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By Otto F. Pfordte

In my paper on " The Refilling of Sulphides Obtaihed in the Lixiviation-Process with Hyposulphite Solutions " (Trans., xx., 37), I gave the outlines of a process for refining sulphides. In a subse-

Jan 1, 1893

By A. O. Dady

PRODUCERS of both bituminous and anthracite coal have for many years been worrying about the gradually decreasing consumption of their product in the United States. Twenty years ago production had climbed to a peak of 569,000,000 tons of bituminous and around 90,000,000 tons of anthracite. In 1939 it was about 393,000,000 tons of bituminous and 51,000,000 tons of anthracite. This does not mean that the country is using less polver than it did twenty years ago, or that we are living in colder buildings. As a matter of fact, about three times as much electric power is now being consumed as in 1920. In general two factors are responsible for the drop in coal consumption: (1) greater efficiency in the use of coal, and (2) increased competition from hydro power, internal-combustion engines, and substitution of oil and gas for coal in conventional furnaces. As to the first factor, it took 3 Ib. of coal to generate a kilowatt-hour of electricity in central stations in 1920 and it takes 1.4 Ib. now; it took about 175 Ib. of coal in railroad locomotives to haul 1000 long tons a mile in 1920 where it talces about 120 lb. now: and marked economies have also been made in the use of coal in steel plants: in by-product coke ovens, and in other large uses. As to the second factor, three times as much electricity is produced from water power now as was produced in 1920; three times as much oil is being consumed in various ways; and likewise, the consumption of natural gas has tripled- whereas coal consumption in the same period has dropped by 40 per cent

Jan 1, 1941

By L. Valentik

Many attempts have been made during the last 40 years to evaluate the performance of gravity separation equipement, that is, the effectiveness with which light and heavy particles are separated. The most comprehensive treatment of the subject was made by Cerchar at the 1st International Conference on Coal Preparation held in Paris in 1950. The methods suggested by the Conference were accepted and very widely used in the last two decades. This paper discusses an improved method of evaluation in the light of the now-accepted standard presentation. The float-and-sink analysis of the product is presented on a Gaussian distribution curve, resulting in an easier visualization of the inherent difficulties of separation. The ogives of the distribution curve me then plotted, giving a quantitative measure of the deviation from perfect separation as an error distance instead of an error area. Illustrations of the new method are given both for gravel and for coal preparation, but the content is valid and applicable to other types of minerals which are separated by gravity methods. Many attempts had been made during the last forty years to evaluate the performance of heavy-media separation (HMS) equipment, that is, the effectiveness with which floats and sinks are separated.'-' The most comprehensive treatment of the subject was made by Cerchar at the 1st International Conference on Coal Preparation held in Paris. 6 The primary aim was the thorough understanding of the mechanism of separation and the unified presentation of data on gravity separation so that the evaluation and comparison of washery performance could be made from all over the world. No strict overall standardization has been achieved, but after the conference a more or less uniform presentation of performance was accepted, which, during the last two decades, has been very widely used. In this paper, illustration of the old methods and an improved method of evaluation will be given. HEAVY-MEDIA SEPARATION (HMS) PERFORMANCE CRITERIA In the ideal HMS process, all material lower in density than the specific gravity of separation (SGS) would be recovered as floats and all material of higher density would appear as sinks. In order to evaluate the misplaced material, the washery products are tested at the density at which the washing unit is operated. The original type of plot1,7, 8 is shown in Fig 1; this was developed primarily for coal cleaning units. The curve for raw coal represents the cumulative percentages of sink material. The refuse curve is also plotted as a cumulative sink, the percentages being expressed in terms of raw coal. This diagrammatic representation of the results of washing units has the merit of easy visual observance of the degree of separation obtained. The error areas (cross-hatched) are a measure of the amount of misplaced material and therefore they can be used to characterize the quality of separation. The ideal and actual separating performance between floats and sinks can be best seen from the partition curve developed by Tromp,2 where the ordinate is the percentage recovery of the sinks, and the abscissa is the specific gravity (Fig. 2). It can be seen from the shape of the curve that as the SGS is approached, the proportion of material reporting to the improper product increases rapidly. In fact, the SGS can be defined as the density of the material in the feed that is distributed equally between float-and-sink products. When the upper half of the curve is inverted, a shape similar to that of a Gaussian error distribution curve is obtained and therefore the analysis of gravity separation may be carried out by using the law of probability. The shape of the curve in Fig. 2 is determined partly by the density composition of the feed, and partly by the sharpness with which the unit separates floats from the sinks.9, l0

Jan 1, 1970

R. W. Raymond, New York, N. Y,:—Since the presentation of my note on this subject at the New York Meeting, Professor Louis has pointed out an error in my statement of his conception of " pitch "—namely, he understands the pitch, in the restricted sense which he proposes, to be the angle of inclination of the axis of an ore-body, measured on the vertical plane drawn through the body; whereas, I represented him as proposing to define " pitch " as the angle of inclination of an oblique body, measured on the plane of the dip, in the direction of the strike. The difference will appear upon consideration of the accompanying isometric projection, Fig. 1, in which ABCD represents the plane of the inclosing ore-deposit (vein or bed), and AC the axis of the oblique ore-shoot. ABE is the angle of the dip, as universally understood; and ACE

Jan 1, 1909

By C. E. Sims, C. A. Zapffe

MANY hundreds of publications have appeared during the past 78 years that treat the subject of hydrogen in iron and steel,105 but conclusions regarding the functions of hydrogen in causing some important defects in steel are still unsatisfactory to many; and other hydrogen-caused phenomena yet remain to be identified with this gas. The most widely discussed of these defects is hydrogen embrittlement, but the conception, perhaps the popular one, that embrittlement is due to hydride formation does not conform to the known facts.104 The true identity of hydrogen embrittlement seems instead to lie in a mosaic nature of metal crystals, which is a concept not yet accepted by most metallurgists. A study of hydrogen embrittlement therefore provides new viewpoints in regard to the crystalline substructure of steel. A second widely discussed hydrogen-caused defect is the "flake" or "shatter crack." Although it is generally agreed that the presence of hydrogen is a prerequisite for their appearance, it is also realized that internal stress plays a decisive part. The relationship of hydrogen to internal stress has not been explained very clearly; nor is it always clear what the relationship is between a "flake" and a "snowflake," or between a "fish eye" and a "shatter crack." More importantly, the relationships among hydrogen embrittlement, hydrogen-caused fissures such as "flakes" and the ultramicroscopic structure of steel have scarcely been recognized. The present investigation attempts to provide an explanation for the embrittlement of steel by hydrogen by showing cause for accepting the "block" concept of metal crystals, and then to show how the numerous hydrogen-caused defects are interrelated in the light of this concept. EVIDENCE OF SUBSTRUCTURE IN METAL CRYSTALS It appears that the concept of a crystal as an aggregate of smaller multi-atom units must be accepted in some form if the behavior of metals is to be understood. The abundant literature on the evidence of an ultramicroscopic "mosaic" structure in metals and other crystalline substances suggests that the physicist has provided the metallurgist with an invaluable new insight. The exact picturization that any one physicist provides may be open to question, but the fact that there is some such fundamental substructure seems undeniable. The present work makes no pretense of comprehensively treating the imperfection structure theories. Nor will conclusions be drawn here regarding the exact nature of the substructure of crystals. However, the acceptance of some imperfection theory of fundamental attributes seems so necessary to an understanding of the behavior of hydrogen in steel that the following brief

Jan 1, 1941

J. E. Johnson, Jr., Glen Wilton, Va. (communication to the Secretary*):—Mr. Meissner announces early in his paper that one of its purposes is the discussion of my paper entitled, Notes on the Physical Action of the Blast-Furnace,' with which he disagrees in part; and as the second stage of the discussion of this important subject has centered around his paper, some reply by me may not be amiss. Unfortunately, Mr. Meissner has not indicated a single statement or conclusion in my paper that he wishes to controvert; but as there is evidently a difference of opinion between us I will disregard this fact, and will discuss those conclusions of his that seem to me not to be justified by the facts of general practice, or even by the data which he produces to support them. Let me say, however, that I am a believer in the dry-air

Jan 1, 1908

New York, March 18, 1913. MR. CHARLES F. RA ND, President, New YORK, MARCH American Institute of Mining Engineers. Dear Sir: In connection with the official notice of Dr. Raymond's unanimous election by the Directors as Secretary Emeritus, we wish to place upon record certain statements concerning his services to the Institute which we think have not been published., and may not be generally known to the majority of our fellow-members. When the Institute was formed in 1871, Dr. Raymond acted as Secretary of the Founders' Meeting, and became the first Vice-President of the Institute, and, by request of the aged and beloved David Thomas, who was the first President of the Institute, Dr. Raymond discharged all the duties of the office of President, to which he was later formally elected in 1872, and which lip held for three years. During that time, he visited Europe, and through his acquaintance and reputation abroad, established those international relations of the Institute which proved so important in later years. He also enlisted the support of the mining engineers and metallurgists of the Pacific Slope, who would not otherwise have been disposed to join a society originating in the East. And for twelve years he attended; at his own expense, nearly every meeting of the Institute, wherever held, giving to it without remuneration his best service, and sacrificing for it many professional and private interests.

Jan 4, 1913

By Robert F. Mehl

THE solid solutions which aluminum forms with copper, and with magnesium and silicon, are not extensive, and accordingly could not be expected to form Widmanstätten figures profusely nor with great ease. A study of the Widmanstätten figures in these systems seemed desirable, however, because of the interest which these alloys bear towards age-hardening theories resulting from the necessary relationship between the age-hardening phenomena and the atomic processes leading to the formation of Widmanstätten figures.1 ALLOYS OF ALUMINUM WITH COPPER The most accurate determination f the solid solubility, of copper in aluminum seems to be that by Dix and Richardson,2 whose results are represented in Fig. 1. According to this work, aluminum dissolves 5.6 weight per cent of copper at 548°, and less than one per cent at room temperature. Judging from the constitutional diagram, this solid solution on cooling tends to precipitate the compound CuAl2, and this conclusion has been confirmed experimentally by Schmid and Wassermann .3

Jan 1, 1932

By R. W. Raymond

Recent literary labors have led me to the compilation of the following tables and estimates, which may possess interest for my colleagues in the Institute, and which are here submitted without comment.

By AIME AIME

AT FOUR O'CLOCK members gathered in the auditorium for the annual business meeting of the Institute which, according to its charter, must be held on the third Tuesday of February each year. President Turner presided and after the usual formal action on minutes announced that he would create a precedent by transferring the President's annual address (which by tradition has always been delivered at the banquet on Wednesday evening) to the business meeting, and, furthermore, would only present a brief abstract of it. Since it appears in full on pages 127-131 of this issue it can be followed with the careful attention its thoughtful analysis of current conditions deserves.

Jan 1, 1933

By W. A. Backofen, D. Lee

Tlze condition of superplasticity or neck-resistanl flow that results front high strain-rate sensitivity has been observed in isothermal tension tests on several titanium alloys and one of zirconium hi general, il was associated with reasonably fine-grain micro-structures being stvained in the transformation range at rates below i - 10 -3 sec-&apos;. The metallographic mean-free path, L, was measured at room temperature after rapid cooling from the temperature of test-ing. The flow stress of Ti-GAL-4V at 950°C was proportional to La at different constanl <; the value of a decreased with increasing. E but at E< 1.5 x 10-4 sec-1 it varied only from 0.9 to 1.25. The findings were interpreted to mean that viscous boundary shear is the rate-controlling process of deformation at high levels of strain rate sensitivity in these materials. Elongation of over 1000 pet could be obtained, but a1 temperatures so high and rates so low that any practical application of the full effect would probably be difficult. As the transformation range was narrowed, by turning from Ti-6AL-4V to Ti-5Al-2.5sn to nomznally pure titanium, the allowable temperature varialion was correspondingly reduced. Superplasticily was not found in Armco iron, presumably because the transformation range was too narrow to allow the developtnenl of a reasonably stable microstructure for isolhermal lesting. THE work represented by this paper grew out of a recent study of texture hardening in a(hcp) titanium and zirconium-alloy sheet,&apos; of which part has now been published.2 It was found that, with heating, the tensile plastic-anisotropy index, R,* was decreased from well above 1 towards 1 as the temperature range for the a(hcp) -ß(bcc) phase change was entered. The clearest example of that trend is illustrated with previously unpublished data in Fig. 1. It might have been thought that such a development resulted simply from introduction of the cubic and therefore plastically less anisotropic phase. However, the accompanying change in the index of tensile strain-rate sensitivity, m = a log a/a log E, was rapidly upwards, to a high of 0.85 in some cases (also illustrated in Fig. 1). At the same time, the total tensile elongation rose to a maximum and the flow strength dropped away as R (and m) approached 1. Taken together, the observations cannot be understood as resulting from the presence of cubic phase, per se. It has been concluded instead that they reflect the largely noncrystallographic deformation which characterizes superplasticity. As demonstrated in other recent work? a necessary condition for super-plasticity is strain-rate sensitivity of flow stress sufficiently high that m is above a lower limit of -0.3. The origin of large m has been traced, in turn, to grain size so small that a substantial amount of viscous deformation is introduced by such processes as Nabarro-Herring diffusional flow4 and/or grain boundary shear.5,6 Because of problems in the processing of titanium and zirconium alloys—problems of high strength, limited ductility, and excessive springback, originating largely in slip resistance-it was natural to wonder if something useful might be done with superplasticity in those materials. Therefore experiments were made for more closely identifying and generally bounding the phenomenon with temperature and strain-rate limits, before attempting to decide about its exploitation. The results are being reported here. EXPERIMENTAL Materials. The two of primary interest were the titanium alloys of nominal composition (in wt pct) 5A1-2.5Sn and 6A1-4V. Others were a 4A1-1/4O2 titanium alloy, titanium of commercial purity (RC-70), Zircaloy-4. and Armco iron. All were received as annealed 3/16 in. thick sheet, except RC-70 which was & in. thick, and tested in that condition. Details of transformation temperature and grain size are given in Table I. The results of dilatometry for the measurement of transformation temperatures were unsatisfactory. Data were finally obtained by metallographic examination of each specimen after test, to determine from the amount of transformed 4 where the specimen had been heated in relation to the critical temperatures. Results were in reasonable agreement with information from the supplier. Strip tensile specimens were of full sheet thickness and taken along the rolling direction, except for those

Jan 1, 1968

By Gerhard Derge, J. Warren Stewart

Extrusion processes are used in the commercial production of a wide variety of products, as indicated by the review presented a few years ago by D. K. Crampton.&apos; Most writers have confined themselves to a general description of the equipment and products and the engineering aspects of the process. The few studies that have dealt with the metallurgical side of extrusion have been concerned primarily with an examination of the mode of flow of the metal during extrusion. This has been accomplished by the use of composite billets, by scribing grids on symmetrical sections of billets and observing the change of dimensions in the gridwork, or by examining microstructures in extruded sections.2"8 Ariotlier limitation of these original studies is that they were confined to the extrusion of very simple shapes, usually rods having a diameter of about one-fourth that of the billet. Tin is particularly well suited to the extrusion of collapsible tubes and similar shapes in which the extruded section is very small in comparison to the diameter of the billet or slug. In modern production, impact extrusion methods are generally employed, therefore the thickness of the slug is small compared to its diameter. Under these conditions the process differs considerably from the processes that have been most fully described in the literature, and it is known that the quality of the product is very sensitive to slight variations in any one of the many variable factors involved, such as coinposition and structure of the alloy, rate of extrusion, temperature, shape of punch and die. An exhaustive examination of all of the above-mentioned problems promises to produce so many data that it seems advisable to initiate the reports at this time, even though all of the factors outlined have not been examined fully, and to confine this paper to a description of the apparatus and method. Only tin and its alloys with small amounts of copper have been considered. These are the alloys most commonly used in this country for the production of the type of articles already described.

Jan 1, 1940

By Gerhard Derge, J. Warren Stewart

Extrusion processes are used in the commercial production of a wide variety of products, as indicated by the review presented a few years ago by D. K. Crampton.&apos; Most writers have confined themselves to a general description of the equipment and products and the engineering aspects of the process. The few studies that have dealt with the metallurgical side of extrusion have been concerned primarily with an examination of the mode of flow of the metal during extrusion. This has been accomplished by the use of composite billets, by scribing grids on symmetrical sections of billets and observing the change of dimensions in the gridwork, or by examining microstructures in extruded sections.2"8 Ariotlier limitation of these original studies is that they were confined to the extrusion of very simple shapes, usually rods having a diameter of about one-fourth that of the billet. Tin is particularly well suited to the extrusion of collapsible tubes and similar shapes in which the extruded section is very small in comparison to the diameter of the billet or slug. In modern production, impact extrusion methods are generally employed, therefore the thickness of the slug is small compared to its diameter. Under these conditions the process differs considerably from the processes that have been most fully described in the literature, and it is known that the quality of the product is very sensitive to slight variations in any one of the many variable factors involved, such as coinposition and structure of the alloy, rate of extrusion, temperature, shape of punch and die. An exhaustive examination of all of the above-mentioned problems promises to produce so many data that it seems advisable to initiate the reports at this time, even though all of the factors outlined have not been examined fully, and to confine this paper to a description of the apparatus and method. Only tin and its alloys with small amounts of copper have been considered. These are the alloys most commonly used in this country for the production of the type of articles already described.

Jan 1, 1940

Albert SauveuR, South Chicago, Ill. (communication to the Secretary): Mr. Howe remarks (nuns., xxiii., 656) that, running through my paper, there is a tacit assumption that there is a constant and known relation between the coarseness of the grain of steel and its quality. The above assumption was not made tacitly. On the contrary, it is based upon the very experiments embodied in my paper. Indeed, most of those experiments were undertaken with that end in view, i.e., to ascertain the existence of such a relation. Mr. Howe calls attention to the fact that of two pieces of manganese-steel, originally from the same bar, the coarser-grained showed the greater strength and ductility. This refers to the fracture of the pieces; whereas, I have considered the micro-structure only, independent of the fracture; and I do not think that a coarse fracture

Jan 1, 1895

Discussion of the paper of CHARLES H. MACDOWELL, presented at the New York meeting, February, 1915, and printed in Bulletin No. 98, February, 1915, pp. 103 to 114. GEORGE S. RICE, Pittsburgh, Pa.-I am especially interested in the mining side of this important question. In 1911, when in Europe investigating mining matters, giving special attention to subsidence clue to mining, for there is a very big problem of that kind, as many of you know, in the Pennsylvania anthracite region, I visited Stassfurt, which is one of the chief centers of potash mining, and which was pointed out as the place to see surface subsidence. We found the town much askewsome of the streets having sunk from 15 to 30 ft., leaving many ancient buildings pitching at various angles. One old church, 500 or 600 years old, has been sunk about 20 ft., cracking it badly. I understand that this condition came about because in early mining clays they were careless about leaving proper supports and used no filling or packing. The Stassfurt mines work along a buried anticline the sides of which pitch at 45° on the average. Through this careless mining they had a break of the hanging wall which let in water from the overlying marls and sands. The water rapidly dissolved the salts in the pillars, and spreading through the entire chain of mines, caused their complete loss, with serious trouble for the old city. They had to start new mines some distance away, and take care to prevent roof caves. The packing system is of interest. They were driving large rooms into the rock-salt foot wall and using the rock salt as dry filling. The application of hydraulic filling, using a saturated solution, was under contemplation at some plant nearby. Whether 6r not the plan was carried out I do not know. I was reminded of the plan by Mr. MacDowell&apos;s remarking on the use of a saturated salt solution in the core drilling. His reference to the apparent breakdown of the potash syndicate raises an interesting question. We have had the German system of syndicates pointed out as perhaps one means of solving our troubles in the soft-coal mining industry due to overproduction. It seems to have worked out admirably in the case of the Westphalian coal-mining syndicate and also in the syndicate of Upper Silesia; but apparently the syndicate plan did not work in the potash industry. .

Jan 5, 1915

By H. G. Landua, Leah L. Naugle, H. H. Lowry

Evidence has been accumulating in recent years, in part from the work of the Coal Research Laboratory, that coals belong to a family of natural polymers and that even in complex reactions the differences between coals are quantitative and not qualitative. This point of view leads to the expectation that if a series of coals were subjected to a closely controlled set of experimental conditions the results obtained should be related to the chemical analyses of the individual coals. The data accumulated over the past 10 years by the Bureau of Mines in its (&apos;Survey of Coke-, Gas-, and By-Product-Making Properties of American Coals," in what has come to be recognized as the Bureau of Mines-American Gas Association (BM-AGA) carbonization assay test,l-l2 offer an unusual opportunity to check this conclusion. The present paper reports an analysis of the data on the first go coals and coal blends— including coals numbered I to 55B, inclusive —which have been carbonized according to a standard procedure at intervals of 100°C. from 500° to 1100° in either or both 13 or 18-in. cylindrical retorts.13 In Table I are given the name of the seam from which the sample was obtained, the analytical data used, and the reference to the original publication of the Bureau of Mines. The coals range in fixed carbon from 46.2 to 79.0 per cent, in volatile matter from 15.4 to 41.3 per cent, in ash from 2.1 to 15.9 per cent, in moisture from 0.8 to 19.7 per cent, and in total sulphur from 0.40 to 4.44 per cent; therefore the entire gamut of bituminous coals is represented. The petrographic nature of the individual coals is not considered in the following analysis, although both "normal" bright coals and splint coals are included in the samples studied. For information on the petrography of the coals and for further information characterizing the coals the original papers should be consulted. Although the coals that are included extend over the whole range of bituminous coals, they do not cover this range entirely adequately. In particular, only 13 of the 90 coals have moisture contents greater than 3 per cent. This concentration at low moisture values means that the effect of moisture, which is an important factor, cannot be determined with as much certainty as would be desirable. All the coals were not tested at every temperature and in both retort sizes. Only the first 30 coals were tested at 1100°, and only about 50 at the other temperatures, except at 900°, where nearly all of them were included. In the accompanying tables the actual number of observations entering into each correlation is given. In this study equations are given for calculating analyses, yields, and properties of coke and by-products from the coal analyses. To decide whether these equations are satisfactory it is necessary to know the accuracy with which these quantities were measured in the assay tests.

Jan 1, 1942

By Leah L. Naugle, H. H. Lowry, H. G. Landua

Evidence has been accumulating in recent years, in part from the work of the Coal Research Laboratory, that coals belong to a family of natural polymers and that even in complex reactions the differences between coals are quantitative and not qualitative. This point of view leads to the expectation that if a series of coals were subjected to a closely controlled set of experimental conditions the results obtained should be related to the chemical analyses of the individual coals. The data accumulated over the past 10 years by the Bureau of Mines in its (&apos;Survey of Coke-, Gas-, and By-Product-Making Properties of American Coals," in what has come to be recognized as the Bureau of Mines-American Gas Association (BM-AGA) carbonization assay test,l-l2 offer an unusual opportunity to check this conclusion. The present paper reports an analysis of the data on the first go coals and coal blends— including coals numbered I to 55B, inclusive —which have been carbonized according to a standard procedure at intervals of 100°C. from 500° to 1100° in either or both 13 or 18-in. cylindrical retorts.13 In Table I are given the name of the seam from which the sample was obtained, the analytical data used, and the reference to the original publication of the Bureau of Mines. The coals range in fixed carbon from 46.2 to 79.0 per cent, in volatile matter from 15.4 to 41.3 per cent, in ash from 2.1 to 15.9 per cent, in moisture from 0.8 to 19.7 per cent, and in total sulphur from 0.40 to 4.44 per cent; therefore the entire gamut of bituminous coals is represented. The petrographic nature of the individual coals is not considered in the following analysis, although both "normal" bright coals and splint coals are included in the samples studied. For information on the petrography of the coals and for further information characterizing the coals the original papers should be consulted. Although the coals that are included extend over the whole range of bituminous coals, they do not cover this range entirely adequately. In particular, only 13 of the 90 coals have moisture contents greater than 3 per cent. This concentration at low moisture values means that the effect of moisture, which is an important factor, cannot be determined with as much certainty as would be desirable. All the coals were not tested at every temperature and in both retort sizes. Only the first 30 coals were tested at 1100°, and only about 50 at the other temperatures, except at 900°, where nearly all of them were included. In the accompanying tables the actual number of observations entering into each correlation is given. In this study equations are given for calculating analyses, yields, and properties of coke and by-products from the coal analyses. To decide whether these equations are satisfactory it is necessary to know the accuracy with which these quantities were measured in the assay tests.

Jan 1, 1942

By Edwin A. Sperry

In 1892 I tested an ore, which was peculiarly difficult to treat, on several concentrators then in general use, including t,he Frue-vanner, the Luhrig table and the Cornish buddle. Owing to the character of the ore it had to be crushed- to a very fine state of division, and the results obtained were far from satisfactory; a large proportion of the values was lost in the slimes, which indicated the necessity of a very careful sizing before dressing. Even after reworking some of the slime-tailings, the results, in my opinion, were not as good aa those which might be obtained on a table designed more especially for the handling of slime. Although the subject of slime-concentration has occupied the attention of many engineers who have threshed the field quite thoroughly, the results obtained in my work led to a careful

Jan 1, 1904

By A. U. Seybolt

The pressure-temperature relations required to maintain the existence of Si3N4 in silicon-iron of 0.44-11.7 pet Si have been partially explored. The critical data obtained have allowed the calculation of some thermodynamic quantities, and have shown evidence of an order-disorder two-phase field extending at 800°C from about l pet to 5.5 pet Si. THE presence of silicon nitride in electrical sheet, nominally about 3 1/4 pet silicon, balance iron, has been described by several authors&apos;" but there has been some discrepancy among them regarding the identity of the nitride. Also, little has been reported on the quantitative thermodynamic prop- erties. In the work to be reported here, the nitride has been found to be more stable than described by Corney and Turkdogan." Several silicon nitrides have been described in the past, including SiN, Si3N4 and Si2N4 (see, for example, Abegg6 and Pascal7). However, the literature on nitrides other than Si,N, is all very old. No recent investigators using the more powerful tools available today have reported the presence of any nitride other than S3,N4. W. B. Hicke and L. R. Brantley8 in 1930 determined the dissociation pressure of Si3N4 which they made by reacting nitrogen

Jan 1, 1959

By R. W. Raymond

RECENT literary labors have led me to the compilation of the following tables and estimates, which may possess interest for my colleagues in the Institute, and which are here submitted without comment.

Jan 1, 1876