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By W. G. Cornwell, R. J. Hisshion

The development of a process for the treatment of telluride concentrates at Emperor Gold Mining Co. Vatukoula, is discussed. The concentrate is produced by flotation in cyanide solution immediately after milling. Two stages of cleaning are employed and a high-grade concentrate is produced usually containing more than 50% of the precious metal. The process developed in the first instance involved batch roasting followed by batch leaching in strong cyanide solution, recovering gold and silver only. The procedure currently employed is chemical oxidation of the tellurides using hypochlorite as the oxidant in a basic solution of a caustic soda and sodium carbonate. After oxidation the gold and silver are recovered by cyanidation. The residue is then leached with sodium sulfide and elemental tellurium precipitated with sodium sulfite.

Jan 1, 1977

By W. E. Horst

John Dasher (Central Research Laboratory, Crucible Steel Co. of America, Pittsburgh. Pa.)— Getting spodumene to float quickly and cleanly can be a problem. The author has presented an excellent account of a valid and useful approach to the scale-up of such problem floats. This indicated advantages for doubling retention time, i.e., buying another set of flotation cells. The author states that 21 pct of the spodumene floated in 2 min in the laboratory cell, that the grade of the rougher was about 75 pct spodumene, and that the final tailing contained 4 to 12 pct spodumene in different sizes with the present cells and 1 to 9 pct spodumene with twice as many cells. About 20 years ago, this writer obtained in the laboratory the flotation of over 90 pct of this spodumene in a King's Mountain sample in 1 min at a grade of 90 pct spodumene in the rougher and a final tailing that contained only 1 pct spodumene. The methods of Norman, Ralston," and Gieseke' were used, which teach that spodumene floats quickly and cleanly if its surfaces have been properly conditioned chemically and/or mechanically prior to flotation. Although feed preparation is not discussed, the results reported indicate that it is inadequate. This writer suggests that improvements in this area might be more effective than doubling the number of cells. W. E. Horst (author's reply)—Dasher's comments are appreciated by the author and require some clarification. He suggests that improved spodumene flotation performance may be obtained by feed preparation techniques rather than increased retention time in flotation. Certainly flotation performance is dependent on feed preparation and this is an important feature in the flotation process. It is true that certain types of spodumene ores, particularly weathered ores, require more complicated feed preparation processing than clean ores to achieve the desired flotation results. It was not implied that current feed preparation techniques are the same as experienced during the scale-up investigations. Although discussion of feed preparation was omitted from the article on scale-up relationships, the important feature was that pre-treatment processing was the same for each level of operation investigated— laboratory, pilot plant, and plant scale. Under these similar conditions large differences existed in recovery for comparable time intervals in each scale of operation. It is highly probable that feed preparation techniques could be modified and thereby increase the flotation rate for each scale or all scales of operation discussed. However, modifications would have to be justified on an economic basis.

Jan 1, 1960

MELTING in a hearth and in a basket is almost the same thing; charcoal and bellows are used for both. These are made large or small according to the quantity that you wish to melt, and more or less force of the bellows is applied according to the need. The hearth, bowl, or refinery, as the masters call it, is made with bricks and clay like a forge; opposite the middle of the tuyère a round hole is made like a wash- basin, wide at the mouth and narrow at the bottom where there is a hole for emptying it. A little iron plug is put in this so that it may be closed when necessary, or a piece of brick that is cut and pointed. Now, when this has been well covered all over with ashes, and the tuyère has been arranged so that the wind strikes the center, it is first filled with charcoal and baked very well so that the metal may be kept hot once it has been melted. When it has been baked, it is again filled with charcoal, fire is applied, and it is left to inflame gradually by itself. Then put one or

Jan 1, 1942

By T. B. Counselman

PRobably the earliest concentration of iron ore in this country was carried on in the northeastern magnetite areas. Magnetic concentration was relatively simple and gave a concentrate that, after agglomeration, and in spite of beillg high in phosphorus hecause of the dry concentrating methods then in use, was satisfactory blast-furnace feed. Production from the northeastern magnetitc area languished after the discovery and development of the Lake Superior ores, where there was seemingly an unlimited tonnage of high-grade ore, first the Michigan ores, and subsequently the still larger deposits of Minnesota. For years only the higher grade, direct shipping ores of the Lake superior district were mined. Those of Michigan, and of the Vermilion Range in Minnesota, were hard ores and came principally from underground mines. The softer ores of the Mesabi came partly from underground mincs, but mostly from the enormous deposits that could be worked by open-pit methods. The costs of ore from these open-pit deposits, even with the high initial cost of stripping, were so low that the underground mines of the Mesabi could hardly compete. The so-called Old Range ores, of Michigan and of the Vermilion Range of Minnesota, were hard and lumpy, and opened UP the burden in the blast furnace, therefore making possible harder driving with greater output. Also, some of these Ores were of such grade and physical characteristics that they were suitable for charge ore in the open hearth. These ores, therefore, commanded a price premium. and could compete with the softer, finer, but cheaper, Mesabi ores. The big tonnage reserves, however, are on the Mesabi. and it is these big open-pit deposits that contitue- our stock pile of iron ore, from which we are drawing so heavily during this war period. On the western end of the Mesabi the ore was found to be high in silica, and not suitable as furnace feed. As early as 1902, attempts were made to concentrate this so-called wash ore and by 1910 the first washing plant was put into operation. The Process was very simple, consisting essentially of a sizing and washing operation, with scalping screens, logwashers and tables, which later were replaced by classificrs. Ore particles finer than I00 mesh were deliberately wasted, because these fines were undesirable in the furnace. Fortunately, these tailings were impounded, and already are being reworked. Before long some of the low-grade ores began to require more elaborate treatment than the simple washing operation and, tables having been discarded because of their low capacity, in favor of classifiers, jigs were next introduced. These were able to discard coarser pieces of tailing than classifiers. Jigs are in active use today, various improvements having been made in their design and application. Various other machines and methods of concentration have been tried from time to time, and have in turn been discarded for more improved processes., The latest and most important process that has been 38

Jan 1, 1944

By T. B. Counselman

PRobably the earliest concentration of iron ore in this country was carried on in the northeastern magnetite areas. Magnetic concentration was relatively simple and gave a concentrate that, after agglomeration, and in spite of beillg high in phosphorus hecause of the dry concentrating methods then in use, was satisfactory blast-furnace feed. Production from the northeastern magnetitc area languished after the discovery and development of the Lake Superior ores, where there was seemingly an unlimited tonnage of high-grade ore, first the Michigan ores, and subsequently the still larger deposits of Minnesota. For years only the higher grade, direct shipping ores of the Lake superior district were mined. Those of Michigan, and of the Vermilion Range in Minnesota, were hard ores and came principally from underground mines. The softer ores of the Mesabi came partly from underground mincs, but mostly from the enormous deposits that could be worked by open-pit methods. The costs of ore from these open-pit deposits, even with the high initial cost of stripping, were so low that the underground mines of the Mesabi could hardly compete. The so-called Old Range ores, of Michigan and of the Vermilion Range of Minnesota, were hard and lumpy, and opened UP the burden in the blast furnace, therefore making possible harder driving with greater output. Also, some of these Ores were of such grade and physical characteristics that they were suitable for charge ore in the open hearth. These ores, therefore, commanded a price premium. and could compete with the softer, finer, but cheaper, Mesabi ores. The big tonnage reserves, however, are on the Mesabi. and it is these big open-pit deposits that contitue- our stock pile of iron ore, from which we are drawing so heavily during this war period. On the western end of the Mesabi the ore was found to be high in silica, and not suitable as furnace feed. As early as 1902, attempts were made to concentrate this so-called wash ore and by 1910 the first washing plant was put into operation. The Process was very simple, consisting essentially of a sizing and washing operation, with scalping screens, logwashers and tables, which later were replaced by classificrs. Ore particles finer than I00 mesh were deliberately wasted, because these fines were undesirable in the furnace. Fortunately, these tailings were impounded, and already are being reworked. Before long some of the low-grade ores began to require more elaborate treatment than the simple washing operation and, tables having been discarded because of their low capacity, in favor of classifiers, jigs were next introduced. These were able to discard coarser pieces of tailing than classifiers. Jigs are in active use today, various improvements having been made in their design and application. Various other machines and methods of concentration have been tried from time to time, and have in turn been discarded for more improved processes., The latest and most important process that has been 38

Jan 1, 1944

By K. R. Carson, J. Weertman

THE fatigue-hardening curve has received much attention in recent years. This curve is obtained by plotting the peak stress required to maintain a given plastic strain per cycle vs the number of cycles. It

Jan 1, 1969

By W. F. Hosford

A quantitative explanation is offered for the peculiar curled grain shapes found in the microstructures of drawn wires of bcc metals and compressed aluminum specimens. It is shown that once an [011] fiber texture is developed, the slip system are so oriented that further slip tends to produce plane strain rather than axially symmetric flow of individual grains. With plane -strain flow, however, compatibility of neighboring grains can be maintained only by a bending of grains about one another. PROBABLY the most obvious microstructural feature of heavily worked metals is the distorted shapes of grains. In the course of deformation, the shape change of each grain must be compatible with that of neighboring grains; otherwise holes would be formed at grain boundaries. In analyses of poly-crystalline deformation by Taylor and subsequent workers it was assumed that grain boundary compatability was maintained by each grain undergoing the same shape change as the polycrystalline aggregate in which it is imbedded. According to this assumption, when simple tension or compression is applied to a random polycrystal or to one with a fiber texture, each grain ought to deform with axially symmetric flow. Initially equiaxed grains should become cigar-shaped during wire drawing and pancake-shaped during compression. While microstructural observations of deformed metals are generally in accord with such a picture, certain striking exceptions may be noted. Peck and Thomas5'8 found that grains in heavily drawn tungsten, iron, and niobium (columbium) wires become shaped like ribbons curled about the wire axis, Fig. 1. At a suggestion from the author, they rationalized the development of these micro-structures by considering the orientation of the slip systems in the [011] texture formed by the wire drawing. It is shown in this paper that marked departure from axially symmetric flow of grains is also observed when polycrystalline aluminum is severely compressed. Again the explanation must lie in the orientation of the slip system in the [011] texture, which is formed in fcc metals by compression.' THEORY A simple quantitative argument will be presented to show that the development of these microstructures is a result of flow on the combination of slip systems for which the minimum amount of mechanical work is expended in producing a unit tensile (or compressive) strain. First it must be realized that the macroscopic strains of a crystal resulting from slip are given by: where d dy, and dc, are normal strain increments parallel to the x, y, and z reference axes; are crystallographic shear-strain increments on slip systems

Jan 1, 1964

By T. S. Lundy

Anand and Agarwala recently determined diffusion coefficients by the residual activity (Gruzin) method for several tracers in large-grained, high-purity aluminum. D values at any particular temperature in the range of 400" to 630°C were about four orders of magnitude lower for cd115, 1n114, sn113, and pdlm than for Ag. Corresponding values for Do and Q in the Arrhenius equation were also quite small. It was pointed out previously that unusually low diffusion coefficients within the region of a specimen near a free surface may be the major cause of such anomalous results for impurity diffusion in silver and in aluminum.44 Anand and Agarwala considered this possibility but rejected it because their penetration profiles were "homogeneous" and "yielded diffusion coefficients obeying the Arrhenius plot". Neither of these two criteria satisfactorily prove or disprove the presence of a near-surface effect. Such can be accomplished only by direct serial sectioning in which the chips ground from the specimen are assayed for tracer content. In fact, such experiments always should be done prior to use of the somewhat indirect Gruzin method where the finer details of the transport process cannot be determined. There have been several other reports of unusually low D, Do, and Q values for impurity diffusion in silver and aluminum.1"4 It is interesting to note that all of these studies made use of the Gruzin method. Also, in all cases where the same systems were examined by use of a direct serial sectioning technique, large near-surface effects were observed. One must conclude therefore that the reported anomalous diffusion parameters for cd, In114, sn113, and pd in aluminum are due to some near-surface effect, while the results for Agl10 indicate that no such effect was encountered for this system.

Jan 1, 1969

By M. E. V. Plummer, F. E. Beamish, J. C. Hole, J. M. Kavanagh

Prior researches have shown that the iron-copper-nickel content of platinum concentrates may be reduced by carbon to form a collecting alloy for the platinum metals in a manner exactly analogous to the formation of the lead fire assay button. The nature of the iron-copper-nickel alloys with the platinum metals has been investigated. Palladium and probably some of the other platinum metals form solid solutions with this alloy. ONE of the greatest known reserves of the platinum metals is to be found in the nickel, copper, iron sulphide deposits of Northern Ontario. The very large tonnage of copper-nickel ore processed makes the Sudbury district a significant world source of the platinum metals, the latter being recovered as byproducts in the electrolytic refining process for copper and nickel. Chalcopyrite, pentlandite, and pyrrhotite are carriers of the platinum metals;' these minerals contain from 0.03 to 2.0 ppm of the noble metals. The analysis of the above ores for the platinum metals necessitates an initial concentration of the minute quantities present in the ore. The method usually employed involves the extraction of the noble metals by molten lead with or without small proportions of silver. The lead is then separated from the precious metals by cupellation, a process which involves absorption by the cupel and volatilization of lead oxide, leaving the precious metals collected in a silver bead on the surface of the cupel. The collection by lead is probably achieved by a process of dissolution followed by some degree of segregation in the lead alloy since the cold button is seldom uniform in composition. With silver-lead alloys this process of liquation has been used to re- cover pure lead since, during the cooling period, crystals of pure lead separate and silver becomes concentrated toward the center of the solid.' Platinum and gold liquate in a manner similar to silver which may account for the successful recovery of platinum by fire assay even though it is considered insoluble in a solid lead medium. 3 In the case of iridium the liquation process may be a disadvantage in that the iridium may appear in the outer areas of the button and thus be lost mechanically during the handling processes. In any case the deficient alloying characteristics of lead for the platinum metals encouraged attempts to find an improved collecting alloy, and by analogy with aqueous extractions, preferably one in which solid solutions would be readily formed. Since, beyond a certain minimum solute to solvent ratio, the formation of a solid solution is accompanied by a lattice distortion, one would expect some relationship between the atomic diameters of any two metals and their tendency to form a solid solution. In one survey5 the hypothesis was put forward that when the atomic diameter of the solute differs by more than about 15 pct from the solvent, the "size factor" is unfavorable and the formation of a solid solution is restricted. On the other hand, when the atomic diameters are within this limit the size factor is favorable and solid solutions are readily formed, e.g. the transition metals of Group VIII having similar radii form solid solutions over wide ranges of composition.6 Even with a favorable size factor, elements having different crystal structures cannot form a continuous series of solid solutions. Cell dimensions alter as the concentration of the solute increases, causing a

Jan 1, 1962

By William Kent

About a year ago, the writer had occasion to assist Mr. John L. Gill, Jr., of the Pittsburgh Car-wheel Works, in malting a trial of his new testing machine. A piece of Bessemer steel, of about .34 carbon, was used as a test-piece, turned to a sectional area of one square inch for a length of five inches between shoulders, and provided with large round heads, which were fitted to what is called the " Wade grip." Measurements of elongation, accurate to 1/10000 of an inch, were made by a special apparatus containing two micrometer screws, with electric contact attachment. The machine was operated by hand-power. Readings of elongation were taken at each increment of 2000 pounds stress per square inch, up to 44,000 pounds, the elongation corresponding to the latter figure being .0085 inch. The elongations up to this point remained almost exactly proportional to the stresses, the strain diagram, as shown on the Plate, from the origin to the point A, being a straight line (the deviation of no observation from the straight line being greater than .0002 inch). There being no indication of an approach to the elastic limit, the attendant at the hand-wheel and scale-beam wits told to proceed as usual and move the poise forward 2000 pounds, or to 46,000, and turn the wheel until the beam was balanced. Noticing that the beam did not rise in the usual time, and that the elongation was increasing rapidly, the writer called to the attendant to stop turning the hantl-wheel and to push the poise backwards until the scale-beam balanced. Instead of balancing at between 44,000 and 46,000 pounds, as was expected, it balanced at 40,000 pounds, and the elongation had increased to .0343 inch (or more than four times that recorded at 34,000 pounds), as plotted at the point B, the dotted line between A and B showing the supposed course of' the strain diagram between these two points. Immediately upon recording the elongation the writer said to Mr. Gill, who was standing alongside: "This phenomena is without a parallel in my experience, and I know of but one way to account for it. The piece. must actually be broken in its interior, through a flaw or weak portion of the metal. The test-piece is now equivalent to a tube, with

Jan 1, 1880

By Harold S. Morgan

INTRODUCTION The Waste Isolation Pilot Plant (WIPP) is being developed in southeastern New Mexico by the United States Department of Energy as a research and development (R&D) facility to demonstrate the safe disposal in salt of radioactive wastes resulting from defense activities. As part of the WIPP R&D program, a series of in situ tests will be performed to determine the behavior of drifts and storage rooms in the creeping salt medium (Matalucci, et al. 1982). Data obtained in these tests will be used to evaluate and improve numerical models used to compute the structural response of these drifts and rooms. Stress has been proposed as one of the parameters to be measured in the tests, and borehole inclusion stressmeters have been included in the instrumentation package. Cages of this type provide an indirect measurement of stress change in that they actually monitor borehole displacements which are then related to changes in the in situ stress away from the borehole. The relationship between stress and displacement is highly dependent upon the constitutive behavior of the rock in which the gage is emplaced. This relationship is well understood for rocks with linear stress-strain behavior (Fossum, et al, 1976), but, for creeping rocks like salt, the relationship has yet to be determined. Thus, inclusion gage response in salt must be investigated fully before stress measurements from the WIPP in situ tests can be used for comparisons with computed stresses The calculations presented in this paper were performed as part of an investigation of inclusion stressmeter performance in salt. They focus on the strain gaged stressmeter (SGS) (Cook and Ames, 1979) and on a hypothetical solid cylindrical inclusion with variable stiffness Issues addressed include the effects of creep and the effects of gage stiffness on stressmeter output for various loading conditions. The

Jan 1, 1984

By S. L. Crouch, C. Fairhurst

The general term "coal mine bump" refers to the sudden and violent failure of in-situ coal. Coal bumps occur in most countries where coal is worked by underground methods. They are related to geological factors and mining techniques. Coal bumps can be characterized as unstable releases of energy associated with yielding that occurs with progressive mining. Unstable releases of energy occur when the coal is able to absorb less energy than is released by the surrounding rock mass during the yielding process. At any stage of mining, the amount of excess energy so released is governed by the mining geometry, the overburden stress, the elastic properties of the rock mass, and the stress-strain characteristics of the seam material. If the coal in the vicinity of the working face is crushed, the peak abutment pressure occurs at some distance into the intact portions of the seam, and mining takes place in essentially destressed coal. With subsequent mining, additional yielding occurs, excess energy may be released, and the peak stress is again shifted into the solid. This process continues until the mining geometry is such that the zone of peak stress is effectively surrounded by yielding coal, at which point it can be anticipated that further mining will produce dramatic redistributions of stress and be accom¬panied by large releases of energy. On this basis, the differences between several alternatives for mining a given block of coal may be pronounced.

Jan 1, 1975

By N. A. MacLeod

Ball wear in wet grinding mills has been the subject of considerable discussion in the last few years. Its importance to millmen is obvious in view of the fact that ball wear may cost from 2 to 4 per ton of ore for the more fortunate operators and many times this cost when a refractory ore must be reduced to a fine state of comminution. Consequently, any factual information that may be obtained on the nature of ball wear may be applied to introduce changes leading to lower ball consumption and therefore also to lower costs. In 1940, while employed with the Britannia Mining and Smelting Co., Britannia Beach, B.C., I had occasion to investigate factors that might affect ball consumption. We performed a number of tests, which will be briefly described. These tests originated as a result of changing from a 3½-in. ball to a 2-in. ball of different type of manufacture and were motivated by the desire to obtain the best possible type of 2-in. ball. Our testing was helped by the fact that the company operated a one-ton electric furnace, so that it was quite easy to make steel changes. It should be emphasized at the beginning that these tests produced results that in their general application to milling should be interpreted qualitatively rather than quantitatively. As will be evident in the description of the method used in testing, the balls were subjected to an intermittent batch grinding treatment, which may have produced results in rate of steel wear that may not have an accurate correlation with steel consumption in full scale mill operation. However, with this bed and rather arbitrary method of testing, results were obtained that may be of some interest and may stimulate further work on this subject. Unfortunately, owing to pressure of war work, our tests, which we had intended to repeat on a continuous grinding operation, had to be discontinued. Method of Testing Tests Were made in a Small cylindrical mill, rotating at 72 r.P.m. Internal dimensions of the mill were 10½-in. dia. by 9 in. The cylindrical inner surface was lined with rubber and the two ends were formed by steel plates. A charge of 2000 grams dry feed and 2000 C.C. of water was added evev 2 hr., the mill being drained of pulp before the addition of each charge, by tilting and sluicing with water. The mill was run On afternoon and night shift for daily periods of about 15 hr. total grinding time, and each test lasted from 60 to 150 hr. This batch method of testing involved a higher average pulp temperature in the mill, which undoubtedly affected comparative results in Some of the tests. Hardness oF Ball vs. Wear In these tests, special "eutectoid" steel balls were used, some of which were chill-Cut and quenched, some sand-cast and quenched, and some sand-cast and annealed to a dead soft condition. The results obtained, using as mill feed an ore containing considerable free quartz and

Jan 1, 1947

By N. A. MacLeod

Ball wear in wet grinding mills has been the subject of considerable discussion in the last few years. Its importance to millmen is obvious in view of the fact that ball wear may cost from 2 to 4 per ton of ore for the more fortunate operators and many times this cost when a refractory ore must be reduced to a fine state of comminution. Consequently, any factual information that may be obtained on the nature of ball wear may be applied to introduce changes leading to lower ball consumption and therefore also to lower costs. In 1940, while employed with the Britannia Mining and Smelting Co., Britannia Beach, B.C., I had occasion to investigate factors that might affect ball consumption. We performed a number of tests, which will be briefly described. These tests originated as a result of changing from a 3½-in. ball to a 2-in. ball of different type of manufacture and were motivated by the desire to obtain the best possible type of 2-in. ball. Our testing was helped by the fact that the company operated a one-ton electric furnace, so that it was quite easy to make steel changes. It should be emphasized at the beginning that these tests produced results that in their general application to milling should be interpreted qualitatively rather than quantitatively. As will be evident in the description of the method used in testing, the balls were subjected to an intermittent batch grinding treatment, which may have produced results in rate of steel wear that may not have an accurate correlation with steel consumption in full scale mill operation. However, with this bed and rather arbitrary method of testing, results were obtained that may be of some interest and may stimulate further work on this subject. Unfortunately, owing to pressure of war work, our tests, which we had intended to repeat on a continuous grinding operation, had to be discontinued. Method of Testing Tests Were made in a Small cylindrical mill, rotating at 72 r.P.m. Internal dimensions of the mill were 10½-in. dia. by 9 in. The cylindrical inner surface was lined with rubber and the two ends were formed by steel plates. A charge of 2000 grams dry feed and 2000 C.C. of water was added evev 2 hr., the mill being drained of pulp before the addition of each charge, by tilting and sluicing with water. The mill was run On afternoon and night shift for daily periods of about 15 hr. total grinding time, and each test lasted from 60 to 150 hr. This batch method of testing involved a higher average pulp temperature in the mill, which undoubtedly affected comparative results in Some of the tests. Hardness oF Ball vs. Wear In these tests, special "eutectoid" steel balls were used, some of which were chill-Cut and quenched, some sand-cast and quenched, and some sand-cast and annealed to a dead soft condition. The results obtained, using as mill feed an ore containing considerable free quartz and

Jan 1, 1947

By E. Brunner, E. S. Mardock

A method of measuring oil saturations in cores or sand packs by neutron scattering is described. This method permits local SatUrations to be measured in a core enclosed in a steel pressure vessel without interrupting the flow. calibration data and a saturation distribution measurement obtained with the apparatus are included by way of illustration. Introduction In laboratory flow experiments designed to study the mechanism of oil production it is frequently necessary to measure the oil saturation in a core or sand pack containing Oil, gas, and perhaps brine. It is sometimes desirable that the saturation measurement refer to a relatively small portion of the core, so as to eliminate end effects; that it be made without interrupting the flow, and that it be applicable to a core enclosed in a steel Pressure vessel capable Of withstanding the Pressures encountered in petroleum reservoirs. None of the usual methods of measuring saturation meets all Of these requirements. To measure the gas saturation by observing the apparent compressibility of the gaseous Phase1 would require the interruption of the flow and would give an average saturation for the whole core. An electrical conductivity method is available for measuring brine saturations,2,3 but it is not applicable to oil. A radioactive tracer might be used if a suitable substance could be found that would dissolve in the oil, emit gamma radiation, and not be adsorbed on the sand, the steel core holder, or in an aqueous- phase. The large gamma-ray background from the mass of radioactive oil in other parts of the apparatus might, however, be undesirable. There remain for the saturation measurement methods involving the absorption or scattering of some penetrating radiation produced outside the apparatus. It might be possible to use X-rays or gamma rays; but these radiations would be so much less strongly absorbed and scattered by the oil than by the steel walls of the core holder and by the sand that it seems doubtful that much precision could be attained. In a beam of neutrons, however, there is a radiation that is very penetrating and, moreover, its scattering by substances containing hydrogen, such as oil, is qualitatively different from that occasioned by other materials. It would seem possible, and has proved to be quite practicable, to measure oil saturations accurately under the required conditions by means of neutron scattering. The first, to our knowledge, to suggest neutron scattering as a means of measuring oil saturation were F. Brans and ,. A. Bottema,4 of the Amsterdam laboratories of the Bataafache Petroleum Maatschappij, who made a few preliminary experiments to test the method while they were engaged in exploring the possibilities of neutrons for well-logging purposes. A comprehensive account of neutrons and their behavior will be found, together

Jan 1, 1946

By E. S. Mardock, E. Brunner

A method of measuring oil saturations in cores or sand packs by neutron scattering is described. This method permits local SatUrations to be measured in a core enclosed in a steel pressure vessel without interrupting the flow. calibration data and a saturation distribution measurement obtained with the apparatus are included by way of illustration. Introduction In laboratory flow experiments designed to study the mechanism of oil production it is frequently necessary to measure the oil saturation in a core or sand pack containing Oil, gas, and perhaps brine. It is sometimes desirable that the saturation measurement refer to a relatively small portion of the core, so as to eliminate end effects; that it be made without interrupting the flow, and that it be applicable to a core enclosed in a steel Pressure vessel capable Of withstanding the Pressures encountered in petroleum reservoirs. None of the usual methods of measuring saturation meets all Of these requirements. To measure the gas saturation by observing the apparent compressibility of the gaseous Phase1 would require the interruption of the flow and would give an average saturation for the whole core. An electrical conductivity method is available for measuring brine saturations,2,3 but it is not applicable to oil. A radioactive tracer might be used if a suitable substance could be found that would dissolve in the oil, emit gamma radiation, and not be adsorbed on the sand, the steel core holder, or in an aqueous- phase. The large gamma-ray background from the mass of radioactive oil in other parts of the apparatus might, however, be undesirable. There remain for the saturation measurement methods involving the absorption or scattering of some penetrating radiation produced outside the apparatus. It might be possible to use X-rays or gamma rays; but these radiations would be so much less strongly absorbed and scattered by the oil than by the steel walls of the core holder and by the sand that it seems doubtful that much precision could be attained. In a beam of neutrons, however, there is a radiation that is very penetrating and, moreover, its scattering by substances containing hydrogen, such as oil, is qualitatively different from that occasioned by other materials. It would seem possible, and has proved to be quite practicable, to measure oil saturations accurately under the required conditions by means of neutron scattering. The first, to our knowledge, to suggest neutron scattering as a means of measuring oil saturation were F. Brans and ,. A. Bottema,4 of the Amsterdam laboratories of the Bataafache Petroleum Maatschappij, who made a few preliminary experiments to test the method while they were engaged in exploring the possibilities of neutrons for well-logging purposes. A comprehensive account of neutrons and their behavior will be found, together

Jan 1, 1946

IN my opinion antimony* is a composition made by Nature to create a metallic mineral that is overflowing with an undue proportion of hot and dry material and with its moisture poorly mixed, with an effect wholly contrary to the composition of metals. Therefore, it comes to be, like quicksilver, a mineral deformity and monstrosity among metals. Or it might be a material that is about to reach metallic perfection, but is hindered from doing so by being mined too soon. I am persuaded to this opinion by seeing in it so many parts similar to those of metals, considering first its clear and brilliant color and its great weight and then the regulus† that it leaves at the bottom of the vessel on melting. Obviously it has in it much earthiness, as is attested by the odor of its sulphurous burning, its imperfect blending, its defective mixture, its difficult fusion, and finally the character of its regulus, for although this is very white and almost more shining than silver, it is much more brittle than glass. [28] The practical philosophers make great use of it in their alchemistic work in order, they say, to make an oil that they believe gives the color of gold to fixed silver. For this reason many of them hold it in high repute, especially the kind that has long thin fibers like a bundle of bristles. And they say that they can obtain greater results with it than with sulphur. I believe this, however, in case it is aided by sulphur, since it is nearer the metallic species than sulphur is. This I know for a certainty because I have seen them extract from it a bloody liquor in the form of an oil. The alchemist who made that which I saw told me that it had not only the

Jan 1, 1942

ALTHOUGH I have already described to you the procedure for making assays of the ores (a thing that is not very different from what I wish to describe in the present chapter), I shall repeat it in substance, with the addition of the method of assaying gold, in order to tell you certain rules for weights which are very necessary to know, and above all in order to demonstrate to you the method of refining a small quantity of silver by the use of a cupel, and in order to tell you how there are (I find) only two ways that are customary for bringing silver to fineness. One is that of the cupel [copella] and the other is that of the cupeling hearth [cenneraccio], one for a small and the other for a large quantity. But although they are called by two names and appear to be two methods, the aim and the procedure of both is actually the same. Nor do I know of other difference between them than the carrying out of the method and the large or small quantity. Cupeling is a very useful thing for anyone who handles gold or silver to know. Indeed it is necessary, because it not only throws light on the work that is to be done but it also shows the truth [55] and the correct weights in large quantities. It is a quicker and easier way of bringing the work to the desired perfection than is afforded by the method for large quantities. Therefore, as you have heard, it is used in making assays in order to know exactly what quantity of the substance of silver or gold is in copper and lead or in ores, as well as in that melted material which remains among the charcoal and ashes. In short, it is the measure by which you have the certainty and safety of knowing that you have not been deceived by art or by your workmen, who had no other interest than their simple wages. Many workmen are found who are so untrustworthy that they no sooner get control of a thing than they think up some fraud, and even though some know that they must give an accounting they do not restrain themselves, although sometimes they would perhaps act with greater security and more deception than they do if they did not fear detection. For, truly, since silver is a valuable thing and every bit is worth much, a man should not enter into refining it with closed eyes. If for no other reason this pro-

Jan 1, 1942

By Sidney H. Haughton

FOLLOWING the discovery of diamonds in 1870 and the Witwatersrand gold fields in 1886 South Africa changed from a predominantly pastoral country with a scattered white population into a land whose economy came rapidly to be based primarily on mining. The total value of the mineral output of the Union in 1944 was approximately $493,000,000, to which gold contributed 84 per cent. Gold furnished some 33 per cent of the Union Government's total revenue in that year, and approximately half the country's population obtained its livelihood directly or indirectly from the gold mining industry. In any review of the Union's mining activities and in any consideration of the country's future, gold mining must occupy a prominent place. It is generally conceded that the present structure is not properly balanced and that an economy based on a preponderance of a single nonpermanent factor possesses potentialities of serious instability.

Jan 1, 1946

By MAGNE MORTENSON

IN laboratory work and industrial tests it is important to set forth the results of research, clearly. This is generally achieved by means of some form of diagram or graphical illustration. The most common form for such graphs of flotation research is a simple chart with two curves for percentage and recovery of the concentrate. This may be quite useful, especially for minerals which may be floated: by means of one reagent in variable and another in constant amounts. If both reagents are used in variable quantities the process may be illustrated by means of several diagrams, .keeping one reagent constant in each series of tests. A more useful form of diagram for a. system with two variable - components (reagents) may be established by drawing a chart with the weights of the two reagents as .abscissas and ordinates. Every test is marked down -in the diagram with an indication of the extraction and concentration gained. In this diagram there are drawn lines for equi-extraction and equi-concentration of the mineral that is floated out in the - concentrate. The contour of these lines gives a relatively clear impression of the conditions for flotation by means of .the chemicals used. The best conditions are of course found in diagrams where the 'areas for maximum extraction and high conntration are coincident

Jan 1, 1931