Search Documents

By Robert I. Jaffee, Walter L. Finlay

IN the broad survey of the nonferrous' metallic elements contained in this book, the reader may well be impressed by the wide range of property combinations offered by the many metals and alloys the metallurgist has prepared since before Kubla Khan. The diversity is great and the overlap is considerable. It is particularly surprising, then, to find the latest structural metal new- comer designated by such extravagant terms as "Cinderella Metal," "Wonder Metal," "Miracle Metal," "The Metal of Tomorrow," "Dream Metal or Nightmare?" and "The Middleweight Champion of the Structural Metals." Of these and others, the most appropriate designation for the metal involved, titanium, appears to be that of The Middleweight Champion. Its intermediate density of 4.5 and elastic modulus of 16 million is a unique combination between the lower density and modulus of magnesium and aluminum and the higher density and modulus of copper, nickel, and iron. It is light, strong, ductile, and corrosion resistant. A chemical neighbor in group IV of the Periodic Table, zirconium, is similar to titanium in many respects but is appreciably denser, 6.5 instead of 4.5, less stiff and relatively much less abundant. On the other hand, the resistance of zirconium to acids and alkalies is better than that of titanium. Also, compensating for its higher density, lower stiffness, and somewhat lower strength level compared with titanium, zirconium has much better permeability to slow neutrons and is much more suitable as a material of construction for nuclear reactors.

Jan 1, 1953

By S. Edward Drummond, Charles D. Haynes, Stephen H. Stow

This paper is a preliminary report on the occurrence and distribution of economically interesting heavy minerals (kyanite, sillimanite, staurolite, zircon, monazite, ilmenite, leucoxene, rutile) in sands from the sea floor surface of the offshore area, Alabama-Mississippi. Weight percent of heavies derived from the +60 portion of 97 samples is contoured in [Fig. 1]. Five hundred grains from 42 of the heavy mineral separates were identified and sized microscopically; the data were converted to weight percent for each mineral species and are summarized in [Table 1]. Heavy Mineral Distribution In the Gulf, there is a general westward decrease [(Fig. 1)] in maximum abundance of heavies from 2.4% north of Sand Island at the mouth of Mobile Bay to slightly over 1.0% south of Petit Bois Island and a corresponding decrease in the Mississippi Sound from 1.4%, north of Dauphin Island to slightly over 0.25% north of Horn Island. Average concentrations of heavies for different areas are found in Table 1. There is westerly longshore transport in this area; the interaction of the longshore current with discharge from Mobile Bay and disruptions of the current by Sand Island, possibly aided by a shoaling effect, appear to be the cause of the preferential deposition and concentration of heavies (2.4%) north of Sand Island in 10 to 14 ft of water.

Jan 1, 1977

By R. E. McNulty, R. D. Heidenreich, C. H. Gerould

TIIE electron microscope techniques and their application to magnesium alloys that are to be discussed in this paper are the result of research at The Dow Chemical Co. over the past three years. The view- point underlying the work is not wholly metallurgical, but has evolved through a variety of problems related to the physics and chemistry of surfaces. It can be said that the interest and stimulus were closely associated with a desire to employ effectively the electron microscope in research concerning the properties of solids as related to their physical structure. Only a portion of this work will be described here, and, consequently, many points of interest and debate are of necessity either only briefly recognized or are completely omitted. As has been pointed out by Desch,1 a great deal of the knowledge of the structure of metals has been obtained through microscopic studies of the surfaces of metallic specimens prepared in a particular manner. This information, when added to that obtained by means of thermal, electrical, X-ray, dilatometric and other methods, has been of great value both from a theoretical and a practical view- point. With the introduction of new instruments such as the electron diffraction camera and the electron microscope, it would be expected that still more information could be obtained. These two instruments have in many instances been very effective when directed toward the investigation of metallic surfaces, provided the proper methods of surface preparation were employed. Experience shows that the problems of surface preparation greatly limit the general application of these instruments to metallographic studies. It was found necessary to discard the standard metallographic procedures in applying the electron microscope to magnesium alloys and to work out new methods, which were required to satisfy certain conditions. These methods are unique to magnesium only in the specific chemical reactions occurring during etching. The presentation of the methods and results will be ordered as follows: I. Electron Microscopy of Surfaces. 2. Surface Preparation of Magnesium Alloys. 3. Discussion of Microstructures. a. Pure Magnesium and Single-crystal Studies. b. Types of Precipitation. c. Some Common Structures. d. Special Micrographs and Techniques. e. Structure of Mg-A1 Solid Solutions. 4. Correlation of "Fine Structure" with Corrosion Behavior of Magnesium Alloys.

Jan 1, 1946

By C. A. Stewart

PAGE. I. Introduction............ 241 II. Location. TopoGRaphy. and History....... 243 III. DescRiption of the Rocks......... 245 1. Altered Sediments.......... 245 2. Alaskite........... 246 3. Alaskite.Porphyry.....255 4. Quartz Dikes........... 257 5. Biotite.Granite.......... 256 6. Quartz.Porphyryl......... 260 7. Andesite........... 262 8. Miscellaneous Dikes......... 263 IV. Age oF the Rocks and Comparison with other Localities.. 263 V. AlteRation............ 265 1. Sericitization........... 265 2. Silicification........... 266 VI. StRuctuRes........267 1. Dip of the Limestone......... 267 2. Faulting........... 267 VII. Contact - metamorhism,.......... 269 1. Endomorphism.......... 269 2. Exomorphism......... 271 Recrystallization and Loss of Color...... 271 New ,Minerals.......... 272 Addition of Material........ 274 Volume.Changes.... 276 Locus of Metamorhism........ 277 Method of Precipitation.........278 VIII. ORe-Deposits............ 278 1. Contact-Metamorphic Copper.Ores,..... 279 General..........279 Shape and Distribution........ 279 Minerals........... 281 Secondary Enrichment........ 282 2. Disseminated Copper.Ores........ 283 3. Origin of the Copper.Orcs........ 284 4. Lead-Silver Ores.......... 287 IX. Bibliography............ 288

Jan 1, 1913

By W. L. Honnold

Owing to a unique labor situation and other unusual circumstances, the mining methods of the Rand are hardly comparable with practice elsewhere. They are of considerable interest, however, and their importance is increased by the magnitude of the' industry with which they are identified, gold of $166,186,000 value, say 40 per cent. of the world's production, having been recovered from 25,701,954 tons of ore milled in 1914. In the sketchy remarks to follow, attention will first be drawn to some influential factors of general bearing, after which certain features at two mines of the writer's group will be referred to. It is hoped that engineers associated with similar or different conditions and practice will contribute to broaden the discussion. Before proceeding, recognition is due the generous assistance of C. E. Knecht and F. A. Unger. General Observations The principal mines are situated along the northern limit of an irregularly shaped geological basin, and extend in almost unbroken continuity over a distance of about 60 miles. As the boundaries are defined by vertical planes there are both "outcrop" and "deep-level" properties, all differing in size and in technical features. So much has been written in regard to the geology of the Rand that only a few pertinent features need here be recalled. Briefly, the ore deposits are profitably enriched portions of certain conglomerate beds or "reefs," rarely more than three, which are interposed between quartzite, or quartzite and slate, and lie so closely together that where more than one are mined they are dealt with as a working unit, although they may be stoped separately. Their collective extension is locally referred to as " the Reef." Along the outcrop the series dips more or less steeply, and in depth it flattehs, the latter tendency being most marked in the Far East Rand, where the bottom of the basin is nowhere so deep as to be inaccessible. Dikes and faults are a common feature throughout. They are,

Jan 1, 1916

By H. L. Talbot, R. S. Young, A. Golledge

The differentiation of oxidized forms of lead from lead sulphide in complex products by chemical analysis is of considerable importance to certain mining and metallurgical companies. A method for the separation of "oxide" lead, (non-sulphide), from sulphide lead, based on the solubility of the former and virtual insolubility of the latter in concentrated ammonium acetate solution, has been employed for many years in the industry.1,2 Unfortunately this solvent, while satisfactory for lead sulphate and carbonate, is without action on lead phosphates or vanadates, with the result that at .Rhodesia Broken Hill Development Co. where these latter minerals are present, they have counted as sulphides when using this procedure. For the control of operations in the new concentrator it became necessary to have a closer check on sulphide lead than could be obtained by the only current method of differentiating this constituent from oxidized lead. For some time this problem has engaged our attention, and after a large number of solvents had been tried, the following procedure was evolved. Like all methods depending on selective solution in a com- plex material, it will not give 100 pct separation into oxide and sulphide portions. Because of the ease of oxidation of galena this is almost an impossibility. Our procedure will, however, give a recovery of 99-100 pct of the oxidized lead, contaminated with very small quantities of lead sulphide, and a corresponding recovery of 97-98 pct of the sulphide lead. The procedure is simple and reproducible, and gives results quite .satisfactory for routine control purposes. Experimental For this work standard samples of the following pure lead minerals were obtained from Broken Hill, Northern Rhodesia. These were hand-picked specimens, and were carefully ground to —200 mesh. Since it was realized that a fair-sized sample would be necessary for this work to thoroughly test the large number of procedures we had in mind, a compromise had to be effected between a few grams of very pure minerals and a large sample of lower grade material. For this work the presence of gangue was not deleterious, so long as the oxide lead minerals did not contain lead sulphide, and vice versa. Table I shows the lead minerals used, and their total lead content, both theoretical and actual. Apart from the pyro-morphite the minerals are seen by analysis to be quite pure. Many solutions were tried in an effort to dissolve the oxidized lead minerals and

Jan 1, 1949

By Alexander L. Field

The rate of elimination of carbon largely controls the time required to make a heat of steel by the basic open-hearth process and to an important degree determines the cost of refining. Practical experience has led to the generally accepted belief that the use of slags relatively high in iron oxide, such as are required to bring about rapid refining, leads to a certain sacrifice of quality in the product. As a consequence, a compromise must be made between the exceedingly slow rate of carbon drop which would correspond to the ideal case and the rapid rate which would best satisfy the condition of minimum cost. An increase in rate of refining necessarily implies an increase in the concentration of iron oxide dissolved in the metal. However, even for the infinitely slow rate that corresponds to slag-metal equilibrium, the metal would contain a certain definite concentration of dissolved iron oxide. It is a matter of great practical importance, therefore, to determine the quantitative relation between the minimum or equilibrium concentration of iron oxide in the metal and the higher concentrations which must actually obtain in practice. The present paper is devoted to the development of certain equations, derived from the established laws of physical chemistry, which will enable this relation between rate of refining and the degree of oxidation of the metal bath to be computed from operating data. So attempt is made to exhaust the possibilities of this general method of treatment. In considering rate of refining, attention is mainly confined to rate of carbon elimination. However, the equations are of a more general nature and their application may readily be extended. The results of the preliminary calculations given herein indicate that increased rate of refining may have a decided effect in increasing the concentration of iron oxide dissolved in the metal. The uncertainty which attaches to the calculated value for this relationship arises in part from probable errors in experimental data on which the calculations are based, and in part from the lack of complete or favorably disposed information on basic open-hearth practice. When the relation between rate of refining and degree of oxidation of the metal has been more accurately established than has been done in the present paper, it will then become possible to consider what comprises

By H. M. Howe

I WISH to present to you a few thoughts on some of the phenomena and laws of iron smelting. Owing to the great complexity of the subject, to the great variety of points to be taken into consideration, many of which are very poorly understood, and to the meagreness and even conflictoriness of our information with regard to some of the most important laws which govern the subject, the fruits of such thoughts as I venture to offer you must be received as speculations, not as facts. Nevertheless, in discussing old phenomena from new standpoints, thus furnishing a metallurgical parallax, if I may say so, these theoretical speculations may have their value in helping to a clearer comprehension of the phenomena and laws we now know, and in suggesting new lines of inquiry. While an increase of height in blast furnaces is not always followed by increase in their power of production, experience proves that it tends to increase it; for while we have many cases of short furnaces producing more iron than longer ones, yet enormous productions, such as those of the Lucy and Isabella furnaces of Pittsburgh, and of the furnaces of Esch sur l'Alzette, in Luxembourg, have never been reached in short furnaces. We may safely infer that height is an element essential to great production, though of course not the only essential element, and that, in the case of high furnaces which are not capable of great production, some other essential element is wanting. Moreover, experience teaches that within limits increase of height tends to increase the producing power in a still higher ratio. Thus, in the Esch furnace, which is 19.8 meters (65 feet) high, 393 tonnes (or 387 gross tons) of 312 per cent. Ore

Jan 1, 1877

By C. S. Finney, John Mitchell

On December 31, 1959, there existed in the United States 15,993 slot-type coke ovens capable of producing 81,447,700 net tons of coke. These ovens were concentrated in 74 coke plants in 21 different states. As of the same date, there were 7448 beehive ovens in existence at 45 plants in the states of Pennsylvania, Virginia, West Virginia, and Kentucky. Total annual capacity of the existing beehive ovens was 4,368,800 net tons, but only 5148 ovens with a capacity of 3,131,600 tons were in operating condition. It is interesting to compare the average dimensions of slot-type ovens built during recent years with the 30 ft x 5 ½ ft x 16 ½ in. ovens erected at Syracuse, N. Y. in 1892. A composite oven built according to the average dimensions of all those erected between 1954 and 1958, for instance, would be 39 ft long. 12 ft high, and 18 in. in width. The coal capacity would be 16 tons as against the 4.4 tons which could be charged to the Syracuse ovens. Of the 15.993 slot- type ovens in existence at the end of 1959, by far the greater number were built by the Koppers Co. whose total of 11,280 ovens included 7891 Koppers- Becker and 3389 Koppers ovens. Of the remainder, there were 3260 Wilputte, 1350 Semet-Solvay, 63 Otto, and 40 Simon Carves ovens. By-product coke oven plants are usually classified either as furnace or merchant plants. According to the definitions used by the US Bureau of Mines, the former are "those that are owned by or financially affiliated with iron and steel companies whose main business is producing coke for use in their own blast furnaces. All other coke plants are classified as merchant. They include those that manufacture metallurgical, industrial, and residential heating grades of coke for sale on the open market; coke plants associated with chemical companies or gas utilities; and those affiliated with local iron works, where only a small part (less than 50 pct of their output) is used in affiliated blast furnaces." The annual coke capacity of the merchant plants during 1959 was 10,393,000 tons. However, the by-product oven of today is essentially an appurtenance of the iron and steel industry, rather more than 87 pct of total by- product coking capacity being concentrated at furnace plants. This was not always so. There was a time when the merchant plants played a much greater part in meeting the US demand for coke and gas. High noon for the merchant plants was reached during the early 1930's. By 1932 there were as many by- product oven installations being operated by the merchant sector of the industry as by the coke divisions of the iron and steel industry (44 of each), and in the same year the merchant plants produced 46.5 pct of all by-product coke made in the country. Since that time their contribution has drastically declined. In 1940 merchant plants were responsible for only 23.2 pct of total US production, and by 1950 their number had decreased to 30 plants which turned out 18.5 pct of the total by-product coke made. At the end of 1959 only 20 of the 74 existing by-product oven installations were merchant plants. They ac- counted for 12.5 pct of the year's production, or 6,849,786 net tons. This percentage has remained fairly constant since 1954. There are several reasons for the decline of the merchant coking industry. For example. On the grounds of economy, quality control, continuity of supply, and so on, the iron and steel industry usually prefers to control its own mines and carbonize its own coal at or near to the blast furnace rather than rely on independent operators for metallurgical coke. As the steel companies have enlarged their own coking facilities, so has the need for coke obtained from other sources declined. Furthermore, not only has the steel industry increased in self-sufficiency by building mare coke ovens during recent years, but it has also progressively improved the fuel efficiency of its blast furnaces. During the years 1947-49 the average coke consumption per ton of pig iron was 1892.8 lb. During 1958 the corresponding figure was 1613.4 lb. There are many individual furnaces where still better results are being obtained, and further reductions in the average may be expected. Perhaps the greatest threat to the merchant coking plant has been the fantastic increase in the use of natural gas and petroleum products for purposes which manufactured gas once served. So deadly has the com- petition from natural gas and oil been that it has almost eliminated by-product oven installations owned by public utilities. In the peak years of the early 1930's there were 23 such public utility plants. In 1960 only two were left. One of these, owned by the Citizens Gas and Coke Utility, was at Indianapolis, Ind.; the other was the plant operated by the Philadelphia Electric Co. at Chester, Pa. The non-utility merchant plants have also been sorely hit. With gas sales revenues reduced, domestic

Jan 1, 1961

By W. F. Mattes

The manufacture of steel rails in the United States upon a large scale may be roughly dated from the years 1875-76, and the same years witnessed an active movement among the railroads toward the adoption of heavier and improved patterns. In this movement each road was a law unto itself, and the "personal equations " of some scores of engineers were so freely injected into the calculations that patterns were multiplied in the most absurd and mischievous manner, until at length the burden upon the mills became wellnigh unendurable, and called forth a vigorous protest in Mr. Holley's paper,* read before the Institute in February, 1881. There were then regularly manufactured in the various mills of the United States, no less than 119 different patterns of steel rails, subject to current order, of which 64 per cent. were embraced under five weights per yard. Commenting upon these and other figures there given, Mr. Holley stated as the primary object of his paper, " to show that,, while this multiplication of rail-patterns is an annoyance and an expense to rail-makers, it is a source of immense loss to railway companies." Since 1876 the increase in gross annual tonnage upon our leading lines has been very great, and has been accompanied by an increase of wheel-loads and running-speeds. As the average weight of the rails of 1876 was by no means excessive, the growing deman Is of traffic have slowly driven the roads toward stiffer sections, inaugurating a movement that now promises to become epidemic. In 1876 a 67-pound rail was a first-class equipment; to-day everything under 75 pounds is light, and many 80's are coming into use. European practice has long been heavier than ours; in part because the higher cost of sleepers has led to an average of 3-feet spacing, instead of two-feet as with us. The old 84-pound double-header, and Sandberg's 80- and 89-pound rails, respectively 51/4 inches and 591/2 inches high, are reported common on English roads; and he is strongly advocating the general adoption of the 100-pounder shown in Fig. 7, with what success I have not learned, except that the Belgian government has ordered a lot. Mr. Sandberg points out the undesirability of frequent changes of pattern, and the recent rapid growth in traffic-requirements; prognosticates a continuance of this

Jan 1, 1887

By R. S. Dean

REQUIREMENTS for war materials have led to large scale experimentation upon metallurgical innovations. It is of interest to inquire what this may contribute of permanent value to our existing technology, as innovations adopted during war are apt to be discarded promptly at its end. This is because utilization of substandard ores usually requires a new technology for ore treatment, and a new use-pattern for employment of the products. Thus two very different problems are involved: first, devising a process; then, adopting its products by industry, with readjustments of the use-pattern if necessary. A new process may be as good or better than an old one, but the readjustments required for use of its products may prevent its general adoption if this implies scrapping existing plants and investing much additional capital. Metallurgical innovations are of three kinds: I. The use of substandard material in processes already established; 2. The grading-up of substandard material to render it more suitable for established processes; 3. The adjustment of technology and use-pattern to the raw materials that we have.

Jan 1, 1945

By A. Lubinski

In drilling operations, attention generally is given to hole angles rather than to changes of angle, in spite of the fact that the latter are responsible for drilling and production troubles. The paper presents means for specifying maximum permissible changes of hole angle to insure a trouble-free hole, using a minimum amount of surveys. It is expected that the paper will result in a decrease of drilling costs, not only by avoiding troubles, but also by removing the fear of such troubles. SUMMARY, CONCLUSIONS AND RECOMMENDATIONS Excessive dog-legs result in such troubles as fatigue failures of drill pipe, fatigue failures of drill-collar connections, worn tool joints and drill pipe, key seats, grooved casing, etc. Most of these detrimental effects greatly increase with the amount of tension to which drill pipe is subjected in the dog-leg. Therefore, the closer a dog-leg is to the total anticipated depth, the greater becomes its acceptable severity. Very large collar-to-hole clearances will cause fatigue of drill-collar connections and shorten their life, even in very mild dog-legs. Another finding regarding fatiguing of collar connections in dog-legs is that rotating with the bit off bottom sometimes may be worse than drilling with the full weight of drill collars on the bit, mainly in highly inclined holes when the inclination decreases with depth in the dog-leg. Means are given for specifying maximum dog-legs compatible with trouble-free holes. An inexpensive technique proposed is to take inclinometer or directional surveys far apart; then, if an excessive dog-leg is detected in some interval, intermediate close-spaced surveys are run in this interval. The application of the findings should result in a decrease of drilling costs, not only by avoiding troubles, but mainly by removing the fear of such troubles. The result would be much more frequent drilling with heavy weights on bit, regardless of hole deviation. Because of errors inherent to their use, presently available surveys are not very suitable for detecting dog-legs. There is a need for instruments especially adapted to dog-leg surveys. Crooked hole drilling rules should fall into two distinct categories—(1) those whose purpose is to bottom the hole as desired, and (2) those whose purpose is to insure a trouble-free hole. Three kinds of first-category rules in usage today are as follows. 1. A means to bottom the hole as desired is to prevent the bottom of the hole from being horizontally too far from the surface location; this may be achieved by keeping the hole inclination below some maximum permissible value such as, for instance, 5. 2. Another means to achieve the same goal is to limit the rate at which the inclination is allowed to increase with depth. A frequently used rate is 1/1,000 ft. In other words, a maximum deviation of l° is allowed at 1,000 ft, 2 at 2,000 ft, 3 at 3,000 ft, etc. 3. Whenever application of the first two means precludes carrying the full weight on bit required for most economical drilling, then the best course is to take advantage of the natural tendency of the hole to drift updip, displace the surface location accordingly and impose a target area within which the hole should be bottomed. This method has already been successfully applied,'.' and its usage probably will become more frequent in the future. Means for calculating the amount of necessary surface location displacement are avail-able.3'5'6 If in high-dip formations the full weight on bit should result in unreasonably great deviations, the situation could be remedied by increasing the size of collars and (if needed) the size of both hole and collars,351 or in some cases by using several stabilizers. Rules which would fall into the second category (i.e., rules whose purpose is to insure a trouble-free hole) are seldom specified today. It is vaguely believed that following Rules 1 and 2 of the first category will automatically prevent troubles. Actually, this is not true. If at some depth the only specified rule is that the hole inclination must be less than 4", the hole may be lost if the deviation suddenly drops from 4 to 2, or if the direction of the drift changes, etc. Rule 3 of the first category is generally used in conjunction with a rule belonging to the second category, namely, that the hole curvature' (dog-leg severity) must not exceed the arbitrarily chosen value of 1½ /100 ft. Moreover, when using this rule, the industry is not clear over what depth intervals the hole curvature should be measured. All this results in a frequent fear

By Cyril Stanley Smith, Earl W. Palmer

STRIP of any of the metals used for deep drawing operations occasionally yields cups that are defective because of a rim that varies in height around the cup in a wave-like manner. Some such defects are traceable to tools or other press factors, but when the protuberances formed (usually four in number on brass and other copper alloys) are symmetrically disposed with respect to the rolling direction of the strip, they are invariably attributable to the metal. The effect is known as "earing" and the protuberances are called "ears." Other terms frequently heard are "tips," "scallops," and "corners." It is recognized that the effect is most commonly a result of a directional crystal structure produced by rolling and annealing operations in the manufacture of the metal strip. 'Numerous papers dealing with various aspects of the earing effect have appeared in the literature, those listed in the references1 being especially interesting and valuable. An investigation of the factors influencing earing of brass cups has been in progress in the laboratories of the American Brass Co. for several years, and it was thought desirable to make some of the results generally available in summarized form. The present paper discusses many factors that do and do not contribute to ear formation. In addition, a section is devoted to methods of minimizing the earing tendency of brass sheet by proper selection of the cold-rolling and annealing schedule by which it is produced. In the space available, it is impossible to quote detailed experimental procedures and numerical results. However, the authors make no statement that they do not believe to be properly substantiated, either by experimental evidence obtained under laboratory conditions or by experience in the actual production of deep-drawing brass in the brass mill. MECHANISM OF EAR FORMATION It must be clearly understood that the formation on cups of symmetrical ears, four or more in number, is attributable solely to the strip metal, and results from the strip having different deformation characteristics in different directions. The tools used in the drawing process, or the type and completeness of lubrication of the strip, have nothing to do with the problem of ears, although they do, of course, greatly affect the "drawing quality" of the strip and the general appearance of the cup. A single tip may be drawn up on the rim of a cup because of misalignment of the tools, or because the gauge of metal varies from side to side of the strip. The two-ear form that sometimes appears is also traceable to gauge variations. However, the four-ear and six-ear symmetrical forms that we are concerned with here are caused by factors inherent in the structure of the metal itself.

Jan 1, 1942

By R. E. Head, E. L. Tucker

In the metallurgy of precious metals, it has been standard practice for years to use cyanogen compounds, so it was but natural that early investigators in the field of flotation should consider these compounds as possible flotation reagents. In Australian Patent 9508, of 1913, alkali cyanides were described as suitable reagents for the separation of heavy sulfide minerals, the reagents being employed either in an alkaline or neutral circuit. In U. S. Patent 1236501, of 1917, to John M. Tibbet, the use of cyanide in conjunction with soda ash or lime is described. One of the claims of this patent reads, "An improvement in the cyanide process for the treatment of ores comprising, mixing the ore with cyanide solution and oil and alkali: emulsifying the oil in the presence of the ore, the alkali and the cyanide solution, floating a portion of the values in the pulp by producing gas bubbles in the mixture and removing the values floated." More recently, Sheridan and Griswold, in U. S. Patents 1421585 and 1427235, describe a somewhat similar process and have successfully introduced it in the mill of the Timber Butte Milling Co. U. S. Patent 1429544, of 1922, to Stevens, describes the use of double cyanides of copper, zinc, and lead. The success of cyanide as a reagent in the differential flotation of lead and zinc sulfides in highly complex ores is proof that these patents have a solid foundation. Although the technique of their application to particular ores has been worked out in many cases, no one, so far as is known, has attempted to describe the nature of the action of the cyanide or to determine the ideal conditions for its application. It was the purpose of the present investigation to gather information on these points. Naturally this would have been an exceedingly ambitious program had the attempt been made to study the effect of cyanide

Jan 1, 1926

By P. W. Bridgman

It is characteristic of most scientific investigators that they are not satisfied with the discovery of new facts, no matter how curious or unexpected, but that along with the factual discovery there is a constant effort to understand. It appears that one's interest in, and satisfaction with, the discovery of an array of new experimental facts is enormously increased if one has at the same time a theory or hypothesis guiding one's expectation of what sort of new experimental discovery may lie around the corner. Conversely, as a theoretical physicist one's satisfaction with his theory is greatly enhanced if along with the development of the theory can go the discovery of new experimental facts, confirming or perhaps modifying the theory as it grows. Of course, there have been long arid stretches in the history of physics in which new data of unquestioned ultimate importance have piled up, without much inspiration or illumination in the way of understanding. For 50 years spectroscopy had such an arid history, but how irksome this was felt to be is plainly shown by the almost audible relief that greeted the first success by Bohr in injecting understanding into the situation, and by the fresh rush of experimenters into this field when the prospect of understanding had once been offered. The investigations in the field of high pressure, which have occupied me for a long time,' until the last few years have been in very much the same sort of situation as spectroscopy before the advent of Bohr. A great many kinds of data were collected for a great many solid and liquid substances, and there could be no question of the importance of these data, because the uniform change of dimensions produced by hydrostatic pressure is perhaps the simplest conceivable type of alteration to which a body can be subjected. But except for a few isolated flashes, there was no theoretical illumination, so that it had to be to a large extent the enthusiasm of the collector that kept me going. However, within the last few years the wave-mechanics theory of solids has progressed so rapidly that

Jan 1, 1938

By P. W. Bridgman

It is characteristic of most scientific investigators that they are not satisfied with the discovery of new facts, no matter how curious or unexpected, but that along with the factual discovery there is a constant effort to understand. It appears that one's interest in, and satisfaction with, the discovery of an array of new experimental facts is enormously increased if one has at the same time a theory or hypothesis guiding one's expectation of what sort of new experimental discovery may lie around the corner. Conversely, as a theoretical physicist one's satisfaction with his theory is greatly enhanced if along with the development of the theory can go the discovery of new experimental facts, confirming or perhaps modifying the theory as it grows. Of course, there have been long arid stretches in the history of physics in which new data of unquestioned ultimate importance have piled up, without much inspiration or illumination in the way of understanding. For 50 years spectroscopy had such an arid history, but how irksome this was felt to be is plainly shown by the almost audible relief that greeted the first success by Bohr in injecting understanding into the situation, and by the fresh rush of experimenters into this field when the prospect of understanding had once been offered. The investigations in the field of high pressure, which have occupied me for a long time,' until the last few years have been in very much the same sort of situation as spectroscopy before the advent of Bohr. A great many kinds of data were collected for a great many solid and liquid substances, and there could be no question of the importance of these data, because the uniform change of dimensions produced by hydrostatic pressure is perhaps the simplest conceivable type of alteration to which a body can be subjected. But except for a few isolated flashes, there was no theoretical illumination, so that it had to be to a large extent the enthusiasm of the collector that kept me going. However, within the last few years the wave-mechanics theory of solids has progressed so rapidly that

Jan 1, 1938

Jan 1, 1942

By D. A. Dahlstrom

In the paper, a comparison was made between flowsheets using the screen bowl centrifuge and disc filters, respectively, as the primary dewatering device. The authors very effectively show that by raising feed temperature, mechanical dewatering is enhanced through reduced viscosity of the water. When a final coal moisture of 10% is required, the net effect of heating the feed is a reduction in thermal requirements because of the lower evaporated load on the dryer. The flowsheet comparison on this, however, was not completely correct. Disc filters do not generally utilize enhanced mechanical dewatering through increased temperature. Horizontal belt filters, through the optimal use of steam heating of the filter cake, have shown significant cost reductions over disc filters where steam is not used. In addition, the authors forgot to mention that there is a certain fraction of the feed that is so fine that it cannot be recovered by the centrifuge economically. That is the function of the filtration device shown in [Fig. 4]. In subbituminous pipeline coals, this fraction represents more than 10% of the feed. Even after flocculation and belt pressing, the moisture content in the fine fraction is 30%-40. Recent tests on a subbituminous pipeline coal slurry, compared an Eimco-Extractor horizontal belt filter with the screen bowl centrifuge flowsheet shown in [Fig. 4]. Mechanical dewatering was enhanced through the use of a steam dry zone after the initial dewatering zone. Vacuum pump horsepower was reduced by more than 50% through the use of condensers, and heat recovery was utilized to minimize thermal costs. Thermal drying to 10% moisture by weight was required in both flowsheets. The 0.5 wt% fines in the filtrate were flocculated and recycled to the filter, thus eliminating the belt press and solids mixers. When the three major operating costs (which normally account for 50%-75% of the coal operating costs) of steam, electricity, and flocculants at current prices were calculated, the flowsheets utilizing the Eimco-Extractor had cost savings vs the centrifuge flowsheet of 89c/t (81c per st) of surface dry coal. This advantage increases with increasing thermal and electricity prices. I congratulate the authors for the strides made with the screen bowl centrifuge. However, filtration flowsheets continue to be improved and their simplicity and low thermal and electrical requirements should not be so quickly dismissed.

Jan 1, 1984

Jan 1, 1941

Jan 1, 1941