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By Roy R. Jones, R. R. Sawyers

It has long been comnlon knowledge that workers in anthracite are prone to develop a disabling disease of the lungs. Some of the earliest scientific contributors dealing with anthracosis were: Pearson1, in his report in 1813, on the coloring matter of the bronchial glands and black spots in the lungs; Stratton2, in 1838, who first termed the condition anthracosis; Greenhow3, who reported to the pathological society in 1865, on the Black Lung of the Collier, and Pick4 in 1870, who reported on the chemical composition of the ash of a collier's lungs. Visconti5, in 1870, is accredited with being the first to use the term "silicosis" to denote the pathological condition of the lungs resulting from the inhalation of silica. Rovida6 confirmed the reports of Pick and Visconti in 1871, in his report on a case of silicosis and chemical examination of the lungs for silica content. The relationship of pulmonary infection, as associated with disabling pneumoconiosis affecting the coal miner, has frequently been discussed. While most reports have emphasized the role of infection, there has been some disagreement regarding the prevalence of tuberculosis among those suffering from anthracosis. The report by Wainwright and Nichols7 in 1905 has frequently been cited to show that the incidence of pulmonary tuberculosis among coal miners was less than that among the general population. It was their opinion that pulmonary tuberculosis was more prevalent among the miners' families than among the miners themselves. Collis and Gil-christ, in 1928 in their study of the Effects of Dust upon Coal Trimmers, concluded that among such workers there was an excess of deaths from bronchitis and pneumonia but not from pulmonary tuberculosis. They

Jan 1, 1936

By E. C. Houston, R. A. Laurence, F. A. W. Davis, L. L. McMurray, H. S. Rankin

This paper is coodensed from several reports by members of the staff of the Minerals Testing Laboratory of the Tennessee Valley Authority, on a series of experimental tests in the beneficiation of barite of the Valley area. These experiments were conducted upon a large number of samples taken from several mines in three different districts. The area contains numerous producing deposits, nearly all of which are hampered by the high iron and silica content of the ores. Because of the small difference in specific gravity between the iron oxide and the barite, a gravity separation is generally poor. The removal of the iron thus offers a special problem. Some of the operators have turned to magnetic separation to meet the shipping requirements for less than one per cent iron. The present experiments were conducted to determine the application of decrepitation or flotation in simplifying the concentration of the barite by removing the iron oxide and silica in one operation. Practically all the barite marketed in the area has been as "off-color" crude. The bleaching studies were made to determine the bleach-ability of the ores to alleviate this inferior grading, placing them on the market as bleached barite. Geology Barite has been produced at many places in the Tennessee Valley area, and prospects and minor deposits are known at many other places, but practically all the production of barite in the Valley has been from the Sweetwater district of East Tennessee. Other leading areas of former production are the Tazewell-Russell counties areas of southwest Virginia, the Del Rio-Stackhouse district of East Tennessee and western North Carolina, and the Fall Branch district of upper East Tennessee. The areas described in this paper are those from which samples used in the concentration tests were obtained.

Jan 1, 1942

FREQUENTLY the careful engineer puts the word porphyry in quotation marks or precedes it with "so-called," when he writes of the Porphyry Copper mines. This is done by way of serving notice that he is aware that the term is not a precise one, though no one who is informed on the subject would in any event misinterpret it. The name originated from the fact that the rock containing the copper at Utah Copper, Morenci, Nevada Consolidated, and Braden-the first four to be developed-was in each instance known as porphyry. The term was convenient; and when Ray, Miami, and inspiration came along they fell into the Porphyry category even though the ore consisted essentially of a rock called schist instead of porphyry. The word is not inclusive enough; nor as a matter of fact is it sufficiently exclusive. Numerous copper deposits occur in porphyry rocks that are not Porphyry Coppers, paradoxical as it may seem. Desiring to be more accurate and at the same time to use a word that is in some degree descriptive, various engineers have adopted the expression "disseminated copper deposits." This alludes to the characteristic scattering of grains or specks of copper minerals more or less uniformly throughout the mass of the rock. Yet here again the implication is not entirely accurate, for the following reason: in some of the ores, the proportion of copper minerals "peppered" in the rock is small, compared with that which coats the walls of cracks and minute fissures; and that which is found as veinlets along planes of fracture. Many geologists have extended their interpretation of the term disseminated to include both types of mineral occurrence. One of the most striking features of the Porphyry ores is the intense shattering and fracturing that the rock underwent at some period or periods prior to the deposition of the copper

Jan 1, 1933

By Joseph Chalmers, J. S. Desmond, R. Van A. Mills

[Because of the limited space in this volume and the fact that a description covering the oil recovery buildings and equipment (see page 4, Technical Publication No. 144) will be given in a forthcomnig U. S. Bureau of Mines publication, and because the paper was published in detail as Technical Publication No. 144, and is available as a separate at the Institute, it is impossible to include here more than the following brief extract.] Problems Being Studied The selection of the first problems to be studied was based largely upon the following very practical questions asked by several of the largest operators in the Mid-Continent field. 1. What are the causes for the formation of excessive amounts of bad thick oil on properties that are being repressured with compressed air and how can this trouble be prevented? 2. Why, in some areas, does the oxygen in the air injected into an oil sand during repressuring operations apparently change to carbon dioxide? Is carbon dioxide formed by the oxidation of some of the oil in the sand'? How can the formation of inert or low B.t.u. casinghead gas, loaded with nitrogen, carbon dioxide and oxygen, be prevented? 3. What percentage of the oil originally present in an oil sand can be recovered by the ordinary methods of operation when the gas originally dissolved in the oil is the main propulsive agent? 4. What percentage of the amount of oil produced by ordinary methods can be recovered under average conditions by repressuring a so-called depleted oil sand? 5. What are the relative propulsive efficiencies of compressed air and natural gas in repressuring operations? 6. What are the practical advantages of pressure maintenance and early repressuring as compared with late repressuring?

Jan 1, 1929

By Roy R. Jones, R. R. Sawyers

It has long been comnlon knowledge that workers in anthracite are prone to develop a disabling disease of the lungs. Some of the earliest scientific contributors dealing with anthracosis were: Pearson1, in his report in 1813, on the coloring matter of the bronchial glands and black spots in the lungs; Stratton2, in 1838, who first termed the condition anthracosis; Greenhow3, who reported to the pathological society in 1865, on the Black Lung of the Collier, and Pick4 in 1870, who reported on the chemical composition of the ash of a collier's lungs. Visconti5, in 1870, is accredited with being the first to use the term "silicosis" to denote the pathological condition of the lungs resulting from the inhalation of silica. Rovida6 confirmed the reports of Pick and Visconti in 1871, in his report on a case of silicosis and chemical examination of the lungs for silica content. The relationship of pulmonary infection, as associated with disabling pneumoconiosis affecting the coal miner, has frequently been discussed. While most reports have emphasized the role of infection, there has been some disagreement regarding the prevalence of tuberculosis among those suffering from anthracosis. The report by Wainwright and Nichols7 in 1905 has frequently been cited to show that the incidence of pulmonary tuberculosis among coal miners was less than that among the general population. It was their opinion that pulmonary tuberculosis was more prevalent among the miners' families than among the miners themselves. Collis and Gil-christ, in 1928 in their study of the Effects of Dust upon Coal Trimmers, concluded that among such workers there was an excess of deaths from bronchitis and pneumonia but not from pulmonary tuberculosis. They

Jan 1, 1936

By Will H. Coghill

FLOTATION has been so closely allied with the sulfide minerals and their early and associated oily reagents that the term "oil flotation" has erroneously been applied to the entire flotation process. Today, the term "chemical flotation" might be used to advantage. Flotation literature has dealt primarily with the removal of sulfides. from non-sulfide gangues, and the separation of one sulfide from another.. Now, the application of the process to the separation of nonsulfide minerals is coming to the fore; and from the standpoint of the number of commercial minerals involved, the flotation of nonsulfides offers the larger field. Here, soap or soap-forming substances, such as the fatty acids and their derivatives, are used; hence there may well be a subdivision of the chemical flotation process called "soap flotation." Early experimenters learned that it was easy to form a froth or foam that would carry a part or all of the ore charge over the lip of the flotation machine; but this could not be regarded as flotation because of the lack of selectivity. Doubtless soap was one of the first reagents tried, and doubtless it was rejected on account of its gangue-carrying properties. Now this same gangue-carrying ability makes soap an acceptable reagent, for we are dealing with that, which among sulfides, is considered "gangue." As in the flotation of sulfides, so in the flotation of nonsulfides, the selective flocculation of the mineral and the dispersion of the gangue are the first objectives. In fact, these two phenomena epitomize flotation. They depend upon the unlike surface properties of the respective minerals; and, as long as the components of an ore have unlike surface properties, a separation is possible, at least in theory. Often in nonsulfide flotation it makes little difference which mineral floats and which is depressed; generally only a separation is sought.

Jan 1, 1932

For many years the occurrence of gold in the Coeur d'A1ène region had been rumored among the pioneers of the Northwest. It is stated that as early as 1853 gold was discovered in this district by Donelson, of the Stevens expedition, but the hostility of the Indians prevented prospecting. In 1858, when Lieutenant John Mullan surveyed the military road across the Bitter hot mountains, the members of his expedition, most of whom had mined in California, noticed sundry outcrops of good-looking quartz, and some of them actually found gold, as is recorded in a letter that Mullan wrote, from Washington, in 1884. The first successful prospector in the Coeur d' Alène was Tom Irwin, who worked a quartz vein on the Mullan road in the spring of 1879. Two years later he met A. J. Prichard, who was engaged in the lumber business; he told him what he thought of the chances of placer mining in the upper reaches of the Coeur d7AlBne river. This was in 1881. Prichard became keenly interested, and himself found gold on several creeks, one of which is now known by his name, at a place close to the site of the town of Murray.* In 1883 Prichard located a number of claims, and shortly afterward he wrote a letter to the members of a Liberal League to which he belonged, inviting them to "secure the lion's share" of the mineral wealth he had uncovered. His letters caused a stampede from Montana and Colorado, and from South Dakota also, to the Coeur d'Alène gold belt in the summer of 1883. A town, named Eagle City, was surveyed; in 1884 lots sold at prices ranging from $200 to $2000. The buildings were made of logs and shingles. Shoveling of the snow in' front left s

Jan 1, 1932

By James F. Kemp

In submitting an additional contribution to the discussion on ore-deposits in the recent volumes of the Transactions, it is my desire to adhere closely to matters of material importance as affecting the actual processes. Judging from the discussion by Professor Van Hise, and from one or two reviews or other articles by associates of his in geological work, the impression seems to prevail that, in so far as my paper* referred to his masterly essay, I was guilty of misconceptions regarding both the part attributed by him in it to the igneous rocks and the ubiquitous presence of the ground-water. I should regret extremely to be wanting in these particulars or to have misunderstood one for whose great services in this and other branches of geology no one has a higher esteem than myself. I have, however, in the most careful way, and with these points in mind, read his essay again, and, taking it as a whole, I cannot gain any different impression of relative magnitudes than the one first received. The importance of the igneous phenomena and the restrictive influence of the processes described by " cementation " in their effect upon the ground-water, as set forth in Professor Van Hise's "Discussion" (Trans., xxxi., 292), impress me as being in very marked contrast with the same things in his first essay. If the point seems to anyone of sufficient importance, it can easily be decided by reading the originals. My paper was the result of some years of observation, reading and reflection, and was meant to be an independent contribution, controversial only in some subordinate particulars. In depicting the drama of the deposition of ores, I cannot but feel that Professor Van Hise assigned to the chorus and the scene-shifters some characters which, it seems to me, should

Jan 1, 1903

By F. T. Havard

The present truce in litigation between Western smelting and ranching interests gives opportunity for a summary of the results achieved by metallurgists in condensing fume and de-acidifying furnace-gases. In the absence of complete records of past experiments, there ha's been a good deal of unliecessary duplication of attempts and failures. Yet, especially uilder the recent policy of our large corporations, looking to the economic recovery of the values of by- and waste products, . original and, in some cases, effective measures have been developed by American metallurgists. In the case of Bliss us. the Anaconda Copper Mining Co., the Montana Suprenle Court, recognizing the progressive efforts made to render the flue-gases innocuous, and the value to the community of the smelting company's operations, refused to hamper its work, and returned a verdict in favor of the defendant. In the trial, the experimental farms of the company ill the so-called "aff'ected region" were proved to be thriving perfectly, showing that immunity was guaranteed to vegetation and stock by tlle wide distribution of the sulyhurous acid gas in the dry air of Montana. Indeed, L. S. Austin has proved that by the time the fume is 4,000 ft, distant from the stack, the percentage of sulphurous acid has been diminished from 2.28 to 0.00045; and Angus Smith has shown that rain must contain 40 parts per million of free acid before vegetation is affected. The arsenic in the stack-gases is but a very small part of the original content of the ore, of which 80 per cent. and over is rejected in the coilcentrator and furnace waste-products or recovered in the flues, Nevertheless, neither the peace in Montana nor the armistice

Jan 1, 1911

By Prof John E. Church

It is a well-known fact that under similar conditions a ton of pig iron can be made from any ore with less fuel when charcoal is used than when coke or anthracite is employed for heating. The cause of this superiority is entirely undiscovered, and no explanation has yet been offered which has won even temporary acceptance. Such as they are the hypotheses heretofore presented are of two general kinds, and they come from those two divisions of the working force which are so often antagonistic in all professions, the scientific and the practical men. The theory of the scientific men is drawn from the chemical reactions which are known to go on in the furnace, and it is well expressed in a recent paper by Prof. Akerman, of the Stockholm (Sweden) School of Mines. It makes the superiority of charcoal as a fuel in the blast furnace to depend upon its quick and thorough reduction of carbonic acid. This property belongs to charcoal in virtue of its porous structure. Its cells have a diameter of only one twenty-four hundredth of an inch, and one grain of charcoal has been computed to have a surface of two and four-tenths square feet. According to the theory in question, carbonic acid is formed by the first impact of the air upon the fuel; but in charcoal furnaces the acid is immediately reduced to oxide by taking the necessary amount of carbon into combination, and the gas reaches its highest reducing power even in the near vicinity of the tuyeres. Coke, being harder, does not produce so strong a reducing gas in that part of the furnace. Carbonic acid is formed as in the case of charcoal, and remains longer before its reduction to oxide is completed. Anthracite is the

Jan 1, 1879

By Kiyoshi Azuma, Hiroshi Kametani

Dissolution of a ferric oxide in acid solution is divided into two different types In the accelerated type dissolution proceeds in three stages 1) an inittal reaction during which the dissolved amount of oxide is nearly proportional to the cube root of time ; 2) an accelerated reaction: and 3) a final stage during which dissolution approaches completion. This course of dissolution gives an S-shaped curve in the above sequence OH a log weight percent of dissolved oxide against log time graph. In the parabolic type dissolution proceeds in four stages: first and second stages similar to those of the accelerated type; 3) parabolic-rate dissolution during which the dissolved amount of oxide is nearly proportional to the square root of time: and 4) a final stage. The effect of the kind of acid, the temperature of solution, and the concentration of acid was investigated. The results are discussed and a rate equation is proposed. AN attempt has been made to obtain some information on dissolution of a ferric oxide in various acid solutions. In view of hydrometallurgical processes the dissolution of ferric oxide is of less importance than that of zinc oxide or copper oxide in general. One of a few processes which intend to dissolve ferric oxide is an elimination of iron impurity from acid-insoluble materials. However, most leaching processes of oxide ores and cinders are accompanied with more or less dissolution of iron. According to Pryor and Evans1 the rate of dissolution of a ferric oxide in various acids decreased in the order of hydrofluoric acid > hydrochloric acid > sulfuric acid > perchloric acid. This order was in accord with the order of decrease of the complexing affinity of the anion for ferric ion,

Jan 1, 1964

By John T. Norton

In spite of the very general errlployment of nitride hardening, there is still considerable doubt as to the real nature of the mechanism involved. Experience has shown that the addition of small amounts of hardening elements to iron or steel results in a wide variety of desirable properties in a nitrided case. Perhaps the foremost of these elements is aluminum and in this investigation an attempt has been made to study the behavior of aluminum during the hardening process. It is believed that the establishment of a complete atomic picture of the metal at various stages of the process will indicate the relationships between the several kinds of atoms and their individual influences on the physical properties in a clear and direct fashion. A consideration of the problem suggests a surprising similarity between the mechanisms of nitride hardening and of age-hardening. It is now generally understood that age-hardening may take place by one of two distinct processes, the first involving the precipitation of a finely dispersed phase and the other being concerned with the modification of an existing phase. Following much the same line of reasoning, two theories of nitride hardening have been suggested. The first explanation, which has been generally discussed, particularly by Fry,' states in brief that the presence of aluminum causes the precipitation of aluminum nitride during nitriding and that this finely dispersed phase is the primary cause of hardening. The second explanation, which has not been published but which has been freely discussed by those interested in the problem, postulates the substitution of aluminum atoms for certain of the iron atoms in the several iron-nitrogen phases in the same manner that the substitutional iron-alurninurn solid solution is formed. The marked increase in hardness, as compared with the aluminum-free system, is attributed to the severe lattice distortion accompanying this replacement.

Jan 1, 1934

By Mark C. Malamphy

During colonial times, Brazil was famous for the richness of her alluvial gold deposits. Paul Ferrand has estimated that the gold produced during the period from 1700 to 1820 was the equivalent of some 64 million pounds sterling. Since that time, most of the more prolific alluvial deposits have been exhausted. A few gold mines are still functioning, notably the Morro Velho mine, which is one of the deepest mines in the world. Today, the gold production of Brazil is insignificant when compared with world figures, but there are still many gold-bearing regions and it is probable that in at least some of them profitable returns would result from an exploitation program taking advantage of all the most modern innovations in gold mining and ore treatment on a large scale. In order to demonstrate the value of some of these abandoned prospects and stir up interest in increasing the national gold production, the government has stimulated research. Experimental plants have been and are being established in various places, and tests on large quantities of ores are being carried out on a semicommercial basis. The Geological Survey of the State of Minas Geraes is very active in this line and the Federal Institution is also showing an increased interest in the matter. One of the lesser known gold-bearing regions of Brazil is in the vicinity of Lavras, in the State of Rio Grande do Sul. Gold was first reported from this region in the early part of the nineteenth century. In 1811, D. João VI sent an experienced prospector from Minas Geraes to investigate the validity of the reports. According to the reports of Baron Eschwege, he succeeded in extracting some 30,000 Oitavos (about 105 kg.) during the first few years, but the production costs exceeded the value of the gold obtained.

Jan 1, 1934

By Bennett R. Bates

Nowhere in the world has cone classification in closed-circuit grinding with tube mills reached as high a state of development as on the Wit-watersrand. In the development of the Far East section the necessity of fine grinding to obtain satisfactory residues gave rise to a situation with which the cone could cope only at a great sacrifice in efficiency of tube-mill grinding. H. A. White1 recognized the limitation of the cone in his study of the theory of tube milling as early as 1915, but it was not until Ewing, Davis and Willey2 carried out their tests at Springs Mines during 1920 that the advantages of mechanical classifiers were demonstrated. During the fall of 1924 the writer supervised a series of tests with Dorr classifiers undertaken by Mr. White, Consulting Metallurgist, at the mill of the Geduld Proprietary Mines, Ltd., Dersley, Transvaal (Far East Rand). The importance of classification to obtain efficient tube-mill grinding was thoroughly demonstrated. The installation of classifiers of the above type that followed the test confirmed the results of the experimental work. Tests with Cones, Straight Type and Bowl Classifiers The test at the Geduld mill was made to determine the relative grinding efficiency of a tube mill when grinding in closed circuit with cones, straight type Dorr classifier and Dorr bowl classifier. The efficiency of a tube mill, as expressed in this article, is based on the tons of minus 200-mesh material produced by the mill. The efficiency is also expressed in terms of tons of minus 90-mesh material produced by the mills to correspond to the standard practice on the Witwatersrand. The results given for the performance of the tube mills grinding in closed circuit with cones (Fig. 1) were taken from previous tests carried

Jan 1, 1926

By B. H. Sage

IN recent years there has been an increase of interest in the flow of gases at relatively high pressures. Hydrodynamic calculation of the energy losses in the flow of gases in conduits, as well as through the porous solid materials constituting natural petroleum reservoirs, requires a knowledge of the viscosity of the fluid at the pressure and temperature involved. Although there are numerous publications concerning the absolute viscosity? of hydrocarbon gases at atmospheric pressure, there appears to be little information available relating to the effect of pressure upon the viscosity of these gases. Vogel28 determined the viscosity of methane at 32° F. and atmospheric pressure. His measurements at 32° F. were later substantiated by the measurements of Rankine and Smith17 at 63° and 212° F. Ishida12 also reported values for the viscosity of methane at atmospheric pressure. Trautz and Kurz26 measured the viscosity of propane at atmospheric pressure, from 83° to 530° F., by the use of a short capillary tube. Rap-penecker18 determined the viscosity of gaseous isopentane at elevated temperatures. Day' made an accurate investigation of the effect of pressure upon the viscosity of n-pentane and isopentane at pressures from 2 lb. per sq. in. ? to the vapor pressure at 77° F. (approximately 9.8 and 13.3 lb. per sq. in., respectively). Earhart5 reported data upon the viscosity of several natural gases measured by the long capillary-tube method. The viscosity of air, at atmospheric pressure and 73.4° F., was measured by Harrington7 by the rotating-cylinder method. Kellstrom13 has recently made an elaborate investigation of the viscosity of air at atmospheric pressure. The latter work is perhaps the most accurate investigation of the viscosity of a gas that has been made. .

Jan 1, 1937

By R. F. Domagala

SOME of the results of a program designed to study the kinetics of transformation and related mechanical properties of prototype Zr-X binary alloys systematically are presented here. The object of this program was to provide a sound basis for a scientific approach to the realization of optimum properties in binary zirconium alloys. Alloys of Zr-Mo (eutectoid), Zr-Sn (peritectoid), and Zr-Ti (a and ß isomorphous) were prepared and studied. The data herein are confined to a presentation of the results of studying the eutectoid prototype alloys. The Zr-Mo phase diagram has been determined.&apos; A definitive metallographic study of isothermaily annealed samples prepared from high purity elements served to position a sluggish eutectoid reaction, ß?a + ZrMo2, at 780°C. The compositions of the phases involved in this reaction are: ß, 7.5 ±1 pct Mo; a, <0.18 pct Mo; and ZrMo2, 67.8 pct Mo. Inasmuch as a lower purity sponge zirconium was used in this work boundary placements were rein-vestigated with the less pure alloys. Materials and Procedures Hafnium-free sponge zirconium was used to prepare all ingots. The arc melted hardness of a small button of this zirconium was found to be Vpn 168. Chemical analyses conducted at Armour Research Foucdation are shown in Table I, High purity molybdenum sheet was used as the alloy addition. A typical analysis is shown in Table I. Several 200-g Zr-50 pct Mo alloys were made by arc melting. Crushed granules of this material were used to ensure inqot homogeneity Ailoy ingots were prepared by double melting techniques. First, three 5-lb ingots of each alloy composition were are melted in 2 nonconsumable electrode arc furnace. After melting. the ingots were ground to remove surface defects. A subse-

Jan 1, 1958

Flaubert, as we know, laid stress on the selection of the right word, le mot juste, the precise epithet, the word that belongs to the thing. A sentence, or even a paragraph, may be spoiled. by the use of a word that is not proper, that does not fit or is foreign to the meaning intended. An Australian mining expert is reported to have said: You have a property of considerable value, and what I saw warrants s good development of very rich cubicular galena, with gossan intermixed. &apos;Cubicular&apos; means &apos;belonging to a small bedroom&apos;, a &apos;cubicle&apos; being a sleeping compartment. He meant &apos;cubic&apos;, of course. This is a malapropism, and reminds me of the lady from Chicago that, on her return from Europe, said how much she had enjoyed the rural parts of France, because, among other things, it was "so delightful to hear the French pheasants singing the mayonnaise to the tune of the Los Angelus". It is impossible to amalgamate coal-tar thoroughly with the pulp in the agitating-tank. In metallurgy, &apos;amalgamate&apos; refers to the combination of mercury with one or both of the precious metals, forming an amalgam, which is an alloy of mercury with another metal. It differs from other alloys, such as brass or bronze, in being made without the aid of heat, inasmuch as mercury is molten at the ordinary temperature. The word comes to us from the Greek through Old French and means &apos;something soft&apos;. It is a mistake to use technical terms, having a specific meaning, for purposes that are foreign to that meaning. The writer of the quotation is not discussing any combination of metals; he is dealing with the physical process of mixing and is using &apos;amal-

Jan 1, 1931

By C. M. Wayman, M. A. Gedwill, C. J. Altstetter

Cobalt Whiskers were grown by the hydrogen reduction of CoBr,. The fcc = hcp martensitic trans-formation in these whiskers was studied using X-ray and metallographic techniques. Present theories of the fee + hcp martensitic transformation were ex-amined in the light of the present findings Experimental evidence for slip as a part of the transformation mechanism is presented. In the bulk form cobalt is known to undergo a martensitic transformation1 from an hcp to an fcc structure upon heating above about 430°C. Upon cooling, the reverse transformation starts at about 400°C, but does not go to completion except in single crystalline or coarse-grained samples, or upon plastic deformation. The transformation may be thought of as the shearing of close-packed atomic planes in such a way as to change the stacking sequence from ABCABC to ABABAB with a contraction normal to the shearing planes and an expansion in the planes,2 producing a c/a ratio slightly less than ideal. This restacking to give {0001) and (112) 11 (1010) can be accomplished by the passage of a shockfey partial dislocation over every other (111)f plane resulting in a theoretical shear of 19.47 deg. To date there has been no completely satisfactory explanation of how the partial dislocations are produced on the close-packed planes or propagated from plane to plane to give the correct stacking sequence. The object of the present research was to study some of the characteristics of the fcc to hcp transformation in geometrically simple single crystals. It was felt that whiskers of cobalt grown by halide reduction would be ideal specimens with which to study the transformation, because whiskers have the following desirable features: 1) are easily grown as fcc single crystals; 2) exhibit relatively simple geometries; 3) have comparatively low dislocation densities;

Jan 1, 1964

By Will Coghill

FLOTATION has been so closely allied with the sulfide minerals and their early and associated oily reagents that the term "oil flotation" has erroneously been applied to the entire flotation process. Today, the term "chemical flotation" might be used to advantage. Flotation literature has dealt primarily with the removal of sulfides from non-sulfide gangues, and the separation of one sulfide from another. Now, the application of the process to the separation of nonsulfide minerals is coming to the fore; and from the standpoint of the number of commercial minerals involved, the flotation of nonsulfides offers the larger field. Here, soap or soap-forming substances, such as the fatty acids and their derivatives, are used; hence there may well be a subdivision of the chemical flotation process called "soap flotation." Early experimenters learned that it was easy to form a froth or foam that would carry a part or all of the ore charge over the lip of the flotation machine; but this could not be regarded as flotation because of the lack of selectivity. Doubtless soap was one of the first reagents tried, and doubtless it was rejected on account of its gangue-carrying properties. Now this same gangue-carrying ability makes soap an acceptable reagent, for we are dealing with that, which among sulfides, is considered "gan-gue." As in the flotation of sulfides, so in the flotation of nonsulfides, the selective flocculation of the mineral and the dispersion of the gangue are the first objectives. In fact, these two phenomena epitomize flotation. They depend upon the unlike surface properties of the respective miner-als; and as long as the components of an ore have unlike surface proper-ties, a separation is possible, at least in theory. Often in nonsulfide flotation it makes little difference which mineral floats and which is depressed; generally only a separation is sought.

Jan 1, 1932

By H. S. Rankin, F. A. W. Davis, R. A. Laurence, L. L. McMurray, E. C. Houston

This paper is coodensed from several reports by members of the staff of the Minerals Testing Laboratory of the Tennessee Valley Authority, on a series of experimental tests in the beneficiation of barite of the Valley area. These experiments were conducted upon a large number of samples taken from several mines in three different districts. The area contains numerous producing deposits, nearly all of which are hampered by the high iron and silica content of the ores. Because of the small difference in specific gravity between the iron oxide and the barite, a gravity separation is generally poor. The removal of the iron thus offers a special problem. Some of the operators have turned to magnetic separation to meet the shipping requirements for less than one per cent iron. The present experiments were conducted to determine the application of decrepitation or flotation in simplifying the concentration of the barite by removing the iron oxide and silica in one operation. Practically all the barite marketed in the area has been as "off-color" crude. The bleaching studies were made to determine the bleach-ability of the ores to alleviate this inferior grading, placing them on the market as bleached barite. Geology Barite has been produced at many places in the Tennessee Valley area, and prospects and minor deposits are known at many other places, but practically all the production of barite in the Valley has been from the Sweetwater district of East Tennessee. Other leading areas of former production are the Tazewell-Russell counties areas of southwest Virginia, the Del Rio-Stackhouse district of East Tennessee and western North Carolina, and the Fall Branch district of upper East Tennessee. The areas described in this paper are those from which samples used in the concentration tests were obtained.

Jan 1, 1942