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By Henry E. Wood

In my opinion, the concentration of minerals by flotation is the most interesting problem in ore-dressing, and will command eventually far more consideration than it has at present. For many ores it furnishes a complete method of concentration absolutely independent of specific gravity, and thus simplifies the milling of many difficult combinations. Not having to recognize the influence of specific gravity, we are also able to dispense with some of the complications resulting from classifying-conditions. Where flotation cannot be used for a complete separation of the minerals from the gangue, it will be found, in nearly all cases, to save those portions which are generally lost by reason of their fine state of division. For this reason, it should be looked upon mainly as an aid to general concentration, although there are many ores so well adapted to flotation that more than 90 per cent. of the valuable metals can be recovered from them in one operation by this process. In presenting the results of my investigations in flotation, I have endeavored to theorize as little as possible. That side of the subject has been extensively discussed by others. My earliest work with flotation was done in 1895, when I used various oils, grease, soap, etc., with results that were remarkable. I did not realize then that with water alone equally good separations could be made. Up to 1906, my endeavors were confined to attempts to keep the concentrates on the tables well wetted and away from exposure to the air. In common with others, I observed that when there mas any obstruction in the wash-water on the table of sufficient size to divert the water to either side, the concentrates collected, and, on exposure to the air, would promptly float away. This convinced me that the sulphides were all good "swimmers," and that if,

Jan 1, 1913

THE Copperton mill in reality was a sort of proving ground. It was. designed to serve three purposes: (1) to verify the accuracy of the mine sampling by actually treating substantial tonnages of ore, (2) to demonstrate on a reasonably large scale the percentage of the copper in the ore that could be recovered, and (3) to permit the testing of various kinds of machines and devices for crushing and concentrating the ore, so as to guide the engineers in designing the proposed 6000-ton milling plant at Garfield. As a matter of fact, it contained a lot of second-hand equipment sent by MacNeill and Penrose from the works of the United States Reduction &Refining Co. in Colorado; and it was by no means a model installation. Probably it would have been even less efficient, except for the skillful work of George O. Bradley and-Frank-G, Janney, both of whom had worked with Jackling at Mercur. Bradley was a mechanical engineer employed to design the plant. Later he directed the design of the concentrator at Garfield and remained as consulting mechanical engineer to the company until 1915. Janney, who afterwards became manager of mills, a position that he retained until his death in 1916, was a skilled mechanic at the Golden Gate mill at Mercur when Jackling built the plant in 1897. His flair was making machinery do what it was intended to do. He was not an ore-dressing engineer in a technical sense; but Jackling him- self was a specialist in this respect as well as in designing and construction and Janney's mechanical aptitude made him a particularly valuable man in the Utah organization. John McDonald, another of Jackling's Mercur associates, was the first mine superintendent. With practically all of the available funds earmarked for construction of the Copperton

Jan 1, 1933

By Frank Corwin

It is the purpose of this article to give a brief account. of the experimental work and to show how the increase in efficiency was brought about. Part of the experimental work described in this paper was carried out by the writers, while in the employ of the Anaconda Copper Mining Co., under the direction of M. W. Krejci, Metallurgist, and Arthur Crowfoot, Chief Sampler. Complete records of all of the MacDougall testing work have been placed at our disposal through the courtesy of A. E. Wheeler, Superintendent. II. BRIEF HISTORY OF PRESENT MACDOUGALL PLANT. The first change from the Brueckner cylinders used for roasting concentrates at Great Falls was the construction of a MacDougall roaster of the Herreshoff type. This furnace was first started on June 15, 1898. It bad eight hearths, was lined with fire brick, and had an air-cooled central shaft, but no provision was made for cooling the rabble arms. It was operated for a while, and accomplished the work of roasting, but ran so hot that the rabble arms became twisted and distorted out of shape. To prevent the furnace from becoming too hot a device was then installed to draw the heated gases away from the hearths. This consisted of a pipe connected to alternate hearths of the MacDougall furnace and also connected to the flue. It was equipped with dampers, 'so that the hot gases could be drawn away from any one of the alternate hearths directly into the flue.

Jan 7, 1913

By E. R. Parker, D. L. Martin

In a previous paper one of the authors observed that the rate of cooling from the anneal prior to testing greatly influenced the life of copper under sustained load at 200°C. Furnace-cooled bars of oxygen-free copper (with and without silver) had a life four to twenty-five times that of the water-quenched specimens. The addition of 0.054 per cent silver to the oxygen-free copper increased the life at a stress of 20,000 lb. per sq. in. from about 2 hr. to 50 hr. Fractures in these bars were intercrystalline. An explanation was advanced to account for the profound influence of cooling rate on the rupture properties at 200°C. The suggestion offered was that at the high annealing temperature the minor constituents are distributed at random. By water quenching, this condition is maintained at room temperature, whereas furnace cooling permits some segregation at the grain boundaries. The higher concentration of the minor constituents in the grain boundaries results in a. strengthening, so that a longer life at a given stress and .temperature results. Small amounts of cadmium or manganese have also been found to increase the life of copper at 200°C., and to a much greater extent than silver.2 The increase in the long-time strength of copper resulting from small additions of cadmium or silver appears to be related, indirectly at least, to the higher softening temperatures of such alloys. The elements, such as silver or cadmium, which greatly increase the rupture life of copper also cause large increases in the softening temperature. As little as 0.05 per cent of cadmium or silver is sufficient to raise the softening temperature more than 100°.3,4 The effects of cooling rate and of minor constituents on the rupture properties are of considerable fundamental as well as practical interest; therefore a more detailed study of their nature was conducted and is reported in this paper. Experimental Procedure Materials The materials studied in this investigation may conveniently be classified in two groups: one consisting of a wide variety of commercial coppers, and the other composed of special high-purity, laboratory-prepared coppers. The commercial materials were tested to determine whether or not the effect of cooling rate occurred with all coppers, whereas the high-purity coppers were investigated in order to establish a basis for evaluating the effect of minor constituents on the rupture properties. In Table I are given the analyses of the coppers tested. The samples I to 6 are commercial materials and were obtained for the most part from stock supplies.*

Jan 1, 1944

By D. L. Martin, E. R. Parker

In a previous paper one of the authors observed that the rate of cooling from the anneal prior to testing greatly influenced the life of copper under sustained load at 200°C. Furnace-cooled bars of oxygen-free copper (with and without silver) had a life four to twenty-five times that of the water-quenched specimens. The addition of 0.054 per cent silver to the oxygen-free copper increased the life at a stress of 20,000 lb. per sq. in. from about 2 hr. to 50 hr. Fractures in these bars were intercrystalline. An explanation was advanced to account for the profound influence of cooling rate on the rupture properties at 200°C. The suggestion offered was that at the high annealing temperature the minor constituents are distributed at random. By water quenching, this condition is maintained at room temperature, whereas furnace cooling permits some segregation at the grain boundaries. The higher concentration of the minor constituents in the grain boundaries results in a. strengthening, so that a longer life at a given stress and .temperature results. Small amounts of cadmium or manganese have also been found to increase the life of copper at 200°C., and to a much greater extent than silver.2 The increase in the long-time strength of copper resulting from small additions of cadmium or silver appears to be related, indirectly at least, to the higher softening temperatures of such alloys. The elements, such as silver or cadmium, which greatly increase the rupture life of copper also cause large increases in the softening temperature. As little as 0.05 per cent of cadmium or silver is sufficient to raise the softening temperature more than 100°.3,4 The effects of cooling rate and of minor constituents on the rupture properties are of considerable fundamental as well as practical interest; therefore a more detailed study of their nature was conducted and is reported in this paper. Experimental Procedure Materials The materials studied in this investigation may conveniently be classified in two groups: one consisting of a wide variety of commercial coppers, and the other composed of special high-purity, laboratory-prepared coppers. The commercial materials were tested to determine whether or not the effect of cooling rate occurred with all coppers, whereas the high-purity coppers were investigated in order to establish a basis for evaluating the effect of minor constituents on the rupture properties. In Table I are given the analyses of the coppers tested. The samples I to 6 are commercial materials and were obtained for the most part from stock supplies.*

Jan 1, 1944

By Ancel St. John

During a session on coal and coke at the February, 1926, meeting of the American Institute of Mining and Metallurgical Engineers, the writer called attention to the important work on the X-ray analysis of coal1,2 being carried on in England by C. Norman Kemp and his associates. This aroused so much interest that a paper on the subject was requested for the October meeting. It has seemed advisable to make this paper a preliminary survey of the present status in the application of X-ray methods to coal problems and to follow it from time to time with further articles as the art develops. A survey of this sort naturally divides itself into two parts, radio-scopic analysis of the distribution of constituents through the body of the coal, and diffraction analysis of the state of association of the elementary components. In this article the subject matter concerning radioscopic analysis has been drawn almost entirely from the writings of Kemp and his associates and the illustrations have been sptcially furnished by him. It is a pleasure to record here a great indebtedness for this courtesy and cooperation. The subject matter and illustrations concerning diffraction analysis are taken from the author's unpublished researches. Nature and Properties of X-rays Before proceeding it is well to recall the nature and some of the properties of X-rays, as well as our present conception of atomic structure According to the accepted theory atoms are composed of electrically-charged particles. A positively-charged center, called the nucleus,

Jan 1, 1927

By J. L. Gregg

RECENTLY there has been considerable interest in the production and use of, extra hard alloys composed primarily of tungsten and carbon. Dr. Hoyt's recent paper1 gives a good description of these alloys and describes their performance when used as tools. There are a number of these alloys on the market sold under various trade names, and it is the purpose of this paper to describe the results of an investigation of the structure of five of these alloys by means of microscopic and X-ray methods. The samples studied were in the form of small tools or wire-drawing dies, which were either purchased or supplied as samples. They were in some cases not supplied by the original makers but were furnished by the agents in this country, and we wish to call attention to the fact that they may not be truly representative of the materials supplied under the various trade names. No performance data are given and no inference as to the inferiority of one alloy as against any other is made K Schröter2 recently described methods for polishing alloys of this type for microscopic examination and has presented photomicrographs of several alloys. However, he did not identify their constituents or describe methods for their identification.

Jan 1, 1929

By E. A. Nesbitt

A new permanent-magnet material has been developed with unusual mechanical as well as magnetic properties. Specimens that have been cast or subjected to a small amount of hot reduction by rolling or swaging may be machined, punched, tapped or drilled. The composition range of the alloys is 30 to 52 per cent iron, 36 to 62 per cent cobalt and 4 to 16 per cent vanadium. After being either quenched, annealed or given the usual cold finishing passes and then heated for 2 hr. at 600°C., such materials have a magnetic energy product of 1.0 X 106 gauss-oersteds. This product is equivalent to that of the well-known Honda steel (36 per cent Co, 4W, 2 Cr, 0.8 C. 0.3 Mn, balance Fe). Material handled in the manner just described does not depend on cold-working for its magnetic properties, and is known as Vicalloy I. The preferred composition for Vicalloy I is 38.5 per cent iron, 52 per cent cobalt and 9.5 per cent vanadium. When the alloys are first hot-worked, then considerably reduced in area by cold-swaging, drawing or groove rolling and then heat-treated, the magnetic energy product measured in the direction of previous extension is increased to 2.0 to 3.5 X 106 gauss-oersteds. These higher values have been obtained only after cold reductions in area of 75 to 95 per cent. Material handled in this manner is known as Vicalloy II and the preferred composi-

Jan 1, 1947

By E. A. Nesbitt

A new permanent-magnet material has been developed with unusual mechanical as well as magnetic properties. Specimens that have been cast or subjected to a small amount of hot reduction by rolling or swaging may be machined, punched, tapped or drilled. The composition range of the alloys is 30 to 52 per cent iron, 36 to 62 per cent cobalt and 4 to 16 per cent vanadium. After being either quenched, annealed or given the usual cold finishing passes and then heated for 2 hr. at 600°C., such materials have a magnetic energy product of 1.0 X 106 gauss-oersteds. This product is equivalent to that of the well-known Honda steel (36 per cent Co, 4W, 2 Cr, 0.8 C. 0.3 Mn, balance Fe). Material handled in the manner just described does not depend on cold-working for its magnetic properties, and is known as Vicalloy I. The preferred composition for Vicalloy I is 38.5 per cent iron, 52 per cent cobalt and 9.5 per cent vanadium. When the alloys are first hot-worked, then considerably reduced in area by cold-swaging, drawing or groove rolling and then heat-treated, the magnetic energy product measured in the direction of previous extension is increased to 2.0 to 3.5 X 106 gauss-oersteds. These higher values have been obtained only after cold reductions in area of 75 to 95 per cent. Material handled in this manner is known as Vicalloy II and the preferred composi-

Jan 1, 1947

By David Russell, Courtland Lee

FOREWOHD-Americans have been able to create wealth from the nation's natural resources to an extent unprecedented in recorded history, thanks largely to the existence of a free market and of a rational body of laws. The General Mining Law of 1872, for instance, by establishing the rules of the game, was quite effective in channeling the ability of Americans to discover and develop mineral deposits. Another example was the Mineral Leasing Act of 1920 which made available the more easily discovered mineral deposits by spelling out the conditions and rules under which miners could obtain leases on federal lands.

Jan 5, 1977

INTRODUCTION Data available on prophyry copper occurrences in the Andean, Caribbean, Appalachian, and Cordilleran orogens may be categorized in a manner to suggest a hypothetical evolution for deposits that occur in the western hemisphere. A classification of de- posits is also suggested. A classification dependent on internal structure of a porphyry copper deposit would lead to two broad categories, breccia pipe and stockwork models. A classification of this type is examined herein but it is not universally accepted in the literature. Modeling based on igneous petrography as well as metasomatism attendant with the sulfide mineralization is more widely accepted by economic geologists whose evaluation of porphyry systems is influenced by the presence or absence of a phyllic zone. Lowell and Guilbert model deposits ordinarily include a phyllic zone, whereas those of the diorite model do not. Position of the phyllic zone in the alteration sequence is a significant ore guide. Should the phyllic zone be absent, dependence on alteration zoning to identify metallization is weakened. Presence or absence of the phyllic zone therefore is a significant parameter in the economic evaluation of a porphyry copper deposit (Hollister. et al., 1975). The Lowell and Guilbert (1970) model commonly includes a phyllic zone in quartz- bearing rocks. Parameters of both calc-alkalic and the quartz monzonite models mentioned elsewhere in this volume are sufficiently close to the Lowell and Guilbert (1970) model that it should be expanded to encompass them. The diorite model remains separate and distinct because deposits of this type are characterized by an absence of quartz in the pluton, commonly highly gold: copper ratios, low molybdenum content, and regular absence of sericite in the alteration zones. Therefore, for the benefit of those

Jan 1, 1978

By B. A. Rogers

ACCORDING to petrographic investigations, 1-4 cooled steel furnace slags contain a number of substances that have been shown to be ferro-magnetic5,6 and hence capable of undergoing appreciable changes of susceptibility with temperature. Since any alteration of the suscepti-bility of a constituent affects the average susceptibility of the sample, information concerning the nature of the substance should be deducible from its magnetic behavior. The possibility of obtaining information concerning slags in this way led to the construction of the apparatus to be described. FUNDAMENTAL PRINCIPLES OF APPARATUS The most convenient method of observing changes in mass suscepti-bility? with temperature is the one employed by Curie7 in his original investigation of the changes in magnetic properties of substances at elevated temperatures. As the method has been described frequently in the literature and in textbooks, only a brief review of the fundamental principles need be given here, but the particular arrangements used in the present work require a more detailed description.

Jan 1, 1939

By M. E. Straumanis, J. -P. Krumme

In basic ([KOH + KCl] with a total polarity of 2) or acidic (2N H2SO4) electrolytes and at anodic current densities of more thun 2 to 4 ma per sq cnz, n-type GaAs single crystals of lozo resistivity preferentially dissol~je forming etch tunnels with triangular or civc~ilay cross sections and of a width between 0.5 arid 5 p. These etch tunnels are oriented along any one of the four possible (111) directions of GaAs. However, their growth occurs only in one direction of a given (111) whick apparently is determined by the atomic sequence Ga —As (and not the rezlerse) in respect to an individual valence bridge in the crystal. It is concluded from comparison with the cubic lattice structure of GaAs that the etch tunnels represent macroscopic evidence for the tetrahedral bonds and their polar properties. If the anodic current density is increased the tunnel fomation results in the development of a fibrous surface layer consisting of GaAs. The latter separates frorn the substrate (in an anodic s~irface disintegration process) by the growth pressure of an As,0, filnz forming in the interior of the fibrous layer, 100 to 200 µ under the surface, at more than about 50 ma per sq cni. The fibrous GaAs film has the same crystallographic orientation as the substvate and represents a skeleton of the original crystal. Since the etch-tunnel density in a separated GaAs layer is about 108 c?n-', and the etch tunnels develop only along (111) in a given polar direction, it is assurraed tlmt the dislocations have no influence on the growth of these tunnels. ElECTROLYTIC treatment of smooth surfaces of poly- and single-crystalline GaAs at high anodic current densities causes the formation of porous surface layers.' This phenomenon suggests comparison with effects being observed with magnesium,' indium,, gallium,4 and aluminum5 and known as "anodic disintegration". The purpose of the present paper is to explore and to explain the reasons for the formation of such surface layers on GaAs and, in particular, to investigate the influence of the lattice polarity of this III-V compound semiconductor in the (111) direction on the anodic dissolution behavior. GaAs SINGLE CRYSTALS For the experiments described below GaAs single crystals from the Monsanto Co., St. Louis, Mo., were used. Their impurity levels were below 1 ppm and their dopant levels between 1 and 100 ppm. They were grown in (111) using the Czochralski or the gradient-freeze technique. The crystals had n-type conductivity and electric resistivities between 1 and 5 ohm-cm. EXPERIMENTAL The GaAs single-crystal rods were cut perpendicularly to (111) into wafers of about 1 mm thickness using a wire-blade crystal slicer and an aqueous slurry of Sic or a diamond saw. The orientation of the faces of these wafers were checked by Laue back-reflection patterns. If there was a deviation from (111) the faces were abraded under a certain angle using grinding paper and distilled water. The damaged surface layer was removed from each crystal by chemical etching with a mixture of 1HF:1HNO3: 1H20 or 2HF:1HNO3:2HAc (glacial). {110) faces were obtained by mechanical cleavage, producing surfaces which did not require a further treatment. The GaAs wafers were mounted using "alligator" clamps instead of soldered electrical contacts.' Only the bare crystal surfaces were dipped into the electrolyte. The clamps were coated with insulating wax to prevent any contact with the electrolyte. The experiments were carried out in aqueous 2 N H2so4,' or in an aqueous solution of KOH and KCl1 (1 mole KOH + 1 mole KCl in 1000 cu cm solution). Anodic current densities up to several hundred ma per sq cm were applied for periods between 30 sec and 2 hr. For the purpose of investigating the initial steps of disintegration the anodic current density applied never exceeded 20 ma per sq cm. The films which partially separated from the anodic surfaces under high-field conditions were treated with KOH to further their detachment by dissolving the As2O3 formed. The washed and dried films were pasted to strips of filter paper, and Laue pictures were made. The back-reflection patterns obtained were compared with those of the original anode surface before and after anodic dissolution. Furthermore, space reciprocal lattices7 were constructed from asymmetric rotation crystal patternsa which permitted the determination of the crystallographic orientation of the detached films of the corrugated anodic surfaces. The disintegration products were identified from assymmetric powder patterns.8 The polarity of the {111) faces was determined by chemical etching with mixtures of 1HF:1H2O2(30 pct): 2H2O or 1HNO3:2H2O. Different patterns on each of two inverse (111) sides appeared.'-l8 The correlation of these patterns to the Ga{111) or the As(111) side has already been established by the use of light figures,18-20 by X-ray diffraction near the absorption edges of gallium and arsenic,'lmZ4 and by LEED measurements.25 The geometric structure of these surfaces and the interior of the anodically attacked crystals were observed and photographed with a high-power microscope using oil immersion objectives up to magnification of X1720.

Jan 1, 1968

By D. K. Crampton

Internal stress and season cracking in brass have been studied for many years and the technical literature contains many data on various phases of the subject. A resume of the literature shows certain fairly well established points upon which various authors are mostly agreed: 1. Season cracking is primarily caused by the presence of relatively high internal stresses, or possibly in some cases by external stresses, or both. 2. A specific corrosion is also essential to season cracking. Certain agents, particularly mercurous salts, mercuric salts and ammonia salts, have such a specific corrosive effect. 3. The tendency to season crack under given conditions increases with increasing zinc content, brass containing less than 20 per cent. zinc being relatively immune. 4. In alpha brass the season cracks are intercrystalline; in alpha-beta brass they lie between the two constituents; and in beta brass they are transcrystalline. 5. The ordinary impurities or added elements in special brasses have little or no effect on the tendency to season crack. 6. Internal stresses can be eliminated, or at least reduced to a safe limit by annealing treatments at temperatures that do not produce visible microstructural changes or appreciable softening of the worked brasses. There are, however, some points in connection with the phenomenon of season cracking which have not been thoroughly investigated, or wherein different authors and investigators are not entirely in agreement. The investigations described in this paper were undertaken to determine: 1. The correlation between mercurous nitrate tests and actual season cracking on long-time atmospheric exposure. 2. The quantitative effect of type and degree of drawing operations on the intensity of internal stress and on the tendency to season crack in brass tubes. 3. The possibility of drawing high-brass tubes in such a manner as to prevent the occurrence of harmful stresses rather than to find a remedy for such stresses once having obtained them.

Jan 1, 1930

By William P. Blake

A recent paper by Prof. George P. Merrill, Curator of the Department of Geology of the U. S. National Museum, Wash-

Jan 1, 1897

By Edwin R. Phelps, Charles W. Porterfield

BACKGROUND OF SURFACE MINING Surface mining refers to the process of removing the material (over- burden) overlying a coal seam and exposing the coal so that it can be loaded out and conveyed by trucks or other methods to the preparation plant or other facility. Surface mining has not always been important in the coal industry. In the early 1900s, almost all of the coal mined in the United States was mined by underground methods. In 1900, about 192 Mt (212 million st) of bituminous coal mere mined and less than 1% was mined by surface methods. The development and use of larger equipment has allowed surface mining to gain prominence throughout the years. Table 1 shows the total production of coal by mining method in the United States for ten-pear periods since 1920 and indicates the growth of surface-mined coal production. Surface mining will undoubtedly continue to account for a large percentage of the coal production in the US for many years because: 1) The capacity of surface mining excavators has continued to increase. Today, mining companies are using shovels (see Fig. 1) which are able to move up to 137.6 m3 (180 cu pd) in each bite and draglines (see Fig. 2) which move up to 168.2 m3 (220 cu pd) in each bucketful. 2) Increasing tonnage from the thick western coal seams is being produced by surface mining methods. 3) Surface mining has normally had lower costs and a better safety record than underground mining. 4) Surface mining normally recovers a much higher percentage of the coal reserve than can recovered by underground mining. 5) Some coal measures call best be extracted by surface mining

Jan 1, 1981

By J. D. McBeth, G. M. Potter, Ramon Pizarro

Heap leaching is used by the Carlin Gold Mining Co., Carlin, Nev., to supplement conventional processing of gold ore by agitation-leaching and countercurrent decantation. Selected open-pit ore containing about 0.072 oz Au per ton is crushed to 3/4 inch, dumped by truck on an asphalt pad, and leached by sprinkling with dilute cyanide solution for 7 days. The heap is then drained and removed by front-end loader to tailings disposal. About 70 percent of the gold is dissolved. Leach solution from the heap joins the pregnant solution from countercurrent decantation for gold recovery by zinc precipitation. Four leach pads, each with a capacity of 1,400 tons of ore, are in use. About 10,000 tons of ore are heap leached monthly from about April through October. Heap leaching is recessed during freezing weather. Labor, equipment, and reagent requirements for heap leaching are presented.

Jan 1, 1974

By E. S. Machlin, W. R. Yankee

IN a previous study1 of the effect of heating com-mercial titanium in air on its subsequent friction coefficient against other metals, as well as itself, it was found that the friction coefficient markedly decreased from a value of about 0.7 to about 0.3. A tentative explanation was given that surfaces normally produced at room temperature are not contaminated sufficiently to prevent seizing or welding of the titanium to the softer mating metals. The latter tend to cleanse themselves during rubbing over the harder titanium. It was thought that the lack of a contaminant protective film on the titanium was due to the high solubility of titanium for oxygen and nitrogen and hence an inability to form a contaminant oxide or nitride. This explanation requires the ratio of the surface absorption rate to the diffusion rate to become much lower at room temperature than it is at high temperatures. In order to check the phenomenon further, commercial titanium specimens were nitrided or oxidized at 800°C for 20 hr in flows of prepurified N2 and 01, respectively, at about 1/2 in. H2O above atmospheric pressure. Friction runs were made in argon using a freshly cut copper hemisphere (cut in argon) on surfaces cut successively into the diffusion layers in the titanium (cut in argon) using the techniques described in a previous publication.' DPH values (100 gram load) were made as a function of depth into the diffusion layer using a Tukon tester. Also, micrographs were taken at separate cross sections to indicate the diffusion layers. The results obtained are presented in Figs. 1 and 2, which show the "static" friction coefficient vs hardness for the nitrided and oxidized specimens, respectively. A separate measurement of the friction coefficient of clean copper vs iodide titanium also was made. From results reported in the literature' giving the oxygen and nitrogen contents as functions of the hardness, cross plots were made showing the friction coefficients as functions of the amount of interstitial solute. These plots are given in Figs. 3 and 4. From micrographs of the diffusion layers and the phase diagrams, it was deduced that the data in Figs. l through 4 correspond to the single phase a region. The points observed on the compound regions have been excluded from the figures. It is apparent that nitrogen or oxygen in solution in the a titanium markedly affects the friction coefficient against a softer mating metal. Discussion of Results These results are extremely interesting from both a practical and theoretical viewpoint. The theoretical implications will be discussed first. According to Bowden, the friction coefficient should be given to a good approximation by the relation where a is the fraction of contact area that has welded, a is the shear strength of weaker component, and H is the hardness of softer component. Using this relation alone, it is difficult to understand the results because none of the terms should be affected by a variation in the oxygen or nitrogen content of the harder and stronger metal, titanium. Even if the ratio of S/H for titanium is used in Eq. 1, the ratio has been shown to be independent of oxy-gen or nitrogen content.' If a more rigorous equa-tion is used combining Eq. 1 and a result given pre-viously" for the case where welding is absent, then the relation obtained is µ = a S/H + (1-a) a W aß/H where a is constant and Waß is the work of adhesion between the two metals comprising the friction couple. This relation states that if a is less than 1/2 or so, variation in the work of adhesion Waß between copper and the titanium should affect the friction coefficient markedly. It is reasonable to expect that the work of adhesion will depend on the oxygen or nitrogen content of the titanium. Available data4 show that clean metals and oxides have much lower works of adhesion than the same metals against the

Jan 1, 1955

By Frank T. Sisco

SHORTAGES of metals and minerals and substitution of less critical materials for those in which a virtual famine exists received detailed and frank discussion at a recent conference in Washington called by Robert E. McConnell, director of the Conservation Section, Office of Production Management. Representatives of the large engineering societies in the United States and O.P.M. department heads participated in the discussion. To open the session Mr. McConnell called upon Zay Jeffries, chairman of the O.P.M. Advisory Committee on Metal Conservation and Substitution, to summarize the present situation. Dr. Jeffries touched briefly on the status of metal shortages, which has already received considerable attention in the popular press, and said that much of the present difficulty was caused by the too-hasty substitution-without sufficient con¬sideration of the immediate conse¬quences-of metals having ordinarily a small yearly consumption, for those having a much larger annual consumption. As a result, all the alloying metals used in alloy-steel manufacture have become scarce, with the exception of molybdenum; further¬more, despite a reserve of 11,000 tons of molybdenum in this country and despite a normal consumption of only about 3500 tons and a prospective annual production rate of 21,000 tons by October, a shortage of molybdenum is possible before this war is over.

Jan 1, 1941

By W. Bradley, R. G. Hall

This paper will attempt to show how a metallurgical problem at one California quicksilver mine was solved, and how the solution was applied successfully at another mine. The pronouns "we" and "our," as used below, refer '0 the Bradley 'lining Co. of San Francisco. The term "concurrent firing" for the purpose of this paper can be defined as feeding and firing a a kiln at the same end—that is, of course, the upper end' This is as opposed to "countercurrent firing," the orthodox method, in which a kiln is fed at the upper and fired at the lower end. The terms "quicksilver" and "mercury" are used interchangeably. Early References The earliest work on nonferrous metallurgy, we believe, was The Pirotechnia of Vannocio Biringuccio,l its first edition having been printed in Italy in 1540. Quoting from its chapter entitled "Concerning Quicksilver and Its Ore": Quicksilver ... is one of the gods and has divine strength in itself, and also, to the annoyance of the alchemists, it is winged. Hence, when it sees that it is in gravest danger, it loosens itself from . . . every bond . . . and fies away into the heavens, escaping from the hands of those who crucify it. Almost laughing, it leaves all its adversaries mocked and scorned, with their phials and filters empty . . . How thorough a job, under certain conditions, it can do of mocking its adversaries and leaving their phials and filters empty, was found out four centuries later at the Sulphur Bank mine, on the east shore of Clear Lake, in Lake county, California, The other mine mentioned in the title is the Reed, in Yolo County, California, 35 miles by road southeast of Sulphur Bank, Reed and Sulphur Bank ranked respectively Nth and seventh in U. S. production in 1943. The earliest direct reference we can find to furnacing troubles at these mines was by Thomas Egleston in 1890.2 Speaking of Sulphur Bank, Egleston says: of there is more sulphur than cinnabar in the ore, which is a detriment to both . . . making the sulphur impure, and rendering the cinnabar difficult to work on account of the soot. In some of the early . . . furnaces the accumulation of soot from the excess of sulphur has been known to penetrate as far as the fan blower at the end of the . . . condensers, and completely prevent its revolution. In order to get rid of the inconvenience of this accumulation . . . , as well as to get a commercial value from the sulphur, it (the sulphur) is now separated by steam and sold. It is claimed that the sulphur alone pays all the expenses of ... the mine. The mine was first worked for sulphur, and the cinnabar it contained was considered to be an inconvenience, and was carefully picked out and thrown away, as its richness and value were not

Jan 1, 1949