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By B. Ladanyi

The problem of rock behavior under concentrated loadings has been the subject of a number of studies in the past and has been receiving increasing attention by rock mechanics investigators in recent years. Its application covers various fields, but main interest in its solution has arisen in connection with the problems of drilling, bearing capacity, and rock testing. These widely different purposes and fields of interest probably have been one of the reasons why, in spite of the large amount of published experimental data and several theoretical studies, there are still many points which need further clarification. Another reason for this situation undoubtedly is due to the fact that the rock behavior in indentation is complicated by a great number of influencing factors. Experimental evidence shows that, depending on the rock type (mechanical properties, porosity), environment (ambient effective pressure, pore fluid, temperature), and the type of loading (indenter shape, initial embedment, load level, loading rate), the rock response to indentation may vary within very large limits. The widely different rock behavior has made it impossible up to now to treat the problem with a consistent single mathematical theory, but has required instead a series of simplified models covering only certain most important events in the failure sequence. As far as the theory of rock indentation is concerned, this chapter does not add much new information. Its main purpose is, however, to state the indentation problem in a general manner and to indicate which points need to be studied in more detail before its definite solution is attempted. Also, since excellent reviews of the state-of-art of rock indentation in drilling have recently been given,1-4 this will not be repeated here, and only references pertinent to the points of the problem under study will be quoted. The theoretical part of this study attempts to give a quantitative evalu-

Jan 1, 1972

By Fred C. Bond

MOST investigators are aware of the present unsatisfactory state of information concerning the fundamentals of crushing and grinding. Considerable scattered empirical data exist, which are useful for predicting machine performance and give, acceptable accuracy when the installations and materials compared are quite similar. However, there is no widely accepted unifying principle or theory that can explain satisfactorily the actual energy input necessary in commercial installations, or can greatly extend the range of empirical comparisons. Two mutually contradictory theories have long existed' in the literature, the Rittinger and Kick. They were derived from different viewpoints and logically lead to different results. The Rittinger theory is the older and more widely accepted. In its first form, as stated by P. R. Rittinger, it postulates that the useful work done in crushing and grinding is directly proportional to the new surface area produced and hence inversely proportional to the product diameter. In its second form it has been amplified and enlarged to include .the concept of surface energy; in this form it was precisely stated by A. M. Gaudin2 as follows: "The efficiency of a comminution operation is the ratio of the surface energy produced to the kinetic energy expended. According to the theory in its second form, measurements of the surface areas of the feed and product and determinations of the surface energy per unit of new surface area produced give the useful work accomplished. Computations using the best values of surface energy obtainable indicate that perhaps, 99 pct of the work input in crushing and grinding is wasted. However, no method of comminution has yet been devised which results in a reasonably high mechanical efficiency under this definition. Laboratory tests have been reported' that support the theory in its first form by indicating that the new surface produced in. different grinds is proportional to the work input. However, most of these tests employ an unnatural feed consisting either of screened particles of one sieve size or a scalped feed which has had the fines removed. In these cases the proportion of work" done on. the finer product particles is greatly increased and distorted beyond that to be expected with a normal feed containing the natural fines. Tests on pure crystallized quartz are likely to be misleading since it does not follow the regular breakage pattern of most materials but is relatively harder to grind at the finer sizes, as will be shown later. This theory appears to be indefensible mathematically, since work is the product of force multiplied by distance, and the distance factor (particle deformation before breakage) is ignored. The Kick theory' is based primarily upon the stress-strain diagram of cubes under compression, or the deformation factor. It states that the work required is proportional to the reduction in volume of the particles concerned. Where F represents the diameter of the feed particles and P is the diameter of the product particles, the reduction ratio Rr is F/P, and according to Kick the work input required for reduction to different sizes is proportional to log Rr/log 2.5 The Kick theory is mathematically more tenable than the Rittinger when cubes under compression are considered, but it obviously fails to assign a sufficient proportion of the total work in. reduction to the production of fine particles. According to the Rittinger theory as demonstrated by the theoretical breakage of cubes the new surface produced, and consequently the useful work input, is proportional to Rr-1.5 If a given reduction takes place in two or more stages, the overall reduction ratio is the product of the Rr values for each stage, and the sum of the work accomplished in all stages is proportional to the sum of each Rr-1 value multiplied by the relative surface area before each reduction stage. It appears that neither the Rittinger theory, which is concerned only with surface, nor the Kick theory, which is concerned only with volume, can be completely correct. Crushing and grinding are concerned both with surface and volume; the absorption of evenly applied stresses is proportional to the volume concerned, but breakage starts with a crack tip, usually on the surface, and the concentration of stresses on the surface motivates the formation of the crack tips. The evaluation of grinding results in terms of surface tons per kw-hr, based upon screen analysis, involves an assumption of the surface area of the subsieve product, which may cause important errors. The'evaluation in terms of kw-hr per net ton of 200 mesh produced often leads to erroneous results when grinds of appreciably different fineness are compared, since the amount of -200 mesh material produced varies with the size distribution characteristics of the feed. This paper is concerned primarily with the development, proof, and application of a new Third Theory, which should eliminate the objections to the two old theories and serve as a practical unifying principle for comminution in all size ranges. Both of the old theories have been remarkably barren of practical results when applied to actual crushing and grinding installations. The need for a new satisfactory theory is more acute than those not directly concerned, with crushing and grinding calculations can realize. In developing a new theory it is first necessary to re-examine critically the assumptions underlying

Jan 1, 1952

By P. N. Richards, M. K. Ormay

The present Paper extends the previous work on cold reduced, low carbon steels to preferred orientations developed after various heat treatments. In recrystal-lized rimmed steel, cube-on-comer orientations increased with cold reductions up to 80 pct. Above that {111}<112> and a partial fiber texture with (1,6,11) in the rolling direction dominated. During grain growth, cube-on-corner orientations have been observed to grow at the expense of {210}<00l>. In re-crystallized Si-Fe (111) (112) and cube-on-edge type orientations are dominant near the surface and the (1,6,11) texture near the midplane for reductions up to 60 pct. With larger reductions {111)}<112> and the (1,6,11) texture are dominant. In cross rolled capped steel a relationship of 30 deg rotation was observed between the (100)[011] of the rolling texture and the main orientations after re crystallization. Most orientations present in recrystallized specimens can be related to components of the rolling texture by one of the following rotations: a) 25 to 35 deg about a (110) b) 55 deg about a (110) C) 30 deg about a (Ill) THE orientation texture of recrystallized steel is of interest where the product is to be deep drawn, because preferred orientation is related to anisotropy of mechanical properties such as the plastic strain ratio (r value);1,2 and in electrical steel applications where a high concentration of [loo] directions in the plane of the sheet improves the magnetic properties of the material. It is interesting to note that both these aims are to a large extent achieved commercially, even though the orientation texture of cold rolled steel does not show large variation3 and the recrystallized orientations are generally given as being related to the as rolled orientations mostly by 25 to 35 deg rotations about common (110) directions.4-6 There is, as yet, no single completely accepted theory on recrystallization. The three mechanisms that have been investigated and discussed are: a) Oriented growth b) Oriented nucleation c) Oriented nucleation, selective growth Largely from the observations of the recrystalliza-tion process by means of the electron microscope,7-11 there is now considerable evidence that the "nucleus" of the recrystallized grain is produced by the coalescence of a few subgrains to form a larger composite subgrain, which finally grows by high angle boundary migration into the deformed matrix. From the intensive work on the recrystallization of rolled single crystals of iron, Fe-A1 and Fe-Si al-loys4-" he following observations have been made: 1) The change in orientation during primary recrys-tallization can usually be described as a rotation of 25 to 36 deg about one of the (110) directions. 2) The (110) axes of rotation often coincide with poles of active (110) slip planes. 3) If several orientations are present in the cold rolled structure, the (110) axis of rotation will preferably be a (110) direction that is common to two or more of the orientations. 4) With larger amounts of cold reduction (70 pct or more) departure from these observations became more frequent. 5) After larger cold reductions, rotations on re-crystallization about (111) and (100) directions have been observed. K. Detert12 infers that a rotation relationship of 55 deg about (110) directions is also possible, by stating that the recrystallized orientation {111}<112> can form from the orientation {100}<011> of cold reduced partial fiber texture A.3 The observation by Michalak and schoone13 that (lll)[l10] formed during recrys-tallization in fully killed steel containing (111)[112],— as well as (001)[ 110] which is related to the {111}<011> by a 55 deg rotation about <110>-implies a possible 30 deg rotation relationship about the common [Ill]. Heyer, McCabe, and Elias14 have recrystallized rimmed steel after various amounts of cold reduction, by a rapid and by a slow heating cycle and found that the preferred orientations strengthened with increased cold reduction. The most pronounced orientation up to about 70 pct cold reduction was found to be {1 11}< 110>, after 80 pct cold reduction both {111}<110> and {111}<112>, after 85 and 90 pct cold reduction, {111}<112>, and after 97.5 pct cold reduction it was {111}<112> and (100)(012). In the present work, the orientation textures of the recrystallized specimens are examined under various conditions of steel composition, amount and method of cold reduction, and method of recrystallization. The relationships between the preferred orientations of the as rolled and recrystallized specimens, and the conditions for the formation of the various orientations during recrystallization are investigated.

Jan 1, 1970

By Magnus Troilius

The method of using the bromine process of determining sulphur in steel, described below, is in successful use at the Midvale Steel Works. Ten grams of drillings are weighed out and put into the 1/2-liter flask A, with long neck. The flask is connected with a wide glass tube C&apos;, which, in its turn, is connected with the absorption bulbs B, containing HCI, 1.12 specific gravity, and ahout 5 C.C. of bromine. The wide tnbe C causes the vapor to condense and flow back into the flask A during boiling. The bulbs B connect with a long glass tnbe, which may be made to carry off the bromine fumes through a hole in a window, or, better still, through a flue with powerful draught. The connections being made, 100 C.C. of boiling water are run in through the thistle tube T. The air is thus completely driven out of the flask. 100 C.C. of HC1 (about 1.19 specific gravity) are then run in. When the gas begins to run rattler slowly through B, heat is applied until boiling gradually ensues. The steel being completely dissolved, the apparatus is disconnected, and the contents of B rinsed out into a beaker of 100 C.C. capacity, into which a few C.C. of a concentrated solution of BaCI, have been previously introduced. Heat is then applied (best by means of the hot iron plate) until the bromine is completely driven off and the BaSO, has settled nicely to the bottom. The BaSO4, is then filtered off on a small

Jan 1, 1884

By T. D. Murphy

This chapter deals with those types of silica raw materials that have been segregated and refined by natural processes into nearly monomineralic deposits and hence, by virtue of their high degree of purity, have become the sources of commodities having special and somewhat restricted commercial uses. In some instances, these raw materials occur in nature as unconsolidated quartzose sand or gravel and can be exploited and used with very little preparation and expense. More often, they occur as sandstone, conglomerate, quartzite, quartz mica schist, or massive igneous quartz which must be crushed, washed, screened, and sometimes chemically treated before commodities of suitable compositional and textural characteristics can be successfully prepared. The occurrence and distribution of silica raw materials is summarized and an effort has been made to bring commodity definitions, critical properties, and specifications up to date. Presentation of mining and processing methods is considered beyond the scope of this article; they are, for the most part, conventional and well known. New production techniques are currently reported in the trade journals and are later adequately described in technical publications as promptly as competitive restrictions allow. Discussion on Basis of Use ABRASIVE USES Industrial silica used for abrasive purposes falls into three main categories: (a) blasting sand; (b) glass-grinding sand; and (c) stone-sawing and rubbing sand. Blasting sand is a sound closely-sized quartz sand which, when propelled at high velocity by air, water, or controlled centrifugal force, is effective for such uses as cleaning metal castings, removing paint and rust, or renovating stone veneer. It is commonly referred to as Sand Blast sand. Multicycle quartz sand is an efficient blasting agent by merit of its survival characteristics which are soundness, toughness, and hardness. Steel grit and shot have supplanted it to a large extent but owing to their higher cost and tendency toward deterioration in storage, are still not universally used. It is conceded that angularity promotes faster cutting but this is offset by a higher loss in fines. The peening action of a rounded grain is a desirable feature in achieving a satin finish for certain light metal castings but a subangular grain is unsurpassed for fast heavy cutting. Specifications are chiefly based on size frequency distribution but it is mandatory that the grain be free of adhering clay or irony coatings. Material that dusts upon handling will not be tolerated. There is no uniform trade designation for the many blasting sand grades. Most producers sell on the basis of numbered grades; that is, No. 1, No. 2 and so on, this generally connoting fine to coarser grades. Designation of grade by the two sieve sizes between which most of the material lies, is practiced in some areas. Thus, in a No. 1220 grade, 98 pct of the material passes a 12 mesh sieve and is retained on a 20 mesh sieve. Blasting sand specifications vary according to use. Coarse grades range from 4 mesh to 12 mesh, medium grades range from 12 mesh to 30 mesh, finer grades may range from 20 mesh to 100 mesh or finer. Specifications generally call for narrow limits of gradation, requiring precise sizing methods. The fact that most blasting sands are retained

Jan 1, 1960

By Morris Cohen

WITHIN the past two years, a number of publications have called attention to the double peaks, or stages, that appear in the hardness and strength curves of certain aging alloys. The author has shown the existence of double hardness peaks during the aging of a high-purity silver-copper alloy;&apos; and on the basis of electrical resistance, microscopic, dilation and lattice-parameter measurements, he concluded that the initial hardness peak occurs prior to precipitation while the secondary hardening is due to precipitation. It was suggested that the general mechanism of age-hardening involves two consecutive processes, the first consisting of nucleus or knot&apos; formation, and the second consisting of actual precipitation and particle growth. It was further held that the two stages are interdependent, but because of nonuniform precipitation they may overlap each other to an extent that increases as the aging temperature is raised. At high aging temperatures, the effect of the first stage cannot be detected because of the rapid occurrence of precipitation. . The general theory of age-hardening recently presented by Dr. M. L. V. Gayler3 is in close agreement with the picture outlined above. With reference to work done on duralumin, copper-beryllium and copper-silver alloys, Dr. Gayler also concluded that age-hardening takes place in two consecutive steps: first, diffusion (in which the solute atoms migrate to certain crystallographic planes), and then precipitation. However, W. L. Fink and D. W. Smith4 have shown that the double aging peaks that appear in the strength curves of high-purity aluminum-copper alloys may be explained without recourse to pre-precipitation phenomena. By means of very careful metallographic technique, Fink and Smith demonstrated that during aging the precipitation takes place at an accelerated rate along the grain boundaries and slip planes as a result of the plastic deformation caused by the drastic quench from the solution heat-treatment temperature. † The general precipitation occurs at a

Jan 1, 1938

By Norman D. Fitz Gerald

The lack of a continuous operating balance in petroleum refining, which is analyzed in this paper, is by no means a feature solely of this division of the oil industry. Serious disequilibria of a capital as well as an operating nature exist both in the producing and marketing departments, while problems in the former and to some degree the latter are complicated by political involvements. Attention has previously been directed to the unstabilizing influence of present proration formulas in stimulating unnecessary drilling.&apos; While equilibrium in petroleum refining operations has been fairly well maintained in the past decade, examination of departures may prove fruitful. Economic analysis is the application of time and motion study to the functioning of management, rather than labor. Properly applied it may reveal changes in policies that would increase the utility of the properties and facilities of the industry for stockholders, employees and the public, while contributing a stabilizing influence to the general economy. The study of economic equilibrium is essentially one of measurement and interpretation, requiring adequate data and the development of a technique of analysis that employs statistical and mathematical methods as a supplement to the broad descriptive phase of economics. Economic equilibrium in petroleum refining is a dual concept. It embraces both the over-all balance between total storage and total demand for major products and the internal balance between the demands and inventories of the various products. The latter is the more complex of the two for it is concerned with proportionating the supplies of the several products stemming from the joint source to the demands for the individual products which are subject to wide variations. All the products are essentially nondurable goods, and they are used both by producers and consumers but in varying proportions. Motor fuel is very largely a consumer&apos;s good, while residual fuel oil is almost entirely a producer&apos;s good, the other products falling between these extremes. The peculiar-

Jan 1, 1939

By Norman D. Fitz Gerald

The lack of a continuous operating balance in petroleum refining, which is analyzed in this paper, is by no means a feature solely of this division of the oil industry. Serious disequilibria of a capital as well as an operating nature exist both in the producing and marketing departments, while problems in the former and to some degree the latter are complicated by political involvements. Attention has previously been directed to the unstabilizing influence of present proration formulas in stimulating unnecessary drilling.&apos; While equilibrium in petroleum refining operations has been fairly well maintained in the past decade, examination of departures may prove fruitful. Economic analysis is the application of time and motion study to the functioning of management, rather than labor. Properly applied it may reveal changes in policies that would increase the utility of the properties and facilities of the industry for stockholders, employees and the public, while contributing a stabilizing influence to the general economy. The study of economic equilibrium is essentially one of measurement and interpretation, requiring adequate data and the development of a technique of analysis that employs statistical and mathematical methods as a supplement to the broad descriptive phase of economics. Economic equilibrium in petroleum refining is a dual concept. It embraces both the over-all balance between total storage and total demand for major products and the internal balance between the demands and inventories of the various products. The latter is the more complex of the two for it is concerned with proportionating the supplies of the several products stemming from the joint source to the demands for the individual products which are subject to wide variations. All the products are essentially nondurable goods, and they are used both by producers and consumers but in varying proportions. Motor fuel is very largely a consumer&apos;s good, while residual fuel oil is almost entirely a producer&apos;s good, the other products falling between these extremes. The peculiar-

Jan 1, 1939

As one surveys the extensive taconite operations on the Mesabi Range, he may find it difficult to believe that only 15 years ago, the iron ore mining industry here was staring at its own imminent demise. Due to the high demands for iron ore during World War II the postwar period of 1946-1950, and the subsequent "police action" in Korea, there was rapid consumption of the Mesabi&apos;s already depleted ores, and some economists were giving the Range only 20-25 years of life. In the 13-year period 1941-1953, more than 850 million tons of iron ore were shipped to steel mills, an amount almost equal to the total production during the preceding 30 years. Proven ore reserves dropped from 1.1 billion tons in 1940 to 8.3 million tons in 1954, the largest decrease being recorded in the famed direct shipping ores.

Jan 9, 1968

By R. L. Wiegel

This article proposes a physical model for an idealized binary mineral system and for the process of liberation by size reduction. Based on this model, equations are derived relating the amount of each component liberated as a function of the ratio of the volumetric abundance of the two mineral components and the ratio of the mineral grain size to particle size. A definite relationship is shown to exist between the mineral concentration within a locked particle and the frequency of occurrence of such a particle. These relationships are used to obtain theoretical expressions for the concentration-recovery diagram. Physical mineral beneficiation processes are based on breaking a mineral aggregate to liberate the dissimilar mineral grains and then making use of their physical properties to separate the mixture into its components. The effectiveness of the process is therefore dependent on how well the minerals are liberated and how efficiently they are separated. Although a substantial amount of work is being done to improve our understanding of mineral separation processes, the study of mineral liberation itself has been almost completely neglected. The purpose of this theoretical study is to shed some light on the liberation phenomenon by: 1) proposing a physical model for an ideal binary mineral system, 2) treating mathematically the fracture of this system into liberated and locked particles, and 3) deriving an expression for the liberation characteristics of this system. The results of this study are useful in understanding the effect and importance of various parameters in liberation, and provide a basis for comparison with real mineral systems. &apos;RANDOM&apos; MODEL It is recognized that liberation can be caused by detachment which results from fractures occurring at the mineral grain boundaries, or by size reduction which restricts the occurrence of dissimilar mineral locking to a portion of the resulting particles. The detachment effect is dependent on the relative strengths of the mineral grains and the bonds between them, and must be treated empirically for each mineral system. The size reduction effect, however, can be treated analytically if certain assumptions are made concerning the shape and geometrical arrangement of the mineral grains.

Jan 1, 1968

By Nicholas J. Grant, John S. Benjamin, Bill C. Giessen

In the course of a study of hard particle-duc tile binder composite alloys, interest arose in the nature of the products of the reaction between the inter metallic compound NiAl and the binder niobium. No published information was then available. A program to

Jan 1, 1967

By L. J. Erck, T. E. Ban

A discussion of laboratory procedures used to determine pellet quality and to simulate handling and firing conditions. Strength-temperature relationships in pelletizing; effect of chemical additives on agglomeration; and crushing, abrasion, and impact resistance of the pelletized products are discussed with respect to five different iron ore concentrates. IN most routine experimental work on products and processes, method:; of operation and product evaluation are established from accurately controlled laboratory tests. With particular emphasis on the pelletization of fine iron ore concentrates, standardized procedures of laboratory production and product testing have been established at Cleveland-Cliffs Iron Co. Research Laboratory at Ishpeming, Mich. A program of this nature was used for investigating the agglomeration characteristics of various iron ore concentrates. The factors which control the process were studied and subsequently controlled for these investigations. Pelletizing as applied to iron ore agglomeration involves the preparation of spheroidal masses from a fine moist concentrate, followed by high-tempera-ture firing to produce a final product. The preparation of moist spherorids is generally designated as balling. This produces the so-called green pellets or balls. After, these have been fired they are called pellets. Balling is accomplished by rolling moist concentrates in a revolving drum until small spheroids form by a snow-balling action. These balls are then heated in a shaft furnace, or a modification of this device, to a temperature high enough to cause agglomeration within the individual balls while they descend countercurrent to hot oxidizing gases. By this process the lour strength balls are converted through various chemical and physical-chemical processes into hard pellets. With correct balling and firing, the pellets are strong, resist abrasive action and handling treatments, and provide a suitable blast furnace and open hearth feed. In 1950 Tigerschiold and Ilmoni developed a working hypothesis to explain the formation and stability of green pellets.&apos; Their work was presented on the basis of geologists&apos; discoveries concerning the soil-water system and C. V. Firth&apos;s early postulates of green pellet formation.&apos; Fundamental reactions oc-curing within fired pellets have been described by Cooke and Ban, who showed the microstructure changes caused by different firing temperatures." All these investigators have provided scientific clarifications of agglomeration by the pelletizing process and have opened avenues for greater development. Mineral grain growth and ceramic bond formation are the two basic phenomena imparting coherency to particles within a fired pellet of iron ore. Each of these is established by the transfer of thermal energy to the mineral particles. Grain growth mechanisms are chiefly physical reactions wherein smaller particles consolidate into larger ones, with resulting decrease in surface energy conforming with the second law of thermodynamics. Ceramic bond formation is a chemical reaction usually between basic and acid metallic oxides of the gangue and ore minerals. CaO, MgO, A1203, and FeO of Fe3O4, react in varying proportions with SiO, or Fe2O3, to form a great series of compounds or amorphous solid solutions. These product bond iron mineral particles together by a bridging action or by direct reaction with the surfaces of the particles. The result of the grain growth-ceramic bond formations is a consolidated, coherent compact of gangue and iron minerals formerly held together by much weaker bonds of interstitial water and forces common to dry, unconsolidated particles.4 With respect to iron ore agglomeration, these high temperature bonding reactions have been described by Schwartz, who referred to the bonds in sinters," and by Cooke and Ban, who referred to the bonds in fired pellets." The extent of the bonding phenomena and the consequent strength of fired pellets is governed by

Jan 1, 1954

In 1776 two Franciscan friars, Dominguez and Escalante, started to find a direct route from Santa Fé to Monterey, and in their misguided wanderings northward they reached Timpanogos, now known as Utah lake, where they heard of a much larger body of water to the northwest, of which they were told that it was extremely salt.* They never saw this great lake, because they passed south of it on their way to the Pacific coast. The Dead Sea of North America was discovered in 1835 by James Bridger, a trapper. He and other trappers had ascended the Missouri and had reached the Bear river. A discussion arose as to the course of this river, and a bet was made, to settle which Bridger followed the Bear river to its source, in the Uintah mountains, and from the crest of the watershed he caught sight of the lake, to which he then descended.† He tasted the briny water of the inland sea and wondered if it were an arm of the Pacific Ocean. The lake was first seen by the Mormons on July 24, 1847. A band of them, numbering 145 and led by Brigham Young, had migrated from Missouri in search of a new home in the western wilderness. It is recorded that when Brigham Young stood on the summit of the pass over the Wasatch range and saw the valley of the Jordan outspread before him, he exclaimed: "It is enough. This is the right place". He had seen it in a vision, so he claimed, and foresaw the future glory of the new Zion that was to be planted in that happy

Jan 1, 1932

By John A. Church

IT is a well-known fact that under similar conditions a ton of pig iron can be made from any ore with less fuel when charcoal is used than when coke or anthracite is employed for heating. The cause of this superiority is entirely undiscovered, and no explanation has yet been offered which has won even temporary acceptance. Such as they are the hypotheses heretofore presented are of two general kinds, and they come from those two divisions of the working force which are so often antagonistic in all professions, the scientific and the practical men. The theory of the scientific men is drawn from the chemical reactions which are known to go on in the furnace, and it is well expressed in a recent paper by Prof. Akerman, of the Stockholm (Sweden) School of Mines. It makes the superiority of charcoal as a fuel in the blast furnace to depend upon its quick and thorough reduction of carbonic acid. This property belongs to charcoal in virtue of its porous structure. Its cells have a diameter of only one twenty-four hundredth of an inch, and one grain of charcoal has been computed to have a surface of two and four-tenths square feet. According to the theory in question, carbonic acid is formed by the first impact of the air upon the fuel; but in charcoal furnaces the acid is immediately reduced to oxide by taking the necessary amount of carbon into combination, and the gas reaches its highest reducing power even in the near vicinity of the tuyeres. Coke, being harder, does not produce so strong a reducing gas in that part of. the furnace. Carbonic acid is formed as in the case of charcoal, and remains longer before its reduction to oxide is completed. Anthracite is the

Jan 1, 1879

By W. B. Mather

A SURVEY of the technical literature concerned with oil well drilling methods and particularly with rate of penetration by various cutting media on different types of rock provides a mass of conflicting data. This is especially true with respect to, (1) the relative efficiency of diamond, rotary and percussion drilling operations; (2) the costs of the various types of drilling; and (3) the hardness factor of various types of rock and cutting media. The latter is the particular phase of the subject discussed here. The cause of the confusion may be attributed partially to a lack of &apos;basic knowledge concerning the physical properties of the cutting media and of individual types of rock. It is also due in part to a general lack of uniform standards in the industry for evaluating the hardness versus drillability of rocks while possible errors in interpretation by the authors of the various papers pertaining to the subject may be an additional cause of misunderstanding. The hardness of a mineral is defined by Dana&apos; as "the resistance which a smooth surface offers to abrasion." Webster&apos; states that hardness is "the cohesion of the particles on the surface of a body (as a mineral) as determined by its capacity to scratch another or be itself scratched." Rock hardness, although not usually defined in publications describing rocks, is assumed to be the same as the minerals which compose the rock or the resistance of the rock to abrasion. Drillability of a rock may be defined arbitrarily as the rate at which rock is penetrated by a definite type of drilling tool with the assistance of a specific type of cutting surface or medium and under speci- fied conditions as to speed of rotation and applications of pressure. Eventually the term penetrability may have to be employed to include any method of making boreholes in rocks, since methods other than those using conventional cutting surfaces are already in operation. A case in point is the jet piercing methoda which employs an oxy-acetylene flame as a means of penetration. The word hardness as used by the drilling fraternity has a variety of meanings which depend upon the type of drilling method employed. For example, in diamond drilling, hardness is interpretated as resistance to abrasion. In percussion drilling the term implies resistance to impact or indentation, while in rotary drilling, hardness is considered anal-agous to compressive strength. The three types of hardness—abrasion, impact and compression—are conflicting variables for different types of rock. Nevertheless, the term hardness is applied indiscriminately by the industry for the resistance of rock to penetration by any type of drilling technique. Abrasion Hardness Since 1818, Moh&apos;s scale of hardness, although only relative in nature, has been accepted universally as the method of measuring mineral and therefore rock hardness. In 1933, Ridgway, Ballard and

Jan 1, 1952

By B. Yu, H. M. Lee, R. P. Gardner

Some preliminary results are given on the use of radioactive tracers for implementing the mechanistic approach to flotation. The process studied is an industrial one for the cleaning of sand for the production of glass. The radioactive tracers employed are those produced from intrinsic elements in the sand by neutron irradiation in a nuclear reactor. The results indicate that the technique will be useful for the determination of flotation simulation mechanistic model parameters on operating industrial processes without interruption of their normal operation.

Jan 1, 1980

By K. J. Richards, W. J. Schlitt

A combination of industrial and laboratory data is used to explain the interrelationships between operating parameters and cementation plant performance as measured by copper recovery and iron consumption. The chemical factors considered are the relative concentrations of copper and ferric ions in solution, acid concentration, the possible buffering action of other dissolved salts and solution temperature. The effects of flow conditions, solution oxidation, the presence of metallic copper and retention time are also considered. Based on the various relationships developed, possibilities for plant optimization are discussed.

Jan 1, 1974

By Henry Sturgis Drinker, Rossiter W. Raymond

Jan 1, 1914

Jan 1, 1961

By C. A. Heiland

The Eötvös torsion balance permits the measurement of certain second derivatives of the gravity-potential, which are known as the gradients of gravity and the curvature values for an equipotential plane of gravity. These quantities are influenced on level ground by the configuration of the masses underneath. Hence, the torsion balance has gained great importance for the location of geological structures and thus indirectly for the discovery of oil and other mineral deposits. If the ground is not level, however, the measurements become more difficult, because the superficial mass-irregularities also produce more or less considerable disturbances. It is necessary, therefore, to determine the shape of the surrounding topography by leveling as well as by consulting topographic maps and to compute its influence upon the torsion balance. The correction thus determined is called, in general, the topographic correction; it is composed of two constituents, the terrain correction and the cartographic correction. The terrain correction would be that part of the topographic correction as derived from the direct leveling of the area surrounding the station, whereas the data for the computation of the cartographic correction are obtained from a topographic map, usually beginning with a radius of LOO meters, as under most circumstances it is difficult to level along a arger concentric circle about the station. Principle of Topographic Correction The principle of all topographic corrections is to assume a homogene-ous compositon of the masses around the station in regard to specific gravity as well as a mathematical shape of the topography. The results become the more accurate the closer this mathematical shape is to the actual configuration of the terrain, but naturally the amount of necessary computation also increases. If a standard correction with fixed dis-ances is adopted, the middle error of this method will, therefore, increase as the irregularity of the terrain. Hence, the application of the torsion balance in mountainous areas may be successful only if the disturbances due to heavy masses underneath the surface are so large as to exceed onsiderably the increased middle error due to rugged topography, or,

Jan 1, 1929