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I HAVE striven to demonstrate to you as well as possible the method of bringing the metals of your ores to their ultimate perfection. But one cannot always do with gold that is found in the ores what is done with the other metals, for gold is not always accompanied by fine silver nor is it

Jan 1, 1942

By I. R. Kramer

I. R. Kramer (Martin Co.)—In a recent paper Nakada and Chalmers24 reported some observations of effects of surface conditions on the stress-strain curves of aluminum and gold single crystals. It is of interest to compare these observations with the results published previously in this journal and to comment on their general conclusions. In brief, Nakada and Chalmers concluded that the removal of the surface layer of a prestrained specimen lowered the stress-strain curve for aluminum but not that for gold. Further, they concluded that the surface work hardening of aluminum is confined to a depth not more than l0-3 cm. In our results25 published previously, it was pointed out that when prestrained specimens of aluminum and gold were polished to reduce the thickness upon reloading the initial flow stress decreased markedly. Further if a sufficient amount of metal was removed, the yield point failed to appear. With continued application of the load the stress-strain curve became coincident with that of the virgin crystal. We have found this behavior in some 100 determinations to hold consistently for gold, aluminum, and copper in both single and poly-crystalline specimens. The amount of strain required before the curves coincided depends upon the amount of metal removed but it is usually less than 0.01. This type of behavior is the same as that reported for metarecovery by other investigators.29 For aluminum specimens which have been prestrained and then heated to temperatures above 50°C we have consistently found that the stress-strain curve was typical of the orthorecovery28 type. In this case the stress-strain curve always lies below that of the virgin specimen. With respect to Ref. 24 the curves for aluminum are always below that of the virgin curves, while those for gold become coincident. This observation indicates at least for aluminum that the specimens must have been heated to a temperature high enough to cause recovery by an alteration of the internal dislocations. In addition, a recovery would be expected because of the removal of the surface work-hardened layer. Nakada27 had reported that, with his particular apparatus in which a perchloric acid polishing solution was used, the temperature of the specimen increased 65°C. The curves presented in Ref. 24 for gold do not permit one to detect the initial flow stress upon reloading after the surface-removal treatment. In fact, contrary to the method used by Nakada and Chalmers, the change in the stress-strain curve produced by a surface-removal treatment cannot be described in terms of a decrease in stress at strains much higher than that at the initial flow stress because of the coincidence of the curves at the higher strain values. With regard to the depth of the work-hardened surface layer, our data show for aluminum single crystals (7.5 by 0.3 by 0.3 cm) that the initial flow stress remained constant after 12 x 10-3 cm had been removed from the thickness. This depth was independent of the prior strain. For gold crystals this depth is somewhere between 10 x 10-3 and 20 x 10-3 cm. Y. Nakada (author's reply)— Kramer states,28 "for aluminum specimens which have been prestrained and then heated to temperatures above 50°C, we have consistently found that the stress-strain curve was typical of the orthorecovery28 type. In this case the stress-strain curve always lies below that of the virgin specimen." However, Cherian et a1.26 discovered that aluminum polycrystals annealed at 32" and 100°C showed the metarecovery behavior. They showed that the orthorecovery behavior did not appear until the crystals were annealed at 150°C. Kramer suggests28 that the drop in the flow stress of aluminum crystals after the surface removal by electropolishing24 may be due to the recovery caused by the temperature rise which may occur during the electropolishing.27 However, as indirectly stated in Ref. 24, the current density used in these electro -polishing experiments was 0.15 amp per sq cm. According to ref. 27, this current density should cause a temperature rise of only 40°C. This may cause the metarecovery but not the orthorecovery. Furthermore, as stated explicitly in Ref. 24, the surface removal was accomplished by chemical etching as well as by electropolishing. The results were the same for both electropolishing and etching. During the etching, the specimen temperature did not rise above 35°C. Some aluminum crystals were placed in water at 35° C for 30 min. These crystals did not show the decrease in flow stress. Therefore, it is quite clear that the flow-stress drop after the surface removal is not caused by a high-temperature recovery. However, as Kramer points out,28 it is quite possible that the internal dislocation structure may have been altered because of the removal of the highly work-hardened surface layer. However, how much this rearrangement contributes toward the flow-stress decrease is not known at present.

Jan 1, 1965

MANY kinds of marcasite* are found since every metallic mineral, and perhaps some of the semiminerals, produces its own. I believe that [28v] rnarcasites are nothing other than the secondary materials and the menses of the conception of metals which, through insufficient time, have yet to arrive at their perfect age; and thus, because of

Jan 1, 1942

By H. N. Eavenson

EaRly in 1917, the United States Coal & Coke Co. secured options on several tracts in Harlan County, Ky., aggregating about 19,000 acres in area, and after careful prospecting by outcrop openings and diamond drilling, completed the purchase late in July of that year. This property is situated in the eastern end of Harlan County, south of the Poor Fork of Cumberland River, and extending across Big Black Mountain to the Clover Fork of Cumberland River, a distance of about 7 mi. (11.3 kg.). It extends from the Kentucky-Virginia line westward for about 6 mi. Looney Creek, which empties into Poor Fork, crosses the property for about 4 mi. (6.4 kg.), and as several of the seams within the property outcrop along this stream, it afforded an easy, and the logical, place for development. The property is on the northern side of the geological trough formed by the uplifting of Stone Mountain, on the southern, and Pine Mountain, on the northern side; the northern boundary along Poor Fork is practically at the base of Pine Mountain. This area has been described in various geological reports. The main seam on this property is the one known variously as the "C," Benham, Keokee, Taggart, and Roda; it is also called, by the Kentucky Geological Survey, the Kellioka seam of the western portion of Harlan County. This seam averages, in this property, about 5 ft. (1.5 m.) in thickness, although local rolls reduce this thickness considerably over small areas, and at the extreme western end of the property the seam splits. It is usually clean, although occasionally a small parting occurs within a few inches of the bottom of the seam; it is one of the best coking and gas coals in the United States. The average analysis of this coal is given in Table 1.

Jan 1, 1922

By R. M. Waterstrat, E. C. van Reuth

BINARY- alloy phases having the A15-type crystal structure have been described as occurring at a simple and more or less invariant stoichiometric composition (A3B) which corresponds to the relative number of atoms occupying each of the two crystallographi lattice sites in this structure.1,2 It is frequently assumed, therefore, that each crystallographic site is occupied exclusively by one kind of atom. In most cases, however, there have been insufficient experimental data to establish whether atomic ordering is, in fact, complete. Recent studies have shown that binary A15-type phases are sometimes stable over an appreciable composition range3''* and, occasionally, the composition range of stability does not even include the "ideal" A3B stoichiometric composition.5-7 We have observed the existence of nonstoichiometric A15-type phases in the binary systems Cr-Pt and Cr-Os. This has not been reported in previous work on these alloy systems.1,8-11 A series of alloys, each weighing approximately 30 g, was prepared by are-melting in an Ar-He atmosphere using 99.999 pct Cr, 99.999 pct Os, and 99.99 pct Pt as starting materials. Each alloy was melted four times with a total weight loss of less than 1 pct. The stoichiometric (A3B) alloys were sealed in evacuated quartz tubes and annealed at 1200°C for periods of time ranging from 3 days to 2 months. Examination of the alloy microstructures revealed that little change had occurred over this time interval and it was therefore assumed that the microstructures were fairly representative of equilibrium conditions. No evidence of contamination was observed although there was apparently some loss of chromium which was confined to a thin layer at the surface of the specimens. The quartz tubes were quenched from the annealing temperature into cold water. X-ray diffraction and metallographic examination of the stoichiometric alloys revealed an estimated 10 to 30 pct of second phases which were tentatively identified as phases previously reported in these binary-alloy systems.8-11 A second series of alloys was prepared by mixing -325 mesh metal powders having a nominal purity of 99.9 pct and compressing these mixed powders in a cylindrical die at a pressure of 43,000 psi. These alloys, each weighing 15 g, and some of the arc-melted alloys were annealed in a high-temperature vacuum furnace heated by tantalum strips at a pressure of 10-8 Torr and were rapidly cooled by turning off the furnace power. X-ray and metallographic examination of both series of alloys served to establish the composition ranges of the A15-type phases. Although some chromium losses occurred during the vacuum annealing, they were largely confined to a thin layer on the outer surfaces of the samples. It was established that the A15 phases occur in the Cr-Pt system at 21 ± 1 at. pct Pt after 1 week at 1200°C and in the Cr-Os system at 28 ± 1 at. pctOs after 1 day at 1400°C (see Table I). We also observed that an arc-melted stoichiometric (A3B) alloy in the Cr-Ir system was single-phase (A15-type) in the "as-cast" condition in agreement with previous work.8,13 In addition we obtained a sample of the Cr-Os A15-type phase from Argonne National Laboratory. This alloy contained less than 1 pct second phase12 and was submitted to a density measurement. The density measurement yielded a value of 11.14 g per cu cm in comparison to a theoretical value of 11.25 g per cu cm calculated using the observed lattice constant (4.6806Å) of this alloy. The uncertainty in measurement was 0.1 pct but the sample may have contained some cracks or minor imperfections which could account for the low experimental value. We have also studied the atomic ordering in these phases by means of integrated line intensity measurements using thick, flat, rotating powder samples and CuK a radiation in an X-ray diffractometer. We have obtained order parameters of 0.90 for the Cr-Pt phase, 0.89 for the Cr-Ir phase, and 0.64 for the Cr-Os phase using the formula: where s is the usual Bragg and Williams order parameter, ra is the fraction of chromium atoms in A sites, and FA is the fraction of chromium atoms in the alloy. The values obtained are estimated to be accurate within ±4 pct. If the unusually small value for the order parameter of the Cr-Os A15 phase were due to the existence of lattice vacancies on the "B-atom" sites, then a density of 10.04 g per cu cm would be expected in contrast to the observed value of 11.14 g per cu cm. We, therefore. conclude that the fraction of lattice vacan-

Jan 1, 1967

By Charles M. Rolker

I desire to put on record this memorandum and accompanying sketch of a vein examined by me, in Honduras, Central America, which exhibits a well-marked banded structure. The illustration is of natural size: The vein traverses trachytic porphyry. It is from three to four inches wide. The central band, a, is of white quartz, one inch wide

Jan 1, 1886

By C. M. Wayman, R. Bullough

The selection rules fir twinning in fcc, bcc, and hcp lattices as established in Part I are used to predict the positions, relative to the matrix (untwinned) reciprocal lattice, of reflections due to double diffraction from the twins. These doubly diffracted reciprocal lattice points, which often coincide with ordinary matrix reciprocal lattice points, are deduced from kinematical considerations. 1. INTRODUCTION. A Bragg diffracted beam under certain conditions may be rediffracted to produce a third beam i .e., the incident beam, the first diffracted beam, and the rediffracted beam). In such a case an initial incident beam is diffracted by a set of planes; the diffracted beam may then be rediffracted by a second set of crystallographically different planes. The initially diffracted beam acts as an incident beam for the second set of planes, thus resulting in a twice-diffracted beam. This twice-diffracted beam may be regarded as a singly diffracted beam from a set of lattice planes whose structure factor is zero. In order to find the reciprocal lattice point corresponding to the doubly diffracted beam, it is customary1,2 to combine vectorially the component reciprocal lattice vectors which head to the extra reflections. For example, hcp metals may exhibit the forbidden (0001) reflections.* As Fig. 1 shows, the (0001) reciprocal lattice point results from: (1010) + (1011) = (0001) Similarly, combination of the beams (1011) and (1010) gives rise to: (1011)- (1010) = (0001) As Pashley and stowell2 have pointed out, even if in fact the double diffraction points lie on the Ewald sphere, they may not actually represent observed doubly diffracted beams because the initially diffracted primary beam, i.e., the source, must also correspond to a reciprocal lattice point which lies on the sphere of reflection; however, the reciprocal lattice point corresponding to the planes causing the rediffraction need not lie on the sphere. A little consideration of the Ewald construction in Fig. 2 makes this argument clear. In Fig. 2 the incident beam is represented by the wave vector ko. This beam is initially diffracted by the lattice planes (hkl) which are represented by the reciprocal lattice vector r(hk1) The reciprocal lattice point (hkl) of course lies on the Ewald sphere in order that the Bragg condition be satisfied. The initially diffracted beam is represented by the wave vector kl. If now kl is rediffracted by a second set of planes (h'k'l') resulting in k2 the lattice point (h"k"l") must lie on the Ewald sphere if the double diffracted beam k2 is to be observed. It is clear that (h"k"l") is the vector sum of (hkl) and (h'k'l'), and that (h'k'l') need not in fact lie on the Ewald sphere. In the usual1,2 analysis the origin (000) of the reciprocal lattice is shifted to the point (hkl). However the translation (000)— (hkl) automatically shifts the point (h'k'l') to the Ewald sphere, i.e., (h'k'l')— (h"k"1"). It is to be seen that (hkl), the source reflection, must lie on the Ewald sphere; if it does not the translation (000) — (hkl) places the "new" origin off the sphere, not satisfying the Ewald construction and hence the Bragg condition. The point (h"k"1") of course must lie on the sphere if it corresponds to an observed doubly diffracted beam. It is to be noted that crystals having the hcp structure, as just discussed, are intrinsically capable (i.e., without lattice defects such as twins) of double diffraction, as contrasted to fcc and bcc crystals which are extrinsically capable (requiring lattice defects or reoriented lattice regions). The "allowed" bcc reciprocal lattice points (which comprise an fcc lattice) are (110), (2001, (211), (220), (310), (2221, (321), (4001, and so forth. The combination

Jan 1, 1967

By Ralph W. Bailey, William B. Price

ARSENIC, antimony and phosphorus are now used in the brass industry as standard inhibitors in preventing dezincification in [ ] condenser tubes. This subject has been thoroughly covered by Barry,1 who described the testing procedure by total immersion of suitable specimens in a I per cent cupric chloride solution at definite temperatures. Effects of dezincification were then determined by loss in tensile strength and elongation of the test specimens after definite periods of immersion. In the crystallography of the chemical elements as tabulated by William Hume-Rothery,2 phosphorus (metallic), arsenic, antimony and bismuth are placed in group V-B and the type of crystal lattice for arsenic, antimony and bismuth is given as rhombohedral. The Metals Handbook3 [ ] lists them as "rhombohedral hexagonal," with the additional notation that for arsenic this is the ordinary form at 20°C.; other modifications known or probable at other temperatures. In view of these statements and of the fact that phosphorus, arsenic and antimony are effective in increasing the resistance to dezincification, it was natural to assume that bismuth would act in the same manner. A series of tests was therefore carried out employing the methods described by Barry. Much to our surprise, bismuth did not inhibit dezincification, but rather seemed to accelerate it. Tensile-test speci-

Jan 1, 1942

By Darwin Soler

This chapter will outline the operating procedures at Freeport Kaolin Co.5 kaolin mining operations in Georgia, with emphasis on explaining new techniques recently introduced to reclaim mined-out areas for reforestation. Kaolin is found in the central Georgia area (See Fig. 1) in lenticular, sedimentary deposits of high purity. The beds are Cretaceous in age and vary from 4 to 60 ft in thickness, under a cover of sedimentary overburden ranging from 5 to 150 ft. The kaolin beds contain the mineral kaolinite (a hydrous aluminum silicate) and have a particle-size distribution ranging from about 20µ to the submicron level and averaging about 60% below 2µ. The only contaminants in the deposits are coarse mica, quartz particles, and minor amounts of iron and titanium oxides. These kaolin deposits vary widely in quality from deposit to deposit and also vary within individual deposits. Some of the controlling quality specifications which are determined during exploration are viscosity in water suspension, optical brightness index as measured by reflectance, amenability to bleaching, and particle-size distribution. For this reason, only a small portion of the total kaolin reserves in the Georgia belt are suitable for wet processing for the present markets being served. Kaolin clays are selectively mined by different mechanical methods and are beneficiated by both wet and dry processing to produce a number of products used as fillers and coatings in the paper industry; fillers or additives in the paint, plastic, and rubber industries; and as basic raw materials for the ceramic industry. The State of Georgia is the largest kaolin producer in the United States, with 3,206,454 tons produced in 1966, according to U.S. Bureau of Mines statistics. Freeport Kaolin Co’s processing plant is located in Gordon, Ga., about 20 miles east of Macon, Ga.

Jan 1, 1969

By Ralph W. Bailey, William B. Price

INTRODUCTION ARSENIC, antimony and phosphorus are now used in the brass industry as standard inhibitors in preventing dezincification in [ ] condenser tubes. This subject has been thoroughly covered by Barry,1 who described the testing procedure by total immersion of suitable specimens in a I per cent cupric chloride solution at definite temperatures. Effects of dezincification were then determined by loss in tensile strength and elongation of the test specimens after definite periods of immersion. In the crystallography of the chemical elements as tabulated by William Hume Rothery,2 phosphorus (metallic), arsenic, antimony and bismuth are placed in group V-B and the type of crystal lattice for arsenic, antimony and bismuth is given as rhombohedral. The Metals Handbook3 [ ] lists them as "rhombohedral hexagonal," with the additional notation that for arsenic this is the ordinary form at 20°C.; other modifications known or probable at other temperatures. In view of these statements and of the fact that phosphorus, arsenic and antimony are effective in increasing the resistance to dezincification, it was natural to assume that bismuth would act in the same manner. A series of tests was therefore carried out employing the methods described by Barry. Much to our surprise, bismuth did not inhibit dezincification, but rather seemed to accelerate it. Tensile-test speci-

Jan 1, 1942

By Shigeki Nishimura

INTRODUCTION In this gapes, the author will describes to development of Yubari New coal mine. The construction set about since October 1970, and commenced from June 1975 in winning. Especially, descrives to compare with the studies at planning stage, and the experiences at under construction. The problems for development are next four: 1) There were no outcrop of the coal bearing strata, but the development was instituted against the deep coal seam occurrence at 800 m below the surface. 2) In order to the coal seams occured the deep level from the surface, threr had very difficult problems, i.e. temperature, earth pressure, methane etc. The countermeasure to solved them, were foundation of the development. 3) The construction was afflict with the inundation in high pressure, due to cement grouting and excavating alternately, overcame the difficulties. 4) The construction was finished by the encourage of national investment, in spite of the enterprise was weaken constitution from the energy revolution since 1960's. OUT LINE OF YUBARI NEW COAL MINE Geography Situation. Ishikari coal field is situated the west side of the Hidaka mountains, where runs north to south at center of Hokkaido, northern district of Japan. It's width is 40km in east and west, and length is 110km in north and south.

Jan 1, 1976

By William B Price, Ralph W. Bailey

Arsenic, antimony and phosphorus are now used in the brass industry as standard inhibitors in preventing dezincification in condenser tubes. This subject has been thoroughly covered by Barry,l who de- scribed the testing procedure by total immersion of suitable specimens in a I per cent cupric chloride solution at definite temperatures. Effects of dezincification were then determined by loss in tensile strength and elongation of the test specimens after definite periods of immersion. In the crystallography of the chemical elements as tabulated by William Hume-Rothery,2 phosphorus (metallic), arsenic, antimony and bismuth are placed in group V-B and the type of crystal lattice for arsenic, antimony and bismuth is given as rhombohedral. The Metals Handbook3 lists them as 'rhobomhedral hexagonal," with the additional notation that for arsenic this is the ordinary form at 20°C.; other modifications known or probable at other temperatures. In view of these statements and of the fact that phosphorus, arsenic and antimony are effective in increasing the resistance to dezincification, it was natural to assume that bismuth would act in the same manner. A series of tests was therefore carried out employing the methods described by Barry. Much to our surprise, bismuth did not inhibit dezincification, but rather seemed to accelerate it. Tensile-test speci-

Jan 1, 1942

By Ralph W. Bailey, William B. Price

Arsenic, antimony and phosphorus are now used in the brass industry as standard inhibitors in preventing dezincification in condenser tubes. This subject has been thoroughly covered by Barry,l who de- scribed the testing procedure by total immersion of suitable specimens in a I per cent cupric chloride solution at definite temperatures. Effects of dezincification were then determined by loss in tensile strength and elongation of the test specimens after definite periods of immersion. In the crystallography of the chemical elements as tabulated by William Hume-Rothery,2 phosphorus (metallic), arsenic, antimony and bismuth are placed in group V-B and the type of crystal lattice for arsenic, antimony and bismuth is given as rhombohedral. The Metals Handbook3 lists them as 'rhobomhedral hexagonal," with the additional notation that for arsenic this is the ordinary form at 20°C.; other modifications known or probable at other temperatures. In view of these statements and of the fact that phosphorus, arsenic and antimony are effective in increasing the resistance to dezincification, it was natural to assume that bismuth would act in the same manner. A series of tests was therefore carried out employing the methods described by Barry. Much to our surprise, bismuth did not inhibit dezincification, but rather seemed to accelerate it. Tensile-test speci-

Jan 1, 1942

Discussion of the paper of HOWARD N. EAVENSON, presented at the Pittsburgh meeting, October, 1914, and printed in Bulletin No. 94, October,' 1914, pp. 2637 to 2660. GEORGE S. RICE, Pittsburgh, Pa.-I think it is very wise to point out the greater liability to explosions in certain parts of the year, if there be such difference, with the caution, however, that vigilance be not relaxed at other times. In comparing the figures for the United States with those of Europe, I think we should separate them as far as possible according to cause of origin and means of propagation. That is to say, it would appear to me that the majority of our explosions are due more directly to the ignition of coal dust directly from the flame of explosives, whereas, judging from my inquiries and observations in some of the mines of Europe, the majority of their explosions have been caused by the ignition of fire damp. Now, in the case of fire damp, I do not think that anybody has yet attempted or has been able to find any connection between the seasons and the issuance of methane into mines. One thing must be borne in mind, that if you get a strong explosion of fire damp, dust of a character that might not ignite readily by itself might assist in the extension of an explosion of fire damp through a considerable area in the mine, if not throughout the mine. While it is true we have many lesser explosions in this country attributable to fire damp, it would appear that the majority of all the mine explosions of the country, in considering the means of propagation beyond the locality of the origin, are due to coal dust; and it is the liability to coal-dust explosions that appears to be affected by seasonal changes. Hence the desirability of separating statistically (if it could be done by the inspectors) fire-damp explosions from coal-dust explosions, in order to obtain the true value of the seasonal effect. Nevertheless, in spite of the inclusion of fire-damp explosions with coal-dust explosions, the preponderance of the evidence, as indicated in Mr. Eavenson's figures for American mines, has shown that' in this country there were more explosions in the winter and spring months, when the mines are drier; that is, when the mines are apt to be drier. Whereas, according to the European figures that he has gathered, it seems to be very clearly demonstrated that in France, England, and Belgium, the time when explosions occur has no connection with any particular season. That, I think, is partly due to the point just mentioned, that a majority of their explosions have originated from fire damp. The European mining men have been more careful, generally speaking, with the use of explosives than we have, so that the cause of ignition from that source has been less. Only comparatively few of the mines in foreign

Jan 4, 1915

By A. C. Halferdahl

DURING a study of reactions involving iron sulfides, it became desirable to know approxi-mately the heat of decomposition of pyrite. The values given for the heats of formation of pyrite and ferrous sulfide are 35,500 calories and 23,070 calories respectively. For the reaction 2FeS2= 2FeS+S:, the heat effect would be-24,860 calories. But pyrite gives sulfur and pyrrhotite upon heating and the latter is a solid solution of sulfur in ferrous sulfide. The only meas-urements of this decomposition are those of Allen and Lombard1 of the Geophysical Laboratory who have measured dissociation pressures of both covellite and pyrite and have carefully reviewed the literature. They give a table of values for covellite as determined by Preuner and Brockmoller2 and by Wasjuchnowa3 and compare these values with their own measurements. The conclusion is that the measurements of Preuner and Brockmoller are seriously in error, while Was-juchnowa's values fit in well with those of Allen and Lombard. Wasjuchnowa's measurements were made by a dynamic method, while Allen and Lombard em-plowed a static method on both covellite and pyrite. Tables I and II reproduce the measurements of Wasjuchnowa and of Lombard and Allen on covellite and pyrite.

Jan 11, 1927

By Robert F. Shurtz, William J. Verner

Three basic questions must be answered by an engineer performing an economic analysis of a mineral property: (1) How much can the company afford to pay for the property; (2) At what rate should the property be mined; (3) What will be the return on the investment. These questions often defy reasonable analysis, because at the point in time at which they must be answered little may be known about the grade of ore and the reserve tonnage. The purpose of this report is twofold. First, to derive a method of determining purchase price, rate of production and return on investment which is valid under varying conditions of ore grade and tonnage reserve; and, second, to apply this method to the Margay deposit in an attempt to evaluate it as a business enterprise. This is an actual economic analysis of an existing nickel-copper deposit fictitiously named the Margay. It was carried out for a mining corporation and proved to be the determining factor in the subsequent purchase and development of the property. All data referring to costs, quality and quantity of ore, etc., are accurate and truly represented. Prices used are obsolete but the method is not dependent on those variables. Basic assumptions for the analysis are given in Table I, page 71.

Jan 11, 1966

By M. A. Roche

AST fall over half a million tons of ore and rock were broken in one blast at the open pit of the Hudson Bay Mining & Smelting Company's operation, at Flin Flon, Manitoba. The following particulars of the blast, and details of the preparatory work, indicate how an operation of this scope is carried out. The data given, in essentially the present form, were first published by The Canadian Mining Journal. The area blasted was 150 ft. wide and about 700 ft. long. A total of 123 tons of 50 per cent forcite gelatin, in 5 by 16-in. cartridges, was used for the charge. Drilling for the blast was started on May 29, and was completed late in August, requiring 1297 machine shifts for drilling only. Total footage drilled for the shot was over 5 miles of 6-in. hole. The main blast consisted of 232 holes spaced on 17.5-ft.

Jan 1, 1934

By David Turnbull

In most reactions involving solids the transformation kinetics may be represented by the combination of two processes —those of nucleation and of growth. For example, Mehl and his coiq-orker in their studies on the transformation of austenite to pearlite in steels have been able to describe the kinetics in terms of the rates of nucleation and of growth. By micrographic examination of their specimens they determined the nucleation rate (rate of appearance of pearlite colonies) as a function of time, of percent transformation, and of temperature. They observed that after an incubation period in which no nuclei are observed, the number of nuclei appearing per unit time per unit of untransformed grain boundary area, increases at an increasng rate with time. When recrystallization rates have been interpreted in terms of rates of nucleation and growth and the rate of nucleation determined, an incubation period followed by an increasing rate of nucleation has also been reported. Among the studies in which this phenomenon has been observed are those of Kornfeld and coworkers3 on cold-drawn aluminum wire, of Anderson and Mehl4 n the recrystallization of aluminum sheet, and of Stanlcy and Meh15 on the recrystallization of silicon ferrite sheet. The existence of an incubation period during which no nuclei are observed does not appear to have been reconciled with the generally accepted Volmer-Becker theory of nucleation in condensed systems. This theory ostensibly requires the rate of appearance of nuclei to be independent of time. Volmer-Becker Theory In order to form a stable nuclcus of a new phase B in a mother phase A, the molecules or atoms of the mother phase must surmount a free energy barrier whose height is determined by the volume free energy change accompanying the transformation and the energy of the surface separating the two phases. The free energy difference between nuclei of various sizes and the molecules or atoms of the mother phase is plotted schematically in Fig I as a function of the radius of the nucleus r. This free energy difference is plotted for two values of the change of free energy per atom, (Jb — ja) accompanying the transformation when the volumes of the two phases are infinite. One of these values of (Jb—Ja) corresponds to a temperature above the temperature To at which the phascs A and B are in equilibrium, and the other to a temperature below To. In order for a nucleus of phase B to be stable at a temperature T² < TO, its radius must be equal to or greater than the critical value r* for which the free energy of formatioil of the nucleus is a maximum, the of phase B having radii equal to or less than r* will be called embryos hfehl and Jetter," in discussing the kinetics of nucleation in solid systems, suppose that embryos of critical size are formed

Jan 1, 1949

By A. Gittens

In two recent papers stevens13,14 has compared the methods used by various investigators to calculate the contribution of grain boundary sliding to the total creep strain. In previous work Gittins15 has shown that the strain due to grain boundary sliding Egb may be estimated from the lateral, d, and vertical, v, displacements of a longitudinal marker line as it crosses a grain boundary. He obtained the formula, where nL is the number of grains per unit length measured on the specimens before creep, and \p and ?2 are, respectively, the angle between the grain boundary and the stress axis in the plane of the surface and normal to the surface (see Ref. 13, Fig. 1). The subscript L indicates that observations are made in a longitudinal direction parallel to the stress axis. It was generally found more convenient to measure the grain size of a specimen before creep; this was necessary to characterize the specimen. Stevens13,14 however prefers to define Egb in terms of NL, the number of grains per unit length after creep. Since nL - NL(l + €1) where cr is the total strain, Eq. 1 11 becomes The quantities d and ?, can be determined directly from the marker lines, while v and ?2 are found by sectioning normal to the surface. In the interior when symmetry considerations suggest that v = d and ?1 - ?2 the strain due to grain boundary sliding may be estimated from a suitable internal longitudinal marker line by the equation To determine cgb at the surface using either Eqs. |1| or [2] requires a large number of observations, particularly if many estimates of cgb are required, and also it is impossible to determine the variation of cgh with creep strain on the same specimen because the specimen must be sectioned to determine ?2. Gittins15 found that for a number of materials the sliding vectors d and v were related to each other so that provided one was measured the other could be estimated. Also during creep, grain boundaries tend to migrate to meet the surface at angles close to 90 deg,16 so that the term nL(v/tan?2)L was comparatively small when 4,- 90 deg. By determining the frequency distributions of ?2 on control specimens this term can be estimated without sectioning the creep specimen. In this way an empirical equation based on Eqs. |1| and |2| enables cgb to be determined with reasonable accuracy with fewer observations of the angles and sliding components. For B brass, the relationship between the sliding vectors indicated that ceb = 0.85nLVL . In Table I of Stevens paper this equation is stated to be incorrectly derived. However it should be pointed out that this is an empirical equation derived from Eq. |1|, based on a knowledge of the relationship between d and v and on the frequency distributions of ?1 and ?2 for a particular material under given experimental conditions. It was used only when these relationships were known, to reduce the number of observations required to estimate cb. Therefore the comment "derivation incorrect does not apply. Gittins did in fact make use of Eqs. |1| and 131. Author&apos;s Reply I must apologize to Dr. Gittins for the inadvertent misrepresentation of his work. Other slight errors in Table I have been pointed out to me. Langdon (No. 12 Table I), Gifkins (No. 7, Table I), and possibly other workers did not measure the number of boundaries per unit length after creep (A&apos;) but the corresponding quantity bejove creep (n). As Dr. Gittins points out, a completely analogous set of equations to those given in the paper can be derived by the same method: using the number of boundaries per unit length before instead of after creep. The basic equations corresponding to Eqs. [2] and 171 of the paper, from which all the others can be derived, are

Jan 1, 1968

By W. S. CAYPLESS, H. O. Hofman, E. E. HARRINGTON

1. INTRODUCTION. AT the Lake Superior meeting, September, 1904, Messrs. A. Gibb and R. C. Philp presented a paper entitled " The Constitution of Mattes Produced in Copper Smelting,)&apos; in which they concluded that ferrous and cuprous sulphides formed the chemical compound, 5 Cu2S, fee. They arrived at this inference from the observed fact that a matte containing Cu2S, 90.4, and Fee, 9.6 per cent (or, in round figures, Cu2S, 90, and Fee, 10 per cent.), did not contain any metallic copper, while one with more than 10 per cent of FeS readily dissolved copper, and with less than this amount retained copper in mechanical suspension. Although they determined the melting-points of five mattes containing from 32.6 to 80.1 per cent of copper, they did not draw a freezing-point curve, as the necessary apparatus was not available. A microscopical examination of 11 polished samples, gave them a grayish-black field of very uniform appearance, except that 5 of the specimens showed the presence of metallic copper. The object of the present investigation was to supplement the above paper by drawing the freezing-point curve of the series ferrous sulphide cuprous sulphide, and to see how the constitution could be further, revealed by microscopical work. The results obtained lead to conclusions very different from those of Gibb and Philp. While their paper bears the date 1904, it was published only in 1906.2 In the meantime, Bolles3 had presented his paper, "The Concentration of Gold and Silver in Iron Bottoms." The raw material which formed the basis of the research was a matte containing Fe, 61.68, and Cu, 11.20

Jan 1, 1907