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By Joseph W. Leonard

Seven formulas commonly used to evaluate industrial screening efficiency are investigated to determine if they are suitable for calculating the efficiency of rectangular-hole screens. Six formulas were found to be limited in application to square-hole screens. The seventh, although acceptable for evaluating rectangular-hole as well as square-hole screening efficiency, was found to be unwieldy. A new formula is developed based on the concept of misplaced sizes. This proposed formula permits the single step determination of efficiency and is applicable to all types of screening applications.

Jan 1, 1975

By Eugene Guccione

Before answering the question raised in the title, let's briefly consider how East-West trade is viewed within the entire US political spectrum. Essentially, there are four major schools of thought: (1) The Peaceful-Coexistence School. Advocates of this school call themselves free-traders and hold to the premise that: (a) trade benefits all parties involved, hence it is the best tool to achieve peace; (b) US trade barriers should be removed, and the quicker the better; and (c) negotiations, cultural exchanges, and political compromise should be used extensively.

Jan 9, 1974

By O. L. Kowalke

THE measurement and control of temperatures have assumed positions of great importance in many industries. The manufacturers of byproduct coke and carbureted water gas find that proper temperature control helps to produce a better product and economizes in the use of raw materials. In the manufacture of glass, enameled ware, brass, and high-temperature refractories, temperature control is now regarded as being coordinate in importance with the control of materials used. To control such processes as malleablizing cast iron, and hardening, tempering, and annealing of steel in a manner to meet exacting market requirements has, within recent years, involved the installation of large and expensive pyrometer equipments. In many of these installations, it was necessary not merely to measure but also to record the temperatures over a period of time and thus obtain a record of the entire heat treatment and an effective check on the workmen in charge. In view of the importance of temperature measurement and control in such a wide variety of industries and the necessity for proper supervision of the installation and operation of the outfits, the following questions may be pertinent: What instruction is offered by the engineering colleges and what departments in the colleges are responsible therefor? The latest available catalogs of ten prominent engineering colleges east of the Mississippi River showed courses in high-temperature measurements given by the departments of physics. These courses, in general, were described as comprising classroom and laboratory instruction in the theory of high-temperature measurements, together with exercises in the calibration of the various devices used. In some cases it was stated that consideration would be given, in the courses, to the practical applications in the industries. In only one. college was the course required of all engineering students; in most colleges it was optional; in a few colleges, it was required only of certain groups. In colleges offering a course in metallurgical engineering, instruction in pyrometry was always given in connection with metallurgical laboratory work. The students in ceramic,

Jan 8, 1919

By Charles Maier

IT has long been supposed that when crystalline materials are com-minuted the energy used in the production of increasingly smaller grain sizes is not entirely dissipated as heat but that a certain portion is "stored" as a part of the internal energy of the material. This portion usually has been called the "surface energy" of the particles. The practical interest of the Bureau of Mines in this subject in connection with the energy requirements of crushing processes has led to the author's attempt to measure the "stored" energy in finely divided calcite by heat-of-solution methods1. The experiments on calcite showed that "storage" of energy could not be proved for this material, because fine grinding caused a lack of chem-ical homogeneity evidenced by loss of carbon dioxide and subsequent adsorption of water on the surfaces of the calcite particles. When thermochemical correction was made for composition changes the cor-rected heat of solution was less for fine material than for coarse. Con-tinuation of the experimental work into the problem of comparing work and heat in the deformation of metallic crystals, where the calorimetric difficulties were less, showed, however, that in the case of copper and aluminum a real discrepancy between work and heat could be shown. similar results had previously been obtained by Farren and Taylor2 and Hort3 and more or less simultaneously with the author's work by

Jan 1, 1936

THE third annual Joint Western Mining Convention, held at Los Angeles, Sept. 10 to 13 inclusive, was a notable success both as to attendance and interest. Registration the first day amounted to 201, and the total crept up to 347 before the close. The American Institute of Mining Engineers was well represented, approximately 80% of those registered and most of the speakers being members. This illustrates largely the amount of interlocking membership and the reason for holding at one time and place meetings of the several related organizations. The plan has proved so successful that it is probable that Spokane will extend an invitation for next year that seems likely to be accepted. It is proposed that the convention be timed so as to permit visitors from the East to stop there Oct. 3 to 5, en route to the American Institute of Mining Engineers meeting at San Francisco, Oct. 7 to 9. Simultaneously, it is expected that the Petroleum Division will hold its fall session at Los Angeles, the two streams of travel meeting in San Francisco, just before departure of the party of engineers traveling to Japan to attend the World's Engineering Congress. The Los Angeles meeting opened Monday morning with a general session under the auspices of the Western Division of the American Mining Congress with Philip Wiseman in the chair. After a series of short responses to the welcome extended, Charles W. Merrill discussed the needs of the western mining industry. A complimentary luncheon to members and delegates followed.

Jan 1, 1928

By Robert W. Zimmerman

POROUS SOLID COMPRESSIBILITIES There are four different compressibilities associated with porous solids, each relating the fractional change in either bulk volume or pore volume with the change in either pore pressure or confining pressure. These will be referred to as Cbc, Cbp, Cpc, and Cpp, with the first subscript denoting the relevant volume, and the second subscript denoting the relevant pressure. They are defined as: [ ] Note that minus signs are included in two of the definitions so that each of the compressibilities will always have a positive value. In general, each compressibility depends on the elastic moduli of the matrix material, the porosity, and the exact geometry of the pores. Taking the latter factor into account calls for separate analysis for each different pore shape, which of course can only be attempted for a few relatively simple cases. But lower bounds for each of the four compressibilities can be found, independant of pore structure, in terms of only the porosity (0) and the elastic moduli of the matrix material (any pair chosen from K, E, G and V). The first step is to find relationships between the four compressibilities, starting with the following observation: If a porous solid made of a linear elastic, isotropic and homogeneous matrix material is subjected to uniform hydrostatic pressure of magnitude P on its external and all of its internal (pore) surfaces, the state of stress in the solid will be exactly the same as that which would occur

Jan 1, 1982

By E. P. Abrahamson

The effect of transition element binary solid solution additions upon the recrystallization temperature of titanium has been investigated. All additions, except columbium and tungsten, raised the recrystallization temperature. A correlation is obtained between the logarithm of the absolute rate of change of recrystallization temperature with atomic percent solute and the number of uuter d shell electrons attributed to the free atom of the solute element in its ground state. The work of Abrahamson, et aL.1-6 on dilute binary solid solution alloys indicated a correlation between the free atom ground state electron configuration of the solute and both the brittle-ductile transition and recrystallization temperature. It is shown in these studies that the number of outer s and d electrons in the solute are of prime importance in determining the absolute rate of change of recrystallization or transition temperature with composition. Furthermore, the limit of initial linearity (in the curve of recrystallization temperature vs at. pct solute) has been shown to be a function of the number of d shell electrons in the solute for dilute iron- and vanadium-base alloys. To date no complete systematic recrystallization study of dilute binary titanium base alloys has been made. This study together with that of zirconium base alloys 6 will provide the data for the comparison of the effect of the same solutes upon two solvents with the same number of outer d shell electrons.

Jan 1, 1962

By J. R. Coulter, F. O. Case, H. G. Satterthwaite, B. Harden

During the two years that the Henderson plant has been in operation, a number of technical improvements have been made by the staff of Basic Magnesium, Inc., the effects of which were realized subsequent to the writing of the paper by Major C. J. P. Ball (p. 28j, this volume). Pellet Mix The process as originally installed required the use of peat moss in the mixture going to the chlorinators. This had to be imported from Canada at a considerable cost, and, besides being expensive, constituted a serious fire hazard in the dry climate of Nevada. Experimentation looking toward its elimination had been going on for some time and was actively pushed as soon as operations commenced. It was found that a pellet mix containing no peat, which would chlorinate at a satisfactory rate, could be cast as a fluid slurry, which would set up into a hard mass having the desired porosity. For carrying out this operation, equipment similar to that used in the manufacture of phosphate fertilizer at Anaconda, Mont., was installed and proved eminently successful. The dry materials, with peat moss and raw concentrates entirely eliminated, are mixed with magnesium chloride solution in two Pratt phosphate mixers and the resultant slurry is poured onto two 48-in. slowly moving rubber conveyor belts. By the time the slurry has reached the head pulley, the material has set su4iciently to be broken and sized as desired. The discharge from the casting belts is fed to the four rotary kilns in the preparation plant, where it is dried and coked to the proper degree for subsequent chlorination. With the peatless feed the capacity of the kilns was found to be about double what it had been before, so that the four rotaries suffice for a 10-unit operation, thus making it unnecessary to operate the extruders and tunnel kilns. In addition to saving the cost of the peat, the new system can be operated with about 85 per cent less labor than was formerly required in the preparation plant. The new pellet production system has also made it feasible to install centralized crushing equipment with suitable conveyors and a loading station. Containers of 8000 lb. capacity were substituted for small cubicles of 1000 lb. capacity which formerly were used for charging the chlorinators, and trailer trucks were substituted for the small trains originally provided for transportation from the preparation plant to the chlorinators. These changes resulted in a considerable saving in handling and transportation charges. Handling Molten Metal The molten magnesium originally was ladled from the electrolytic cells into small gas-fired brick-lined cars standing between the cell rows. From these cars the metal nes ium. into ''cheeses'' weighing from 150 to 300 lb. After solidification the

Jan 1, 1944

By Martin J. Conway

DURING the past year, the intense interest shown by the metallurgical industry in the use of relatively pure oxygen has been evidenced by the number of papers dealing with its application and production. The reason for this interest is apparent when it is realized that, weight for weight, oxygen enters into the formation of steel equally with iron. In the manufacture of steel, approximately one ton of oxygen is required to produce one ton of ingots. Until the recent development of plants capable of producing oxygen at far lower costs than had ever previously been considered possible, the oxygen required for steel manufacture was used as it occurs in air, where it is associated with approximately four times its volume of nitrogen. Because of the diluent nitrogen more than 4 tons of total gaseous material per ton of steel must be handled rather than only approximately one ton required when pure oxygen is used. In addition, provision must be made to handle the large quantity of waste, gases resulting from the process. There are cases where the reduction in gas volume alone can justify the installation of an oxygen plant.

Jan 1, 1947

By Frederick Rhines

THE investigations of Wyman1 have demonstrated that copper deoxidized with several of the commonly used agents that confer immunity to ordinary hydrogen em-brittlement can still be embrittled if it is annealed alternately under oxidizing and reducing conditions. During the oxidizing cycle, oxygen diffuses into the copper and frequently deposits a subscale composed of the oxide of the residual deoxidizing agent. Upon subsequent reduction with hot hydro-gen, the copper becomes ruptured along the grain boundaries to a depth sharply limited by the previous penetration of oxy-gen as delineated by the inner boundary of the subscale. Obviously the sensitivity to this kind of hydrogen embrittlement is engendered by the introduction of oxygen during the oxi-dizing anneal, but beyond this the mecha-nism of the process, and hence the controlling factors, remain obscure. There are several possibilities: (I) oxygen dissolved in the copper matrix of the subscale may, upon cooling prior to the hydrogen anneal, precipitate as cuprous oxide which is subse-quently reduced by hydrogen as in the familiar case of hydrogen embrittlement; (2) oxygen in solid solution in copper may itself confer susceptibility to embrittlement by hydrogen; (3) the normally refractory oxides such as those of aluminum, silicon and titanium may themselves he reduced by hydrogen when in contact with copper; or (4) the precipitated oxides of the sub-scale may be complex compounds such, perhaps, as Si02-Cu20, which are partially reduced by hydrogen. These possibilities have been examined, and it has been con-cluded that the first three and possibly the fourth are operative collectively or indi-vidually under more or less predictable conditions.

Jan 1, 1940

By Robert C. Linares

Cubic zinc sulfide has been grown from molten salt solutions substantially below the hexagonal-cubic phase transition of 1020°C. Crystals free of birefringence have been grown from molten lead chloride at temperatures from 500° to 800°C. Factors affecting the optical transmission and the birefringence are discussed. CUBIC zinc sulfide is of interest for electrooptic devices and as an optical coating material. However, it cannot readily be produced as large crystals which are free of birefringence. The birefringence arises from the fact that the cubic ZnS is usually grown as the high-temperature hexagonal phase and is transformed to the lower cubic phase by annealing.' This results in stacking faults, stress, and birefringence. A requirement for the growth of cubic ZnS is that it be grown below the phase transition of 1020°C.2 Crystals of cubic ZnS have been grown below 1020°C by the hydrothermal,3 flux,4 and vapor transport5 techniques. However, these all appear to have limitations in size or quality of material produced. It was felt that a new flux method might have a good chance of overcoming some of the previous problems. Mita6 reported the growth of hexagonal ZnS from molten NaCl and wilke7 reported the growth of iron sulfides from molten lead chloride solution, indicating that molten chlorides make good solvents for sulfides. An investigation of a number of possible molten chlorides as solvents showed that molten PbCl2 has an appreciable solubility for zinc sulfide and that crystals can be grown at temperatures from 500° to 800°C. EXPERIMENTAL Crystal growth was performed in open or sealed Vycor or fused silica tubes, in an argon atmosphere or vacuum. There were no deleterious effects due to using vacuum; however, a sealed essentially isothermal system must be used to prevent vapor transport mechanisms from dominating. This will be discussed later in detail. Noble metal containers were not usable as they were severely attacked by these melts. The materials used were: reagent-grade PbC12, reagent-grade ZnS, optical-coating-grade ZnS, and Irtran 2 (ZnS). Crystal growth was accomplished by both slow cooling techniques and gradient growth techniques. In the slow cooling techniques, 15 g of ZnS and 100 g of PbCl2 were used. The components were placed in the silica tube, heated at 800°C for 2 hr, and then slowly cooled (l° to 10° C per hr) to 500°C. The furnace was constructed so that the tube could be inverted, thus allowing the liquid to drain off the crystals at the end of the run. The gradient runs were made by placing the above mixtures in a silica tube at 550° to 600°c, Fig. 1. A temperature gradient was maintained such that the floating mass of undissolved sulfide was 10° to 50°C warmer than the bottom of the tube. Growth occurred on spontaneously nucleated sites at the cooler bottom. RESULTS When using high cooling rates (5° to 10°C per hr), crystals form in thin sheets perpendicular to the {111} face. Crystals 5 by 5 by 1.2 mm, Fig. 2, have been ob-

Jan 1, 1969

By John R. Freeman

This paper relates entirely to the casting of brass under fluid pressure in steel dies. Die castings of metals and alloys of low melting point have been available for many years but the development of brass die castings has been relatively recent, occurring within the past five years. The successful developnlent of brass die castings has resulted from the availability of alloy steels that would give satisfactory life as dies and the development of suitablc die-casting machines. The melting point of copper is 1084" C. (1983" F.) and of a high brass about 900" C. (1652" F.), as compared to 327.5" C. (621.5" F.) for lead, 419.4' C. (786.7" F.) for zinc and 658.7" C. (1217.7" F.) for aluminum, temperatures that are indicative of the casting temperatures required for the various types of alloys, of which the melting points are somewhat lower than those of the pure metals. Type of Die-casting Machine In the well-known plunger and gooseneck types of die-casting machines used for casting the alloys of relatively lower melting point, much of the working mechanism is immersed in the molten alloy. For alloys having the relatively high melting point of brass, this obviously is impossible. Machines with a separate melting chamber are essential. Two rather distinct types are in extensive use at the present time, the Pack and Polak machines, the former designed by Charles Pack and developed at the American Brass Co., the latter developed by Joseph Polak, of Prague, Czeclioslovakia. The principles of operation of these machines have been described in articles by Pack1,2,3 and by Sieg.4

Jan 1, 1935

By John R. Freeman

This paper relates entirely to the casting of brass under fluid pressure in steel dies. Die castings of metals and alloys of low melting point have been available for many years but the development of brass die castings has been relatively recent, occurring within the past five years. The successful developnlent of brass die castings has resulted from the availability of alloy steels that would give satisfactory life as dies and the development of suitablc die-casting machines. The melting point of copper is 1084" C. (1983" F.) and of a high brass about 900" C. (1652" F.), as compared to 327.5" C. (621.5" F.) for lead, 419.4' C. (786.7" F.) for zinc and 658.7" C. (1217.7" F.) for aluminum, temperatures that are indicative of the casting temperatures required for the various types of alloys, of which the melting points are somewhat lower than those of the pure metals. Type of Die-casting Machine In the well-known plunger and gooseneck types of die-casting machines used for casting the alloys of relatively lower melting point, much of the working mechanism is immersed in the molten alloy. For alloys having the relatively high melting point of brass, this obviously is impossible. Machines with a separate melting chamber are essential. Two rather distinct types are in extensive use at the present time, the Pack and Polak machines, the former designed by Charles Pack and developed at the American Brass Co., the latter developed by Joseph Polak, of Prague, Czeclioslovakia. The principles of operation of these machines have been described in articles by Pack1,2,3 and by Sieg.4

Jan 1, 1935

By John R. Freeman

THIS paper relates entirely to the casting of brass under fluid pressure in steel dies Die castings of metals and alloys of low melting point have been available for many years but the development of brass die castings has been relatively recent, occurring within the past five years The successful development of brass die castings has resulted from the availability of alloy steels that would give satisfactory life as dies and the development of suitable die-casting machines The melting point of copper is 1084° C (1983° F ) and of a high brass about 900° C (1652° F ), as compared to 327 5° C (6215 °F) for lead, 419 4° C (786 7° F) for zinc and 658 7° C (1217 7° F) for aluminum, temperatures that ale indicative of the casting temperatures required for the various types of alloys, of which the melting points are somewhat lower than those of the pure metals TYPE OF DIE-CASTING MACHINE In the well-known plunger and gooseneck types of die-casting machines used for casting the alloys of relatively lower melting point, much of the working mechanism is immersed in the molten alloy For alloys having the relatively high melting point of brass, this obviously is impossible Machines with a separate melting chamber are essential Two rather distinct types are in extensive use at the present time, the Pack and Polak machines, the former designed by Charles Pack and developed at the American Brass Co , the latter developed by Zoseph Polak, of Prague, Czechoslovakia The principles of operation of these machines have been described in articles by Pack1,2,3 and by Sieg 4

Jan 1, 1935

By E. S. Bardwell

Each of the three refining furnaces in use at Great Falls is provided with a waste-heat boiler. The general arrangement of furnace and boiler is as shown in Fig. 1. Two of the furnaces have hearths 45 ft. 7 in. by 14 ft. 6 in.; the third has a hearth 46 ft. 101/2 in. long and of the same width as the other two. The furnaces at present are equipped for firing with natural gas. As originally constructed two of the furnaces had hearths 36 by 14 ft., and were designed to use coal on grates, but these furnaces were lengthened and fired successively with pulverized coal and oil. The third furnace was added in 1926 and was oil-fired until 1928. Since that year natural gas has been in use on all of the furnaces. The changes that have occurred in connection with furnace design and the comparative performance of the furnaces with various fuels were described1 by the author in 1932. Two of the furnaces are provided with Stirling class A-30 boiler. rated at 400 hp. and having 4008 sq. ft. of heating surface. The thir furnace has a class A-21 Stirling waste-heat boiler rated at 300 hp. with 2805 sq. ft. of heating surface. The boilers are not baffled. The waste-heat boilers are placed on a platform 17 ft. 3 in. above the level of the furnace charge floor. The waste gases from the furnace pass by a vertical uptake flue, 4 by 3 ft. inside at the point where it enters the chamber, to a brick chamber from which the gases pass over a bridge wall and into the boiler setting. The uptake flue and chamber are constructed of silica brick. Each furnace has a steel stack 125 ft. high, measured from the boiler floor. The stacks have a 41/2-in. firebrick lining and are 5 ft. in diameter

Jan 1, 1934

By Cyril Stanley Smith

Somewhat over ten years ago the author described studies1'2 on the constitution of the copper-silicon system. The copper-rich portion of this diagram is shown in Fig. 1. The experimental points freely dotted about the diagram seemed to justify an otherwise unconvincing diagram and for several years the curious reverse bend in the alpha-phase boundary was accepted as substantially correct, even by later investigators3 of the system who introduced changes in the high-silicon phases. The binary diagram has been used as a base for several ternary systems5-9 without any suggested changes. Voce10 suspected the existence of another phase from his study of the cast alloys in the copper-manganese-silicon system, but evidently hesitated to extrapolate this to the binary diagram, particularly in view of the too ingenious explanation that was advanced1' to account for the pools of constituent clearly visible in castings; namely, that they were secondary alpha of twinned orientation deposited from beta. Von Schwarz,12 in 1932, called attention to the fact that this micro-constituent in copper-silicon alloy castings was anisotropic under polarized light and asserted that a new phase, not cubic, should be placed in the diagram .adjacent to alpha. Sautner,l3 on the basis of investigations with the polarizing microscope and with X-rays, introduced this phase into the diagram at about 6 per cent Si. The relevant part of his diagram is shown in Fig. 2. Sautner called the new phase beta, renaming the old beta phase zeta. To avoid confusion, in redrawing Fig. 2 the phases have been renamed in accordance with the terminology adopted in the present paper, in which the new phase is called kappa and the other phases retain the designation given them by Arrhenius and Westgren.4 The thermodynamic impossibility of Sautner's diagram and the paucity of experimental data left the exact location of the new phase field most uncertain, although his work proved beyond doubt that an additional noncubic phase exists. Because of the industrial importance

Jan 1, 1940

By Cyril Stanley Smith

Somewhat over ten years ago the author described studies1'2 on the constitution of the copper-silicon system. The copper-rich portion of this diagram is shown in Fig. 1. The experimental points freely dotted about the diagram seemed to justify an otherwise unconvincing diagram and for several years the curious reverse bend in the alpha-phase boundary was accepted as substantially correct, even by later investigators3 of the system who introduced changes in the high-silicon phases. The binary diagram has been used as a base for several ternary systems5-9 without any suggested changes. Voce10 suspected the existence of another phase from his study of the cast alloys in the copper-manganese-silicon system, but evidently hesitated to extrapolate this to the binary diagram, particularly in view of the too ingenious explanation that was advanced1' to account for the pools of constituent clearly visible in castings; namely, that they were secondary alpha of twinned orientation deposited from beta. Von Schwarz,12 in 1932, called attention to the fact that this micro-constituent in copper-silicon alloy castings was anisotropic under polarized light and asserted that a new phase, not cubic, should be placed in the diagram .adjacent to alpha. Sautner,l3 on the basis of investigations with the polarizing microscope and with X-rays, introduced this phase into the diagram at about 6 per cent Si. The relevant part of his diagram is shown in Fig. 2. Sautner called the new phase beta, renaming the old beta phase zeta. To avoid confusion, in redrawing Fig. 2 the phases have been renamed in accordance with the terminology adopted in the present paper, in which the new phase is called kappa and the other phases retain the designation given them by Arrhenius and Westgren.4 The thermodynamic impossibility of Sautner's diagram and the paucity of experimental data left the exact location of the new phase field most uncertain, although his work proved beyond doubt that an additional noncubic phase exists. Because of the industrial importance

Jan 1, 1940

By Donald O. Rausch, Robert H. Merrill

12.1 -1. Introduction. Problems concerning slopes in soils and rock generally arise in connection with road cuts and open pit mines. The angle at which a slope will safely stand is of major economic importance to both the road designer and the open pit operator. Stable slopes in soils and rock are evaluated through two fundamental approaches, namely, soil mechanics and rock mechanics. The approach selected to make this evaluation depends upon the material in the slope. For the purposes of this chapter, only slopes totally in soil or totally in rock are considered. By definition, soils are unconsolidated accumulations of solid materials produced by mechanical and chemical disintegration of rocks or the accumulation of sediments (28); rock is defined as the hard, compact, natural materials composing the crust of the earth (10). The basic factors affecting slopes in soil or rock are similar, although rock strengths are orders of magnitude greater than soil strengths. In general, the strength of large masses of soil depends upon the texture of the soil, the particle size, cohesion, and resistance to tensile and shear stress; the strength of large masses of rock depends upon the strength of the rock and the defects, such as faults, fractures or joints, that intersect the rock. Further, some of the defects in rock are cemented or uncemented, and may be filled with materials that are strong or weak compared to the rock. In slopes of either soils or rock, the stability is presumed to be a function of the slope height, slope angle, the size of the excavation, and the stresses imposed on the soil or rock by tectonic and/or gravity forces, earthquakes, or other static or dynamic forces. In addition, both soil and rock slopes are affected by static and dynamic water pressures in the pores of soils or permeable rocks or in the defects in the rock behind the slope. Visual observations of slope failures also indicate that both soil and rock can deteriorate with time, and this deterioration may be caused primarily by weathering (27).

Jan 1, 1968

By W. P. Frey

The briquet plant of the Lehigh Coal and Navigation Co., at Lansford, Pa., has previously been referred to.' It has passed the stage of experiment and now rests on a foundation practically and financially sound. The purpose of this' paper is to explain how success has been attained, and to set standards for the development of hard-coal briquetting which may eliminate future failures. All the conclusions are based on actual results, avoiding speculation and theory. Up to three years ago, the L. C. & N. Co. used coal-tar pitch as a binder in making hard-coal briquets. The plant operated with a monthly output of 300 to 600 tons and was unable to meet its own expenses. Naturally, no one was satisfied, especially as the ideals of a smokeless briquet were still unrealized. Then came the Dutch oil process, introduced in this country by the General Briquetting Co. of New York. This process uses as binder a small percentage of heavy residue of petroleum, which, being liquid, permits great economy of handling; it also did away with the most objectionable fumes of the former briquets. This oil2 is not absolutely smokeless; heating the fresh fuel to red heat liberates some low-volatile hydrocarbons, yielding a white smoke which is not objectionable. On the other hand, this oil adds to the briquet about 7 per cent. of volatile matter, giving the product a heating capacity equal to that of the best free-burning anthracite coal. The average silt used in the manufacture of these boulets averages 16.5 per cent. chemical ash, corresponding to 12,000 B.t.u. per pound of coal. The Hydrolene used as binder runs about 17,500 B.t.u. per pound, and approximately 7 per cent. of it enters into the mixture, hence 12,000 X 0.93..........................11,160 B.t.n. 17,500 X 0.07.......................... 1,125 B.t.u. Total.....................................12,385 B.t.u. per pound of briquets

Jan 1, 1918

By W. P. Frey

THE briquet plant of the Lehigh Coal and Navigation Co., at Lansford, Pa., has previously been referred to.1 It has passed. the stage of experiment and now rests,, on a foundation practically and financially sound. The purpose of this paper is to explain how success has been attained, and to set standards for the development of hard-coal briquetting which may eliminate future failures. All the conclusions are based on actual results, avoiding speculation and theory. Up to three years ago, the L. C. & N. Co. used coal-tar pitch as a binder in making hard-coal briquets. The plant operated with a monthly output of 300 to 600 tons and was unable to meet its own expenses. Naturally, no one was satisfied, especially as the ideals of a smokeless briquet were still unrealized. Then came the Dutch oil process, introduced in this country by the General Briquetting Co. of New York. This process uses as binder a small percentage of heavy residue of petroleum, which, being liquid, permits great economy of handling; it also did away with the most objectionable fumes of the former briquets. This oil2 is not absolutely smokeless; heating the fresh fuel to red heat liberates some low-volatile hydrocarbons, yielding a white smoke which is not objectionable. On the other hand, this oil adds to the briquet about 7 per cent. of volatile matter, giving the product a heating capacity equal to that of the best free-burning anthracite coal. The average silt used in the manufacture of these boulets averages 16.5 per cent. chemical ash, corresponding to 12,000 B.t.u. per pound of coal. The Hydrolene used as binder runs about 17,500 B.t.u. per pound, and approximately 7 per cent. of it enters into the mixture, hence 12,000 X 0.93 11,160 B.t.u. 17,500 X 0.07 1,125 B.t.u. Total 12,355 B.t.u. per pound of briquets

Jan 1, 1918