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By C. M. Brinckerhoff

Safety work in mining at the Andes Copper Mining Company, Potrerillos, Chile, is divided into three parts: (1) accident prevention, (2) fire prevention and protection, and (3) silicosis prevention and control. In the company's operations a steady campaign has been waged to reduce accidents and silicosis, and to prevent fires. In the following pages the safety record for the past twelve years will be examined and the methods explained by which the accident rate was reduced. Table 1 contains yearly data pertaining to the scale of the mining operations and the accident record. Block caving is used for all ore production and the tonnage mined has aver- aged 30,000 short tons per day for the past seven years. Table 2 classifies 44 fatal accidents which have occurred since 1935. The leading causes of accidental death are transportation of ore and use of explosives, followed in order by per- sons falling, falls of ground, and by asphyxiation. In the case of serious accidents, however, the greatest cause is falls of ground, followed, in turn, by ore

Jan 1, 1949

By F. R. Morral

INDUSTRY has yet to find a universal solution to the problem of engineer personnel selection. Today, the choice of the right man for the right job is even more pressing than ever before. The age of the hard apprenticeship seems to have passed. In its place one finds the interviewer who must determine through personal contact and evaluation of college grades whether a graduate engineer will fit into his company's scheme. The problem, as it is constituted today, may be broken into four parts: Need for better use of human resources (there is a shortage of engineers, scientists, and skilled workers), productivity with higher efficiency, encouragement of personal pride in work performed, and employee's happiness on the job and away from it.

Jan 4, 1953

By Ralph Hultgren

A CONSIDERABLE interest in the subject of superlattices has been mani-fested by many papers and reviews that have recently appeared, both in physical and metallurgical publications. This interest is due largely to the apparent simplicity of the ordering process, which permits the explana-tion of many phenomena on the basis of elementary theory. Moreover, ordering may cause important changes in the physical properties of alloys. In this paper, we shall discuss the causes of superlattices in terms of simple properties of the elements that give rise to them, together with a series of experiments performed to test our conclusions. Evidence is presented that in some cases the process of ordering is more complex than might be supposed. While the different species of atoms are usually found in random posi-tions in alloy lattices, in some cases unlike atoms tend to be nearest neighbors. Bethe'st "order of neighbors" is a statistical measure of this tendency. At suitable compositions it is possible for atoms in large regions to be regularly arranged, which causes superlattice lines to appear in X-ray diffraction patterns. Bragg and Williams2 have dealt with this "long-distance order" in their fundamental work on superlattices. Excellent discussions of superlattices are to be found in current reviews.3,4

Jan 1, 1939

By B. F. Zwick

The entire production of oil in Ecuador so far has come from the Santa Elens Peninsula, Province of Guayas. Both the shallow fields of the northern and the deeper fields of the southern part of the peninsula have been in constant exploitation, though the former are of doubtful economic value. In Table I herewith, which commences with the total amounts produced by the various companies up to 1940, annual company totals are given for the succeeding years. The figures for 1944 have been partly estimated. Table 2 gives figures on casinghead gasoline. Shell Company of Ecuador (formerly known as Anglo-Saxon) has continued active exploration in the Oriente region east of the Andes, and during 1944 the Company's first wildcat well was spudded in. International Ecuadorean Petroleum Co. (formerly International Petroleum Co., Limited) has pursued an active exploration campaign since the latter part of 1939, and a drilling string was placed in operation about a year later. A second string of tools was added during 1943 and a third a few months ago. Ten wildcats, all dry, have been completed in this period, two wells are drilling at the present time and other locations are on the program. Seven of the wells thus far drilled are in the area between Guayaquil and the Santa Elena Peninsula, one up the Daule River beyond Balzar, one on Puna Island in the Guayas Estuary and one in the northern province of Esmeraldas. Both the present drilling wells are in the Guayaquil-Santa Elena zone. The situation in regard to concessions has changed during the past four years because I.E.P.C. has made its selections from the extensive Daule-Guayas Study Concession, as a result of which large tracts were returned to the Government; because of the expropriation of the holdings of the "Ecuapetrol," a German concern whose acreage has passed into other hands; the Peruvian-Ecuadorean boundary settlement, which has reduced Shell's holdings somewhat; and the transfer of most of the holdings of the Cia. Minero-Petrolera del Pacifico to I.E.P,C. The greater part

Jan 1, 1945

The Development of Research and Quality Control in the Modern Steel Plant. By Leo F. Rein-artz. (Metals Technology, April 1943) Blast Furnace and Raw Materials Essential Considerations in the Design of Blast Furnaces. By A. L. Foell. (,Metals Technology, December 1942) Results Obtained from Surveys of Gas at Furnace Tops. By James M. Stapleton. (Metals Technology, January 1943) Physical Aspects of the Dust Catcher, Gas Washer and Precipitator on No. 3 Furnace at Carrie. By C. P. Clingerman and C. J. FleiscH. (Metals Technology, January 1943) Slag Control by Introduction of Flux through Blast-furnace Tuyeres. By Carl G. Hogberg (Metals Technology, January 1943) The Electrical Conductivity of Molten Blast-furnace Slags. By A. E. MaRtin and GerRard Derge. (Metals Technology, August 1943) Some Physical Characteristics of By-product Coke for Blast Furnaces. By CEarles C. Russell and MichaeL Perch. (Metals Technology, December 19+2) Pyrometry at the Coke Oven. By Robert B. Sosman. (Metals Technology, December 1942) Calcination Rates and Sizing of Blast-furnace Flux. By T. L. Joseph, H. M. Beatty and Gust Ritsianes. (Metals Technology, December 1942) The Low-temperature Gaseous Reduction of a Magnetite. By M. C. Udy and C. H. Lorig. (Metals Technology, October 1942) Steelmaking Problems of Total Operation in Steelmaking. By William C. Marshall and Frank G. Norris. (Metals Technology, April 1943) Silicon-oxygen Equilibria in Liquid Iron, By C. A. ZapFFe and C. E. Sims. (Metals Technology, September 1942) Equilibria of Liquid Iron and Simple Basic and Acid Slags in a Rolating Induction Furnace. By C. R. Taylor and John Chipman. (Metals Technology, September 1942) Rapid Analysis of Oxygen in Molten Iron and Steel. By Gerhard DeRGe. (Metals Technology, January 1943) Silver Chloride as a Medium for Study of Ingot Structures. By Karl L. Fetters and Margaret Dienes. (Metals Technology, August 1943)

Jan 1, 1943

The Development of Research and Quality Control in the Modern Steel Plant. By Leo F. Rein-artz. (Metals Technology, April 1943) Blast Furnace and Raw Materials Essential Considerations in the Design of Blast Furnaces. By A. L. Foell. (,Metals Technology, December 1942) Results Obtained from Surveys of Gas at Furnace Tops. By James M. Stapleton. (Metals Technology, January 1943) Physical Aspects of the Dust Catcher, Gas Washer and Precipitator on No. 3 Furnace at Carrie. By C. P. Clingerman and C. J. FleiscH. (Metals Technology, January 1943) Slag Control by Introduction of Flux through Blast-furnace Tuyeres. By Carl G. Hogberg (Metals Technology, January 1943) The Electrical Conductivity of Molten Blast-furnace Slags. By A. E. MaRtin and GerRard Derge. (Metals Technology, August 1943) Some Physical Characteristics of By-product Coke for Blast Furnaces. By CEarles C. Russell and MichaeL Perch. (Metals Technology, December 19+2) Pyrometry at the Coke Oven. By Robert B. Sosman. (Metals Technology, December 1942) Calcination Rates and Sizing of Blast-furnace Flux. By T. L. Joseph, H. M. Beatty and Gust Ritsianes. (Metals Technology, December 1942) The Low-temperature Gaseous Reduction of a Magnetite. By M. C. Udy and C. H. Lorig. (Metals Technology, October 1942) Steelmaking Problems of Total Operation in Steelmaking. By William C. Marshall and Frank G. Norris. (Metals Technology, April 1943) Silicon-oxygen Equilibria in Liquid Iron, By C. A. ZapFFe and C. E. Sims. (Metals Technology, September 1942) Equilibria of Liquid Iron and Simple Basic and Acid Slags in a Rolating Induction Furnace. By C. R. Taylor and John Chipman. (Metals Technology, September 1942) Rapid Analysis of Oxygen in Molten Iron and Steel. By Gerhard DeRGe. (Metals Technology, January 1943) Silver Chloride as a Medium for Study of Ingot Structures. By Karl L. Fetters and Margaret Dienes. (Metals Technology, August 1943)

Jan 1, 1943

Jan 1, 1968

Jan 1, 1967

By Jack R. Elenbaas, Donald L. Katz

A radial turbulent flow formula has been developed which permits the computation of the pressure drop for radial flow in gas wells whether the flow is laminar, turbulent, or partially laminar and partially turbulent. Using the formula a complete back-pressure curve has been calculated and analyzed by a comparison with existing back-pressure curves. A procedure is presented for computing the permeability of the porous media when the porosity, sphericity and average particle diameter are known. Introduction Recent studies on the flow of fluids through porous media have provided new methods for computing flow under turbulent conditions. The present study was initiated as an investigation of pressure -drop computations for flow through porous sands in gas wells and as an analysis of present-day back-pressure tests. Although laminar flow exists in the producing formation of gas wells under normal flow rates, turbulent flow does take place adjacent to the well bore. As the flow rate is increased, turbulent flow exists further and further into the producing formation and under open-flow conditions in relatively deep wells a considerable portion of the flow through the sand will be turbulent. In order to calculate a complete backpressure curve for relatively deep wells without resorting to extrapolation of curves drawn from data obtained in back-pressure tests or calculations made in the completely laminar region, it was necessary to have some means of calculating pressure drop for flow through porous sands under turbulent conditions.4.6 As a result, a radial turbulent flow formula was derived from the equations recently presented by Brownell and Katz.1 A rigorous solution of this equation involves a trial and error graphical integration. By making the assumptions of average viscosity, temperature and compressibility factor of the flowing gas, it was possible to graphically integrate the relation for the general case of radial flow of gases through the porous sand of gas wells. A chart has been prepared relating the value of the integral to the radius of the well bore and to the Reynolds number of the flowing gas. The chart actually performs the graphical integration and the solution of the formula is then reduced to a simple trial and error calculation. A typical back-pressure curve is calculated to show the transition from laminar to turbulent flow. This paper will briefly describe the pro-cedurcs for computing flow through porous media, including a method for predicting sand permeability from porosity and grain size and shape. Flow through Porous Media Brownell and Katzl recently reported a correlation for computing flow of fluids through porous media by the use of an enlarged Reynolds number and friction factor in which the porosity of the bed is included as an additional prime variable. The enlargcd Reynolds number com-

Jan 1, 1948

By Donald L. Katz, Jack R. Elenbaas

A radial turbulent flow formula has been developed which permits the computation of the pressure drop for radial flow in gas wells whether the flow is laminar, turbulent, or partially laminar and partially turbulent. Using the formula a complete back-pressure curve has been calculated and analyzed by a comparison with existing back-pressure curves. A procedure is presented for computing the permeability of the porous media when the porosity, sphericity and average particle diameter are known. Introduction Recent studies on the flow of fluids through porous media have provided new methods for computing flow under turbulent conditions. The present study was initiated as an investigation of pressure -drop computations for flow through porous sands in gas wells and as an analysis of present-day back-pressure tests. Although laminar flow exists in the producing formation of gas wells under normal flow rates, turbulent flow does take place adjacent to the well bore. As the flow rate is increased, turbulent flow exists further and further into the producing formation and under open-flow conditions in relatively deep wells a considerable portion of the flow through the sand will be turbulent. In order to calculate a complete backpressure curve for relatively deep wells without resorting to extrapolation of curves drawn from data obtained in back-pressure tests or calculations made in the completely laminar region, it was necessary to have some means of calculating pressure drop for flow through porous sands under turbulent conditions.4.6 As a result, a radial turbulent flow formula was derived from the equations recently presented by Brownell and Katz.1 A rigorous solution of this equation involves a trial and error graphical integration. By making the assumptions of average viscosity, temperature and compressibility factor of the flowing gas, it was possible to graphically integrate the relation for the general case of radial flow of gases through the porous sand of gas wells. A chart has been prepared relating the value of the integral to the radius of the well bore and to the Reynolds number of the flowing gas. The chart actually performs the graphical integration and the solution of the formula is then reduced to a simple trial and error calculation. A typical back-pressure curve is calculated to show the transition from laminar to turbulent flow. This paper will briefly describe the pro-cedurcs for computing flow through porous media, including a method for predicting sand permeability from porosity and grain size and shape. Flow through Porous Media Brownell and Katzl recently reported a correlation for computing flow of fluids through porous media by the use of an enlarged Reynolds number and friction factor in which the porosity of the bed is included as an additional prime variable. The enlargcd Reynolds number com-

Jan 1, 1948

By Samuel Hoyt

THIS paper gives a brief description of an investigation made several years ago on the diffusion of zinc into copper. The material for that study was furnished in the form of thin copper strips coated with zinc. The result was required rather quickly and at not too great an expense, and especially information was desired as to the rate at which zinc would diffuse from the zinc coating into the copper and the temperature at which the operation should be carried out. A study of the requirements of this problem indicated that the solution might be secured by means of six determinations. This is the smallest number that will give the information desired and, at the same time, furnish checks on the accuracy of the determinations which justify an abbreviated experimental program. This does not count a preliminary test which was designed to give some idea of the correct temperature to use. The minimum number of temperatures that can be used is two. Knowing the rates of diffusion of zinc into copper at two properly chosen temperatures, it is possible to calculate the rate for any other temperature, and also to check the accuracy of the determination by means of the heat of diffusion, which is calculated from the effect of temperature on the rate of diffusion. The minimum number of determinations at any one temperature is three. The amount of diffusion which occurs at a fixed temperature is definitely related to the time of diffusion, so that by determining the amount of diffusion for three different time intervals, this relationship may be established and possibly a check on the accuracy may be secured. This accounts for the six determinations or experiments, and suggests the logical plan of the work. The check used here is not generally applicable to diffusion phenomena, but it seems to hold closely enough for the limited amount of diffusion in this investigation to justify its use.

Jan 1, 1928

By Junius D. Edwards

WHEN Charles Martin Hall invented the electrolytic process for the production of aluminum, one basic requirement was a supply of pure alumina. Now, more than 50 years later, the same requirement still holds, and there are no technical straws in the wind to indicate that this situation is likely to change. Long ago, Aluminum Company of America took a number of steps to see that this country should not face shortages of alumina and aluminum in time of emergency. As one step to this end, the Company developed and used a supply of bauxite in South America in order to conserve dwindling Arkansas reserves. Another, and more a program than a step, was to investigate every type of process that might bear the possibility of utilizing the low-grade ores of aluminum that are more plentiful than bauxite. It is a long story, but the investigation included electric-furnace processes, acid extraction processes and alkaline extraction processes, with or without preliminary furnace and sinter treatments. Some of the processes developed were operated in commercial production. This work has been continuous since the first World War. The turn of the wheel came sooner than was expected when, in 1942, bauxite shipments through the Caribbean became uncertain and hazardous through the operation of submarines. The tremendous requirements of aluminum for the war effort were consuming high-grade bauxite at an alarming rate and a national search for substitutes began. High-grade bauxites, for technical and economic reasons, have been defined as those containing about 7 per cent or less of silica. While bauxite of this grade was limited in amount in the United States, there was in sight a substantially greater volume of low-grade, high-silica bauxite not amenable to economic treatment by the Bayer process, but richer in alumina than the clays or other available low-grade ores. It was at this point, and after several years of intensive research on this particular phase of the problem, that Aluminum Research Laboratories brought to completion the invention of one of its research staff, which made practical the utilization of large reserves of low-grade bauxite in America. BAYER PROCESS The Bayer process has been almost universally used for the 'production of alumina from bauxite. This process, in outline, comprises the digestion of finely ground bauxite in a solution of caustic soda (NaOH) under pressure and at an elevated temperature. Alumina in the bauxite goes into solution as sodium aluminate and the impurities-oxides of iron, titanium and silicon-remain undissolved. The undissolved residue, known as "red mud," from its color, is separated and run to waste. Aluminum hydrate (A1202.3H20) is precipitated from the solution of sodium aluminate, and the liquor containing the caustic soda and some alumina is returned to the process for digesting more bauxite. The aluminum hydrate, after washing, is calcined at a high temperature to produce

Jan 1, 1945

By Charles F. King

The only investigations on record of the reactions occurring (luring the Bessemer blow are of charges containing a large percentage of manganese, with the exception of' two partial analyses by Snelus and Barker of the English method, where a low percentage of manganese was used. They do not give the analysis of the spiegel, [lor do they report any graphitic carbon after the first stage of the process. Both report only traces of manganese after the first stage until the addition of spiegel. The slags corresponding to the samples of metal were not analyzed.

Jan 1, 1881

By B. C. Wonsiewicz, W. W. Wilkening

Following a procedure proposed by Wheeler and Ireland, Plane stress yield loci were constructed from Knoob hardness numbers. Basically, six differently oriented hardness measurements were made on three orthogml surfaces through pure poly crystalline magnesium sheet, a magnesium single crystal, and sheet of the magnesium alloys: Mg + 0.5 pct Th, Mg + 4 pct Li, AZ31B, and EKOO. Hardness loci were found to be in poor agreement at small strains (E < 0.05) with loci established by a more rigorous technique. At larger strains (E - 0.10) the agreement is fair, but at this stage in deformation the conventional locus has lost much of the asymmetry that characterizes these anisotropic materials. Two effects which will lead to distortions in the Khn locus are discussed with reference to the geometry of plastic flow during a hardness test. DETERMINING a material&apos;s resistance to multiaxial loading is of interest not only from a structural design viewpoint but also from that of deformation processing. Unfortunately, the determination of the yield locus, although simple in principle, involves tedious procedures if the results are to be at all rigorous.&apos; The idea, first proposed by Wheeler and 1reland2 of determining the yield locus by means of six Knoop hardness impressions along the principal directions in a material has obvious appeal. It is simple, quick, and should be applicable to very thin sheets. If such a technique could be demonstrated to produce consistently reliable results, it would be of interest to both researcher and designer. Lee, Jabara, and ackofen have compared the yield locus determined by Knoop hardness measurements (the Khn locus) to a locus determined by more rigorous techniques. They found good agreement for two titanium alloys at a plastic strain of about 1 pct. The purpose of this paper is to investigate if the Khn locus construction is a reasonable approximation to the locus of a highly anisotropic material. Examples of such materials are magnesium and magnesium alloys which have severely distorted yield loci which in turn reflect markedly dfferent yield strength in different directions.&apos; In pure magnesium, for example, the yield stress in tension along the transverse direction may be four times the yield stress in compression in the same direction and twice the tensile yield stress in the rolling direction. Predicting such large differences ought to serve as a severe test of the Khn locus construction. EXPERIMENTAL PROCEDURES Samples of rolled sheet, 0.250 in. (6.35 mm) thick, of pure magnesium and four magnesium alloys (Mg experimental materials. The pure magnesium together with the lithium and thorium alloys were those used in the study of Kelley and Hosford. The grain size was ASTM number 4 for the pure magnesium and number 6 for the alloys. HARDNESS TESTING The materials were sectioned along the rolling and transverse planes, mounted in a quick setting resin, and mechanically polished. Most of the hardness tests were performed on a surface prepared by electro-polishing (30 pct nitric acid in methanol at 0°C and 20 v) with the exception of the AZ31B and EK00 alloys which were made directly on a metallographically polished surface. However, subsequent hardness tests on the same sample after heavily electropolishing, revealed essentially the same hardness as before. At least twenty Knoop hardness impressions under a 100-g load were made in each of the six orientations shown in Fig. 1. The average hardness number and standard deviation were then calculated for each orientation. CONVENTIONAL LOCUS CONSTRUCTION Yield loci were constructed using a technique described in detail by Lee and ackofen,&apos; in which the flow stress (stress at a given plastic strain) fixes the coordinates of a point on the locus and measurements of the strain ratio serve to establish the slope of the locus at that point. The loading paths which correspond to uniaxial tension or compression tests establish the four intercepts of the locus with the coordinate axes plus one point on the balanced biaxial tension line Tensile testing was performed along the rolling and transverse (r, t) directions. Samples had a uniform rectangular gage length 1 by 4 by 4 in. (25.4 by 6.35 by 6.35 mm) and were deformed at a strain rate of 3.33 x 104 sec-&apos;. The tests were interrupted periodically to unload the sample and measure the plastic strains by means of X-Y post yield strain gages. Compression tests in the rolling, transverse, and through-thickness (r, f, z) directions were performed on 1/4 in. (6.35 mm) cubes at an initial strain rate of 8.33 x sec-&apos;. Lubrication was provided by 0.002 in. (51 pm) Teflon sheet which was renewed after unloading for micrometer measurements used to calculate the strains.

Jan 1, 1970

By William P. Shinn

Jan 1, 1881

By Felix A. Vogel

I (New York Meeting, February, 1912.) FLUE-DUST, to most blast-furnace operators, means a troublesome by-product, the formation of which should be curtailed, if not prevented entirely. However, with the increasing use of fine ores, larger furnaces, and high-pressure blast, the production of flue-dust is constantly increasing, and amounts annually in the United States to from 3,000,000 to 3,500,000 tons, An exceedingly high tonnage, of which a large part has been discarded as valueless. As a result of greater economy in the iron industry, the attention of our furnace-men has been directed towards the utilization of this enormous amount of waste material, a problem which had also been given due consideration by metallurgists abroad. Flue-dust is generally a fine material containing considerable coke and iron-ore, with a small admixture of lime and silica, depending upon the burden. The iron-ore is partly reduced, which shows that the dust originates largely in the reducing-zone of the blast-furnace. In the United States this dust usually contains 20 per cent. of coke and more than 40 per cent. of iron. Estimating coke to be worth $3.25 per ton, and iron-ore 7 cents per unit, a ton of flue-dust, unless made available, represents a loss to the furnace-man of $3.50. This accounts for the first efforts to recharge the flue-dust into the furnace, either by moistening it clown with an excess of water, or mixing it with clay to form balls of pulp, or treating it with lime-water. These methods, however, have been practically discarded, as they failed to produce the desired economies. To recover, in the blast-furnace, all the values represented by the material contained in the flue-dust, the following con¬ditions should be complied with

May 1, 1912

By William P. Shinn

IT seems proper to present in the Transactions of the Institute, from time to time, formal record of the advances made in the arts and sciences to which our organization is devoted-milestones in the highway of progress-from which our successors may measure what they in their turn have gained. The admirable address of the Hon. Abram S. Hewitt, then president elect of the Institute, on "A Century of Mining and Metallurgy in the United States," read at the opening of the meeting held in this hall in June, 1876, forms a point of departure, and the conclusion of the eighth decade of the nineteenth century and the end of the first five years of our country&apos;s second century seem to offer a fitting time for again making up our record. The period since 1875 has been marked by a degree of activity in mining and metallurgical industry never before equalled in our history, while the progress made in the science and art has been, if possible, still more noticeable. Whether we consider the mining of iron, ore, and coal, or of the precious metals,-the advances made in smelting the former and in reducing the latter, the extraordinary increase in the production of Bessemer steel, or the science of Thomas and. Gilchrist, which makes the hitherto rejected phosphorus the corner-stone of success,-the past five years are alike memorable for the progress they have shown and to some of the most marked features of this progress I will now oriefly call your attention. It may be of interest in this connection to note the following figures, showing the growth of the population of the United-States during the last three decades :

Jan 1, 1881

For the benefit of those of our members who are considerable holder; of securities, but owing to their isolated situations are not in close touch with the metropolitan market and current quotations, we are publishing two very interesting graphs, showing the course of the bond and stock markets in New York over a long period. These graphs are-fui?riished through the courtesy of the financial department of the New York Tribune.

Jan 8, 1919

By Joseph Richards

THERE are two essentially different types of case-hardening processes; that using a dry mixture in which the object to be case-hardened is packed and kept for the necessary time at the necessary temperature, and the "liquid" process, employing a bath of fused, salts into which the object- is immersed and which by immediate contact case-hardens the surface of the article. The Shimer process belongs to the second class, and was a war emergency invention. Of the liquid melts used as baths, the most effective and most fre¬quently used are melted potassium cyanide and melted sodium cyanide. These may be used either pure, or mixed with salts that reduce the melting point and the percentage of cyanide present. The use of these baths since 1914 has met many commercial difficulties because of the high price and frequent commercial scarcity of the cyanide salts; at present sodium cyanide has practically entirely displaced potassium cyanide. Another trouble is the danger to the workmen handling the cyanide salts, which are extremely poisonous, and the annoying and poisonous vapors or gases given off in the workshop, unless an effective system of hoods and ventilation is provided, so as to prevent the gases from the baths mixing with the air of the room. Porter W. Shimer, of Easton, Pa., has invented a substitute for the bath of melted cyanides which case-hardens with equal or greater facility and effectiveness, gives off no poisonous vapors, and costs for chemicals materially less than the cyanide costs in the previously used baths. The process has been in use over a year in a large American works and the following statement embodies the results of practical experience in the use and operation of the process. The Shinier liquid or melted bath consists of a mixture of easily fusible salts that do not possess case-hardening properties, into which is immersed fresh calcium cyanamide, which imparts to the bath case-hardening properties. The composition of the non-case-hardening-,salts appears rather immaterial. Good results have been obtained by using a mixture of sodium chloride, calcium chloride, and barium chloride in

Jan 2, 1919

By W. L. Remick

WHEN the senior author of this paper presented an article on Fine Coal Cleaning by the Hydrotator Process,1 at the February, 1927, meeting, that process had been developed in the anthracite region only to clean what is known as "slush" or "silt." This size constitutes all of the material passing the finest screen used at any particular colliery. Some use a 3/32 -in. round-hole screen and others use a 1/16 -in. round hole. Practice varies throughout the anthracite region, but the tendency seems to be toward the finer screen.

Jan 1, 1929