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By D. T. MacRoberts

This paper embodies the results of theoretical studies concerning gas reservoirs, especially the effect of drilling programs of various intensities upon pressure depletion and ultimate recoveries. The primary objective has been to determine the net quantity of recoverable gas that could be obtained as a result of each additional well, in comparison with the gas . that might be secured from a single well ideally placed with respect to both acreage and geological structure. No method is yet known whereby the relative merits of intensive and sparse drilling can be compared experimentally; a reservoir must either be drilled closely or developed with wide spacing, but both programs cannot be conducted simultaneously. Hence, the analytical method seems to be the only approach to the problem. While the present state of our theoretical knowledge does not offer a precise solution to the problem of gas flow in sand bodies, it takes such appropriate cognizance of the limitations of the methods used as to restrict any answer obtained to the realm of engineering accuracy. In solving the problem for the average gas field, it was found that practically the same answers resulted as to pressure distribution, regardless of the size of the drainage radius, even though the latter was assumed to vary from a few feet as a minimum to that of the entire reservoir as a maximum. Such limits represent extreme possibilities; therefore, the practical conditions that are associated with normal development programs, in which wells are placed in the center of tracts varying in size from 40 to 640 acres, will of necessity result in less extreme variations than those indicated in the tables accompanying this paper. Stated more concisely, the amount of gas unrecovered at abandonment (of the particular field used for illustrative purposes) will lie somewhere between 4.6 and 6 per cent of the total original content, no matter how intensively the field is drilled. Gas reservoirs may be divided into two general types, those in which the energy is intrinsic, and those of which the energy is extrinsic. † The first type contains energy in the form of a compressed gas, which expands

Jan 1, 1938

By R. A. Esmonde

This paper describes the building and testing of a prototype welded aluminum truck body to a new design concept. The results of these tests are given along with an outline of further developments in the design and field application of aluminum bodies. The results of field service history are recorded with special reference to types of mining operations, service performance, wear, maintenance and economics of operation. Mention is made of current U.S. usage and predictions given as to future development of aluminum bodies in the mining industry. The use of aluminum for off-highway truck bodies in hauling rock for the mining and construction industries is by no means the novelty that it may seem. In 1932 an aluminum unit proved very satisfactory in service on the Hoover Dam project but at that time the only high strength aluminum alloys available were not weldable and with the high cost of construction, a sound economic case for an aluminum body could not be made. After World War I1 great advances in aluminum welding techniques, using the inert gas shield, combined with the development of high strength alloys with good welded properties and welding characteristics changed the whole picture. Welded aluminum bodies were rapidly developed and by 1958 attention was again focused on the use of aluminum for off-highway truck bodies. EARLY DEVELOPMENT WORK In 1959 Alcan, the Aluminum Co. of Canada, embarked on an extensive development program to prove the durability and economics of aluminum truck bodies for the mining and construction industries. The first step was to design a prototype aluminum body which took particular advantage of the fact that the modulus of aluminum is only one third that of steel. This means that within the elastic range, aluminum moves three times as much as steel which makes it more flexible and capable of absorbing much greater impact shocks. A body was built and mounted on a 22-ton truck and taken to the Jeffery Mine of Canadian Johns Manville Company at Asbestos, P.Q., Canada. Very little information was available as to the order of stresses that were set up in off-highway truck bodies and so it was therefore decided to carry out a test program to find out this information.

Jan 1, 1969

By William E. Ford, Edward Salisbury Dana

IN the representation of crystals by figures it is customary to draw their edges as if they were projected upon some definite plane. Two sorts of projection are use8; the ah- graphic in which the lines of projection fell at right angles and the chirographic where they fall at oblique angles upon the plane of projection. The second of these projections is the more important, and must be tr2atcd here in some detail. Two points are to be noted in regard to it. In the first place, in the drawings of crystals the point of view is supposed to be at an infinite distance, and it follows from this that all lines which are parallel on the crystal appear parallel in the drawing. In the second place, in all ordinary cases, it is the complete ideal crystal which is represented, that is, the crystal with its full geometrical symmetry as explained on pp. 10 to 13 (cf. note on p. 13). In general, drawings of crystals are made, either by constructing the figure upon a projection of its crystal axes, using the intercepts of the different faces upon the axes in order to determine the directions of the edges or by constructing the figure from the gnomonic (or stereographic) projection of the crystal forms. Both of these methods have their advantages and disadvantages. By drawing the crystal figure by the aid of a projection of its crystal axes the symmetry of the crystal and the relations of its faces to the axes are emphasized. In many cases, however, drawing from a projection of the poles of the crystal faces is simpler and takes less time. The student should be able to use both methods and consequently both are described below.

Jan 1, 1922

By Francis C. Frary

OF the five metals that now show the highest figures for annual tonnage production in the world, three (iron, copper, and lead) have been known and used by man for many thousands of years. The fourth (zinc) did not come into general use until the Middle Ages. Only the fifth (aluminum) is of, ultramodern origin, as far as mankind is concerned. Discovered in 1825, and first publicly exhibited at the Paris Exposition in 1855, aluminum was still so difficult to obtain that it was more expensive than silver, until the development of the dynamo provided cheap electricity and the development of the present electrolytic process for its production made it possible to make large quantities cheaply. Even today, the world production of aluminum is only about one per cent of the world production of iron, although about half that of copper by weight. The increase in production from a few tons to more than a million tons per year began with ,the development of the Hall-Héroult electrolytic process, which was first commercially operated by Mr. Hall's company, The Pittsburgh Reduction Co., in 1888. During the relatively short period of time that has elapsed since that date, it has been necessary to develop all the metallurgical and fabricating information required for the production of useful articles of the metal and its alloys, together with experience in both their production and their use, so as to be able to fit them satisfactorily into their proper places in our complex modern civilization. The fundamental properties upon which the usefulness of aluminum depends are its lightness, workability, resistance to corrosion,

Jan 1, 1953

By Edward G. Norton

The salt deposits of the Mississippi Embayment region present a problem of origin so genetically related to the larger problem of the stratigraphy and structure of the region that a discussion of the one necessarily involves or assumes an understanding of the other. For this reason, I shall summarize briefly our knowledge of this region, emphasizing the facts related to the subject of this paper. In so doing I shall make liberal use of the reports of the National and State surveys. Geographically that section of the United States known as the Mississippi Embayment region represents a great V-shaped area, extending from near Cairo, Ill., to the Gulf of Mexico, and including Louisiana, eastern Texas, all that part of Arkansas bordering the Oua-chita and Ozark mountains, western Tennessee, Mississippi, and a part of Alabama. This great section Professor Harris has described as structurally a pitching trough, its medial line being well represented by the Mississippi River. Outcropping along the border of this area are the Cretaceous and Tertiary formations, unconformably laid down on the hard Paleozoic rock sheets that show more or less plication, deformation, and faulting, depending upon their proximity to the nearby major uplifts. East and west of the Mississippi River the Cretaceous and Tertiary beds dip river- and coastward at angles greater than the slope of the land. "Waters entering along the outcropping edges of the Tertiaries and Cretaceous and following bedding planes southward are soon thousands of feet beneath the surface." As the sedimentation of the region progressed, faulting and slips occurred along planes of pre-Cretaceous weakness. Whether these movements were genetically related to the loading of this V-shaped area, as Professor Harris seems to think, is a question still to be settled. The accompanying map, Fig. 1, was taken from Bulletin No. 7 of the Louisiana- Geological Survey. It shows the regional distribution of the salines, as well as an alignment of the domes, which has been assumed to indicate faulting.

Jan 1, 1915

By Edward Keller

In order to conduct intelligently the sampling of copper of various forms and grades, solid or in molten furnace-charges, a knowledge of this subject is essential. Yet figures and tests have been persistently withheld from publication, and the books at our command give us little or no information in this regard. This gap in our copper-literature has led to a series of experiments, the results of which are given below. Nearly all gold- and silver-bearing copper, destined for shipment, is cast into the form of bars or pigs. For the sampler, the question arises, Does copper, so cast, remain homogeneous ? If it does, sampling should present no difficulties; but, from experience, we know that this is not the case, and we are thus led to study the behavior of the precious metals arid impurities in copper when the latter changes from the molten to the solid state. For the purpose of the experiments here described, all available grades of copper were selected, and all of them mere subjected to the same conditions, an important requisite for proper comparison. The molten copper obtained directly from reverberatory- and blast-furnaces was cast in a cast-iron mould, the sides and bottom of which were 1 inch thick, and would, therefore, give the copper a fair length of time to chill. The inside dimensions of the mould, and, consequently, of the block of copper obtained, were: length, 10 inches; width, 9 inches; and depth, 5 inches. Fig. 1 illustrates the method employed to obtain samples from these blocks. A was cut away, and the face so produced BALTIMORE COPPER WORKS,

Jan 1, 1898

By W. E. Keck, Paul Jasberg

THERE is a considerable tonnage of iron ore in the Menominee Range of Michigan that is unsalable only because it has too large a content of sulphur. Beneficiation of such ore is economically desirable, as a relatively large quantity of finished concentrate would be obtained (deleterious sulphur mineral content being generally less than 5 per cent) and because large blocks of such ore have been developed incidentally during search for low-sulphur ore. Research on the flotation beiieficiation of these high-sulphur ores consisted of: (1) a study of the flotative properties of the principal minerals in a nearly pure state, (2) flotation of synthetic mixtures of these pure minerals and (3) application of this experimental information to samples of the ores. Gypsum in iron ores is extremely deleterious; but when sufficiently free from impurities it is a valuable commodity. In 1934, the United States produced 1,500,000 tons of calcined and uncalcined gypsum valued at $13,700,0001. Of this quantity and value, Michigan produced approximately 19 per cent4. Thus this investigation may also prove to be of interest in connection with the gypsum industry if minerals separation, such as flotation, becomes necessary in the future processing of gypsum. Data on the flotative properties of gypsum would also be of interest to the science of flotation because such information has been extremely limited. The technical literature reveals one reference to the flotation of gypsum, in which was discussed the use of the mineral, with several others, to determine the relation between the floatability of minerals and the pH of the flotation solution2. This investigation necessarily was not comprehensive in regard to gypsum, but it did show that the mineral could be floated with oleic acid under varying pH conditions.

Jan 1, 1937

By Arvid Holst Mortensen

The rational exploitation of deposits for cement manufacture requires evaluation of the material, the planning of the quarrying and the right choice of quarry machinery. By using a computer for all evaluations and planning work the optimal recovery of material is arrived at and a quarry layout - and machinery is decided upon. The result will be uniform production throughout the lift of the deposits using a rationally chosen quarry equipment.

Jan 1, 1977

By Charles R. Holmes

MORE than 70 igneous pipes and dikes are known to occur in Cambrian sediments throughout an approximately circular area of about 75 sq miles, in southwestern Ste. Genevieve County and southeastern St. Francois County, Mo., across the southern portion of the Farmington anticline, which is outlined in fig. 1. From evidence obtained from fossil fragments taken from some of the intrusives, and from the similarity in composition of the more basic intrusives to those of known age in surrounding states, these pipes and dikes are believed to be at least post-Devonian and probably Cretaceous in age. As first postulated by Rust[1], these intrusives are believed to represent explosion tubes, or diatremes, punched through great thicknesses of solid rock by gaseous pressure.

Jan 11, 1950

Jan 1, 1905

By Cyril Stanley Smith

BETA brass (consisting of approximately equal atomic proportions of copper and zinc) exists as a random solid solution at high temperatures, but at low temperatures [ ] an ordered structure is stable, with the copper and zinc atoms occupying alternate sites on the body-centered-cubic lattice. On cooling, ordering commences at a temperature of 450° to 470°C., depending on the composition. The degree of ordering progressively increases at lower temperatures until it becomes virtually complete at about 100°C. The electrical resistivity of the alloy illustrates the changes clearly (Fig. I). This type of reaction has been a favored subject for study by physicists. An [ ] excellent summary of the theory is to be found in a paper by F. C. Nix and W. Shockley.1 All published data on electrical conductivity, specific heat and other properties agree in indicating that the ordering reaction in beta brass takes place so rapidly that it cannot be prevented or even retarded by quenching. With most ordered alloys, cold-working induces disorder and

Jan 1, 1942

By Weldon B. Smith

When faced with excavating vast amounts of overburden at its surface coal mining operation in Centralia, Wash., the Washington Irrigation and Development Co. (Widco) chose to utilize a bucket wheel excavator and shiftable conveyor system. In the early 1970s, Widco-a subsidiary of the Washington Water Power Co.-held reserves of sub-bituminous C coal estimated at some 180 million tons (200 million st). Subsequent investigation of the overlying land formations revealed the need to excavate millions of bank cubic yards of material as part of the mining plans.

Jan 7, 1979

By Michael B. Kahle, Fred J. Scheaffer

Production scheduling, along with production planning, provides projections of future mining progress and time requirements for the development and extraction of a resource. These schedules and plans are used by management as a means of attaining the following objectives (1) maintaining or maximizing expected profit, (2) determining future investment in mining, (3) optimizing return on investment, (4) evaluating alternative Investments, and (5) conserving and developing owned resources. The first four goals are generally concerned with mining costs, both capital and operating requirements, and as such, play an important role in production planning. However, this chapter is concerned with the fifth management objective of resource development in order to conserve and perpetuate the corporate entity. The following discussion is based on the premise that detailed economic evaluations and market surveys have been performed and analyzed and that the results indi¬cate a viable project.

Jan 1, 1979

By C. Harries

The mechanism of blasting and the effect that blasting has on rock properties including the generation of new cracks and the opening of existing joints is discussed and compared with changes in seismic velocities. .Knowing the extent of blast induced damage and the overall stable slope angle it is shown that it is possible to design blasting so as not to induce any damage behind the toe of the blast area. Practical methods of blasting to meet this criterion and the results of these blasts are then discussed.

Jan 1, 1983

By P. J. Conners, H. Colijn

Belt conveyors have proven themselves for many years as a dependable and low cost method of moving bulk materials at high flow rates. The success of a belt conveyor system greatly depends on the initial loading of the material on the belt. If the material is loaded on the belt at the center, at the same speed and without impact, then about 90% of all belt conveyor problems would disappear. Proper belt loading is primarily determined by the engineering and design of the conveyor transfer point. Some general design criteria required for proper transfer of materials from one conveyor to another are established and discussed. Specific attention is given to loading chutes and skirting.

Jan 1, 1973

By O. Jay Myers

The war effort has furnished the necessary impetus for better magnesium foundry practice. Four or five years ago, there were but a few formulas in general use for core-sand mixtures for magnesium castings. Certain sands, binders, and inhibitors were specified and the proportions of these materials in each mixture were maintained between very narrow limits. As more and more war industries entered the field, much research was carried out and methods and practices were improved. Magnesium founding is still in a state of flux; therefore it is not uncommon to find one foundry spraying inhibitors on its cores, and another foundry using sand mixtures with incorporated protective agents. The basic core or dry-sand mold mixture for magnesium in use today is compounded with sand, core oil or resin binder, cereal, and moisture. Core oil or resin binder are added for baked strength while the cereal binder and moisture are for green strength. The normal mixtures (based on the weight of the sand) contain from o.5 to 1.5 per cent of both cereal binder and core oil, and the moisture content variesbetween 1.5 and 5 per cent. The ratio of core oil to cereal binder varies from 60:40 to 40:60, while the correct amount of moisture depends upon the method of coremaking. Protective Agents In all magnesium practice, protective agents are used in conjunction with the core and molding sands to prevent oxidation of the metal. The use of these inhibitors is not novel, but publications covering this field are not entirely adequate. Beck1 says: Magnesium alloys decompose water to form magnesium oxide, hydrogen being liberated in the process (Mg + H2O ? H2 ?+ MgO). This reaction results in the blackening of the skin and the appearance of areas of porosity on the casting surface, the cavities of which are filled with a grey oxide powder (these are termed 'burns'). Although sand cores for magnesium castings are thoroughly dried during the baking cycle, burning will take place on the casting5 unless the metal is protected properly. This type of burning is more difficult to define than the "water-magnesium" reaction cited by Beckl A possible explanation may lie in the following equation: 2Mg + O2—> 2MgO Here, the source of the oxygen is not water, but the air in the mold cavity, together with the chemically combined oxygen in the core-binding media. Generally, two methods are used to prevent this reaction from taking place.

Jan 1, 1945

By Noah Fields Drake

During July and August, 1899, the writer took advantage of an opportunity of going to Shansi to gather some information concerning the geology and value of the already famous coalfields of that province. The long journey, mainly on slow river-boats, and the limited time at command, allowed only about ten days of work to be done in the coal-fields around Tsê Chou. The geologic structure and the rock-formations were found to be simple and quite regular, so that in that time the accompanying sketch-map (Pig. 1) was made, and a fairly good idea of the distribution of the coal and general geologic features was obtained. The map was made by measuring a base-line about three-quarters of a mile long, triangulating for principal points over the field, and filling in the details by rapid sketches. The few elevations marked on the map were taken with an aneroid barometer. Only a few of the great number of towns and villages that are within this densely populated area are shown; and the coal-mines indicated are not the only ones within the area, but the ones where most of the following information about the coal was obtained. The value of this coal-field was first clearly set before the scientific and commercial world by Baron von Richthofen,* who made a geologic reconnaissance of Shansi in 1870. Since that time the hostile attitude of the Chinese government and people towards foreigners and their enterprises has kept the coal-fields from being developed. But the last few years of rapid change in the conditions of China have at last apparently opened a way for the exploitation of this coal-field. The Peking syndicate, a joint English-Italian company, now has concessions from

Jan 1, 1901

By D. R. McCord

Data of a known statistical quality has been successfully used in a system of conventional fluid mechanics equations essentially free of empirical "conformance factors to prediet early detailed field 03 in a reservoir where gravity drainage is important and oil and rock properties vary con. siderably. The system is useful where comparative recovery predictions for one or more cases of natural depletion and gas cap pressure maintenance are needed and the reservoir is not too heterogeneous. INTRODUCTION Many authors, have examined various facet* of the gravity drainage-gas cap pressure maintenance problem over the last several years. Two of them. Burtchaell and Elkins, have published practical studies. In the case described in the present paper the best development and operating plan for one of the important reservoirs of the Bolivar Coastal Field in Western Venezuela was urgently needed. It was requested that sound comparative economics be presented along with an engineering evaluation of no additional drilling, maximum drilling. several cases of gas pressure maintenance, of water flooding and combination cases. A rapid analysis of the effect on recovery of the range of crude and rock properties indicated that none of the published methods using average properties would yield adequate comparative predictions. This paper covers the predictive system developed to deal with natural depletion and gas cap pressure maintenance. The large amount of data available for this field permitted statistically reliable correlations to be made of most rock and oil properties, and the evident smooth areal variations of these properties encouraged the construction of a lineal mathematical model of material balance and fluid flow equations, which could be manipulated by a modified iterative procedure. The manipulation is much more adaptable to computing machines than manually operated calculators and subsequent studies have been prepared for the IBM Card Program Calculator. A matrix as opposed to linear model has been tentatively worked out by other members of our group to deal with more heterogeneous reservoirs. It is more adaptable to computers such as IBM-701 or the Remington-Rand Univac. In 1950, when the system reported below was developed, no rapid computing machines were available to the author. Their existence and promise encouraged an initial approach by hand. Some details of oil and rock Property correlation are included because there are a surprisingly large number of medium-sized reservoirs in the world that show systematic property variations which are significant for a rigorous analycon. All large reservoirs (over half a billion barrels recovery) with which the author is familiar contain at minimum a significant temperature variation. Using the rock and oil property correlations, past pressure and production, the gas-oil ratio history of the reservoir was computed and found to be in close agreement with field measurements. The future performance under cases of natural depletion, gas injection of 100 MMcf/day, and of 130 MMcf/day, was then computed; a 70 MMcf/day case was also carried far enough to provide data for comparative economics. The 130 MMcf/day case proved to be the most attractive. A 50,000 horsepower gas turbine driven centrifugal compressor plant to take this quantity of adjacent field gas from 30 to 1,950 psia and inject it into the reservoir is under construction. The total cost of the project will exceed 20 million dollars.

Jan 1, 1953

By Hans Allenius, R. T. Hukki

This paper describes in quantitative terms the effect of sharpness of classification on the performance of the closed grinding circuit. The analysis is based on a large number of laboratory experiments designed to simulate the two most common industrial closed grinding systems. The experimental results show quantitatively the degree of improvement achievable by more efficient classification. In an earlier paper1 the senior author has presented a trend showing qualitative analysis of mill and classifier performance in tile closed grinding circuit. According to this analysis, the master key to a major improvement appeared to be effective removal of finished fine material from the classifier sands, or in other words, improved sharpness of classification, leading simultaneously to a substantial reduction of the circulating load. One purpose of this paper is to present the results of a quantitative investigation of the closed grinding circuit. Another is to set forth the essential pertinent variables revealed by the quantitative experiments carried out by the junior author. In the two most common systems of closed-circuit grinding, (1) feed to the circuit is introduced into the grinding unit, normally the ball mill, operating in closed circuit with the classifier; or (2) feed to the grinding circuit is introduced into the primary grinding unit, normally the rod mill, discharging into the classifier in closed circuit with the secondary grinding unit, normally the ball mill. In the following discussion, these two systems are analyzed separately in the indicated order. BALL MILL - CLASSIFIER CIRCUIT The Test Apparatus and Procedure: The test appara- tus included: (1) a F 195 mm x 220 mm laboratory ball mill rotated at a speed 77% of the theoretical critical speed, and a 7-kg batch of F 20 mm-F 50 mm steel balls; (2) a conventional 65-mesh test sieve and a Ro-Tap sieve shaker serving as a classifier; and (3) a Permaran instrument manufactured by Outo-kumpu Co. for surface area determinations by the permeability method. As no continuous closed-circuit experiments could be brought about on a laboratory scale, the process was broken down into alternating grinding and sizing steps in such a way that the new feed plus the returning sands always formed a batch of 1000 gm. For each selected grinding period and for each selected sharpness of classification the basic steps were repeated six times. Steady-state conditions were then reached. Crystalline vein quartz was used as a test material. Feed to the process consisted of -10-mesh fraction of this quartz crushed in rolls. This fraction included 15% of-65-mesh material. Experimental Results: The general flowsheet is shown in Fig. 1. Table I gives the essential data obtained representing steady-state conditions under the indicated set of variables. The table is based on 110 grinding experiments, 440 screen analyses and an equal number of specific surface area determinations. Fig. 2 shows the relationship between the cumulative net energy consumption and the cumulative number of mill rotations as evaluated by separate experiments. Note that this relationship is not linear but is instead represented by a slight curve. The data given in Table I are presented in graphical form as follows: Fig. 3 shows the produced -65-mesh material in grams per minute vs. time of grinding in minutes; the sharpnesses of classification at 65 mesh were 100%, 75% and 50%. It is clearly indicated that the highest-capacity figures call for relatively short grinding times and for the sharpest possible classification. Fig. 4 presents the specific surface area on the final -65-mesh product in square centimeters per gm vs. time of grinding in minutes. In conventional mineral dressing processes, a final product characterized

Jan 1, 1969

By H. M. Davis, T. S. Jones

A methodfor accelerating the reduction of a metal oxide by carbon monoxide is to incorporate in the reduction system a nonreducible oxide which has a strong affinity for carbon dioxide and will remove it from the product gases. The effectiveness of this method was investigated by veduction experiments on specially prepared powder mixtures of SrO-ZnO ("active'.) and SrCO3-ZnO (reference). Measurements at 750o and 677°C showed that the rate of reduction of ZnO by CO was as much as an order of magnitude greater in the presence of SrO. Under the experimental conditions at least as much CO2 as generated by veduction was absorbed when SrO was present. Enlzancernent of the veduction rate by SvO resulted from modification of' gaseous djfitsion processes. THE specific question posed in this investigation was whether the reduction reaction CO + ZnO - Zn(g) + COa [1] could be accelerated by incorporating strontium oxide into the oxide charge undergoing reduction. Provided the strontium oxide was active enough, it could remove carbon dioxide from the product gases of ( 11 and form strontium carbonate, thus modifying Reaction [ 1] to CO + ZnO + SrO = Zn(g) + SrCO3 [ 2] This study of the comparative rates of Reactions [ I] and [2] can be considered as a particular case of a general scheme for increasing the rates of reduction of metal oxides by carbon monoxide. The limits of applicability of this scheme are indicated in the simple thermodynamic analysis presented in the appendix. This analysis primarily dictated the choice of the system, CO-ZnO-SrO, employed in this investigation. In addition, it was thought that a study of this scheme by use of the CO-ZnO-SrO reaction system would be of special interest in view of indications in the literature1-3 that the gaseous reduction of zinc oxide is prone to rate control by diffusion in the gas phase. The distinction should be pointed out between this and other efforts to increase the rates of reduction reactions through the use of addition agents. Additions of a wide range of chemicals have been tried with de- grees of apparent success varying from slightly negative to highly positive. The reasons for making additions have included the use of salts to produce effects akin to catalysis,4, 5 the alteration of the microstruc-tural details of the reduction process (including solid-state diffusion),6-8 and the conversion of an en-dothermic reaction into one that is exothermic or autogenous.9-12 The means used to attempt alteration of the enthalpy change has commonly been to incorporate lime into the charge, so that heat is generated by reaction with either of the reaction products, carbon dioxide or water. The use of lime in this way makes endeavors such as that of Edstrom and Wiberg similar to the present one. Furthermore, the basic principle behind the present work has previously been set forth.13 However, a detailed investigation of the type of reaction described in this work does not appear to have been conducted. EXPERIMENTAL PROCEDURE From both conceptual and physical standpoints, Reaction [2] is to be considered as the sum of two reactions:

Jan 1, 1968