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By H. F. Porter

MUCH has been written relative to the errors involved in the use of a galvanometer for measuring thermocouple electromotive forces. In general, it may be said that accuracy with a galvanometer is secured only at the sacrifice of durability, unless manual adjustment is made in the operation of the instrument to overcome the errors of resistance. and resistance changes. The pyrovolter and the potentiometer both require manual adjustment for every reading, readings being taken on a "null" method. To the end that some of these balances may be eliminated and only an occasional balance be made as a check reading, the "continuously deflecting pyrovolter" was developed. Essentially, the operation of the continuously deflecting pyrovolter is to determine the resistance of the thermocouple circuit, though its value is not noted or indicated, then throwing in series with the thermocouple sufficient resistance to bring the sum up to some standard value for which the indications of the galvanometer will be correct. This result may, however, be accomplished in a somewhat simpler manner, for which general method patents are now in the course of application. If we devise a galvanometer circuit so that by means of a simple adjustment the resistance of the entire circuit will be rendered equal to some constant predetermined value, we may rely on the galvanometer to give correct e.m.f. indications (assuming that the errors of temperature resistance coefficient and cold junction have been properly allowed for), and will indicate temperature continuously where the e.m.f. measured is developed by a thermocouple.

Jan 9, 1919

By J. I. Budnick, W. B. Ittner III, D. P. Seraphim

A reliable technique has been developed for producing single crystals of tantalum in the form of small diameter wires. By suitably heat treating these and polycrystal samples, first in an oxygen atmosphere and finally in vacuum, it has been found possible to reduce residual resistivities to 10-3 microhm-cm. The purity of these samples is thus comparable to the purities obtained in zone-refined silver, copper, and aluminum. THE growth and purification of pure single crystals of the transition metals is, in general, difficult. The high melting and annealing temperatures of these metals make it necessary to employ rather special techniques in any crystallization process. In addition, the transition metals show a great affinity for and are easily contaminated by nitrogen, oxygen, and carbon. Recently, however. a number of investigators have been successful in growing,

Jan 1, 1961

By D. W. Peaceman

In previous papers by this author on numerical calculations of multidimensional miscible displacement, some simplifying assumptions were made in writing the dispersion term of the differential equation. It was assumed that the flow vectors were essentially parallel to the x-axis. However, in most multidimensional miscible displacements, the flow vectors are not so simply oriented with respect to the coordinate axes. This paper derives the correct dispersion term /or the more general case; gives a difference approximation /or the dispersion tern; and derives the stability criterion for the corresponding explicit difference eguation.

Jan 1, 1967

By W. P. Lass

Discussion of the paper of W. P. LASS, presented at the San Francisco meeting, September, 1915, and printed in Bulletin No. 103, July, 1915, pp. 1443 to 1447. ROBERT M. KEENEY, Somersville, Conn. (communication to the Secretary *).-There is not only a possibility of improvement in present methods of treatment of the byproducts of refining in the cyanide plant by the use of the electric furnace, but also in melting and refining of gold precipitate. This interesting paper by Mr. Lass shows an electric furnace in successful operation in a large plant for the treatment of by-products. Electric melting of cyanide precipitate is a cheaper form of treatment in many cases than any of the combustion methods now used because of the high cost of oil, coke or coal in many camps, while on the other hand electric power may be had cheaply, especially in a place where there is possibility of development of high-head hydro-electric plants for power purposes. Also, if the oil-fired tilting furnace is used for direct melting of the precipitate, as is the case at many small mills, a great saving in cost is made by the use of the electric furnace because of the high crucible cost in melting with the tilting furnace. A study of this paper indicates the cost of the operation approximately. Consider all the fluxes to be turned in as byproducts and coke at $18 per ton.

Jan 12, 1915

By John W. Cabot

The following series of analyses, which may, be of interest to Bessemer-steel makers, is submitted as a contribution to the muchvexed discussion of manganese in Bessemer steel. They were made by the writer in the spring of 1881, at the works of the Pittsburgh Bessemer Steel Company Limited, during a' period of about eight days, part of. which time the rail-steel showed great variation in rolling qualities. During the first part of tile time in question, it rolled well; later on it began to roll wome until, finally, it cracked very badly, reaching its worst stage. After this it rapidly improved until it again rolled smoothly. During this time of transition from good rolling to bad, and hack to good again, the course of the manganese was followed quite closely. It is the striking correspondence between these varying manganese contents and the differences in rolling which is here presented as worthy of notice. The other ordinary elements were determined occasionally, but showed no. unusual variation: The steel, in question, was ordinary rail-steel of about the following compusition : C=35. P - .08. Mn - .98. Si = .08. 8 = .06. The samples for manganese determinations were taken at first from an average of two days' work, and later on, when the steel

Jan 1, 1882

By D. W. Fuerstenau

Locked-cycle grinding experiments on mineral mixtures provide a means to study circuit performance in simulated continuous grinding systems. Such experiments with calcite/quartz mixtures revealed that approximately twenty-five 2-minute cycles are required before the composition of the circuit product and the recycle material attain steady state. The circulating load, after steadily increasing during the first 15 cycles, continued to fluctuate over a narrow range. Previous batch ball mill grinding of mineral mixtures has shown that breakage rate functions of minerals are time- independent but composition-dependent. In the closed-circuit grinding of ores with constituents having different grindabilities, the grinding rate parameters for the components also would therefore change during the transient period. With fluctuations in feed composition occurring randomly every half to one hour in processing plants, it is quite likely that the grinding circuit can be in unsteady state perpetually. The significance of these observations is discussed in this paper in the con- text of the models used in control schemes for the grinding circuits

Jan 1, 1984

By M. Cross

The main results from a programme of theoretical work on various aspects of the pelletizing operation are presented. This paper is primarily concerned with the modelling of: (i) The balling drum operation. A model is outlined which clearly demonstrates the characteristic surging behaviour of the balling circuit. It is used first in a control analysis and, subsequently, in the design and testing of various control schemes. (ii)The grate-kiln-cooler induration process. Models describing each of the constituent processes are outlined and a composite model of the whole induration process presented. The main results from each of these models are discussed.

Jan 1, 1977

By A. U. Seybolt

DURING the course of an investigation of hot corrosion of nickel-base superalloys (combination oxidation-sulfidation attack at high temperature), it was considered possible that sulfur might gain entrance to the alloy in part, at least, by diffusion through the scale. Cr203 is nearly always observed as a prominent component of the oxide scale, and hence some experiments were carried out to examine the tracer diffusion of sulfur through Cr203 at 1000° C in the upper temperature range experienced by jet engine blades and vanes. Some hot-pressed Cr203 discs of quite high density were available from an earlier investigation1 on the rate of crf3 migration through Cr203. The Cr203 was 99.3 pct pure and contained -0.06 pct Fe as the largest metallic impurity. Additional data is given in Ref. 1. In this earlier work it was found that the rate of cation diffusion was independent of the atmosphere of thermal equilibration when using nitrogen, argon, or air, and also that the electrical conductivity of the hot-pressed Cr203 compacts was likewise independent of atmosphere in this range, thus indicating that the de-

Jan 1, 1969

By J. K. Jeyapalan, A. P. S. Selvadurai

Plate loading tests which use surficial loading of a rock mass are employed quite extensively for the determination of in situ deformability characteristics of rock masses. The cable jacking method is essentially a surficial plate load test in which the test load is provided by reaction against a cable anchored at some depth below the rock surface. The results of the test are usually evaluated within the framework of the classical theory of elasticity to generate estimates for the bulk deformability properties of the rock mass. In the conventional evaluation of this test it is assumed that the test plate is rigid and that the embedded anchor load has no influence on the test plate settlement. The purpose of this paper is to examine the possible influences of the plate flexibility and the anchor load location on the effective settlement of the test plate. The variational estimates presented in the paper are valid for moderately flexible test plates which are characterized by a relative rigidity parameter Numerical results are developed in the form of correction factors that should be applied to the cable jacking results to arrive at the deformability characteristics of the tested rock mass.

Jan 1, 1982

By Ta M. Li

In Gila County, Ariz., the Jaquays Mining Co. still finds the mining of asbestos a worthwhile and economical venture. At a time when domestic productive capacity is being reduced because of rapidly rising costs and tough environmental dust standards, this firm has dramatically brought its mine and mill operation into full productive capacity and compliance with both Federal and State regulations. Jaquay's Mining Corp. owns four underground mines in the Tonto National Forest, located approximately 32 miles north of the Globe-Miami District in Arizona. Only one mine, the El Dorado, is presently active. It mines an estimated 45,000 tpy of ore and waste. From this figure about 3000 tpy of fiber (No. one crude to Grade 4T) and fiberized shorts (No, seven) are recovered at the firm's mill, located in Globe, Ariz. Based on current ore reserves, the El Dorado mine has an estimated life between 15 to 17 years, assuming current mining rates and stable market conditions.

Jan 3, 1975

By S. S. Hedge, J. C. Ferm, J. T. Berger

The coal procedures described in this paper address the problems building a body of coal data that is accurate, precise, readily available, and easy to manipulate. The system is a set of interactive computer procedures consisting of a) data gathering (core hole and geophysical logs, their location, elevation, etc.) and standardized computer printouts, b) the graphic outputs of coded logs (log strips-scale variable) wing on-line electrostatic plotter, c) determination of seam continuity via relative movements of the log strips on an interactive graphic display terminal, d) calculation of the seam parameters (minable seam thickness, volume of non-coal material in the seam, ash and sulfur content of the raw or prepared product, roof and floor characteristics and other attributes relevant to mining), e) posting of seam parameters wing on-line drum plotter controlled by a microprocessor on-line to the minicomputer (PDP- 11).

Jan 1, 1983

By D. F. DeSante, A. S. Tetelman

MICROCRACKS are often introduced into commercial metals during fabrication processes such as swaging, cold rolling, deep drawing, and welding. These microcracks act as strain concentrators and may be capable of causing premature catastrophic failure of a component or weld. The present investigation was undertaken to determine whether high-temperature annealing treatments may be capable of reducing or negating the detrimental effects of such existing microcracks. Internal microcracks, ranging from 0.1 to 0.85 mm in length and averaging 0.23 mm, were introduced into polycrystalline Fe-3 pct Si tensile specimens (0.155 mm grain size) by the cathodic charging of hydrogen.1'2 The typical appearance of such microcracks and their associated strain patterns (made visible by the technique of dislocation etch pitting3) is shown in Fig. 1. The stress fields of the dislocation loops formed during plastic relaxation stabilize the microcracks so that, when the internal hydrogen pressure is removed: the microcracks stay open, rather than disappear as perfectly elastic cracks would be expected to do.' As shown in Fig. 2, such stopped microcracks cause a 36 pct decrease in the macroscopic cleavage fracture strength at -196°C.

Jan 1, 1969

By W. M. Tuddenham, R. J. P. Lyon

In many areas surrounding the orebodies in mining districts rocks have been bleached and altered by the ore-forming solutions and have been oxidized during later weathering processes. A number of the rock-forming silic-ates have been broken down to clay, sericitic micas and chlorites have been developed, and pyrite may be found hundreds of feet outside the economic limits of the orebody. These halos of altered ground are prime targets used by geologists in many districts to delineate promising sites for drilling. Both in the field and in the laboratory it is often difficult to map these mineralogical changes in the halos in detail without numerous petrologic examinations. The secondary minerals are generally fine-grained, and since conversion of one mineral to another is often progressive, many alteration processes have not proceeded to completion (feldspars to clay to sericite mica). Qualitative detection of these minerals is difficult; quantitative determination is frequently impossible.

Jan 1, 1960

By J. L. Rodda

A large amount of time has been devoted to the microscopical study of the copper-zinc alloys, emphasis naturally being placed upon the commercially important alloys of the system. Suitable methods are available for microscopically recognizing the two phases richest in copper, but none appear to have been developed for the positive identification of the other phases. This is, however, accomplished, for the phases normally encountered, by an electrolytic method described in the following pages. Five phases of the copper-zinc diagram (Fig. I) are considered for the purpose of this paper: the solid solution of zinc in copper, alpha (a); the intermediate phases, beta (ß), gamma (?), and epsilon (e); and the solid solution of copper in zinc, eta (11). Beta prime is not considered a separate

Jan 1, 1937

By Peter F. Howard

Major reserves of phosphorite were found in the Georgina Basin of northern Australia in the period 1966-1968. Geological investigations by various companies and the Bureau of Mineral Resources of Australia show that these phosphorite deposits are associated with siltstones, cherts, siliceous shales, and limestones of the Beetle Creek formation or its equivalents, all of lower Middle Cambrian age. The discoveries resulted from systematic Australia-wide exploration programs by several companies utilizing, in concept, the relation of basin stratigraphy, lithologic associations, tectonics, and phosphate occurrences to paleogeography in respect to its paleolatitude and areas of supposed oceanic upwelling. In terms of field techniques, the first discovery at Duchess, North Queensland, resulted from the recognition of a phosphorite interval at depth in a stratigraphic oil well followed by prospecting of the nearest outcrop of the equivalent aged rock succession. In Northern Territory, the Wonarah-Alexandria deposits, which do not crop out, were discovered by analysis and interpretation of gamma radiation logs followed by drilling.

Jan 1, 1972

By Felix Wunsch

WHILE the effect of the cold-junction temperature has been known by many, its consideration has been ignored in a number of installations, resulting at tunes in a very considerable error. In fact, the magnitude of this error may amount to over 100° in some cases. While hand-operated correcting devices for portable checking pyrometers may be entirely satisfactory, it is, of course, desirable to have such apparatus en¬ Millivoltmeter Thermocouple Platinum Wire Mercury FIG. 1.-EARLY `METHOD OF AUTOMATICALLY COMPENSATING FOR COLD-JUNCTION TEMPERATURE CHANGES. tirely automatic, when applied to curve-drawing or printing pyrometers, otherwise there is no assurance that the record is correct. Numerous methods for automatically compensating for cold-junction temperature changes of thermocouples have been proposed and used in connection with millivoltmeters. One of the earliest proposed was that shown in Fig. 1. A bare resistance wire was immersed in a column of mercury located near the cold junction of the thermocouple. An increase in temperature near the cold junction resulted in a rise of the mercury column, which short-circuited more of the resistance wire causing an increase in the potential difference across the millivoltmeter, which compensated for the decreased electromotive force of the thermocouple.

Jan 9, 1919

By W. M. Aubrey, P. L. Steffensen

AUTOMATIC grinding control for ball mills in closed circuit with cyclones was developed for the concentrator of the Marmoraton Mining Co., a subsidiary company of Bethlehem Steel Corp. The concentrator, located at Marmora, Ont., Canada, treats an ore that analyzes 35 to 40 pct magnetic iron. Magnetite, the recoverable iron mineral, is concentrated by fine grinding and magnetic separation. The mesh of grind obtained in the plant is not determined by the point at which liberation is sufficient to yield a satisfactory grade of concentrate, but by the physical requirements of the downstream pelletizing operation. This is considerably finer than is metallurgically necessary. The concentrator has two identical units, each consisting of a rod mill in open circuit, followed by a ball mill in closed circuit with a cyclone and two rougher magnetic separators. The cyclone was chosen as a classifier because of its high efficiency on heavy gravity, magnetically flocculated material.

Jan 1, 1957

By P. F. Mataich

When the subject of plant computers is brought up most people visualize the computer's con- trolling the entire plant with very little operator intervention. Actually, this picture is true today in only a limited number of cases and will certainly not be true in the minerals industries for many years to come. There are several ways in which a plant computer can significantly contribute to improving plant operation and closed loop control is only one of these. First of all, for good plant control, two basic requirements must be met. First, the operator must get good information feedback from the process and then he must know what action to take in response to this information. Control information can be obtained through instruments, laboratory analyses, or through simple visual observation. If it is timely and accurate and the operator knows how to use it, then we have the makings of a good plant control system. The computer can be of help in both these areas by getting good data back to the operator and in helping to develop a good control scheme for the plant.

Jan 12, 1966

By Gary E. Butts, Paul R. Smith

Introduction The design of a mineral processing flowsheet involves many factors. The importance of the sample can not be overemphasized. Competent and thorough mineralogical examinations are important as an aid in designing the test program. Designing and conducting the laboratory test program is basic to the design of the flowsheets. In the project under consideration a flotation pilot plant was conducted to prove the process and to provide a realistic prediction of metallurgical results. Moreover, the pilot plant operation provides important pilot plant design data. Finally, accurate and clear reporting is essential so that the information developed can be utilized advantageously by the client and the engineering firm. The design of a minerals processing flowsheet is a team effort. Engineers from the mining company, the research organization, and the engineering firm all contribute to the effort.

Jan 1, 1978

NEW MEMBERS The following list comprises the names of those persons who became members during the period Sept. 10 to Oct. 10, 1915: Members BENEDICT, C. HARRY, Met Calumet & Hecla Mining Co., Calumet, Mich. BETTERTON, JESSE OATMAN,. Met., Supt. Blast Furnaces and Sulphate Depts., St. Louis Smelt. & Ref. Co., Collinsville; Ill. CLARK, H. A., Supt Calumet & Arizona Mining Co., Douglas, Ariz. COOPER, CLAUDE H.; Asst,. Supt Calumet & Hecla Smelt. Works, Hubbell, Mich. CRAMPTON, FRANK A., Min. Engr.; Mine Supt., Platinum Gold Min. Co., Goodsprings, Nev. CUNNINGHAM, GEORGE HAMILTON, Asst. Supt. of Construction, Anaconda Copper Mining Co., Anaconda, Mont.

Jan 11, 1915