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By Frank Firmstone

In a paper read at the meeting in Cleveland, Ohio, in 1875,* I showed that as a result of changing from open-topped to close-topped furnaces at the Glendon Iron Works, there had been a decided falling off in regularity of working, which we attributed to the very different distribution of the materials in the new method of filling. Subsequent experience has, on the whole, confirmed the opinions then expressed, and in 1881 we decided to try the modification of the Langen charger, shown on the accompanying drawings, thinking by its use to approximate to the distribution obtained by dumping the barrows at six equidistant points in the circumference of the open-topped furnaces. The top of the furnace is closed by a ring-shaped " bell," as we still call it, the outside of which is cylindrical and rests by the turned lower edge on the bored seat of a " loose ring," supported by the lower part of the hopper. The inside of the bell is an inverted frustrum of a cone, the central opening in which is closed by a cylindrical plug, which is prolonged into a pipe to carry off the gas.? This center-plug is connected by rods and chains to sectors on the ends of a forked lever, to the other end of which is attached, by a wire rope, the piston-rod of the blast-cylinder used in opening the top. The rods connected to the center-plug pass loosely through the apexes of triangular frames, to the other angles of which the bell is attached; it thus being suspended by four points when the top is open. When the materials are dumped out of the barrows into the hopper, a part is thrown over the crest of the bell into the space between it

Jan 1, 1885

By G. D. Tranter

THE importance of ladle and teeming practice and its relationship to the yield and quality of the product has focused considerable attention on this phase of open-hearth operation. Inherently bad steel cannot be perfected by manipulation during teeming, but through the proper handling of "off heats" serious losses, which in many cases arise, can be greatly minimized. Conversely, good steel can be ruined as a result of poor workmanship in the -pit, and rendered unsuitable for application to orders where exacting surface and physical requirements are essential. Sufficient evidence has been secured to warrant careful investigation of pit operations when an abnormal number of basic defects develop in the semifinished product or are found on the inspection table. This paper is written from the standpoint .of the problems involved in making satisfactory ingots for sheet rolling. Furthermore, since rimming steel is almost universally used for manufacture of sheet, the data presented herein refer particularly to that type of steel. Going back some 30 years in open-hearth .history, the word "pit" properly described the hole into which the ladle was lowered to receive the metal tapped from the furnace. The working space was necessarily limited, and the disposal of slag and metal overflowing the ladle or lost because of breakouts presented a serious problem. The equipment, of course, was rather crude in the light of present-day development. Often no ladle stands were provided, the ladle being hung on the crane beneath the runner. When delayed taps occurred, the ladle was often held in position for many hours, thus tying up pit operations and causing delays to adjacent furnaces. Because of crowded conditions, slag thimbles were not used and a network of cast-steel triangles and old tapping bars, placed before the heat was tapped, was the means for removing slag from the hole. Furnaces of different capacities were used

Jan 1, 1935

By W. M. Weigel

THE rapid advance, during recent years, in the manufacture of articles that have been in common use for generations and the development of new materials entering into appliances and devices unheard of fifty years ago, have created a demand for some of the more common non-metallic minerals. To supply this demand there has quietly developed a branch of the mining industry of which little is known by most mining engineers the mineral-filler industry. In this paper, and generally in the trade, the term mineral filler is applied to a mineral used, in its natural state after mechanical preparation only (such as. grinding, milling and washing), without undergoing any chemical change and without exerting any chemical action on the substance with which it is incorporated. The consumption of mineral fillers is confined chiefly to large manufacturing centers in the eastern and northern states. Where available, materials originating near the place of consumption are used, as most fillers bring a comparatively low price and, frequently, the freight may equal the cost of the finished filler at the mine. The southern states have abundant deposits of non-metallic minerals suitable for fillers, which supply the manufacturing industries in adjacent states. Many of these deposits are equal to, or superior, in quality to those mined in the north, but they can not compete with them because of the freight rates. The mineral-filler industry has felt the present depression, but it has suffered less than most mining industries for as a rule the mills are simple, the overhead expenses are low, and the labor is entirely local and can revert to farm work when the plant closes down. Many other deposits in the southern district will undoubtedly be developed when business. revives and freight rates are adjusted.

Jan 2, 1922

By G. D. Tranter

The importance of ladle and teeming practice and its relationship to the yield and quality of the product has focused considerable attention on this phase of open-hearth operation. Inherently bad steel cannot be perfected by manipulation during teeming, but through the proper handling of "off heats" serious losses, which in many cases arise, can be greatly minimized. Conversely, good steel can be ruined as a result of poor workmanship in the pit, and rendered unsuitable for application to orders where exacting surface and physical requirements are essential. Sufficient evidence has been secured to warrant careful investigation of pit operations when an abnormal number of basic defects develop in the semifinished product or are found on the inspection table. This paper is written from the standpoint of the problems involved in making satisfactory ingots for sheet rolling. Furthermore, since rimming steel is almost universally used for manufacture of sheet, the data presented herein refer particularly to that type of steel. Going back some 30 years in open-hearth history, the word "pit" properly described the hole into which the ladle was lowered to receive the metal tapped from the furnace. The working space was necessarily limited, and the disposal of slag and metal overflowing the ladle or lost because of breakouts presented a serious problem. The equipment, of course, was rather crude in the light of present-day development. Often no ladle stands were provided, the ladle being hung on the crane beneath the runner. When delayed taps occurred, the ladle was often held in position for many hours, thus tying up pit operations and causing delays to adjacent furnaces. Because of crowded conditions, slag thimbles were not used and a network of cast-steel triangles and old tapping bars, placed before the heat was tapped, was the means for removing slag from the hole. Furnaces of different capacities were used

Jan 1, 1935

By Charles J. Moore

It seems a duty incumbent on the older members of the Institute to set forth in permanent form some of the results of their experience for the benefit of the younger members; this is the principal object of the present paper, which is the result of a recent examination requiring somewhat unusual geologic investigation. History. The London vein mas first discovered by float and occasional outcrops in the year 1873, four years before the great lead carbonate discoveries of Leadville, but the mine was not definitely located and opened until two years later, when the present locations, Mother, Paris, London, and Hard to Beat, were surveyed for patent. Since 1875 the London mine has been worked almost continuously until 1911, when the force was reduced to a few men only. In its early life the ore was assumed to be free-milling gold-quartz, although lead was a constituent of the vein throughout, and much useless expenditure was made in the erection and operation of a free-gold stamp-mill, with plates and tables for saving concentrates. The vein then opened was in the porphyry-limestone contact, a siliceous lead-ore, clearly most amenable to reduction by lead-smelter. The losses due to this process led in time to the close of the mill. For 20 years past, the mine has been worked under lease and the ore shipped to the lead-smelters in Denver or Salida. In January, 1912,I examined the mine to ascertain whether it was advisable to run a cross-cut tunnel some 4,200 ft. in length to intersect the main vein at a depth of 650 ft. below the present lowest workings. Finding a greatly-faulted zone, a close determination of the geological conditions became necessary to the solution of the problem.

Jan 1, 1914

By Foster Fraas

MOST commercial electrostatic separators utilize the electrical property of conductivity, but although based on the same principles, they are constructed in a variety of forms, a common one being the simple roll type. Some information obtained during an investigation of that type of separator, and which indirectly is applicable to other types, is presented here. NUMERICAL RELATIONSHIP In Fig. I material discharged from hopper 6 is fed onto grounded rotating roll 2. Electrode 3 is at a high electrical potential with respect to roll 2, and any conductive particle in contact with roll 2 therefore acquires an electrical charge of such polarity that, when present in the electrical field, the force on it is in the direction of electrode 3. A detailed description of the charging by conductance as utilized in electrostatic separators may be found in a previous publication.1 As a result of this force, the path of the projected particle is changed in increasing amounts in the direction toward region C as the magnitude of the charge is increased. With the dividing edge 4 the projected particles may be divided into two fractions -those in region C designated as "deflected" or " deflectant " and those in region B designated as "residue." [ ] When material is passed over the roll only once, a complete separation is seldom obtained, therefore most commercial separators contain several roll-separator units in series, and some practical machines use as many as 12. In this paper a "pass" means the passage of material over a single-roll unit. The procedure is to repass either residue B with a low potential on electrode 3 or deflectant C with a high potential on 3. Most electrostatic separations follow a flowsheet of roughing and cleaning either the concentrate or the tailing, on both. In a specific instance, a dry, heated mixture of wet cleaned chromite and garnet from an

Jan 1, 1942

By Herbert Banks Johnson

DURING the past 10 or 12 years very little information has been made generally available concerning the commercial possibilities of separating materials by means of static electricity; and yet during that same period important improvements have been made in various branches of the science of electricity, which, when taken together, and applied to electrostatic separation, have resulted in important improvements in that art as well. For example, much improvement has been made in high-voltage electrical equipment such as full-wave vacuum-tube rectification and improved mechanical rectification. Great strides have likewise been made in the development of insulators for high-voltage work, not only in the materials used but also in the design of the insulators themselves. Again, in another field, the development of air-conditioning equipment has improved the technique of controlling the surface condition, through drying or humidifying, of the various materials that are passed through the electrostatic separator. In many authoritative publications and textbooks, the electrostatic separation process is declared to require a balance far too sensitive for general commercial application. For example, one publication1 in the past has referred to an unfavorable effect on the process caused by varying atmospheric conditions such as humidity. Some2 have even gone so far as to state that sunlight and shadows may seriously affect the separating efficiency of the process. Such statements may have been true in the early development of the art, when the source of static electricity was derived from a friction disk machine, such as the Wimshurst. The Blake Mosher equipment and the work of Huff in applying motor- generator sets, transformers and mechanical rectification overcame much of this kind of objection to the commercial application of the electrostatic separating process. Another objection made periodically is that it is generally considered necessary to feed the particles into the electrostatic field in a stream that

Jan 1, 1938

By K. D. Eigenbrod

A case history is presented of a landslide that occurred adjacent to a highway in the valley of the North Saskatchewan River, about 12 miles upstream of Edmonton, Alberta. The slide took place in the late fall of 1965 following excavations associated with highway improvements that deepened the slope and cut it back to 20º. The slide occurred in the Upper Cretaceous Edmonton Formation. Till covers the bedrock at the location. The bedrock consists of interbedded mudstone, claystone, and sandstone with layers of bentonite and coal. The field investigation consisted of a series of pits at the toe of the slide and seven boreholes around it. Undisturbed samples were taken with a Pitcher Sampler and piezometers were installed at various depths in the section. The slide had taken place on a horizontal bentonitic clay layer and it crossed softened mudstone in the back slope. Three piezometric levels were detected but no water pressures were found along the horizontal portion of the slip surface because it was in contact with a free-draining coal layer. Borehole evidence revealed that the bentonitic clay layer was sheared in place beyond the confines of the slide zone. Although this slide was a first-time occurrence, it was part of a much larger slide block that moved presumably when the valley was being formed. Laboratory tests were carried out to determine the shear strength parameters of the bentonitic clay and the back slope material. These parameters together with the observed water pressure distribution in the slide area gave a factor of safety of 1.01 in a non-circular limiting equilibrium analysis. The case history is particularly instructive in indicating the care that must be taken to obtain representative information for stability analysis when geological and groundwater conditions are non-uniform. The origin of the sheared clay is discussed.

Jan 1, 1972

By C. S. Roberts, S. L. Couling

PLASTIC strain in polycrystalline metal as a result of bulk movement of one grain with respect to another along grain boundaries is not new. Rosenhain and Humphrey observed such effects shortly after the turn of the century.' Since then, observations of grain boundary deformation have been made on several metals. In recent years, intensive studies of the deformation at grain boundaries have been performed on polycrystalline metal and bicrystals.14-20 Aluminum or its alloys have been used in these latter studies. The subjects of controversy at present appear to be not whether grain boundary deformation exists, but 1) how quantitatively important it can be in polycrystalline metal, and 2) what its detailed mechanism is. Some investigators have concluded that such de- formation is minor in importance while others have concluded that it is a major consideration. Some have concluded that it involves shear of one grain over another at the interface while others have concluded that it operates by crystallographic deformation within the grains near ,the boundary. A categorical statement for electrolytic magnesium cannot be made on either of -these points. When polycrystalline magnesium is deformed in creep under conditions of high strain rate and low temperature, grain boundary deformation is relatively slight." Under these conditions, much deformation occurs within the grains and boundary contours change to a higher-energy jagged form. The result is shown in Fig. 1, where boundary jaggedness is pronounced upon polishing and etching after a plastic strain of approximately 6 .pct at 300°F and 3000 psi. No migration of the boundaries has been detected in this process. When the same metal is deformed the same amount at 600°F and 300 psi, resulting in a much lower strain rate, the boundaries migrate toward a lower energy configuration, where

Jan 1, 1958

By Walter White

THE measurement of the reading of a thermoelement is the measurement of an electromotive force extraordinarily small compared to those generally used in commercial work. Of the various possible methods of measuring such a quantity, the most advantageous is always a delicate galvanometer. Since a galvanometer measures current, it is necessary to adopt some scheme by which its current reading shall indicate electromotive force. There are two general methods of doing this. One is to use the delicate galvanometer as a "direct reader," that is, to let the electromotive force of the thermoelement furnish the power and produce the current measured. If the resistance is constant the reading will, after a suitable calibration, give the electromotive force of the thermoelement which, by means of a table or of a suitable scale in the galvanometer itself, will FIG. 1.-SIMPLIFIED POTENTIOMETER. POTENTIAL DROP ACROSS THE PART PIN or CIRCUIT OF BULL CELL BALANCES THAT OF THERMOELEMENT TC WHEN GALVANOMETER G READS ZERO. give the temperature. The other method, that of the potentiometer, is to balance the electromotive force of the thermoelement by means of another electromotive force, using the galvanometer to tell when the balance is made. The usual way of getting this other electromotive force is to have a battery, the "bull" cell, send a current through a series of resistances, which 'may in a special case be the resistance of a single wire. The fall of potential along this circuit will then, by Ohm's Law, be proportional to the resistance; the potential difference between any two points, proportional to the resistance between the two points. This is represented in Fig. 1, where M and N are the two points in the circuit AZ of the battery. If M or N, or both, is movable so that the resistance

Jan 9, 1919

By A. J. Fenn

Cananea is located at an elevation of 5,200 ft in the north-central part of the state of Sonora, Mexico, about 135 miles northeast of Hermosillo, the state capital, and about 30 miles south of the United States border. A graded road runs to Cananea from the border town of Naco, near Bisbee, and a branch road turns east to Cananea at Imuris, a town 36 miles south of the border on the Nogales-Hermosillo highway. Railway service is provided by a spur from the Nogales-Naco branch of the Ferrocarril del Pacífico Railroad. Fuel for the power plant, smelter, and town (population approximately 20,000) is natural gas, supplied through a pipeline from the United States. The Compa[n]ía Minera de Cananea generates electric power for its own installations and also supplies both electricity and water to the town. HISTORY The earliest record of mining in Cananea dates back to 1760, when Jesuit fathers worked the Cobre Grande mine for silver in spite of resistance from hostile Indians. About 1800, several mines were worked on a relatively large scale by the House of Guea of Chihuahua. From then until about 1890 when William C. Greene of Fairbanks, Ariz., acquired control of a large group of properties, mining continued in a rather sporadic manner. The mineralized district is approximately 6 miles wide and 15 miles long, and the orebodies are associated with breccia pipes and granitic intrusive rock. In the early days, many small mines operated within the area on high-grade orebodies. In 1899, Greene promoted the building of a mill and smelter and established the present company, The Cananea Consolidated Copper Co., S.A., now Cia. Minera de Cananea (S.A. de

Jan 1, 1969

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 Walter L. Maxson, Fred C. Bond

There is more information contained in a screen analysis than is ordinarily recognized, and there is an increasing need for methods of making this additional information easily available. As more comprehensive studies of crushing and grinding are made, and as the possibilities of decreased expense and increased extraction through a closer control of grinding are explored, methods of interpreting screen analyses assume an importance which they have not had heretofore. The information commonly desired, which can be determined from a complete and carefully made screen analysis, includes: (1) the size distribution of the material passing the finest screen, (2) the presence of a hard grinding fraction, (3) the location of natural grain sizes, (4) the presence of different materials with markedly different grinding characteristics, (5) the presence and amount of finely divided material such as clay, which is merely unlocked in grinding, and (6) the total surface area of the ground product. It is necessary to know the fundamental law of size distribution of a homogeneous material in order to correctly resolve a screen-analysis curve, and to understand the variations and anomalies that a sample may exhibit when compared with the ideal curve. This fundamental law was developed by Gaudin,1 who showed that when the logarithm of the per cent weight retained on any screen and passing the next larger screen in the Tyler standard screen scale was plotted against the logarithm of the screen aperture the resulting curve for the finer sizes of a homogeneous crusher or grinding-mill product would be a straight line. Gross and Zimmerley2 experimentally confirmed Rittinger's law, which states that the useful work done in crushing a homogeneous material is directly proportional to the new surface area produced; and showed that in the larger screen sizes resulting from impact crushing a

Jan 1, 1935

By H. N. Kalia, J. B. Gresham

Several attempts have been made in the past 60 years to commercialize the vast oil shale deposits of the US. However, the industry has yet to become economically viable. To date, it has not been possible to produce oil from oil shales at a competitive price compared with oil produced by conventional methods. The development work, nevertheless, has been fruitful in furthering the art of thick bed mining and technology of in situ retorting. The in situ method has the potential of recovering oil from thick beds, and the resource recovery potential is much greater than that from underground mining and surface retorting. In situ methods require that the shales/marlstones be fragmented in place to induce adequate porosity and permeability to allow in situ heating of the fragmented shales. This can be accomplished by using explosives. However, it has been found that the existing blasting systems, though very efficient, have some drawbacks. The explosives become insensitive when shot in multiplevertical decks. They can also become insensitive when spaced horizontally at close proximity to other charges. Also, since the blasting is done in a very limited free face, the delay time that can be allowed between charges is also quite limited. Consequently, it is not always possible to routinely predict the performance of the blasting system. Furthermore, since it is not possible to undertake secondary blasting, it is imperative that the blast design function properly. Recent successful retorting by Occidental Petroleum Co. Of Retorts 7 and 8 suggests that some of these problems may have been overcome. This paper addresses some aspects of in situ retorting and problems that have impeded the development of a viable oil shale industry in the US.

Jan 1, 1986

By Richard P. Rothwell

IN the pear 1881, I visited San Domingo, in the interest of French capitalists, to examine and report upon certain "concessions" of gold-bearing gravel and quartz veins, on the Isabella and Jaina rivers and their tributaries. This district is periodically reported to he extraordinarily rich, and there is oast around it the glamour of the mysterious shipments of gold, credited, in romance and in more or less romantic history, to Columbus and the Spaniards of the fifteenth and sixteenth centuries. Since considerable sums of money and several valuable lives have been lost in the unsuccessful search for its profitable mines, it seems desirable to place on record Borne of the information collected concerning the value of these famous gold fields, with the hope of facilitating the work of those who may hereafter be called on to investigate these claims, and of preventing the unnecessary waste of capital. It is needless to add that the capitalists for whom my investigations were made abandoned the enterprise they had in view,although no doubt similar schemes will be brought forward many times in the future, as they have been in the past, under the fervent advocacy of too sanguine enthusiasts. Since the time of the Spanish occupation of the Island of San Domingo, in 1497, when Columbus Found the natives wearing ornaments of gold, more or less of the precious metal has been obtained annually by washing the gold-bearing sands of several of its streams. It is said that during the Spanish domination, when the native Indians were held in the most abject servitude, a certain amount of gold was required of each one as the rault of his labor. Uuder this

Jan 1, 1882

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

RESEMBLING in some respects the enterprise at R Chuquicamata is that of the New Cornelia Copper Co. at Ajo, Arizona. Controlled from its inception by the Calumet & Arizona Mining Co., New Cornelia became a unit of the Phelps Dodge Corporation when the latter absorbed the Calumet & Arizona company in 1931. Both Ajo and Chuquicamata are situated in low mountains in extremely arid desert country. Both ore deposits consisted-the past tense is used advisedly because the oxidized ore has nearly all been mined at Ajo-of a horizon of leachable oxidized ores overlying sulphide or concentrating ore. The principal technical problem in each case was the development of a method for treating the oxidized ore. In both instances the capping of waste rock was comparatively thin and power-shovel mining in open cuts was the obvious method of exploitation. Nature had smiled on neither place in the matter of climate. Though Ajo does not have the persistent winds for which Chuquicamata is notorious, the comforts of living are largely artificial. And it is only fair to emphasize that at each place the mining companies have achieved remarkable success in providing these comforts. Of course, in point of size New Cornelia must be content with the inferior role. From May, 1917, when production was started, to the middle of June, 1930, the company leached 16,368,000 tons of oxidized ore, thereby virtually exhausting the ores of this class. Up to the same date, about 15,000,000 tons of sulphide ore had been mined, and a rough estimate gives 170,000,000 tons remaining in reserve. The total tonnage does not loom very large in comparison with Chuquicamata's billion tons; but it is exceeded by similar figures for only four of the Porphyry group.

Jan 1, 1933

By Carl E. Swartz

In the course of a recent investigation1 to develop a more satisfactory white-metal bearing alloy, a number of alloy systems were studied. The cadmium-nickel system showed characteristics desirable in a bearing alloy, and the system was therefore studied in some detail. Experimental Method Alloying cadmium with nickel offered no serious difficulty. After melting the cadmium, clean sheet nickel was added while the temperature was maintained at 500" to 600" C. A few crystals of ammonium chloride2 served to clean the nickel when the latter did not "wet" readily. In preparing the individual alloys for thermal and microscopic investigation, a "hardener" containing about 10 per cent nickel was used. Thermal Experiments and Apparatus Time-temperature cooling curves were made by standard methods. Globe electrolytic cadmium was added to the hardener to make a melt of the desired composition weighing between 100 and 200 grams. This charge was placed in a Pyrex test tube, 1 by 10 in., closed with a rubber stopper carrying a thermocouple sheath and quartz stirring rod. The assembly was lowered to a depth of about 4½ in. into an electric resistance pot furnace containing a No. 0000 clay-graphite crucible (to catch the melt in case of a break in the test tube). After the tube was clamped in this position, an asbestos-magnesia mixture was loosely packed in the furnace around the tube and a "halved" cover of transite placed on top. This left at least 5 in. of the test tube protruding from the furnace. When the alloy had melted, the thermocouple was adjusted so that the hot junction was l! in. from the bottom of the test tube. The melt was stirred thoroughly for several minutes to insure composition homogeneity and absence of thermal gradients.

Jan 1, 1934

By John A. 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 C. T. Eddy

The refining of native copper in the reverberatory furnace, as practiced in the Lake Superior district of Michigan, is very similar to the reverberatory melting and refining of cathodes, but the presence of arsenic in some of the copper concentrates renders the operation somewhat more difficult. Though the copper occurs as the native metal, which is often excep tionally pure—purer, in fact, than after it has undergone refining—its intimate association with the gangue minerals necessitates the cumbersome reverberatory treatment. The gangue consists chiefly of complex silicates of calcium, magnesium, iron, aluminum and sodium, but in certain ore deposits other minerals are often found, among them the native copper arsenides—mohawkite, whitneyite, algodonite and the like. These latter minerals, when present, because of their relatively high specific gravity (7.5 to 8.5), find their way into the concentrates through the gravity concentration processes employed in the recovery of the copper. When such concentrates are melted, the silicates are removed as slag, but, because of the great affinity of molten copper for arsenic, the arsenides dissolve more or less completely in the copper bath. Because of the stability of the resulting melt, the arsenic is tenaciously held in solution. The influence of arsenic on the properties of copper, especially on its electrical conductivity, is generally recognized. For certain uses it is beneficial, and in many instances its presence in limited amounts is not objectionable, but if the metal is to be used for electrical purposes, the almost complete removal of the arsenic is of prime importance. Considerable research has been done on the subject of the influence of arsenic on the electrical conductivity of copperll but the conclusions presented in the literature dealing with the problem show some disagreement. The methods now in use for the removal of arsenic have not

Jan 1, 1931