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By M. Oka, C. M. Wayman

It has been known for some time1 that (110)b twinning is possible in bct martensite.* Any plane of the form (110) not parallel to the fourfold axis of tetra-

Jan 1, 1969

By K. A. Slagle, D. K. Smith

weight obtained. Additives used in conjunction with salt in these slurries have included silica flour, calcium ligno-sulfonate and cellulose retarders, granular lost-circulation materials, bentonite and selected low-water-loss additives that are not significantly deteriorated by the presence of the chloride ion. In some other areas of South Texas, the salt-saturated slurries have been used quite extensively for improvement of the flow properties of slurries and attainment of better circulation characteristics at lower displacement rates. Concurrently with this property, the protection of shales and shaly sands is also realized, as well as useful retardation of the slurry. Resultant superior cementing jobs have been indicated by both communication tests and acoustic logs for bonding to pipe and formation.' In one section of Louisiana, a major oil company has been using salt-saturated API Class A cement with calcium lignosulfonate retarder for cementing through the Miocene at 9,000 to 10,000 ft. This is another of the situations where interbedding of sands and shales exists, creating difficulty in maintaining formation competency when a fresh-water slurry contacts the clay minerals of the formation. Further work has also been done in the shaly Miocene formation at 13,000 to 15,000 ft where fairly close water or gas contacts are encountered. Indications thus far are that better segregation of these various fluids is obtained by use of the saturated salt slurries because of their improved formation bonding characteristics. In addition to the properties of salt in this situation, attainment of turbulent flow at minimum displacement rates has also been accomplished by use of an additive to help provide exceptional dispersion and viscosity reduction of the slurry. Another oil company was encountering considerable expense in completing wells in Southwestern Louisiana due to extensive block squeeze requirements for effective separation of zones. A very effective mud program was being used to minimize washout in the shale sections and, apparently, a nearly gauge-size hole was being obtained. However, primary cementing results with fresh-water slurries were generally poor. On a few occasions when slurry was actually circulated to the surface, large pieces of shale formation were brought out of the hole with the slurry, indicating a severely water-sensitive, sloughing formation. Inhibition of shale heaving was being accomvlished in the drilling program, and immediately indone ipon circulation of the fresh-water slurry even though it contained a low-fluid-loss additive to reduce filtrate damage in the sands. The subsequent change to salt-saturated slurry yielded 11 successful primary cement jobs out of 12, compared to the previous success ratio of practically zero. Since these were deep, high-temperature wells in the range of 13,000 ft with high-pressure zones necessitating 17.5-lb/gal fluid densities, the slurry used was API Class E cement, silica flour, weight material, retarder, salt saturation (which also reduced the amount of weight material) and maintenance of low fluid loss by use of a salt-compatible additive. Other salt slurries have been used to a limited extent in this same general area for similar problems at depths ranging from 5,000 to 17,000 ft. In the shallower wells, the cement has usually been API Class A where the salt functions as a retarder, and in the deeper wells API Class E cement is used with the additional salt advantage being its increased slurry weight and inability to dissolve salt stringers. A considerable number of squeeze jobs have also been done on older wells using the salt-saturated slurries with very good results. MID-CONTINENT In North Texas, salt-water slurries have been used for cementing the Woodbine sand, Strawn sand, KMA sand and Pettit lime. Shales surrounding these formations have created the same difficulty in obtaining separation of producing zones that has been the problem in other areas. Depths in this area range from 3,400 ft for the Strawn to 7,400 ft for the Woodbine, and concentration of salt has varied accordingly. In the deeper wells, where retardation is desired, saturated salt-water cement is used; for the shallower wells, in order to provide shorter waiting-on-cement times, the amount of salt has been 18 per cent by weight of the mixing water. Results have been excellent with no reported failures on any of the salt cement jobs; where acoustic bond logs have indicated indifferent bonds previously, they are indicating very good bonding for the salt slurries. In Oklahoma various shales of Pennsylvanian age exhibit a high degree of sloughing in the presence of fresh water, causing severe washouts above and below sand formations which it is desired to isolate. This situation exists to some degree in practically all parts of Oklahoma and includes formations of other ages such as the Wood-ford shale. For the past few years, salt-saturated cements and displacement rates as high as practical have been used as a remedy for this problem, with very good results. The Layton and Bartlesville formations are two examples of shaly sands where saturated slurries have been helpful. In one area where five wells were drilled through this type of problem shale without obtaining a satisfactory primary cement job, a change was made to salt-saturated cement preceded by a suitable chemical wash for the drilling mud involved. Acoustic bond logging indicated excellent bonding, and final completion bore out this result by being trouble-free. This type of slurry has also been used extensively on squeeze jobs where shales have been heaving around the producing formations. Predominantly, the basic slurry has been either API Class A cement or a pozzolan cement—although, as deeper wells are being drilled, the use of salt in Class E cement is also increasing. Salt cement in West Texas has been used primarily to help prevent channeling through the shales around the Delaware sand, Queens dolomite and Hope lime. Many of the shaly and dirty sands of this area are sensitive to the filtrate from a fresh-water cement. Salt at 16 to 18 per cent by weight of mixing water has been added to centent, and has been effective in controlling formation damage and communication between zones in these formations. Use of these lower salt concentrations is dictated in this area by the relatively low formation temperatures where retardation of the slurry would create unduly long waiting-on-cement times. Also, quite a bit of cementing has been done in this area using salt concentrations in the accelerating range— that is, 2 to 5 per cent by weight of water. Specifically, these concentrations have been used in coiljunction with high percentages of gel to overcome the retarding effect of the calcium lignosulfonate dispersant, although there are probably several shales where these concentrations could provide some degree of formation stability. On several occasions, the salt has also been used to lower the critical velocity or rate for turbulence with the slurry, particularly in the pozzolan cements. On wells in the Hope lime, it has usually been necessary to squeeze the shale above and below the lime to get a water-free completion. Use of salt-saturated slurries has largely eliminated this

By F. M. Walters

IN order to isolate the effect of an element on some property of an alloy, the effect of the other alloying elements must be elimi- [ ] nated, either by reducing their quantity to the extent that they may be neglected or by determining the specific effect of each. The success of Grossmann1 in calculating [ ] hardenability from chemical composition by means of factors suggested such a

Jan 1, 1942

By O. U. Bradley

The utilization of casing-head gas in the manufacture of casing-head gasoline by both the absorption and the compression method is a most important factor in the conservation of our natural resources. Any industry connected with the oil business, in general, possesses particular attraction for a large number of people not conversant with its basic principles, for the reason that the large fortunes made in the production and utilization of petroleum and its products have been given undue prominence. The general impression of the public that enormous profits are to be realized in the casing-head gas industry with minimum expenditures of both capital and effort has, in a large measure, accounted for the phenomenal expansion of the industry in recent years and, likewise, has resulted in many mistakes and loss of investment funds. It is true that many installations have been very profitable, but such instances are always the result of careful planning, experienced judgment and conservative estimates. The inception and subsequent activity in the manufacture of casing-head gasoline, enabling the business to assume an important position in the petroleum industry, are of comparatively recent origin, as its greatest growth, particularly in Oklahoma, occurred during the years 1917 and 1918. Much information must yet be secured and systematized concerning the methods of manufacture of gasoline from high-yield casing-head gas, and a large field is still open for the application of accumulated experience and good engineering practice in devising better methods of extracting gasoline from casing-head gas of the poorer grades. The absorption process is coming into general use as a most efficient system of treating casing-head gas, and even so-called dry gas. In fact, there is a decided tendency toward the universal adoption of the absorption process as against compression methods. However, a general discussion of the relative merits of these two systems is not, within the scope of this article. A few of the facts that must be given 'consideration in arriving at a fair and impartial estimate of the actual investment value of the casing-head gas business are the quantity of gas available, the quality and

Jan 1, 1921

Jan 1, 1937

By J. S. Osoba, J. G. Richardson, F. M. Perkins

Laboratory experiments have shown profound diffcrences in the behavior of so-called "fresh cores" from the East Texes field and of the same cores after ex~ractio~l with organic solvents. The residual oil satura/ion remaining after waterflooding fresh cores was appreciably lower than the corresponding saturations after flooding extracted cores. This behavior was also reflected in the water-oil relative permeability-saturatiorl relations, which were more favorable for high oil recovery from the fresh cores. These differences were evident not only in the amount of residual oil left after wafer flooding, but also in the saturation water remaining in the core after displacernent by oil. Residual water saturation after displacernetzt of water by oil was higher in the fresh cores than in the extracved core,. Capillary pressure-saturation relations were also different for the fresh crnd extracted cores. Imbibition experiments indicated that both fresh and extracted Bast Texas cores imbibed water spontarteOLISIY, but- the rate of imbibition of water was higher for samp1es after. extraction than it was for fresh core. material. INTRODUCTION Several years ago a series of waterflooding tests was made in the laboratory on a number of Woodbine core samples from the East Texas field. These samples had been stored in containers open to the air and were extracted with organic solvents before they were subjected to the laboratory tests. After water flooding, the residual saturation of kerosene, which was the oil used in the tests, was found to average about 30 per cent. This saturation was higher than expected. In investigating the circumstances which might have been responsible for such a high residual oil saturation, attention was given to possible changes in wetting properties of the rock brought about by the procedure employed in extracting the cores. Preliminary results indicated that the explanation for the high residual oil saturation lay in the wetting behavior of the cores, though what effect extraction had on this behavior was not clear. In consequence, the work described in this report was undertaken in an attempt to investigate the mechanism responsible, and to ascertain the actual residual oil saturation to be expected in the reservoir after water flooding. It was soon found that there were profound differcnces in the behavior of so-called "fresh cores" from the East Texas field and of the same cores after extraction with organic solvents. These differences were evident not only in the amount of residual oil left after water flooding, but also in the saturation of watet remaining in the core after displacement by oil. The complete explanation of this behavior is not yet apparent. The description of work and results described in following sections, therefore, must be considered as an interim report presenting facts which must await additional information before they can be fully interpreted.

Jan 1, 1956

By Ralph S. Siegrist

For the past 30 years the construction industry has used steel supports in rock and soft ground to expedite driving tunnels under many difficult conditions. The industry has had a definite advantage in that it bids its work in accordance with the type of job to be encountered. The mining industry has had to keep its progress in line with the economics imposed by the price of the commodity it mines. Even so the mining industry, particularly metal mining, has been using steel support. Timber was universally used because of availability and cheapness, but as timber became scarce and labor more expensive-it takes more time to erect timber support-steel gradually replaced timber.

Aug 1, 1956

By Persifor Frazer

COMPARATIVE columns expressing the series of rocks of the lower half of the Mesozoic age in this country and in Europe are not yet definitely established. The following represents a co-ordination of the beds in England and Germany,* with a list of materials to be worked in from this country. † * Cotta, " Geologic der Gegenwart." † Section from York to Dillsburg. Report C, 1875; Second Geological Survey of Pennsylvania.

Jan 1, 1877

By Alten F. Grandt

What is prime farmland? Can such land, once it has been surface mined for coal, be restored so that it will produce corn, soybeans, wheat, and alfalfa? What methods or practices are necessary to bring about restoration within a reasonable time so that crop yields will be equivalent to or higher than those of unmined prime farmland under high levels of management? These questions concerned land use researchers in Illinois as early as 1948 when the Illinois Agricultural Experiment Station experimented with growing cultivated crops on surface mined land in St. Clair County (Grandt, 1949). This research was done almost thirty years before requirements of Public Law 95-87 were passed by the US Congress and signed August 3, 1977.

Jan 1, 1982

By R. A. Wyman

The overall approach to nonmetallic mineral flotation practiced in the laboratories of the Mines Branch, Ottawa, Canada, is outlined. The use of floatability tests to indicate possible areas of selectivity is indicated. Selected examples of the evolution of flotation systems are presented. Reagents are briefly discussed.

Jan 1, 1972

The Library of the above-named Societies is open from 9 A.M. to 10 P.M., except on holidays. It contains about 70,000 volumes and 90,000 pamphlets, including sets of technical periodicals and the publications of scientific and technical societies. Members of the Institute, with few exceptions, are forced to spend a portion of their time in localities isolated from sources of information. To these the Library, through its Library Service Bureau, can render valuable service through correspondence; letters requesting information will receive especial attention. The Library is prepared to furnish references and photographic copies of articles on mining and metallurgical subjects; to determine the existence of mining maps, and to furnish general information on the geology and mineral resources of all countries. All communications should be made as definite as possible so that the information received may be what is, desired and not include collateral natter which may not be of interest. The time spent in-searching for such collateral matter will be saved, and the information will be sent more, promptly and-in more usable shape.

Jan 2, 1917

By Gordon W. Hodgson, Edward Tipman

INT'RODUCTION An appreciable number of the oil fields in Western Canada are accumulations of heavy black oils in more or less unconsolidated sandstones. When the crude oils are produced by conventional means, they are frequently contaminated with both sand and oilfield water. The water is usually present as emulsified water, and the sand and other solid materials are suspended in the emulsions. The presence of the solid material in the crude oils is troublesome and, in general, little is known about the behavior of suspended solid particles in emulsions. The Stokes equation describes the behavior of suspended particles in homogeneous fluids in terms of particle size, density differential, and fluid viscosity. In the case of an emulsion, particle size and density differential introduce no difficulties, but considerable doubt centers around the viscosity term. It has been reported1 that the viscosity of an emulsion is related to the viscosity of the continuous phase by an expression of the type: n = a, (1 + a C) where n is the viscosity of the emulsion, n,, is the viscosity of the continuous phase, a is a constant, C' is the volume concentration of the disperse phase. The value of 17, the coefficient of the concentration term, has been determined for various systems, and has been found to vary from a value of 1 to 4.75. The value of 2.5 has been found to be applicable to a large number of systems, and this is the value that is widely used in the equation which then becomes the Einstein equation for the viscosity of emuls~ons. It is of considerable significance that neither the particle size nor the viscosity of the disperse phase enters the expression; the expression for the viscosity of the enlulsion is based solely upon the viscosity of the continuous phase and the concentration of the disperse phase. For crude oil emulsions the Simha equation and the data presented by Fukushima and lchimurai show a non-linear dependence of the viscosity ratio on the water concentration. While it is undoubtedly reasonable to use these data for predicting the viscosity of a specific emulsion, and while it is equally reasonable to expect the calculated viscosity to predict the settling rate of a solid spherical particle in the emulsion by means of Stokes equation, there seems to be no direct evidence that this calculation is indeed sound for describing the settling rates of solid particles in emulsions of water in crude oils. PROCEDURE A direct approach to the problem was thus indicated. Laboratory equipment was designed and built for the direct determination of the rate-of-fall characteristics of solid particles in emulsions of water in oil. Although the apparatus incorporated the basic design of conventional falling-ball viscometers, the study was concerned directly with the rate-of-fall characteristics of particles in emulsions, rather than with the viscosity of the emulsions as such. The crude oil used in this study was a very heavy black crude oil—the McMurray oil obtained from oil-soaked sands outcropping on the Athabasca River in northeastern Alberta. It was produced from the sands by strip mining followed by hot-water separation of the oil in the separation plant of the Alberta Government at Bitumount'. The primary plant product was a wet crude oil containing about 5 per cent solids and 35 per cent water. The final plant product was only slightly different from the native oil, having lost only about 4 per cent of its bulk as light ends during dehydration distillations. In the present investigation two kerosene dilutions of the McMurray oil were used in addition to the dry plant product. The McMurray oil contained 1.92 per cent solids. Analysis of the solids by X-ray diffraction showed the presence of kaolinite, pyrite, and illite as major constituents. with lesser amounts of quartz. Particle size of the pyrite and quartz was less than 10

Jan 1, 1957

Regulation of the Coal Industry. BY HOWARD N EAVENSON (Tech Pub 711, also Trans, vol 119 3400 words) A review of conditions in the bituminous coal industry during the last 15 years and of the attempts to remedy them through Appa¬lachian Coals, Inc, and through the NRA The lack of any provision in the so-called "Guffey" law for conservation of our coal supplies is pointed out and the efforts at regulation of the English coal industry are described Assuming that some regulation of the industry is necessary to maintain reasonable working and living conditions and that Federal control by compulsion will not be possible, the requirements for regulation

Jan 1, 1937

By T. C. King

AT the new Graham-Central Mill of Eagle-Picher, near Galena, Ill., material is simultaneously dewatered and introduced into the ball-mill scoop boxes by the use of variable-speed, 24-in. spiral classifiers. This arrangement has proved satisfactory in that the moisture content of the wet feed is reduced, thus allowing maintenance of density within the mills, and a constant feed at any desired rate to the mills is provided. In this mill the primary feed is wet crushed to minus ½ in. and preconcentrated by jigs to produce a bulk lead-zinc-iron concentrate and a waste tailing. The jig concentrate is then dewatered by a conventional dewatering classifier and stored in, bins ahead of the ball mills. Even though this material is well dewatered, the discharge at the bin bottom is sloppy because of the gradual drainage of the water from the surface of the particles. Conventional belt feeders with vertical cutoff gates are unsatisfactory because of the flushing characteristic of the wet sand.

Jan 1, 1950

By E. K. Landis

The question of magnetic concentration is assuming considerable importance, and the efficiency of the different concentrating-machines is widely discussed. As the amount of iron left in the tails must vary with commercial requirements, and with the nature of the minerals in the tails, the writer feels justified in calling attention to some points often overlooked. In almost every such commercial operation a point is reached beyond which it does not pay to go, the material saved by further operations being obtained at a cost too great. The amount of iron left in the tails from concentration must depend, therefore, upon the cost of crushing, the size to which the ore is crushed, the nature of the minerals in the gangue, and the nature of the ore itself. Some ores are so intimately mixed with their gangue that a large loss of iron in the tails is unavoidable. In many cases the gangue contains hornblende, pyroxene, serpentine, etc., which carry considerable iron as silicate, or otherwise combined, and this iron a magnetic machine cannot extract, since the minerals themselves are not magnetic. It is evidently unfair to charge the machine with this loss of iron; and hence a satisfactory test of any such apparatus would require that the iron present in the ore as magnetite should be determined, and the proportion in the tailings of such iron only should be the measure of the loss, as compared with theoretical efficiency.

Jan 1, 1892

By W. A. Vine

WHEN a hole is made in a stressed solid, such as rock pierced by mine openings, equilibrium of the solid is destroyed. To re-establish that equilibrium the stress condition in the rock surrounding the opening becomes rearranged. This rearrangement may or may not develop local stresses in the vicinity of the opening which exceed the elastic strength of the rock. Since stability of the opening depends, therefore, on the strength of the naturally occurring rock surrounding the opening, this rock is an engineering material of construction, and all rock affected by the associated opening or system of open- ings may be considered a structure. The term invert is chosen to describe the formation of the structure —built from the inside, as it were, and a consequence of mining rather than an entity built for a purpose. By definition, an invert structure is formed when openings are made underground and is composed of that material on the solid side of a rock-air interface wherein the stress condition is affected by the associated opening or system of openings. The shape of an invert structure is never clearly defined; the skin of the structure may be mapped, and even described, but the boundary of the structure within the solid rock mass must be arbitrarily set. The name geomechanics is proposed to describe a branch of scientific knowledge which will encompass principles and working hypotheses for behavior and design of invert structures. It is foreseen that study

Jan 1, 1956

By George S. Miller

Now that low-carbon steel is manufactured successfully in large quantities by the Bessemer process, and threatens to displace wroughtiron for nearly all purposes, it becomes interesting to find how its Specific gravity compares with that of wrought-iron. The general name "steel" is retained in this paper to designate that metal made by the Bessemer process, which might be more properly called " ingot iron." But the former name seems to be quite firmly established in the iron trade. This steel offers many inducements to the manufacturer of architectural iron, by reason of its hornogencity, and the large masses in which it may be readily moulded. The steel from which these determinations have been made, was produced in four-ton heats and cast into ingots of about 3100 Ibs. weight, having an average section 14'' by 14". These ingots were rolled in a blooming-mill to a section about 24" by 14", cut into slabs and rolled in a plate-mill to a plate .065" to .165" thick, and about 1411 in width. The specific gravity was obtained from pieces of this plate. The metal showed by analysis .10 to .12 per cent. carbon,.33 to .45 manganese,.060 to .072 sulphur,.075 to .082 phosphorus, and .010 silicon. The samples were not annealed, but were brought to a bright surface with a file. All figures given are averages of not less than three determinations on separate pieces from the same plate. The variation in the figures from which the averages were made in no case exceeded .015.

Jan 1, 1886

By H. R. Green, D. M. Lamb, A. D. Taylor

The design of slurry launders has usually been based on strictly empirical concepts. An examination of the most common procedures reveals that they do not account for many of the variables that are recognized as significant for slurry transport. These may include flow rate, volume concentration of solids, solids specific gravity, solids size distribution, particle shape, launder geometry, and roughness of the wetted surface. It was decided to develop a design procedure, which would accomplish two things: First: Take into consideration most of the known significant variables and systematize the procedure to assure consistent results. Second: Provide a rational basis for examining and utilizing operating data to refine and improve the system. To accomplish this, it was necessary to develop a basic design concept. This concept has been developed through a complex development history, and yet still appears workable and technically sound. That concept may be outlined as follows: First: The solids transport velocity is the fundamental basis for slurry launder design. Second: The stream configuration, hence the launder size, is integrated with the solids transport velocity so that the actual stream velocity exceeds the solids transport velocity. Third: The launder slope is that which will achieve the

Jan 1, 1979

By Norman L. Newbern, Robert E. Green

An investigation of the effect of size on the deformation properties of metal single crystals made it desirable to grow from the melt cylindrical aluminum single crystals possessing exactly the same crystallographic orientation but varying in diameter. Methods for the growth of rather large (up to 3 in. diam) aluminum single crystals in molds of the desired shape are well known. However, when one applies the same techniques to the growth of smaller (less than 1/8-in. diam) specimens many additional problems arise. Two of the major problems are the construction of the molds to be used and the removal of the thin specimens from these molds without deformation after growth has been completed. Also the problem of the constraint forces exerted by the mold on the specimen is much more pronounced for the smaller specimens. The technique described herein is a zone-melting method in which no mold is used since the surface tension of the molten metal and its oxide is sufficient to retain the melt. The specimen is suspended vertically in a manner similar to that of Keck and Golay.2 However, while Keck and Golay supported the specimen from both ends, the method used here supports the specimen only at the upper end. The surface tension of the molten aluminum and aluminum oxide contains the melt and suspends a length of newly grown crystal that has already passed through the molten zone until the weight of the newly grown crystal is equal to the component of surface tension holding the specimen together in the molten region. When the weight of the newly grown crystal is equal to the component of surface tension holding the specimen together the specimen pulls in two in the molten zone. The length of crystal which can be grown before this separation occurs varies with the diameter of the specimen and the size of the molten zone. In order to prevent the specimen from pulling in two a tube of glycerine is placed beneath the furnace in such a manner that the newly grown crystal passes into the glycerine which provides sufficient buoyancy to allow aluminum single crystals in wire form to be grown to lengths determined only by the length of the tube containing the glycerine. A schematic diagram of the experimental arrangement is shown in Fig. 1. The furnace used is constructed as follows. High-resistance nichrome wire is coiled on a 3/8-in. diam fused quartz tube. The distance between the windings is much less over a length of about 3/8 in. at the center so as to develop a hot spot. This core is located in the center of a 4-in. diam steel cylinder 5 in. in height and insulated from it by Kayolite. The temperature of the furnace is controlled by means of a thermocouple located near the central hot spot and a Minneapolis-Honeywell temperature controller. Temperature ins,ide the furnace is measured with a thermocouple and a standard potentiometer in the usual manner. By the above method it is possible to grow high-purity (99.99 pct Al) aluminum single-crystal wires over a range of sizes. Crystals varying from 1/8 to 1/64-in. diam were grown by the authors. Since the tube containing the glycerine cannot contain a crystal longer than approximately 3 ft, the growth of crystals longer than this presents another problem. It was found that one could cut the newly grown crystal without deformation in the region between furnace and glycerine tube try means of a cutting torch and then by moving the glycerine tube slightly aside continue

Jan 1, 1962

By F. M. Lewis, J. F. Meyers

In the mining and handling of sulphide ores, some degree of oxidation takes place on the sulphide surfaces, which are exposed to the atmosphere. It is, moreover, well known that the oxidation compounds formed are a factor when such ores are subsequently treated by flotation. Modern operating technique and reagents are capable of contending with this condition to a major degree, provided that the proportions of the reagents used are varied correctly. This is particularly true at the Tennessee Copper Co., where the ore treated contains pyrrhotite in addition to other sulphides. A number of soluble salts, some of which are unstable, can be formed during the oxidation of the sulphide ores. Those unstable salts, whose oxygen requirements are unsatisfied, are constantly changing to more stable forms because oxygen reacts with them during the crushing, grinding and other operations of ore preparation. We add no chemicals of any kid to the ore pulp in its preparation for flotation feed. Consequently the only compounds that are present in the flotation feed are those produced by the natural oxidation of the ore in the presence of air and water. The Tennessee Copper Co. ore is composed of from 60 to 70 per cent sulphides and from 40 to 30 per cent non-sulphide material. It is not the purpose of this paper to discuss the nature of these various oxygen-sulphur compounds nor their effect on flotation, but to describe a method for correcting the effect. Suffice it to say that we have found that the reducing sulphur and oxygen salts have a depressing action on our bulk flotation process.' From long experience we find that the best means of correcting for this variation in our work is to increase or decrease the quantity of xanthate, the promoting agent, as the quantity of the reducing salts increases or decreases. It was, therefore, very desirable to provide the operators with some quick and

Jan 1, 1947