphasizes UV response for microscopy, X-ray response for radiology, and energetic electron response for electron microscopy. Astronomy and nuclear physics demands low light level response, storage ability, and resolution (here the tube is a successful replacement for film). The interested reader might profitably read Advances in Electronics and Electron Physics, vol. 12,' 16,2 and 22A3 and 22B4 for detailed discussion of the use, properties, and technology of electronic pickup tubes. In general, because of the importance of these uses, none of the above properties will be ignored. Nevertheless attention will be restricted to only those imaging devices, called pickup tubes, using a scanning electron beam to dissect the image with a resulting video signal for conventional CRT display. However pickup tubes have become so complex that many of them include components such as image in-tensifiers which would be normally excluded by this restriction. Thus some of the other imaging devices will not be ignored entirely. We will first review the fundamental elements and physical phenomena involved in modern electronic pickup tubes, then the relevant materials and some of the material problems and then an interesting goal yet to be achieved. REVIEW OF PICKUP TUBE PRINCIPLES In all modern television systems using pickup tubes there is an interval called the frame interval, during which the incoming radiation flux is allowed to produce a cumulative effect in the form of a stored charge pattern which is a replica of the radiation image, and a scan interval during which the stored charge pattern is converted into a video signal. The frame interval bears no fixed relation to the scan interval and may be shorter or longer. In conventional, real time television the scan interval including retrace is identical to the frame interval. Integration and storage is the key to the sensitivity of modern pickup tubes, in contrast to earlier tubes such as the image dissector. At equivalent light levels and without integration, the number of photons contributing to the video signal in the image dissector is lower by a factor approximating the number of picture elements in the displayed image, a number of order 10. Statistical fluctuations in the number of contributing photons represent a serious limitation to the attainable signal to noise ratio, resolution and contrast. As a result considerably greater light levels have to be used then in targets which integrate over the full frame period. Thus the crucial elements, common to all modern pickup tubes, are the charge storage surface and the scanning electron beam which is incident on the charge storage surface at very low energy. These are shown in Fig. 1(a). The charge storage insulator is generally very thin with a thickness of several microns or less. The surface of the insulator is held near cathode potential. The backplate potential is held at cathode potential or at a small positive voltage relative to cathode. The combination of storage insulator and backplate electrode is commonly called the "target". In the absence of incident radiation flux the electron beam scans over the storage surface depositing negative charge uniformly over the scanned part of the surface by virtue of the fact that the effective secondary

Jan 1, 1970

By L. Leibowitz, M. G. Chasanov, L. W. Mishler

A drop calorimeter system is described for use in measuring enthalpies to 3600°K. Data are presented for tungsten between 2800" and 3600°K. The enthalpy of tungsten in cal per mole between 2000° and 3600°K can be represented by the equation HºT- Hº298 = - 1.7622 X 103 + 5.7772T + 8.9861 where T is in degrees Kelvin. A tabulation of com -puted values is presented for heat capacity, entropy, and free energy function. A drop calorimeter has been constructed to carry out enthalpy measurements at temperatures to 3600°K. Samples are heated by induction1 and dropped into a commercial adiabatic calorimeter, modified for this purpose. The experimental temperature is limited by the melting point of container materials and compatibility of the container and its contents. Several high-temperature drop calorimeters have been described in the literature1-5 but none has been used at temperatures as high as those in the present work; our measurements of the enthalpy of tungsten range from 2800" to 3600°K. DESCRIPTION OF EQUIPMENT An overall schematic view of the equipment is shown in Fig. 1. Power for the induction coil is supplied by a 25-kw 250 kHz Ther-Monic generator coupled to an iron core RF transformer. The Sample capsule is suspended in the work coil by 10-mil diam tungsten wires which are wrapped around a horizontal 5-mil diam tungsten wire. The horizontal suspension wire is clamped between two massive copper electrodes which are fixed in an x-y motion device that allows adjustment of the position of the heated capsule from outside the vacuum chamber. The copper electrodes are connected by flexible copper straps to a 1250-joule (5 kv, 100 pfarad) condenser bank. When it is desired to release the capsule, the condensers are discharged through the horizontal suspension wire causing it to vaporize rapidly. Very reliable and precise release of the capsule is achieved in this manner. Experiments have shown that no heat correction is required for this discharge energy. As part of the temperature measuring system, two prism holders have been incorporated in the apparatus. The upper prism holder is in the main vacuum chamber itself, whereas the lower one is in a side arm attached to the drop tube below the gate valve. The upper prism is mounted on a rotary vacuum feed-through, and may be moved under a protective shield when not in use. This prevents deposition of vapors on the prism surfaces when temperature measurements are not being made. Similarly, the lower prism is mounted on a push-pull vacuum feed-through, and when not in use may be pulled into its side tube. The prism mountings are fitted with guides and stops so that they may be moved precisely into the desired position. The aim throughout is to minimize the time the prisms are exposed to vapors from the hot samples. At the high temperatures reported in this paper, only the lower prism was used. The upper prism holder in these cases was fitted with an additional radiation shield. By using a prism and viewport, the lower surface of the samples can be observed by an optical pyrometer. The measurements discussed in this paper were obtained with a Leeds and Northrup 8622-C-S series manual pyrometer which is estimated to be accurate to 0.5 pct. Pyrometer calibrations and prism and window corrections were carried out in the conventional manner6 using tungsten strip lamps calibrated by the National Physical Laboratory, Teddington, England. Prism corrections were rechecked after each use. All work to date has been done in vacuum, and no measurable change has been observed in the prism correction below -2300°K for the upper prism and below -2800°K for the lower one. The total time of exposure of the prisms is about 50 sec per run. At high temperature, the final temperature reading is corrected by using the final A value for the prism; see Ref. 6 for details of this procedure. The calorimeter is a modified Parr Instrument Co. (Moline, lll.), Series 1230 adiabatic calorimeter with automatic jacket control. Other authors5 have used a similar calorimeter with good results. The calorimeter jacket cover and calorimeter cover are attached to the drop tube which contains a radiation shield. This shield is a gold-plated copper disc which can be operated manually from outside the calorimeter. The receiver is attached below the radiation shield and is lined with tungsten. In a typical experiment, the calorimeter and its jacket water temperatures were adjusted to 0.000°K temperature difference. The sample was allowed to equilibrate in the furnace at the desired temperature for about 20 min. The initial calorimeter temperature was then recorded, the sample dropped, and appropriate shutters closed. After about 3 min, the drop tube and receiver were filled with helium to 60 torr. The final calorimeter temperature was recorded after it had remained constant over a 5-min period. The equilibration time in the calorimeter was about 25 min. Thermistor probes are used to operate a hot and cold water supply system to maintain the jacket temperature equal to the calorimeter temperature. For actual measurements of the calorimeter temperatures, a quartz thermometer was used (Hewlett Packard Dymec Thermometer, Model #2801A). This thermome-

Jan 1, 1970

By M. C. Irani

This study is a survey of supply and demand for minerals, metals, alloys, and compounds used by the chemical industries in the Ohio River Basin (ORB) area of Ohio, Pennsylvania, and West Virginia during 1967. Data for the study were obtained from completed questionnaires received from chemical manufacturers and from interviews with officials of chemical companies and mineral producers and distributors. The information includes kind, quality, quantity, values, sources, specifications, uses, and methods of transportation. Results of the study show that of the total value of mineral materials consumed by the chemical industry, manufacture of inorganic chemicals consumed 46 percent; fertilizers, 22 percent; and soaps and detergents, 19 percent. Fifteen commodities accounted for 91 percent of the total value of mineral materials consumed. Five of these--phosphates, potash, salt, sulfur, and titanium dioxide--accounted for 59 percent of the total.

Jan 1, 1970

By C. D. Hall

This paper may be divided into two main parts: (1) analysis and data to show that Eq. 6 adequately correlates the authors' experimental data, and (2) the assertion that Eq. 20 "should permit scale-up with data taken from one pipe diameter for Newtonian, inelastic non-Newtonian, and viscoelastic fluids, such as dilute polymer fracturing fluids, which produce considerable pressure reductions." The authors might well recommend that this broad grouping of fluid types could be correlated by using Eq. 6 (requiring data from at least two pipe diameters). On the other hand, Eq. 20 is only shown to be adequate for conditions within the range of the present data set. Specifically, predictions by Eq. 20 for diameter scale-up to casing sizes would give larger deviations than implied in Table 2, and scale-up for some other fluids that give large drag reduction could be grossly in error. The description of a class of fluids "which produce a diameter family of straight parallel lines on a log (d?p/4L) vs log (8 v/d) plot. . ." defines a necessary condition for using Eq. 6; i.e., that s shall be constant for each fluid. The proposal that Eq. 20 is applicable to turbulent flow of such fluids is equivalent to saying that the spacing of these parallel lines, with A being constant, will be found to correspond to m = -1.20 for all such fluids. Table 1 shows the values of m derived from data on 16 non-Newtonian fluids. The key statement of this paper is that the diameter exponents "do not vary significantly from . . . -1.20." In statistical terms, this says that the m value for each fluid, which was obtained from all the measurements made on that fluid. has not been shown to be different from the arithmetic mean of the m values for the 16 fluids tested. This implies that the group mean, -1.20, is a more reliable value to use for an individual fluid than is the m value derived from the data on that fluid alone. No statistical test is described to support the key statement that the diameter exponents do not vary significantly from -1.20. Such a test would have to take into account that each individual m value is shown to correlate the pressure gradients for its fluid, with only about 3 percent standard deviation over the diameter range covered. That is, the m value is not the result of a single independent measurement. Thus, it would not be sufficient, or valid, to compare the deviation of one of the m values with the variance of the 16 values of m about their mean. An alternative interpretation of the key statement is that the diameter exponents do not vary appreciably from -1.20; i.e., that using -1.20 does not cause serious inaccuracy. Table 2 seems to be offered in support of such an assertion. However, such a statistical treatment (1) is unnecessary and (2) cannot lead to any valid scale-up generalization. The amount of error introduced by using a 1"wrong" value of diameter exponent — i.e., -1.20 instead of m — is determined by Eq. 6. The ratio of the pressures predicted by Eqs. 6 and 20 for scale-up from ds in small pipe to d, in casing is The pressure for 30-percent calcium carbonate slurry (m = -1.112) in 10-in. ID pipe would be predicted 30 percent higher by Eq. 6 than by Eq. 20, if based on tests in 0.5-in. ID pipe. The data set tested in Table 2 represents only a limited sample of pipe diameters (ratio of about 4:l) out of the population of diameters that would

Jan 1, 1970

By Mary H. Brown

The heats of formation of oxalic acid and sodium, potassium oxalates, and lithium oxalates were related by solution calorimetry to the heat of formation of (COOH)2.2H20, a value believed to be reliable as reported in the literature. The following heats of formation were determined: (COOH)2(a), -198.1±0.1; (COOH)2(ß), -197.8±0.1; UAW,, -328.7±0.4; Na2C204 -316.2±0.1; K2C204, -321.9±0.2; and K2C204-H20, -393.5±0.2 kcal/mole. The heat of the crystalline transformation (COOH)2(a) ? (COOH)2(ß) was determined to be 0.30±0.02 kcal/mole at 298.15° K.

Jan 1, 1970

By H. Stuart, L. Zwell, N. Ridley

specimen that was subjected to 700°C for 250 hr is shown in Fig. 2(c). The precipitates in this foil appear round and exhibit only very faint strain contrast. From this evidence, along with that described above for the symmetry of the strain field, it may be concluded that this coherent precipitate is spherical, which is generally the favored shape for coherent precipitates when the lattice parameter mismatch is small.12 These observations are consistent with the assumption that this precipitate is the y' (Ni3Al, Ti) phase. y' is known to be spherical in the early stages of precipitation. It is fcc and is similar in composition to the matrix and thus would have contrast similar to that of the matrix as do these precipitates. Direct identification of the spherical precipitate did not prove possible because of its low volume fraction and small size. The results of this investigation suggest that the increases in yield strength and the decreases in elongation observed in 45-Fe 30-Ni 20-Cr alloys containing about 0.4 pct A1 and 0.4 pct Ti on prolonged aging at 550" to 700°C are very likely due to the presence of a coherent, spherical precipitate, thought to be y'. Mi-crohardness measurements indicated that the precipitation of semicoherent M23C6 resulted in some matrix hardening. However, this precipitation process occurs much more rapidly than the changes in mechanical properties at these temperatures. 1C. L. Clark, J. J. B. Rutherford, A. B. Wilder, and M. A. Cordovi: J. Eng. Power, 1962, vol. 84, p. 258. 2 F. A. Comprelli and U. E. Wolff: USAEC Report GEAP-4745, General Electric Company November, 1964. 3C. N. Spalaris: A Monograph, USAEC Report GEAP-4633, General Electric Company, July, 1964. THERE have been many X-ray investigations of the room temperature lattice parameters of austenite which has been retained in quenched steels of various carbon contents. The results of these investigations have been collected by Wrazej,1 Wever et al.,2 and by Roberts3 and are included in Fig. 1 due to Pearson.4 The dashed line in Fig. 1 was considered by Roberts3 to most reliably describe the variation with carbon content of the lattice parameter of retained austenite. This line is given by the equation: a (Å) = 3.555 + 0.044 wt % C and recent unpublished measurements by one of the authors (LZ) support this relationship. The object of this communication is to draw attention to a relationship which describes the variation of the room temperature lattice parameter of 'equilibrium' austenite with carbon content, and which is different from that for retained austenite. The relationship a(Å) = 3.573 + 0.033 wt % C has been obtained from lattice parameter measurements made on equilibrium Fe-C austenites at elevated temperatures, which have been extrapolated to room temperature. The room temperature lattice parameter of 3.555Å which the Roberts' relationship gives for pure y-Fe is no: in agreement with the value of 3.573Å obtained when the high temperature lattice parameter data of Basinski et aL.5 and of Goldschmidt6 is extrapolated to room temperature. A linear extrapolation was

Jan 1, 1970

By G. L. Gates

Five possible sources of water for waterflooding of petroleum reservoirs in the arid San Joaquin Valley of California were considered. Three of them (water produced with petroleum, water from a shallow saline aquifer, and waste irrigation water) were analyzed chemically; laboratory information for one (sea water) had been developed during a previous study. A series of laboratory tests made on the fifth source (fresh water) determined the solubility of calcium sulfate dihydrate in water. Laboratory analyses included the following: Chemical analyses of water produced with petroleum and waste irrigation water; solubility of calcium sulfate dihydrate in water and brines; the effect of excess sulfate on the solubility of calcium sulfate in brines; the presence of sulfate-reducing bacteria; and the permeability of cores from a petroleum reservoir to air, to water from other petroleum reservoirs, and to waste irrigation water. The results showed that most of the waters and mixtures of waters are compatible with petroleum reservoir waters and are generally suitable for injection. The calcium content of some of the formation waters is quite high, and care must be taken to prevent precipitation of calcium sulfate dihydrate. The permeability of the few cores tested was about the same to water and brines as to air, indicating that formation damage due to clay swelling will not be serious. The waters most likely to be available for injection are water produced with petroleum, water from shallow saline aquifers, and waste irrigation water.

Jan 1, 1970

By Pedro Bolsaitis, Paul M. Sullivan

The activities of zinc in liquid Zn-A1 alloys in the temperature range of 1000' to 1160°K were determined by means of the isopiestic technique. The results are in reasonable agreement with the previous values determined by the radioactive tracer dew point method. Slightly negative excess entropies of mixing were found. The measured activities suggest that the a function for these alloys is not a constant, as has frequently been assumed, but is better represented by two straight line segments of different slopes. THE thermodynamic data of Al-Z alloys have been the subject of investigation by many authors. However, in the recent compilation of such data by Hult-gren et al.,5 the conclusion is reached that none of the previous measurements are reliable or consistent with each other. Since then two new sets of measurements have been reported,2, 8 both laying claim to good accuracies, yet showing very significant disagreement in the measured activity coefficients of zinc in Zn-A1 alloys and in the magnitude and sign of the excess entropies of mixing. Information on the thermodynamics of the system is of particular interest for interpreting results of the Bureau of Mines research on refining of zinc by distillation of die cast scrap. The present study was undertaken as an independent check on the recent values obtained from dew point measurements 8 and electromotive force measurements.' The isopiestic method, first introduced by Herasy-menko,' was chosen because it is one of the few thermodynamic techniques which, in principle at least, is carried out under perfect equilibrium conditions. The disadvantage of the method is that data are obtained at various random compositions and temperatures, which makes the interpretation somewhat cumbersome. The random errors arising from temperature gradients and fluctuations appear to be comparable to those of other techniques, as evidenced by the magnitude of the estimated uncertainties in the calculated integral thermodynamic quantities. An advantage of the method is that each run provides a relatively large amount of data; thus, it is less time consuming than those methods where samples of each composition must be measured individually. EXPERIMENTAL PROCEDURE The activities of zinc in liquid Zn-A1 alloys were measured by the isopiestic method which uses the principle of the tendency toward equilibrium of a series of samples at various temperatures under an imposed vapor pressure of the more volatile component (i.e., zinc, in this case). The basic apparatus is shown in Fig. 1. The small graphite crucibles that contained the metal samples were 15 mm ID and 13 mm deep with approximately 3 mm wall thickness. Each crucible was notched at the top and bottom to allow easy passage of vapor from one to another. At the beginning of an experiment each crucible was weighed on an analytical balance. Zinc and aluminum of spectrographic purity (99.999 pct) were then weighed into the crucibles. The amounts of each metal added were such that initial compositions varied above and below equilibrium values. One crucible contained only pure zinc. After weighing, the crucibles were stacked with the pure zinc on the bottom (corresponding to the lowest temperature in the furnace) and richest aluminum alloys at the top. The entire stack of crucibles was then placed in the silica glass container "E" which was then sealed under vacuum. Sixteen to twenty calibrated Chromel-Alumel thermocouples were attached by wire along the length of the silica tube, one or more adjacent to each sample.

Jan 1, 1970

By Roger J. Morrell

Disk-cutter experiments were performed on five rock types ranging in compressive strength from 9,000 psi to 27,000 psi. A specially constructed testing machine called a linear-cutter apparatus (LCA) was designed to load and traverse a free-rolling disk cutter across a sawed rock surface. The LCA was instrumented to measure the vertical and horizontal forces acting on the cutter during the run.. The ability of disk cutters to fragment rock was determined for both 60--degree and 90-degree cutting-edge angles, and relationships and regression equations were developed to predict cutter performance based on rock physical properties and applied forces,

Jan 1, 1970

By J. E. Udd, L. P. Geldart, B. B. Dhar

"Solutions for the stress distributions around simulated underground openings have been limited to calculations of boundary stresses for simple openings in which the boundaries may be expressed in mathematical terms. Studies involving circles, ellipses and ovaloids are re-ported in the literature.The stresses on the boundary of an opening and those at a distance from it in the medium are of concern to the engineer. The former may be related to the greatest concentrations of stresses encountered; the latter have a bearing on the identification of the ""zone of influence"" of the opening.Recent advances, in the form of a derivation for the stresses at a distance from an opening of elliptical shape, together with a solution derived previously for stresses in depth around ovaloidal openings, have been combined with computer programming techniques to provide complete solutions for a wide range of cases and variables. Some typical results which, it is hoped, may have some application to the design of underground openings are given herein."

Jan 1, 1970

By A. J. Baer

"DEFINITION OF THE REGION AND ITS BOUNDARIESTHE EXPOSED PART OF THE GRENVILLE PROVINCE is the southeastern part of the Canadian Shield, characterized by crystalline rocks with K-Ar ages of about 1,000 million years. Its Canadian portion is bounded on the southwest by Georgian Bay •and by Paleozoic sediments south of a line passing through Orillia and Kingston, on the southeast by the St. Lawrence River valley and the north shore of the Gulf of the St. Lawrence, on the east by the coast of Labrador and on the northwest by the Grenville front, a linear tec-tonic feature that is a metamorphic transition zone and/or a fault. Rocks located to the southeast of the front have younger K-Ar radiom€tric ages than rocks located to the northwest of it.The region is formed of complexly deformed and highly metamorphosed crystalline rocks and in part differs from other areas of the Canadian Shield by the presence of large amounts of crystalline limestone and bodies of anorthosite."

Jan 1, 1970