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By John F. Lundeberg

CLAUSS1 observed that if isothermal creep data could be approximated as straight lines on a log stress-log time plot, a relationship existed that could be expressed as log t = m log s + b [ l] where t = time,

Jan 1, 1965

By E. S. Grumell

THE correct sampling of coal and coke is becoming important to an ever increasing number of producers and consumers. This, therefore, may be an opportune moment to examine where we stand with regard to existing and proposed methods. In this paper an attempt will be made to review, as briefly as possible, some of the considerable amount of painstaking research which has been done in the last 10 years, and which has unquestionably led to a much better understanding of the subject. In so doing we shall try, on the one hand, to make clear where substantial progress has been made, and on the other hand, to draw attention to points that require further investigation. The paper is divided into sections in order to emphasize the major divisions of the subject; further, in order to retain this emphasis, detailed consideration of some of the points has been relegated to appendixes. No attempt has been made to give a complete survey of the literature, as this has already been done by L. A. Bushell.2 The following abbrevia-tions will be used: A.E., average error; P.E., probable error; S.W.R., size-weight ratio; B.S.I., British Standards Institution.

Jan 1, 1939

By J. N. Ong, J. P. Ratledge, J. H. Boyce

Since German operators opened the Tsumeb mine in the early 1900's, continuous operation has been interrupted only by enforced shutdowns during two world wars and the depression of the 1930's. Original metallurgical practice was blast furnace smelting. This was applicable only to low zinc ore, leaving large tonnages of high zinc ore to be stockpiled on the surface. A gravity concentrator using tables, buddles, and jigs operated for several years, but differential flotation of the ore did not get beyond the experimental stage. When the property was put up for sale by the South African Custodian of Enemy Property there was an estimated 434,000 tons of ore on surface dumps. The dump material, assaying 4.48 pct Cu, 15.8 pct Pb, and 10.9 pct Zn, had become highly oxidized during a stay of many years on the surface. But these dump ores had to be used in evaluating possible metallurgy because the shaft became flooded after the 1940 shutdown and underground ore was unavailable. Many companies examined Tsumeb but quickly lost enthusiasm because of the formidable metallurgical problems presented by the dump ore. However, on the basis of extensive test work, the present company decided that differential flotation would be successful and purchased the property after competitive bidding.

Jan 4, 1955

Year of Election 1944 Walter Hull Aldridge, New York, N.Y 1955 Louis S Cates, New York, N.Y 1946 William Fraser (Lord Strathalmond), London, England 1917 Herbert Hoover, New York, N Y 1955 George M Humphrey, Cleveland, 0

Jan 1, 1959

By C. W. Mason

TIN has long been cited as offering a classic example of polymorphism, second in repute only to the allotropy of sulphur. The notorious "tin disease," which Cohen1 has studied so exhaustively in terms of the enantiotropic transformation of tetragonal white 0 tin to cubic gray a tin, has apparently encouraged the expectation that one or more addi-tional polymorphic modifications might exist. The search for confirma-tion of this idea has, as might be anticipated, led to the accumulation of a body of miscellaneous evidence, much of which would probably never have been sought, or taken seriously even by its discoverers, but for previous assumptions. The ball apparently was started rolling in 1880 by Trechmann,' who reported a new modification of tin (y tin), which was brittle and found in "hard head," a highly arsenical, slaggy material produced in a certain stage of tin smelting. A mixture of two kinds of crystals was obtained from a Cornish tin furnace, and those thought to be y tin were studied crystallographically. The results indicated that these crystals were rhombic and of different density from the tetragonal tin prepared electrolytically by Miller.3 Their analysis was given as 98.7 per cent Sn, 1.3 per cent Fe, and traces of As, Sb, Bi and S. In 1881 von Foullon4 obtained similar crystals from a Bohemian tin furnace. Headden5 examined crystals similar to those of Trechmann and von Foullon and reported them to be monoclinic, but of analysis corresponding to stannous sulphide. Later, Stevanovic,6 by goniometric measurements, proved that these crystals of SnS were really rhombic. Groth7 pictures and describes both "rhombic tin" (Fig. 9, vol. 1) and stannous sulphide (Fig. 84, vol. 1); their faces and angles correspond within the accuracy of measurement. Spencer3 in 1921 examined the above evidence critically; he found similar crystals from Cornish tin furnaces, proved them to be SnS, and even was able to analyze some of Trechmann's original specimens, finding high sulphur content. (Apparently Trechmann's analysis had been based on a second lot of crystals, not described crystallographically.)

Jan 1, 1939

By J. F. Bryson

Instantaneous outbursts of coal in underground workings have occurred frequently in various coal fields in Nova Scotia; British Columbia; Canada; South Staffordshire, England; and the states of Washington, Virginia, West Virginia and eastern Kentucky in the United States. Such outbursts in eastern Kentucky have been called "mountain bumps " because they are more likely to occur under mountain cover than elsewhere, but recently they have become generally known as "coal bumps." The eastern Kentucky coal field has been troubled by these outbursts since 1923. Many men have been injured and killed, and the morale of the workmen in the vicinity of such outbursts has been affected to such an extent that mine production has suffered for a considerable period following each outburst. Such phenonlenal occurrence in any coal field naturally has led to discussion as to the cause and means of prevention. In the eastern Kentucky field, local mine officials, workmen, mining engineers, and many others have offered many ideas as to the cause and many methods of prevention have been suggested, and tried without success. Some of the plans were either practically or economically unsound and in general impossible to follow. To enumerate all the suggestions would require a large volume. One cause mentioned was that they might be due to gas under high pressure, as in Lower Silesian mines, and the remedy reeommcnded was to drain the gas by drilling holes into a suspected area. A hole 30 ft. long was drilled into a 60-ft. pillar to allow the gas to drain off, hut the pillar bumped the next day. Realizing the importance of obtaining the best information available on coal bumps, the writer, with the permission of the Harlan County Coal Operators' Assoeiation, invited Mr. George S. Rire, Chief Mining Engineer of the U.S. Bureau of Mines, who had investigated bumps in several countries, to conduct an investigation of coal bumps in this field. Mr. Rice, by permission of the Director of the G.S. Bureau of Mines, accepted the invitation, and it was the writer's privilege, in company with

Jan 1, 1936

By J. F. Bryson

Instantaneous outbursts of coal in underground workings have occurred frequently in various coal fields in Nova Scotia; British Columbia; Canada; South Staffordshire, England; and the states of Washington, Virginia, West Virginia and eastern Kentucky in the United States. Such outbursts in eastern Kentucky have been called "mountain bumps " because they are more likely to occur under mountain cover than elsewhere, but recently they have become generally known as "coal bumps." The eastern Kentucky coal field has been troubled by these outbursts since 1923. Many men have been injured and killed, and the morale of the workmen in the vicinity of such outbursts has been affected to such an extent that mine production has suffered for a considerable period following each outburst. Such phenonlenal occurrence in any coal field naturally has led to discussion as to the cause and means of prevention. In the eastern Kentucky field, local mine officials, workmen, mining engineers, and many others have offered many ideas as to the cause and many methods of prevention have been suggested, and tried without success. Some of the plans were either practically or economically unsound and in general impossible to follow. To enumerate all the suggestions would require a large volume. One cause mentioned was that they might be due to gas under high pressure, as in Lower Silesian mines, and the remedy reeommcnded was to drain the gas by drilling holes into a suspected area. A hole 30 ft. long was drilled into a 60-ft. pillar to allow the gas to drain off, hut the pillar bumped the next day. Realizing the importance of obtaining the best information available on coal bumps, the writer, with the permission of the Harlan County Coal Operators' Assoeiation, invited Mr. George S. Rire, Chief Mining Engineer of the U.S. Bureau of Mines, who had investigated bumps in several countries, to conduct an investigation of coal bumps in this field. Mr. Rice, by permission of the Director of the G.S. Bureau of Mines, accepted the invitation, and it was the writer's privilege, in company with

Jan 1, 1936

By J. P. Dunlop

THE fact is-notable though probably little known that the United States is the only nation obtaining and distributing through its Government bureaus any data pertaining to waste metals and drosses. Some foreign governments do issue reports relating to mine or smelter production of primary metals, but none gives in scope and detail the information published now by the U. S. Bureau of Mines and formerly by the U. S. Geological Survey; and this is despite the fact that the funds annually allotted for those purposes are insignificant in comparison with allotments for the preparation of data relating to other industries of like importance. The earliest data on the production of metals from secondary sources in the United States were contained in a press bulletin issued by the U. S. Geological Survey on Jan. 4, 1909. The information published was that for the year 1907 obtained and compiled by C. E. Siebenthal, who was one of the first to visualize the growing importance of the scrap-metal industry. The National Conservation Commission had emphasized its opinion that the known domestic supply of certain kinds of the more important metals was being rapidly marketed and that while there was no immediate cause for concern it was best to conserve such resources. Not only had there. been a lamentable lack of any data regarding the quantity of scrap metals available or used but also gross carelessness and indifference in the segregation, collection, and effective use of scrap material. Siebenthal realized that even approximately correct statistics of recoveries from the more important base-metal scrap and drosses were nearly as essential to both producers and consumers as the statistics of the output of primary metals. There were not then nor are there now sufficient funds for complete collection of data, nor was it considered the province of the Geological Survey to do more than determine approximately the recovery of secondary metals for use in supplementing those given for the primary metals. Undoubtedly the first bulletins-issued did not give the full output, for it takes time to establish contacts for an inquiry covering so

Jan 1, 1928

By J. P. Dunlop

THE fact is notable though probably little known that the United States is the only nation obtaining and distributing through its Government bureaus any data pertaining to waste metals and drosses. Some foreign governments do issue reports relating to mine or smelter produc-tion of primary metals, but none gives in scope and detail the information published now by the U. S. Bureau of Mines and formerly by the U. S. Geological Survey; and this is despite the fact that the funds annually allotted for those purposes are insignificant in comparison with allotments for the preparation of data relating to other industries of like importance. The earliest data on the production of metals from secondary sources in the United States were-contained in a press bulletin issued by the U. S. Geological Survey on Jan. 4, 1909. The information published was that for the year 1907 obtained and compiled by C. E. Siebenthal, who was one of the first to visualize the growing importance of the scrap-metal industry. The National Conservation Commission had emphasized its opinion that the known domestic supply of certain kinds of the more important metals was being rapidly marketed and that while there was no immediate cause for concern it was best to conserve such resources. Not only had there been a lamentable lack of any data regarding the quantity of scrap metals available or used but also gross carelessness and indifference in the segregation, collection, and effective use of scrap material. Siebenthal realized that even approximately correct statistics of recoveries from the more important base-metal scrap and drosses were nearly as essential to both producers and consumers as the statistics of the output of primary metals. There were not then nor are there now sufficient funds for complete collection of data, nor was it considered the province of the Geological Survey to do more than determine approximately the recovery of secondary metals for use in supplementing those given for the primary metals. Undoubtedly the first bulletins issued did not give the full output, for it takes time to establish contacts for an inquiry covering so

Jan 1, 1928

By J. P. Dunlop

THE fact is notable though probably little known that the United States is the only nation obtaining and distributing through its Government bureaus any data pertaining to waste metals and drosses. Some foreign governments do issue reports relating to mine or smelter production of primary metals, but none gives in scope and detail the information published now by the U. S. Bureau of Mines and formerly by the U. S. Geological Survey; and this is despite the fact that the funds annually allotted for those purposes are insignificant in comparison with allotments for the preparation of data relating to other industries of like importance. The earliest data on the production of metals from secondary sources in the United. States were contained in a press bulletin issued by the U. S. Geological Survey on Jan. 4, 1909. The information published was that for the year 1907 obtained and compiled by C. E. Siebenthal, who was one of the first to visualize the growing importance of the scrap-metal industry. The National Conservation Commission had emphasized its opinion that the known domestic supply of certain kinds of the more important metals was being rapidly marketed and that while there was no immediate cause for concern it was best to conserve such resources. Not only had there been a lamentable lack of any data regarding the quantity of scrap metals available or used but also gross carelessness and indifference in the segregation, collection, and effective use of scrap material. Siebenthal realized that even approximately correct statistics of recoveries from the more important base-metal scrap and drosses were nearly as essential to both producers and consumers as the statistics of the output of primary metals. There were not then nor are there now sufficient funds for complete collection of data, nor was it considered the province of the Geological Survey to do more than determine approximately the recovery of secondary metals for use in supplementing those given for the primary metals. Undoubtedly the first bulletins issued did not give the full output, for it takes time to establish contacts for an inquiry covering so

Jan 1, 1928

George Smith, Sydney, N. S. Wales (communication to the Secretary): The very interesting paper by Mr. Emmons on " The Secondary Enrichment of Ore-Deposits " has just come under my notice; and its reference to my own paper* on " The OreDeposits of the Australian Broken Hill Consols Mine "† is therefore only noted some two and a half years after its publi-

Jan 1, 1903

By J. P. Dunlop

The fact is not.ablc though probably little known that thc Unitcd Statcls is the only nation obtaining and distributing through its Govcrn-ment burcaus any data pertaining to waste metals and drosses. Some foreign goverrlnlents do issuc reports relating to rnine or smelter production of prirrlar~ metals, but none gives in scope and detail t'he information published now by the U. S. Bureau of Mines and formerly by the U. S. Geological Survey; and this is despite the fact that the funds annually allotted for those purposes are insignificant in comparison with allotments for the preparation of data relating to other industries of like importance. The earliest data on the production of metals from secondary sources in the United States were contained in a press bulletin issued by the U. S. Geological Survey on Jan. 4, 1909. The information published was that for thc year 1907 obtained ant1 compiled by C. E. Siebenthal, who was one of the first to visualize the growing importance of the scrap-letal indust,ry. Thc Nationd Conscrvation Commission had emphasized its opinion that the known domestic supply of certain kinds of the morc important irietals was being rapidly marketed and that while there was no immediate cause for concern it was best to conserve such resources. Not only had there been a lanlentable lack of any data regarding the quantity of scrap inetals available or used but also gross carelessness and indifference in the segregation, collection, and effective use of scrap material. Siebenthal realized that even approximately correct statistics of recoveries from the more important base-metal scrap and drosses wcrc nearly as essential t,o both producers and consumers as the stat'istics of the output of primary metals. There were not then nor are there now sufficient funds for complete collection of data, nor was it considered the province of the Geological Survey t'o do more than determine approximately the recovery of secondary metals for use in supplementing those given for the primary metals. Undoubtedly the first bulletins issued did not give the full output, for it takes time to establish contacts for an inquiry covering so

Discussion of the paper of GEORGE S. RICE and H. H. CLARK, presented at the Pittsburgh meeting, October, 1914, and printed in Bulletin No. 94, October, 1914, pp. 2563 to 2571. NORMAN V. BRETH,* Pittsburgh, Pa.-It was my privilege to visit in the last two months on behalf of the U. S. Bureau of Mines 10 mines where electric shot-firing systems controlled from outside the mine are installed. I will describe briefly what I saw in some of these mines, which are located in Utah, New. Mexico, Oklahoma, Alabama, and Kansas. At a mine in Utah, 230-volt alternating current is used to fire the shots, which is taken from a small transformer in the substation. The shot-iring circuit is independent of all other wires and is tested for grounds every day. There are no lightning arresters on the firing circuit. Porcelain insulators are used inside of the mine, and glass outside. The switches are situated as follows: One in the substation, one in, the shot-firer's cabin, two at each cross entry; where the shot-firing circuit crosses the trolley wire a switch is placed on either side of the entry in series with the shot-firing circuit. The miners are checked in and out of the mine. The coal is undercut and is shot down with permissible explosive, the shots being connected in multiple. There are 75 to 110 shots fired each day. A great many times there are no missed shots. If not more than two or three are missed they are left until next day. The fan is kept running at full speed when the shots are fired. The shot-firing switch is closed only once and the whole mine is shot at once. At another mine in Utah, power wires are used for shot-firing circuits; 500-volt, direct current is used to fire the shots. The only sizes of wire used outside of the power wires are Nos. 8 and 14 B. & S. gauge. The return is connected to the pipe lines and track. Porcelain insulators are. used inside of the mine.

Jan 4, 1915

By D. H. Newland

Certain observations from the field and laboratory suggest the need for recasting some of our ideas about gypsum as a rock-forming mineral and in relation to supplies for industrial use. Until about 25 years ago, the use of gypsum was confined almost entirely to agriculture. During the past quarter century, though, its usefulness has been greatly developed, particularly in the building trades, which now absorb most of the gypsum produced. In 1919, according to the U. S. Geological Survey, the output of crude gypsum was 2,240,163 tons, a gain of 912 per cent. in 25 years. About one-half of this production was mined in New York, Ohio, and Michigan, where the proved supplies can hardly be regarded as over-large when viewed in relation to the rapid expansion of industrial requirements. The occurrence of gypsum in the United States is treated by R. W. Stone and others.' The deposits of Canada are described by L. H. Cole. Several states, including Kansas, Oklahoma, Iowa, Michigan,and New York, have made special surveys of their gypsum deposits, but the reports, as a rule, refer to conditions as they existed from 15 to 20 years ago. Association of Gypsum and Anhydrite The two calcium sulfate compounds, gypsum (CaSO4.2H2O) and anhydrite (CaS04), are the more stable forms of a series which includes at least two other members, so-called half-hydrate (CaSO4.1/2H20) and soluble anhydrite (CaS04). Each of the latter readily takes up water to recrystallize as gypsum and consequently is incapable of existence under ordinary geological conditions; also each can be prepared from gypsum by the application of heat within certain temperatures, the process on which is based the manufacture of commercial plasters. If the temperature limitations are not observed, the result of the calcination process will be insoluble anhydrite which, compared with the soluble form, takes up water very slowly so as to be of no practical use, although actually it is soluble and in time is convertible into gypsum like the other forms.

Jan 1, 1922

By J. G. Savins

Certain types of macromolecules added to water and salt solutions flowing in turbulent motion can reduce the pressure gradient. Alternatively, the volumetric capacity of a pipe for these fluids is increased by the presence of these materials. Examples presented show that the drag reduction can become significant. Thus, the presence of 0.28 per cent of a gum derivative in a solution of sodium chloride flowing at 200 gal/min in a 1.89-in. pipe yields a pressure drop which is 0.44 of the single-phase drop measured under the same conditions of turbulent flow; the addition of 0.1 per cent of a vinyl derivative to a I-in. water line yields a throughput capacity which is 1.78 of the single-phase capacity at the same pressure drop. It is further shown that these phenomena are distinctly different from previous observations with other classes of non-Newtonian systems. There a simple lowering of friction factors below the levels predicted from the resistance laws for Newtonian fluids is associated with a suppression of turbulent motion. A rational physical explanation for drag reduction is advanced. Briefly, the proposed mechanism is a storage by the molecular elastic elements of the macromolecules in solution of the kinetic energy of the turbulent motion. INTRODUCTION This study was inspired by a recent review of some paradoxical drag reduction phenomena in turbulent pipe f1ow.I Under very moderate conditions of turbulent flow, the pressure gradient necessary to pump solutions containing certain specific kinds of polymers, fibers and metallic soaps may become appreciably lower than that required* to pump the solvent, i.e., water or a low-viscosity hydrocarbon, under identical flow rates in the same conduit. As shown by our review, this phenomenon of drag reduction in turbulent duct flow was first noted during the second world war, apparently arising in connection with the development of flame warfare weapons. Since that time several papers illustrating this phenomenon have appeared: Toms, Oldroyd,3 Agoston et al., Bundrant and Matthews, Robertson and Mason,6 Ousterhout and Hall,7 Daily and Bugliarello~ Lummus, Anderson, and Fox. 9 That there are practical applications for techniques which increase discharge or decrease the pressure necessary to transport a liquid through a pipeline is illustrated in the patents which have issued which take advantage of this peculiar phenomenon, e.g., Mysels,l0 Dever, Harbour, and Seifert.11 One also finds fragmentary evidence of this effect in the data pertaining to a few of the polymeric solutions studied by Shaver12 and Dodge.13 However, these investigators were concerned with the development of friction factor vs Reynolds number correlations for a variety of non-Newtonian solutions and suspensions, rather than in a study of drag reduction-. A similar kind of drag reduction effect has been observed in gases. Sproull, for example, reports that adding dust to air flowing in turbulent motion through a pipe results in a lowering of the pressure gradient at identical flow rates. There are also military applications for reducing the drag on hydrodynamic vehicles. For example, the possibility of injecting a rheologically complex fluid into the boundary layers of bodies to reduce the skin friction has been investigated by Fabulal5 and Granville.16 Along somewhat different lines are the drag reduction studies of Kramer.17118 He has shown that skin friction can be reduced by covering the surface of a vehicle with a flexible skin. The effect is apparently due to the boundary layer being stabilized by the presence of the skin. Drag reduction by means of coexisting gas and liquid boundary layers, e.g., film boiling and continuous gas injection, has been proposed by Bradfield, Barkdoll, and Byrne,19 Cess and Sparrow,20'21 Sparrow, Jonsson, and Eckert.22 Here the skin friction occurs between a vapor and a surface rather than between a liquid and a surface. There are several references in the literature to friction-factor correlations for non-Newtonian solutions and suspensions: Shaver and Merri11,23 Dodge and Metzner, Clapp,25 and Thomas.26

Jan 1, 1965

Professor Jenney has performed a notable service in presenting this summary of the steadily increasing body of observation on the presence of carbon in rocks of all kinds and its probable influence upon ore-deposition, and in formulating a mode of comparing directly the relative resistance of minerals to oxidation, as well as their reducing-power, and the protective action which minerals having higher reducing-powers exert in preventing the oxidation of associated minerals which possess relatively lower affinities for oxygen. I have had an opportunity of observing a vein which falls within the scope of his interesting discussion. The vein at Ku Shau Tzu, Mongolia, lies directly across a contact of limestone and overlying bituminous shales. Probably it occupies a compression-fissure. The shale has been reduced to such a condition of' non-coherence that much of it can be crushed in the hand, producing a handful of angular fragments resembling beech-nuts in shape and size. In the limestone the metals are principally in argentiferous galena with some pyrite and blende; but the latter two are very subordinate in quantity to the galena. In short, it is an every-day lead-vein in limestone, with siliceous limestone gangue. It is one of those veins in which the ore is not continuous, but consists of a band in the country-rock in which seams of lead sulphide begin at one wall and cross in a bent form, increasing in thickness, to the other wall, where they thin out and end. This may indicate torsional stress, but the shape of the lenses points to some other action. They often ran nearly parallel to the hanging-wall for a considerable distance and crossed the vein on a moderate angle, but turned sharply along the vein on approaching the foot-wall. The intermediate rock contains nodules, bunches and specks of ore, and the lenses vary exceedingly in size, shape and position in the vein.

Jan 1, 1903

By M. E. Wadsworth, P. H. Yu, C. K. Hansen

A study of the rate of dissc5lution of chalcopyrite (CuFeS2) in acidic solutions under oxygen overpressures was carried out by measuring the rate of formation of cupric ions in solution. Effects of temperature, oxygen partial pressure, surface area, and concentration of sulfuric acid were evaluated. A sized batch of chalcopyrite was leached in the temperature range of 125° to 175°C and in the pressure range of 75 to 400 psi of oxygen. In 0.5 N H2SO4 all products of reaction went into solution except for trace amounts of elemental sulfur. The dissolution of chalcopyrite followed linear kinetics and was essentially independent of hydrogen ion concentration for H2S04 concentrations between 0.2 and 0.5 N. The oxygen dependence indicated adsorption approaching limiting values with increasing oxygen pressure. The linear mechanism was explained in terms of steady-state adsorption of oxygen at the chalcopyrite surface followed by a surface reaction. The enthalpy of activation for adsorption of oxygen was found to be approximately 33 kcal per mole. An activation enthalpy of approximately 9 kcal per mole was observed for the surface reaction. Charge transfer reactions are not rate controlling in the process.

Jan 1, 1973

By Donald W. Mitchell, John Nagy, Edwin M. Murphy

In 1957 research was initiated in the U.S. Bureau of Mines experimental coal mine near Pittsburgh, Pa., to study factors affecting foam generation and transport, to evaluate the effectiveness of high-expansion foam for controlling mine fires, and to develop techniques for applying the method under U.S. mining conditions. These investigations showed that high-expansion foam containing at least 0.2 oz of water per cu ft of foam is effective in controlling experimental underground fires burning coal, wood, and oil. Sometimes the fire was completely extinguished, but more often, it was brought under sufficient control to permit either a direct attack on the fire with a stream of water or loading of the hot material into cars. A progress report prepared in July 1958 summarized the initial achievements of the USBM experiments. Since then other phases of the foam-plug method for attacking fires have been studied in the laboratory and in the mine. Previous studies by British engineers of the foam-plug method for fighting mine fires indicated that high-expansion foam was effective in controlling experimental timber fires in an underground passageway. Their subsequent work pertained to the practical aspects of fighting large fires within a mining area with a foam-plug.

Jan 9, 1960

By R. F. Mehl, C. E. Birchenall

SINCE Maxwell1 first considered the self-diffusion process in 1872 its importance in the kinetic theory of matter has been recognized. Until the discovery of isotopes in 1913, a direct measurement of this quantity seemed impossible. The only information that could be gathered indirectly was for gaseous systems for which the kinetic theory was well developed. When methods of direct observation be-came available, investigations on self-diffusion were carried out in condensed phases. In metals these data are presumably of potential importance in the study of recovery, recrystallization, creep, sintering, and related phenomena. Following the pioneer work of Von Hevesy2 and his collaborators, who determined the rate of self-diffusion in lead with the naturally occurring thorium B isotope, several metals have been investigated. Pb, Ag³, Au.6,5, and Cu6,7,8,9 are examples of isotropic crystals existing in only one phase modification. Anisotropy of diffusion has been demonstrated in Bil6 and Znll. This paper is a study of a single metal in two allotropic forms and also of self-diffusion in a body-centered cubic lattice. Despite the fact that the measurements in each of the papers cited on self-diffusion in copper seem to be internally consistent to about 10 to 15 pet, the curves reported by different authors differ by factors of 2 to 4 at the same temperatures. This uncertainty may account, in part, for the failure to establish a successful correlation between the self-diffusion rates and other physical characteristics of the metals. No satisfactory theory of metallic self- diffusion has as yet been proposed to account for all the existing data and to permit estimation in other metals. Experimental Part: Two units of radioactive iron were used in these experiments, each a mixture of Fe53 and Fe59 (12). Fe53 decays by K electron capture and the emission of an X ray with a half life of about 4 years. Fe59 emits two beta spectra, one with a maximum energy of 0.26 Mev, the other 0.46 Mev, and gamma rays of 1.1 and 1.3 Mev, with a half life of about 44 days. They were present in nearly equal concentration initially. The composite half life started at about 50 days and increased as the Fe59 decayed, leaving Fe55 relatively more abundant. After aging a year, the half life was too long to measure significant decay in a month. The absorption properties also changed with time. Because of the importance of the absorption coefficient in the diffusion calculations, it was necessary to determine this quantity frequently over the period during which these experiments were carried out. This correction was unsuspected at the time of publication of notesl3 on this work and accounts for the discrepancy in alpha iron and for part of the discrepancy in gamma iron.* * The data in the present paper supersede those given in the notes entirely. In one note the scale of log D was inadvertently reversed. In addition to the correction for the drift in absorption coefficient, the D values for gamma iron at low temperatures were high owing to insuficient correction for diffusion occurring during heating and cooling through the high temperature part of the alpha range at a rate much slower than that employed in the runs reported here. The high temperature alpha rates are much higher than the low temperature gamma rates and correspond to large equivalent times at these temperatures. These experiments were discarded and new measurements taken. Independent experiments with the same activity units indicated a radioactive contaminant in the iron, but exhaustive attempts to isolate and identify it chemically failed. These experiments? indicate † These experiments will be discussed in a later publication from this laboratory. that the contaminant represented only a trace of little importance in the diffusion results. The active iron was plated from an iron chloride solution. Enough of the solution was dropped on a 1% in. square of filter paper to wet it thoroughly.

Jan 1, 1951

CARACAS PETROLEUM Established February 24, 1957 Official year begins in January Harry J Sykes, Chairman G J Clarke, Vice-Chairman Robert S Longwell, Vice-Chairman David L Stepanek, Treasurer Robert C Newman, Secretary Texas Petroleum Co Apartado 267 Caracas, Venezuela

Jan 1, 1960