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By George J. Young

The nature of slimes handled in the treatment of gold- and silver-ores has been discussed in technical literature to a considerable extent. The subject of slime-filtration from the practical worker's stand-point has also received much comment, arid scattered through the literature of the subject are descriptions of many slime-filtration installations. Articles of this nature serve a valuable purpose and assist materially in the design of new and the improvement of old plants. The subject of the physics of slime-filtration has been touched upon to only a slight extent. The underlying principles are worthy of niore intensive study and experimeritation than they have received, and the main purpose of this paper is to present the results of such study and experimental work as will serve to make clear in part at least many of the principles which control the filtration of slime. Nature of Slime. Much has been written concerning an accurate definition of the term "slime," but no comprehensive definition seems to be gcnerally accepted. The reason for this is clear. A slime consists of at least three different substances, each, when separated, possessing distinctly different physical and to a certain extent chemical properties. These substances are extremely fine sand, a colloidal material which may bc and generally is in a coagulated condition, and a colloidal material which is in a non-coagulated condition. Suspending a slime in a relatively large volume of water by shaking and allowing sedimentation to take place, results in the fine sand settling out with comparative rapidity, followed by the coagulated material, which settles niuch more slowly and finally a certain portion remains

Jan 1, 1912

Report of the Secretary GENTLEMEN Herewith are transmitted reports from the Treasurer and of the principal standing committees of the Institute. To these special reports members are referred for details as to the year's work. Despite the unfavorable business conditions obtaining throughout the year, the Institute was able to carry on its various activities without curtailment and without drawing on the surplus accumulated through previous years. In fact, small additions were made to the Life Membership and various other funds. It is highly desirable that such additions should continue to be made, especially to the Life Membership fund, for reasons reported last year. At present, money must be used from current receipts in order to enable the Institute to fulfill its obligations to those who on joining the organization commuted their dues by a single payment. In addition, with the passage of years the number increases of those who have paid dues forty years or more and who, by reason of age or disability, are unable longer to practise their profession. These men have supported the Institute through their active professional life and it would be a pity to lose them as members through resignation or for failure to keep up their dues. In accordance with the By-laws the Board has authority to advance such members, on application, to the Honor Roll of Senior Members and to relieve them from further payment of dues. It has been the policy of the Board to do this liberally, but to keep up this, as well as to meet other obligations, it is necessary for money to be provided. It has been estimated by the Treasurer that nearly $50,000 additional should be placed in the Life Membership fund as soon as possible to meet these obligations without using current income and to that end it is necessary, not only to avoid running behind currently but to earn, if possible, some surplus each year. The small amount transferred to the Life Membership fund from surplus this year was, as a matter of fact, made possible by certain members paying personally bills that were properly chargeable to the Treasury. Such generosity is common among those active in Institute work and probably no year would have closed with a surplus except for it.

Jan 1, 1929

James Douglas will long be remembered as a distinguished mining engineer and metallurgist, as a scientist with broad vision, as an executive whose understanding of practical problems coupled with his knowledge of men and affairs enabled him to weld together great mining interests and to their service build railroads and bring power. More, he will be recalled as a philosopher and a writer of charm, a historian of no mean order, and one whose catholic tastes and enthusiasms led him into the fields of education, medicine and theology. His aim was to possess that which he considered made life worth while—friends and effectiveness in whatever task he undertook. In this aim he was successful to a degree exceeded by few, as thousands of his friends and associates could and can testify. Dr. Douglas was born on November 4,1837, at Quebec, Canada. His father, James Douglas, Sr., was a prominent physician and the leading surgeon of Canada. He also established the first retreat for the insane in the Dominion, the Quebec Lunatic Asylum, to which he devoted his services for years; The son followed in the footsteps of his father and studied medicine, not only in Canada but also in Scotland and in Germany. He entered the University of Edinburgh in 1855 but after two years at that institution returned to Canada and was graduated from Queens university at Kingston, Ontario, .with the degree of Bachelor of Arts. Later he went to Lava1 University, Quebec, and subsequently became professor of chemistry at Morrin College, Quebec. After he was graduated—at the time he considered his formal education completed—he traveled with his father in Europe and in the Orient; visiting Egypt, being especially interested in that country, several times. They gathered together an important archaeological collection which later was donated by them to the Metropolitan Museum of Art in the city of New York. James Douglas was also greatly interested in photography, a hobby in which he made use of his chemical knowledge. The writer can remember distinctly the descriptions he gave more than forty years ago in Arizona of the difficulties he encountered with the old wet photographic plates, especially while traveling in Egypt, when he prepared and used his own chemicals. In his humorous manner he told how he once discovered, in the nick of time, the nurse preparing to give the baby in the party a rub-down, using for that purpose the white, limpid

Jan 1, 1934

By Thomas Egleston

All industrial establishments whose operations depend upon chemical reactions use gases. In the simplest case the oxygen of the atmosphere, heated or not, as the case may be, is used, and in other cases, gases which are produced by a special apparatus of more or less complex composition. The manufacturer depends, for the success of his operations, entirely upon having these gases arrive at the right time, in the proper proportions, at the required temperature. It often requires but a slight variation in their composition to make a given process a success or a failure. In most cases the gas used is formed from fuel, and according as variations in its composition are produced by alterations in the manner of charging the grate, not only different, but often directly opposite, results are obtained. The great industrial question of the present time, and one upon which the prosperity of the world depends, is how to get the greatest amount of useful effect from fuel, whether the caloric is used directly or is transformed into horse-power. In almost all industrial pursuits this translates itself into the question of how to construct a fireplace and its adjuncts in such a way that the heat of the flame and of the products of combustion shall be made to produce a maximum effect. Unfortunately, until very recently, except by comparison, there was no means of ascertaining whether the loss of useful effect was 80, 40, or 20 per cent. of the total amount of fuel employed. It seems now strange that there should have been furnaces so constructed as to produce 20 per cent. of carbonic acid in the fireplace, but this has been proved by analysis to have been true. It does seem incredible that, notwithstanding the immense number and variety of furnaces used for different processes, and the great difference in kind, quality, and quantity of fuels consumed, there should formerly have been used for them all, the same stereotyped fireplace, varied only in its dimensions of height, length, and breadth. It is true that, with a good fireman, excellent effects may be, and have been, produced, but the manufacture is here, as in many other cases, dependent on the intelligence of the workman, a very uncertain reliance for capital to rest upon. The workman, unless he receives a prime for fuel saved, or is fined for excessive use of it, may be said

By P. Raffinot, M. Rey, V. Formanek, G. Sitia

Six years of laboratory study, followed by three years of mill operation treating more than 10,000 tons of ore, have established the flotation of oxidized zinc ores with fatty amines as an efficient process. Recently the method has been applied with success to partially oxidized sulphide ores. In this paper the authors give an account of their research and the milling results obtained in Sardinia since 1951. CONCENTRATION of oxidized copper and lead ores by flotation has been practiced for 30 years, but flotation of oxidized zinc ores has remained unsolved until a few years ago. This problem is, however, of great importance in mining districts where large tonnages of oxidized zinc ores exist in underground mines or in dumps. Some sulphide ores also possess a degree of oxidation high enough to justify recovery of oxide zinc minerals. Various attempts have been made to float the zinc carbonate, smithsonite. It is well known' that smithsonite can be collected with fatty acids, but as the predominant gangue constituents, limestone and dolomite. are floatable with the same reagents, fatty acids are difficult to use. Gaudin has shown,' on mixture of pure minerals, that smithsonite can be floated with higher xanthates, or better, with higher mercaptans. Another procedure, briefly mentioned by Davis," consists in sulphidizing the ore, activating the zinc carbonate with copper sulphate, and floating with ordinary xanthates. This process was attempted in the writers' laboratory in 1946, but results were erratic. It has since been taken up by Italian engineers and is in operation on certain types of ores. Two other research projects should be mentioned. In 1942 Erlenmeyer and others' floated synthetic mixtures of smithsonite and gangue minerals with hydroxyquinoline, an analytical reagent for zinc. On the other hand, Bunge, Fine, and Legsdin published in 19465 Some interesting results obtained on Missouri oxidized zinc ores. With sodium oleate as a collector and a combination of sodium hydroxide, sodium silicate, and citric acid as a limestone depressor, they secured, after four cleaning operations, a good grade of concentrate. With many ores this reagent combination lacks adequate selectivity. In 1939 M. Rey initiated a program of research on this important problem. Work was pursued first at the School of Mines in Liége, Belgium"' and later in Paris in the laboratories of Société Miniére et Mbtallurgique de Penarroya and Société Minerais et Métaux. Reagents used in the beginning were higher xanthates and mercaptans, later fatty amines. Sulphidization with sodium sulphide was found necessary. These conditions make possible the flotation of zinc carbonate and zinc silicate. Two milling plants were put in operation in Sardinia in 1950 and several others are now contemplated." ' It should be mentioned that unknown to the present writers McKenna, Lessels, and Peterson were

Jan 1, 1955

By Edward L. Fidler, Thomas E. Finch

Thin seam coal mining in the western US nominally equates to recovery of stray seams associated with thicker, major seams. The thin or stray seams encountered are generally recovered, but not in all cases. The alternative to extraction is, of course, spoiling. The majority of thin seams are encountered somewhere in the overburden above the major seam or in the parting between thick seams. Although some are true strays and appear anywhere in the geologic sequence, others might be classified as thin "rider" seams immediately above or below a thick seam and separated by some equally thin parting. For the purpose of this discussion, stray or thin seams are defined as those which are less than 1.2 m thick or represent less than 10% of the expected extractable coal. [Figure 1] is a graphic representation of typical thin, stray, or rider seams which actually appear in a western operation. Operationally, stray seams create irritating scheduling problems and require special handling techniques which do not always lead to efficient equipment utilization. Additionally, coal recovery from a thin seam is considerably less than the 95% usually recovered from thick seams. Higher recovery in thin seams leads to dilution problems, which depreciates Btu quality, and most western coals are not in a position to lose heating value. Thin western seams also undulate and pinch or swell more than thick seams, and this leads to more difficult recovery. Often they are associated with equally dark carbonaceous shales and visual selectivity is difficult at best during daylight hours. Resource Recovery Regulations Thin seam recovery in western mines is encouraged by both federal and state regulations and by the mining industry's concern for total resource recovery. [Table 1] lists the western coal states and their recovery regulations. The federal regulations are found in the Surface Mining Control and Reclamation Act of 1977. They state, "General performance standards shall . . . require the operation as a minimum to … conduct the surface coal mining operations so as to maximize the utilization and conservation of the solid fuel resource being recovered." Economic stimulation for thin seam recovery appears to be marginal or at the least controversial. Scheduling and operational problems often outweigh the nebulous profits created by engineering analysis. The only alternative to extracting thin seams occurring above major production seams is to strip directly through them and lose the resource to the spoil pile. Although this is not palatable to environmental emotions or resource promoters, it is the most simple expedient to operations people.

Jan 1, 1981

By P. E. Doherty, R. S. Davis

Sub boundaries and micropores, as well as certain other imperfections, may be revealed in aluminum by the formation of pits on the surface during cooling from elevated temperatures. The pits are attributed to the condensation of vacancies from supersaturated solution. This "vacancy pit" phenomenon has been used as an etching technique for studying the structure of aluminum specimens grown from the melt. Three fundamental structures were studied: stria-tions, cells, and dendrites. Two types of striations, as well as a crosswise structure are reported. Mic-roporosity is observed to occur in the cell walls on freezing. Subboundaries between primary, secondary, and tertiary branches are observed in dendritic growth. A special case is cited in which cellular growth suppresses the formation of striations. SMALL, well-defined pits have been observed to form on the surfaces of electropolished aluminum specimens during cooling from elevated temperatures.' This phenomenon was attributed to the condensation, from supersaturated solution, of vacancies at particular points on the surface. It was shown that the amount of cooling required for the formation of pits increased exponentially with decreasing holding temperatures in a way that was consistent with the thesis that a critical supersaturation of vacancies was required for the pits to form. Pits do not form in the vicinity of certain imperfections, namely, subgrain or normal graind boundaries, phase boundaries, certain surface irregularities, and pores. The width of the pit-free region increases with decreasing cooling rate. This observation suggests that the imperfections in question are effective sinks for vacancies and that the pit-free region around them is material that is not sufficiently supersaturated with respect to vacancies to nucleate the surface pits during cooling.

Jan 1, 1962

By John A. Emery, Frank G. Snyder

MINING geology has a threefold objective: to guide prospecting for new ore, to evaluate known orebodies as development risks, and to supply the detailed knowledge of ore structures necessary for more economical extraction. The role of geology in exploration is well established. This article will deal solely with orebody evaluation and the application of geology to development and mining problems as practiced by St. Joseph Lead Co. in the southeast Missouri district, which for many years has supplied approximately 30 pct of U. S. lead production. The primary concern of the present discussion is geology in the district, not geology of the district. The southeast Missouri district, locally called the Lead Belt, includes parts of St. Francois, Madison, and Washington counties. The first recorded mining was about 1720 at Mine La Motte in Madison County on surface showings of lead ore. Later discoveries near Bonne Terre, twenty-five miles to the north, led to extensive prospecting and underground mining. To date the district has yielded well over 8 million tons of pig lead, valued at more than $1 billion. By far the greater part of the lead production has come from an area of 50 sq miles, centering on the city of Flat River, as shown in Fig. 1. Role of Geology in Metal Mining The history of the use of geology in the older metal mining districts follows a simple consistent pattern that may be considered in terms of four distinct phases. Each geologic phase is a response to the economic status of the mining district; each has definite characteristics setting it apart from other phases; and each passes into the succeeding phase as the mining operation gradually exhausts the large, rich, easily discovered deposits and lives upon increasingly smaller, lower grade orebodies that are less easily found. The geologic phases and their major characteristics are as follows: Period of No Organized Geologic Program: During the early history of a great metal district ore is easily found by random prospecting and wildcat drilling. Many small operators are active, as profitable mining can be done with a relatively small capital outlay and a minimum of technical staff. Mining practice consists largely of sinking a shaft on an ore showing and following the ore in sight. When the ore is exhausted or becomes unprofitable to mine, the process is repeated on a new ore showing. The miners become familiar with certain ore habits and use this practical geologic knowledge to guide mining. The method is successful as long as large tracts of virgin mineralized area are available. This phase ends when small-scale mining methods are no longer profitable and the mines become consolidated into the hands of a few operators.

Jan 1, 1957

By M. Muskat, R. D. Wyckoff

The general problem of the simultaneous movement of water and oil in a connected sand is of considerable practical interest from two points of view. First, there is the situation usually described as "edge-water encroachment." Here the water in the sands contiguous to and flanking the oil sand begins to enter the latter as the oil is removed and the reservoir pressure declines. The physical questions involved concern an understanding of the mechanism of the advance of the water and its control, so as to aid the oil recovery rather than to hinder it. In so far as the entry of the water into the oil sand means at least the partial replacement of the oil from the region of the encroachment by the advancing water, it is quite appropriate to consider this type of situation as one of natural water-flooding. For the present discussion, however, we are primarily interested in the problem of artificial flooding. Here the water is deliberately injected into the oil sand with the intention of displacing the oil and removing it through prearranged output wells. For the practical development of such a procedure rather large areas are included in the flooding program and the injection and output wells are arranged in regular patterns or networks, which are felt to be most favorable for a high oil recovery. Although remarkable success has already been obtained in such flooding programs, especially in the Bradford field of Pennsylvania, essentially by the application of the lessons of practical engineering experience, a more thorough physical analysis of the problem appeared to offer promise of leading to results of some interest and value. Another phase of the problem, which stimulated both the experimental and mathematical analysis, is that it is susceptible in large measure to empirical field tests. It, is in itself but an example and illustration of the general theory of the flow of dead (gas-free) liquids through porous media, in which the authors have been interested for the last several years. From the point of view of its applicability to actual petroleum technology problems, however, water-flooding is a particularly favorable

Jan 1, 1934

By Persifor Frazer

The following notes on the Whopper and adjoining mines in the Gunnison district of Colorado mere made in the spring of this year. The time chosen for the author to visit the region was, unfortunately, the most unfavorable of an exceptionably unfavorable year. About the middle of May all the hill slopes, which at this period of the pear are generally covered with pasture, were thickly covered with snow. The unusually large precipitation of this Tear caused loacal mountain torrents at every few hundred feet, which wore away the oft foothills into gulches, gouged great chasms out of the roads, and transformed miles of usually dry soil into dangerous quagmires. Travel was totally interrupted for weeks, except on horseback or afoot, and even then with great difficulty and some danger. The Whopper mine is situated on the Whopper Mountain, about two miles from the headwaters of Rock Creek, and on the right hank of that stream. The Whopper Creek flows into Rock Creek horn the east, and, by a precipitous descent, offers excellent facilities for its utilization as a source of power. This stream, which pours past the picturesque Whopper Cabin about thirty tons of water a minute, has a fall of 100 feet in 400 yards, and is said to be a stream of some size, even at the seasons of the year when drought prevails. The Whopper claim extends down the hill a distance of about 250 feet to its intersection with the Whopper Creek (on the other side of which is a small tunnel on its extension called the "Teller") and over the steep hill northwest to the limits of the claim about 1250 feet. The part of the mountain in which this mine is situated is remarkable for its splendid forest, the spruce, fir, and quaking asp covering the mountain-sides with a green growth of valuable timber. The distance from Gothic City to this mine is about eight miles along the valleys of East River and Rock Creek, and on the divide which separates them. The elevation of Gothic City is given from the engineer's notes as 9500 feet above sea-level, and the mean of several observations with a Beck watch-barometer made the elevation of Whopper Cabin (which is about fifteen feet above the floor of the Whopper upper tunnel) about 1260 feet above Skiles's Cabin in Gothic City. The record of this instrument must, how-

Jan 1, 1881

By David E. Hyatt, Christopher H. Cox, Franklin T. Davis

INTRODUCTION The composition of water used in the flotation process has always been of primary interest to the flotation metallurgist. It is by alteration of the chemistry of the water introduced to the process that flotation separation is effected. In only a few cases has it been necessary to treat available water prior to use in the process. In the past, flotation tailings were treated for the removal of solids via the tailings dam and water decanted from the dam was either recirculated to the process or discharged to the surface water system. The choice of recirculation or discharge was based upon water availability, effect of recycle water on the process, and economic considerations. The Federal Water Pollution Control Act Amendments of 1972 have charged the United States Environmental Protection Agency with establishing effluent limitations from point sources of discharge into the navigable water of the United States. A detailed study, sponsored by EPA, of the water of ore processing plants took place in 1974 and 1975 and guidelines for these plants will presumably have been published by the time this paper has been presented(1). The action of many of the individual states preceded the EPA in this attempt to regulate the quality of the water discharged from industrial point sources. Even with recycle of tailings water, some water is discharged from tailings dams into the substrata and at least one state is currently preparing guidelines for the quality of water discharged into the substrata.

Jan 1, 1976

By Carlos A. Aranda

The Smelting and Refining Department of Cerro de Pasco Corporation is located at La Oroya at an altitude of 3,720 meters (12,205 feet) in the Peruvian Andes. Producing lead, zinc and copper as well as twelve by-product metals and chemicals, the smelter is among the world's most complex. With the intake of high-bismuth ores in 1934, electrolytic lead refining by a modified Betts process was piloted and the plant went into commercial production in 1937 at a nominal capacity of 100 M.T. per day. After expansions in 1950 and 1963, nominal capacity has increased to 250 M.T. per day. Anodes spaced at 10.8 cm centre to centre and starting sheets are both set into the cells by overhead cranes. The asphalt-lined concrete cells are arranged in a Walker side-by-side configuration, and the electrolyte, circulating at 13 l/min./cell, is a solution of locally-produced hydrofluosilicic acid and lead fluosilicate. The corrosion cycle is limited to four days due to high impurity content of the bullion, which has successfully been treated at contents of up to 9% impurities. The cathodes are melted, drossed, and cast into blocks and pigs assaying 99.997 + % lead. The anodes with the blanket of slime adhering, are washed with electrolyte and condensate makeup water to remove the concentrated lead fluosilicate entrapped in the slimes. The slimes are then removed with high-pressure water sprays, centrifuged and sent to another plant for recovery of silver, gold, bismuth, selenium, tellurium, and antimony.

Jan 1, 1970

By T. Prof. Egleston

ALL industrial establishments whose operations depend upon chemical reactions use gases. In the simplest case the oxygen of the atmosphere, heated or not, as the case may be, is used, and in other cases, gases which are produced by a special apparatus of more or less complex composition. The manufacturer depends, for the success of his operations, entirely upon having these gases arrive at the right time, in the proper proportions, at the required temperature. It often requires but a slight variation in their composition to make a given process a success or a failure. In most cases the gas used is formed from fuel, and according as variations in its composition are produced by alterations in the manner of charging the grate, not only different, but often directly opposite, results are obtained. The great industrial question of the present time, and one upon which the prosperity of the world depends, is how to get the greatest amount of useful effect from fuel, whether the caloric is used directly or is transformed into horse-power. In almost all industrial pursuits this translates itself into the question of how to construct a fireplace and its adjuncts in such a way that the heat of the flame and of the products of combustion shall be made to produce a maximum effect. Unfortunately, until very recently, except by comparison, there was no means of ascertaining whether the loss of useful effect was 80, 40, or 20 per cent. of the total amount of fuel employed. It seems now strange that there should have been furnaces so constructed as to produce 20 per cent. of carbonic acid in the fireplace, but this has been proved by analysis to have been true. It does seem incredible that, notwithstanding the immense number and variety of furnaces used for different processes, and the great difference in kind, quality, and quantity of fuels consumed, there should formerly have been used for them all, the same stereotyped fireplace, varied only in its dimensions of height, length, and breadth. It is true that, with a good fireman, excellent effects may be, and have been, produced, but the manufacture is here, as in many other cases, dependent on the intelligence of the workman, a very uncertain reliance for capital to rest upon. The workman, unless he receives a prime for fuel saved, or is fined for excessive use of it, may be said

Jan 1, 1874

By Jesse O. Betterton

Recently some experimental work was conducted by the author in connection with the direct leaching of certain zinc ores with sulfuric acid with the object of subsequently recovering the zinc by electrolysis. The ores contained relatively large quantities of soluble silica, making it necessary to evolve special methods for handling the silicate solutions resulting from a leach of the ore, and also for the final removal of the silica before electrolysis. The problem was complicated by the presence of vanadium in the ore, the commercial recovery of which was very desirable. This paper, however, deals only with the silica phase of the problem. The zinc in the ore occurs in the form of a silicate (hemimorphite) and, to a very small extent, as the phosphate (hopeite) and carbonate (calamine); the vanadium is found as descloizite and vanadinite but mainly as descloizite. The experimental work was done in a plant producing 50 lb. of zinc = daily, in which the complete cycle of operations, including the final electrodeposition of the zinc, was performed continuously for one year. Some of the conclusions given here are the result of the operations in -this plant; the others are from laboratory tests inaugurated both as a guide to the plant operations and, in certain cases especially, to determine the limits in question. The practice in the 50-lb. zinc plant was to direct leach the ore crushed to pass 40 mesh, with spent electrolyte from the cells containing approximately 3 per cent. zinc and 10 per cent. free acid. This resulted in an acid leach solution and an ore residue. The acid leach solution was ' subjected to a special treatment for subsequent removal of vanadium; then the silica and vanadium in solution were precipitated together and removed as a "silica residue" by pressing through an ordinary plate and frame press. The next step was to treat the filtrate from the silica residue with zinc dust as a final purification step before it went to

Jan 1, 1923

By Persifor Frazer

THE following notes on the Whopper and adjoining mines in the Gunnison district of Colorado were made in the spring of this year. The time chosen for the author to visit the region was, unfortunately, the most unfavorable of an exceptionably unfavorable year. About the middle of May all the hill slopes, which at this period of the year are generally covered with pasture, were thickly covered with snow. The unusually large precipitation of this year caused local mountain torrents at every few hundred feet, which wore away the soft foothills into gulches, gouged great chasms out of the roads, and transformed miles of usually dry soil into dangerous quagmires. Travel was totally interrupted for weeks, except on horseback or afoot, and even then with great difficulty and some danger. The Whopper mine is situated on the Whopper Mountain, about two miles from the headwaters of Rock Creek, and on the right bank of that stream. The Whopper Creek flows into Rock Creek from the east, and, by a precipitous descent, offers excellent facilities for its utilization as a source of power. This stream, which pours past the picturesque Whopper Cabin .about thirty tons of water a minute, has a fall of 100 feet in 400 yards, and is said to be a stream of some size, even at the seasons of the year when-drought prevails. The Whopper claim extends down the bill a distance of about 250 feet to its intersection with the Whopper Creek (on the other side of which is a small tunnel on its extension called the "Teller ") and over the steep hill northwest to the limits of the claim about 1250 feet. The part of the mountain in which this mine is situated is remarkable for its splendid forest, the spruce, fir, and quaking asp covering the mountain-sides with a green growth of valuable timber. The distance from Gothic City to this mine is about eight miles along the valleys of East River and Rock Creek, and on the divide which separates them. The elevation of Gothic City is given from the engineer's notes as 9500 feet above sea-level, and the mean of several observations with a Beck watch-barometer made the elevation of Whopper Cabin (which is about fifteen feet above the floor of the Whopper upper tunnel) about 1250 feet above Skiles's Cabin in Gothic City. The record of this instrument must, how-

Jan 1, 1881

By W. A. Koehler, M. E. Hinkle

THE oxidation of pyrites and marcasite in coal-mine strata to produce discolored acid mine drainage has long been explained by chemical reactions occurring in three stages: 1. The iron sulphide minerals are oxidized by air in the presence of water to produce a nearly colorless solution of ferrous (iron) sulphate and some sulphuric acid. 2, The ferrous sulphate and part of the sulphuric acid combine with additional oxygen to form ferric (iron) sulphate. 3. The ferric sulphate hydrolyzes to form a reddish-brown precipitate and additional sulphuric acid. Nevertheless, chemical data alone are not sufficient to explain all observed facts. The first stage seems to proceed more slowly in the chemical laboratory than in nature. The second and third stages normally occur to a marked extent within a few days with raw mine water. However, the visible discoloration that characterizes these latter stages will not develop for months if the mine water is sterilized. By means of bacteriological techniques, two organisms have been isolated from acid coal-mine drainage. These are believed to have a part in promoting the chemical reactions summarized above. One organism is considered to be Thio-6aciZZus thiooxidans, which is known to be able to convert elementary sulphur or sodium thiosulphate to sulphuric acid. Its relation to the formation of acid mine drainage has not Yet been established. Apparently it does not Promote the oxidation of ferrous iron compounds in mine drainage to the ferric state. The second organism has not been identified by name but is described as " Gram negative, non-spore-forming rods approximately 0.4 micron wide by 0.8 to 1.0 micron long." A pure culture of this when added to sterile mine water will cause the latter to become amber and develop the typical rusty precipitate. However, it has not been found to convert sulphur compounds to sulphuric acid. Further research is planned to determine whether or not these microorganisms play a significant part in the first stage of oxidation whereby pyrites and marcasite minerals go into solution. Some of the conditions found in abandoned sections of coal mines, such as a reduced Percentage of Oxygen and increased percentage of carboll 'dioxide in the air, as well as the existing temperature and acidity ranges, will be tolerated by and may even be favorable to these organisms. Acid Coal Mine Drainage Acid coal mine drainage has been the concern of coal mine operators, industrialists, sportsmen and public officials for many years. The amount of acid flowing into our streams in the coal-producing areas varies considerably from mine to mine and from

Jan 1, 1949

By Paul T. Allsman

1.1-1. Current Status. The history of surface mining is essentially that of mining coal, copper, and iron ores, and the nonmetallic minerals--clays, gypsum, phosphate rock, sand, gravel, and stone. Table 1.1-1 is a comparison of the estimated world production of crude metallic and nonmetallic ores and coal with that of the United States for 1964, in short tons. It includes an estimate of the quantity produced by surface mining methods. Two-thirds of the 8.8 billion tons are mined from surface, ranging from a third of the coal, half the metallic ores, and nearly all clays, stone, sand, and gravel. In the United States, production by surface methods parallels that of the world with two major exceptions: 74% of copper ore and 90% of usable iron ore are mined from the surface, whereas outside the country less than 40% of copper ore and only 50% of usable iron ore are mined from the surface. In surface mining of both metallic ores and coal, much waste is stripped, but in mining nonmetallics the ratio between waste and ore is small. Assuming that the stripping ratio for surface mining in the United States will apply equally to world production, it is estimated on a weighted basis that over 21 billion tons of waste, or a total of nearly 27 billion short tons of material, are mined annually in the world by surface methods. Data are not available to confirm the assumption for waste stripping outside the U.S., but the estimate expresses an order of magnitude that is worth noting. Table 1.1-2 shows the materials-crude ore, coal, and waste-mined by surface methods and the relation to total mined by both surface and under- ground methods in the United States during 1964. Eighty-two percent of all crude metallic and nonmetallic ores and coal was mined from the sur- face, including 82% of metallic, 96% of nonmetallic ores, and 35% of coal. Copper and iron ore comprise 83% of the metallic ores mined from the surface, and clays, gypsum, phosphate rock, sand, gravel, and stone

Jan 1, 1968

By Carl Floe

A NUMBER of proposals have been made for the hydrometallurgical recovery of copper from flotation concentrates, but as yet no process has been developed that has demonstrated an ability to compete with the present smelting methods under ordinary conditions. The treat-ment of copper concentrates by hydrometallurgical methods is in general similar to that used in the present electrolytic zinc process and involves roasting, leaching with H2S04 solution, separation of solutions, control of impurities and electrodeposition. While many of these steps are simpler and more readily carried out for copper than for zinc, a number of inherent difficulties have prevented the general adoption of the process. To compete with smelting, the following problems must still be con-fronted, although many solutions for their have been proposed: (1) con-duction of the roast in such a way that leaching will give an extraction of copper comparable to that obtained by smelting; (2) regulation of the ferric iron content of the solutions during electrolysis; (3) disposal of the excess acid regenerated from the sulphates formed in roasting; (4) eco-nomical recovery of the precious metals from the leach residues. The roasting problem is largely one of preventing the formation of copper ferrites, CuO.Fe2O, and Cu20.Fe2O3, which are quite insoluble in dilute sulphuric acid. These ferrites are apparently formed' to a small extent even at low temperatures and above 650° C. their formation is rapid1. While it is possible to carry out laboratory roasts in such a way that less than 5 per cent of the total copper is present in the insoluble ferrite form, a closer temperature control is required than can readily be obtained in industrial furnaces. The flash" roasting effects and consequent high temperatures that occur as the calcine falls from hearth to hearth in the ordinary multiple-hearth roaster are probably largely responsible for the inevitable formation of some ferrites. The result is that in a commercial plant the extraction of copper would not average more than 90 per cent in a single 10 per cent H2SO4 leach. This is

Jan 1, 1937

By R. G. Webber, F. C. Langenberg

During the course of some magnetic investigations which the authors have under way, six bars of 0.43-carbon steel were tested, a permeameter designed after the Hopkinson yoke type being used. The results obtained were of some interest and although far from complete serve at least to show the necessity for a careful investigation of the previous history of the samples under study as well as the chemical composition. A steel of given chemical composition may assume a great variety of structures, depending on its treatment. Professor Sauveur has devised a very clear and effective means of illustrating this point. The accompanying microphotographs show some of the possible structures assumed by a 0.30 carbon steel (Fig. 1). It is now a well-established fact that a structural change is accompanied by changes in the tensile strength, elastic limit, hardness, etc., and it seems reasonable to assume also, a change in the magnetic properties. Six bars of a 0.43-carbon steel were used, all the bars being taken from the same rod and treated as follows: Bar 1. Heated to 1,100° and cooled in the furnace. Bar 2. Heated to 1,000° and cooled in the furnace. Bar 3. Heated to 900° and cooled in the furnace. Bar 4. Heated to 1,000° and cooled in air. Bar 5. Heated to 900° and cooled in air. Bar 6. Untreated. The bars were then turned to 13 mm. diameter and tested by the Hopkinson yoke method. After testing, three specimens were taken from each bar, one from each end and one from the middle. The homogeneity of the bars was tested in this manner and in no instance could any difference in structure in the three specimens1 be detected. Bars 1 to 3 inclusive are pearlitic in structure. The white areas are ferrite (iron with certain impurities in solution) and the dark areas pearl-

Jan 1, 1915

By Charles Russell

PRESSURES developed by the coal during the coking process have been responsible for serious trouble to many companies that operate or build by-product coke ovens. The insidious nature of this trouble is indicated by the fact that oven operators, unless they have ascertained the charac-teristics of the coals they use, cannot determine the existence of dangerous pressures until after the damage has been done. A rather popular mis-conception is that ease of pushing of the charge at the completion of the coking period indicates that no dangerous pressure has been developed, but this is far from the truth; pressures developed during the coking period are often completely dissipated by the shrinkage of the charge in the completion of coking, and so any criterion based on the ease of pushing is futile. However, methods of testing coals are available that will definitely distinguish the dangerous coals from those that are safe, and such methods have been brought to a high degree of certainty. The operator should take no risk that involves either a lack of knowl-edge of the behavior of coals during coking or the failure to believe that certain of the coals or coal mixtures can cause damage to the oven struc-ture. This merely tends to minimize the problem and leads to claims that coking coals of all kinds may be carbonized with no danger of damage to the oven structure provided some particular kind of by-product oven is used. This lack of appreciation of the true situation is in itself one of the main factors leading to damage of coke-oven structures. Coals that develop more than a certain safe pressure cannot be used in by-product coke ovens without causing damage to the side flue walls. The following paper presents a highly certain method for the measure-ment of the pressures developed during the carbonization of coal-a method that is the culmination of many years of work on the problem in which a number of methods for the purpose were investigated and used. While actual pressures found may appear to be small when expressed in pounds per square inch, the number of square inches in each oven wall is so large that the total pressure on the oven wall becomes an enormous load.

Jan 1, 1939