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By F. F. Lines

IT is not the intention of the writer to enter into a discussion of the relative merits of the duplex process as compared with the straight scrap and pig iron process, working under the same conditions, but rather to present in a general way several modifications of the former process, and then describe the method adopted by the Maryland Steel Co., as best suited to local conditions, and also to meet the metallurgical problem presented in the removal from the iron of an unusual constituent-chromium. The principal factors to be considered in deciding whether or not duplexing should be employed are: (1) Chemical constituents of pig iron. (2) Variety and quantity of steel to be produced. (3) Relative cost of pig iron and scrap. (4) Regularity of operation. (5) Capital to be invested. (6) An existing Bessemer plant. Having decided to adopt the duplex process, several combinations may be used, viz.: (1) Acid-lined converter with basic open hearth. (2) Acid-lined converter with electric furnace. (3) Basic-lined converter with basic open hearth. (4) Basic-lined converter with electric furnace. (5) Basic open hearth with electric furnace. The combination of an acid-lined converter with a basic open-hearth furnace is the one most commonly employed, and as it is the one best adapted to the conditions encountered at the plant of the Maryland Steel Co., we will briefly outline the advantages and disadvantages of the different methods of working.

Jan 4, 1915

By William F. Blake

In September I contributed an article upon Columbite in the Black Hills of Dakota to the American Journal of Science. I had not at that time seen the paper by Professor Charles A. Schaeffer, of Cornell University, upon the occurrence of tautalite in the same region," or I would have gladly made reference to it. His analysis, proving the entire thence of columbic acid, shows that the specimen he analyzed, at least, should be called tantalite, and not columbite, if the distinction between these two closely related species is to be maintained. It is hard to say where the line is to be drawn, in such cases, between two minerals, when the specific characters and the composition are so nearly the same. If the name is to be determined by the relative amounts of tantalic and columbic acids, what shall we call the mineral when these acids are present in nearly equal quantities? Preference was given in this case to the name columbite, for the reason that the specific gravity, as ascertained by the ordinary scales at command, was nearer 6 than 7. As Professor Schaeffer had only one fragment by post, while I had an abundance from many places, it may yet be found that columbic acid predominates in some of the specimens. I therefore use the name columbite or tantalite indifferently. With this explanation I proceed to give a few observations upon the occurrence of the mineral with the tin-ore of the Black Hills. There are two localities, especially, where the mineral is found in the same dike or vein as the cassiterite: 1. at the Etta mine; 2. at the Bob Ingersoll claim. At the Etta it occurs in close association with albite and feldspar in crystals from one to four or five inches broad, and from one-quarter of an inch to three inches thick. It is not in contact with or mingled with the cassiterite, and each call be

Jan 1, 1885

By Henry M. Howe

in Cast-Iron. It has been generally accepted that the presence of silicon in cast-iron leads to the formation of graphite; and this has been explained by saying that the silicon lowers the solvent power of iron for carbon at and somewhat below the freezing-point, so that, in the presence of silicon, the iron is unable to retain in solution or combination the whole of the carbon with which it has united while molten, and therefore expels the excess of carbon in the form of graphite, during and immediately after solidification. Probably the best way to study this question would be to examine pure cast-irons, i.e., those containing nothing but iron, carbon and silicon, which at the same time should have been saturated with carbon when molten. But the data for such a study are not at hand; so we must turn to commercial pig-irons as they are made in the blast-furnace, and before their composition has been changed by remelting. Much evidence has been offered of late, tending to oppose the theory of the action of silicon above set forth. Some of this evidence will be examined here. 1. Mr. Bachman's Results. In particular, Mr. F. E. Bachman† has published a collection of analyses of cast-iron, in which the proportion of graphite at first appears to be nearly independent of the proportion of silicon present. Thus, in his Table LI., we find that with pro-

Jan 1, 1901

By J. F. K. Brown, E. E. Roecker

For three years The Hudson Coal Co. has used egg anthracite instead of coke in its foundry cupola. It has long passed the stage of being told it cannot be done—the metal would be cold, of poor quality, or the speed of operation would be low. From observation, from use and from test. we know that our metal is about average; the cast iron invokes no adverse comment from the machine shop and the speed suits our foundry requirements. We have there-iore resolved into practice anthracite combustion processes in an industrial furnace formerly using coke, under conditions suitable to our needs. When it comes to translating what we know into use in another cupola, however, where operating conditions may be different, or to explaining why, with seemingly the same conditions in our own cupola, we have attained sometimes a temperature of 2800° in the metal and at another time 2600°, or a speed of 5 tons per hour against 2 35 tons per hour, we cannot do it. We cannot do this because there seems to be an unbridged gap between laboratory ideas on combustion and practical ideas on com-bustiqn, which we have been unable to cross in terms understandable to us as practical consumers. This gap or bridge centers around the problem of how combustion actually takes place; and we believe it is controlled by two factors: (I) the character of the surface of the fuel and (2) the space provided and needed within which the oxygen of the air is allowed to or can act on that surface. It has long been contended on behalf of coke that porosity is an important factor in combustion, although, admittedly, there are two schools of opposing thought on this question, as revealed in technical literature. It has been understood generally that a light, porous coke is the best metallurgical fuel because there are more square inches of carbon exposed to the blast of air, therefore more useful carbon-dioxide reactions can take place in the given space between the entrance of the air and the point where useful work is done. It is now our general idea that the heavier and the harder the coal, the better the metallurgical fuel, provided the surface of that fuel is suitable for fast reaction with the oxygen. Time and Space A cupola is loaded in layers of fuel and iron. The horizontal line where the first charge of iron rests on the coal is the top of the bed coal. With us that is 22 in., usually, above the tuyeres where the air enters. This means 600 lb. of coal. Every subsequent coal layer is 100 to 125 lb. of coal, and that 100 to 125 lb. of coal melts 1000 lb. of iron at around 2700° in the ladle. This quantity of coal represents a 3-in. layer spread across the cupola. The question arises: If this 3 in. of coal will melt 1000 lb. of metal, why was it necessary to use 600 lb., or 22 in., of coal beneath and between the first charge of iron and the air entrance?

Jan 1, 1944

By E. E. Roecker, J. F. K. Brown

For three years The Hudson Coal Co. has used egg anthracite instead of coke in its foundry cupola. It has long passed the stage of being told it cannot be done—the metal would be cold, of poor quality, or the speed of operation would be low. From observation, from use and from test. we know that our metal is about average; the cast iron invokes no adverse comment from the machine shop and the speed suits our foundry requirements. We have there-iore resolved into practice anthracite combustion processes in an industrial furnace formerly using coke, under conditions suitable to our needs. When it comes to translating what we know into use in another cupola, however, where operating conditions may be different, or to explaining why, with seemingly the same conditions in our own cupola, we have attained sometimes a temperature of 2800° in the metal and at another time 2600°, or a speed of 5 tons per hour against 2 35 tons per hour, we cannot do it. We cannot do this because there seems to be an unbridged gap between laboratory ideas on combustion and practical ideas on com-bustiqn, which we have been unable to cross in terms understandable to us as practical consumers. This gap or bridge centers around the problem of how combustion actually takes place; and we believe it is controlled by two factors: (I) the character of the surface of the fuel and (2) the space provided and needed within which the oxygen of the air is allowed to or can act on that surface. It has long been contended on behalf of coke that porosity is an important factor in combustion, although, admittedly, there are two schools of opposing thought on this question, as revealed in technical literature. It has been understood generally that a light, porous coke is the best metallurgical fuel because there are more square inches of carbon exposed to the blast of air, therefore more useful carbon-dioxide reactions can take place in the given space between the entrance of the air and the point where useful work is done. It is now our general idea that the heavier and the harder the coal, the better the metallurgical fuel, provided the surface of that fuel is suitable for fast reaction with the oxygen. Time and Space A cupola is loaded in layers of fuel and iron. The horizontal line where the first charge of iron rests on the coal is the top of the bed coal. With us that is 22 in., usually, above the tuyeres where the air enters. This means 600 lb. of coal. Every subsequent coal layer is 100 to 125 lb. of coal, and that 100 to 125 lb. of coal melts 1000 lb. of iron at around 2700° in the ladle. This quantity of coal represents a 3-in. layer spread across the cupola. The question arises: If this 3 in. of coal will melt 1000 lb. of metal, why was it necessary to use 600 lb., or 22 in., of coal beneath and between the first charge of iron and the air entrance?

Jan 1, 1944

"Coulter's Rainbow and Crooked Falls are situated about five miles below the City of Great Falls. Coulter's, the first of the series in the course of the river, is unimportant and has been submerged by the Rainbow dam. Next below Coulter's is the Rainbow Falls, 47 feet in height. Following Rainbow Falls is the Crooked Falls, 21 feet in height. The power developed at this point is such that the one clam, power house and tail-race utilize the power from all three of the above falls.The development at Rainbow was started October, 1908, and completed July, 1910. It has a total capacity of 21,000 k-w. in generators, and 36,000 h-p. in waterwheels, and operates at 105 foot head. The general scheme of development is typical of what may be called standard practice in the west for plants of medium head, and consists of a low diverting clam, a double pipe line feeding into a balancing reservoir near the plant, and individual pen-stocks supplying the turbines from this reservoir.The dam is a rock-filled crib structure 1,146 feet long and 29 feet high, the up-stream side of which slopes at such an angle that the stability of the clam is assured even under the greatest floods, the weight of the water acting to hold it down, so that the higher the flood the greater the stability. The down-stream side is also sloping and tapers off into a long apron so designed as to take care of any overflow which may occur without shock or commotion. The clam is founded on solid rock throughout its entire length."

Jan 1, 1913

By B. F. Fackenthal

One of the practical questions presented to the blast-furnace manager, with regard to which little help can be obtained from existing technical literature, is the manner of filling and blowing-in. This operation is often performed according, more or less, to traditions which have come down from earlier practice, and which, if not positively detrimental when followed with the large modern furnace, may at least be greatly improved, just as the running of the furnace itself, while in blast, has been improved. It is not necessary, as many of the old furnace-men believed, to make a lot of white or silver-gray iron at the start, or to spend many weeks, or months even, in bringing the furnace to its normal burden. It has seemed to me that the publication of carefully-recorded data of practice on this point may be interesting to the members of the Institute engaged in the management of blast-furnaces. The enlarged blast-furnace at the Durham Iron Works, Riegelsville, Pa., owned by Messrs. Cooper & Hewitt, of New York City, was first put in blast February 21, 1876, since which time it has made seven blasts, and is now running on the eighth. A description of the furnace-plant, together with a record of the fifth blast, was given in my paper read at the Chattanooga meeting, May, 1885 (Transactions, xiv., 130). After some of the early blasts the furnace-lines underwent considerable change, and I have thought best to accompany this paper with drawings showing the lines and the tuyere-arrangement (see Plates I. and II.), and to give also the following summary of the conditions and results of each blast. During the first and second blasts no coke was used, and the furnace ran very irregularly, showing a constant tendency to scaffold, which was attributed, in great part, to the small hearth and other defective lines. The large proportion of air required at this furnace is accounted for by the fact that the engines are defective, and do not deliver into the furnace the amount of air indicated by the pistondisplacement.

Jan 1, 1890

By E. P. Jennings

The iron-ore deposits of Iron county, Utah, which rival those of Lake Superior in extent, are situated 275 miles south of Salt Lake City, and 25 miles south of Lund, a station on the San Pedro, Los Angeles & Salt Lake railroad. The range of hills containing the deposits has a general NE-SW. strike, and rise from a few hundred to 2,000 ft. above the Escalante desert, the ore being included in an area of 5 by 20 miles. The basal rock of these hills is diorite-porphyry. The flanks of the range are covered with limestone supposed to be of Carboniferous age, underlain in some localities by quartzite. Both formations are conformable to the porphyry, and are the remnants of beds that formerly covered the highest peaks, but have been removed subsequently by erosion. In the central and southern parts of the range, beds of Cretaceous sandstone rest unconformably on the eruptives. Rhyolite-flows occur to the south and southeast of the iron-ore deposits; and dikes and sheets of post-Tertiary lava are common. With the exception of a few springs, the range is destitute of water. Sage-brush, stunted cedars and the common desert-bushes constitute the only vegetation. Large beds of coal of poor quality occur in Cretaceous sandstones 15 miles east of the ore-deposits.

Jan 1, 1905

A SPRING meeting is to be held at Cleveland this month under the joint auspices of the Iron and Steel Committee and the Ohio Section with the cooperation of the neighboring sections in Pennsyl-vania, Illinois, and the other States of the Great Lakes region. The discussions will be focused on just one subject, that of manganese, but will cover that thor- oughly as is indicated by the following list of papers. TECHNICAL PROGRAM Some Political Aspects of the World Manganese Situa-tion. By C. K. Leith, Professor of Geology, Uni-versity of Wisconsin, Madison, Wis. Manganese Resources in Relation to Domestic Con-sumption. By J. V. W. Reynders, Consulting En-gineer, New York, N. Y. Manganese Deposits of the' Gold Coast, Africa. By Sir Arthur E. Kitson, Director of the Geological Sur-vey of the Gold Coast, London; with Notes on the Petrology of Certain Associated Manganese Silicate-bearing Rocks. By Maj. N. R. Junner. Reserves of Lake Superior Manganiferous Iron Ores. By Carl Zapffe, Manager, iron ore properties, North-ern Pacific Railway Co., Brainerd, Minn. Iron Manganese Alloys Low in Carbon. By. Sir Robert Hadfield, Hadfields, Ltd., London. Manganese in Non-ferrous Alloys. By M. G. Corson, Consulting Engineer, New York, N. Y. Importance of Manganese in the Steel Industry. By H. M. Boylston, Professor of Metallurgy, Case School of Applied Science, Cleveland, Ohio. Minnesota Manganiferous Iron Ore in Relation to the Iron and Steel Industry. By T. L. Joseph, E. P. Barnett and C. E. Wood of the North Central Min-ing, Experiment Station, U. S. Bureau of Mines, Minneapolis, Minn. Representatives of the leading steel companies, the Army, the Navy, the Geological Survey, Bureau of Mines, and leading technical societies will be present and a lively discussion of the various papers is already assured. Nearly 14 pounds of manganese is needed for every ton of steel made. Estimates indicate that the total reserves of ore in this country suitable for making ferro would hardly supply domestic requirements for ten years, even if it could all be mined in that time. The grade of ore called for by present practice must come from abroad. The present tariff policy of this country is stated to cost industry $8,000,000 in order to force production of manganese ore to the extent of $600,000. What is the wise thing to do? Should a stock be accumulated? If so, how? Is it feasible to change practice and use low-grade ore or to beneficiate the ores of this grade and meet our requirements? What progress is being made in this direction? ,These and similar questions are raised in the various papers that have been submitted and will be open for dis-cussion.

Jan 3, 1927

By Foster Fraas

That variations in the humidity of the air and in the moisture content of a mixture of broken solids being separated electrostatically cause trouble is not new.' Much of the reputation for unreliability commonly ascribed to the electrostatic separation processes is probably due to this one factor alone. Some operators dry thoroughly before separating; and while this is good in many instances, there are others in which it is not the remedy for trouble. Some mixtures behave best in very dry air and with the mixtures fed to the separator while hot to reduce the adsorbed water content. On the other hand, an overdried mixture on coming to equilibrium with more humid air, has been known to take up moisture selectively on one family of particles, as of coal in the presence of slate and clay, and give sharper electrostatic separation. From these observations it is concluded that there is a permissible moisture content for a particle and also for the atmosphere surrounding it, if in equilibrium, at which the particle will have a conductivity or cntact potential2-4 that is ideal for electrostatic separation. This permissible moisture content varies between a wide range of limits for the different materials that are are and with the kind of electrostatic separating process used. Water can be present as a result of adsorption and condensation from the atmosphere, as an accumulation before or during mining, or as a residue from a previous process step. The water may exist as a liquid film or as an adsorbed layer of vapor. If the water exceeds permissible limits it must be removed. Its state determines the method. Drying by evaporation is necessary for adsorbed water, for part of the liquid-film water (that is, up to several percent of the dry weight), and for free water in the internal structure. Large water contents may be removed by drainage Or filtration. At just what point mechanical removal should cease and drying by evaporation begin depends upon the method of mechanical removal and its cost. Particles can also be separated according to their differences in dielectric constant when suspended in a liquid of intermediate dielectric constant. Recovery of this liquid presents a a problem' Permissible Moisture The adsorbed moisture on the outer surface of minerals can be quickly removed or replaced. Accordingly, in speaking of adsorbed moisture contents, either that of the solid or that of the surrounding air may be considered, the two values being connected by a distribution coefficient which varies with the temperature. However, such a condition does not necessarily exist in processes where an initially dry material is suddenly introduced into an atmosphere having a partial pressure of water vapor or where a moist material is suddenly introduced into a dry atmosphere. Here the resultant differences in the

Jan 1, 1949

By Foster Fraas

INTRODUCTION THAT variations in the humidity of the air and in the moisture content of a mixture of broken solids being separated electrostatically cause trouble is not new.1 Much of the reputation for unreliability commonly ascribed to the electrostatic separation processes is probably due to this one factor alone. Some operators dry thoroughly before separating; and while this is good in many instances, there are others in which it is not the remedy for trouble. Some mixtures behave best in very dry air and with the mixtures fed to the separator while hot to reduce the adsorbed water content. On the other hand, an overdried mixture on coming to equilibrium with more humid air, has been known to take up moisture selectively on one family of particles, as of coal in the presence of slate and clay, and give sharper electrostatic separation. From these observations it is concluded that there is a permissible moisture content for a particle and also for the atmosphere surrounding it, if in equilibrium, at which the particle will have a conductivity or contact potential2-4 that is ideal for electrostatic separation. This permissible moisture content varies between a wide range of limits for the different materials that are separated and with the kind of electrostatic separating process used. Water can be present as a result of adsorption and condensation from the atmosphere, as an accumulation before or during mining, or as a residue from a previous process step. The water may exist as a liquid film or as an adsorbed layer of vapor. If the water exceeds permissible limits it must be removed. Its state determines the method. Drying by evaporation is necessary for adsorbed water, for part of the liquid-film water (that is, up to several percent of the dry weight), and for free water in the internal structure. Large water contents may be removed by drainage or filtration. At just what point mechanical removal should cease and drying by evaporation begin depends upon the method of mechanical removal and its cost. Particles can also be separated according to their differences in dielectric constant when suspended in a liquid of intermediate dielectric constant. Recovery of this liquid presents a similar problem. PERMISSIBLE MOISTURE The adsorbed moisture on the outer surface of minerals can be quickly removed or replaced. Accordingly, in speaking of adsorbed moisture contents, either that of the solid or that of the surrounding air may be considered, the two values being connected by a distribution coefficient which varies with the temperature. However, such a condition does not necessarily exist in processes where an initially dry material is suddenly introduced into an atmosphere having a partial pressure of water vapor or where a moist material is suddenly introduced into a dry atmosphere. Here the resultant differences in the

Jan 1, 1947

(Members are urged to send in for this column any notes of interest concerning themselves or their fellow-members.) The following members have registered recently at the Headquarters of the Institute Seeley W. Mudd, Los Angeles, Cal. Charles Janin, San Francisco, Cal. Edgar Rickard, London, England. Donnel F. Hewett, Washington, D. C. L. Maurice Cockerell, Chihuahua, Mexico.

Jan 4, 1913

John Birkinbine, Philadelphia, Pa.: We have in the Institute two Dudleys—Dr. Charles B. Dudley, who has so thoroughly studied the chemical composition and physical behavior of rail-steel, and Dr. P. H. Dudley, whose investigations and

Jan 1, 1900

By J. C. Boswell, J. D. Crawford

IN addition to its base-metal and coal mining operations, the United States Smelting Refining and Mining Company has, for the past quarter century, been one of the few large American mining companies interested in dredging. Its activities in this field are confined to gold, and to Alaska, but it is the largest operator in that territory, with twelve huge dredges available to work during the summer on the frozen ancient beach sands at Nome and the gravels of Fairbanks. These operations will be described separately.

Jan 1, 1948

By Jerry L. Straalsund, D. Bruce Masson

A dew-point technique was used to determine the thermodynamic activity of zinc at 430°C in a series of e phase Ag-Zn alloys. The composition of the alloys ranged from 72 to 88 at. pct Zn. This range included the composition at which Massalski and King3 found a reversal in the composition variation of the crystallo-graphic c/a ratio, which they attributed to an overlap of the Fermi surface across the (002) faces of the Brillouin zone. The data is presented in a graph in which RT In yz,, where yz, is the activity coefficient of zinc, is shown as a function of atomic percent zinc. This curve has an unmistakable change in slope at the same composition that Massalski and King observed the beginning of the reversal in the c/a ratio. This change in slope of the thermodynamic data is also attributed to a Brillouin zone overlap. Equations are presented to demonstrate that the thermodynamic activity can be related to the density of states of the conduction electrons, and that the observed phenomena are consistent with this model. It is also demonstrated that the contribution of the density of states can be related to the excess stability, a phenomenological parameter recently shown by Darkeen" to be significant in the interpretation of thermodynamic data of metallic phases. The data seem to indicate that zone overlap has caused a spinodal point, and the resulting misci-bility gap, in the phase diagram. THE problem of developing an adequate thermodynamic model of solid solutions has proven to be difficult, and is still only partially solved. The main approach has been to develop a statistical model, such as that of an ideal solution, regular solution, and so forth, to which can be attached corrections for electronic, vibrational, magnetic, ordering, or other contributions. Such corrective terms are usually derived on an ad hoc basis, and it is difficult to predict in advance what their relative importance will be. This problem has been discussed in general terms by Oriani and Alcock,' who have reviewed several thermodynamic models and a few empirical correlations. The measurements described in the present paper were made to demonstrate in a special case the importance of one such corrective term, the contribu- tion of the energy of the conduction electrons of an alloy. It was our premise that the contribution of the energy of the conduction electrons to the thermodynamic activity of the alloy components could be detected; further, that such an effect would be observed at alloy compositions where other phenomena, also ascribed to the energy and density of states of the conduction electrons, are observed. The idea of the importance of the conduction electrons is hardly new. Hume-Rothery and his adherents have developed the well-known theory of alloy phases in which the sequence of phase fields in binary equilibrium diagrams, especially those involving the noble metals with the IIB, IIIB, and IVB subgroups, can be correlated by replacing the composition variable with the ratio of conduction electrons to atoms, e/a. Jones and others have developed a physical explanation for this correlation, in which they consider the solubility limits of phase fields to be restricted by an intersection between the Fermi surface and a Brillouin zone. The general features of the model are also quite well-known—presumably zone intersection causes the density of states to decrease at critical alloy compositions. The attendant increase in energy of conduction electrons in the original crystal structure allows an alternate structure to become more stable as the concentration of polyvalent solute is increased. In spite of the wide acceptance of these ideas on phase stability, there is only indirect* evidence, such as the variations in lattice parameter recorded extensively by Massalskizy3 and others, that Brillouin zone interactions occur. There are few experimental measurements, other than the correlations of the phase sequence, that substantiate the premise that the energy of conduction electrons affects the solubility limits of alloy phases. Much thermodynamic data of alloys has been found to be consistent with the theory; yet there is a lack of detailed data at compositions where zone intersection and overlap are thought to occur. One would expect that the energy of the conduction electrons would make a measurable contribution to the thermodynamic properties of alloys at compositions near zone intersection and overlap if the theory of Hume-Rothery and Jones is correct. This conclusion cannot be avoided, because the phase boundaries are determined by the requirement that the chemical potential of the components be equal in both phases at equilibrium. An electronic effect large enough to alter the stability of a phase should also affect the thermodynamic activity by a measurable amount.

Jan 1, 1969

By T. H. Weldon, L. V. Whiton, R. R. McNaughton, J. H. Hargrave

Oxygen enriched air is being used quite extensively in the metallurgical plants of The Consolidated Mining and Smelting Co. of Canada, Limited, at Trail, B.C. The oxygen used for this purpose is a by-product from the Company's chemical plants located in the area. Most of the ore treated in the Trail metallurgical plants comes from Com-inco's Sullivan Mine at Kimberley, B.C. At Kimberley the ore is milled to produce lead and zinc concentrates which are shipped to Trail for further treatment to metal. One section of this paper deals with the use of oxygen enriched air in the suspension roasting of the zinc concentrates. In this process the concentrate is calcined for leaching preparatory to electrolytic recovery of the zinc. A second section of the paper describes the use of oxygen enriched air in operations at the lead smelter. There oxygen enriched air is used in the blast to the lead blast furnaces and in the slag fuming furnace which recovers the lead and zinc contained in lead blast furnace slag. The final section of the paper outlines the precautions necessary for the safe use of oxygen enriched air in any plant operation. The Use of Oxygen Enriched Air in the Suspension Zinc Roasters The suspension roasting of zinc concentrate developed at Trail, B.C., has been described in AIME Vol. 121, "The Electrolytic Zinc Plant of The Consolidated Mining and Smelting Company of Canada, Limited" by B. A. Stimmel, W. 11. Hannay and K. D. McBean. Since the publication of that paper, the use of oxygen enriched air in suspension roasting has been introduced as regular practice with marked advantage. The relative importance of a specific advantage may vary with changing conditions, but, in general, it may be stated that improved operation has been achieved at increased capacities. Suspension roasting is carried out at Trail in converted standard 25 ft diam Wedge roasters. The 2nd, 3rd, 4th and 5th roasting hearths have been removed and the drying hearth covered over. Drying of the concentrate is done on the drying hearth and the 1st roasting hearth. The dried concentrate, after any lump's have been broken up in a ball mill, is fed to a single burner located in the upper part of the combustion chamber. Oxygen is introduced at the burner fan along with the gases from drying, returned combustion gases from the waste heat boiler outlet and the required amount of new air. Up to 60 pct of the concentrate settles out on the 6th roasting hearth, the rest passilig out of the roaster. The product collected in the waste heat boiler is finished calcine, but the dust collected in the cyclones after the boilers is returned to the base of the combustion chamber where the sulphate is decomposed. Gases from the c'yclones go to a Cottrell precipitator. The discharges from the 7th roasting hearth and the waste heat boiler are combined with the Cottrell dust to give the finished calcine. Following small scale tests started in 1933, oxygen enriched air has been used continuously in the suspension roasting of zinc concentrate in Trail, beginning in 1937. A significant factor in promoting its use in this operation was the availability of by-product oxygen from the Company's near-by Chemical and Fertilizer Division. To-day it is standard practice at Trail to use oxygen enriched air for zinc concentrate roasting. The most important requirement in roasting a zinc concentrate for an electrolytic plant is that the zinc in the calcine should have maximum solubility. It is also desirable at Trail that the gas produced for the manufacture of suhhuric acid should have a ~naximum concentration of SO2 and that a substantial recovery of waste heat from the gas be achieved. High solubility of zinc requires that the sulphide sulphur and zinc ferrite in the calcine be kept low. These are both functions of temperature and time, with formation of zinc ferrite also dependent on contact between the iron and zinc particles. One of the inherent advantages of suspension roasting is that minimum time and contact are achieved. The limit on temperature is imposed by the fusion point of the concentrate and not by the need to control zinc ferrite formation. Operating temperatures are normally maintained within the limits of 1725" and 1850°F. A relatively low zinc sulphate in the calcine is required at Trail, and this results from discharging the calcine from the high sulphur dioxide atmosphere at a temperature above 1600°F.

Jan 1, 1950

By Richard P. Rothwell

Fires in mines are so serious in their consequences and of such frequent occurrence, that their causes and the means of extinguishing them are certainly questions of the greatest interest to a large part of the engineering profession. We have already, in this country, many mines which have been burning for years, and though our hard anthracite is so difficult to ignite that for a quarter of a century after it was first discovered it mas not known how to burn it except with the aid of an artificial blast, yet most of the fires which have occurred underground have been in anthracite mines, and in the coal itself. The injury which these fires have caused to properties in various parts of the anthracite regions, and the cost of extinguishing them, would amount to many millions of dollars, and they have also occasioned the loss of many valuable lives. It is not surprising, therefore, that the subject has already attracted much attention, and the exercise of great ingenuity; and the present communication is made less with the expectation of announcing anything new, than with the object of putting upon record the present state of our knowledge on this subject, or, in other words, of indicating how defective are the present means of combating underground conflagrations. Causes of Mine Fires.—Even upon the surface, fire is a terrible foe to contend with, and there is probably no other which inspires such thorough and well-founded alarm. With what feelings, then, must we look upon this destructive element, when its field is in the narrow galleries of a mine, where the poisonous products of combustion, spreading in every direction, protect, in the most effectual manner, the fire itself from the attacks of extinguishers, while, if the face of attack be ventilated so as to enable then] to approach the seat of the fire, the air current simply increases the extent and violence of the conflagration. Fires underground originate in as various ways as those on the surface, and it is scarcely necessary to say that, except in the rare cases where they are the result of design, they are invariably classed as " accidents," and most generally as " unavoidable accidents." In reality, by an intelligent understanding of their causes and with due precautions, they can almost always be prevented. Ignorance and

By FREDERICK LAISY

A NUMBER of new plants for the treatment of copper ores were completed or under construction during the year. Among these may be mentioned the plants of the International Nickel Co., those of the Hudson Bay Mining and Smelting Co. and of the Roan Antelope Copper Co. Three copper re- fineries have been constructed, one at El Paso, Tex., and the other two in Canada. Two more are projected, one in France and one in England. The International Nickel Co.'s plant consists of an 8000-ton concentrator and a smelting plant containing thirty 10-hearth Herreshoff roasting furnaces, five reverberatory furnaces, and eight Smith-Pierce converter5 . The smelting plant is estimated to have a capacity of 5000 tons of ore or concentrate per day. The roasters are superimposed on the reverbratory furnace plant. As a consequence of this arrangement, the furnace building is unusually high. being 183 ft. from yard level to highest roof elevation.

Jan 1, 1931

By Chung Wang

CHINA now leads the world in antimony production, having contributed during recent years something over 60 per cent. of the world's production. The history of the antimony industry of China dates back to 1897 when the Tai Shing Co. was formed, under contract with the Hunan. Bureau of Mines, for the smelting of the ore to crude; and in 1908 the Wall Chang Mining & Smelting Co. was formed for the smelting and refining of the ore and crude to regulus. The writer was then asked to take charge of the erection and control of this first plant for regulus production in China and has, since then, been more or less connected with the antimony industry in this country. This paper contains the results of many years' experience in connection with the Wah Chang Mining & Smelting Co., Changsha; the Pao Tai Mining & Smelting Co., Wuchow; the Loong Kee Smelting Works and the To-Cheng Smelting Works, Hankow; as well as information gathered from various other small smelters, scattered in different parts of the Provinces of Hunan, Hupeh, Kwangsi, and Kwangtung. An idea of the growing importance of regulus production in this country can be gleaned from the fact that, within a period of about 8 years, the export of regulus from Hunan alone jumped from 3 tons in 1908 to about 6000 tons in 1915; that a production of about 23,000 tons of regulus per year could easily be effected from all the smelters, as tabulated below, most of which were erected a year or two ago under the stimulus of the war booms, if the price at Hankow were to stay somewhere about $900 (Mexican) per ton, half of what it was at its height, thus enabling the utilization of ores from the hinterlands of the provinces; and even under the present ruling of prices and the closing of the less-favored smelters, the production of regulus should not be less than 12,000 tons per year.

Jan 4, 1918

By C. R. Forbes, J. C. Barton

Many different shapes of drill bits are in use with hammer drills, but little definite information is available whereby to judge which one of these shapes is the best. The following investigation was undertaken in order to determine what effect, if any, the shape of the cutting edge has on the cutting speed and wearing qualities of drill bits. The bits tested were those in common use, namely, the 4-point or cross bit, the 6-point bit, the Z bit and the "Carr" bit. The rock in which the tests were made was the red granite from southeast Missouri. It is a coarse crystalline granite containing an unusually large amount of quartz and is extremely hard, and on account of its uniform texture is admirably adapted to this work. While tests in other rocks might show somewhat different results, nevertheless it is the opinion of the authors that the relative cutting quality inherent in the shape of the bits would be the same in all rocks. Other qualities, such as mudding freely, freedom from fitchering, etc., might make one bit more desirable than another in softer rocks. Description" of Bits Tested 'I'he 4-point bits were the usual shaped bits commonly made on the Leyner sharpener, with 14' taper on the wings and a 90" angle between cutting edges. Some tests were run at 85 Ib. pressure with a 4-point bit made with a 50 taper on the wings; this bit was formed with the Carr bit dies. The 6-point bits were the usual shaped bits made on the Leyner sharpener. The Carr bits were made with a 5º taper and an angle of 100" between cutting edges.

Jan 1, 1918