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By V. E. Christensen

AT most smelting plants, forced draft, induced by high stacks or fans, is used to carry the gases away from the furnaces, roasters, or sintering plants. Gases moving under forced draft carry varying amounts of solids in the form of dust and fume. Where the weight of the solids is material, and the metal content high, it is usually profitable to treat the gases to recover these solids. Baghouses, Cottrell treaters, and settling chambers are the common forms of plants used to recover solids from gases. To check on the efficiency of these plants it is necessary to know the volume of gas leaving the plant and the amount of solids carried by the gas. As the volume of gas is equal to the product of the velocity of that gas and the cross-sectional area of the flue, the determination of the volume includes the measurement of the area of the cross section and the determination of the velocity. The velocity is generally measured by means of the Pitot tube and Ellison differential pressure gage, although low velocities are best determined by means of an anemometer. The dust concentration is determined by passing a measured volume of sample through a filter and weighing the dust caught. From this the dust concentration per unit of volume may be calculated. It is necessary to assume that the gas is homogeneous or that each cubic foot of the gas contains the same weight of dust as every other cubic foot. Having the volume of gas passing through a flue per unit of time, and the dust concentration of the gas per unit of volume, the amount of solids may easily be calculated.

Jan 1, 1935

By AIME AIME

THOUGH the dust-control systems in the crushing plants and other buildings at Morenci do not differ materially from similar installations in other large copper reduction works, it is probable that in few other plants has as much attention been paid to the dust problem. Possibly the most striking feature of the Morenci installation is the manner in which the necessary equipment has been built into the various structures, and the absence of unsightly pipes, ducts, and fan houses. That this result has been attained is due, in no small part, to the basic conception that the control of the dust in a milling plant should be an essential part of the process itself and not something to be tacked on later after the plant is in operation. The control systems were designed and developed along with the general plant construction program and when the first car of ore was dumped into the crusher the dust-control equipment was ready.

Jan 1, 1942

By CHRIS A. HARTNAGEL

For the second consecutive year, the production of crude petroleum in New York has fallen below the 5,000,000-bbl. Mark that had prevailed previously since 1937. In 1945, the output totaled 4,658,000 bbl., a decrease of slightly more, than one per cent from the 1944 production. This total represents 2 per cent of the stripper-well production of the United States, which in turn is I 3 per cent of the total annual yield of the nation's petroleum.

Jan 1, 1946

By Allen V. Heyl

This old district is a major zinc and lead source and minor copper and barite source. Ores are chiefly in the Galena Dolomite and in limestones and dolomites of the Decorah and Platteville Formations, all of Middle Ordovician age. Locally, deposits have been mined from Lower Ordovician dolomites and Upper Cambrian sandstones. Small deposits of lead, zinc, and iron sulfides have been found in Upper Ordovician Maquoketa Shale and in Lower and Middle Silurian Edgewood, Kankakee, and Hopkinton Formations. No post-Precambrian igneous rocks are known in the region, and the granitic and metasedimentary Precambrian basement rocks unconformably underlie the district at depths of 1500 to 2000 feet. The strata are gently flexed and faulted, probably largely the result of gentle compressive and rotational adjustments in the underlying crystalline basement, especially along lineaments between basement blocks. Folds of three orders ·of magnitude are recognized, and many related reverse, strike-slip, and normal faults of small to moderate displacements are present. Zinc-lead deposits are commonly linear, arcuate, or elliptical in plan. Most ore occurs as vein fillings in fractures and as breccia fillings and lining vugs, but some is in bedded replacements and impregnations of wall rocks. The ore is in shears, small reverse and bedding- plant faults, joints, and solution-slump structures related to intermediate and small folds. The main primary minerals in their general sequence of deposition are quartz, illite, dolomite, pyrite, marcasite, cobaltite(?), sphalerite, galena, chalcopyrite, millerite, barite, and calcite. Wall-rock alterations include solution of the carbonate rocks, silicification, dolomitization, clay alteration, and sanded dolomite. Oxygenisotope, trace-element, lead-isotope, and sphalerite- stratigraphy studies are in progress. Fluid inclusions in sulfide and gangue minerals are filled with concentrated brines at 120° to 40°C. Sulfides are directly replaced by supergene minerals above the water table at 50 to 100 feet in depth. In this relatively cool climate and limestone environment, smithsonite is in pseudomorphs after sphalerite; solution transport and redeposition of supergene minerals are rare. Ore genesis is postulated by rising hot-water solutions-a mixture of heated connate, magmatic, and meteoric waters.

Jan 1, 1968

By C. van der Poel, R. L. Chuoke P. van Meurs

When an initially planar interface between two im-ttitcihle liquids is displaced at constant rate, U, nor-mat to the front, instability will occur for all rates greater than a critical rate. U, given by provided the Fourier decomposition of the spatial pertmrbcrtiott or deformation of the moving displacetment front contains modes with wavelengths. A, greater than a critical wavelength, given by tit there expressions, p, p and k, with the subscripts I and 2 distinguishing the two 1iquids under consideration, are density, viscosity and effective pemeability coefficients respectively; g is the absolute value of the acceleration due to gravity; and cos (zz') is the direction cosit7e between the vertical carlesian coordinate z' (positive upward) and the z coordinate norma1 to the initially plane macroscopic interface taken positive in the direction from Liquid I to Liquid 2. U is the average volumetric velocity (injected volume of liquid pet. unit time per unit of area normal to Z) and is positive for Liquid I displacing Liquid 2, negative for the reversc displacement and r2 is an effective inter-fucial tension (for displacements between parrallel plates, t0= s the ordinary bulk interfacial tension). further, there is a wavelength of maximum instability given by For natural perturbations, this wavelength will preclotninate and characterize the form of the instability as a quasi-sinusoidal deformation, i.e., viscous fitzgers of peak-to-peak separatiotr, A,,. Comparison of experitient with theory rei'eals tltat these considerations are recsonably valid for displacements in hoth parallel plate chantzels and nnconsoli-clutt'd glass ptnvder packs. These results are. tij particular interest for interpretation of data from laboratory experiments with regard to fielil applica/iotz.s. It is quite possible for A,, although st7zall relative to the large lateral dimension of the reservoir, to rxceed the greatr.st lateral extent of the lahoratory sample or model. If it does, frontal displace- ment occurs in the laboratory experiments, and oil INTRODUCTION Thc puposes of this paper are to present theoretical and experimental evidence for occurrence of macroscopic instabilities in displacement of one viscous fluid by another immiscible with it through a uniform porous medium and to compare available experimental data with some predictions of a theory of instability developed by the first author. The instabilities are referred to as macroscopic in the sense that spatially quasi-sinusoidal, growing fingers of the displacing liquid are formed, the width and peak-to-peak separation (wavelength) of which is large relative to a characteristic length of the particular permeable medium such as grain size. Visual models of two kinds have been used to obtain observations: displacement of oil by water-glycerine solutions through the flow channel formed by closely spaced parallel plates and displacement of oil by water with and without initial interstitial water through unconsolidated glass powder packs, employing the technique of matching indices of refraction. In all cases we have observed macroscopic instabilities or fingers under conditions predicted by the theory to be favorable for their occurrence. The phenomenon discussed here is not the production of streamers due to gross inhomogeneities such as permeability stratification of the porous medium. It is our object to show, on the contrary, that a quantitative prediction of finger spacing is possible in a porous medium known to be macroscopically homogeneous and isotropic throughout. The importance of the phenomenon in its influence on the configuration of oil and water with respect to oil production behavior was noted earlier by Engel-berts and Klinkenberg' who coined the term "viscous fingering". THEORY Necessary and Sufficient Conditions ior Instability anc Initial Kinematics There are several levels of increasing complexity in the theoretical description of instabiIity of fluid displacements in permeable media. Of these, the simplest description, ;tdapted to low permeability systems, is selected for presentation.' More inclusivc tlescriptions are reserved for separate publication.

By J. A. Burkhardt

Field measurements and theoretical studies have been made of pressure surges—momentary variations in fluid pressure—produced by movement of pipe in mud-filled boreholes. Pressure measurements were recorded by five pressure gauges located at various positions in the borehole. An important positive pressure peak was found to occur as the casing moved with maximum velocity. Important negative peaks were found as the casing was lifted from the slips and as brakes were applied to stop pipe movement. A rigorously formulated theory has successfully predicted the sequence and magnitudes of these positive and negative surges and has established a basis for understanding how they occur. Both the measurements and theory indicate that the most important pressure surge is usually due to viscous drag of the flowing mud. The theory of viscous-drag pressure surges has been approximated by simplified graphs and calculation procedures to facilitate ready use in field operations. Comparison of measured results with those predicted by the simplified theory shows that the magnitude of this surge can be predicted accurately. INTRODUCTION It is widely recognized that raising or lowering pipe in a fluid-filled borehole produces momentary variations in fluid pressure, commonly called pressure surges. Both negative (or "swabbing") surges and positive (or "fracturing") surges may occur. In 1934, Cannon1 measured the negative surges and showed that they could be large enough to cause flow of formation fluids into the well-bore and, in extreme cases, lead to blowout conditions. Later, Coins2 measured the positive surges associated with lowering pipe. His results and subsequent field operations strikingly demonstrated that pressure surges could be an important factor in some cases of lost returns. In addition, although the evidence is less clear than in the case of blowouts and lost returns, other investigators 3, 4 feel that pressure surges probably play a part in many instances of minor gas cutting, salt-water flow and other hole trouble. The importance of pressure surges in drilling operations led naturally to attempts to explain the physical causes, nature and magnitude of the surges. Cardwell5 was the first to publish a theory which allowed the quantitative prediction of momentary pressure variations. He assumed that the drilling fluid was a 300-cp Newtonian fluid in turbulent flow. Most field muds have a considerably lower viscosity and are generally believed to be Bingham plastic in nature.6 However, card-well's results were useful because they were presented in a form convenient for field use and, in some cases, gave a reasonably accurate predicted value for the maximum pressure surge. Subsequently, Ormsby7 published a more comprehensive theory of pressure surges. He discussed both laminar and turbulent flow and considered the theory of mud-bypass devices for reducing pressure surges. As a consequence of his more rigorous approach, his results were more accurate but more complex and difficult to use. Further, both Ormsby and Cardwell considered only the pressure surge arising from viscous drag of the moving mud. Clark later published idealized graphs of surges and presented equations for predicting their magnitudes. In addition to pressure variations arising from viscous drag, he considered those caused by inertial effects. His theory was in this respect more complete than those of Cardwell and Ormsby, although he did not discuss pressures due to breaking of the gel. Furthermore, his equations, while not exceptionally complicated, were too complex for ready use at a drilling location. One difficulty common to all three theories is that none was tested rigorously by direct comparison with measured pressure surges. Their accuracy, therefore, could, not be demonstrated. Further, the two theories based on most realistic assumptions (Ormsby and Clark) required the solution of one or more rather complex algebraic equations. The research described in this paper was undertaken to supplement that described and to overcome some of the difficulties noted. It seemed obvious that a fully satisfactory study of pressure surges should encompass three main phases. 1. A valid theory useful in all field situations must be developed. This theory must be based upon realistic assumptions, must be formulated rigorously and should lead to clear concepts whereby the nature of pressure surges can be easily understood. 2. The theory, however complex and involved, ultimately must be presented in simplified form for convenient field use. This may involve extensive machine computations and the use of figures and empirical equations. 3. The accuracy of the simplified equations must be established by comparing measured pressure surges with those predicted by the theory. These must agree both in their characteristic nature and in magnitude. 'This means that careful measurements of surges occurring in actual field operations must be made.

By ALEC CROWELL

This brief summary of oil and gas developments in Alabama, Florida and Georgia has been made possible through the courtesy of Stewart J. Lloyd, Assistant State Geologist of Alabama; Herman Gunter, Director, Florida Geological Survey, and Garland Peyton, Director, Georgia Department of Mines, Mining and Geology.

Jan 1, 1946

By Russell A. Carter

Alaska is a land of immense proportions and resources. Its very name, derived from an Aleut term, means "The Great Land." Yet, in a state slightly larger than Texas, California, and Montana combined, there are presently only two-large scale mines in production, excluding dredge operations. Once referred to by its territorial governor as "a storehouse of minerals," Alaska is, in the opinion of many industry observers, at least 20 years away from a healthy, productive mining industry. The mineral potential of the state is tremendous: coal deposits on the North Slope alone have been hypothetically pegged at 1.5 trillion tons. Copper-zinc deposits on the south flank of the Brooks Range are conservatively estimated to be worth $4 billion to $6 billion. However, the problems facing mineral development are of equal magnitude, and include:

Jan 11, 1976

By J. W. Ristori, V. R. Garfias

ONE of the most serious problems now confronting Gel- many-and one that will affect Italy even more seriously if she goes to war against England and France -is that of supplying her navy, mechanized army, and air force as well as her industrial and other needs with the necessary and related products. This problem, serious even now, will become vital should hostilities on a large scale develop.

Jan 1, 1939

HAVING taught you to make aqua fortis and to cleanse and reduce it to perfection, before I teach you the work of parting on a large scale, I wish now to teach you how to make an assay of the amount of gold present in a quantity of silver, so that you may proceed to your work with open eyes in order to become aware of mistakes when you have erred yourself or have been deceived by someone else. Therefore it is necessary to know very exactly, before you take it out, how much gold should be in your cucurbits from the weight of the silver that you put in. Thus you may see the gain or loss, if you had to deliver it to someone else or if you had bought it. If you did not do this you would proceed blindly in your work.

Jan 1, 1942

By AIME AIME

A PAPER recently presented before the Anthracite Section of the A. I. M. E. by S. J. Phil- lips, Mine Inspector, Fifth Anthracite District, Department of Mines of Pennsylvania, covering the water hazards in the anthracite coal mines of the Lackawanna River Valley, was especially timely because the conditions there are duplicated to a large extent in the Wyoming Valley, which is traversed by the Susquehanna River with its many large tributary streams. Also, in the southern anthracite field, where there are a number of large creeks, similar pumping problems and mine water hazards will in time be presented if mining is continued to its conclusion.

Jan 1, 1936

By W. C. PAGE

ALL mine ore here must be concentrated before shipment, which involves selective flotation. Three products are made: lead, zinc, and pyrite concentrates. The equipment and practice are so well outlined in the accompanying flow sheet that only a few amplifying remarks are necessary. After crushing at the mine to approximately 4 in., the ore is carried by aerial tram about 4 1/2, mi. to the mill. From 1800 to 2000 metric tons per day, excluding Sundays, is thus transported. At the mill, the buckets are hand-tipped into the bins. After crushing to pass a ¼ -in. square opening, the ore may be stored in reserve crushed-ore bins or ball-mill feed bins as desired. Total bin capacity at the mill is about 4000 metric tons. The concentrator is arranged in three independent grinding sections, each fed from its own storage bin. Grinding operations follow standard practice, with ball mills in single-stage closed circuit with classifiers, the overflow from which is delivered to the lead circuit rougher flotation machines,

Jan 1, 1936

By PERCY E. BARBOUR

SECONDARY copper1 has &come more or less of a bugbear generally. What is its influence is often the subject of heated argument. The inedapable fact usually quoted is that since in 1929 primary production of copper in the United States was 1,026,348 tons and secondary production was 626,550 tons, there- fore, 0.6 lb. of secondary is produced for every pound of primary, and "How can you get around that?" The matter seems very plain, now that I have reached my conclusions, but they are the result of much laborious study and research. I shall show that' the production of secondary copper is not 0.6 per lb. of primary, in spite of statistical appearances; that the production of secondary is a function of primary production rather than of price; that secondary production has 'only a sub-. ordinate influence on the price of copper and then only in abnormal times; that there is not an accumulating reservoir of secondary from which the country is some- time to be drowned in copper, as is believed by some, or a reservoir from which we are going to draw much needed and more or less inexhaustible stores in the future, as is believed by others; and finally, that the United States always produces more copper than it uses and exports the surplus. These are all controversial points, and for that reason and to anticipate argument I have set forth my reasoning in considerable detail.

Jan 1, 1931

By T. F. Witheree

The Fletcherville Furnace was built in 1864 and 1865, making its first blast from August until October of the latter year, when it was blown out to prevent its " bunging-up." Repairs were made in time to enable it to be blown in again December 12th, 1865, the blast ending October 7th, 1866. Total product 1921.15 tons iron, an average of 6.8.2.5 tons per day, from ores yielding 44.8 per cent. Consumption of charcoal 223.2 bushels per ton of iron. The furnace journal up to this time shows no record of furnace dimensions, or temperature of the blast, but as near as can be ascertained, they were as follows, viz.: Height of stack, 42 feet. Diameter of bosh, 11 feet. Angle of bosh, 71/2 inches to 12 inches rise, about 58°. Diameter of open tunnel head, 42 inches. Number of tuyeres 3 ; each 3 inches in diameter. Dam 15 inches high. Tuyeres 24 inches high. Tymp 224 inches high. Diameter of steam cylinder, 20) inches. } Diameter of blast cylinder, 64 inches. } Stroke 5 feet. The engine is direct-acting horizontal non-condensing. December 26th, 1866, the furnace was again put in blast, having been considerably altered in the crucible; the height of stack, bosh, and tunnel head remaining as before. Six tuyeres were put in, three in each of the side arches. The hearth or crucible was rectangular in form, 3 feet wide x 31/2 feet long x 64 feet high. Inclination of bosh 58°. Height of tuyeres 26 inches; nozzles 21/4 inches diameter. Temperature of blast estimated to be about 500°.

By Jerome F. Kuzmick

The use of iron powder during the postwar conversion period has been increasing with great rapidity. This is particularly true in regard to the manufacture of molded mechanical parts such as bushings, gears, cams, small wheels, and the like. Many manufacturers have found it possible to replace machined cast iron and carbon steel with molded iron powder parts, and thereby can not only effect a savings in cost, but can produce a better product as well. As the field of application for iron powder parts widens, greater demands are made upon the powder supplier concerning quality and uniformity characteristics. The following are some of the most important properties parts fabricators desire in the iron powder they use: 1. The powder should have high compressibility so that good density can be obtained without the use of excessive pressures. At the same time, it should show low die wear so that a large number of pieces can be produced from the die. This means that the powder must be of high purity and good softness or plasticity. 2. The powder should produce compacts of high green strength, so that unsintered parts can be handled without breakage or fraying of the edges. 3. The sintering properties should be good so that satisfactory strength is obtained in the sintered piece. 4. Compacts made from the powder should show small but, above all, uniform dimensional changes during the sintering operation so that accurate parts can be produced, and warping and other such bad effects eliminated. 5. The powder should have satisfactory flow properties for automatic molding. 6. It is very important that the powder be uniform in sieve analysis, compressibility, flow, purity, and other qualities, from container to container in any given lot and from shipment to shipment. 7. Price—The fabricators desire all these good properties, but in many instances still do not wish to pay a premium price. There has been considerable discussion as to the importance of price of the powder in relation to the cost of the finished product. It is true that in cases where certain special properties only procured by powder metallurgy are required, price is not a criterion. On the other hand, there have been a number of applications recently made which would not be commercially practical with a powder which commands a premium in price. Iron powder parts are compressed in automatic presses to definite size, shape, and density. The powder is compressed to a density figure dependent upon the function the part is to perform, as well as upon such important considerations as press capacity and die wear. Such parts can be roughly broken down into the following density ranges:

Jan 1, 1949

By A. L. Holley

THIS process is performed in the Pernot puddling furnace; it removes from 75 to 80 per cent. of the phosphorus, most of the sulphur, and practically all the silicon, from crude iron, in from five to eight minutes. It has been in regular use since March, 1877, and has prod uced over seventeen thousand tons of washed metal for the open-hearth furnace. During two years, nearly all, and lately, all the open-hearth steel produced in these works has been made from about 5 tons of washed pig and 2 tons of scrap per open-hearth furnace heat. There are 12 open-hearth furnaces, of which 4 to 9 are running, according to the state of orders. A large amount of highly phosphoric iron from France and Belgium has been also washed and then puddled for parties who have taken, or are expected to take, licenses. The washing of pig for puddling, however, is not a practice at Krupp's works, because pure pigs are nearly as cheap as impure ones. The author and his assistant, Mr. Laureau, spent, during the last month, three days at Krupp's works, examining this process. They copied out of the office books characteristic analyses and physical tests, some of which are given herewith. They also brought hone many samples of pig, cleaned metal, puddle bar, and steel, which they saw treated. Analyses of some of these samples appear in Table IV. As there are no blast furnaces at Essen, the iron is melted in two Bessemer cupolas with fore-hearths; they melt 12g pounds of iron with 1 pound of coke. The metal is run by a spout from the fore-hearth into an opening at the side of the main door of the washing-furnace. The Washing furnace.-This is a regenerative gas furnace. It has a Pernot revolving-hearth of 12 feet external diameter and 3 feet depth. (See Plate.) The four regenerator chambers have 780 cubic feet capacity, which is about the same as the average regenerator capacity of open-hearth steel furnaces of equal tonnage. The lining is 13 inches thick on the sides and 9 inches on the bottom, thus giving a hearth 9 feet 10 inches by 2 feet 3 inches deep. The lining is composed of lumps of highly refractory ores

Jan 1, 1880

By A. L. Holley

This process is performed in the Pernot puddling furnace; it removes from 75 to 80 pel. cent. of the phosphorus, most of the sulphur, and practically all the silicon, from crude iron, in from five to eight minutes. It has been in regular use since March, 1877, and has produced over seventeen thousand tons of mashed metal for the openhearth furnace. During two years, nearly all, and lately, all the open-hearth steel produced in these works has been made from about 5 tons of washed pig and 2 tons of scrap per open-hearth furnace heat. There arc 12 open-hearth furnaces, of which 4 to 9 are running, according to the state of orders. A large amount of highly phosphoric iron from France and Belgium has been also washed and then puddled for parties who have taken, or are expected to take, licenses. The mashing of pig for puddling, however, is not a practice at Krupp's works, because pore pigs are nearly as cheap as impure ones. The author and his assistant, Mr. Laureau, spent, during the last month, three days at Krupp's works, examining this process. They copied out of the office books characteristic analyses and physical tests, some of which are given berewith. They also brought home many samples of pig, cleaned metal, puddle bar, and steel, which they saw treated. Analyses of some of these samples appear in Table IV. As there are no blast furnaces at Essen, the iron is melted in two Bessemer cupolas with fore-hearths; they melt 124 pounds of iron with 1 pound of coke. The metal is run by a spout from the forehearth into an opening at the side of the main door of the washingfurnace. The The washing-furnace.—This is a regenerative gas furnace. It has a Pernot revolving-hearth of 12 feet external diameter and 3 feet depth. (See Plate.) The four regenerator chambers hare 780 cubic feet capacity, which is about the same as the average regenerator capacity of open-hearth steel furnaces of equal tonnage. The lining is 13 inches thick on the sides and 9 inches on the bottom, thus giving a hearth 9 feet 10 inches by 2 feet 3 inches deep. The lining is composed of lumps of highly refractory ores

Jan 1, 1880

By Wm. A. Haven

ON the northern part of the globe, almost since the earliest days of mankind's history. ironmaking has been practiced in one form or another. Some investigators question the generally accepted belief that copper and bronze were in earlier general use than iron, explaining the greater age and abundance of copper relics by their greater resistance to natural oxidation. However, the occurrence of copper in its natural state and its greater ease of reduction from the simpler copper minerals is a strong argument that the making and use of copper came first. Nevertheless, good evidence exists that ironmaking was practiced in ancient India and China, as well as in ancient European countries. Some interesting vestiges of those early operations still survive and have a place, in the background at least, of a discussion of modern blast-furnace practice.

Jan 1, 1940

By Jerome F. Kuzmick

INTRODUCTION THE use of iron powder during the post-war conversion period has been increasing with great rapidity. This is particularly true in regard to the manufacture of molded mechanical parts such as bushings, gears, cams, small wheels, and the like. Many manufacturers have found it possible to replace machined cast iron and carbon steel with molded iron powder parts, and thereby can not only effect a savings in cost, but can produce a better product as well. As the field of application for iron powder parts widens, greater demands are made upon the powder supplier concerning quality and uniformity characteristics. The following are some of the most important properties parts fabricators desire in the iron powder they use: I. The powder should have high compressibility so that good density can be obtained without the use of excessive pressures. At the same time, it should show low die wear so that a large number of pieces can be produced from the die. This means that the powder must be of high purity and good softness or plasticity. 2. The powder should produce compacts of high green strength, so that unsintered parts can be handled without breakage or fraying of the edges. 3. The sintering properties should be good so that satisfactory strength is obtained in the sintered piece. 4. Compacts made from the powder should show small but, above all, uniform dimensional changes during the sintering operation so that accurate parts can be produced, and warping and other such bad effects eliminated. 5. The powder should have satisfactory flow properties for automatic molding. 6. It is very important that the powder be uniform in sieve analysis, compressibility, flow, purity, and other qualities, from container to container in any given lot and from shipment to shipment. 7. Price-The fabricators desire all these good properties, but in many instances still do not wish to pay a premium price. There has been considerable discussion as to the importance of price of the powder in relation to the cost of the finished product. It is true that in cases where certain special properties only procured by powder metallurgy are required, price is not a criterion. On the other hand, there have been a number of applications recently made which would not be commercially practical with a powder which commands a premium in price. Iron powder parts are compressed in automatic presses to definite size, shape, and density. The powder is compressed to a density figure dependent upon the function the part is to perform, as well as upon such important considerations as press capacity and die wear. Such parts can be roughly broken down into the following density ranges:

Jan 1, 1948

By M. C. Fuerstenau, R. B. Bhappu

The response of beryl to sulfonate flotation was examined. The dependence of flotation recovery on sulfonate concentration, pH, and the absence or presence of various ions is also demonstrated. The response of quartz and feldspar to sulfonate flotation at various values of pH is given to. show the conditions necessary for selective separation. Finally, beryl was successfully concentrated from a natural ore using a technique devised from experimental observations on systems of pure minerals. With the possible exception of quartz, the flotation characteristics of silicate minerals are rather poorly understood. This is due in part to the com- plexity of the mineral systems themselves and in part to an insufficient amount of flotation data. The complexity of the systems arises from the wide range of chemical composition that the silicate minerals can assume. This is reflected in the variability of such physical properties as hardness and cleavage. Although the chemical composition of silicate minerals can vary considerably, a general grouping can be accomplished conveniently on the basis of the assemblage of SiO4 tetrahedra in all the silicates. That is, it has been shown that six basic groups can be obtained, depending on the arrangement of oxygen sharing between adjacent silicon atoms (or substituted aluminum). When all four oxygen atoms are shared, a framework structure such as quartz or feldspar is obtained. When three oxygens are shared, infinite sheets are obtained as in the micas and clays. When two oxygen atoms of the tetrahedra are shared, infinite chains are obtained, such as those in

Jan 1, 1963