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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 R. B. Mears, G. F. Sagar, R. H. Brown

There are well recognized procedures for determining the various tensile, fatigue, and other mechanical properties of the common structural materials. This makes it possible for engineers to design structures of various materials which have adequate initial strength to stand the stresses to which they are subjected in service. There is also considerable general information about protective measures suitable for protecting the usual structural materials from the effects of ordinary environments. However, often insufficient quantitative information is available on the combined effects of stress and corrosion to permit the designer satisfactorily to appraise the structure from the stress-corrosion standpoint. This situation is further complicated by the fact that the stresses causing stress¬corrosion failures are usually not the design stresses but rather the residual forming and assembly stresses which are generally of unknown magnitudes. Thus, tests which will rapidly evaluate the susceptibility of materials to stress-cor¬rosion failures are extremely useful. Of particular value are tests which can be applied to built-up structures as well as to simple specimens, since, as mentioned above, residual stresses often are caused by fabricating procedures and assembly operations. The present paper contains

Jan 1, 1945

By W. E. D. Jr. Stokes

THE application of aviation to mining and petroleum operations, on the basis of economy and attainment, has become a demonstrated fact. According to Dominion Government records, 30 Canadian companies engaged in air transportation with northland mining camps, carried 13,000 tons of freight in 1935, and in 1936 carried 16,000 tons. In addition, many mining companies used planes to transport prospectors with canoes, outboard motors, gasoline drums and supplies to remote locations, and one company maintained a plane to take radium-bearing ore from its mine on Great Bear Lake nearly 1000 miles south to the rail-way at Waterways, Alberta. Heavy pieces of mining machinery weighing 2 tons are being carried by Ford trimotor planes over the Andes, at an altitude of not less than 15,000 feet. At Bulolo, New Guinea, 17,500 tons of disassembled gold-dredging equipment has been flown over inaccessible terrain, while supplies and building materials for a community of 1000 whites have been transported by airplane. A 31 z-ton shaft was carried on one notable trip, while at another time an automobile, 2 tons of rice and a large safe went over the mountains in one plane. Fig. 1 shows an electric generator that was carried by plane to Bulolo. Many large American oil companies operated fleets of planes during 1936, ranging from fast, luxurious air liners for executives to elaborate geological prospecting units, ambulance planes, freight carriers and pipe-line repair crews.

Jan 1, 1937

By H. J. Wasson

With the close of 1932 and the third year of the depression, the activity of oil production presents, amidst the general wreckage and chaos of industrial society, a somewhat unique picture of rationalized economic effort. How long it will continue to present such a picture, however, is a subject for conflicting surmises. East Texas still dominates the contemporary horizon, but it has become, at least for the time being, a definitely known factor. With its 9500 wells it is approximately 90 per cent drilled up. So long as production control obtains, it is merely one important factor of the national oil reserve. Domestic Production The notable new discoveries in the United States were less numerous than for several years. Elsewhere in the world the record is much the same. The Conroe field in Montgomery County, Texas, lying in an intermediate zone that might be classified either as Gulf Coast or East Texas, represents perhaps the single example of a truly major discovery during the year. Elsewhere in Texas the new pool discoveries, about a dozen or so in number, were nearly all in the region known as Southwest Texas. Oklahoma contributed seven or eight new pools of the routine "run-of-mine" caliber, and the opening up of a few deeper oil pays also were of some significance. Continued expansion of the proved and semiproved reserves in Kansas added an important increment to the oil resources of that state. In California not a single new field was added to the roster, though deeper pay zones equivalent to or of greater importance than many new fields in other parts of the country were discovered or indicated. The new deep zone in the Belridge field is considered by some to underlie the prolific Temblor and may thus forecast the widespread distribution of a potentinl oil horizon underlying many San Joaquin Valley fields below the depths thus far exploited. Aside from the routine operations in connection with settled production, the Eastern fields were decidedly inactive. Further new develop-

Jan 1, 1933

By J. Parke Channing

IT, HAS been my privilege to be Chairman of Engineering Council for very nearly three years, during which time Mr. A. D. Flinn, the. Secretary, and myself, have seen the organization develop until it is functioning smoothly and accomplishing what it can with the money at its disposal. The earliest attempt at what may be called an Engi¬neering Council, of which. I have any knowledge, was made six or seven years ago when the four Founder Societies each appointed two men, who occasionally met to discuss matters submitted to them which were of importance to, the, profession as a whole. I was one of the representatives of the American Institute of Mining Engineers.

Jan 1, 1920

By W. W. Anderson, S. Razi

Electroluminescetrce of single crystals of terbium-(loped ZnS prepared by vapor-transport technique shows the sharp line specirum characteristic of the 4f— 4ft,ansitiotzs of the trivalent Tb3 rotz. V-I tt~easuverr~ents give evidence of space-ellarge-lirrlited curvent but the thrveshold for trap-filled law behavior is not iu agreement with Lampert&apos;s theory for. Single injection. Variations of &apos;brightness with applied voltage, the observation of double peaks its brightness because joms, and the spatial distribution oi electroLur?zir~escerrce indicate that the accelet~atiotz-collision mechanism involving the bst lattice and/ov shallow traps is most likely to be responsible fov excitation of&apos; electrolnminescence. Efficiency rtreusuver)~etits show the quantwn efficiency to be about 10 pct and powev efficiency about 0.05 pct. Effect of anr~eallng the crystal in sulfur vapor is to enluztzce llle rare-earth emission. It rs pvoposed tlzat sulfitv anr~ealing crreates acceptorr-lvpe defects with which the donor-type vare-eavtll ion can associate more readily vesulting in enhanced rare-earth emission. A&apos;o such e~zlznr~cerr~etrt is obserued when the crystal is atztrealetl in zinc vapor. Photolianinescence of ZnS doped nith a variety of rare earths also shows tile slurvp l~rze rwve-eavtlz erriission which in sorrretirr~es accompanied by broad band, stvuctureless lattice emission. Photo-atrd electrolutr~itzesce?~ce of ZIIS:Tb slw~rj do!rlit~unt rare-earth emission in the ~ticirzity of 54(3OA corre-sporrdit~g to the transition D* — Fj. Hoz~!el)er, the detailed line structuve of the luo spectvtr is cliffevet~t, irzdicutit~g that different sites are active in the two processes. Decay of rave-eartlr fluorescence in ZnS doped with any of sei!evul vuve eurtlzs car1 be described by a single exporleritial e.scepl joy ZrlS:lIo. Tl~is exceptiotr can be explaitred it~ tevrr~s of tlre closely spaced er~evgy 1e1:els Jov the HO~&apos; iorr. Decay lime measurertzekzts jov ZnS:Tb, using pulsed elect,-ical ar~d pulsed opticcll excitutiorzs, (11-e itz goor1 agrcetrier~t. LUMINESCENCE of rare-earth-doped materials has been a subject of interest for the past 20 years. Within the past few years there has been a considerable increase in rare-earth research motivated in search of new and more efficient laser materials and also due to the use of certain-rare-earth compounds in the preparation of color television screens. The purpose of this study has been to seek an understanding of some of the basic processes involved in exciting the rare-earth luminescence which is associated with transitions within the 4f shell of the trivalent rare-earth ion. Single crystals of ZnS doped with a variety of rare-earth ions have been prepared by vapor-transport technique described elsewhere.&apos; Photoluminescence was excited by a high-pressure short-arc mercury lamp together with suitable glass and chemical filters. For electroluminescence, sinusoidal and pulse excitations were used. 1) ELECTRICAL CHARACTERISTICS 1.1) V-I Measurements. Electroluminescence experiments were performed on crystals of terbium-doped ZnS. The samples were cleaned and etched and indium or In-Ga alloy contacts were alloyed on by heating in H2 atmosphere to 600°C for times ranging up to 10 min. Static voltage-current measurements were made on several samples. Fig. 1 shows the results for a typical sample. For voltage V < 20 v, the V-I relationship is linear giving a resistivity of 2.5 x 109 ohm-cm for this particular sample at room temperature. In the range of 20 to 250 v, I varies as V "3 and at still higher voltages (when electroluminescence is visible to the scotopic eye) current varies as Vs up to 600 v, all at room temperature. At 77"K, for V > 200 v, / I vge5 up to 1000 v. The V-I characteristics at room temperature follow reasonably well the behavior predicted by Lampert&apos; for one carrier space-charge-limited current in an insulator with traps although, as shown later, the expression derived by Lampert2 for the threshold for trap-filled law behavior Vtfl yields an unrealistically low value for trap density if we use the experimental value of 300 v for VtfL. Assuming the case for shallow trapping, the transition from Ohm&apos;s law behavior to space-charge-limited behavior occurs at voltage Vtr given by where no = thermally generated free carrier density, L = length of the sample, e = static dielectric constant, 6 = ratio of free to trapped electron densities, e = electron charge. For the ZnS:Tb crystal, L = 0.5 mm, E = 8.3 €0, Vtr - 20 v, and no = 5 x 10&apos; per cu cm, calculated from the ohmic behavior assuming electron mobility of 100 sq cm per v-sec. This results in 9 = 0= As more and more electrons are injected the Fermi level moves up in the forbidden gap toward the conduction band. If we assume a single-energy level for traps (which is not strictly correct, as we will show later), the current voltage characteristic is profoundly affected when the Fermi level crosses the trap level. The traps are now filled and injected carriers can no longer be immobilized in traps. Hence, current rises sharply with voltage. The transition from space-charge-limited behavior to the trap-filled behavior occurs at voltage VTFL given by

Jan 1, 1968

By AIME AIME

FRANCIS ANDREW THOMSON was born in London, Dec. 21, 1879, coming to the United States by way of British Columbia where he lived until he matriculated at the Colorado School of Mines. When only sixteen he was inducted into the mining industry as apprentice assayer and millman at the Victoria Metallurgical Works. Following his training at Golden he had more practical mining and milling experience at several properties in the West, and studied a little as well at the Royal School of Mines, in London, and at the Ecole des Mines, in Paris.

Jan 1, 1939

By W. C. Ellis, E. S. Greiner

METALLIC titanium has been prepared in small quantities since the beginning of the century. Hunter1 reported in 1910 that he obtained a malleable product of 99.9 pct purity by the reduction of the tetrachloride by sodium in a closed container. Later Van Arkel2 and Fast3 prepared small quantities of malleable titanium by thermal decomposition of titanium iodide. Another method for producing malleable titanium from tetrachloride was reported by Kroll4 who used magnesium as the reducing agent. More recently Dean, Long, Wartman, and Anderson5 working at the U.S. Bureau of Mines have reported the preparation of the metal on a pilot plant scale by the reduction of titanium tetrachloride by magnesium in an atmosphere of helium. Their product, which is malleable, was used in the present investigation. Early in 1948 after the work of this paper: was completed Campbell, Jaffee, Blocher, Gurland, and Gonser6 described the strength and working characteristics of pure titanium which was prepared by the iodide method on a scale producing 300 to 600 g per run, in the form of 0.3- to 0.4-in. diam rods. Their product is characterized by low hardness and large capacity for cold work which they attribute to a high degree of purity with respect to oxygen, nitrogen, and carbon. Titanium has a melting point of about 1725°C5 it may be classed as a light metal since the specific gravity is 4.5 g per cc-1. The crystal structure is close-packed hexagonal from room temperature t0 885°C. Above this temperature the structure is reported7 as body-centered cubic. The change in crystal structure has been associated with discontinuities in specific heat8 electric resistance9 and thermoelectric force10 at temperatures near 890°C. It is reported11 that annealed titanium has a tensile strength 0f 78,700 psi which can be increased by cold-work to 123,000 psi. In the present investigation, the lattice constants at room temperature, the thermal expansivity between 30 and 800°C, as well as the electrical resistivity and thermoelectric force against platinum between - 200 and 1000°C have been determined. MATERIALS For the measurements, two series of specimens were prepared from titanium furnished by the U. S. Bureau of Mines. The first was lade from an annealed sintered compact, 0.38 in. thick. Sections of the compact were cold-swaged with intermediate anneals in vacuum to the sizes used. Sizes over 0.25-in. diam were annealed at 1000°C and smaller sizes at 800°C. Specimens originating from the sintered compact are designated in this paper as A. The second series of specimens was lade from a rod of titanium, 0.19 in. in dial, which was cold-swaged with the necessary intermediate anneals to the required sizes. This series of specimens is designated B. The impurities in the specimens of titanium, determined by chemical analysis, are given in Table I. Oxygen and nitrogen which were not determined by analysis, are probably present although in small quantities in view of the ductility of the material.

Jan 1, 1948

Herbert C. Hoover, who became a member of this Institute in 1896 and who is now one of its Vice-Presidents, is the man who in 1914 extended a helping hand to Americans stranded in Europe at the outbreak of the war, and who made it possible for many such travelers to return safely to their homes. When his countrymen no longer needed his services, he turned to the Belgians, whose need of food had been presented to him. Engineers have been among his assistants from the first, and it is because we believe that members of his own profession will still be particularly interested in his work that we thus mention it in the Bulletin. A Minute adopted by the Board of Directors of the Institute, in which the Belgian Kiddies, Ltd., is recommended to the consideration of the members, immediately follows the Proceedings of the Meeting of the Board of Directors. With the thought that members of the Institute may be glad to read Mr. Hoover&apos;s own words in regard to his work, we print in full the speech

Jan 3, 1917

By Lewis Blanchard Brown

It is my purpose in the following paper to describe the south-central part of Siberia, with special reference to its geology and the mineral deposits. This region is known politically as the Achinsk and Marinsk districts of the Tomsk Government. It is situated among the Altai mountains, in. ]at. 50° to 55O n and long. 87O to 93O E., not far from the northern frontier of Mongolia, and is divided as follows: Mining Districts.—(1) The Tomsk mining district, including the political districts of Altai (belonging to the private crown lands of the Russian Emperor) and Marinsk; (2) the AchinskMinusinsk mining district, including the political districts of Achinsk and Minusinsk; and (3) the North Yenisei mining district, situated in the northern part of the Yenisei political district of the Yenisei Government. Fig. 1 is a map of the Tomsk mining provinces, showing the useful mineral-deposits, excepting those of gold, and giving the routes of the railroads and post-roads connecting the various districts. Political Divisions.—The Tomsk Government is sub-divided into seven " oojesdy " or districts, as follows: Barnaul; Biisk; Kuznetsk; Kainsk; Kolyvan; Marinsk; Narim; and the Altai district (private land, as above). The Yenisei Government is sub-divided into five "oojesdy" or districts, as follows : Erasnojarsk ; Kansk; Yenisei; Achinsk; Minusinsk. Concerning the geology of the region, in addition to the record of my own observations, references will be made to the works of earlier writers. These have been consulted for the purpose of comparison, as regards the districts which I have actually traversed, and for the purpose of completing my account of such portions as I have not been able to visit.

Jan 1, 1904

By Anthony Anable

THE definite trend to stricter specifications with respect to hydraulic concrete has become increasingly manifest in the last six years or so; but it remained for the vast reclamation projects of the Bureau of Recla-mation of the Department of the Interior of the last few years to focus attention on this trend, and to demonstrate how thousands of tons of concrete-making aggregates can be produced continuously and auto-matically with a control of fineness comparable with that obtained with small samples in well equipped private and governmental laboratories. Pioneer work in this direction was done, to be sure, by private com-panies, notably the Kaiser Paving Co. of San Francisco, prior to the present vast public works program. Then in 1931 came the first great aggregates-preparation plant of the Six Companies, Inc. to supply. construction materials for Boulder Dam&apos; in Nevada, and now, in 1936, the aggregates plant of the Mason-Walsh-Atkinson-Kier Co., general con¬tractors on the Grand Coulee dam in Washington. At Boulder dam and to an even greater degree at Grand Coulee dam, sand production is recognized as probably the most important single element affecting the physical characteristics of the concrete. For in the construction of dams accurate grading of the fine aggregate has consider-able bearing on the attainment of a uniform and homogeneous concrete of a high degree of workability and placeability and, at the same time, combining high density and low cement content. Low cement content is of value not only from the standpoint of economy but also because the use of an unnecessarily rich concrete causes certain undesirable characteristics to develop. This paper will relate how at Grand Coulee dam methods that are more advanced than ever before are producing four sizes of gravel and a sand having a fineness modulus of 2.5-3.0. The design capacity is 1000 tons an hour. Significantly, the methods and equipment employed are broadly those that have been used for a generation in metallurgical mills for accurately sizing and grading both precious

Jan 1, 1936

By Anthony Anable

The definite trend to stricter specifications with respect to hydraulic concrete has become increasingly manifest in the last six years or so; but it remained for the vast reclamation projects of the Bureau of Reclamation of the Department of the Interior of the last few years to focus attention on this trend, and to demonstrate how thousands of tons of concrete-making aggregates can be produced continuously and automatically with a control of fineness comparable with that obtained with small samples in well equipped private and governmental laboratories. Pioneer work in this direction was done, to be sure, by private companies, notably the Kaiser Paving Co. of San Francisco, prior to the present vast public works program. Then in 1931 came the first great aggregates-preparation plant of the Six Companies, Inc. to supply construction materials for Boulder Darn1 in Nevada, and now, in 1936, the aggregates plant of the Mason-Walsh-Atkinson-Kier Co., general contractors on the Grand Coulee darn in Washington. At Boulder dam and to an even greater degree at Grand Coulee dam, sand production is recognized as probably the most important single element affecting the physical characteristics of the concrete. For in the construction of dams accurate grading of the fine aggregate has considerable bearing on the attainment of a uniform and homogeneous concrete of a high degree of workability and placeability and, at the same time, combining high density and low cement content. Low cement content is of value not only from the standpoint of ceonomy but also because the use of an unnecessarily rich concrete causes certain undesirable characteristics to develop. This paper will relate how at Grand Coulee dam methods that are more advanced than ever before are producing four sizes of gravel and a sand having a fineness modulus of 2.5-3.0. The design capacity is 1000 tons an hour. Significantly, the methods and equipment employed arc broadly those that have been used for a generation in metallurgical mills for accurately sizing and grading both precious

Jan 1, 1938

By Anthony Anable

The definite trend to stricter specifications with respect to hydraulic concrete has become increasingly manifest in the last six years or so; but it remained for the vast reclamation projects of the Bureau of Reclamation of the Department of the Interior of the last few years to focus attention on this trend, and to demonstrate how thousands of tons of concrete-making aggregates can be produced continuously and automatically with a control of fineness comparable with that obtained with small samples in well equipped private and governmental laboratories. Pioneer work in this direction was done, to be sure, by private companies, notably the Kaiser Paving Co. of San Francisco, prior to the present vast public works program. Then in 1931 came the first great aggregates-preparation plant of the Six Companies, Inc. to supply construction materials for Boulder Darn1 in Nevada, and now, in 1936, the aggregates plant of the Mason-Walsh-Atkinson-Kier Co., general contractors on the Grand Coulee darn in Washington. At Boulder dam and to an even greater degree at Grand Coulee dam, sand production is recognized as probably the most important single element affecting the physical characteristics of the concrete. For in the construction of dams accurate grading of the fine aggregate has considerable bearing on the attainment of a uniform and homogeneous concrete of a high degree of workability and placeability and, at the same time, combining high density and low cement content. Low cement content is of value not only from the standpoint of ceonomy but also because the use of an unnecessarily rich concrete causes certain undesirable characteristics to develop. This paper will relate how at Grand Coulee dam methods that are more advanced than ever before are producing four sizes of gravel and a sand having a fineness modulus of 2.5-3.0. The design capacity is 1000 tons an hour. Significantly, the methods and equipment employed arc broadly those that have been used for a generation in metallurgical mills for accurately sizing and grading both precious

Jan 1, 1938

By M. R. Geer, J. D. Davis, H. F. Yancey

ALTHOUGH the mechanical cleaning of coal is carried out at plants on the surface, preparation is actually begun at the face in the mine. Here the character of the coal and the amount, character, and distribution of the impurities within the bed may be seen. Blasting methods, dust-allaying procedures, location of mining cut with respect to bands of impurity, and the practice of discarding segregated impurities underground, all have an important bearing on the successful operation of surface cleaning units. The most important single characteristic of both coal and its associated impurities from the standpoint of cleaning is specific gravity. Other characteristics related in one way or another to the preparation , of coal are rank, petrographic composition, structure and hardness, and friability. These and still other coal properties are discussed in the first section of this chapter and impurity characteristics in the second. COAL CHARACTERISTICS RELATED TO PREPARATION Rank As a result of work done over a period of several years by committees of the American Society for Testing Materials and the American Standards Association, standard specifications are now available showing the &apos;classification of coals according to rank and quality of grade.&apos; The term "rank" expresses the degree to which the original coal-forming material has been changed by metamorphism through successive stages from peat to anthracite. Table 1 shows the classification of coals according to rank as devised by the committees of the organizations mentioned. The basic scheme of classification for the higher-rank coals is according to

Jan 1, 1943

By M. R. Geer, J. D. Davis, H. F. Yancey

ALTHOUGH the mechanical cleaning of coal is carried out at plants on the surface, preparation is actually begun at the face in the mine. Here the character of the coal and the amount, character, and distribution of the impurities within the bed may be seen. Blasting methods, dust-allaying procedures, location of mining cut with respect to bands of impurity, and the practice of discarding segregated impurities underground, all have an important bearing on the successful operation of surface cleaning units. The most important single characteristic of both coal and its asso¬ciated impurities from the standpoint of cleaning is specific gravity. Other characteristics related in one way or another to the preparation of coal are rank, petrographic composition, structure and hardness, and friability. These and still other coal properties are discussed in the first section of this chapter and impurity characteristics in the second. COAL CHARACTERISTICS RELATED TO PREPARATION Rank As a result of work done over a period of several years by committees of the American Society for Testing Materials and the American Standards Association, standard specifications are now available showing the classification of coals according to rank and quality of grade.&apos; The term "rank" expresses the degree to which the original coal-forming material has been changed by metamorphism through successive stages from peat to anthracite. Table 1 shows the classification of coals according to rank as devised by the committees of the organizations mentioned. The basic scheme of classification for the higher-rank coals is according to

Jan 1, 1943

By Victor O. Homerberg, Dexter N. Shaw

A study of the correlation of the mechanical properties and of the microstructure with the heat treatment of 60-40 brass has been confined, heretofore, to the rolled or extruded material as received from the mannfacturer. The results obtained by Babson and Buhler,&apos; Bengough and Hudson12 Stead and Stedman,3 and Brayton4 have been confined to the treatment of the material as received. No attempt was made to get the material into a given condition and then to work from this basis. To start with a given structure would have the decided advantage of making the work independent of the original condition, hence, to make the results reproduceable. In a previous paper, it was shown, in connection with the study of the transformation that occurs at about 470" C., that if specimens were quenched to produce the beta structure and then reheated, the beta would begin to break down, at approximately 200" C., into a very finely divided alpha. It was predicted that important results might be obtained if test pieces were to be given a similar double heat treatment and then tested for the mechanical properties as well as a study of the microstructure. The material used in the present investigation was a 3/4-in. round bar of extruded muntz metal of the following composition: Copper, 61.05 per cent.; zinc (by difference), 38.90 per cent.; lead, 0.05 per cent.; iron, trace; tin, nil.

Jan 1, 1924

By Victor Homerberg

A STUDY of the correlation of the mechanical properties, and of the microstructure with the heat treatment of 60-40 brass has been confined, heretofore, to the rolled or extruded material as received from the manufacturer. The results obtained by Babson and Buhler,1 Bengough and Hudson,2 Stead and Stedman,3 and Brayton4 have been confined to the treatment of the material as received. No attempt was made to get the material into a given condition and then to work from this basis. To start with a given structure would have the decided advantage of making the work independent of the original condition, hence, to make the results reproduceable. In a previous paper, it was shown, in connection with the study of the transformation that occurs at about 470° C., that if specimens were quenched to produce the beta structure and then reheated, the beta would begin to break down, at approximately 200° C., into a very finely divided alpha. It was predicted that important results might be obtained if test pieces were to be given a similar double heat treatment and then tested for the mechanical properties as well as a study of the microstructure. The material used in the present investigation was a ¾ -in. round bar of extruded muntz metal of the following composition: Copper, 61.05 per cent.; zinc (by difference), 38.90 per cent.; lead, 0.05 per cent.; iron, trace; tin, nil.

Jan 3, 1924

By B. A. Rogers, K. O. Stamm

BECAUSE it is the basis of the economically important operation of hardening steel by quenching, the A3 transformation in iron has been the subject of numerous investigations. Although the contributions to this subject are interesting, no general review will be given here. Readers who care to follow the matter further are referred to the comprehensive summary by Cleaves and Thompson,1 which covers the literature to about 1935. Their references to 53 papers on the subject suggest that further investigation is hardly justifiable. However, considerable interest has developed recently concerning the reversibility of the transformation. From thermodynamic considerations, the transition ought to occur at the same point on heating or cooling, if the change of temperature is sufficiently slow. Yet all of the earlier investigators found a difference of several degrees. Burgess and Crowe,2 who used thermal methods, obtained average temperatures of 912° for Ac3 and 900°C. for Ar3 on electrolytic iron. Their data indicate a considerable range of temperature over which the change occurs, both on heating and on cooling. Terry3 measured the susceptibility in the critical range and estimated from the steepest parts of his curves that Ac3 came at 9180 and Ar3 at 903°C. Ishiwara4 was one of the first investigators to report a shorter interval between the temperature of the change in the two directions. He measured the change of susceptibility of kaolin-coated samples of steel, in a hydrogen atmosphere, at rates of heating and cooling so low that about 3 or 4 hr. were required for the transformation to complete itself. His results show some variability between samples, but indicate that the difference between Ac3 and Ar3 is in the vicinity of 6°C. Roberts and Davey5 measured the space lattice in pure iron in the vicinity of 900°°C. and concluded that a change occurs reversibly between 907° ± 3° and 9100 ± 3°C., probably between 907° and 910°C. Wells, Ackley, and Mehl6 made dilatometric determinations of the Ac3 and Ar3 points in samples of hydrogen-treated carbonyl iron maintained under a vacuum. They used three rates of heating and cooling: 2°, &apos;1/2°, and 1/8°C. per min. and found the spread between the two points decreased with low rates. At the slowest rate, the Ac3 transition occurred at 909° to 909.5°C. and the Ar3 change at 907°C. in three of the samples believed to contain the lowest percentages of alien elements. They concluded that if the rate of temperature change and the content of alien elements were low enough, the A3 transformation would be completely reversible at 909.5° ± I°C. The question of reversibility is an interesting one and when some iron with especially small percentages of alien elements became available the opportunity to conduct an investigation was welcomed. This iron was prepared by the Division of

Jan 1, 1941

HENRY M. HOWE, Bedford Hills, N. Y. (communication to the Secretary *).-Dr. Burgess would add to the value of this important paper if he would give us the carbon content of the steel made in the several charges, or, if this cannot be done, if he would indicate whether, as might he inferred from his paper, the teeming temperature is approximately constant and independent of the carbon content of the steel, or whether as would be expected, it varies with the content and is materially higher for low- than for high-carbon steel. If he could add to Table 3 the time of the several tests, that would be welcome. His Table 3 leads one to infer that, once the bath is melted somewhat more than flat, the temperature of the roof is nearly constant and is approximately the highest compatible with reasonable longevity. That is to say, the metal is heated by means of a roof and flame at nearly constant temperature. The temperature of the observed upper surface of the slag should reflect that of the roof approximately, and in Table 3 this seems to be true, the temperature of both rising toward the middle of the record, and again falling. The slag as the medium through which the heat passes from roof to metal, should be intermediate in temperature between the two, as it is here. But the temperature of the metal ought to rise continuously, unless when cold additions are charged, and this too seems to be. true, allowing for slight observational errors, the total rise from the first to the last spoon-test being 89°. The temperature drop of from 85° to 135° from the last spoon-test to the teeming is surprisingly great, suggesting that the spoon-tests represent the metal immediately beneath the slag, and therefore appre-

Jan 6, 1917

By Anthony Anable

THE definite trend to stricter specifications with respect to hydraulic concrete has become increasingly manifest in the last six years or so; but it remained for the vast reclamation projects of the Bureau of Recla-mation of the Department of the Interior of the last few years to focus attention on this trend, and to demonstrate how thousands of tons of concrete-making aggregates can be produced continuously and auto-matically with a control of fineness comparable with that obtained with small samples in well equipped private and governmental laboratories. Pioneer work in this direction was done, to be sure, by private com-panies, notably the Kaiser Paving Co. of San Francisco, prior to the present vast public works program. Then in 1931 came the first great, aggregates-preparation plant of the Six Companies, Inc. to supply construction materials for Boulder Dam&apos; in Nevada, and now, in 1936, the aggregates plant of the Mason-Walsh-Atkinson-Kier Co., general con-tractors on the Grand Coulee dam in Washington. At Boulder dam and to an even greater degree at Grand Coulee dam, sand production is recognized as probably the most important single element affecting the physical characteristics of the concrete. For in the construction of dams accurate grading of the fine aggregate has consider-able bearing on the attainment of a uniform and homogeneous concrete of a high degree of workability and placeability and, at the same time, combining high density and low cement content. Low cement content is of value not only from the standpoint of economy but also because the use of an unnecessarily rich concrete causes certain undesirable characteristics to develop. This paper will relate how at Grand Coulee dam methods that are more advanced than ever before are producing four sizes of gravel and a sand having a fineness modulus of 2.5-3.0. The design capacity is 1000 tons an hour. Significantly, the methods and equipment employed are broadly those that have been used for a generation in metallurgical mills for accurately sizing and grading both precious

Jan 1, 1936