Search Documents

By J. F. Lewis

Much has been written on this great engineering work, principally from the civil engineer's stand-point. In presenting the subject to the Institute, it seems necessary to include something of geology as well as engineering. In this case, it is particularly the glacial and post-glacial periods with which we are concerned; for it has been clearly proved that the canal recently excavated has not for the first time opened the Des Plaines valley for drainage away from Lake Michigan, and that this valley, as well as the site of this city, is very closely connected with the processes and effects of the ice period. We have simply renewed a channel and a drainage direction which formerly existed. As the days of deep water-ways for commercial purposes are fast approaching, engineers may find the consideration of ancient topography and geologic changes highly useful. For what I may say on this subject I am greatly indebted to Mr. Ossian Guthrie, who has made an earnest study of glacial geology and labored especially to decipher the records of its history in this region. * Chicago is situated in the track of one of four great glacial ice-streams that swept down from the North: one moving due South from Marquette and entering the Illinois valley at Ottawa; one through the Lake Michigan valley, entering the Illinois valley near Lemont; one from Saginaw Bay diagonally across the States of Michigan and Iadiana, entering through

Jan 1, 1898

INTRODUCTION TO PROBABILITY THEORY The mathematical theory of probability provides the foundation for the interpretations and inferences that can be made from statistical techniques. Probability theory is a broad field of study in itself, and can only be touched on here in order to provide the necessary back- ground for a more complete understanding of statistical analysis. Probability is concerned with the outcome of random events. It had its beginnings in the theory of games of chance which were of great interest to European mathematicians during the last half of the 17th century. The outcome of a random process or experiment is defined as an event. The collection of all mathematical points associated with each event is called the sample space for an experiment. Consider a random experiment having a finite number, n, of possible outcomes, some of which have a characteristic A. What is the probability that A will result from a single

Jan 1, 1980

By M. A. Scheil

Austenitic stainless alloys are susceptible to stress-corrosion cracking which may occur under certain corrosion environments irrespective of their susceptibility to intergranular corrosion. Test samples are described for investigating stress-corrosion susceptibility of alloys for industrial equipment. A laboratory test using a solution of magnesium chloride boiling at 309 F. was found to produce transgranular cracks in several alloys investigated and in types 347 and 316 stainless steel tubing a residual stress of the order of 10,000 psi. was observed to initiate cracking. The susceptibility to stress-corrosion cracking as judged by the boiling magnesium chloride test indicates that alloys may be selected which will withstand a high stress in service Stressed specimens of stainless alloys included in a corrosion testing program will aid in determining the acceptibility of these fabricated alloys, when stressed, to the service conditions.

Jan 1, 1945

By AIME AIME

AWIDE variety of subjects was discussed at the Wednesday sessions on Non-metallic Minerals. W. M. Weigel as chairman, presided at the morning session, and W. M. Myers, vice-chairman, in the afternoon. In the morning session a paper by W. N. Logan on "Mineral Wool Resources of Indiana" was read by H. H. Hughes. Mr. Logan explained that as Indiana is the principal source of mineral wool, the paper might well he entitled "Mineral Wool Resources of the United States."

Jan 1, 1932

By Clarence Seyler

THE technical difficulties of cutting thin sections of coal for examination by transmitted light have hitherto restricted the investigation of the important subject of the microstructure of coal to the few possessed of the requisite skill and time. Apart from this, the method fails with anthracites and other coals rich in carbon, owing to the opacity of the material. Occasional use of the method of polishing a surface, with or without etching, has been made, but it was not until Winter1 published an account of his results that attention was seriously directed to the method. In May, 1923, a specimen of dull anthracite came into my hands; I tried Winter's method on it and the presence of megaspores and other vegetable structures became clearly visible. A preliminary notice was published by me;2 but I soon abandoned the use of Schulze's solution having found that a mixture of chromic and sulfuric acids gave far better results. In the meantime Turner and Randall, in America, had independently developed the method of flame etching, as applied to anthracite, with great success. I have spent a year studying the method of chromic etching, which gives excellent results with bituminous coals and cannels, as well as with anthracite. For anthracites, I have used the chromic method and Turner's method of flame etching, whichever was the more convenient or as a check one on the other. The polishing is done, according to metallurgical practice, by the use of a polishing machine and successively finer emery paper, followed by polishing on cloth moistened with a suspension of levigated green oxide of chromium, and a final rubbing on "selvyt" (a cotton velvet polishing cloth) moistened' with alcohol. The polished sample is examined by reflected light with a 2/3 and 1/6 in. objective. Bituminous coals usually show considerable structure, and even anthracites show it faintly in places. The sample is then etched by immersion in a boiling solution made by adding 10 c.c. of concentrated sulfuric acid to 30 c.c of a saturated solution of chromic acid; enough water is then added to dissolve

Jan 3, 1925

By AIME AIME

A PAPER prepared by James A. Adams, development engineer of the fitline & Smelter Supply Co., and presented at the last Annual Meeting of the A.I.M.E. in New York City, de- scribed a new automatic pulp density controller which has had a most favorable reception. Manual control has until now been the universal practice in spite of its shortcomings; samples of pulp for density determination were often improperly taken, and only at the operator's convenience, so that the trend in density changes was frequently missed, and the grinding circuit al- lowed to operate under something less than the most efficient conditions.

Jan 1, 1940

By J. J. Beeson

Page I. PrimaRy MineRalization............................................ 356 1. Introduction..................................................... 356 a. Scope of Work............................................... 356 6. Acknowledgments............................................ 357 c. The Bingham Mining District.................................. 357 d. General Geology.............................................. 357 e. The Utah Copper Mine....................................... 376 f. Field and Laboratory work.................................... 376 2. The Quartz-Monzonite.............................................. 377 3. The Pegmatite Veins.....:.•..............................:........ 378 4. The High-Temperiture Veins.........................-.............:379 5. The Early Hydrotherma! Period.:......................'............ 380 6. The Late Hydrothermal Period................................:.... 385 II. Seconuabx EnricuMENT............................................. 386 . 1. Author's Note;..... ;............................................ 386 2. Factors Governing Enrichment.....................................: 387 3. The Enrichment.................................................... 387 4. The Covellite Enrichment.; .:; ; : .:. :..:.............:................ 388 a. The Capping above the Covellite Ores:....:....................... 388 b. Conclusions Drawn. from a Study of the Capping and the Covellite ; Ores....,.............................................:.....,.' 392 c. Covellite Enrichment at Depth......:......................... : : 392 5. The Chalcocite Enrichment...................................... ; 394 a. The Carbonates in the Capping above .the Chalcocite Ores...:..: .. 394 ' b. The Formation of Chalcocite..:.:. :......:..'...........,......' 394 . 6. Secondary Chalcopyrite and Bornite.............................i ..., . 395 111.- Conclusions as to the Formation.oF the ImpoRtant Sulphides in the Disseminated ORes........................................,.......... 400 I. Primary MiNeRalization 1. Intrdtiction a. Scop. e .of Work.. first part bf, this paper deals with the country rock, its pegihatitic, pneumatolytic', and hydrothermal altektions; also, the effect of magnetite on the deposition of the primary chalcopyrite and pyrite.

Jan 1, 1916

By Cyril Wells

THE diffusion of carbon in gamma iron plays an essential role in many metallurgical processes. In carburizing, in graphitizing, in homogenizing, in the formation of pearlite from austenite, and in other processes, migra-tion of carbon in gamma iron occurs.1,2 A full understanding of the rate at which these processes occur obviously requires a knowledge of the rate of diffusion of carbon. In carburizing, for example, the depth of carbon pentration is determined by the carbon concentration in solid solution at the surface, and by the rate of diffusion inward of the carbon. Until reliable data on the rates of diffusion of carbon are available it is unlikely that a full quantitative description of this process will be obtained. In the formation of pearlite from austenite, the segregation of carbon and alpha iron from the austenite obviously requires the diffusion of carbon; the rate at which pearlite nodules grow is evidently controlled at least in part by the rate of diffusion of carbon; it is unlikely that we shall understand the factors that determine the rate of growth unless data on rates of diffusion of carbon, and the variation of these with com-position, grain size, and temperature are available. Accordingly it was decided: (1) to determine, more accurately than hitherto, the diffusion coefficients of carbon in austenite over a wide temperature and a wide concentration range, (2) to study the influence of grain size and impurities on this diffusion coefficient, and (3) to study the effect of manganese and nickel on the rate of diffusion of carbon in the austenite of manganese and nickel steels, respectively; the influence of carbon on the rate of diffusion of manganese and of nickel will be made the subject of later papers. The rate of diffusion of carbon in gamma iron has been studied by Runge3 by Tammann and Schönert4, by Bramley and co-authors,5-14 and

Jan 1, 1940

By E. S. Davenport

WHEN annealed carbon, or low-alloy, steels are suitably heated the ferrite (alpha iron solid solution) and the carbide, of which they are composed, react together to form a single solid solution of carbon (and other elements) in gamma iron (austenite). This reaction may begin only at a certain minimum temperature called the eutectoid temperature. The first ferrite and carbide thus to react together do so in definite proportions known as the eutectoid composition. With further heating the original constituent that is present in excess is dissolved in the austenite until exhausted. Whether the excess constituent be ferrite (hypoeutectoid steels) or carbide (hypereutectoid steels) the procedure is much the same, and upon slow cooling the homogeneous austenite expels the excess of either (proeutectoid ferrite or carbide) until the eutectoid composition is reached. Thus the reaction upon heating is strictly reversed upon cooling and accordingly an equilibrium diagram of this process may be constructed. Such an equilibrium diagram concerns itself only with the tempera¬tures involved and with the proportions and compositions of the phases developed under conditions that suffice to permit equilibrium. Specifically it has no concern for the type or mode of distribution of these constituents nor with any extra-equilibrium conditions such as undercooling, which is almost universally encountered in metals. Actually, however, of great importance is the sluggishness toward equilibration caused by the not inconsiderable time involved in diffusion. Thus instead of the theoretical transformation point AE, we find for a certain rate of heating or cooling the use of the designations Ar and Ac (transformation temperature found on cooling and upon heating). These figures obviously have no particular meaning except as measured and expressed for a definite heating or cooling rate, and represent the apparent temperature displacement caused by an inadequate time allowance. In this paper are presented the results of a study of the time required for' the transformation of austenite to ferrite and carbide at a variety of temperatures and also of the time required for the reaction austenite ?martensite at the temperatures at which this reaction occurs instead of

Jan 1, 1930

By B. S. Crocker

Pebble grinding was used at Lake Shore Mines in 1949. A full description of experimental evidence and test plant results was published in 1952 1 and further operating details in 1954 2.' In more recent years the term autogenous grinding has been coined and is now frequently seen in the technical literature. Autogenous crushing and/or grinding covers any grinding mill in which the larger pieces of ore are made to grind the fine pieces; the crushing and grinding may be either dry or wet. This discussion deals only with wet autogenous grinding, and only in the fine grinding part of the circuit, i.e., from 6 mesh to 92 pct —325 mesh. The term pebble milling could apply to fine autogenous grinding in which the pebbles are made from the ore itself, or it could also refer to grinding with pebbles, such as flint pebbles, from a source outside the mine. The first mill to use screened ore to grind the ore (1949) was Lake Shore Mines, Kirkland Lake, Ont. Pebbles were screened from the jaw crusher discharge and used in 5x16-ft tube mills which had been converted to 6 ft 8 in. by 16-ft grate discharge pebble mills. The same general practice was adopted the following year by the Wright-Har-greaves Mine in Kirkland Lake. Shortly after that the Neptune Mines in Nicaragua started correspondence with the writer concerning the possibility of using screened ore for grinding in their plant. They first ran some plant-scale tests which confirmed the Lake Shore findings, with the ultimate result that their plant was successfully converted in 1956 to an autogenous grinding plant. In 1957-1958 the writer was successful in converting the grinding plant of Renabie Mines in northern Ontario to autogenous grinding. In all these plants the existing grinding equipment was converted, usually by expanding the diameter of the shell to make the change from steel grinding to ore pebble grinding mills. In all the above plants primary grinding was done in either small rod mills or ball mills. These mills first reduced the pebble mill feed to about 6 mesh. The final grinding in the pebble mills varied from 75 pct —200 mesh to 92 pct —325 mesh. At Lake Shore three stages of pebble milling were used, with a different size pebble in each stage. In other parts of the world interest was being shown in this form of grinding, and in March 1952 the writer had some correspondence with the mill staff at Outokumpu in Finland, with regard to the pebble system used at Lake Shore. At Stockholm in 1957 the account of the crushing and grinding system at Outokumpu was presented in a paper by H. Tanner and T. Heikkinen.V his is the only ore grinding plant that does not use grate discharges on its pebble mills; trunnion discharges equipped with heavy reverse spirals retain the pebble load. The first new mill designed to use screened ore as a grinding medium was the Bicroft mill at Bancroft, Ont., which began operation in the fall of 1956. In 1957 this plant was followed by similar installations at Faraday Mines, also in the Bancroft area, and the North Rankin Nickel Mines in the North West Territories. In 1958 the Dyno Mill at Bancroft was converted, using the same type of grinding. Since all these plants, designed by Kilborn Engineering (1954) Ltd., were originally planned as pebble grinding mills, they were able to take full advantage of the latest design and technique. They are neat in appearance and very efficient and easy to operate. Effect of Ore Hardness: It is often commented that this type of autogenous grinding applies only to hard siliceous ores. Experience has shown that this is not so. In the past ten years the author has had an opportunity to test more than a dozen ores, several of which were quite soft. One of these was shale. The softer ores actually make better looking pebbles than the hard ores. These soft ores produced no particles in the intermediate size range which could not be ground by the largest pebbles in the mill charge. Slabby ores, such as shales, make a suitable pebble for the —6 mesh grinding. It is not generally recognized that for fine grinding a spherical medium is not essential or more efficient. Another frequent objection to pebble grinding is the belief held by some operators that there is too much variation in the hardness of their particular ore to make it acceptable as a source of pebble media. Experience has also shown that this is not a serious problem at all. The variation in pebble load due to changes in the ore hardness is nothing like as great as most people would expect, and the method used for feeding the ore and controlling the the load in the mills is more than sufficient to take care of daily variations in ore hardness. This point

Jan 1, 1960

By H. M. Chance

STRETCHING from New York southwestwardly to Georgia is a great range of hills and mountains consisting of pre-Palaeozic schists, slates, and gneissic and granitoid rocks, known locally by many different names; in Pennsylvaniaa as the South mountains, the Berkshire or Durham and Reading hills, and in Virginia and farther south as the Blue ridge. To the northwest of this range lies the " Great Valley," underlain by Lower Silurian limestones, and known as the Lehigh valley, Cumberland valley, Shenandoah valley, valley of Eastern Tennessee and Georgia and by other local names, but all these are parts of one valley, geologically and geographically continuous from New Jersey to Georgia. Lying upon and along the northern flank of this range of mountains, and dipping northwestwardly under the limestone of the valley, is the Potsdam formation (Primal or No. 1 of the Pennsylvania Geological Survey), which consists of sandstone or conglomerate overlain by slates. The latter are sometimes arenaceous and occasionally are replaced in part by sandstone. This formation varies from a few feet to several hundred feet in thickness. At the outcrop the slates are completely decomposed, oxidized or disintegrated, forming a belt of clay several hundred feet wide occupying the interval between the outcroppings of the sandstone and limestone. This clay-belt includes a more or less continuous series of iron-ore (brown hematite) deposits, which have been, and still are, extensively worked. The belt is more or less continuously mineralized with iron throughout its length, and hundreds of large deposits of ore have been developed and worked, producing many millions of tons of ore.

Sep 1, 1908

By Oliver Bowles

GLASS razor blades, glass chairs, and marble window panes attest that creative genius was still active in 1935. Many less striking, though doubtless more important, developments are to be recorded for the nonmetallic mineral industries, and not the least of them is the establishment of an Industrial Minerals Division in the A.I.M.E. under the able leadership of Samuel H. Dolbear, Chairman. Thus the nonmetallics are rightly granted equal dignity with metals and fuels in the category of mineral industries. The brief review of progress that follows merely touches the fringe of important developments in this broad field.

Jan 1, 1936

By K. Tanaka, J. D. Mote, J. E. Dorn

It) an attempt to ulLcoce.lP the operative strain-rate-contl-olliy: dislocation nieclzanistns, specially oviented sizgle clystals of the intel-nzediate 1zexagonal phase containing Ag plus 33 at. pct A1 were tested in tension over a wide range of temperatures. Slip was observed to take place by the {0001} <1120> {l100} mechani fracture took place across the(i100) plane and winning occurred by the (i01Z) ?lechanisn. Basal slip exhibited a strong yield point over the -alzge from 77 to 450°K, the upper ,esolved shear st]-ess having the exceptionally high value of 10,500 psi over this entire ?-a?zge of tenzpei,atuves. The critical 9-esolved shear stress for prismatic slip decreased f7-om 48,000 psi at 4.3"K to 23,000 psi at 170°K (Region 1) follozcirg zt:lzich it decl>eased sloz&ly to 21,500 psi at 475°K (Res&apos;on II); from 475" to 575°K (Regioz III), the c7-itical esolced shear stress dec&apos;-eased precipitously to 2000 psi; and from 575" to 750°K (Region IV) it decreased less afi&apos;dly to a low value of about 500 psi. Pvistintic slip in Region I was pobably controlled by the tliel-nally activated riecharzisui of nucleation and g,-ozcth of kinks in dislocations lying in Peierls potential troughs. In Region II for prismatic slip the critical 1-esolved shear stress was slzocn to be deteemined by sh0l.t-range 01-dering, Overall the forgiorz fo basal slip, 7.c.lre1-e a Strong yield-point phenorlienu ia7as observed, the critical vesolved slzea?-stress was shoztn to be determined by n conibirzation 0-f Szizuki locking and short-range-order Izavderzizg, The precipitous decrease in the critical resolved shear stress with increase in ter,/pe7-atrir-e over Region HI was tentatively ascribed to a decrease in the degree of slort-)ange 07-del;iqq (0)- clusteing) and also the effect of fluctuations the degree of o?der, It is at pgreser2t zrtzce)taitz as to 1t1hethe1- these or other possi1)le effects are also ,esponsible. fo- the data obsel-ved 172 Region IV. 1NTEREST in inter metallic compounds stems not only from their role in dispersion hardening of polyphase alloy ystems but equally from their potentialities for high strength, hardness, and stability not only at atmospheric temperatures but especially at elevated temperatures. As summarized in a re- cent symposium of the Electrochemical Society on "Mechanical Properties of Inter metallic Compound", most of the experimental evidence regarding the mechanical behavior of intermetallic compounds centers about the effect of temperature on the hardness and ductility of polycrystalline specimens. The available data reveal that the plastic behavior of intermetallic compounds might be rationalized in terms of the usual dislocation mechanisms appropriate to a solid solutions providing the additional complexities arising from crystal structure, long-range ordering, short-range ordering, and defect lattices are taken into consideration. It is apparent, however, in terms of the history on a solid solutions, that a complete detailed mechanistic rationalization of dislocation processes may not be possible until the deformation processes are studied in single crystals of intermetallic compounds. The present paper contains a preliminary report on the plastic behavior of single crystals of the hexagonal Ag-A1 intermetallic phase over a wide range of temperatures. The results confirm the thesis that single crystal data provide a most effective method of identifying operative dislocation mechanisms in intermetallic compounds. EXPERIMENTAL TECHNIQUES Several factors prompted the selection of the hexagonal Ag-A1 intermetallic phase for this preliminar investigation on the plastic properties of single crystals of intermetallic compounds: 1) This phase has a wide solubility range5 which would permit future investigations on the effect of composition and axial ratios on slip mechanisms. 2) Although it undoubtedly exhibits short-range ordering (or clustering) this intermetallic phase is free from complexities arising from long-range ordering.6 3) Since the atomic radii of aluminum and silver are practically identical, the possible complications due to Cottrell locking are minimized. 4)Whereas the dislocations on the basal planes are expected to dissociate into Shockley partials and are thus susceptible to Suzuki locking, those on the prismatic planes probably remain complete. 5) The axial ratio, being 1.61, is almost ideal, suggesting that short-range ordering may be almost spherically symmetrical. The present investigation was conducted exclusively with the hexagonal Ag-A1 alloy containing 33 at. pct Al. Preliminary investigations revealed that this alloy undergoes basal slip by the (0001)

Jan 1, 1962

By C. W. EICHRODT

NUMEROUS requests for the suspension of publicity make difficult the preparation of the annual review of copper metallurgy for 1934. In the United States, sales allocations indirectly have set restrictions on the scope of activities of producers and refiners, and necessitated closer cooperation between secondary and primary producers. However, the feeling exists that preparations for a return of intense competition should not he neglected, and careful investigations are being conducted for ways and means of improving industrial positions and production methods. In all probability, efficiency in technique and equipment will prove of far greater importance in the near future than production capacity, and many important developments in copper metallurgy later will be found to have been born during the current year.

Jan 1, 1935

By Thomas Fraser, David R. Mitchell

THE primary purpose of the loading plant is to transfer the finished product from the preparation machines to the railroad car, truck, or barge in which it is to go to market. Secondary purposes of the loading plant are: to prevent excessive degradation of sizes during loading, to reduce segregation as much as possible, and to prevent excessive quantities of very good or off-grade coal from entering any one car. Nonuniformity of consignments is one of the chief sources of com- plaints by consumers and coal merchants. A properly designed loading plant will do much to reduce complaints and ensure uniformity, not only from shipment to shipment but also in each individual consignment along the length of the car and in cross section. DEGRADATION IN STORAGE, LOADING AND SHIPMENT The object in loading is not only to handle the coal without breakage and segregation, but also to produce a well-trimmed load that will ride to its destination without spillage or breakage en route. The small sizes present in a car of prepared coal as received by the purchaser consist-of: missed small sizes not screened out in the preparation plant, breakage during loading, and breakage caused by handling en route. For domestic sizes of anthracite shipped from the Pennsylvania anthracite field to Atlantic coast cities, the dealers&apos; lass because of breakage in loading and shipment amounts to from 2 to 5 per cent and for anthracite shipped to Middle West cities, the loss is 8 to 9 per cent. This difference is in part because dealers in the Middle West rescreen their coal more thoroughly than is usual in the East. One dealer handling Illinois No. 6 coal shipped from southern Illinois mines to Chicago reports an average size loss of 10 per cent when lump coal is unloaded with a fork. This runs as low as 5 per cent for carefully loaded coal and as high as 15 per cent for carelessly loaded coal.

Jan 1, 1943

By Reginald Williams

THE amount or value of the precious metals consumed in dentistry is probably amazing to most people. It falls very little short of that which is consumed in jewelry. Inasmuch as the ultimate destination is in the human mouth, dental alloys enjoy some importance because life and health depend upon restorations made with them. Prosthetic dentistry has made wonderful progress in the last few years. The manufacturers who supply the metals also deserve commendation. This industry which deals with metals to go-into people&apos;s mouths is comparatively new. There is no literature on the subject, and little or no precedent by which to be guided. It was only by close cooperation with the dentist or prosthetic technician that desirable physical properties were produced, as-nearly as possible, in the metals which were available and permissible. It is true that there were and still are conflicting opinions among the dentists as to the physical properties they require. Sometimes they request the impossible, such as alloys which are exceedingly stiff and springy, yet will bend or adjust easily. Even in this latter instance, progress has been made by supplying methods of heat-treatment whereby metals may be softened or hardened at will. (Figs. 1 and 2.) The demands made upon manufacturers are extremely varied. They must supply metals of tensile strengths ranging from approximately 30,000 to 100,000 lb. per sq. in. and over. The latter metals must be workable and in many instances capable of extreme deformation. They must not be affected by mouth conditions, nor should they oxidize greatly when molten, at red heat, or during a soldering operation. In addition to physical, specifications, color demands must also be met. The firm of which I have the most, knowledge manufacturers 11,553 standard stock articles of precious metals, taking into consideration formulas, finenesses, grades, colors, gages, lengths, sizes and weights. If special demands are taken into consideration, the number would be in excess of 25,000. Wrought metals are manufactured in a great many alloys of different sizes and shapes, such as plate, bar, rod, wire, sheet, strip, mesh and foil. There are also other products of importance.

Jan 1, 1928

By P. Chiotti, G. R. Kilp

IN the study of zinc-zirconium1 and zinc-uranium2 systems, vapor-pressure measurements were made in order to establish the equilibrium phase diagrams for a pressure of 1 atm. In each of these systems, only zinc has an appreciable vapor pressure over the temperature range investigated. The zinc pressure was measured over a sufficiently wide temperature and composition range to permit calculation of the standard free energy, enthalpy, and entropy of formation for the compounds ZrZn, ZrZn2, ZrZn3, ZrZn6, ZrZn14 , and U2Zn17. In these calculations the compounds were treated as line compounds. Although the exact composition range was not determined, metallographic and thermal data indicate that the solubility range for these compounds is small. It is to be noted that the compound initially reported to correspond to the formula UZn9, 2 has been shown by the crystal structure work of Makarov and vinogradov3 to correspond to the formula U2Zn17,. The crystal structure is similar to that for the compounds Th2M17, investigated by Florio,4 et al; here M represents iron, cobalt, or nickel. Therefore, thermodynamic calculations are based on the formpla U2Zn17 EXPERIMENTAL The dew-point method employed to measure the vapor pressure of zinc over uranium-zinc alloys has been described previously.2 The same procedure and apparatus were used in measuring the zinc pressure over zinc-zirconium alloys. In the case of alloys in the two-phase region consisting of a zirconium and the compound ZrZn, the Knudsen effusion method was employed to obtain a few values in the temperature range 600" to 560°C. In most cases, tantalum crucibles were used to contain the zirconium alloys. THERMODYNAMIC PROPERTIES OFU2Zn17 A least-squares treatment of the vapor-pressure data obtained for 35 and 65 wt pct U alloys in the temperature range 650° to 940°C gave lOg10PAtm = 7,713/T + 6.33 Here, as in following equations, T represents degrees kelvin and P represents the zinc vapor pressure in atmospheres. The probable errors for the two constants were calculated to be 60.68 and 0.0563, respectively. This relation represents the equilibrium dissociation pressure for the reaction U2Zn17 (s) - 2U(s) + 17Zn(v) The solubility of zinc in solid uranium is negligible and the only additional information required to calculate the free energy of formation of U2Zn17 is the free energy of vaporization of pure zinc. K. K. Kelley5 gives the relations, AF°= 30,902 + 6.03Tlog T + 0.275 X 10-3T2 - 45.03T

Jan 1, 1961

By C. A. Heiland

MEASUREMENTS of gravity with gravimeters have come into increased use in this country and abroad in the past five years. Probably 100 to 125 gravimeter parties are working in the United States alone. In oil exploration, gravimeter methods have relegated the gravity pendulum definitely to second place, if not third, and now closely rival and possibly surpass the torsion balance in many applications. Gravimeters have lately been applied in mining, although it is doubtful whether they will ever replace electrical or magnetic methods in this work. Notwithstanding the widespread application of gravimeters, there has been no article covering the entire field in the domestic or foreign literature. The purpose of this paper is to meet the demand for com-prehensive engineering information on the subject. The working principles of a number of gravimeters will be, illustrated and treated in relation to the action of corresponding seismometers and astatization methods. The mathematical discussion of theory has been confined to the most necessary fundamentals and been given in as ele-mentary form as possible. A description of calibration methods con-stitutes the last part of the paper. The symbols shown at the top of page 2 will be used in equations throughout the paper.

Jan 1, 1939

By C. E. Mills

The Verde mining district is in Yavapai County, in north-central Arizona. Jerome, the principal town, has a population of 6000 and the two important mines of the district—the United Verde and the United Verde Extension—lie almost within its limits. Perched high on the southwest side of the Verde valley, at elevations of 4800 and 5500 ft. (1463 and 1676 m.) respectively, both mines have long tunnels from their lower levels through which the ore is hauled to the smelters. Clarkdale, the smelter town for the United Verde mines, lies in the Verde valley 4.1 miles (6.5 km.) distant in an air line from Jerome and at an elevation of 3560 ft. The two towns are connected by the standard-gage railroad of the Verde Tunnel and Smelter R. R., a subsidiary of the United Verde Copper Co. This road is 11 miles long and has a compensated grade of 4 per cent. At Clarkdale it connects with the Verde valley branch of the Santa Fe railroad. Clemenceau, the smelter town for the United Verde Extension mine, lies 3.5 miles (5.8 km.) in a southeasterly direction from Clarkdale, at an elevation of 3420 ft. It is connected to the Verde Valley branch of the Santa Fe railroad at Clarkdale by the Arizona Extension R. R., a subsidiary of the United Verde Extension Mining Co. The portal of the haulage tunnel, at an elevation of 3757.5 ft., is also connected with the smelter town by 4 miles of standard-gage track belonging to the same company. In the vicinity of Jerome, the great southern escarpment of the Arizona plateau forms the northeast side of the Verde valley. The general level of this escarpment, or "rim" as it is called, is about 4000 ft. above the Verde River. A corresponding elevation is reached only by the highest peaks of the Black Hills, which bound the valley to the southwest. Two lava-capped mesas, known as "Mingus" and "Woodchute mountains," form the culmination of the Black Hills. That part of the Old Black Hills mining district which lies between their crests and the Verde River is now known as the Jerome, or Verde, mining district. If the smelter towns are not included, a strip about 7 miles long by 3 miles (11 by 5 km.) wide, embraces practically all of the properties belonging to the Jerome district. T-bis strip lies parallel to and along the side of the Verde valley from First View, 2 miles northwest from Jerome, to the

Jan 1, 1925

By C. Kremer Bain

DURING the past several years of diamond drilling in Washington County, Mo., the St. Joseph Lead Co. has discovered a concentration of commercial lead-zinc ore at four different points within an area of 36 square miles. The largest and to date the most promising group of these orebodies is located in the Indian Creek area. It was considered to be of sufficient value to warrant development.

Jan 9, 1953