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By K. D. White, Chester W. Washburne

Colombia has an almost ideal situation with lespect to the world's markets, being only a short distance from the Panama Canal and the West Indies. The sailing distance from its Caribbean ports to New York is less than that from Tampico. Geographically, Colombia consists of three systems of broad mountain ranges separated by two long narrow valleys. The Cauca River valley separates the Western or Coastal range from the Central range. On the west side of the Coastal range are the Atrato and San Juan Rivers. The Central and Eastern ranges are separated by the Magdalena River valley. In the department of Santander the Eastern range divides, one branch continuing northward as the Cordillera of Perija, the other turning eastward across Venezuela as the Cordillera of Merida. Between these ranges is the great basin occupied by Lake Maracaibo. These valleys consist mainly of long narrow reentrants or tongues of Tertiary sediments between the older rocks of the mountain ranges. The late Miocene and younger sediments seem to have been deposited in separated basins, but the Cretaceous and possibly some earlier Tertiary strata were laid down more or less continuously over a great part of Colombia and Venezuela. These strata were subsequently folded into the present ranges. The deposition of the Cretaceous and of some of the Tertiary was in a great sea, the main land mass being in Brazil, with land probably along some of the cores of the present mountain systems. The sediments, except the Lower Cretaceous, vary markedly in character and thickness. An illustration is seen in the massive series of non-marine conglomerates and sandstones of the upper Magdalena River valley, near Honda, which are almost wholly wanting in the coastal sections where marine sediments prevail. The oldest rocks bearing on the search for oil are the black carbonaceous and bituminous shales, limestones, and cherts of the upper part of the Lower Cretaceous. These probably are the main source of oil in both Colombia and Venezuela. They include thick bodies of true "oil shale." Above the carbonaceous and bituminous beds, lies a series of many thousand feet of clastic sediments. The most noticeable and easily recognizable formation among these clastic sediments is the "coal-bearing series," which may be either upper Cretaceous or Eocene. The

Jan 1, 1923

By Rollin Farmin

"SWELLING GROUND" delivers pressure on mine timbers that originates in expansion of the wall rock, whereas "heavy ground" delivers only gravitative pressure. Of the several possible causes considered, the swelling is attributed to the physical surface action of water on gouge and flaky rocks at the periphery of the mine opening.

Jan 1, 1944

By Carl F. Dietz

(New York Meeting, February, 1912.) THE problem of drying ores is one that most mill-engineers are sooner or later called upon to meet, and it may be timely to point out sortie of the difficulties resulting from such operations from purely a metallurgical and economic stand-point. We mean, in the following pages, to discuss primarily the effect of such operations on. the ore itself, without particular reference to the mechanical or cost features of the subject; That an appreciable tonnage of the ore fed to the usual form of drier, either rotary or stack, is lost, is fairly well appreciated, but we believe that only a few mill-managers know just. what their drier-losses amount to, and we have found that in most cases they console themselves with the fact that the drier-smoke is not very much discolored, and it is generally believed that the draft is not sufficient to carry away more than a. negligible percentage of the values. The drying of ores is becoming an important factor. since the more general application of magnetic, static, and dry-table treatment. Its importance in the field of metallurgical operations warrants a close examination into its effects. This subject has been repeatedly brought hone to us, and while the drier-losses, in every case examined, have considerably exceeded even the most generous estimate, an attempt at a recovery of these values is rarely made. We have found that the losses resulting from drying-operations can be effectively recovered, at a low cost, and believe that the publication of the results of a number of investigations along these lines will be of interest and benefit to the profession at large. To dry an ore quickly and effectively, it must be brought into actual contact with hot gases or air. The rapid drying is effected by the fact that the hotter the gas the hungrier it is

Jul 1, 1912

By A. Thies, Wm. B. Phillips

1. Introductory Remarks.—The Haile Gold Mine is in Lancaster county, South Carolina, 3 1/2 miles east of Kershaw station on the Charleston, Cincinnati and Chicago Railway. It was first opened about, the year 1832, and since that time has passed through various fortunes. Many different operations have been practiced here for extracting the gold : panning, grinding in Chilian mills or arrastras, stamping, the Designolle process, dry-crushing, and finally the Thies process of barrel-chlorination, which has now been in successful use for 2 1/2 years, and by which 36,000 tons of ore have been treated profitably. The Thies process is in brief the treatment of dead-roasted auriferous concentrates (pyrite, sometimes also chalcopyrite, as at the Phœnix mine, Cabarrus Co., N. C.) with nascent chlorine, without ' artificial pressure or exhaust, in lead-lined iron cylinders; the throw-

Jan 1, 1891

By D. C. DERINGER

METALLURGISTS and mill operators appreciate, in a general way, .the economic or commercial relationship between recovery and grade of product but few have correlated in detail fluctuating metal prices with the metallurgy. They know that many factors such as metal price, dedusiions for returning charge, transportation, percentage of metal in head ore, etc.; all affect the commercial relationship between recovery and grade of product. In practically every mill some one at some ' time has calculated the amount of recovery that can be sacrificed for each percentage increase in grade of concentrate and from this calculated ratio the commercial or ., economic tail has been established. Such a ratio finally becomes a well-entrenched rule by which the progress of the metallurgy is judged.. When once established, these-, ratios are but seldom corrected to changes of metal prices for each possible grade of concentrate that may be produced. The calculation is tedious when often repeated. Other methods have been suggested and used to correlate the commercial with the metallurgical phase. A factor .derived ,by multiplying the grade of concentrate by recovery is often used, but is of little importance because it does not possess a single commercial quantity. The percentage monetary recovery calculated by dividing the gross value of the ore into the net smelter return gives a good economic index and, is to be commended, but it is difficult to correlate exactly and quickly the work of each day on a commercial basis.

Jan 1, 1931

By J. P. Carson

The works of the Tula Iron Company are in the Republic of Mexico, State of Jalisco, twenty-eight leagues southwest of Guadalajara, ten leagues northwest of the town of Sayula, through which passes the projected line of the Mexican National Railroad. Its geographical position would be about: latitude, 20' 10' N., longitude, 40 35' w. of Mexico City. The surrounding country is a rolling plateau, 6000 feet above the sea, enjoying the most magnificent climate in the world, the average temperature being about '70'. The works were commenced in 1850 by a company with very small capital, having not the least idea of the undertaking. They soon fell into the hands of the money-lenders, and after changing

Jan 1, 1879

By M. C. Flemings, R. Mehrabian, G. E. Nereo

Analytic expressions were developed and applied in two preuious papers to predict effects of solidification variables on macrosegvegation. In this paper, experiments are reported to test the analyses quantitatively and qualitatively. Good quantitative agreement is obtained between predicted and measured compositions for the following types of segregation (all experiments were on laboratory-size ingots of Al-4.5 pct Cu alloy): (a) inuerse segregation, (b) composition distribution in ingots solidified with unidirectional heat and fluid flow, (c) simulated centerline segregation, and (d) segregation resulting fro, change in solidification cross section. In addition, qualitative agreement of prediction of theory with experiment is obtained for (a) segregation resulting from sudden change in heat extraction during solidification, (b) centerline segregation in a bidirectionally solidified ingot, and (c) under-riser positive segregation. IN two previous papers,''2 it was shown that a variety of apparently different types of macrosegregation result from the same basic mechanism. This mechanism is the flow of solute -rich liquid to feed solidification and thermal contractions. Analytic expressions were derived and examples given of their application to predict macrosegregation. Calculations were for Al-4.5 pct Cu alloy. In this paper, we describe a series of experiments designed to test results of the foregoing calculations. All experiments were on laboratory-size ingots (weighing 10 lb or less), of A1-4.5 pct Cu alloy, nominal composition. APPARATUS AND PROCEDURE A typical mold and chilling arrangement used for unidirectional solidification is shown in Fig. 1. Before casting, this assembly was placed in an electrically heated air furnace, and heated to 680" to 700°C. When the plaster reached the desired temperature (usually 1 to 2 hr after the furnace temperature), the mold was filled through a funnel extending from the outside of the furnace into the cavity. The assembly, with liquid, was held for several minutes to allow convection to subside. The coolant, either air or water (depending on the desired solidification rate), was turned on and the ingot solidified. With the four sides and top insulated, heat removal for solidification was through the bottom surface, resulting in a fully columnar structure. Design of the casting cavity was varied, as discussed below, to produce desired macrosegregation effects. However, for castings solidified with unidirectional heat flow, the top was always open to the furnace atmosphere and temperature. The bottom sur- face rested on a chill through which the heat was extracted, and all other surfaces were insulated with plaster. In one case to be discussed, the mold design was changed to obtain bidirectional solidification. In this case, two vertical chills were used (on two faces of the mold) and the bottom was insulated. In a last case discussed, that dealing with under-riser segregation, experiments were conducted in bottom-chilled sand molds at ambient temperature. Except for this one case, all experiments were conducted in the electrically heated air furnace as described above. In many ingots, thermocouples were used to obtain continuous records of solidification. In all cases, these were chromel-alumel couples with output continuously monitored on a twelve-channel recorder. Where thermocouples were employed, these were embedded in the refractory mold walls during mold-making so their heads extended to the vertical centerline. Six to nine couples were employed, placed at intervals from the chill. METAL-MEL TING PROCEDURE Aim analysis was A1-4.5 pct Cu; alloy was prepared from high-purity aluminum (99.9 pct Al) and A1-Cu master alloy (50 pctOFHC Copper, 50 pct high-purity Al). The A1-4.5 pct Cu alloy was cast in 5- to 7-lb ingots for subsequent remelting for the macrosegregation experiments. Melting for ingot casting was as follows. After preheating the melting crucible for an hour or more, the charge was melted and superheated to a temperature of 690" to 720°C. After stirring, the melt was degassed with chlorine for 10 min. After stirring again for 1 min, a gas sample, under reduced pressure, was taken. When the sample was gas-free, the crucible

Jan 1, 1969

By H. J. Ramey

A general solution is presented for the transient temperature distribution caused by radial movement of a cylindrical heat source through a homogeneous medium of infinite extent. This problem represents a highly simplified model of the movement of a combustion front during the thermal recovery of oil. Numerical solutions are presented for a heat source moving at a constant velocity, and a velocity inversely proportional to the radial location of the heat source. Numerical solutions are presented for both finite and infinite vertical thickness of the heat source, i.e., with and without vertical heat losses. The numerical solutions are used to estimate the fuel concentration needed to maintain a combustion front during the thermal recovery of oil. The sensible heat carried to the combustion front by the injected gas stream is discussed in regard to the fuel concentration. Numerical solutions for a heat source (combustion front) of finite vertical thickness indicate the field conditions that may be necessary to sustain the temperature of a combustion front above the ignition temperature of the fuel over considerable distances from an injection well. The results also have implications in regard to the quantity of heat required during ignition. The results of this computation apply to a highly idealized model of a thermal recovery process. But the results may be used as a guide in engineering consideration of the thermal recovery process. INTRODUCTIO N The thermal recovery of crude oil has received considerable attention since the publication by Kuhn and Kochl of laboratory and field tests of this method of oil recovery. Other publications2,3,4,5,6, since that time have dealt with various features of the thermal recovery of oil and have illustrated the extremely complex nature of this process. Vogel and Krueger7 described an electric analog computer designed to solve a moving heat source problem which was analogous to movement of a combustion front during the thermal recovery of oil. The heat source was maintained at constant temperature and was a cylindrical source of infinite height (no vertical heat loss) moving radially at either constant velocity, or at a velocity inversely proportional to the radial location of the heat source. Jenkins and Ramey2 presented analytical solutions to a similar heat conduction problem and pointed out the possible importance of vertical heat losses. The following presents a general solution to the transient heat conduction problem introduced by Jenkins and Ramey4 as well as numerical solutions for a wide range of conditions possibly similar to those that might exist during field operation of the analogous thermal recovery process. DESCRIPTION OF PROBLEM The problem considered in this paper is determination of transient temperature distribution caused by a cylindrical heat source of infinite or finite vertical height, moving radially through an isotropic medium of infinite extent. It is further assumed that the heat flux generated at the surface of the moving heat source may be a function of time such that the fuel concentration required may be constant, or permitted to vary, and that heat is generated at the surface of the heat source only. In regard to the thermal recovery of oil the assumption that heat is generated at the surface of the front is equivalent to assuming that the thickness of the combustion zone is infinitely small, or that the reaction rate between fuel and oxidant gas is infinite. The last assumption does not appear stringent. See laboratory information published by Martin, et al3 Under these assumptions the temperature distribution throughout an infinite medium caused by a heat source moving radially with an arbitrary velocity may be described by The heat generation function or heat flux at the surface of the source, +(t), is Note that the fuel concentration may be defined as a function of time. Eq. 1 is derived in the Appendix.

By R. R. Sayers

VENTILATION may be defined as the process by which vitiated air of an inclosed or partly inclosed space is continuously replaced by fresh air. Fresh air has been defined as invigorating pure air. Pure dry air at sea level contains the following gases:1 Analysis of Air at Sea Level PER CENT. Oxygen 20.94 Nitrogen 78.09 Carbon dioxide 0.03 Argon 0.94 Helium, krypton, neon, xenon, hydrogen, hydrogen peroxid, ammonia, ozone traces CARBON DIOXIDE LIMIT For many years carbon dioxide was used as an index of the purity of the air vitiated by the metabolism of people. It was, however, well known that the untoward effects produced on those exposed to such air was not due to the concentration of the carbon dioxide. It has been found that the untoward effects on the comfort and efficiency of those so exposed are due to the increased temperature and humidity. It has been found that men can breathe air containing many times the amount of carbon dioxide found in our worst ventilated theaters and assembly halls, which, according to Rosenau, do not contain above 0.5 per cent. carbon dioxide.

Jan 7, 1926

THE John Fritz Medal Board of Award, at its regu¬lar annual meeting Oct. 19, awarded its gold medal to Herbert Clark Hoover. Thus ended a process of selection begun a few years ago. The award was tentatively made a year ago by the Board, which is composed of sixteen recent past-presidents of the four national societies of Civil, Mining and Metallurgical, Mechanical, and Electrical Engineers, having together a membership of nearly 60,000. The sixteen members of the Board are: American Society of Civil Engineers : C. E. Grunsky, Robert Ridgway, George S. Davison and John F. Stevens ; American Institute of Mining and Metallurgical Engineers: William Kelly, J. V. W. Reynders, Samuel A. Taylor and E. DeGolyer; American Society of Mechanical Engineers: Fred R. Low, D. S. Jacobus, Dexter S. Kimball and Charles M. Schwab; American Institute of Electrical Engineers: Farley Osgood, M. I. Pupin, C. C. Chesney and Bancroft Gherardi.

Jan 1, 1928

By AIME AIME

THANKS to the excellent preliminary work of: the Division officers and the local committee the fall meeting of the Coal Division at Bluefields was a brilliant success. West Virginia was at its best with its beautiful mountains, good roads and foliage, just beginning to turn to autumn colors. The meeting began on time and was kept on time throughout. The papers were-well prepared and, being on subjects of live interest, provoked 'lively discussion. One factor in bringing this about was that they were not too numerous and that with one exception copies had been submitted in advance a sufficient time to permit of them having been studied. The Friday morning session was presided over by John .J. Lincoln of the Crozier Coal and Coke Co. and president of the Pocahontas Coal Operators Association. After brief announcements by Thomas H. Clagett, chairman of the local committee, regarding plans for the two day's involved, and by Howard N. Eavenson, chairman of the Division, the reading of papers was taken up.

Jan 1, 1931

By Warden A. Moller

(Pittsburg Meeting, March, 1910.) THE Fushun coal-field, now being opened up by the South Manchurian Railway Co., is connected with the main line by a branch, 30 miles long, from Sui Chia Tun, 10 miles south of Mukden, the capital of Manchuria. The coal-field, which lies on the southern bank of the Hun river, 25 miles east of Mukden, consists of a long narrow valley,. running east and west between hills composed of granitic and volcanic rocks. At the foot of the northern hills, the Hun river flows westward towards the Liao river, which drains the greater part of South Manchuria. At the foot of the southern hills, resting immediately upon volcanic rocks, and overlain by 20 ft. of alluvial, is a thick layer of Tertiary shales, carrying near the base two coal-seams. In many places the lower of these two seams is in immediate contact with volcanic lauds and basalts, the flows of which were evidently both prior and subsequent to the formation of the coal-seams. This contact has practically destroyed the lower seam for commercial purposes. The value of the field lies in the upper seam, which, for a length of nearly 8 miles, varies from 100 to 130 ft. thick. Of this seam, 85 per cent is good coal. The seam dips to the north conformably with the shales, at angles of from 25° to 30°, and appears to have an uninterrupted dip for about 1.5 miles before being possibly cut o$' by the northern hills. The coal-bearing shales extend east and west for a length of about 20 miles, but towards the east the continuity of the seams is broken by intrusive rocks. The coal is of the sub-bituminous variety, low in ash, bright in appearance, and breaks with a conchoidal fracture. It has the usual qualities of Tertiary coal-quick steam-raising and poor stacking-qualities. Pieces of resin, varying in size from

Apr 1, 1910

By R. J. Evans

THE Combined Metals Reduction Co.'s plant is at Bauer, Utah. It was built primarily to treat ore from the Combined Metals mine at Pioche, Nevada. Shortly after its completion, the company acquired the old Honerine mine, and ores from this mine, as well as custom ores from widely scattered districts, are now being treated at the Bauer plant. PIOCHE ORE The Pioche ore, which comprises about 50 per cent. of the mill feed, occurs as a replacement of an impure thin-bedded limestone. The lime beddings are separated by thin layers of micaceous shale containing appreciable quantities of sericite and graphite. The ore is an exceptionally fine-grained, dense mixture of minerals and gangue, assaying approximately 0.03 oz. gold, 7.2 oz. silver, 7 per cent. lead, 15 per cent. zinc, 16 per cent. iron, 29 per cent. insoluble and 1.5 per cent. lime. Of the total lead 7 per cent. is in the form of sulfate and carbonate. Approximately 10 per cent. of the ore consists of chert nodules impregnated with barren pyrite; the nodules average 0.8 mm. in size, and are extremely hard, compared with the other constituents of the ore. Microscopic examination of Pioche ore ground to 80 per cent. minus 150 mesh shows pyrite, sphalerite and galena still attached. EARLY ATTEMPTS AT ORE DRESSING Metallurgists, both professional and those working for private companies, have been more or less familiar with the Pioche ore since 1913; in fact, a total of 35 commercial and plant laboratories experimented with the ore between 1913 and 1921. The work during this period was decidedly negative, it being seemingly impossible to effect a satisfactory separation of the valuable minerals into marketable products. In 1913, it was recognized that fine grinding-that is, about minus 200 mesh-was required to liberate the minerals from one another, and from the gangue, but such fine grinding was not considered practicable at this time.

Jan 1, 1928

By R. F. Krueger

Results are presented from tests of dynamic fluid-loss rates to cores from clay-gel water-base drilling fluids containing different commercial fluid-loss control agents (CMC, polyacrylate or smt,ch), organic viscosity reducers (quebracho and complex metal lignosulfonate) and oil at several different levels of concentration. In the dynamic system the most effective individual additives to the clay-gel drilling fluid, based on cost-equalized concentrutiom, were found to be starch and the viscosity reducers. These results do not conform with the rankings determined by API fluid-loss rests, which indicate CMC, polyacrylate and starch to be the most effective and comparable. Generally, minimum dynamic fluid-losr rates were attained at cost-equalized concentrations of additive (including thinner) of about $1.00/ bbl, or less. For chernically treated clay-gel drilling fluids, both the standard and the high-pressure API filter-loss tests were found to he inaccurate indicators of trends in dynamic fluid-loss rates under the test conditions used, particulurly for drilling muds containing viscosity reducers. From a practical field viewpoint, restrictions on the applicability of the API fluid-loss test are such that it is open to question whether or not results of this test can be used routinely with confidence as an indicator of control of down-hole fluid loss under field treating conditions. INTRODUCTION The petroleum industry spends large sums of money during drilling operations to control the fluid-loss properties of drilling fluids based on the standard API filter-loss test,' which is a static filtration system. Laboratory studies' ' of dynamic filtration have shown that in a given time period filtrate loss from a circulating mud stream is greater than from a static system and that it is a function of linear mud velocity, pressure and the properties of the drilling fluid. Ferguson and Klotz' and Horner, et al," observed that (I) the dynamic fluid-loss rates for the drilling fluids used were not related to the extrapolated API filter loss and (2) the drilling fluids with the lowest API filter losses did not have the lowest dynamic fluid-loss rates. However, there has been no published information on the relative effects on dynamic fluid-loss rate as a given drilling fluid is treated with increasing amounts of chemical additive to reduce the API filter loss. Such information is economically important because drilling-fluid costs rise rapidly as chemical requirements increase. This paper presents the results of a study of dynamic filtratioi rates to cores from a clay-gel water-base drilling fluid treated with various commercial viscosity reducers and chemical fluid-loss control agents. The dynamic fluid-. loss rates to cores are compared with the standard API filter-loss values at several different levels of additive concentration. Dynamic filtration rates were obtained in each experiment under two different simulated wellbore conditions: (1) filtration just above the bit through a new mud cake laid down dynamically on a freshly drilled formation and (2) filtration up-hole through a mud cake formed by deposition of a static filter cake on top of the initial dynamically formed cake. The latter case corresponds to the bottom-hole conditions existing above the bit when mud circulation is restarted after a stand of pipe has been added or a round trip has been made to change the bit. Except for the short-duration, high-rate filtration beneath the bit where no mud cake can form, these two conditions probably represent the two extremes of dynamic filtration. Because thickness of a dynamic mud cake formed on freshly exposed formation is limited by the shearing action of the mud stream, the filtration rate for this condition is high. On the other hand, once circulation is stopped and a static mud cake forms on top of the dynamic cake, re-starting circulation has only a small effect on the cake properties and filtration rate is much lower thereafter. A discussion of the mechanics of mud-cake deposition and dynamic filtration is outside the scope of this paper but may be found in more detail in publications by prior investigators. APPARATUS AND EXPERIMENTAL CONDITIONS The test equipment used to simulate the dynamic flow conditions existing during drilling was a modification of that described previously by Krueger and Vogel: A schematic flow diagram is shown in Fig. 1. In general, a power-driven, high-pressure mud pump capable of delivering up to 60 gallmin was used to circulate drilling fluid parallel to the faces of 1-in. diameter sandstone cores mounted in a 2 3/4-in. ID high-pressure test cell. Pump rates were controlled by means of a magnetic clutch to maintain an average axial fluid velocity of 110 ft/min in the annular space between the cell wall and a 1 1/2-in. rod positioned on the center line of the cell. The core specimens were Berea sandstone plugs sealed with plastic inside 1 1/8-in. OD tubes and were fluid-saturated prior to use. Burettes were used to accumulate fluid discharged from the cores. The mud sump shown was used for treatment and storage of the drilling-fluid samples during a particular test. The valve arrangement permitted either (1) circulating drilling fluid through the by-pass line while treating with

By Nathan C. Rockwood

BASIC mineral commodities may be divided into two general classifications in their market or price characteristics. In one class are commodities sold on a world-wide basis, as gold, silver, nickel, asbestos and petroleum, and in the second are those produced and sold locally. Of course, no precise line of demarcation exists between the two; coal, for instance, belongs more or less in both. If there are enough producers of any commodity to prevent control of production by any one person or group, a free market then exists and the price in a buyer's market is determined by the most favored producer-meaning the producer, with the lowest production cost or the lowest cost of transportation, or both, to the particular market, or place of use. With minerals in the first classification, their high intrinsic value far outweighs the transportation cost and a uniform market price is accepted as an essential element in the economy of distribution. But with common minerals of small. intrinsic value and relatively high transportation costs, economists are reluctant to admit that a uniform price may also be an essential element in distribution.

Jan 1, 1940

By R. J. Evans

The Combined Metals Reduction Co.'s plant is at Bauer, Utah. It was built primarily to treat ore from the Combined Metals mine at Pioche, Nevada. Shortly after its completion, the company acquired the old Honerine mine, and ores from this mine, as well as custom ores from widely scattered districts, are now being treated at the Bauer plant. Pioche Ore The Pioche ore, which comprises about 50 per cent. of the mill feed, occurs as a replacement of an impure thin-bedded limestone. The lime beddings are separated by thin layers of micaceous shale containing appreciable quantities of sericitc and graphite. The ore is an exeeptionally fine-grained, dense mixture of minerals and gangue, assaying approximately 0.03 oz. gold, 7.2 oz. silver, 7 per cent. lead, 15 per cent. zinc, 16 per cent. iron, 29 per cent. insoluble and 1.5 per cent,. lime. Of the total lead 7 per cent. is in the form of sulfate and carbonate. Approximately 10 per cent,. of the ore consists of chert nodules impregnated with barren pyrite; the nodules average 0.8 mm. in size, and ire extrcmely hard, compared with the other constituents of the ore. Microscopic examination of Pioche ore ground to 80 per cent . minus 150 nicsh shows pyrite, sphalerite and galena still attached. Early Attempts at Ore Dressing Metallurgists, both professional and those working for private companies, have been more or less familiar with the Pioche ore sinee. 1913; in fact, a total of 35 commercial and plant laboratories expenmented with the ore between 1913 and 1921. The work during this period was decidedly negative, it being seemingly impossible to effeet a satisfactory separation of the valuable minerals into marketable products. In 1913, it was recognized that fine grinding-—that is, about minus. : 200 mesh—-was required to liberate the minerals from one another, and from the gangue, but such fine grinding was not considertd practicable at this time.

Jan 1, 1928

By C. Land, R. Hultgren

Heat contents of four Cr-Ni alloys were determined in a diphenyl ethev calorimeter. Aside from ferromagnetic effects, Kopp's law of additivity of heat capacities is approximately fol-lowed, in disagreement with earlier results of A. W. Foster. In 1934 Foster1 reported heat-capacity measurements of dilute solutions of chromium in nickel, primarily as a study of the effect of alloying on the ferromagnetic Curie temperature. He found that, apart from the Curie temperature effect, the general level of heat capacities was reduced 10 pct by the addition of 1 pct Cr; 20 pct by the addition of 2 pct Cr. His measurements of pure nickel essentially agreed with accepted values. These results indicate that small amounts of dissolved chromium cause an increase in the Debye temperature of nickel, presupposing a change of frequency of interatomic bonding vibrations which is much larger than should be expected. If Foster's results were verified, therefore, they would have important implications for bonding theory. The only other heat-capacity measurements in this system seem to be those of Taylor and Hinton,' who studied anomalies which they attributed to super-lattice formation at 25 at. pct Cr. At temperatures above the anomaly, Taylor and Hinton found heat capacities at this composition were quite normal, approximately obeying Kopp's law of additivity. EXPERIMENTAL WORK In order to verify or disprove the remarkable results of Foster, the heat contents of four dilute solid solutions of chromiunn in nickel were measured in a diphenyl ether calorimeter. This instrument, described elsewhere,, operates on the principle of the Bunsen ice calorimeter, but uses diphenyl ether as the working substance. Diphenyl ether melts at the convenient temperature of 26.S°C and supplies a more sensitive measure of heat than ice. The hot sample, in an atmosphere of argon, is dropped from a furnace at a measured temperature into a chamber which is surrounded by a mixture of solid and liquid diphenyl ether. The heat from the hot specimen melts some of the solid without chang- ing the temperature of the calorimeter. The amount of solid melted, and therefore the number of calories released by the specimen, is measured from the increase of volume of the mixture, which pushes mercury down a graduated capillary tube. The apparatus has been standardized against the known heat content of pure platinum. Heat loss during the dropping of the specimen was estimated by comparing the heat content of an empty platinum capsule with a solid platinum ball of the same radius and degree of polish of the surface. Repeated tests demonstrate the precision of measurement to be closer than *0.3 pct. Smoothed experimental results are listed in Table I. The tabulated values for pure nickel are taken from kelley, several measurements were made which agreed closely with this tabulation. For chromium, however, no similar agreement was found. The values tabulated were taken from a thorough study of chromium with the diphenyl ether calorimeter which will be published elsewhere.= Suitable plots of the data showed the expected ferromagnetic anomalies in the low-chromium alloys, while the 11 pct alloy shows no ferromagnetic anomaly, but a different, small anomaly below 900°K. This is perhaps the same anomaly found in CrNi, which was once attributed to superlattice formation,' but is probably due to some other cause, such as antifer-

Jan 1, 1960

By Frank T. Sisco

DURING the past year the iron and steel industry of the world as a whole operated on a satisfactory basis. No discoveries nor new processes of outstanding importance were announced either here or abroad, although rumors of such were persistent. In general, the efforts of operating and research men in the iron and steel industry seemed to be confined to improving quality and reducing cost, not a new aim, for the same efforts have been noted in nearly all of the annual reviews of the industry for at least fifty years. Most published papers on blast furnace or steel-making practice were of minor importance, at least when judged by the criterion of radical change in process or product. If the number of reports in the technical journals, or articles in the trade press, is used as a basis for comparison, continuous-mill sheet is still the most important single product of the industry; papers were published detailing the results of the investigation of various phases of the

Jan 1, 1938

By F. Z. Schellenberg

(Pittsburg Meeting, March, 1910.) SYSTEMATIC exploitation in the Pittsburg coal-seam on a large scale is simple where the boundaries of the property do not interfere by forcing drainage-, ventilation-, and transport-lines of entries to be run to particular confined fronts. A prime condition governing development is the natural direction of the seam's perpendicular cleavage-planes, giving long lines of smooth faces near together and parallel, bearing about 65° to the left of the meridian and therefore crossing the basins. The gradients of dip into the basins change from 10 per cent at the east rim to practical flatness northwestward across the great coal-fields, a hundred miles wide; the clip being halved in rate at each successive crossing-over of an anticlinal crest. Elevations above sea-level on this transverse section, in scope of present development, differ by 1,000 ft. between low trough and high outcrop. Local irregularities of dip are found, but the main feature to be recognized is the pitch of the basins-the general rise northeastward at 20 ft. per mile, from 100 ft, below sea-level at the low point near the. SW. corner of Pennsylvania to 1,500 ft. and more above tide, and the appearance then, at the surface, of the lower coal-seams carried in the next deeper-lying thousand feet of rock-measures; below which series come the oil- and gas-sands of Oliphant's charted column of strata, reaching down altogether 3,000 ft. below the Pittsburg coal-seam. Because of -the general regularity of occurrence of the coal-seam, the mine-map depicting the courses of economic operation to be undertaken and the steps in controlled exhaustion, need be but a projection of two dimensions on the horizontal plane of space, and this for the most part composed of natural, almost unbroken lines, on the face and on the end of the coal, co-ordinating rectangularly.

Jul 1, 1910

By F. P. Haver, M. M. Wong

When a mixture of chalcopyrite concentrate and lime is heated in air, the following reaction takes place: 2CuFeS2 + 4Ca (OH)2 + 8 ½ 02 ; 2Cu0 + Fe203 + 4CaS04 + 4H20. Ca (OH)2 is the only common reagent that will adequately control SO2 evolution in roasting. Other additives tried, including CaO, CaCO3, Na2CO3, NaOH, MgO, Mg (OH)2, and MgCO3, were not effective. All reacted with sulfur, but not to the extent that will be required to meet the new control regulations for sulfur oxide emissions. For example: when the concentrate was heated with the theoretical amount of limestone (CaCO3), about 55% of the sulfur was retained in the calcine; whereas use of the stoichiometric amount of Ca (OH), converted approximately 99% of the sulfur to CaSO1. In most of the experiments, Ca(OH)2 was formed by adding CaO to concentrates containing enough water to simulate filter cake from flotation circuit. This eliminated the need for drying the concentrate and utilized the heat of hydration of CaO.

Jan 6, 1972