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By E. Hoek

The stability of a rock structure depends primarily upon the extent to which fracture develops within the structure, The prediction of the extent of potential fracture, the first step in the study of fracture development, involves a knowledge of both the stress distribution in the structure and the criterion which governs rock fracture under various stress conditions. While a great deal of research effort has been devoted to the development of techniques for analyzing the stresses in mining and civil engineering structures1-3 and to the investigation of the fracture mechanism of rock 4-6 relatively little attention has been paid to the application of available knowledge to the solution of practical engineering problems. This paper describes a photoelastic technique for the determination of potential fracture zones in certain types of rock structures. A practical example, based upon a problem which might be encountered in designing the layout of deep-level mine excavations, is given as an illustration of the application of this technique. STRESS ANALYSIS AND ROCK FRACTURE In deciding upon the technique to be used for the solution of a problem involving the prediction of rock fracture it is necessary to consider: 1) What type of stress information is required to satisfy the fracture criterion for rock; anti 2) How this information can most conveniently be obtained. It has been established, both theoretically 4,7 and experimentally 5,6,8that the fracture of hard rock depends primarily upon the relationship between the algebraically greatest and the algebraically smallest of the

Jan 1, 1967

By John E. Conley, John A. Ruppert

LIGHTWEIGHT aggregates have been in use for many years in the United States but are now receiving more and more attention by manufacturers and users of concrete shapes. These shapes comprise building blocks, special forms, such as door sills, lintels, floor slabs, and beams. Lightweight aggregate also is adapted for monolithic construction. The increased building activity since termination of the war, together with the widespread shortage of cinders resulting from a general trend toward the use of oil and pulverized-coal fuels, has aggravated the situation. In some localities? new producers of lightweight aggregates have been stimulated to increased efforts to supply the demand. In addition, various estab- lishments of the United States Government have recently given attention to this problem. The National Bureau of Standards, in the Commerce Department, and the Bureau of Reclamation, in the Interior Department, have completed a series of tests on concretes made from some of the available commercial aggregates in order to evaluate their qualities. The tests have been made to focus attention on the desirable properties of good aggregates. This work was done at the request of the Technical Office of the National Housing Agency and Housing and Home Finance Agency. Some time previously, the former office had conducted a survey of the locations where lightweight aggregates are produced.' A study of this information discloses that the producing centers are widespread and that certain areas, notably the region east of the Mississippi River and especially the southeastern states in the sections along the Atlantic Coast, have only a limited number of such plants. The situation has been alleviated to some extent with new plants having been erected near Richmond, Va., and Lansford, Pa. Experiment Stations of the Federal Bureau of Mines at Tuscaloosa, Ala., Norris, Tenn., and College Park, Md., have investigated types and sources of potential raw materials such as clays, shales, and slates, as well as methods and procedures for utilizing these materials for their conversion into aggregates, and have published the data as a Bureau of Mines report.' Structural Uses of Lightweight Aggregates: Production of masonry blocks in the United States has averaged close to a billion units a year for the past three years, and of these it is estimated that more than 40 pct consisted of the lightweight type. It is anticipated that the future will witness an increase in this percentage in view of the superior insulating properties, decrease in dead weight, and ease of handling, transporting, and laying units of this type. Lightweight aggregates are used extensively in multistoried buildings in which the weight of the walls and floors is carried by a structural steel framework. The substitution of a lightweight concrete for normal concrete in a building of this type has brought about in many instances some or all of the following advantages:

Jan 1, 1951

By John A. Ruppert, John E. Conley

LIGHTWEIGHT aggregates have been in use for many years in the United States but are now receiving more and more attention by manufacturers and users of concrete shapes. These shapes comprise building blocks, special forms, such as door sills, lintels, floor slabs, and beams. Lightweight aggregate also is adapted for monolithic construction. The increased building activity since termination of the war, together with the widespread shortage of cinders resulting from a general trend toward the use of oil and pulverized-coal fuels, has aggravated the situation. In some localities? new producers of lightweight aggregates have been stimulated to increased efforts to supply the demand. In addition, various estab- lishments of the United States Government have recently given attention to this problem. The National Bureau of Standards, in the Commerce Department, and the Bureau of Reclamation, in the Interior Department, have completed a series of tests on concretes made from some of the available commercial aggregates in order to evaluate their qualities. The tests have been made to focus attention on the desirable properties of good aggregates. This work was done at the request of the Technical Office of the National Housing Agency and Housing and Home Finance Agency. Some time previously, the former office had conducted a survey of the locations where lightweight aggregates are produced.' A study of this information discloses that the producing centers are widespread and that certain areas, notably the region east of the Mississippi River and especially the southeastern states in the sections along the Atlantic Coast, have only a limited number of such plants. The situation has been alleviated to some extent with new plants having been erected near Richmond, Va., and Lansford, Pa. Experiment Stations of the Federal Bureau of Mines at Tuscaloosa, Ala., Norris, Tenn., and College Park, Md., have investigated types and sources of potential raw materials such as clays, shales, and slates, as well as methods and procedures for utilizing these materials for their conversion into aggregates, and have published the data as a Bureau of Mines report.' Structural Uses of Lightweight Aggregates: Production of masonry blocks in the United States has averaged close to a billion units a year for the past three years, and of these it is estimated that more than 40 pct consisted of the lightweight type. It is anticipated that the future will witness an increase in this percentage in view of the superior insulating properties, decrease in dead weight, and ease of handling, transporting, and laying units of this type. Lightweight aggregates are used extensively in multistoried buildings in which the weight of the walls and floors is carried by a structural steel framework. The substitution of a lightweight concrete for normal concrete in a building of this type has brought about in many instances some or all of the following advantages:

Jan 1, 1951

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 Philip R. Strand

Vermiculite is the name used for those micaceous minerals with a ferromagnesian aluminum silicate composition and the unique property of exfoliating to a low density material when heated. Commercially, the exfoliated products are also called vermiculite, or more exactly, expanded vermiculite. In its exfoliated state, vermiculite serves many markets, chief among them construction, agriculture, horticulture, and general industry. Composition and Properties Vermiculite, in a natural state, has the characteristic mica habit, splits readily into thin laminae, flexible but inelastic. In a mineralogical sense, vermiculite is a hydrated silicate with no exact chemical composition. The structural formula for a macroscopic, trioctahedral vermiculite may be written: [ ] The structure of vermiculite is basically that of a talc, and it could be regarded as a trioctahedral member of the smectite group. Macroscopically, vermiculite displays the prominent monoclinic crystal faces that are commonly marked by lines at 60° and 120°. Hardness varies from 1.5 to 2.8 or more; specific gravities are between 2.1 and 2.8; color is amber, bronze, brown, dark green, or black. When heated quickly to an elevated tempera¬ture, vermiculite expands by exfoliating at right angles to the cleavage, into wormlike pieces (the name vermiculite is derived from the Latin `vermiculare,' to breed worms). This characteristic of expansion, the basis for commercial use of the mineral, is the result of the mechanical separation of the layers by the rapid conversion of contained water to steam. The increase in bulk volume of commercial grades is 8 to 12 times, but individual flakes may expand as much as 30 times. All expansion occurs at right angles to the basal cleavage. Vermiculite may also be expanded by a number of chemical processes such as soaking in hydrogen peroxide, weak acids, and other electrolytes. There is a color change during expansion that is dependent upon the composition of the vermiculite and furnace atmospheres. Heating in an oxidizing atmosphere produces dull gray colors. The iron is generally not oxidized during chemical expansion. The exfoliation of the vermiculite crystal results in large pores being formed between groups of platelets. Thus exfoliation can make available a large increase in void volume without significantly changing the surface area of the platelets. This characteristic is important in the chemical carrier applications of vermiculite. Although there has been much research on the chemical and structural composition of vermiculite, an exact formula and composition cannot be described. This is to be expected since vermiculite derives from a number of different mineral sources. As has been proposed, vermiculite is not a single mineral species, but families of related minerals. Additionally, commercial interest in the end product has resulted in the name vermiculite being applied to the very voluminous, bloated products from calcination of baueritized (bleached) phlogopite. This has also resulted in many names for the specific vermiculite found in a particular deposit. All of this difficulty arises from the nature of its crystal chemistry. Consequently, vermiculite is now thought of as several related variable mineral series rather than a group of related species. The vermiculites have a common silica tetrahedral sheet structure with separating ions. It is now generally agreed that vermiculites must also be regarded as true clay minerals. The properties of the mineral, such as cation exchange capacity, organic complexing ability, and vari-

Jan 1, 1975

By E. G. Woodruff

(Butte Meeting, August, 1913.) FEW authors of treatises and papers on engineering subjects have . given adequate attention to topographic maps.. The statement applies especially to mining engineering in all branches. Even those who have discussed such maps have treated the subject only in a general way. Therefore it is proposed to outline in this paper a few of the uncommon, yet important relationships which topographic maps and their by-product, structure-contour maps, have to modern methods of mining investigation and development when the facts depicted on such maps are properly interpreted. Topography, as suggested by the etymology of the word, menus a detailed description of particular places. Written descriptions have been found less effective than the pictorial representations, therefore attempts have been made in various ways to picture the surface features of places. Lines and shading have been used, hachures drawn, and, finally, the contour topographic map. To a large extent this style of snap is the result of the demands of engineers. It is designed to meet their needs far more than those of the man untrained in engineering. In fact, the average man obtains a better idea of the topography of an area from the hachure system than from contour maps. . Since the maps. have been made chiefly for the use of the engineer, they ought to meet his demands on the one hand, and, on the other, should be used by him to the fullest extent. Such maps, when properly made, accurately portray a portion of the earth's surface and should present the topography better than a personal examination of the area without a map could present it, because the person making such examination views only a limited portion of the surface at a time, and estimates distances only roughly with his eye. Let the engineer consider carefully the fact that in many instances the topographic map is superior to a personal examination of the surface features of a property because the map is based on careful instrumental measurements, whereas the eye gives imperfect data because it can be used merely for the estimation and

Jan 6, 1913

By J. S. Aronofsky

The first step in a quantitative analysis ot the mechanism of oil displacement by water in a fractured reservoir is usually conceded to be the solution of the differential equation describing the saturation distribution of two immiscible fluids flowing in a porous medium, where the capillary pressure is taken into account. In such a system the production mechanism may consist of displacement of oil both by the flow of water due to natural or artificially imposed pressure gradients and by imbibition, which implies a flow of water not due to external pressure gradients. Owing to the presence of the two oil displacement mechanisms, the mathematical model given by the differential equation intended to describe the system may not properly represent the behavior of the physical system. In fact, in the reservoir the rate of water advance may be very slow, and in the case of a fractured reservoir with a great number of large fractures, the pressure difference determining the flow of water through the matrix may be much less than 1 lb/'psi over lengths of a few feet. In such a case, imbi-bition (the exchange between oil in the matrix and water in the fractures resulting from capillary forces) may become, with time. a significant element of the production mechanism. It occurred Lo the authors, however, that without going into a physical analysis of the process of production, it might be possible by means of simple abstract reasoning to throw some light on the variation of recovery with time under conditions occurring in a highly fractured oil reservoir with rising water table. The object of this paper is to present both the reasoning and its application to a reservoir of the highly fractured type. Specifically, the analysis given here was undertaken to try to explain the increase of recovery (as defined later) with time as observed in this reservoir, without having to assume unlikely variations in the reservoir parameters with depth. This attempt has been successful as will become clear upon comparison of the computed recoveries with the actual field data. ABSTRACT MODEL Let us consider a small volume. of porous matrix saturated with oil at time, t = 0. Let the process of oil displacement by water start at time, t = t,,. At some time, t, the process will have terminated. Then a volume of oil equal to or smaller than the original oil contained in the matrix will have been produced. The first basic assumption that describes the model and guides the forthcoming reasoning is that the oil production from the small volume. dv, is a continuous monotonic function of time and that it converges to a finite limit. Such an assumption is not inconsistent with the results of laboratory waterflood tests as well as with results of imbibition tests where this is, in fact, observed. The second basic assumption is that none of the properties which determine the rate of convergence change sufficiently during the process to affect this rate or the limit. Let it be assumed that the form of the function of time relative to production from the matrix volume. dv, is given by where V,(t) is the volume of oil produced up to that time t. R is the limit toward which the recovery converges, A is a constant giving the rate of convergence, and V,(t) is the volume of oil originally in place in the volume, dv. It should be noted that recovery at time I will be understood here to he It follows that r. tends to R as t tends to infinity. CONSTRUCTION OF RESERVOIR FROM ABSTRACT MODEL Let the reservoir consist of a series of identical blocks of porous matrix stacked vertically and separated by fractures. Let each of these blocks satisfy the conditions of our abstract model. These conditions are: (1) that recovery is a continuous mono-tonic function of time converging to finite limit, and (2) none of the properties that determine the rate of convergence change sufficiently to affect the rate or the limit. Let water be rising in fractures so that oil production from any part of the block starts when the water comes in conLact with it. TOTAL RECOVERY FROM THE RESERVOIR COMPARED TO RECOVERY FROM A SINGLE MODEL ELEMENT As stipulated in Eq. 1, in the case of the abstract model,

By R. I. Parsons, M. B. Standing, E. N. Lindblad

The recovery of the heavier components from a gas cap or retrograde pool is shown to be the greatest when the sand is cycled with a dry gas at a low pressure. This conclusion is in direct opposition to the belief that the most efficient production program is pressure maintenance and cycling at or near the dew point. The results are calculated from: (I) constant volume, variable composition pressure-volume-temperature tests on a mixture of trap gas and liquid from a producing well; (2) published equilibrium constant data and the measured composition of the dew-point material; and (3) the fact that in a sand section of homogeneous permeability, injected gas displaces reservoir gas nearly, quantitatively. The results are based on the simplifying assumption that variable permeability systems may be defined by the ratio of two statistical parameters, and that gas injected into an actual sand will behave as though the sand were composed of many layers, each of constant permeability. Introduction Pressure decline in gas-condensate type reservoirs is accompanied by the formation of a liquid phase throughout the reservoir. Over the past ten years the processing of the material from these types of reservoirs for the heavier hydrocarbon components and the return of the light fractions to the reservoir ("cycling") has become increasingly popular. It has often been stated that the purpose of such a program is to prevent the loss of the retrograde liquid phase formed in the reservoir. The purpose of this paper is to present the results of laboratory tests and computations concerned with several possible methods of producing a gas cap or condensate type of reservoir. The results show that the recovery of heavier hydrocarbons for this type of reservoir is not a maximum under conditions of cycling at or near the dew-point pressure. Instead, variations in permeability and the ability of the dry injected gas to revaporize condensate, point to cycling at a considerably reduced pressure as the optimum production-method. In addition the paper suggests a way of evaluating sands for their permeability variation. The calculations presented in the following sections of the paper are in terms of the production of the butanes and heavier fraction from the gas cap of a field which had an original pressure of approximately 3000 psi. Specifically, the calculations show: 1. To what extent the condensate formed in the reservoir after pressure decline can be recovered by the cycling of a dry absorber-plant gas through the sands. 2. Whether there would be greater recovery of hydrocarbons if cycling were instigated at the original reservoir pressure.

Jan 1, 1948

By M. B. Standing, R. I. Parsons, E. N. Lindblad

The recovery of the heavier components from a gas cap or retrograde pool is shown to be the greatest when the sand is cycled with a dry gas at a low pressure. This conclusion is in direct opposition to the belief that the most efficient production program is pressure maintenance and cycling at or near the dew point. The results are calculated from: (I) constant volume, variable composition pressure-volume-temperature tests on a mixture of trap gas and liquid from a producing well; (2) published equilibrium constant data and the measured composition of the dew-point material; and (3) the fact that in a sand section of homogeneous permeability, injected gas displaces reservoir gas nearly, quantitatively. The results are based on the simplifying assumption that variable permeability systems may be defined by the ratio of two statistical parameters, and that gas injected into an actual sand will behave as though the sand were composed of many layers, each of constant permeability. Introduction Pressure decline in gas-condensate type reservoirs is accompanied by the formation of a liquid phase throughout the reservoir. Over the past ten years the processing of the material from these types of reservoirs for the heavier hydrocarbon components and the return of the light fractions to the reservoir ("cycling") has become increasingly popular. It has often been stated that the purpose of such a program is to prevent the loss of the retrograde liquid phase formed in the reservoir. The purpose of this paper is to present the results of laboratory tests and computations concerned with several possible methods of producing a gas cap or condensate type of reservoir. The results show that the recovery of heavier hydrocarbons for this type of reservoir is not a maximum under conditions of cycling at or near the dew-point pressure. Instead, variations in permeability and the ability of the dry injected gas to revaporize condensate, point to cycling at a considerably reduced pressure as the optimum production-method. In addition the paper suggests a way of evaluating sands for their permeability variation. The calculations presented in the following sections of the paper are in terms of the production of the butanes and heavier fraction from the gas cap of a field which had an original pressure of approximately 3000 psi. Specifically, the calculations show: 1. To what extent the condensate formed in the reservoir after pressure decline can be recovered by the cycling of a dry absorber-plant gas through the sands. 2. Whether there would be greater recovery of hydrocarbons if cycling were instigated at the original reservoir pressure.

Jan 1, 1948

• One effect of the British devaluation of the Pound Sterling, with its resultant lowering of the pay limit, was the addition of considerable tonnages of previously marginal ore in gold mining. Crown Mines, Ltd., reported that 1,245,000 tons of such ore had been added to available reserves. But for devaluation, a steady decline in ore reserves had been a feature of operations during the previous ten years, and would have continued. •Loree Colliery of the Hudson Coal Co. is using a Humphrey spiral cleaning plant to meet requirements of the state in the matter of stream pollution. However, the process is producing a salable product. •Noranda is considering plans for constructing a commercial sized unit designed to produce elemental sulphuric acid and sintered iron oxide from pyrite. Test plant results have indicated the No. 5 ore zone can be treated by the new process economically. •A magnetic fluid clutch, and magnetic amplifiers for motor and generator control, have been developed under Navy contract by Vickers' Electric Division, in St. Louis, Mo. This constitutes the first commercial production of the clutch recently developed by the Bureau of Standards. •Fuel experts estimate coal production will run up to 500 million tons this year based on the expectation that business conditions will continue to be good. They also expect that in the future the use of coal will increase by 50 pct over today's level. These expectations are based on the fact that it provides the bulk of the heat, light, and power for making steel, for manufacturing, and for generating electricity as well as the development of the coal burning gas turbine and processes for making gas, gasoline, and oil from coal. •Entombed miners may benefit from a two-way communication system which utilizes the earth's strata as a network for electric signals. The use of FM radio waves makes this possible. The invention includes a portable transmitter-receiver unit kept near the face, and a more powerful portable equipment of the same sort above ground. In use, two probes on wires from the apparatus are driven into the earth. • The Union of South Africa has launched a uranium production project which government leaders think will help the West maintain world atomic supremacy. Experiments under way in the pilot plants are expected to lead to the establishment of a chain of processing factories along the Witwatersrand in which uranium will be reclaimed from gold tailing. •Recent developments in mechanized mining at the Bureau of Mines oil-shale mine near Rifle, Colo., have lowered mining costs to 29 cents per ton of shale. The cost of producing crude shale oil from 30-gal-per-ton-shale, using the new mining and processing techniques, would be about $1.50 per barrel. This is 500 lower than any previously stated price. • COMINCO is planning to open the old Bluebell lead-zinc mine near Nelson, B. C., on a 500-ton-per-day basis. The old workings will be pumped and a 970-ft incline sunk. A mill will be constructed at the property.

Jan 7, 1950

By A. M. Gaudin, J. G. Morrow

FLOTATION requires the existence of a definite contact angle. This contact angle, the surface tension of the solution, and adsorption at the solid-fluid interface are quantitatively related. Adsorption of dodecylammonium acetate on hematite was measured for a wide range of concentrations of reagent in solution. Similar measurements for quartz have already been made. Contact angle measurements were then made on polished surfaces of hematite and of quartz immersed in aqueous dodecylammonium acetate solutions, and a functional relationship was sought between adsorption density at the mineral-solution interface and the contact angle. Finally, the surface tension of the aqueous amine acetate solutions was measured. These data were combined to give an evaluation of the work of adhesion for the three-phase system. Specular hematite was crushed and then ground dry in a laboratory porcelain mill, with flint pebbles, to pass a 200-mesh screen. The ground product was sized in a Haultain infrasizer, and one of the granular sizes (cone No. 3) was used in all adsorption tests. A hand magnet was used to remove magnetite and abraded iron. Quartz was removed in a Frantz isodynamic magnetic separator. The purified hematite was leached in aqua regia, washed with distilled water until the washings appeared free of electrolyte by conductance measurement, dried in a low-temperature oven, and stored in a pyrex container. The specific surface of the closely sized hematite was determined by the krypton gas adsorption method.' Three measurements gave an average value of 1350 sq cm per g. Chemical analysis showed Fe -69.37 pct, insol = 0.72 pct. The quartz used in the flotation tests had been prepared by Chang" for an earlier investigation. Demineralized distilled water was used for all test solutions. Dissolved salt content was of the order of 0.03 ppm, expressed in terms of sodium chloride, as estimated from conductance measurements. Dodecylammonium acetate was obtained from Armour & CO. in two forms, the unmarked compound and a preparation marked by carbon 14 in the hydrocarbon chain of the aminium ion. Specific activity of the active salt was 0.134 millicurie per g. The important physico-chemical constants for the primary amine salt have been reviewed by de Bruyn. The calculated effect of hydrolysis of amine salt on pH of aqueous solutions and the effect of pH on the distribution ratio of the alkylammonium ion to free amine are of particular interest. All other chemicals used in this investigation were of analytical reagent grade. A column method' was used for adsorption work. Attainment of equilibrium distribution in the adsorption column depends on the solid-solution contact time, hence upon the volume of solution passed. It was assumed that contact time required for equilibrium would be a maximum for the lowest reagent concentrations. On this premise it was demonstrated experimentally that the passage of 500 ml of solution through the mineral bed was adequate. An aliquot (1 to 5 cc) of the solution to be analyzed was transferred to a small pyrex cup and allowed to evaporate to dryness at room temperature; 4 or 5 mg of unmarked amine acetate were added to the dried sample and the cup and its contents were transferred to the combustion system for analysis. Evaporation at room temperature must be emphasized, as even slightly elevated temperatures result in loss of reagent. A laboratory model G Beckman pH meter equipped with a glass electrode was used to measure pH of amine acetate solutions. The technique of internal gas counting of radioactive carbon dioxide in a Geiger-Muller counter was used. Developed originally by Brown and Miller,- his method was adapted to the analysis of carbon-14 marked flotation reagents by Chang, de Bruyn, and Bloecher. nalytica1 method and procedures have been described in detail by Bloecher.' Contact angles were measured by the captive-bubble technique." The mineral specimens were carefully selected to avoid cracks and inclusions of other minerals. All specimens were mounted in plastic and polished to produce a smooth surface. The final polishing and contact-angle measuring

Jan 1, 1955

By C. E. Sims

The carbon-oxygen reaction without doubt is the basic reaction in steelmaking. It is important on several counts: In the first place, carbon is the element that distinguishes steel from iron. It is the principal element controlling properties, and its control is of prime concern. Although the principal objective of the carbon-oxygen reaction is to oxidize excess carbon, the accompanying boil should not be underrated. The mechanical agitation, stirring, and mixing resulting from the boil are so useful in the distribution of heat and in promoting uniformity of composition in the bath that, were it not a natural accompaniment of the carbon-oxygen reaction, it is probable that something would have to be invented to replace it. The open-hearth operation, for example, with the bath heated from above by radiation, would be impracticable without the carbon boil. The electric-arc furnace is somewhat less dependent on it, but every melter knows how much easier it is to gain temperature with minimum damage to refractories during the boil than with a dead bath The motor action of the induced current of the induction furnace makes the carbon boil unnecessary but even there a severe oxidation has been found useful in giving greater freedom from porosity in certain steels. The quantitative aspects of the carbon-oxygen reaction have been given considerable attention by a large number of investigators, and the principles of physical chemistry have played an important part in these studies. Physical chemistry is the science of the mechanics and mathematics of chemical reactions. It is possible to study the mechanisms of reactions in a qualitative manner writhout reference to mathematics and thus obtain valuable concepts as to the manner in which the wheels go around. When it is desired to express quantitative relations in these reactions, however, resort to mathematics is not only convenient but necessary. Mathematics may also be regarded as the shorthand language of physical chemistry. A basic relation whose description requires numerous words may be expressed very simply by a mathematical formula or equation. A good example of this is the equilibrium constant for a chemical reaction. Expressed verbally, it is: When a chemical reaction has reached a condition of equilibrium, the Product of the concentration of the reacting substances on one side of the equation, divided by the product of the concentration of the reacting substances on the other side, gives a quotient that is a constant at constant temperature For the carbon-oxygen reaction C + O ^ CO this is expressed simply as % C X % O -%co where K (from the German Konstant) is the equilibrium constant for the reaction. Although mathematics is such a necessary and useful tool, it is also a potential pitfall. Mathematics in itself is an abstract science, which is not inhibited by consideration of mechanisms or materials.

Jan 1, 1948

By C. E. Sims

The carbon-oxygen reaction without doubt is the basic reaction in steelmaking. It is important on several counts: In the first place, carbon is the element that distinguishes steel from iron. It is the principal element controlling properties, and its control is of prime concern. Although the principal objective of the carbon-oxygen reaction is to oxidize excess carbon, the accompanying boil should not be underrated. The mechanical agitation, stirring, and mixing resulting from the boil are so useful in the distribution of heat and in promoting uniformity of composition in the bath that, were it not a natural accompaniment of the carbon-oxygen reaction, it is probable that something would have to be invented to replace it. The open-hearth operation, for example, with the bath heated from above by radiation, would be impracticable without the carbon boil. The electric-arc furnace is somewhat less dependent on it, but every melter knows how much easier it is to gain temperature with minimum damage to refractories during the boil than with a dead bath The motor action of the induced current of the induction furnace makes the carbon boil unnecessary but even there a severe oxidation has been found useful in giving greater freedom from porosity in certain steels. The quantitative aspects of the carbon-oxygen reaction have been given considerable attention by a large number of investigators, and the principles of physical chemistry have played an important part in these studies. Physical chemistry is the science of the mechanics and mathematics of chemical reactions. It is possible to study the mechanisms of reactions in a qualitative manner writhout reference to mathematics and thus obtain valuable concepts as to the manner in which the wheels go around. When it is desired to express quantitative relations in these reactions, however, resort to mathematics is not only convenient but necessary. Mathematics may also be regarded as the shorthand language of physical chemistry. A basic relation whose description requires numerous words may be expressed very simply by a mathematical formula or equation. A good example of this is the equilibrium constant for a chemical reaction. Expressed verbally, it is: When a chemical reaction has reached a condition of equilibrium, the Product of the concentration of the reacting substances on one side of the equation, divided by the product of the concentration of the reacting substances on the other side, gives a quotient that is a constant at constant temperature For the carbon-oxygen reaction C + O ^ CO this is expressed simply as % C X % O -%co where K (from the German Konstant) is the equilibrium constant for the reaction. Although mathematics is such a necessary and useful tool, it is also a potential pitfall. Mathematics in itself is an abstract science, which is not inhibited by consideration of mechanisms or materials.

Jan 1, 1948

Secondary blast holes are now being pierced in quartzite and sandstone quarries, using multiple hand-operated Jet-Piercing units supplied with oxygen, fuel and water from a compact mobile carrier. A unit of this type, operating in a Canadian quarry, enabled four Jet-Piercing blowpipes to pierce blast holes for two hours without shutdown. The piercing blowpipes used were developed by Linde Air Products Co., a division of Union Carbide and Carbon Corp. The mobile supply carrier was constructed by the quarry from specifications supplied by Linde and modified by the quarry operators for their particular use. Employment of the new self-contained unit, which allows up to four operators to pierce approximately 450 ft of blast hole without shutdown, accelerates rock removal operations. Normally, only two blowpipes are in operation at one time. Large boulders or ledges, which sometimes remain after primary blasting to hamper loading operations, can, in the case of certain hard rock, be prepared for reduction more rapidly with these new units than by any other means. A special feature of the new manual Jet-Piercing unit is the mobile gas and fluid supply carrier. It consists of a standard truck chassis fitted out with four banks of large standard-capacity oxygen cylinders, a steel-holding tank for fuel oil, and a gasoline-driven air compressor and tank for pressurizing the fuel oil tank. Cooling water for the blowpipes is supplied to the unit from a hose extension to the quarry supply line. Feeder lines from the oxygen cylinder manifolds and the oil and water tanks terminate in four sets of take-off stations on the control panel at the rear of the truck. As many as four hand Jet-Piercing blowpipes can be connected to the take-off panel by high-pressure rubber hoses. The hand Jet-Piercing blowpipe used with the mobile supply carrier is a highly portable device which can be manipulated comfortably by one operator. The blowpipe can pierce blast holes at rates up to 60 ft per hour, depending on the properties of the rock. Blast holes can be pierced at any angle from the vertical to the horizontal, making it necessary for the operator to drill from the top of the boulder. Hole diameter is held to approximately that which allows the use of a standard 11/8-in. diameter dynamite. The manual Jet-Piercing blowpipe has these important design features: a burner from which the combustion gases emerge at supersonic speeds (in excess of 6000 ft per sec); a hole-sizing shell which controls the minimum size of the hole and protects the copper burner; and a sliding shield which protects the operator against the steam and spallings ejected from the hole during the piercing. The Jet piercing process has been applied successfully in United States and Canadian quarries within the last several years as an advanced method of "drilling" blast holes.

Jan 1, 1952

Attention! Engineers! Geologists! Here is your Opportunity to be of Professional Service The war has interrupted the supply of many minerals, which were normally imported. In view of present transportation conditions, a serious shortage exists in certain materials and will soon develop in others. Some immediate action is imperative. The first thing is to take a careful inventory of American resources. We must know where the ore deposits are, what has hitherto hindered their utilization, what methods must be used, and what equipment will be needed if an emergency demands their rapid development. Many properties must be re-examined from a new point of view, that of present necessity rather than of normal profit. When the shortage is realized, the preliminary steps for relief should have been completed. It is a necessary and patriotic form of mineral insurance. Will you have a part in it? Do not forget that these are war times, and that what may have been valueless a year ago may be a "life-saver" now; an abandoned copper prospect of 1913 might make a successful pyrite mine in 1917. We are fighting an autocratic enemy who knows his resources to the last pound, and uses them with most efficient organization. We have no Kaiser, so each of us must do his share to put our Government in the same situation. The Government needs your facts.

Jan 8, 1917

By V. H. Wilhelm

During the first half of the year 1935, the oil industry in California was on a fairly profitable basis, owing mainly to the operation of the Petroleum Marketing Agency. Coincident with the discontinuance of enforced curtailment, California production surged upward from an average of about 500,000 bbl. per day (over the first five-month period) to approximately 625,000 bbl. per day (over the last seven-month period). On Dec. 9 the state production had reached a peak of over 700,000 bbl., a figure that had not been approximated since the early days of voluntary curtailment (Fig. 1). A price cut was instituted during the last half of August, but had no deterring effect on operators that were determined to take advantage of the breakdown of curtailment and produce to capacity. New reserve figures, compiled from actual potentials, available after cessation of curtailment, revealed the startling fact that California reserves were rapidly declining. This situation, coupled with the desire among operators to obtain a more equitable price for their dwindling reserves, caused a restoration in November of a portion of the August price slash. A further rise in price was effected in early December, and crude quotations at the end of the year closely approximated those in effect during the first right months. At the close of the year, the industry felt confident that the production situation was under control. In all fields where competition is keen because of close spacing, production is gradually declining. In the Los Angeles Basin especially there is no likelihood of a large amount of overproduction, unless a new pool is discovered or deeper drilling reveals a prolific source of crude. As long as the fields that are operated by a few companies, such as Kettleman Hills, North Belridge, Ventura Avenue, West Coyote, Dominguez, and some others, can be controlled, it is believed that the overproduction problem in California will be solved.

Jan 1, 1936

By V. H. Wilhelm

During the first half of the year 1935, the oil industry in California was on a fairly profitable basis, owing mainly to the operation of the Petroleum Marketing Agency. Coincident with the discontinuance of enforced curtailment, California production surged upward from an average of about 500,000 bbl. per day (over the first five-month period) to approximately 625,000 bbl. per day (over the last seven-month period). On Dec. 9 the state production had reached a peak of over 700,000 bbl., a figure that had not been approximated since the early days of voluntary curtailment (Fig. 1). A price cut was instituted during the last half of August, but had no deterring effect on operators that were determined to take advantage of the breakdown of curtailment and produce to capacity. New reserve figures, compiled from actual potentials, available after cessation of curtailment, revealed the startling fact that California reserves were rapidly declining. This situation, coupled with the desire among operators to obtain a more equitable price for their dwindling reserves, caused a restoration in November of a portion of the August price slash. A further rise in price was effected in early December, and crude quotations at the end of the year closely approximated those in effect during the first right months. At the close of the year, the industry felt confident that the production situation was under control. In all fields where competition is keen because of close spacing, production is gradually declining. In the Los Angeles Basin especially there is no likelihood of a large amount of overproduction, unless a new pool is discovered or deeper drilling reveals a prolific source of crude. As long as the fields that are operated by a few companies, such as Kettleman Hills, North Belridge, Ventura Avenue, West Coyote, Dominguez, and some others, can be controlled, it is believed that the overproduction problem in California will be solved.

Jan 1, 1936

By M. E. Volin, D. W. Fuerstenau, A. L. Mular

This paper presents the results of an investigation of the effect of feed size on the integral rate at which feed material is dry ground in a laboratory rod mill. The data are interpreted in terms of the Gaudin-Meloy distribution equation. The equation, Mo — Mt/t = Aoxo r-1, is found to hold for feed sizes smaller than some critical size or for grinding times larger than some critical time. It is shown that a feed grindability is related to this critical size, which appears to be the transition between predominately impact and predominately attrition grinding. Detailed research on feed size effects in comminution has been rather limited. Gaudin1 ground single-sieve fractions of quartz for extended time periods (four hours) in a laboratory ball mill. His work, which was designed to study the nature of size distributions, showed that there is a critical feed size above which comminution occurs primarily by attrition. For his system, the critical size was about 2-mm when using 22-mm balls. In a more recent investigation2 single-sieve fractions of quartz were ground in a laboratory rod mill for constant time periods (15 min) to determine how feed size affects the grindability of the material. This work showed that grindability is essentially independent of feed size in the rod mill after this moderately long grinding period. To further clarify this observation, a study in which feed size and grinding times are varied over a fairly wide range, and particularly, a study of the dependence of the integral rate of grinding on feed size during the initial stages of rod milling is necessary. For an analysis of such data, it is desirable to use a parameter which is very sensitive to change during the initial grinding period when reduction ratios are

Jan 1, 1964

By Lewis A. Delano, Harold Rabling

It has been generally recognized that, owing to the extreme friability of galena, fine grinding has a tendency to cause excessive sliming of the mineral, so operators of lead mills have attempted to avoid this condition by commencing concentration at as coarse sizes as any mineral is freed. Jigging has been the basis of the milling process, making a clean coarse concentrate and a large amount of tailing, which was considered sufficiently low-grade to be rejected. However, developments and improvements in concentration processes are everywhere changing the low-grade tailing of yesterday into material worth re-treating today. Investigations of the work of the Hancock jig on the Bonne Terre ore have shown that the best results to be expected will give a tailing assaying 0.75 per cent. lead; the average for all conditions and grades of ore will be between 0.80 and 0.90 per cent. By crushing the jig tailings in ball-mills and retreating by tables and flotation, a tailing of considerably lower grade can be made; the problem then becomes an economic one of increased crushing costs versus higher recovery. In considering the entire elimination of jigging, the increascd smelting charges due to a greater amount of slime galena will be counterbalanced by the lower operating cost, increased recovery, and the many advantages of a simpler flow sheet. In developing these problems in the Bonne Terre mill of the St. Joseph Lead Co., a long series of tests has been carried out covering every stage of crushing and concentration, and a large number of possible flow sheets were considered and tried. Only the final results and a few comparisons will be given here. At the same time, a careful and detailed cost-keeping system has enabled us to compare milling costs with the various Bow sheets, and to calculate the economics of the problem with great accuracy. Concentration Problem The ore occurs as widely scattered deposits of galena disseminated through limestone; it has a specific gravity of 2.8 and the following composition: Pb, 4.00 per cent.; Fe, 3.00 per cent.; Zn, 0.32 per cent.; S, 3.10 per cent.; MnO2, 0.73 per cent.; SiO2, 4.20 per cent.; Al2O3, 3.20 per cent ; CaO, 28.60 per cent.; MgO, 16.85 per cent.; CO2, 36.00 per

Jan 1, 1922

By James A. Crookston, William D. Fitzpatrick

Committee C-8 of the American Society for Testing and Materials defines "Refractories" as "Material, usually nonmetallic, used to withstand high temperature," and it defines the term "Refractoriness" thus, "In refractories the capability of maintaining the desired degree of chemical and physical identity at high temperatures and in the environment and conditions of use." The ability to withstand high temperatures is critical to classifying a material as a "refractory." However, as the foregoing definition of "refractoriness" implies, the refractory material may be subjected to and is expected to resist not only high temperatures but a variety of other destructive forces incident to its use. These include abrasion, impact, thermal shock, chemical attack, and high level loads at high temperatures. The various industrial applications of refractories represent an infinite variety of combinations and degrees of severity of these destructive forces, including high temperatures. Naturally, such a variety of application conditions leads to a need for a wide variety of refractory products to satisfy those conditions. The number of refractory products available is great enough that some form of classification is necessary to a discussion of refractories. Refractories may be classified in several ways, but the most suitable one is based on their general compositions and to lesser degrees on their physical condition and distinctive properties. The primary types of brick include aluminosilicate brick (fire clay and alumina), basic brick (magnesia and chrome ore, alone and in various combinations), silica brick, insulating brick, and special refractories (carbon, Sic, ZrO,, zircon, borides, and nitrides). Brick are, of course, preformed and are usually heat treated at high temperatures before use, but are in some instances unburned and/or chemically bonded, including the relatively new class of tar-bonded magnesia and/or dolomite brick. In addition to preformed refractories, another broad category includes the so-called specialty refractories, which are usually made in the same types as itemized for brick-bonding mortars and high temperature cements, hydraulic setting castables or refractory concrete, plastic firebrick, and ramming mixes. Refractory grains, such as fire clay and high alumina calcines, dead-burned magnesite and periclase, and dead-burned dolomite are also considered refractory products. Brick are also classified on the basis of physical dimensions, as standard sizes and special shapes. The standard sizes are those which are of definite shape and design and are designated as 9 x 4 ½ x 2 ½ in. and 9 x 4 ½ x 3 in. straights and series. All other brick of non- standard sizes are referred to as special shapes. These come about as a result of a particular need for a given furnace or for a particular application.

Jan 1, 1975