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By Enrique Hauser

FIRE-DAMP is a mixture of methane with other inert gases or combustible gases. The inert gases in question are carbonic acid, water vapor, nitrogen, etc. The combustible gases are hydrogen, ethane, etc. The study of the properties of fire-damp, therefore, becomes a study of the properties of methane and the influence on its properties of the different gases we have mentioned. Characteristic Properties of Methane 1. Respirability.-Methane being a paraffin is characterized by its weak chemical affinities. From the physiological, point of view one could substitute it for nitrogen of the air at least momentarily, without experiencing any difficulty in breathing the mixture consisting of 21 per cent. 02 + 79 per cent. CH4. I .have tried this on myself, making the gas exhaled -from the lungs burn subsequently in a Bunsen burner.1 From the chemical point of view, this weak affinity permits the gas to be burned in certain circumstances with hydrogen and oxide of carbon in an oxygenated mixture, with the result that the last two gases achieve only a fractional combustion. This practice has been utilized with success in the methods of analysis which I have perfected and which I describe later in this paper. 2. Retardation of Flashing Point.-A characteristic property of methane is its retardation of flashing point, noted by Davy in 1816 and studied by Mallard and Le Chatelier in 1883.2 Taffanel and Le Floch have recently confirmed these results.3 Let us recall the nature of this retardation:

Jan 2, 1916

By N. G. W. Cook

At present, tunnels can be driven in rock by either of two essentially different techniques, in one of which rock-breaking is accomplished by drilling and blasting and in the other by mechanical loading. The methods based on these techniques are comparable in terms of the rates at which tunnels may be advanced, although they differ widely in their range of applicability to different types of rock and lengths of tunnel. The method based on drilling and blasting has reached a high degree of development. It is applicable to even the hardest rocks and rates of advance in excess of 50 ft per day (fpd) are attainable. The main disadvantages of this method are that it involves a sequence of operations punctuated by blasting and that it is relatively uncontrolled, resulting in overbreaking the tunnel profile and damage to the surrounding rock. However, its flexibility, mobility, and low capital cost constitute real advantages in many situations, such as those involving short lengths of tunnel or low rates of advance. Tunneling machines based on mechanical breaking of the rock are a more recent development. They offer a continuous and controlled means of tunneling capable of rates of advance in excess of 100 fpd under favorable conditions. However, these machines weigh many tens of tons and consume several hundred horsepower, so that they are costly and lack mobility. At present, their applicability is limited to long tunnels in relatively soft rock where the high rates of advance and tunnel quality can offset their onerous capital cost. Many situations exist in which the superior quality of a machined tunnel and freedom from blasting would be real advantages, but where the rock is either too hard for existing machines or the length of the tunnel does not justify their capital cost: What are the possibilities of developing cheaper, more flexible, and mobile tunneling machines? Most existing tunneling machines fragment all the rock at the tunnel face to facilitate its disposal. If a machine were used to cut only the profile of a tunnel as one of a sequence of operations, it would be required to break

Jan 1, 1970

By Jerome F. Kuzmick

Many investigations have been made on the effect of the variables of pressure, sintering temperature and sintering time on the physical and microstructural charactcristics of metal-powder compacts. Severa1 such investigations have indicatcd that pressure is the least important of these three factors in an attempt to secure a dense. strong compact by a simple coltl-pressing and sintering procedure. However, it was felt that a further study of the effect of pressure on pressed and sintered metal powder compacts might prove interesting, for the following reasons: In work done in the past on the effect of pressure, temperature. arid time, the, metal-powder compacts were subjected to long sintering periods, and temperatures right up to the melting point of the metal were applied. It was thought that pressure might exert a more profound effect under short-time simtering and within narrower ranges of temperature. such as normally would be applied in large-scale production of metal-powder parts. 2. It was hoped that something further might be learned of the nature of the bond in pressed and sintered metal-powder compacts. 3. It was thought that interesting infor mation concerning the work-hardening effect of pressure on the crystal structure. of sintered metal-powder compacts would be obtained. Procedure Rectangular bars, 2 by 1/2 by 1/4 in. were molded from the following metal powders: Atomizcd till powder, 325-mesh Atomized aluminum powder, 325-mesh Reduced copper powder, 100-mesh Electrolytic iron powder, 100-mesh Atomized 70-30 brass powder, l00-mesh The, till powder was molded at various pressures up to 40 tolls per sq. in. This was the maximum, because at higher molding pressures there was considerable extrusion of tin into the die wall, jamming the die plungers. The tin specimens were not -in tered, as this phase of the work was- done merely to see how much a very sold metal could be compressed. The aluminum powder was compressed at various pressures up to 50 lons per sq in. Higher pressures could not be used because of extrusion into the die wall The compacts were sintered one hour at 000 in pure dry hydrogen. The copper powder was molded at vari-ous pressures up to 96 tons per sq. in. One set was sintered at 750°C., another at 050 C. for one hour in pure dry hydrogen. The electrolytic iron powder was molded at various pressures up to 00 tons per sq. in. and sintered, one set at Soo°C and one set at 1300°C for one hour in pure dry hydrogen. Extra 325-mesh specimens were also prepared to study the effect of reduced particle size on grain structure. The brass powder was molded at various pressures up to 96 tolls per sq. in. and silltered for one hour. one set at 65o°C. and one set at 800°C, in pure dry hydrogeu.

Jan 1, 1945

By J. W. Stewart

THE aim of this paper is to point out the various ways in which design is taught in standard four-year mining engineering curricula in American colleges and universities; to discuss the reasons apparently justifying the great diversity of procedure that exists along this line; and to indicate possible solutions to the difficulties now attending the teaching of design. A study was made of typical four-year mining engineering curricula in 15 colleges and universities of the United States (Table I). Great diversity in content of the various design courses, if taught as described, became apparent immediately. It appeared that it might be both interesting and instructive if the cause for this colorful variety could be found. Was the cause local mining conditions, departmental individuality, or actual necessity? Study of the school catalogues revealed that the various design courses could be classified into two fairly distinct types; namely, (I) those dealing with mine equipment or structures, and (2) those dealing with underground layout of mine workings. It seemed reasonable to label the first type of course "mining design" and the second type "mine design." Some such distinction must have been in the minds of mining educators, for we find both names (i.e., mine design and mining design) used to designate the design courses included in the various mining curricula. Unhappily, the name and the apparent content of such courses do not, in all instances, conform to the classification made here, although in most instances such conformation does obtain (Table I), It is possible that in the exceptional case the method of teaching a design course, and consequently the content of it, may have been changed at some time without change in the name of the course. Apparently only 3 of the I5 schools made an effort to cover both types of design in their curricula (Table I). Two other schools did not list or describe any course of study that could with certainty be taken as a design course. Of the remaining 10 schools, 9 gave a mining-design type of course and one gave a strictly mine-design type. Obviously, the preponderance of design courses afforded are of the mining-design type. Why? To answer this question, it is necessary to make a study of the prerequisites for the two types of design courses taught. In all schools the design courses were taught in the senior year; in eight, design was taught throughout both semesters; in two, it was taught during the first semester only; and in three it was taught during the second semester only. Consequently, excepting the last three cases noted, it is obvious that all prerequisites for a design course should be completed by the end of the junior year. PREREQUISITES What are the probable prerequisites for the different kinds of design courses as they appear to be taught? Let us take first the case of the mine-design type of course, having to do with layout of underground workings. Here it would seem that logical

Jan 1, 1941

By Granville S. Borden

THE program for income tax legislation presented here proposes some diminution in the current tax burden on mineral producers but it will, if enacted, eventually increase the potential and current Government revenue from the mineral industry.

Jan 6, 1951

By W. I. Duvall, D. E. Stephenson. Discussion by R. G. K. Morrison

R.G.K. Morrison (Chairman, Dept. of Mining Engineering and Applied Geophysics, McGill University, Montreal, Que. Canada) - The authors have introduced a subject, the intensive study of which has awaited scientific developments. These are now such as to justify a thorough review of our thinking on the causes and control of rockbursts. The formulae developed in the paper, the comparison between rockbursts and earthquakes in figure 1 and the energy data relating to explosives serve as an effective foundation. In the paper this writer is quoted as suggesting that energy of the order of 10 x 10 11 ft. lb. may have been released in some of the heaviest rockbursts in the Kolar Gold Field. He now hastens to add that such an estimate has no scientific validity. It arises only from a casual comparison of surface and underground effects of the medium heavy bursts, referred to in the paper and estimated by Jones at 3.0 x 1010 ft.lbs., with those of obviously greater magnitude. In any case, we have the estimate by Jones above, that by a team of seismologists 1 on the Witwatersrand of 10 x 1010 ft.lbs., that by Coates of 3.8 x 10" ft.lbs., also referred to in the paper, that by Blan-chard2 for the catastrophic rockburst at Springhill, N.S., of only 7.4 X 107 ft. lbs., and finally the range covered by Cook, referred to in the paper. It is probable also that data for the heavy rockburst at Merkers3 in the WERRA potash area of Germany are available as it was recorded on seismographs from Moscow to Spain. It is the writer's impression that some standardization is present in the estimates above for 10 x 10 10, 3.8 x 1010 and 7.4 x 107 ft.lbs., respectively. The latter, for Springhill, represents a relatively low order of magnitude. It is obvious that any energy estimate must be related to the local geometry of openings at the time of the event. It is also obvious that any explanation of the causes of rockburst must be capable of providing a wide range of energy. However, we must remember that the energy release is an effect indicating magnitude. The cause lies with the mechanism initiating the primary failure, generating the seismic activity, to which much of the damage is probably due.

Jan 1, 1967

By Harrison Souder

MAGNETITE mining and milling in the Eastern States showed continuing improvement during the year. Some of the smaller mines remained idle, but the larger operations responded promptly to the improved situation in the iron and steel industry. The output of ore for 1936 was over twice that for 1935. A number of improvements were made in mine plant and equipment, and operating forces were increased and maintained at near normal. The coming year should see additional mines started up and production increased at the larger properties.

Jan 1, 1937

By Gustaf Ising

For relative gravity measurements, the author in 1918 described an instrument1 of which the essential part consists of a highly astatized, standing pendulum turning about a horizontal elastic axis. This type of instrument has been used recently in practical field work, therefore a description of its principle and technical development is given herein. Part I, describing the principle, is a direct translation of the original Swedish paper.1 Part II gives an account of the practical elaboration of the instrument, together with some description of measure-ments performed.

Jan 1, 1937

By Charles R. Isaacs

In 1972 Kennecott Explorations, Inc. conducted a three month cruise to the central Pacific as part of a study of deep-ocean manganese nodules. One of the objectives of the voyage was to collect at least 200 tons of nodules for use in extractive metallurgy research and various engineering tests. It was determined to cut off production at a maximum of 200 tons, should we reach that amount before the end of the 38 on-station days. We were able to reach that goal; 200 tons of nodules were collected, representing an average return of 2340 lb from 171 dredge runs. Once equipment and techniques were refined, normal returns consistently exceeded 2 tons per haul. Up to this time, Kennecott had sampled extensively with the use of small free-fall devices using wire rope and winch equipment. These devices have never offered a viable method for collecting nodules in bulk, and we sought to develop a dredging capability which would give some assurance of meeting future requirements with efficiency and economy. After testing a series of increasingly complex dredge designs at sea, it was decided to utilize two of the simpler configurations, which after modification provided the basic design for the dredge used.

Jan 4, 1974

By J. D. Lubahn

The Bauschinger effect, or rounding of the corner of the stress-strain curve upon reloading, represents a temporary apparent softness that is more pronounced at large strains than small and for complete unloading than for partial unloading. Interrupted creep tests on copper exhibit a similar temporary softness (high creep rate) upon reloading. The fact that the strainwise dying-out time of these effects is the same in both tensile and creep tests shows that they are related. Thus, the term Bauschinger effect appears to embrace behavior following partial or complete unloading and reloading in addition to behavior following reversed loading. It is suggested that the term may properly apply also to certain creep behaviors following a small load decrement. INTERRUPTED tensile tests at low temperatures show1 a rounding of the corner of the stress-strain curve for reloading, which indicates a temporarily low deformation resistance. In the absence of recovery, the curve soon rises to the value that would have prevailed if the test had not been interrupted. The rounding of the reloading tensile curve has sometimes been referred to1 as the Bauschinger effect, although the term is more commonly applied to low deformation resistance in compression following tensile prestrain. The unusually broad usage of the term Bauschinger eflect in ref. 1 seems justified by the obvious interconnection of the various behaviors to which it has been applied.' In fact, the following discussion will indicate that still broader usage might be desirable. The Bauschinger effect is common at room temperature but apparently disappears at higher temperatures.2 Interrupted creep tests and tensile tests were made on certified OFHC copper (nongaseous impurities exclusive of silver were 0.004 pct), cold drawn 84 pct to ½ in. diam, and annealed at 600" (about 0.025 mm grains) or 850°C (about 0.2 mm grains). The tests were made in standard creep or tensile machines, using an O.S. Peters microformer-type extensometer or, for the small plastic strains, a special arrangement employing General Electric magnetic gage heads.' Interrupted creep tests at room temperature show3,4 an initial softness after reloading, manifested by an initial creep rate that is higher than that which would have prevailed if the test had not been interrupted. Fig. 1 shows some typical examples. This effect is apparently temporary (as is that in tensile tests): in four of the five tests shown, the log rate vs strain curve becomes parallel to an

Jan 1, 1956

By William I. Watson

Problems encountered in beneficiating mineral raw materials become increasingly difficult as there is a shift to lower grade and more complex raw materials, and because of the economic need to strive for ever higher recoveries, higher grade products, and lower processing costs. Methods of attacking the many problems should include not only the familiar chemical and physical tests and equipment, but such techniques as X-ray analysis, infra-red analysis, differential thermal analysis, and the use of electron and X-ray microscopes. Many people in the mineral-treating field are unfamiliar with these newer methods and techniques. The differential thermal analysis method, in particular, does not seem to be very well known, even though it offers interesting possibilities in the study of many ore treatment problems.

Jan 7, 1959

By Charles Wert

THE diffusion and precipitation of carbon and nitrogen in a iron have previously been investigated using the internal friction as a measuring tool.' Most of this work has been done on rather pure iron; no effect was observed which would indicate that either of these phenomena is affected by the rather small amounts of impurity found in these samples of iron. Fastz observed, however, that both the diffusion rate and the aging properties of nitrogen in iron were sensibly changed by the addition of Vz pet Mn. The diffusion rate at a given temperature is reduced and the nucleation of nitrides is apparently changed somewhat. He observed no such changes for carbon in this alloy. Later Dijkstra and Sladek" extended these observations on nitrogen to other alloys of iron. They found that metals other than manganese also influence the behavior of nitrogen in iron; chromium, molybdenum and especially vanadium affect the diffusion and precipitation of nitrogen even more than manganese does. Their results have been verified in all essential details by this author, who finds in addition that small additions of nickel have about the same effect on the diffusion of nitrogen as the same amount of manganese. The present work was undertaken to study the effect on carbon in iron of these alloying elements. The alloys used had two sources. The material used as a "standard" (designated Fe in this paper) in the measurements was some iron supplied by J. K. Stanley, of Westinghouse Electric Corp., who reported 0.01 pct 0, as the only major impurity. He also made up an alloy of 0.26 pct Ni and one of 0.9 pct Mo using this same iron as a base. They were supplied by him in 2 lb billets, which were sawed into rods and cold formed into 0.030 in. wires for measurement. The alloys of chromium, manganese, and vanadium were prepared by the metallurgy section of the Institute for the Study of Metals, University of Chicago, by adding these metals in turn to vacuum melts of National Research Corp. iron. The small castings prepared in this way were also cold formed into 0.030 in. wires. After these wires had been prepared they were decarburized for 30 min at 730°C in wet Hz. After this treatment, no trace of carbon (as measured by internal friction) could be found. All specimens were then carburized for about 15 min at 710°C and water quenched. By this treatment the internal friction at 40°C was raised to a Q-' ~ 0.015. The diffusion of carbon in these alloys was studied by observing the shape and position of the internal friction peak at 0.9 cycles per sec. These measurements were made using a torsional pendulum in a manner described earlier.' The data are plotted in Fig. 1. It is seen that there is no apparent difference in internal friction between the various alloys. This is in marked distinction to the broadening and shift-

Jan 1, 1953

By Nelson Severinghaus

Consolidated Quarries Corp. must conduct operations for an average sales price of $1.25 per ton, about the same price at which stone was sold 25 years ago when the dollar was worth twice what it is now. To maintain success in a competitive business, the company must solve the usual production problems, which will be discussed here in the order they occur in the flowsheet. Most crushed stone quarries must first remove soil and decomposed rock. Although seasons of lower sales sometimes release regular quarry excavating and haulage equipment for this purpose, overburden is often too extensive for this method to be used. In such cases, special equipment must be assigned or the job may be contracted. As many earthmoving contractors have heavy duty specialized equipment well suited to overburden removal, they should be seriously considered before the job is undertaken. Pockets of clay beneath peaks of hard stone sometimes defy mechanized removal. Pick and shovel laborers at this point might be supplanted by more ingenious use of pumps and water or some other mechanical means. Where overburden is extremely heavy or difficult to remove, underground mining must be considered.

Mar 1, 1956

The Round Table on Qualities of Pig Iron, under the auspices of the Joint Committee on Qualities of Pig Iron, which is made up of members of the American Institute of Mining and Metallurgical Engineers, the American Foundrymen's Association, the American Society for Testing Materials, the Gray Iron Institute, and the Malleable Iron Institute, was held at the Palmer House, Chicago, III., on Oct. 1, 1935. Prcoeedings R. H. SwEEtseR,* New York, N. Y.—Seven years ago last June, in Chicago, we had a round table on qualities of pig iron1, and at that time the foundrymen were out with their battle-axes for the blast-furnace men, and the open-hearth men were doing the same thing. After that meeting there was really a determined effort to find out about the qualities of pig iron, and great progress has been made all along the line. This afternoon we want to have a frank discussion of the qualities of pig iron, whether it is the molten pig iron going into the steel plant, or cold pigs going to the different foundries. We ought to hear something from Dr. J. T. MacKenzie, who is chairman of the Joint Committee, and from Mr. R. E. Kennedy, the Technical Secretary of the American Foundrymen's Association. J. T. MacKEnzie,† Birmingham, A1a.—As a result of that meeting in Chicago, there was considerable agitation in the Foundrymen's Association to develop a set of tests for pig iron. One of the difficulties was that nobody talked the same language on shrinkage, draws, live iron, dead iron, and so forth, which were the main complaints against pig iron. By request of a committee of the Foundrymen's Association, the Bureau of Standards ran a comprehensive set of tests that did develop the principles governing the optical pyrometer as applied to cast iron and pig iron. Then the Bureau went on further with the fluidity test, and developed a method for the absolute changes of volume at the freezing point. There is one serious gap in the yardstick, which has never been developed, and that is the tendency to draws from heavy sections to light. Everyone who has worried about the differences of section, and sponginess in changes of section, realizes that the

Jan 1, 1936

The Round Table on Qualities of Pig Iron, under the auspices of the Joint Committee on Qualities of Pig Iron, which is made up of members of the American Institute of Mining and Metallurgical Engineers, the American Foundrymen's Association, the American Society for Testing Materials, the Gray Iron Institute, and the Malleable Iron Institute, was held at the Palmer House, Chicago, III., on Oct. 1, 1935. Prcoeedings R. H. SwEEtseR,* New York, N. Y.—Seven years ago last June, in Chicago, we had a round table on qualities of pig iron1, and at that time the foundrymen were out with their battle-axes for the blast-furnace men, and the open-hearth men were doing the same thing. After that meeting there was really a determined effort to find out about the qualities of pig iron, and great progress has been made all along the line. This afternoon we want to have a frank discussion of the qualities of pig iron, whether it is the molten pig iron going into the steel plant, or cold pigs going to the different foundries. We ought to hear something from Dr. J. T. MacKenzie, who is chairman of the Joint Committee, and from Mr. R. E. Kennedy, the Technical Secretary of the American Foundrymen's Association. J. T. MacKEnzie,† Birmingham, A1a.—As a result of that meeting in Chicago, there was considerable agitation in the Foundrymen's Association to develop a set of tests for pig iron. One of the difficulties was that nobody talked the same language on shrinkage, draws, live iron, dead iron, and so forth, which were the main complaints against pig iron. By request of a committee of the Foundrymen's Association, the Bureau of Standards ran a comprehensive set of tests that did develop the principles governing the optical pyrometer as applied to cast iron and pig iron. Then the Bureau went on further with the fluidity test, and developed a method for the absolute changes of volume at the freezing point. There is one serious gap in the yardstick, which has never been developed, and that is the tendency to draws from heavy sections to light. Everyone who has worried about the differences of section, and sponginess in changes of section, realizes that the

Jan 1, 1936

By Charles Berkey

CONTENTS PAGE C. P. Berkey-Responsibilites of the Geologist in Engineering Projects (with discussion) 4 Kirk Bryan-Problems Involved in the Geologic Examination of Sites for Dams 10 0. E. Meinzer-Relation of Ground-water Conditions to Leakage of Reservoirs (with discussion) 19 Charles Terzaghi-Effect of Miner Geologic Details on the Safety of Dams (with discussion) 31 G. H. Matthes-More and Better Geologic Data for Use in Hydraulic Projects (with discussion) 47 L. W. Fisher and R. D. Ohrenschall-Geologic Examination of Dam Sites in the Tennessee and Cumberland River Basins 60 C. K. Wentworth-The Geology of Dam Sites (with discussion) 78 L. C. Glenn-The Geology of Dams and Reservoirs 97 H. T. Stearns-Success and Failure of Reservoirs in Basalt (abstract) 111

Jan 1, 1929

By J. O. Nomland

Bahrein 'Island.—In 1936 the Bahrein Petroleum Co. continued drilling additional wells to further increase production. In all, 39 flowing wells have now been finished and five others are drilling. A second well has been deepened for prospecting the deeper horizons but has not been successfully completed as a commercial producer. In addition, a well has recently been drilled near the eastern limit of the producing area for edge-water observation. The present system places wells 3000 ft. apart in a rhombic grid, or about one well to 179 acres. The total production for the year was 4,644,635 barrels. It is expected that refinery capacity of 20,000 bbl. per day will have been completed by July, 1937. A new permanent and enlarged camp with office buildings is being built. A new hospital has been constructed and two additional medical men have been added to the staff. Saudi Arabia.—In eastern Saudi Arabia, the California Arabian Standard Oil Co. has continued with the program of prospect drilling started in 1935. After the gas encountered in Dammam well No. 1 had been successfully shut off, it was completed as a small flowing well of 51" gravity oil. Dammam No. 2, which had been started in 1935, tested 3840 bbl. of approximately 50" gravity oil from a depth of 2175 ft. Dammam No. 5, before being deepened for prospecting lower productive horizons, encountered a gas zone producing 30 million feet. Five other wells on the Dammam dome are in various stages of drilling or completion. Most of these have been located principally to outline the productive area and the various producing horizons of the structure. An extensive program of geological work is being continued. In June, 1936, a well was started on the El 'Alat structure about 25 miles northwest of the Dammam development. Although various tar showings have been reported, the well has not yet, at 2518 ft., reached the depth at which it has been thought that productive horizons might be encountered. A prospect well is being drilled by the Kuwait Oil Co. (jointly owned by Gulf and Anglo-Iranian Oil Companies) in the Sheikdom of Kuwait. The well is near Bahra, a few miles north of Kuwait Bay and about 240 miles northwest of El 'Alat. To date no favorable results at depth of about 6000 ft. have been reported.

Jan 1, 1937

By Paul Levin

A coal preparation plant built with conventional materials only might be able to do an efficient job of preparing coal, but its maintenance costs would be high and emergency shutdowns frequent. To remedy this situation special materials are being used, either in original plant construction or for replacement of conventional materials. The special materials vary from high-strength and abrasion-resisting steels and stainless steel alloys to ceramics. They include hard surfacing welding rods, rubber refractories and some of the newer plastics, the merits of which are cited by the author. A coal preparation plant, limited strictly to the use of conventional materials-for example, mild steel, cast iron and ordinary rubber-could, no doubt, do an efficient job of preparing coal, but the high cost of maintenance and increasingly frequent emergency outages would soon force the operator to seek relief by introducing special materials such as alloyed steels, oil-resistant rubbers and hard-surfacing welding rods.

Jan 6, 1964

By M. E. Wadsworth, I. B. Cutler

Coprecipitation of anionic and cationic polyelectrolytes has been applied to floccula-tion of several mineral systems. Results obtained in a study of the flocculation of kaolinite and hematite suspensions of polycationic and polyanionic electrolytes are presented. Greatly increased settling rates were observed following precipitation of positive and negative polyelectrolytes on the surface of finely divided minerals in aqueous suspension. The ratios of polycationic to polyanionic electrolytes required to produce maximum sedimentation have been shown to correspond closely with the equivalence points obtained by light scattering studies of systems containing the positive and negative polyelectrolytes by themselves. DISPERSION of colloids has been of interest to surface chemists for many years. Flocculation studies have been employed to evaluate the limits of colloid stability. In water suspensions, colloids become unstable and flocculate when the ( potential, the potential of the kinetic solvation sheath, falls to a value at which van der Waals forces may act to draw the particles together. This may happen through an adjustment of the pH of the suspension or by addition of a salt. Optimum conditions for rapid formation of large flocs are found in the region of minimum ( potential. In addition to these well known considerations, colloids in water suspensions are known to be flocculated by certain large organic macromolecules. These polyelectrolytes in some cases minimize the i potential and in other instances increase the attractive forces by supplying sites for hydrogen bonding.' Use of organic polyelectrolytes in flocculation of mineral colloids has increased rapidly in recent years. These materials are now recognized as indispensable aids to fluid-solid separations in many extractive metallurgical operations. They have been found to increase both the settling rate in thickeners and the filtration rate of filters. In the elucidation of the characteristics of these organic reagents as floc-culants in this laboratory, it was discovered that interaction of certain polyelectrolytes had a surprisingly good effect on flocculation of mineral colloids. Experimental Procedure: The anionic flocculants used in this study were Lytron 886 and 887, produced by Monsanto Chemical Co. Both reagents are copolymers of vinyl acetate and maleic anhydride. Lime is added to Lytron 886, whereas Lytron 887 is all organic. These reagents possess two carboxyl groups for each acetate group and are therefore anionic in character. The cationic reagents used were the Peter Cooper Co. 1-X and 2-X glues. The structures are not definitely known, but the re- agents are amines and are cationic in character. The glues were prepared in the chrome-alum form. Both types of reagents may be classified as polyelectrolytes in that they are high molecular weight polymers and ionize in water. All data presented are in terms of sedimentation rate, measured in 250-ml glass-stoppered graduated cylinders. With suitable precautions such measurements are fairly reproducible and provide a sensitive means for selecting important parameters such as pH, reagent concentration, and floc size and density.2 Agitation was standardized with five complete end over end cycles of the suspensions in the stoppered graduated cylinders.

Jan 1, 1957

By V. I. Purcell, S. C. Sun. R. E. Snow

A study including effects of 7) pH value, 2) fatty acid collector, 3) fuel oil, 4) interfering ion, 5) particle size, and 6) operational variables. Test results indicate feasibility of fatty acid flotation under certain restrictive conditions. FATTY acids have been used as standard collectors for floating the matrix1-8 but not the leached zone phosphate ores. After a series of investigations, Davenport9 and Tarbutton10 concluded that the Florida leached zone ores tested were unamenable to fatty acid flotation and must be upgraded by floating the siliceous gangue with Armac-T as collector. The cationic flotation was estimated11 to cost almost ten times as much as a fatty acid process that would ideally give the same flotation grades and recoveries of phosphates. Mineralization: Extensive deposits of leached zone aluminiferous phosphate occur in Florida."= The ore sample used for this work was obtained from the Virginia-Carolina Chemical Corp., Clear Springs area, Florida. The ore is a potential source of uranium and aluminum as well as phosphorus. Since the uranium and the recoverable aluminum are contained in some of the phosphate minerals, an upgrading of phosphate results in a corresponding enrichment of both uranium and aluminum. The phosphate minerals in the ore are primarily pseudo-wavellite, millisite, and carbonate fluorapatite, with a minor amount of wavellite. Quartz and clay are the common gangue minerals, quartz being predominant. Others present in small amounts are ilmenite, hydrated iron oxides, staurolite, monazite, and zircon. Experimental Procedures: After being dried to less than 1 pct surface moisture the material was dry-ground in a Hardinge conical ball mill to —6 mesh. The ground product was classified into 6/20, 20/200, and —200 mesh size fractions. On the basis of Table I, the coarse and fine size fractions were considered as phosphate concentrates, because of their high phosphorus contents. In contrast, the 20/200 mesh fraction, which was low in phosphorus, was used as the flotation feed. All the flotation tests, unless otherwise stated, were performed in a laboratory Fagergren machine under the following conditions: 1) 400 g of solid feed for each test, 2) 2000 rpm impeller speed, 3) 8.9 pH and 4-min conditioning, and 4) 3-min flotation. The procedure used for the quantitative bubble pick-up tests has been described previously.18

Jan 1, 1958