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By M. A. Orehoski, J. M. Hodge

It is now generally conceded that if a steel is to develop optimum physical properties in the conventionally quenched and tempered condition, the microstruc- ture after quenching should consist wholly of martensite; and that transformation of austenite to intermediate-temperature products during quenching will have a deleterious effect upon the physical properties, particularly the toughness, of the tempered material. This implies that, in order to obtain the optimum physical properties from a given steel, its "harden-ability " should be high enough to suppress all transformation except that to martensite under the heating and quenching conditions to which it will be subjected, and this premise is probably the most important reason for hardenability control. However, the criterion of hardenability that at present is most widely accepted and used is based on a microstructure of 50 per cent martensite. This criterion, which was suggested by Grossmann,' does have considerable justification. It may be readily measured by a fracture or etch test and, since it represents the point at which the hardness is changing most rapidly with variations in cooling rate, it may be determined empirically from a hardness-depth curve by determining the point of steepest slope (the inflection point). Furthermore, in plain carbon steels or in steels of low hardenability, the difference in hardenability expressed in

Jan 1, 1947

By Eugene P. Pfleider

Research indicates that the cube diamond is a superior stone for drill bits. It can be oriented to combine a long cutting edge with structural strength and high resistance to wear. Test bits set with preferred orientation give double the bit life at astoundingly low diamond loss in comparison to oriented octahedral diamonds. A PROGRAM of research on the orientation of diamonds in drill bits has been under way for several years at both the United States Bureau of Mines Experimental Mine at Mount Weather, Va., and the School of Mines and Metallurgy of the University of Minnesota. Reports on past work done both in the laboratory and the field are available in the technical press.1,3,4 The results of such drilling, done under comparable conditions, show that bits having diamonds oriented in a direction that combines structural strength and greatest hardness not only can advance somewhat faster than random set bits but can do this with a unit diamond loss of 50 pct or less. Several bit manufacturers have initiated the training of diamond setters in the principles of orientation on the basis of the above-mentioned research results. The basic information on the crystallography and hardness variation of the diamond was presented in an earlier paper,' which pointed out that the diamond is several hundred times harder along certain directions and certain faces than on others. The same article discussed the drilling results obtained with a group of nine bits having octahedron diamonds set with on-point, positive (gouge) rake, and negative (drag) rake orientations. The testing of oriented cube diamonds is an extension of this research program, employing the same procedures and equipment (Hy Mac hydraulic drill unit, EXT diamond core bits, St. Cloud Pink granite) as previously described. This current work covers the test experience of seven bits set with cube diamonds running approximately 10 stones per carat. The individual stones were near perfect cubic form; hence it was simple to orient them in any desired direction. The cube is a comparatively rare crystal form of the diamond, although considerable numbers are produced from the Congo. It is understood that most of the cube diamonds are retained in Africa, where they are either used locally for diamond bit manufacture or ground up to make powder. They have been considered to be an inferior stone for drilling purposes.

Jan 1, 1954

By F. L. Clerc

The lead and zinc region of SW. Missouri is interesting, not only by reason of the value of its output, which ranges in the neighborhood of ten million dollars a year, but even more because of the facilities which it offers for the study of certain forms of ore-deposits, of' which the loci and genesis are somewhat obscure. Although the mineral species found in the region are few and of common occurrence, crystallization has taken place on a generous scale, and unusual forms abound in many combinations, presenting examples of pseudomorphism, para-genesis, metasomatic replacement and the action of mineral-depositing and mineral-dissolving waters. For the mineralogist, lithologist, and specialist in certain lines of metamorphism, it has peculiar attractions, while the systematic geologist will perhaps find its chief claim to attention in the simplified problem it presents, in the study of ore-deposits. In addition to the phenomena above enumerated, it presents instances of well-developed comb-structure in the ores, fissures and faults, and slickensides—features usually associated with extensive movements in the earth's crust, and believed by some authorities to prove the deep-seated origin of the ores. In connection with these occurrences, the absence of all igneous rocks from this region is noteworthy and significant. For that reason, the simplified case presented by the Joplin region, from which these rocks have been eliminated as a factor, is specially valuable. Having had unusual opportunities to watch the development of this district, I have been deeply interested in the bearing of the revelations of the Joplin mines upon questions of universal importance to the science of ore-deposits; and it was to my great regret that the project of a meeting of the American Institute of Mining Engineers at Joplin, proposed in 1892, was

Jan 1, 1908

By S. A. Allison, N. P. Finkelstein

After a brief consideration of the properties of zinc sulfide minerals, their flotation characteristics, and their reactions with thiol collectors, the literature on the activation of the minerals by cupric ion, their deactivation by cyanide, and their depression is reviewed in detail. The distinction between deactivation and depression is stressed. The contradictions in the published results and theories are discussed and attempts are made to resolve them. It is concluded that, whereas all aspects of the subject require further investigation, the study of depression is most likely to yield benefits in practice.

Jan 1, 1976

By Samuel Daniels

Aluminum-base alloys containing small amounts of copper and magnesium possess but ordinary physical properties as sand cast, but may be treated to give a remarkable range of tensile values and of Brinell hardness. The high-copper (4.5 per cent.) duralumins must be given a protracted treatment which in nature resembles the malleableizing of white cast iron; the low-copper (2.25 per cent.) duralumins develop an excellent combination of strength and ductility with a treatment which requires a maximum of 5 hr. to be completed. THE wrought alloys of aluminum with small amounts of copper and of magnesium have, with the development of the automotive and aircraft industries, sprung into prominence through the medium of duralumin; but the cast alloys remained in the background because their possibilities in the heat-treated condition were either not recognized or not fully investigated. In 1919, the Bureau of Standards published a preliminary survey1 of this field, which pointed out that, in general, the ultimate strength and the percentage of elongation of the alloys of aluminum with and without magnesium could be improved by so simple a treatment as heating to 932° F. (500° C.) for 2 hr., cooling in, air, and aging at room temperature for several days. British investigators, too, working with chill-cast material, found that " considerable improvement in the mechanical properties of copper-aluminum alloys' may be obtained from suitable heat treatment applied to castings."2 Jeffries and Gibson3 made the first contribution to the literature dealing exclusively with the heat treatment of sand-cast aluminum-base alloys, describing the effect of small additions or of combinations of copper, magnesium, and iron on the response to a short heat treatment comprising heating at 932° F. in a

Jan 7, 1924

By C. S. Matthews, H. C. Lefkovits

The purposes of this study are (a) to determine the accuracy of a previously proposed method for calclrlating average reservoir pressure and (b) to find a method for estimating the shape of the drainage area of each well in a bounded reservoir. Both numerical and experimental methods are used to determine the pressure distribution and the location of drainage bounrlaries in idealized reservoirs at steady state. A number of photographs are included which show flowlines and drainage areas in reservoir models of various shapes. Results from these studies are then compared with those from the previously proposed method for calculating average reservoir pressure.' It is concluded that the previously proposed method is sufficiently accurate for most reservoir engineering purposes. In addition, some simple methods are given for estimation of .shapes of drainage boundaries. INTRODUCTION A method for the determination of the average Pressure in a bounded reservoir was previously developed by Matthews, Brons, and Hazebroek,1 and presented at the Petroleum Branch Fall Meeting in 1953.† In aP- plying this method, the reservoir was first divided into drainage volumes; second, the average pressure in each drainage volume was calculated; and third, these drainage volume pressures were averaged volumetrically to give the average pressure in the reservoir. It was shown that each well's individual drainage volume, at steady state, is proportional to the well's production rate; however. the question of how to estimate accurately the shape of these drainage volumes could not be answered. Furthermore, in calculating the average pressure for each drainage area, the actual drainage areas, which are in general quite asymmetric in shape, are replaced with one of the symmetric prototypes given in T.P. 3876. A question may then be raised as to how accurately the symmetrical figures depict the pressure behavior of the actual unsymmetrical drainage areas. The study reported on in the present paper was made in an attempt to shed light on the above questions. METHODS It was shown in T.P. 3876 that after a period of steady rate of withdrawal the rate of pressure decline becomes constant at every point in a bounded reservoir containing a single-phase fluid whose compressibility is small and constant and whose viscosity is con-

Jan 1, 1956

By Thomas V. Falkie

4.3-1. Introduction. DEFINITION OF PRODUCTION SYSTEMS ENGINEERING. Surface mines, like most other mining and manufacturing operations, are usually organized along functional departmental lines. Frequently a mine manager will have his responsibilities divided among production, maintenance, administrative, and engineering functions. Often these are separate departments, but various combinations and variations of these functions can be found in mining companies throughout the world. The production function is responsible for physically removing the ore from the ground, processing it, and shipping the product to its market. The production manager supervises and is responsible for all man-machine systems necessary to extract and process the ore. The maintenance function, which is sometimes included within the framework of production, has the task of insuring the maximum availability and longevity of equipment needed to produce the ore. The administrative function is responsible for accounting, personnel, industrial relations, purchasing, public relations, property, and other related staff functions. For purposes of this chapter, engineering can be described as the function which plans, designs, and supervises construction of physical plant and equipment. In this context engineering includes mechanical, civil, chemical, electrical, and mining engineering. However, another phase of engineering is to prepare plans to insure that the various man-machine components function in an optimum way towards the single most important goal of any enterprise-the maximization of return on the investors' money. Along with the planning, another duty of engineering is to audit all phases of the operation for the purpose of recommending improvements toward this same general goal. These latter two ideas form the basis for a discussion of production engineering and systems engineering. Production engineering is a catchall, problem-oriented function whose duties can include: 1) solution of day-to-day production problems, 2) short-

Jan 1, 1968

By L. S. Darken

In the study of reactions occurring in liquid iron, alone or in contact with a liquid oxide or slag phase, it has been found that the experimental data over a limited range of concentration can in some cases be represented satisfactorily by the simple equilibrium expression where (P) denotes the concentration of a product and (R) the concentration of a reactant in the reaction r1R1 + r2R2 + • • • D P lP1 + P 2P2 + • • • Some of the reactions for which it holds are listed in Table 1. For others, however, the simple equation apparently does not hold. This has been attributed to an improper method of expressing concentration (for instance, weight per cent instead of mol fraction); or it has been supposed that the solutions are not ideal in the sense that the activity of a component is not proportional to its true mol fraction. But it may be that the problem has been oversimplified by neglecting some molecular species actually present; that is, by considering only the ostensible simple components and thus leaving out of account possible compound formation. It is the purpose of the present paper to point out how, in a group of related cases, a reasonable consistent assumption relative to the presence of a compound makes it possible to express the experimental data satisfactorily by the simple equilibrium expression when this compound is taken into account, and to bring into harmony data referring to different reactions in liquid iron. There are several a priori reasons for believing that solutions in liquid iron should not deviate far from ideality, provided that the concentration of solute is not too great and is expressed in proper terms. The factors that commonly lead to nonideality in systems at ordinary temperature— as ionization or the occurrence of polar and nonpolar molecules—are presumably less effective in inetal and in slag systems at high temperature. Again, the type of equation commonly used to express the value of

Jan 1, 1940

By J. M. Hodge, M. A. Orehoski

It is now generally conceded that if a steel is to develop optimum physical properties in the conventionally quenched and tempered condition, the microstruc- ture after quenching should consist wholly of martensite; and that transformation of austenite to intermediate-temperature products during quenching will have a deleterious effect upon the physical properties, particularly the toughness, of the tempered material. This implies that, in order to obtain the optimum physical properties from a given steel, its "harden-ability " should be high enough to suppress all transformation except that to martensite under the heating and quenching conditions to which it will be subjected, and this premise is probably the most important reason for hardenability control. However, the criterion of hardenability that at present is most widely accepted and used is based on a microstructure of 50 per cent martensite. This criterion, which was suggested by Grossmann,' does have considerable justification. It may be readily measured by a fracture or etch test and, since it represents the point at which the hardness is changing most rapidly with variations in cooling rate, it may be determined empirically from a hardness-depth curve by determining the point of steepest slope (the inflection point). Furthermore, in plain carbon steels or in steels of low hardenability, the difference in hardenability expressed in

Jan 1, 1947

By H. W. Gudenau, R. S. Chatty, W. Wenzel, M. Ponthenkandath

During several experimental programs conducted at the Institute of Ferrous Metallurgy, Technical University, Aachen, whisker formation was observed when iron ores were reduced at low as well as at high temperatures. Thus, in an attempt to find the reason for the volume change taking place during reduction, iron whisker growth was observed. Whisker growth appears to be one of the important reasons for the swelling of pellets. One set of experimental observations determined that when iron forms as needles rather than as a crust on the surface of oxide, the pellets became very porous. In related experiments, the beneficiation of finely disseminated iron ores, in which the metallic iron is separated from the gangue in granular or nodular form, was achieved by a reduction-concentration method. In this process, which is conducted at sufficiently high temperatures, oxide whisker growth, resulting from the formation of volatile suboxides and a gas transport mechanism, plays a vital role in the joint deposition of SiO, and iron from the vapor stage.

Jan 1, 1973

By Blamey Stevens

(Butte Meeting, August, 1913.) THE following paper aims to make a full explanation of the phenomena of rock jointing. It may be unnecessary to give any general description of what are termed joints in rocks, but. Professor Geikie's clear and faithful generalizations are so illuminating that no excuse need be given for introducing the following and other quotations into this paper: "Almost all rocks are traversed-by vertical or highly inclined divisional planes termed joints. These have been regarded as clue in some way to contraction during consolidation (fissures of retreat) ; and this is no doubt their origin in innumerable cases. But, on the other hand, their frequent regularity and persistence across materials of very varying texture suggest rather the effects of internal pressure-and-movement within the crust."1 General Explanation.-In this paper I show that the phenomenon of jointing may to a large extent be accounted for by the pressure of the water contained in the pores of the rock. To understand this, each constituent grain of. the porous material may be considered to be separately compressed by the 'water which submerges it. As all the grains are held together by cohesion, the whole mass is contracted by this pressure. In an indefinitely extended mass, however, there must be a limit to the possible contraction without rupture, because the material is restrained from. moving freely by other material around its boundaries. The mass of rock thus becomes broken up. This phenomenon is known as " shrinkage " jointing. The terra "shrinkage" is an apt one, if it be understood that the shrinkage of the rock is often brought about by change of stress. Stresses.-The compressive component of water stress on the individual grains is evidently the same as that of the water with which it is in contact. This is so, both. before and after the jointing is formed. Before the jointing is formed there is, however, a tensile stress in one or more directions which keeps the material from contracting.

Jan 7, 1913

By M. R. Geer

THE importance of the size composition of coal is reflected in the differ-ence in price of the various sizes of the same coal and in the large number of primary sizes and mixtures of sizes produced by the modern preparation plant to meet the demands of a market that in late years has grown increasingly conscious of coal size. The importance of size in the indus-trial and domestic uses of coal has its counterpart in the role played by size composition in the laboratory examination of coal. Investigation of many of the physical properties of coal in their relation to its uses requires an evaluation of size composition. In fact, the Standards on Coal and Coke issued by the American Society for Testing Materials in 1936 contains 12 standard methods of testing that involve some use of size composition. The screen analysis is, of course, the standard method of determining size composition, whether the material is coarse run-of-mine coal or fine pulverized fuel. Customarily, the analysis is reported as the weight percentages retained on or passing each of a series of testing screens, the number of which may range from only two or three to as many as 20. When more than two or three sieves are used, which is usual, the number of weight percentages obtained is so great as to make the analysis difficult to comprehend. Direct comparison of analyses made on the same sieves is hard, and comparison of analyses covering the same range of sizes but made oil different sieves is next to impossible. Consequently, a frequent purpose of sizing tests-correlation of size with properties and charac-teristics related to size-is rendered difficult.

Jan 1, 1938

By G. H. Wilson

INTRODUCED in 1946 to serve a need in power- plant operation, closed-circuit TV has been used by well over 200 organizations in approximately 25 different industries. Known as industrial television, or simply ITV, it can be described as a private system wherein the television signal is restricted in distribution, usually by confinement within co-axial cable that directly connects the TV camera to one or several monitors, Figs. 1, 2. The picture is continuous and transmission is instantaneous, permit- ting an observer to see an operation that may be too distant, too inaccessible, or too dangerous to be viewed directly. Destructive testing or the machining of high explosives can now be conducted hundreds of feet away by personnel who still have close control through the eyes of the TV camera. It is also possible for one man to control operations formerly requiring the co-ordinated efforts of several workers. For example, at a large midwestern cement plant conveyance of limestone from primary crusher to raw mill and loading into five storage bins once necessitated the work of two men, one having little to do but prevent spilling of material by manually moving the tripper on the belt conveyor as occasion required. TV cameras mounted on the tripper now provide bin level indication to the conveyor operator at the crusher position so he is able to control the entire loading operation remotely, Fig. 3. By means of a switch, the picture from either camera is alternately available on a single viewer, or monitor, Fig. 4. Each camera is mounted on the tripper by means of a simple adjustable support and looks down into the bin, which is identified by the number of cross members on the vertical rod. Each associated power unit is located on a platform above the camera, Fig. 5. This centralized control by means of TV often has produced superior results, and in many instancés saving in operating costs has been sufficient to write off equipment costs within six months to a year.

Jan 7, 1954

By A. E. Martin, Gerhard Derge

IE the molecular constitution of molten slags were better known, the nature of chemical reactions in slags and between slags and metals could be better understood and as a consequence might be better controlled. Constitutional information can be obtained by studies on either the molten or the solidified slags. Valuable as the studies on solidified slags admittedly are for many purposes, especially as control methods in steelmaking, they are always of questionable value in giving information on the molecular constitution of liquid slags. However, the characteristics of molten slags such as viscosity, rates of dilfusion, and electrica1 conductivity can be determined experimentally and interpreted along with other knowledge on slag-metal and slag-gas reactions so as to provide direct information on liquid slags. Metallurgists are accustomed to regard reactions in molten slags as involving only neutral molecules, whereas it is quite possible that ionic constituents are actually involved. For example, the dissociation of calcium silicate usually is represented us Ca2SiO4 = 2CaO + SiO2 although a reasonable alternative would be to write Ca2SiO4 = 2Ca+2 + Si04-4 Such ionic dissociation has been suggested frequently without adequate experimental proof. This paper deals especially with electrical conductivity measurements on slags oi the blast-furnace type. These measurements were made to determine whether or not slags are ionized and, if so, to provide a qualitative estimate of the extent of ionization. Electrolysis experiments that indicate the identity of the ions present are also reported. Since the presence of ions has not been considered carefully in modern slag studies, the relevant literature will be reviewed. Review of Literature In 1906 Aikenl obtained a patent for a continuous process of producing iron electrolytically by passing a direct currenl through a bath of FeO.SiO2 to which iron oxide was added periodically to maintain a uniform concentration. The patent also included the addition of CaO and MgO to the bath to lower its melting point. The silicate melts involved were thus in the same system as basic open-hearth slags but with higher FeO and lower CaO contents. Electrical conductivity measurements were made on some molten silicates by Doelter2 in 1907. Natural silicates, such as

Jan 1, 1943

By N. Lilienberg

Refractory materials play much the same part in the producion of metals as houses and shelter for men, and it therefore seems useful to discuss sometimes the ways of manufacturing them. In fact, it appears to me that too little has been said on this important matter, probably because the manufacturers of fire-brick do not care to publish details for the benefit of competitors, but perhaps, also, by reason of the indulgent indifference of consumers. Judging from the revolutions in the manafacture of iron and steel caused by using calcareous materials for the furnace-bottoms, it does not seem improbable that in the future basic bricks may be produced suffciently strong for building also side-walls and arches, and perhaps, also, for use in blast-furnaces. But the existence of the present difficulties of great shrinkage in burning and small strength against compression, which limit the possibility of using basic bricks to Bessemer converters and such open-hearth furnaces as permit the bottom to be separated from the superstructure, seems to indicate still a long and extensive use of silica fire-bricks. I am not prepared to say anything about American fire-brick making, but knowing that industries abroad are watched with increasing interest by American manufacturers, I have imagined that this association would like to hear some facts about the way firebricks arc made in my country—Sweden. Well-known as it is that Sweden produces a high quality of iron, it is perhaps not so universally known that the same country produces a very high grade of silica fire-brick, whereby most of its own wants are supplied. In giving the following sketch I can, of course, not claim that all the facts are entirely new, but shall consider my object attained if American manufacturers can derive some benefit from the comparison of the following methods with their own, and if some discussion on this important subject can be aroused which will contribute to further progress. In order to show the extensive use of domestic fire-bricks in Sweden, where English bricks are easily obtainable, I mention the fact that about twelve millions of all kinds of fire-bricks (reduced to

Jan 1, 1885

By Robert Ammon

THE milling practice at Mascot, at present, consists of dry crushing to 5/8 in., jigging, fine grinding, and flotation. The ore arrives at the mill from two mines, No. 1 mine shaft being located in the mill proper, and No. 2 mine shaft being situated about 2000 ft. east of the mill. No. 2 mine is served by a coarse-crushing plant and aerial tramway to the mill bins. In jigging the No. 2 mine ore, 50 per cent. of the mill feed is rejected by the jigs as a jig tailing ranging from 5/8 in. to 10 mesh; the balance of this ore, after removing a jig concentrate, is ground to flotation feed. In jigging No. 1 mine ore, approximately 80 per. cent. of the mill feed is rejected as a coarse jig tailing, and the balance is ground to flotation feed without the removal of a jig concentrate. The difference in the treatment is due to the fact that No. 2 mine ore carries a higher content of zinc than that from No. 1 mine. Of the total concentrates produced, 30 per cent. are made on jigs and 70 per cent. by flotation. At present, 1350 tons of No. 2 ore and 800 tons of No. 1 ore are treated each 24 hours. The recoveries for a typical week are as follows: Heads 3.55 Jig concentrates 61.30 Jig tails 0.80 Flotation concentrates 60.60 Flotation tails 0.09 Extraction 86.50 The associated minerals are a straw-colored sphalerite, dolomite, calcite, pyrite, quartz, and a small amount of greenockite, which occurs as a stain and sometimes small crystals along with sphalerite, but is comparatively rare. Pyrite is present in small quantities, usually less than 0.5 per cent.; quartz occurs in bands a few inches thick. A complete analysis of the ore is as follows:

Jan 9, 1924

By J. E. Johnson

OF the many items of information necessary to the successful management of the blast-furnace, few are more important than knowledge of the location and movement of the stock: line:—whether the furnace is full and has been kept so; whether the stock is settling regularly or slipping; and, if slipping, how often it has slipped, at what times, and how far at each time. To obtain these data, a man is sometimes stationed at the top of a pair of mechanically-filled furnaces, sim-ply to watch and gauge them by hand in the old-fashioned way. A more recent practice is the suspension of test-rods from ropes leading over pulleys to the ground-level, where the ropes are mound on small drums with graduated peripheries and provided with crank-handles, whereby the skip-man or some other person can quickly and conveniently gauge the position of the stock-line in the furnace. I believe the credit for this great improvement belongs to Messrs. McClure $ Phillips of Sharon, Pa., who were, as far as I know, the first to apply it, and who have a patent for it. The valuable indications gained by application of the Uehling pyrometer to the down-comer are not to be ignorcd; but the information thus furnished is somewhat indirect, and there is no scale for the translation of " top-temperatures " into " feet down." Moreover, this apparatus, as a whole, is delicate, and the cost of installation and maintenance is high. If the record furnished by the Uehling pyrometer is not in the most desirable form, the test-rods, on the other hand, give no record at all, except through the memory or notes of a man who, to say the least, is not gauging continuously, and who may omit to report an improperly low stock-line, if it be due to a fault of his own.

Jan 1, 1906

By Charles Prasky, Robert K. Zahl, John C. Nigro

Bench scale and pilot plant research was conducted using dolomitic (CaO - MgO) lime as the basic additive in the preparation of self-fluxed pellets from a typical magnetic taconite concentrate (5.5% SiO2). The specific objective of this investigation was to ascertain the viability of the magnesia lime pellets in high temperature oxidizing and reducing atmospheres. Pellet basicity and induration temperature were major parameters affecting fired pellet quality; temperatures ranging from 1200° to 1250°C appeared to be the most favorable for production of self-fluxed pellets with basicities (B) above 1.0. Comparison of the mechanical and metallurgical properties of regular (acid) and self-fluxed pellets (B = 1.55) produced under similar conditions in a modified grate pelletizing machine showed that the selffluxed pellets were more resistant to abrasion and to high and low temperature reduction disintegration, an important consideration in commercial application. The +3 mesh Linder index increased from 68% (regular pellets) to over 90% (self-fluxed pellets). The reducibility and swelling indices of the self-fluxed pellets were found to be comparable to the regular pellets.

Jan 1, 1974

By Arthur Boynton

IN THE preparation of this paper the writer has been influenced by the fact that descriptions of various means of cleaning blast-furnace gas have been published and that further descriptive treatment of the subject will probably be less interesting than a statement of conclusions with regard to preferable methods which have been reached by him as a result, of experience and observation in this country and also as a result of somewhat detailed investigation of the subject made toward the end of the year 1927 on the Continent of Europe and particularly in. Germany. Owing to various circumstances, including a cost of fuel that is extremely high in relation to the wages of labor, the German iron and steel industry has accumulated experience in gas washing which is as yet in part lacking in the United States of America. The paper begins with a statement regarding the economics of the use of blast-furnace gas, then considers the principle's and practices employed in its purification. USES OF BLAST-FURNACE GAS For many reasons having to do with the utilization of coke-oven and blast-furnace gases in steel manufacture and with the use of hot metal, the blast furnace is now usually a part of a steel-producing unit, which also includes coke plant and rolling mill. Therefore both blast-furnace and coke-oven gas are usually applicable to any of the iron and steel-making processes, including the generation of power, and their allocation in any given works should be considered as a single problem. The uses to which blast-furnace gas, either alone or mixed with coke-oven gas may be put, include the following: Regenerative Heating of Air for the Blast Furnace.-This is the oldest and metallurgically the most important of all uses. It is universally performed with unmixed blast-furnace gas and under proper conditions should require not over 23.5 per cent. of the total gas generated for a blast temperature of 1350° F. For Steam-raising Purposes.-This is almost universally done with unmixed blast-furnace gas. From the standpoint of quantity used, it is at the present time the most important application in American steel-works practice.

Jan 1, 1928

By S. A. Falconer

One of the outstanding achievements in connection with this country's war efforts has been the ability of our mining industry to supply from domestic sources many of the minerals of strategic importance that formerly were obtained principally from abroad. In order to meet the war-born demands for these scarce minerals, it has frequently been necessary to develop special methods for treating ores and waste products hitherto considered too lowgrade to be workable; and to improve the efficiency of older beneficiation processes. Important in this respect have been the recent technological advances in the field of froth flotation of nonsulphide minerals. Because of the refractory nature of many of these domestic ores, and, in many cases, the limited available technical data regarding their treatment, much research work has been necessary. The following examples describe the procedures and reagents used, and the results obtained, in certain laboratory flotation investigations conducted by American Cyanamid Company's engineers at the Cyanamid Ore Dressing Laboratory on ores containing such minerals as scheelite, manganese oxides and carbonate, ilmen-ite, brookite, kyanite, garnet, spodumene, mica, feldspar, celestite, fluorite, chromite, corundum, and cassiterite. In presenting these data, we wish to point out that many of the minerals listed have previously been tested, and their amenability to flotation reported, by other investigators—notably those of the United States Bureau of Mines. In some instances the procedures and reagents used in the treatment of some of the following described ores follow rather well-established lines, and with one or two exceptions, the reagents used were well known. However, many of the ores tested did not respond well to simple conventional procedures and it was necessary to adopt special methods of conditioning and desliming, reversal of the usual order of floatability of some of the minerals, multiple cleaning, etc., in order to secure separations. Except where otherwise noted, all numbered and trade-marked reagents mentioned in this paper are marketed by the American Cyanamid Co. or the American Cyanamid and Chemical Corporation. Tungsten ORes Tungsten minerals, vitally important in the war industries of the United States, rank high in the list of those we formerly had to import in order to supply our needs. Most of our domestic ores of tungsten contain scheelite as the valuable mineral. Today there are in the neighborhood of twelve tungsten operations in this country where flotation is used as the main or accessory form of benefication. It has, of Course, been known for some time that scheelite and other tungsten minerals respond to treatment by flotation.

Jan 1, 1947