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By John A. Church

When, in 1879,I examined the mines of the Tombstone Mill and Mining Company, at Tombstone, Arizona, I found a bed of tailings containing 12,000 tons, which had a value of 9 to 12 ounces of silver per ton and some gold. The ore had been amalgamated in pans, in which each charge had been ground for four hours, having been pre viously stamped through rough-punched screens, which gave a pro duct varying from 1-100th to 1-20th of an inch, according to the state of wear of the screen. It was certain that a large proportion of the tailings must be in fine slimes, and the question of recovering their value was difficult. Even now the concentration of slimes is . an unwelcome task, and at that day very little was known about it. Nevertheless, after considering the results of a test by repanning the tailings, I advised the company to concentrate and smelt, although they had to face the difficulty of making a smelting-product from slimes containing only 3 per cent. of lead. Limestone was abundant enough, but no iron suitable for flux was to be had for hundreds of miles. One of the company's claims con tained an argeutiferous manganese-ore, which gave but poor results by amalgamation. This was one reason for recommending smelt ing ; for if manganese would play the part of a precipitant, as iron does, the company could smelt by combining two of its silver ores, without other flux than the small amount of lime that might be needed. At that time no smelter had ventured to trust manga nese as a precipitant, though large quantities of this ore containing silver were bought and used by custom-smelters, who looked upon the manganese solely as a basic flux for silica. I believe that no other furnace has been obliged to trust this metal, and that the man ganese practice of Tombstone remains unique among the records of smelting lead-ores in the shaft-furnace. The bright side of the problem was given by the fact that the mines were shallow and that the enterprise would at least begin with oxidized ores. The tailings contained about 85 per cent. of silica,

Jan 1, 1895

By AIME AIME

DURING my senior year at college a professor said to his class that a student who failed to obtain a passing grade in that certain subject could not graduate with his class and that his diploma would be withheld until the failure had been removed. In that way for four years a diploma had been made to appear to us as the objective in attending college. We grew up to think that a diploma was the means of providing employment; consequently, a diploma could not be jeopardized and, heeding the professor's remarks, we resolved to put forth special efforts and make good. During one of our class periods this same professor digressed briefly from his prepared lecture in metallurgy and advised the boys to join a national technical society. He spoke with earnestness and sincerity. After class we students discussed those remarks. We concluded that the professor had not convinced us. We were already members of technical societies at school and saw no need of joining another. In fact, even up to that moment a society had never indicated to any of us that joining it had any relation to landing a job, and we were fully aware that joining another society meant paying out more money, for fees and dues, which money we then needed to buy food, clothes, and perhaps a new slide rule. Furthermore, we knew that joining a society was not part of the curriculum and, therefore, the diploma could not be withheld if we did not follow the advice. Our conclusion was that we would not join but would concentrate on our work that assured getting our diplomas.

Jan 1, 1936

By William L. Batt

FROM the time the Japs overran the Far East, the United Nations faced a serious military problem in the critical shortage of many raw materials desperately needed to prose¬cute the war on two fronts. For many months this critical shortage threatened substantially to limit the gigantic effort to get shooting equipment into the hands of the fighting men on the far-flung battle lines. Now this crisis has been met. Solvency in raw materials has been achieved. Simply stated, this job of producing solvency has been done by "cutting cloth to fit the garment." This does not mean that we have all the raw materials we need. Unfortunately, a few raw materials are still short, thereby limiting the total production of certain war goods, or making these goods less effective. Where the supply of raw materials is known to be limited, however, substitutions have been made or production schedules have been geared to the amounts available, and an over-all balance has been achieved between various parts of the war-production program.

Jan 1, 1943

By J. E. Lawver, J. D. Raulerson, Charles C. Cook

The agriculture industry has made great strides during the past decade to increase agriculture yields through increased use of fertilizers. Increased use of fertilizers may prevent, or at least delay, mass starvation due to the alarming increase in world population. Phosphate was added to soil as a plant nutrient in the form of calcined bones at least 2000 years ago (Anon., 1964), and man has used phosphate minerals as a source of fertilization in one form or another for at least 100 years. During 1977 the world produced about 116 Mt of phosphate rock, with about 86% used for fertilizers and another 4% for animal feed supplements. More than three-fourths of the total production comes from the United States, Morocco, and the Soviet Union. From a mineral beneficiation point of view, the major sources of phosphate rock and the methods of beneficiation can be classified as follows: marine deposits not containing appreciable carbonate minerals, marine deposits requiring a francolite carbonate mineral separation, igneous deposits not containing appreciable carbonate minerals, and igneous deposits requiring apatite carbonate mineral separation. [ ] Guano, mostly from Chile and Peru, accounts for 0.1% of the total world production, and the calcium phosphates from Ocean, Nauru, and Christmas Islands and the aluminum and iron phosphates from Brazil and Aruba account for less than 4% of the world production and are thus not considered in this classification (Lawver, et al.). At present, marine phosphorite deposits account for about 75% of the world's production; the igneous deposits account for 20%. The igneous deposits low in carbonate minerals are easily concentrated by crushing, grinding, and apatite flotation. The most important igneous deposits are those of the Kola Peninsula, USSR (Woodrooffe, 1972). The igneous deposits high in carbonate materials are of corn appreciably more difficult to beneficiate, but they have been concentrated by froth flotation for a number of years. An interesting but rather complicated flowsheet of this type is at Phalabonva, in the Republic of South Africa (Lovell, 1976). The Phalaborwa deposit is an igneous complex of pyroxenite with a central core of carbonatite surrounded by a serpentine- magnetite-apatite rock called phoscorite. The phoscorite containing about 10% P2O5, 35% magnetite, and 35% calcium magnesium carbonate is currently being processed. The process involves comminuting the material for fiberation and subjecting it to a copper float using a potassium amyl xanthate as collector and triethoxybutane as a frother followed by a magnetic separation of the tailings to produce a feed for phosphate flotation. This process produces a phosphate concentrate containing greater than 36% P2O5 at a P2O5 recovery ranging from 75 to 80%. Considerable success has been claimed for recovering apatite from carbonate-bearing ores at the Jacupiranga Mine of Serrana S/A (Silva and Andery, 1972). The carbonatite currently being mined contains an average of only 5% P205 and is concentrated using a unique flotation process (Andery, 1968) to yield 96% P205 concentrates. The ore contains about 12% apatite, 5% magnetite, 80% calcite plus dolomite, and minor amounts of phlogopite, olivine, zircon, ilmenite, and pyrochlore. Feed preparation consists of crushing to -31.75 mm (-1 M in.), rod milling in closed circuit with hydrocyclones to about 92% (-50 mesh), and two-stage cyclone desliming of the -50 mesh sands at 20 m. Weight recovery in the deslimed feed is normally 85 to 88% and the corresponding P2O5 recovery is usually about 90%. The deslimed feed is conditioned at 60 to 70% solids for 15 min at pH = 8-10 with 0.6 kg/t of causticized starch for iron oxide and calcite-dolomite depression. The conditioned slurry is diluted to 20 to 30% solids, about 0.2 kg/t of fatty acid or soap collector is added to the conditioner discharge, and the reagentized ore is subjected to rougher-scavenger flotation with additional fatty acid added to the scavenger float. The scavenger concentrate is returned to rougher circuit distributor, and the rougher concentrate froth is subjected to two stages of cleaner flotation to yield a final apatite concentrate analyzing 36 to 38% P205. Flotation recovery of P205 is, in general, above 90% when treating fresh carbonatite. The high-carbonate flotation tails normally analyze 1 % P2O5 or less and are suitable for portland cement production. The marine deposits. Types 1 and 2 of central Florida are representative of enormous reserves of phosphate rock that will undoubtedly account for much of the world's production in the near future. Until very recently the sedimentary deposits high in carbonate minerals (Type 2) have not been considered reserves due to the difficulty in making a francolite-carbonate separation. Although no commercial plant has yet been built to beneficiate Type 2 ore, laboratory and pilot plant data indicate the process is viable. If so, the reserves of Florida and similar deposits throughout the world will be substantially increased. A discussion of the beneficiation of these two types of sedimentary deposits and the relation of the resulting concentrates to the fertilizer industry of the United States is the subject of this paper.

Jan 1, 1981

By S. R. B. Cooke, S. W. Clark

Adsorption of calcium and magnesium by quartz was determined over a wide pH range using flame photometry for solution analysis. A parallelism was noted between calcium adsorption at alkaline pH and flotation of activated quartz by means of various fatty acid collectors. Abstraction of calcium from 100 ppm solutions increased above pH 10.5 until all of the calcium was removed at pH values between 12 and 12.5. Calcium was desorbed from the quartz over the pH range 12.5 to 13.0 and returned to the solution. Precipitation of magnesium hydroxide prevented measurement of magnesium adsorption above a pH of 9.9. A calcium adsorption isotherm determined at pH 9 matched measurements of barium adsorption by other investigators over the range where adsorption corresponded to the equation of a Freundlich adsorption isotherm. In accordance with the Gouy-Chapman theory for adsorption in the diffuse layer, adsorption of the divalent cations under these conditions was four times the adsorption of monovalent sodium. Activation of quartz by multivalent metal cations in flotation using anionic collectors has been studied by many investigators. The occurrence of activator cations in the water of flotation mills makes depression of silaceous gangue very difficult. Alternatively, in some flotation systems it is practical to cause activation of quartz so that it is floated from the desirable mineral values. The present study was initiated to investigate the activation of quartz by measuring adsorption of calcium and magnesium ions as a function of solution pH. Early empirical tests showed that quartz would be activated to flotation using anionic collectors if any of a number of divalent or trivalent metallic cations were present in the pulp.1*2 Subsequent studies by Clemmer,3 Cooke and Digre,4 Cooke,5 Schuhmann and Prakash,6 and Cooke, Iwasaki, and Choi,7-8 showed that flotation depended strongly upon the alkalinity of the flotation pulp, the concentration of the activating cations, and the chain length and structure of the organic collectors used. The concept of the electrical double layer has been applied to the case of the quartz-aqueous solution interface by Gaudin and Fuerstenau,9-10 and by de Bruyn 11 to explain the activation of quartz by multivalent metal cations. Studies of the surface of quartz by Gaudin and Fuerstenau9,10,12 and by Li " using the streaming potential technique contributed much information on the electro kinetic condition of the surface of quartz in the presence of various organic and inorganic ions. Measurement of adsorption of ac-

Jan 1, 1969

By Edmond S. Miksch

The morphology and growth rate of ice grown in supercooled water are markedly affected by convection of the water. A dendritic ice sheet with water flowing past the dendrite tip exhibits deflection of the dendrite spine toward the upstream direction, accelerated growth of secondary spines on the upstream side, and suppression 01" secondaries on the downstream side. Flow causes a thin disk to become corrugated, the corrugations being parallel to the flow. Flow causes an increase in the growth rate of the ice. IF a small seed of ice is placed in slightly supercooled water, it grows initially as a disk with the axis of the disk parallel to the c axis of the ice crystal.' It appears that growth in the c direction is inhibited, while growth occurs with equal facility in all directions in the basal plane. It appears that growth rate as a function of interface temperature is very nearly equal for all directions similarly oriented relative to the c axis. Subsequent to the discoid growth, branching occurs and dendrites develop. The primary dendrite spines grow parallel to the six equivalent a axes of the crystal. Secondary, and in some cases, tertiary spines also grow in these directions. The highly anisotropic: dendritic growth indicates that there must be some finite difference of growth rate for different directions in the basal plane. These differences must be quite small, however, since if they were large, the discoid mode would not occur. Hence, it was expected that the dendrite growth direction could be deflected from the crystallographic direction by perturbation of the thermal field at the dendrite tip. Experiments were done in which perturbation of the thermal field was accomplished by causing the supercooled water to flow past the dendrite tip. The flow direction was perpendicular to the c axis of the crystal, and was perpendicular to the primary spine of the unperturbed crystal. Supercooled water was supplied by a 15 cm cubical copper box, which was refrigerated and insulated so it could cool water to temperatures down to —2oC, and maintain the temperature constant to O.l°C for the duration of a run. A lucite channel of rectangular cross-section, 12 by 24 mm, was mounted horizontally in the box, with one end open so water could flow into it, and the other end leading out through the wall of the box to a length of tubing leading: to an orifice plate 123 cm below. cnunMn s MIKSCH, MemberAiMe, formerly Research Associate, Research Associate, Fig. l(b)—Vertical section of apparatus A horizontal cross-section is shown in Fig. l(a), and a vertical section is shown in Fig. l(b). Means for observing the ice are shown in Fig. l(a). Collimated light passes through the ice sheet and forms an image on the ground glass screen. A lucite box containing dry air was employed to prevent condensation. Ice of the desired orientation was provided by the seed holder shown in Fig. l(b). This device was made of lucite, and had a reservoir in which ice could be frozen by placing it in a freezer. This reservoir com-unicated with the outside only through a narrow gap between two sheets of lucite. The seed holder (after ice had been washed off its exterior) was immersed in the tank of supercooled water, the narrow gap terminating in a slot in the top of the flow channel. Ice growing through a thin water layer in the gap between the two sheets of lucite was oriented so its c axis was perpendicular to the sheets. This orientation is an application of a growth phenomenon2 which causes ice growing along a smooth solid surface in supercooled water to orient itself so its c axis is normal to the surface. After the ice grew into the channel, further orientation was necessary, since the direction of the a axis

Jan 1, 1970

THE Boston meeting, August 29-31, was in many ways one of the pleasantest the Institute has enjoyed in years. Much hard work had been done by the committee, and with excellent results. The program had been purposely restricted with the idea that a smaller, more homogeneous audience formed the best basis for a regional meeting, and the event fully justified the plan. The one hundred and sixty-three members and guests attending were dominantly interested in geophysical methods or their application, and, despite the highly technical character of the papers and the unusual heat, attendance and interest in the technical sessions were well sustained. The exhibition of geophysical instruments and aerial maps added greatly to the meeting.

Jan 1, 1928

By Paul E. Richardson, Edwin E. Maust

Cyclic voltammetry and surface potential (photovoltage) measurements have been carried out on galena electrodes in sodium tetraborate solutions with added HC1 and NaOH to adjust the pH over the range 2 to 13. The first technique shows that the surface species formed on moderate anodic polarization and reduced on subsequent cathodic polarization are the same over the entire pH range. At anodic potentials, a soluble metal species and excess sulfur are formed; at cathodic potentials, sulfur is reduced to a soluble species. More importantly, excess surface sulfur is formed spontaneously under zero current conditions in alkaline solutions. This has been shown to occur on both polished surfaces and on virgin surfaces produced by in situ cleavage under the electrolyte. The photovoltage gives some insight into the charge and potential distribution at the galena surface. This is found to depend on past electrochemical history and the n- or p-type semiconducting character of the electrode and is interpreted in terms of changes in the surface stoichiometry that occur during reduction or oxidation. The effect of surface stoichiometry on subsequent xanthate interactions is discussed.

Jan 1, 1976

By AIME AIME

AN enthusiastic crowd, cheerfully confident that the upturn in the oil industry has arrived, gathered in Los Angeles on Sept. 29 for a Petroleum Division meeting arranged by the Southern California Section. The assembly room of the California Oil and Gas Association was the place of meeting. H. Norton Johnson was in the chair for the morning session, with about eighty members and guests present. Four papers were presented before lunch and a fifth, on electrical coring, was withdrawn as the work on which it was based is still confidential. Joseph Jensen read his contribution on the "Kettleman Hills Middle Dome Unit Plan" and, as he had an active part in framing the plan, his outline and discussion of it was authoritative and informing. J. H. Woods asked concerning the operation of the casing-head gasolene plant under the plan and was informed that one company would operate the plant and royalties would be paid participating companies

Jan 1, 1933

By Alan Stanley

The MacIntyre Development of the National Lead Co. is located at Tahawus, N. Y. The operations involve the mining and concentrating of a titaniferous iron ore to produce an ilmenite concentrate and a magnetite concentrate. Construction of the MacIntyre plant was commenced during the summer of 1941, when world conditions threatened to cut off the supply of Indian ilmenite. An open pit mining operation was developed and the crushing and milling equipment put in operation in July 1942. A general description of the operation was given in the Adirondack Issue of Mining and Metallurgy for November 1943. The metallurgy of the mill operation was described by Mr. Frank R. Milliken,* Plant Manager, National Lead Company, MacIntyre Development, and presented at the AIME New York Meeting, February 1948.

Jan 1, 1949

By Thomas A. Steven

Most mineralized areas in the central San Juan Mountains, Colorado, are associated with the youngest subsidence structures in a large volcanic cauldron complex that formed concurrently with eruption of the surrounding ash-flow field. Two local types have been recognized: (1) fissure-vein deposits along faults characterized by relatively late movement, and (2) hydrothermally altered and mineralized areas associated with postsubsidence Fisher Quartz Latite centers. The first type has provided most production in the past; the potential of the second type has yet to be adequately tested.

Jan 1, 1968

By Noah Fields Drake

This paper is devoted chiefly to the coal-fields of the western part of the province of Chili and the eastern part of the province of Shansi; but the outline of this belt will give some idea of the extension of the coal-fields over northeastern China. This part of China is topographically divided into: (1) the mountainous peninsula of eastern Shantung; (2) the coastal plains, extending W. and SW. from the gulf of Pechili; and (3) the mountains and table-lands N. and W. of the coastal plains. The plains extend N. and W. from the gulf to within from 10 to 25 miles of the Great Wall, while their SW. extension covers western Shantung and reaches W. along the Yellow river almost to the southern boundary of Shansi. A line joining the mapped coal-fields, shown in Fig. 1, almost gives the western boundary of the plains; since these areas lie on the border of the plains—except the Tsê Chou field, which is on the table-land, 20 to 25 miles from that border. The coal-fields which have been mapped and investigated by the author are shown in Fig. 1. The one at and around Tongshan is known as the K'ai-p'ing coal-field; the one W. of Peking has been called the Wang-p'ing coal-basin; the one SW. of Pao-ting and N. of Chêng-ting may be called the Lingshan coal-field; and the one at and around Tsê Chou is known as the Tsê Chou coal-field. I. The K'ai-p'ing Coal-Field. As is shown in Fig. 2, most of this field lies in the coastal plains, and is therefore covered by alluvium and loess, which have buried the older rock-beds, and the more gentle and older topographic outlines, to such an extent that most of the re-

Jan 1, 1902

By AIME AIME

PETROLEUM technology was the sole subject of discussion at the meeting of the Petroleum Division at the Baker Hotel, Dallas, Texas, Oct. 6-7, except for the brief talks by President Becket and Secretary Parsons at the dinner on Friday evening. Even on this occasion, following the scheduled official features, it was in order to talk "shop." W. E. Wrather and E. A. Stephenson, respectively Chairman and Secretary of the Division, had planned for a meeting of this nature and by preference, apparently, the 122 who registered fell in with the scheme wholeheartedly. Not because the competent local committee had not provided for it, but by choice, the members just did not sign up for entertainment or field trips, but did attend largely the three technical sessions and engage in earnest discussion of the approximately dozen excellent papers. In this connection, and without question, the high lights of the meeting were the papers by Morris Muskat and R. D. Wyckoff, and Prof. W. K. Lewis. The former, entitled, "A Theoretical Analysis of Waterflooding Networks," had been entirely demathematized by the authors for presentation at this and the Los Angeles meetings; the author of the latter, which was on the "Physical-chemical Relationships of Hydrocarbon Gas-liquid Mixtures at High Pres¬sures," had airplaned to Dallas in the company of Dr. H. D. Wilde from Chicago in order to present his paper at the final session on Saturday morning.

Jan 1, 1933

By Benjamin F. Tillson

THE past seven years, and 1937 in particular, have witnessed the return of New Jersey iron mining to a place of importance. Following the World War period, little mining was done for several reasons. The properties were operated by small merchant furnaces whose demand was not sufficiently large to warrant large-scale methods with their attendant low operating costs. Under those conditions, the ore produced could not compete with that from the Great Lakes. However, when on Nov. 1, 1.929, the Alan Wood Steel Co., of Conshohocken, Pa., leased the Scrub Oak and Washington properties at Mine Hill and Oxford respectively, they made radical changes in the mining and milling processes which greatly reduced the cost of production and pointed the way to a renewed interest in mining in New Jersey. The following factors have been advanced as influencing the reopening of New Jersey mines:

Jan 1, 1938

By T. R. Wright

IN few mining regions in the world are the ores so varied and complex as in the Andes of central Peru. Consequently, in few localities is one company engaged in so many and such diverse metallurgical operations as the Cerro de Pasco Copper Corp. Concurrent with the mining of complex lead-zinc ores in Peru, and the consequent expansion of the Corporation's metallurgical activities, a department of metallurgical research was established in 1927 at La Orova. Facilities were provided for research in ore dressing, hydronivtallurgy pyrometallurgy, electrometallurgy, and analytical chemistry. In addition to laboratories. various pilot plants were built, including a concentrator, leaching plant, "by-product" smelter, and electrolytic refineries. These pilot plants are not diminutive units; they are designed and equipped as semicommercial plants for operation on a continuous 24-hour basis thus assuring the duplication of pilot plant results in actual practice. In general, the sequence in the development of metallurgical operations hasbeen as follows: (1) investigations in the laboratory to determine the most effective and economical method of treatment; (2) continuation of the research project on a pilot-plant scale when the evaluation of the laboratory

Jan 1, 1945

By Paul Weir

BLEACHING clays have been used extensively in the oil-refining industries for a number of years. Their use in water purification is relatively recent and less extensive. They are frequently classified as (1) those naturally active and (2) those active after artificial activation with acid. Fuller's earths fall within the general group of bleaching clays and gradually the commercial term "fuller's earth" has been applied to natural clays originating, for the most part, in the south-eastern section of the United States. Bentonitic clays are usually classed as activable and are prevalent in the southwestern section of the United States.1 Bleaching clays vary considerably in chemical and physical properties throughout the country, or even in different parts of one deposit (Table 1). TABLE 1.-Physical and Chemical Composition of Different Types of Clays Composition, Per Cent Constituents and Properties Bentonite Fuller's Mud Clay (Wyoming) Earth (P Peak)' (Alluvial) Silica (SiO2) 60.0 69.6 61.67 Alumina (Al203) 19.0 14.3 20.34 Ferric oxide (Fe203) 2.8 3.90 7.70 Titanium oxide (Ti02) 0.13 0.70 1.01 Lime (CaO) 0.5 0.80 0.00 Magnesia (MgO) 2.0 1.00 0.24 Soda (Na2O) 2.4 0.40 0.31 Ignition loss 4.7 6.77 8.51 Moisture content 8.0 10.0 20.0 Isoelectric point, pH 9.2 9.2 6.5 Average swelling volume 15.0 0.0 0.0 Weight per cubic foot, lb 55.0 40.0 65.0 Material passing 200-mesh sieve, per cent 90.0 85.0 50.0

Jan 1, 1939

By AIME AIME

THE best meeting ever held, was the opinion expressed by a number of those who attended the annual meeting of the Institute in New York, Feb. 18 to 21, and there was an atmosphere of friendliness and good fellowship about it that fully justified the feeling. In numbers it was not quite so large as last year and unless the Engineering Societies should build for themselves a new building it is probable that no meeting can be larger, in respect to numbers, than that held in 1928, which was only made possible by the circumstance that the eighth floor of the building happened to be, temporarily vacant at the time. The number of rooms available for -sessions that were provided when the building was built long ago proved inadequate, and it is only by the expedient of obtaining the temporary use of the board and committee rooms of other societies that it is possible to arrange for the over 40 sessions that must be spread over the four days of the meeting. The-fifth floor, where. a buffet lunch is served each-day, has reached its full capacity and it seems quite evident that any future development of Institute meetings must be along the lines of quality, not size.

Jan 1, 1929

By G. C. Wallick, J. S. Aronofsky

This paper presents an experimental verification of numerical solutions of the differential equation describing the transient flow of an ideal gas through a porous material including gas slip effects. Several experiments previously proposed by one of the authors are described together with the correlation of the experimental results with the numerical solutions. Excellent agreement is shown between experiment and theory, thus demonstrating the validity of both the basic assumption made in the derivation of the differential equation and of the numerical solutions of the differential equation. INTRODUCTION In a recent paper,' one of the authors has discussed a numerical solution of the differential equation describing the unsteady flow of an ideal gas through a porous material. This paper was primarily concerned with the effect of gas slip on the flow behavior. In steady state measurements, Klinkenberg2 and others have observed that the apparent gas permeability Kn of a porous material may be expressed as a linear function of the reciprocal average pressure 1/P of the form, ka = b + m/P........(1) where the intercept b is a constant for a given porous material and the slope m is a constant for a given porous material-gas combination. Aronofsky1 assumed that Equation (1) could be used to describe transient flow if P was replaced by the average pressure in an infinitesimal volume element. A number of numerical solutions of the resultant differential equation were presented and specific flow experiments were proposed as a means of testing the numerical solutions. The purpose of the present paper is to describe the results of several of these experiments and the correlation of the experimental data with the results of the numerical analysis. Reference should be made to the previous paper' for details of the mathematical and numerical analysis. EXPERIMENTAL PROCEDURE A simplified schematic drawing of the experimental apparatus is shown in Fig. 1. An 8.89 cm diameter limestone core of length L = 14.82 cm was mounted in a conventional rubber sleeve permeameter cell. The external sleeve pressure in this cell was maintained equal to 500 psig during all experimental tests, thus permitting only longitudinal flow through the core. One end of the core, X = L, was connected to an adjustable cavity of volume V as well as a pressure gauge or manometer. The other end of the core, X = 0, was connected to a Nullmatic pressure regulator which was in turn connected to a nitrogen cylinder or vacuum pump. In each experiment, the core and adjacent dead volume were charged with nitrogen to a uniform gas pressure P1. The pressure at X = 0 was then suddenly raised or lowered to a constant pressure P, and the resulting pressure buildup or pressure decline at X — L was recorded as a function of the time. The porosity + and the permeability constants m and b were determined using the transient method which was suggested by the results of the numerical analysis and which was described in the earlier paper.' The following average values for these constants were obtained as a result of 19 separate evaluations: 171 -0.259 2 0.005 md-atm; b = 0.374 5 0.008 md; and F = 0.098 ± 0.005*. It should be noted that in order that transient phenomena will be slow enough to be observed conveniently, it is desirable to use a porous material of very low permeability, e.g., less than I md. Moreover, it is in this low permeability range that the gas slip effects are most significant. Thus, such a low permeability sample is very suitable for use in an experimental verification of the numerical solutions previously described.

Jan 1, 1955

By R. L. Bowron

GROWING use of basic slag in the agricultural industry is of special interest and importance to the iron and steel industry of the Birmingham district, providing an increasing outlet for this by- product. Such use of basic slag was first developed in England about fifty years ago where it soon became wide- spread. About twenty years ago the Tennessee Coal, Iron & R. R. Co. began its production in the United States after exhaustive tests had demonstrated its high value here as in Eng- land. It is particularly valuable on heavy clay and acid soils, improving their physical condition, increasing their alkalinity where that is desirable, and providing soluble phosphate and small amounts of manganese to soils deficient in these respects. Its use in agriculture is growing as its advantages are becoming more widely known.

Jan 1, 1937

By Harry M. Mikami, Harold A. Heiligman

The term chromite is often used to cover all chrome ores and concentrates which are the designations actually employed by most industrial users and producers. Chromite is, of course, the predominant mineral in chrome ores which are aggregates of chromite and gangue minerals, most commonly magnesian silicates. Most chrome ores now used are petrographically chromitites which is a rock, rather than an individual mineral term. The title of this chapter, following past usage, is meant in the broad sense. Chromite is the only primary commercial source of chromium. This book is intended to deal only with nonmetallic minerals and rocks. Chromite uses are both metallic (ferroalloys) and nonmetallic (refractories and chemicals), but any discussion of mineralogy, geology, and mining is common for all types. A number of the major commercial ores are interchangeable, and their uses are determined by economic considerations. Mineralogy COMPOSITION [Chromite is a term embracing a wide range of chromium-bearing spinel*-group minerals the compositions of which can be expressed as (Mg,Fe2+)0.(Cr,AI,Fe3+ )203.t This can be further generalized to R2+O.R23+03 and the molecular RO: R,03 ratio is generally close to one. The exact composition may be arbitrarily expressed as a solid solution of six end-members, MgAI2O4, MgCr2O4, MgFe2O4 FeCr2O4, FeA12O4, and Fe2+.Fe23+04 with the proportions of each stated or plotted in the six-cornered prism of Johnston and Stevens61 or this scheme may be simplified to comprise only three endmembers making up a composition triangle, Fig 1. [ ] FIG 1-Triaxial composition diagram showing molecular compositions of chromites listed in Table 1. The RO.Fe2O3 corner includes Ti02 norms listed in the table. Note that the high-alumina chromites (1, 2, 3, 9), form a cluster well apart from the high-Cr2O3 chromites. There is a tendency for high-iron chromites to be higher in Fe2O3 + TiO2 but it is not a consistent or systematic relationship. The MgO/RO ratio must also be known to characterize the chromite chemically. Simplest and most convenient method is Thayer's' in which a chromite such as (Mg.65Fe.352+)O.(Cr.40Al.50Fe.103+)203 would be written as (Mge,) Cr eAlo. The molecular pro- portions of ferrous and ferric oxides can be seen at a glance as the divalent and trivalent oxides]

Jan 1, 1960