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By Paul K. Krueger

SUMMARY Since 1970 the Federal Preparedness Agency has been using computer models to help establish the amounts of strategic and critical materials to be held in the National Stockpile. Fifty-three of these materials are metals or minerals. The following diagram shows the linkage of models used to estimate material requirements. [ ] The starting point for the models are estimates of the major components of GNP for some future period. These may be estimates purchased from a forecasting service or may be produced in-house. The projections are translated into industrial final demands using DITT (Demand Impact Transformation Tables), a system developed at FPA. Then using a version of the current Bureau of Economic Analysis input-output model, estimates are made of the gross output of each industry necessary to support the level and composition of GNP as specified by the macro-economic model.

Jan 1, 1977

By R. M. Board

This paper will focus on measurement and control of four main aspects of crushing, namely horsepower, bowl level, mantle position and feed rate, and will discuss related sensors and control techniques, some of them designed specifically for crusher control, that have proven successful and reliable in many installations.

Jan 1, 1982

PROF RICHARD ÅKERMAN Stockholm, Sweden DR. FRANK DAWSON ADAMS Montreal, Canada PROF RICHARD BECK Friberg, Germany ANDREW CARNEGIR New York, N.Y. DR. JAMES DOUGLAS New York, N.Y. PROF HATON DE LA GOUPILLIERE Paris, France SIR ROBERT A. HADFEILD London, England PROF HANS HOFFER Leoben, Austria PROF HENRI LOUIS LE CHATELIER Paris France EZEQUIEL ORDONEZ Mexico City, Mexico ALEXANDRE POURCEL Paris, France DR. ROSSITTER W. RAYMOND New York, N.Y. DR. ING H. C. EMIL SCHROEDTER Dusseldorf, Germany JOHN E. STEAD Middlesborugh, England JAMES M. SWANK (Associate) Philadelphia, Pa. PROF DIMITRY CONSTANTIN TSCHERNOFF St Petersburg, Russia PROF TSUNASHIRO WADA Tokyo, Japan CHARLES D WALCOT Washingtion D.C.

Jan 1, 1917

By E. H. Rose

The present symposium on flotation machines provides a unique opportunity for group reappraisal of standard or habitual viewpoints. A symposium is by definition a trading post- for observations that might prove complementary when put together, thus leading to useful thoughts that might not have been evident from the original observations individually. The present paper, pertaining to power consumption in flotation, is deliberately an experiment of that kind. Data were solicited from the operating superintendents of several of the major flotation plants on this continent. The information received, covering a total of 14 separate operations in seven plants, has been collated in terms of power intensity; that is, the total power input per cubic foot of cell volume. This departs somewhat from the conventional expression of power per ton of ore treated, though the latter figure is also given for the plants concerned. Because of wartime restrictions, particularly in Canada, identifying names of plants and machines are withheld. Not as a firm conclusion, but as a tender for symposium discussion, the following points are made: 1. That flotation is a power operation in much the same sense as ball milling. 2. That contact time is the complement of power intensity and may be decreased as the latter is increased. 3. That a decrease in flotation power per ton of ore can result from an increase in power intensity. Analogy with Grinding In grinding, it has become axiomatic that the more the power put into a given operation, the greater the work performance. The analogous view is now proposed that the effectiveness of any flotation operation will be related to the mechanical energy usefully applied to that operation. Under this view, each increment of properly directed input energy should give either an increase in unit tonnage or an improvement in the metallurgical separation (concentrate grade or tailing grade), until either the theoretical limit imposed by mineral constitution or surface condition is reached, or until further increments of power become uneconomic under the law of diminishing returns. Thus, as in grinding, there are two forms of output that greater power input or improved utilization of power can produce. As for the law of diminishing returns, lower unit cost of power through improved generating efficiency in the past decade has pushed the limit back. Over and above this, however, there is strong indication in the operationg data herein presented that higher power intensity results in an actual economy of over-all power consumption. Like crushing and grinding, flotation accomplishes a rupture of the forces of molecular attraction, by taking particles from the common environment and placing them in the two separate environments of

Jan 1, 1947

By E. H. Rose

The present symposium on flotation machines provides a unique opportunity for group reappraisal of standard or habitual viewpoints. A symposium is by definition a trading post- for observations that might prove complementary when put together, thus leading to useful thoughts that might not have been evident from the original observations individually. The present paper, pertaining to power consumption in flotation, is deliberately an experiment of that kind. Data were solicited from the operating superintendents of several of the major flotation plants on this continent. The information received, covering a total of 14 separate operations in seven plants, has been collated in terms of power intensity; that is, the total power input per cubic foot of cell volume. This departs somewhat from the conventional expression of power per ton of ore treated, though the latter figure is also given for the plants concerned. Because of wartime restrictions, particularly in Canada, identifying names of plants and machines are withheld. Not as a firm conclusion, but as a tender for symposium discussion, the following points are made: 1. That flotation is a power operation in much the same sense as ball milling. 2. That contact time is the complement of power intensity and may be decreased as the latter is increased. 3. That a decrease in flotation power per ton of ore can result from an increase in power intensity. Analogy with Grinding In grinding, it has become axiomatic that the more the power put into a given operation, the greater the work performance. The analogous view is now proposed that the effectiveness of any flotation operation will be related to the mechanical energy usefully applied to that operation. Under this view, each increment of properly directed input energy should give either an increase in unit tonnage or an improvement in the metallurgical separation (concentrate grade or tailing grade), until either the theoretical limit imposed by mineral constitution or surface condition is reached, or until further increments of power become uneconomic under the law of diminishing returns. Thus, as in grinding, there are two forms of output that greater power input or improved utilization of power can produce. As for the law of diminishing returns, lower unit cost of power through improved generating efficiency in the past decade has pushed the limit back. Over and above this, however, there is strong indication in the operationg data herein presented that higher power intensity results in an actual economy of over-all power consumption. Like crushing and grinding, flotation accomplishes a rupture of the forces of molecular attraction, by taking particles from the common environment and placing them in the two separate environments of

Jan 1, 1947

By R. P. Killmeyer, B. S. Gottfried, J. T. Wizzard

The US Department of Energy's Coal Preparation Branch has developed a computer program to calculate the performance characteristics of coal washing devices. This program uses specific gravity analyses of the clean coal and refuse streams as input, and generates dependent and independent performance criteria for the washer. Partition curves are internally represented in a functional form by a Weibull function. Comparisons are made between performance criteria calculated by hand and the performance criteria calculated by the program for 120 different dense medium cyclone tests. Results show that the computer program gives results in close agreement with hand-calculated values while greatly reducing the amount of time involved in performing the analyses.

Jan 1, 1984

By C. H. G. Bushell, James E. Lawver, William Barbarowicz

Proper use of automatic controls in the process industries is a combination of art and science. Although many phases of automatic control theory can be expressed by precise mathematical relationships, the final control arrangement usually requires considerable effort by trial and error before the optimum control circuit is found. The failure of flotation operators to recognize that control circuits require study and plant experimentation before satisfactory operation occurs has led to a popular misconception that flotation plants simply do not lend themselves to automation. This widespread belief has been overcome to some degree in recent years by the numerous installations of automatic controls that have paid their way by increasing profits in terms of increased recoveries, lowered costs, or higher grade concentrates. WHY CONTROL ? Any form of automation must be justified in terms of ultimate return on in- vestment by improving quality, by increasing plant throughput, or by reducing the total operating costs. Generally speaking, automatic controls rarely re- place a mill operator. They assist the operator in holding important variables within predetermined limits. Large tonnage operations usually can justify a great deal of automation because an increase in one or two units of recovery results in enormous savings compared to the capital and operating costs of controls. DETERMINATION OF CONTROL The first questions in considering plant automation are: 1) What variables must be controlled? 2) What are the optimum levels of the variables? The optimum operating conditions for any process are those which maximize profits. Many of the variables active in flotation processing can be determined by experimentation in the laboratory or pilot plant 10. Although laboratory experiments can pinpoint variables, the true optimum conditions existing at plant level usually must be determined by plant scale experiments. In recent years, the concepts of detailed experimental designs in the laboratory, followed by plant experiments, have reached the stage of maturity where

Jan 1, 1962

By Arthur Gray

THE thermal analysis of a metal or alloy is ordinarily made with the aid of heating and cooling curves, in which transitions are indicated by the rapid changes in curvature that accompany .changes in the rate of heat absorption or evolution. Analysis by the method that depends on the change in thermal expansivity is not customary, partly, at least, because of the difficulties involved in making the necessary measurements. However, under certain circumstances, the dilatometric method of analysis may possess advantages over the thermometric method that will justify the additional trouble required. The addition of 1 per cent. of zinc to an alloy has been found to produce, upon the volume changes that take place during transition, effects that suggest the possibility of using the dilatometric method of thermal analysis as a rather sensitive means of obtaining chemical information. Although the illustrations presented in this paper are drawn from data obtained during an investigation of dental amalgams, similar phenomena can doubtless be observed with other alloys. Some of the results found during an investigation made in 19171 have been confirmed by data on the thermal expansivity of amalgams published by Souder and Peters of the Bureau of Standards in reporting tests of dental materials.2 Although the Bureau of. Standards made experiments for the purpose of discovering effects of including zinc as one of the constituents of a dental alloy-a matter much discussed in dental literature but without the presentation of reliable experimental evidence to support the views of ;either side-the reports of the test made by the Bureau give the impression that certain striking phenomena associated with the presence of zinc were not noticed. Among such phenomena are those connected with the conditions that determine whether or not a specimen of amalgam becomes covered with droplets from which crystals develop.

Jan 9, 1920

By Dennis V. D’Andrea, Robert C. Steckley, William C. Larson, Richard A. Dick

A fragmentation experiment was performed in cooperation with Duval Corporation in a porphyry copper molybdenum deposit near the Sierrita pit south of Tucson, Ariz. A 10-hole test blast was detonated to establish relationships between blasthole spacing and the resulting fragmentation. Blastholes were 9 in. in diameter and 110 ft deep. The 10 blastholes contained a total of 17,400 lb of aluminized slurry blasting agent in 50-ft columns with 60 ft of stemming. Blasthole spacings of 25, 20, and 15 ft were tested. Diamond drill core examination was the primary method used to determine the condition of the rock before and after blasting. Topographic surveys were used to measure the rock swell produced by the blast and a fragment size distribution was obtained for the rubblized material on the surface. The rubble zone at the surface was ideal for in situ leaching. Fragmentation to depths of 110 ft was excellent from the 15- to 20-ft blasthole spacing patterns. Good breakage was also produced by the 25-ft pattern although the effects of the blast were not as obvious. In situ leaching tests were not conducted. However, based on size consideration only, all three blasting patterns produced adequate breakage for successful leaching.

Jan 1, 1974

By William D. Schwab

In the technical literature of 1965 and 1966, there were several papers about future power for mining and construction equipment. Most of these papers made the same predictions: •More power •Better reliability and durability •Ease of service and maintenance •Operating economy •The possibility of future environmental concern •The entrance of the gas turbine In the five years that have since passed, some of the 1965-66 predictions have at least partially come true, while others have not been fully realized. Actually the list still appears sound today. Priorities may have changed and details may be different, but the main points cover the requirements for future prime movers quite well.

Jan 1, 1971

By Arthur W. Gray

The thermal analysis of a metal or an alloy is ordinarily made with the aid of heating and cooling curves in which transitions are indicated by the rapid changes in curvature that accompany changes in the rate of heat absorption or evolution. Analysis by the method that depends on the change in thermal expansivity is not customary, partly, at least, because of the difficulties involved in making the necessary measurements. However, under certain circumstances, the dilatometric method of analysis may possess advantages over the thermometric method that will justify the additional trouble required. The addition of 1 per cent. of zinc to an alloy has been found to produce upon the volume changes that take place during transition effects that suggest the possibility of using the dilatometric method of thermal analysis as a rather sensitive means of obtaining chemical information. Although the illustrations presented in this paper are drawn from data obtained during an investigation of dental amalgams, similar phenomena can doubtless be observed with other alloys. Some of the results found during an investigation made in 1917l have been confirmed by data on the thermal expansivity of amalgams published by Souder and Peters of the Bureau of Standards in reporting tests of dental materials.2 Although the Bureau of Standards made experiments for the purpose of discovering effects of including zinc as one of the constituents of a dental alloy—a matter much discussed in dental literature but without the presentation of reliable experimental evidencae to support the views of either side—the reports of the tests made by the Bureau give the impression that certain striking phenomena associated with the presence of zinc were not noticed. Among such phenomena arc those connceted with the conditions that determine whether or riot a specimen of amalgam becomes covered with droplets from which crystals develop.

Jan 1, 1921

By Henry A. Wriedt, John Chipman

Equilibrium in the reaction of hydrogen gas with oxygen in liquid nickel, iron, and their alloys has been studied at temperatures of 1500° to 1700°C. The equilibrium con^stant, 0/p, [% O], is greater in nickel then in iron by a factor of 45 at 1594 C. In the alloy steel range, the activity coefficient of oxygen is slightly increased by the presence of nickel. NICKEL is more resistant to oxidation than is iron, in both the solid and the liquid state. The solubility of oxygen,' however, is greater in nickel than in iron. The two metals and their liquid alloys constitute an interesting series of solvents in which the chemical behavior of oxygen can be studied by methods similar to those used for liquid iron.' Experimental Method The furnace assembly, including the tube for preheating the entrant gas, was the same as that described by Gokcen and Chipman. " controlled mixture of water vapor, hydrogen, and argon preheated to approximately the melt temperature impinged upon the surface of the liquid metal. The charge, weighing about 35 g, was held in an alumina crucible at constant temperature in the gas stream for a prolonged period, then quenched in a stream of cold helium, sampled, and analyzed for oxygen by the vacuum fusion method. The temperature of the liquid metal was measured by a Leeds and Northrup optical pyrometer which had been checked against a similar instrument certified by the National Bureau of Standards. The freezing point of electrolytic iron in hydrogen, taken as 153j°C, was used for frequent checks. This point and the emissivity determined by Dastur and Gokcen" established the transmissivity of the optical system. The emissivities of Fe-Ni alloys at 1535" are known from the experiments of Smith and Chipman,h nd it was assumed that the variation with temperature is parallel with that of iron. Recorded temperatures are probably accurate within k5"C. Preparation of Gas Mixtures—Since the ratio H,O:H, had to be much higher for nickel than for iron, it was found convenient to construct two separate systems for gas preparation. In both cases, the ratio of argon to the sum of the other two gases was at least 4, the proportion of hydrogen and water vapor being varied to produce H,O:H, ratios from 0.2 to 70. The primary purpose of the argon was to diminish the errors caused by thermal separation' in the gas phase. In addition, its presence lowered the saturation temperature required for a given H,O:H, ratio and minimized the difficulty of preventing condensation. Both systems were modifications of the one used by Dastur and Chipman.' For H,O:HI ratios greater than 2, welding-grade argon purified by passage over magnesium chips at 620°C was mixed with hydrogen produced in the electrolytic cell shown in Fig. 1. The design was based on a cell used by Bodenstein and Pohl," the important features of which area nickel wire cathode and sodium hydroxide solution as the electrolyte. The rate of hydrogen evolution was controlled by a calibrated ammeter and a rheostat in the circuit, the current efficiency being taken as 100 pct. Precise control of the argon flow rate at about 300 ml per min was achieved by means of a capillary flowmeter having a controlled pressure drop. The molar flow rate was measured volumetrically before each run, and a constant flowmeter setting was maintained thereafter. The A-H, mixture passed through a water saturator of the type previously described," the saturation temperature being maintained automatically with a fluctuation of k0.04"C. The tube between saturator and furnace was heated by a resistance winding. The system was of all Pyrex construction with the exception of the stainless steel tube containing magnesium chips. This was connected with the glass tubing at the upstream end by

Jan 1, 1957

By E. H. Griswold

The many complexities arising from our present oil pool proration systems emphasize the need for a suitable standard of property rights. Attempts at conservation and unitization agreements have frequently failed because of the lack of such a standard. The necessity of reducing production to consumption has caused umpires, committees, commissions and other governing bodies to allocate the production of flush fields among the respective owners. The methods of allocation vary widely and conservation of underground reserves is frequently neglected or misused. Critical economic conditions increase, rather than modify, competitive methods. In some fields we have irregular and uneconomically close well spacing. Many operators drill unreasonably large holes, take excessive sand penetrations or leave their wells untubed in order to secure higher potential open-flow tests than their offsets. All of these practices result in economic waste and frequently damage to the pool. Regardless of our agreement with the fundamental principles of proration or unitization, both are actual necessities in many of our present economic situations, and we are in urgent need of a suitable standard of rights to facilitate and simplify their operation. The problems pertinent to unit management are simple and of daily use in many partnership enterprises, but the problems of fair and proper division of production under either proration or unitization are, as yet, subject to controversy. The rights of respective owners must be ascertained and standardized before we can eliminate wasteful practices and still preserve constructive competition in our industry. Valuation of Tracts In a recent unitization conference it was found that each participant had a different basis for calculating the relative values of tracts. Some of these assumptions were as follows: 1. Unrestricted open-flow operation to abandonment. 2. Current proration system to abandonment.

Jan 1, 1933

By W. Spencer Hutchinson

IT is the purpose of this paper to describe a method used to determine the corundum contents of samples of hard crystalline gneiss containing both corundum and red garnet. A chemical analysis of the rock for alumina would not fix the amount of corundum because at least three other constituent minerals of the rock, mica, feldspar, and garnet, contain alumina combined with silica. Following are the principal minerals found in the samples, together with their specific gravity and hardness as given by Dana:

Jan 6, 1913

By M. W. Strong

The technique of handling drilling muds varies somewhat, partly because of personal factors but mainly because of differences in formation, the type of problems, and the general drilling conditions in different localities. The much greater depths to which bore holes are now carried have made necessary closer attention to and great modifications of all aspects of drilling-mud technique. Increased depth means smaller hole, smaller drill pipe, smaller clearances, higher pumping pressures, higher differential pressures between shows and the mud column, less accurate control of the weight of the mud column, delayed receipt of formation data, and poorer samples. It means longer delays and greater hazards in rectifying mistakes or dealing with accidental occurrences. Equipment on a larger scale is necessary and more pains must be taken with layout. Lastly, the budget costs of raw materials have risen to high figures and economy of time and of direct monetary expenditure have come to mean much more than formerly. A mud laboratory is now part of the essential establishment of a modern oil field and to it current problems can be submitted for the most thorough investigation. The detailed chemical properties of all materials purchased or quarried have to be investigated. Detailed data on the physical properties have to be ascertained and research on improvement of material and its most efficient use has to be carried out. In this paper will be discussed the main mud problems of Iran, some of which are peculiar to local conditions while others are of the general type common to all workers in this subject. Underground Conditions In deep wells in Iran the normal overburden may consist of: (1) up to several thousand feet of marls with interbedded sandstones and limestones of varying porosity and permeability; (2) beneath this a chemical series of rock salt and anhydrites, containing various marls and thin limestones,

Jan 1, 1939

By M. W. Strong

The technique of handling drilling muds varies somewhat, partly because of personal factors but mainly because of differences in formation, the type of problems, and the general drilling conditions in different localities. The much greater depths to which bore holes are now carried have made necessary closer attention to and great modifications of all aspects of drilling-mud technique. Increased depth means smaller hole, smaller drill pipe, smaller clearances, higher pumping pressures, higher differential pressures between shows and the mud column, less accurate control of the weight of the mud column, delayed receipt of formation data, and poorer samples. It means longer delays and greater hazards in rectifying mistakes or dealing with accidental occurrences. Equipment on a larger scale is necessary and more pains must be taken with layout. Lastly, the budget costs of raw materials have risen to high figures and economy of time and of direct monetary expenditure have come to mean much more than formerly. A mud laboratory is now part of the essential establishment of a modern oil field and to it current problems can be submitted for the most thorough investigation. The detailed chemical properties of all materials purchased or quarried have to be investigated. Detailed data on the physical properties have to be ascertained and research on improvement of material and its most efficient use has to be carried out. In this paper will be discussed the main mud problems of Iran, some of which are peculiar to local conditions while others are of the general type common to all workers in this subject. Underground Conditions In deep wells in Iran the normal overburden may consist of: (1) up to several thousand feet of marls with interbedded sandstones and limestones of varying porosity and permeability; (2) beneath this a chemical series of rock salt and anhydrites, containing various marls and thin limestones,

Jan 1, 1939

By H. J. Fisher, J. L. Walter

Two types of Si-Fe columnar ingots with preferred crystal orientation have been produced: a) ingots with (0011 directions of the crystals parallel to the longitudinal ingot axis and b) seeded ingots in which all crystals have the (100) [001]orientation with respect to the sides of the ingot. Measurements of freezing rates and temperature gradients indicated that columnar freezing occurred as long as the temperature gradient ahead of the solidification front was greater than zero. THE development of preferred orientations or textures in wrought metals may be influenced by the presence of a preferred crystal orientation in the ingot from which the product was made. The deliberate introduction of preferred orientation in the ingot for the express purpose of producing a particular preferred orientation in the wrought product has not, to the authors' knowledge, been reported in the literature.* This report describes the prepara- tion of ingots of 3 1/4 pct Si-Fe in which preferred orientations near (100) [001] were produced. These ingots were subsequently rolled to strip, 0.012 in. thick, to provide a sufficient quantity of polycrystal-line sheet having the (100) [001] orientation or "cube-texture" to evaluate the magnetic properties. The properties; and test results showing the advantage of the cube-textured Si-Fe magnetic sheet over magnetic sheel having the (110) [001] texture or "Goss" texture have been reported elsewhere.' The rolling and recrystallization textures of single crystals of silicon-iron having orientations near (100) [001] have been studied by Walter and Hibbard.2 They found that if the crystal has an original orientation such that the (100) plane is within 30 deg of the rolling plane, the recrystallization orientation will approach (100) [001]. If the (110) plane is nearly parallel to the rolling plane,

Jan 1, 1962

By AIME AIME

MONDAY evening a reception, supper and bridge in honor of the guests of the Woman's Auxiliary was given by the New York Section in the Engineering Woman's Club. After supper, tables were made up for bridge. Some tried jig-saw puzzles, while others merely visited. On Tuesday morning the annual business meeting was called to order by President Bassett. Mrs. Bassett read a note from Mrs. Hoover regretting her inability to be present, and then gave her welcome and message: It gives me much pleasure to welcome you in this annual meeting, and I hope you will be able to come next year, and those who are not able to come this year I hope will be here next year.

Jan 1, 1933

By C. K. Eilerts, J. D. Ham

Laboratory research has been conducted to evaluate the characteristic effects of condensate saturation on the mobility of gas in typical reservoir rocks. A pump with two pistons provided phases in equilibrium at controlled flow rates and constant liquid-vapor volume ratios. Core samples were tested in a holder that permitted sealing steady-state phases in the pore spaces under flow test pressures for weighing with sufficient precision to give an accurate measure of the attained saturations. Parameters of the study were pressure, apparent velocity, flowing liquid-vapor volume ratio, fluid composition, core material and length-to-diameter ratio. Tests were conducted at 515 and 1,515 psia to determine the effect of pressure on the mobility-saturation relationship. Influence of the apparent velocities 0.30, 0.15 and 0.07 cm/sec and of five liquid-vapor volume ratios from 0.0001 to 0.01 was determined at 515 psia The principal fluid system was nitrogen and and separator liquid from a Gulf Coast condensate, but the effect of a condensate of different viscosity was also determined. The significance of a possible concentration of liquid near the outlet end of the test cores was investigated. Core materials included a consolidated sandstone and a low-permeability limestone. Relative mobility and liquid-vapor volume ratio relationships are concluded to be dependent on pressure, saturation and, to a lesser extent, on velocity. For each porous medium and fluid there is a minimum saturation essential to two-phase flow, and high velocities of flow have only limited effect on saturations in this range. INTRODUCTION It is now recognized that knowledge of the availability of a reservoir gas — the period that gas may be recovered from a reservoir at a given rate — is as important as the estimate of gas in place. When reservoir conditions are such that pressure decline owing to production will result in retrograde condensation, liquid saturation can increase in the structure around the production well in a way that may restrict flow capacity, and hence future availability. l Based on a numerical solution of transient radial flow of single-phase gas-condensate fluids, 2 a program for computing the accumulation of condensate in a reservoir and the effect of this condensate on deliverability has been developed. During this development a need evolved for data that described the influence of pressure, velocity of flow and condensed liquid on mobility as recovery progressed. This paper presents the results of experimental investigation to obtain insight into the mobility relationship at reservoir pressures of gas-condensate fluids. A core holder for flow tests at reservoir pressure was developed to weigh the core and its fluid contents under pressure to determine saturation. A specially constructed pump was used to drive a two-phase fluid through the core until a steady state prevailed. The core was used as a differential device, and properties measured were intensive rather than extensive. APPARATUS Fig. 1 shows a schematic representation of the major pieces of equipment used in the mobility determination. The weighable core holder is connected to a two-piston, constant-displacement pump. Attainment of steady-state flow is indicated by stability of the flow differential read from the high-pressure manometer. WEIGHABLE CORE HOLDER An important part of the data needed was the mobility-saturation relationship. This required that mobilities and saturations be measured at pressures, flow velocities and liquid-vapor volume ratios characteristic of condensate reservoirs.

By L. H. Robinson

Triaxial compression tests on Indiana limestone indicate that chemical additives in the pore fluids can increase or decrease the strength in plastic failure but not in brittle failure. Tests using a series of the sodium salts of dicarboxylic acids show that odd-number carbon-atom chains decrease the yield strength as much as 3.0 x 10 3 psi, and even-number carbon-atom chains increase the yield strength as much as 9.0 x 102 psi. ,The most effective chemical (sodium citrate) decreased the yield strength of Indiana limestone from 16.0 x 103 to 12.0 x 103 psi. The chemical additives investigated have no influence on microbit drilling rate when drilling with zero differential pressure. However, when drilling at a 2.0 x 103-psi pressure differeniial and using an odd-number carbon chain compound as the circulating fluid, the roller bit drilling rates were slower than with water whereas the drag bit drilling rates were faster. One even-number carbon chain compound added to the circulating fluid produces the opposite effect: the roller bit drilling rate is slightly faster than with water and the drag bit slower than with water. INTRODUCTION A Russian book by Rehbinderl published in 1944 generated much interest in the possibility of aiding and accelerating the destruction of solids by the action of a liquid in which the solids are deformed. This book describes a process in which microcracks are generated during elastic deformation. To describe this process, the rock is divided into three zones: (1) the zone in which the destruction takes place, (2) the predestruc-tion zone (an affected area immediately below the destroyed zone) and (3) the undisturbed specimen. Consider a load applied normally to a surface of an infinite slab of rock. Immediately below the point of application of the load, the rock is destroyed by compression or shear forces. Below this area of destruction, because of a great number of discontinuities ranging from defects to weak points in crystals of discontinuities in crystal latices, very small cracks are created in or between the crystals (often referred to as microcracks). Upon removing the load, the broken rock in the destroyed zone could be removed. In the lower predestruction zone, however, the microcracks in and between the crystals could disappear by the process of rehealing, i.e., the molecular attraction from one side of the crack to the other side being sufficient to completely eliminate the crack. Thus, a large number of these microcracks possibly exist only for a relatively short period of time. The concept of small cracks being generated within the crystals of a rock is not unreasonable. If the rock matrix is deformed below the yield point, some of the defects present within the crystalline structure could start small cracks through the interior of the grains. Upon removal of the load, these microcracks reheal (or the newly generated surfaces come back together) so that all evidence of cracks completely disappears. Under various types of loading, and in various types of fluids, the rehealing of these cracks would be time dependent. If a liquid adhered to the surface of a rock, it could penetrate into the microcracks and thus delay or prevent the rehealing process. This suggests that the prevention of healing of the microcracks may be dependent upon the wetting characteristics of the solid. Thus, rocks which are water-wet should be more easily destroyed in water than in nonpolar hydrocarbon liquid. Adsorption of a liquid could also reduce the free surface energy which could explain the decrease in strengths of materials under nonrepetitive-type loading. Rehbinder's work prompted Boozer, Hiller and Serdengecti 2 to examine the effects of pore fluids on the deformation of rocks subjected to triaxial compression over a range of confining pressures, temperatures and strain rates. Fluids which strongly adsorbed on the rock grain surfaces decreased the strength of sandstone and limestone, which deformed plastically. For certain strain