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By L. D. Frink

THOSE actively interested in mining are fully aware of the ever-increasing difficulty of making conditions such that efficient work can be clone in underground openings, especially as higher rock temperatures are encountered in depth. This is also true where an effort is being made to cut down the burden of overhead expense by working headings 24 hr. in a day if blasting is done as often as is possible in that time. That the conditions resulting from both these causes have driven the native-born Americans from the mines and that their places have been taken by less efficient foreigners is a fact that we must all admit. The great war now being fought in Europe and the educational qualification clause written into our immigration law by the last Congress will probably limit very materially the supply of labor, such as we are now using in our mines, and will force upon mine operators the necessity of making this work appeal again to Americans. Metal tubing, with blower or exhaust fans, has long been used in supplying air to dead ends where natural ventilation is impossible, or in driving the smoke from such places, or in doing both, as the need might be. Here in Butte we have now come to use canvas tubing very extensively and find that it has many advantages not possessed by the metal. The use of flexible tubing is not new, but it has not been generally used in mining operations. Recent improvements, however, in the canvas itself and in the jointing of sections and manner of suspension have so increased its usefulness that it promises to add much to the efficiency of mining. There is now on the market a product that is impervious to air, is fireproof, and has a system of jointing which, permits it to be put up or taken clown in a few seconds. In this article an effort will be made to explain the manner in which canvas tubing is being used in the North Butte company's operations at Butte, Mont. The accompanying photographs will, I hope, help make clear what may be done with this material.

Jan 1, 1918

By C. G. Maier

COMMERCIAL processes of lead softening directly involve the behavior on fusion of mixtures of the oxides of antimony and lead, and the vapor pressures of these materials. Practically no quantitative data have been available for the discussion of lead softening from the point of view of the fundamental metallurgy of the process. The Pacific Experiment Station -of the United States Bureau of Mines, in cooperation with the University of California, in the course of its program of study of the fundamental properties of oxides and sulfides, recently made vapor pressure measurements upon the various forms of pure antimony trioxide.1 When these measurements were considered in connection with the softening and "fuming" furnaces which are often used for lead purification, an unexpectedly anomalous condition appeared. In brief, this anomaly consisted in the fact that in certain softening furnaces, where lead bullion of approximately 1 per cent antimony content was being treated at a temperature of approximately 1300° F., no appreciable volatilization of antimony occurred, there being produced only a "skim" containing from 15 to 20 per cent Sb, 65 to 60 per cent Pb, as mixed oxides. In the "fuming furnaces," where the temperature was only about 1400° F. and where an accumulation of "skims" from the primary softener was being treated with certain other antimony-containing materials, a considerable volatilization of antimony as oxide occurred; an "impure" skim of some 60 to 65 per cent Sb and 10 per cent Pb was also produced as mixed oxides. The latter material cannot be suitably treated in hearth-type or softener furnaces. The essential chemical difference between the first and second step is the customary use of some reducing material (such as petroleum coke) in the later operation. An obvious interpretation of the effect of coke in facilitating the fuming of the antimony is the supposition that the antimony may be reduced to metal, and volatilized as such. This supposition is improbable, however, when it is realized that a slight extrapolation of the vapor-

Jan 1, 1932

By S.H. Ash, P.S. Miller

Extensive and diversified resources justify large populations and great industries. To carry on the business of commerce and meet the demands of large populations, the utilization of tunnels in some form for transportation purposes constitutes an important link in modern civilization. The driving of tunnels has been appropriated by the tunneling branch of the heavy-construction industry, and the progressive steps taken by modern tunnel builders were not even dreamed of 50 years ago. Great strides have been made toward more rapid progress in tunneling in the United States during the past I0 years. Tunneling consists of a definite cycle of operations developed from ideas that are crystallized and translated into action programs through various engineering phases that begin with the first preliminary survey and do not end until the job is completed. Once the line of the bore is established and a time set for the completion of the work, the face must advance according to estimates prepared before the work commences. This schedule must be followed in regular sequence from the moment the drills start against a new face of rock until they are ready again to drill the Succdeding face, constituting a round. Mining is largely tunneling carried on under conditions often more inherently hazardous than actual tunnel construction, but for various reasons" tunne1ing is more hazardous than mining in any branch of the mineral industry. On the other hand, obstacles are sometimes encountered in heavy-construction tunneling projects that when met in mining enterprises do not offer comparable tasks to avoid or overcome them. One is the existence of water under high pressures. In mining enterprises, various alternatives offer a solution in driving a tunnel, even to the extent of its discontinuance or the abandonment of the mine, but a "construction" tunnel usually must go forward because some important project depends largely if not entirely upon it. This paper describes an unusual method of driving a water-supply tunnel through rock carrying water under pressures and conditions that did not permit the use of ordinary tunneling methods. The Delaware Aqueduct The new Delaware aqueduct is a Manhattan project of some magnitude; when regular it will contain what probably will be, for some time to come, the longest tunnel in the world. Various features in its construction are currently described in the trade journals of the construction industry, and informative engineering details are given in the Delaware Water Supply News, published twice a month by the Board of Water Supply of the City of New York. Work was begun on this project on March 24, 1937. The tunnel will convey water from reservoirs at the headwaters of the Delaware River to the City of New York.

Jan 1, 1943

By P. S. Miller, S. H. Ash

Extensive and diversified resources justify large populations and great industries. To carry on the business of commerce and meet the demands of large populations, the utilization of tunnels in some form for transportation purposes constitutes an important link in modern civilization. The driving of tunnels has been appropriated by the tunneling branch of the heavy-construction industry, and the progressive steps taken by modern tunnel builders were not even dreamed of 50 years ago. Great strides have been made toward more rapid progress in tunneling in the United States during the past I0 years. Tunneling consists of a definite cycle of operations developed from ideas that are crystallized and translated into action programs through various engineering phases that begin with the first preliminary survey and do not end until the job is completed. Once the line of the bore is established and a time set for the completion of the work, the face must advance according to estimates prepared before the work commences. This schedule must be followed in regular sequence from the moment the drills start against a new face of rock until they are ready again to drill the Succdeding face, constituting a round. Mining is largely tunneling carried on under conditions often more inherently hazardous than actual tunnel construction, but for various reasons" tunne1ing is more hazardous than mining in any branch of the mineral industry. On the other hand, obstacles are sometimes encountered in heavy-construction tunneling projects that when met in mining enterprises do not offer comparable tasks to avoid or overcome them. One is the existence of water under high pressures. In mining enterprises, various alternatives offer a solution in driving a tunnel, even to the extent of its discontinuance or the abandonment of the mine, but a "construction" tunnel usually must go forward because some important project depends largely if not entirely upon it. This paper describes an unusual method of driving a water-supply tunnel through rock carrying water under pressures and conditions that did not permit the use of ordinary tunneling methods. The Delaware Aqueduct The new Delaware aqueduct is a Manhattan project of some magnitude; when regular it will contain what probably will be, for some time to come, the longest tunnel in the world. Various features in its construction are currently described in the trade journals of the construction industry, and informative engineering details are given in the Delaware Water Supply News, published twice a month by the Board of Water Supply of the City of New York. Work was begun on this project on March 24, 1937. The tunnel will convey water from reservoirs at the headwaters of the Delaware River to the City of New York.

Jan 1, 1943

By Robert H. Aborn, J. J. B. Rutherford

It is now well known that troublesome intercrystalline corrosion may occur in austenitic stainless steels following exposure of the metal to a temperature within the range 1000° to 1500° F. (540° to 815° C.). The present paper describes a satisfactory method of estimating the extent of such corrosion, based on the measurement of the electrical resistance of a specimen before and after attack. This new method enabled us to study quantitatively the effect of several factors upon intergranular corrosion in the 18 Cr, 8 Ni type of alloy. The results show that susceptibility to this attack increases with increasing carbon content and grain size and appears to pass through a maximum for certain combinations of temperature of sensitization and period during which the alloy was maintained at that temperature; and are in complete accord with our interpretation of the mechanism of this phenomenon. The method is probably applicable to other metals or alloys subject to intercrystalline attack, such as the aluminum alloys of the duralumin type. The methods hitherto in use for estimating the degree of intergranular attack fall into three types: (1) microscopic examinationll (2) macroscopic examination of fractures, and (3) determination of the time required for complete failure or disintegration.2 None of these lends itself very well to a measurement of the extent of corrosion. The first two are qualitative in nature and the third provides an arbitrary value largely dependent on individual judgment, since failure is a progressive phenomenon and not a sudden event. Our experience is that weight-loss determinations, although valuable in some types of corrosion investigations, bear no simple relation to intercrystalline corrosion in this type of alloy, as is to be expected since the phenomenon probably involves only the thinnest films between adjacent metallic grains. Measurement of electrical resistance has been used recently in the study of some types of corrosion,3 but seems not to have been applied to

Jan 1, 1932

By C. Willard Hayes

Introduction.—The recent developments in the metallurgy of aluminum and its consequent rapidly growing use in the arts are at present attracting considerable attention to its ores. The success of the Hall electrolytic process, by which the metal is obtained directly from the oxide, has removed bauxite from the position of a rather uninteresting mineral to that of an important ore. Its production on a commercial scale is so recent, particularly in this country, that little attention has yet been paid to its mode of occurrence and origin.. Any investigation, therefore, which throws light upon these points should be of interest to mining engineers- at the present time, especially if the conclusions afford a basis for estimating the probable extent and value of deposits already known and a mane of directing search for others. Two localities in the United States have so far yielded bauxite in commercial quantities. These are in Arkansas and in the Coosa valley of Georgia and Alabama. According to descriptions of the Arkansas deposits by Branner, they bear little resemblance to those in the Southern Appalachians and their geological relations appear to be entirely different. Only the latter deposits are considered in the following paper. These have been briefly described by McCalley† and Spencer.† They were visited by the writer during the past summer and somewhat carefully examined, in connection with the study of the areal geology of the region. Location of the Deposits.—The ore is found irregularly distributed within. a narrow belt of country extending from' Adairsville, Ga.,

Jan 1, 1895

Jan 5, 1976

By William G. Pariseau

There are important phenomena in rock and soil mechanics that cannot be explained in terms of theories of homogeneous, isotropic materials. Subsidence of strata about mine openings is an example. In-situ stress measurements in nonisotropic sedimentary and metamorphic rocks is another. Patterns of joints, faults, fractures, and similar geologic features impart directional mechanical properties to rock masses that are locally isotropic or anisotropic. On the geologic scale, the nonhomogeneity of composite rock masses may, in certain instances, be dealt with as homogeneous anisotropy. The mechanics of large rock masses can, therefore, be expected to involve considerations of anisotropy. The source of the anisotropy is not relevant. Once the scale of observation is selected and the material is defined accordingly, the analysis of stress and deformation proceeds without regard to the numerical values of the material constants. There are also important phenomena in rock and soil mechanics that cannot be explained in terms of linear elasticity, theory. For the mechanical description of anisotropic geologic materials capable of deforming beyond the limit of purely elastic strains, a plasticity theory is required. The purpose of this chapter is to present a plasticity theory for anisotropic rocks and soils. The proposed theory is based on the work of Hill in anisotropic metal plasticity and represents an extension of his work so as to include anisotropic geologic materials. The point of departure from metal plasticity theory begins with the inclusion of the normal stresses as linear terms in the yield condition, which plays a central role in plasticity. Once the yield condition is established, the plastic strain increments are obtained immediately through the principle of normality. For practical applications, some simplification of the three-dimensional theory is re-

Jan 1, 1972

By T. A. Read, H. M. Otte

THEORETICAL analysis by Wechsler, Lieberman and Read of the crystallography of martensite formation has shown that the requirement for the existence of a macroscopically undistorted plane between austenite and martensite permits a calculation of the indices of the habit plane of the marten-

Jan 1, 1958

By George A. Morrison

The Columbia Chemical Division of the Pittsburgh Plate Glass Co. is at Bar-berton, Ohio, 35 miles south of Cleveland. For many years large tonnages of limestone have been brought to the Barberton plant from distant points. The stone is here burnt in vertical kilns, the resultant product then hydrated and the hydrated lime used in chemical processing. To eliminate the expense of these shipments, the company decided to investigate a limestone bed known to exist on company property at Barberton, where the stone is used. The bed lay at a depth of more than 2000 ft. and was known locally as the "Deep Lime." Chemical analyses of sludge from churn-drill holes made some years ago proved that the limestone was of sufficient purity to warrant diamond-drill exploration. Four diamond-drill holes were put down at well-spaced intervals, to represent fairly an area of four miles by one mile. Cores logged as to chemical and physical conditions were found to compare closely, and to corroborate the earlier evidence that the limestone was of superior quality for chemical use. A plant of 300 tons per hour was subsequently decided upon. SITe The yard at the chemical plant was already so congested that location of the projected mine within its area could not be considered. Eventually a site was selected 2 miles northwest of the plant, near the main line of the Erie Railroad. Here 412 acres were owned outright by the company and stone rights were obtained on 2 50 additional acres. This location required a transportation line of nearly 2 miles (8800 ft.), crossing two major highways, and to avoid interruption of deliveries to the plant, overpasses were planned. Geology The limestone in the immediate vicinity lies about 2200 ft. below the surface. Geologists* identify this stone as Delaware of Devonian age. It is overlain by 18 ft. of unconsolidated (sand and gravel), 100 ft. of water-bearing sandstone, and finally 2080 ft. of shale into which sandstone in thin layers is interbedded. The contact of shale and limestone is abrupt, flat-lying and very pronounced. Berea sandstone, often found at 520 ft., is absent, but Euclid sandstone was encountered, together with a seepage of oil and a small amount of methane gas. The limestone bed itself is 345 ft. thick, and overlies 200 ft. of gypsum. The lower part becomes dolomitic as it approaches the gypsum. A detailed study of the drill cores indicates that the upper 50 ft. are highest in lime and reasonably low in silica. The physical make-up shows several separating cherty layers. These occur at definite horizons and cause distinct partings, which become horizontal planes of

Jan 1, 1946

By T. PH. D. Egleston

THE origin of gold both in placer deposits and in veins, and especially the origin of nuggets, has been the subject of repeated discussions and investigations, which have been recently brought to my attention by several extremely interesting specimens sent to me for examination, and more especially by the one exhibited at the meeting of the Institute in February, 1880.* In the year 1874 I made some examinations of the hydraulic mines of Califor¬nia, and was very much struck with the distribution of the gold throughout these deep placers, which were almost invariably poor on' the surface, while gradually growing richer towards" the bed¬rock. The constant presence of fossil wood, and the large quantity of organic matter contained even low down in these beds, was also remarkable. Not being satisfied with the various theories advanced to account for the formation of these deposits, I began an investiga¬tion early in the year 1879 on the conditions of solubility of gold and the causes of the loss in working gold ore in a large way: The researches which I have undertaken show that gold must be considered a soluble rather than an insoluble metal, and that the conditions of solution are such as will be found anywhere where gold is likely to occur, and the solution may take place even under the ordinary cir¬cumstances of surface drainage, and may be going on freely even where the presence of gold has never been suspected, and that there are causes enough in nature to produce the solution of the gold in sufficient quantities to account for all the phenomena of both the vein and placer formations. The general theory with regard to the formation of these placer deposits and nuggets has been that they were the result of the de¬struction of pre-existing- vein-matter, which does not accord with the facts as shown in the deep placer deposits. The gold in such case would be distributed in layers of unequal richness throughout * Transactions of the American Institute of Mining Engineers, vol. 8, p. 451.

Jan 1, 1881

By Irwin Roman

NUMEROUS results and formulas have been published for analyzing seismic records, but most of them apply only to large-scale phenomena such as are encountered in studying earthquakes. In a few cases,1 formulas have been published for some of the simpler structures. In the present paper, an attempt will be made to analyze several types of struc-tures without using methods more advanced than those of a first course in calculus. In, tracing a disturbance through a medium, it is almost always possible to base the analysis on Fermat's Principle of Extreme Time, which states that waves of displacement travel between points in such a manner as to make the time of travel an extremum with respect to all neighboring paths. In the simpler cases, comprising most of those used in optics or geophysical prospecting, this time is a minimum and the principle is often referred to as the Principle of Least Time. Within a homogeneous medium, having a uniform speed of transmission of the disturbance in all directions and throughout the medium, the paths are straight and are refracted at the interfaces in accordance with the Snell law of refraction, which states that the ratio of the sine of the angle, made by the ray with the normal to the interface, to the speed of trans-mission is the same on both sides of the interface. Thus, in any medium composed of homogeneous sections, this same ratio has a constant value at all points. In particular, if all interfaces are horizontal, it is apparent that the angles of incidence are the angles made by the ray with the vertical direction. Furthermore, the incident ray, the refracted ray and the normal to the interface are all in the same plane at each refraction;

Jan 1, 1933

In our sessions devoted to geophysical prospecting, the greater part of the time heretofore has been given to the presentation of theoretical subjects or highly technical details by specialists directly engaged in the development and perfection of the various methods. This was necessarily so, for we wanted such information available for the benefit of other workers and for our members who were anxious to gain a reliable understanding of the principles involved, to enable them to form an opinion of the adaptability of this new technique to their special problems. The methods have now been actively applied by many reliable organizations for several years and in this period there has been opportunity for operating mining men, engineers and geologists to appraise them. We therefore felt that it would be desirable at this meeting to give some time to interchange of opinion concerning results from actual cases. Consequently, the Committee on Geophysical Methods of Pros pecting sent out letters of inquiry to numerous mining people, asking for frank statements of opinion based on results from geophysical surveys at their properties. We have received many replies, among which 30 or more are of specific interest. On the whole, the point of view is remarkably uniform. Except for one or two who were, perhaps, a bit irritated, the operating men who have replied consider the methods to be capable of yielding valuable information when suitable conditions exist. Their attitude is definitely one of tolerance and of confidence in the integrity and sincerity of the outstanding workers. There is, however, a very general feeling that the chances of attaining positive and trustworthy results are small unless the work is directed by, or at least carried on with the close cooperation of, a geologist or mining man who is thoroughly familiar with the local geologic and mineralogic conditions and with the relations of the orebodies to rocks and structure. From certain comments, I am inclined to think that some operators are not greatly impressed with the cheapness of the work. Probably they are not attaching much weight to cost per acre, but are thinking primarily of total cost in terms of significant results obtained. It is

Jan 1, 1932

Jan 1, 1897

By W. Francis

Before attempting to describe the application of recently acquired knowledge to the classification of coal it will be as well to consider the objects at which a scientific classification should aim. Here one can not do better than to follow the example of Clarence Seyler,l by quoting from Huxley's "Classification of Animals:" "By the classification of any series of objects is meant the actual or ideal arrangement together of those which are like and the separation of those which are unlike, the purpose of the arrangement being to facilitate the operation of the mind in clearly conceiving and retaining in the memory the characters of the object in question. Thus there are as many classifications of any series of natural or other bodies as they have properties or relations to one another or to other things. But the statement of the characters of the class ... is something more than an arbitrary definition ... it expresses firstly, a generalization based on and constantly verified by very with experience; and, secondly, a belief arising out of that generalization—in other worda. the definition of the class is a statement of a law of correlation or coexistence . . . from which the most important conclusions are deducible." In that same sense writes John Stuart Mill, in the chapter on classification in his "Logic:" "The ends of scientific classification are best answered when the objects are formed into groups concerning which a greater number of general propositions can be made, and these properties more important, than could be made respectiug any other groups into which the same things could be distributed. The properties, therefore, according to which objects arc classified should, if possible, be those which are causes of many other properties, or, at any rate, which are sure marks of them." Now in the case of coal, the properties which have been used from time to time for classification purposes are the ultimate analysis, volatile matter, caking power, calorific power, burning properties, etc. Seyler has shown that there is a general law of correlation or coexistence between the ultimate composition and the other properties. The ultimate composition, therefore, of the natural series of bodies known as coal is the

Jan 1, 1930

Jan 1, 1961

By Raymond D. Daniels, Frank E. Rizzo, James D. Gerber

ThIS discussion describes a method for the addition of small amounts of oxygen to columbium (niobium) in an accurate and reproducible manner. The method is based on the complete reduction by columbium of a carefully weighed amount of another metal oxide. The equilibrium Pq associated with Cb-CbO mixtures is extremely low, e.g., 10"25 atm at 100O°C, and the pressures over Cb-0 solutions are even lower. The equilibrium Pq associated with a given metal-metal oxide mixture can be easily obtained, with the aid of a Richardson-Jeffes chart.' Although columbium should effectively reduce almost any metal-metal oxide combination, the proper choice of a metal-metal oxide system is complicated by the low rate of oxygen transport in the gas phase at low oxygen pressures and the difficulty in reducing any columbium suboxide formed during the reduction of the oxygen source material. Thermodynamically, oxide formation on columbium will be avoided so long as the oxygen partial pressure over the columbium is below the equilibrium pressure associated with the mixture Cb-CbO. The logical choice of a source for oxygen would appear to be a mixture of Cb-CbO, since oxide formation would be precluded by nucleation difficulty. But calculations using the kinetic theory of gasses indicate that, for a temperature of 900°C, the reaction would proceed too JAMES D. GERBER, formerly Research Assistant, University of Oklahoma, Norman, Okla., is Research Metallurgist, Air Force Weapons Test Laboratory, Kirtland Air Force Base, N. Mex. FRANK E. RIZZO, Junior Member AIME, formerly Assistant Professor of Metallurgy, University of Oklahoma, is Associate Professor of Metallurgy, University of Texas at El Paso, El Paso, Tex. RAYMOND D. DANIELS, Member AIME, Professor of Metallurgical Engineering, University of Oklahoma, is an NSF Fellow, Institute de MBtallurgie Structurale, Universite de euch:tel, Neuchitel, Switzerland. Manuscript submitted October 28, 1968. IMD

Jan 1, 1970

By R. G. Hall

The method of crushing rock by throwing with violence against a resisting surface does not differ in principle from the method of dropping it from a height upon a specially arranged surface. The former is applied in various mills now in use, especially those for reduction of the softer rocks and minerals. The latter is the principle of the Hadsel mill. Probably not new, but Hadsel's method of approach is at least novel, and applicable to hard as well as softer rocks. An elevating wheel raises the rock and drops it from a height upon a hard metal plate or series of plates. The first commercial mill consisted of two units, one on each overhung end of a horizontal shaft, driven by a gear train from a 100-hp. motor. A description of this machine, then in operation at a mine at Georgetown, Calif., was printed in the Engineering and Mining Journal (April, 1932) and need not be repeated here. That machine took mine run ores of a size up to 12 in. and successfully produced a pulp of approximately minus 60 mesh, suitable for flotation. The mills were each 24 ft. in diameter and 3 ft. in width of face. The elevating buckets were formed of steel plates, extending inward from the periphery, inclined to the tangent at 75". This plate was 3 ft., the width of the wheel, and 2 ft. deep. One side of the wheel towards the carrying shaft was closed, the other was open except for the rim plate enclosing the ends of the buckets and extending inward about 5 ft. on the radius. About a 90" arc was immersed in a concrete tank, which acted as a classifier. The breaking plates, seven in number, were carried cantilever through the open side of the wheel. The lowest plate was placed just above the water level. The illustrations (Figs. 1 and 2) make plain the general arrangements. The plant set-up was somewhat crude but worked well enough to demonstrate the weak points of the mill. In this operation it was early apparent that, considering all the factors from delivery of the mine run ore to the final pulp for flotation or cyanida-tion, the Hadsel mill offered possibilities of great simplicity of plant and savings in power. Continuous operation developed mechanical weaknesses, some of which were readily discernible in details of design, some became more apparent as operations progressed.

Jan 1, 1935

MINING; SOLUTION U.S. 4,066,297 - In the solution mining of uranium from an underground deposit of uranium ore using an alkaline leaching solution, precipitation of alkali metal salts is avoided by maintaining the Injected leach solution of an alkaline carbonate or bicarbonate and an oxidant undersaturated with respect to carbonates Undersaturation is effected by use of a water softening unit or by bleeding a portion of the recycled alkallne leach solution. A P. Spence, assigned to Atlantic Richfield Co Jan. 3, 1978 4 pp. (299-4). Filed: 6-1-76 (69 1,344)

Jan 1, 1979

By A. J. Sinclair

Sampling methods for feasibility studies are dependent on geological characteristics of the deposit being evaluated. A preliminary geostatistical study is required, taking into account autocorrelation aspects of variables under study in order that sample plan design can be optimized to produce grade and tonnage estimates within stipulated error limits. In general, regular sample distribution is to be aimed for, and regular sample lengths (from drill core or cuttings, for example) are preferred in order to facilitate statistical analysis. Sample plans are modified and improved (either technically or economically), as a sampling program proceeds and additional information is obtained. Bulk samples for metallurgical testing can be evaluated in terms of the variance shown by all such samples in a deposit and the internal variability of grade. Attention to these sources of variability will ensure proper evaluation of pilot test results from bulk samples. In addition, a general mineralogical study of a deposit is an important, often ignored, requirement in a more general but semi-quantitative evaluation of the representativeness of a bulk sample; and, moreover, provides information useful in optimizing plant design.

Jan 1, 1978