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By A. H. Grobe, F. N. Rhines

THE constitution of the indium-zinc alloy series has been investigated by Wilson and Peretti,1 who determined the liquidus and eutectic temperatures by the conventional method of cooling curves and the eutectic composition by analyzing eutectic exudations. Recent developments affecting the availability of indium and consequent increased interest in its applications make a more complete knowledge of the constitution of its alloys desirable. As a part of a program for the reexamination of the constitution of indium alloys by precision methods, the indium-zinc phase diagram [ ] (Figs. I and 2) has been redetermined in its entirety. The eutectic temperature (143.5°C.) reported by Wilson and Peretti has been confirmed exactly, but their value of the zinc concentration at the eutectic, 4 per cent, was found to be high; the new value is 2.8 per cent of zinc. There is also a rather large difference between the forms of the liquidus curves of Wilson and Peretti and those found in the present studies. The solidus curves herein have been located for the first time and the limits of solid solubility have been tenta-

Jan 1, 1944

By H. Rosenthal, A. L. Jamieson

Stress-corrosion cracking of copper-base alloys is of considerable importance and has been the subject of many investigations which employed various accelerated tests and long-time service tests. The outstand¬ing accelerated tests used are variations of either the mercury cracking test reported by Rogers in 1905( 1)2 or the ammonia test reported in 1910(2). The ease of applica¬tion of the mercury test is probably the reason industry adopted it. Subsequent investigation of this test(3,4) revealed that a minimum threshold stress was necessary before mercury cracking could develop. Since season cracking has been found in some instances in caliber 0.3o ammunition which has passed the mercury test, it is evident that the threshold stress value of the mercury test may be too high for dis¬tinguishing between acceptable and un¬acceptable caliber 0.30 cartridge cases. This condition has naturally led to the study of an ammonia test with its ability to cause cracks with almost any stress level. But the lack of a definite threshold value means that standards are necessary for evaluating the results of the ammonia test.

Jan 1, 1945

By Paul Wilkinson

From the earliest times, the principal component of mallplaster has been ordinary lime. Plaster-of-Paris has also been known from early times, but never used to any extent in the actual base-work of plastering-materials; it is generally used for finishing over the brown coat and for ornamental work. As an illustration of the antiquity of the use of gypsum-plaster for mortar, I find that the analysis of the exterior covering of the pyramid of Cheops, as made by Dr. Wallace, is almost identical

Jan 1, 1898

INTRODUCTION TO PROBABILITY THEORY The mathematical theory of probability provides the foundation for the interpretations and inferences that can be made from statistical techniques. Probability theory is a broad field of study in itself, and can only be touched on here in order to provide the necessary back- ground for a more complete understanding of statistical analysis. Probability is concerned with the outcome of random events. It had its beginnings in the theory of games of chance which were of great interest to European mathematicians during the last half of the 17th century. The outcome of a random process or experiment is defined as an event. The collection of all mathematical points associated with each event is called the sample space for an experiment. Consider a random experiment having a finite number, n, of possible outcomes, some of which have a characteristic A. What is the probability that A will result from a single

Jan 1, 1980

By George W. Bain

The good work of the surveys supported by the different branches of the government needs little mention to geologists but is underappreciated by people at large. Geologists and engineers realize their usefulness and yet even from this group one hears occasionally an undercurrent of discontent about their work or the distribution of it. The very fact that discontent arises within and without this group and has drawn attention of legislative bodies of the country in the present time of stress means that a large number of people do not receive or do not realize that they receive benefit from these public works. This seems to be a clear indication that more than the relations between government surveys and the mining industry is involved and that if the mining industry is interested in continuation of the work of these surveys on the past scale they must consider the other survey divisions and their activity. Also, relations between government surveys and certain specialized types of mining have not been as close as they should be. I have been employed in almost the entire range of fields offered to geologists and have studied closely the feeling of people towards geological service. Recently it has been a pleasure to be closely associated with men who were as deeply interested in civic welfare and affairs of state as in the financial success of a large industry developing natural resources. Previously I had seen service in a national survey, a state survey, summer employment by a large mining company exploring new property and detailed geological work for a large corporation. Major responsibility as a college instructor has left me free to view each of these assignments in unprejudiced fashion and at the same time study the relation of government surveys to large natural resource industries, average industrial and construction work and service to nongeologists and laymen. Considerations Governing Geologic Public Service Three groups of people must be satisfied by the surveys if dissatisfaction is to be dispelled. First there is a large group of people who pay taxes to support the government activities and must receive some service

Jan 1, 1935

By G. W. Jarman

THE purpose of this paper is to present briefly a description of some of the special methods of separation or concentration, either singly or in combination with others, and to give certain operating data and examples. Explanation of the usual methods of large-production mill treatment, such as flotation or wet tabling, or of chemically treating industrial minerals, is not included in the scope of this paper, although one of these methods might be, in certain instances, augmented by one or more of the special methods that will be enumerated herein. Description of these special methods will be centered on magnetic separators, electro- static separators and air flotation or air tables. MAGNETIC SEPERATORS In general, separating is achieved by exerting upon a particle some kind of force opposed to gravity, either directly or at an angle. For example, in the Wetherill or cross-belt type of magnetic separator some particles are lifted vertically from the others because they have been exposed to a force to which they respond more readily than particles of lesser magnetic susceptibility. Of course, there is a limitation to this vertical rise, for the particle must be of a high enough susceptibility to receive a magnetic force greater than the 980 dynes per gram of gravitational urge. To overcome this limitation, the induction type of magnetic separator was developed, so that it is only necessary to instill, say, 30 to 60 dynes per gram instead of the 980, to cause a deflection away from the vertical in falling, and that deflection can be used advantageously when falling by inserting a dividing knife-edge. The induction magnetic separator (Fig. 1) has become a fairly well known method of concentrating and purifying. For example, abrasive grain was among the materials that did not respond to the previously best known type of magnetic separator, such as the Wetherill type, and the development of the induction magnetic separator in the plant of a

Jan 1, 1938

By George W. Bain

The good work of the surveys supported by the different branches of the government needs little mention to geologists but is underappreciated by people at large. Geologists and engineers realize their usefulness and yet even from this group one hears occasionally an undercurrent of discontent about their work or the distribution of it. The very fact that discontent arises within and without this group and has drawn attention of legislative bodies of the country in the present time of stress means that a large number of people do not receive or do not realize that they receive benefit from these public works. This seems to be a clear indication that more than the relations between government surveys and the mining industry is involved and that if the mining industry is interested in continuation of the work of these surveys on the past scale they must consider the other survey divisions and their activity. Also, relations between government surveys and certain specialized types of mining have not been as close as they should be. I have been employed in almost the entire range of fields offered to geologists and have studied closely the feeling of people towards geological service. Recently it has been a pleasure to be closely associated with men who were as deeply interested in civic welfare and affairs of state as in the financial success of a large industry developing natural resources. Previously I had seen service in a national survey, a state survey, summer employment by a large mining company exploring new property and detailed geological work for a large corporation. Major responsibility as a college instructor has left me free to view each of these assignments in unprejudiced fashion and at the same time study the relation of government surveys to large natural resource industries, average industrial and construction work and service to nongeologists and laymen. Considerations Governing Geologic Public Service Three groups of people must be satisfied by the surveys if dissatisfaction is to be dispelled. First there is a large group of people who pay taxes to support the government activities and must receive some service

Jan 1, 1935

By Roy Moore

THE Tom Reed Extension and Big Jim mines of United Eastern Mining Co. are situated in the Oatman district, Mohave County, Ariz., about 28 miles southwest of Kingman, the nearest railway point. Articles descriptive of the mine surface plant, mill construction, and plant operations have been written by Otto Wartenweiler1, the designing engineer; Wheeler 0. North,2 when he was assistant general manager for the company, and Earle M. Bagley, mill superintendent.3 The last article covers average costs for the full time the mill was operated. The geology of the mines is described by F. L. Ransome4 of the United States Geological Survey. Production was started in January,. 1917, and the known orebodies were exhausted in May, 1925, showing a life of seven years and five months. On account of the comparatively short life and the fact that stoping operations were confined to two orebodies, little experimenting was done with mining methods. The two orebodies were in what is generally called the Tom Reed-United Eastern vein, which occupies a fault fissure having a normal displacement of several hundred feet. Seven or eight very productive ore shoots were mined along this vein in a distance of 1 ½ miles, the two worked by the United Eastern being 1 mile apart. The maximum dimensions of the Tom Reed Extension ore shoot were height, 750. ft.; length, 950 ft.; thickness, 48 ft. The vein structure varied from a solid quartz-calcite filling to a series of parallel stringers separated by andesite. From this body, 511,976 tons of ore were mined. (Fig. 1.)

Jan 1, 1928

By John Chipman

IT has been long known that the gas evolved during the boil in the open-hearth furnace is mainly carbon monoxide associated with smaller quantities of other gases. A number of attempts have been made to determine the precise effects of carbon and oxygen content of the bath, and of other factors, such as temperature, upon the evolution of carbon monoxide. In his investigation of the carbon-iron oxide product in liquid steel, Herty1 showed that the value of this product at equilibrium could be approximated by plotting the value of the product observed in open-hearth reactions against rate of carbon elimination, and extrapolating to zero rate. The results of this study showed a slight but definite effect of temperature upon the carbon-iron oxide reaction. Experimental studies of the evolution of gases from rimming-steel ingots have not yet attained the degree of precision necessary for an exact understanding of the effects of pouring temperature, carbon content, and iron oxide in the metal upon the composition of these gases. Klinger2 showed that the gas consists mainly of carbon monoxide, and that con-siderable variation in its composition occurs during the solidification of the ingot. In order that these variations may be understood in their proper relationship to the progress of solidification of the ingot and the segrega-tion that accompanies solidification, it is essential to have a knowledge of the condition of equilibrium in the several chemical reactions by which the gases are being formed. It is also necessary to understand the effects of temperature upon the equilibria, and further, to know the manner in which the temperature of the liquid metal within the ingot changes as the skin of the ingot is being built up. The reactions in which we will be chiefly interested are those involving in the one case the oxides of carbon, and in the other case steam and hydrogen, with iron oxide and carbon in the liquid metal. The reactions as they occur in unalloyed liquid iron, and their respective equilibrium constants are written as follows:

Jan 1, 1937

By Alden Greninger

TWINNED metal crystals are usually designated as either deformation twins or annealing twins. If twins are to be classified according to the treatment the metal has undergone just prior to the obser vation of the twins, there are two other possible groups: (1) solidification twins,? when observed in the as-solidified or as-cast condition, and (2) transformation twins, ? when observed in a metal which has been cooled from above an allotropic transformation temperature. McKeehan has demonstrated that ferrite does, occasionally at least, contain twinned structures2. The twins, which he studied by optical methods, were obtained during the preparation of iron single crystals by very slow cooling through A3. He proved that the twin relation was actually that which previous investigators had predicted; namely, twinning along three planes of the form {112}. Since McKeehan's discovery, little or no attention has-been given to this transformation twinning of alpha iron, or to the possibility that it might occur at all speeds of cooling from above A3 instead of merely during the prepara-tion of single crystals. McKeehan's twins were evidently regarded as interesting only in proving that a body-centered cubic metal could form twinned structures-at least under certain conditions. It is generally believed that iron seldom if ever forms annealing twins. Certainly the straight-line banding which is so abundant in annealed face-centered cubic metals is characteristically absent in iron annealed below A3. However, O'Neill3. has studied "twin-like" crystals in annealed alpha iron and concludes that the specimen he studied actually

Jan 1, 1936

By William E. Ford, Edward Salisbury Dana

I. Oxides of Silicon. 11. Oxides of the Semi-Metals : Tellurium, Arsenic, Antimony, Bismuth ; also Molybdenum, Tungsten. III. Oxides of the Metals. The Fifth Class, that of the OXIDES, is subdivided into three sections, according to the positive element present. The oxides of the non-metal silicon are placed by themselves, but it will be noted that the compounds of the related element titanium are included with those of the metals proper. This last is made necessary by the fact that in one of its forms TiOz is isomorphous with MnOp and PbOz. A series of oxygen compounds which are properly to be viewed as salts, e.g., the species of the Spinel Group and a few others, are for convenience also included in this class.

Jan 1, 1922

By William J. Douglas, Jack T. Urie, Randall D. Metz

Production and financial planning for a new underground mine requires the coordination of equipment and coal reserves in a manner which assures that resources are utilized efficiently in achieving the target mine production. It is necessary to establish the productions which are attainable at the section level during different mining operations (advance, retreat, development) and under different mining conditions (roof, seam height, resource quality). It is also necessary to identify the interactions between production plans and ventilation equipment So that operations can be carried out without disruptions caused by inadequate ventilation. A set of computer models has been applied in planning a number of new coal, oil shale, and phosphate mines. A critical path production model, CPMINE, was used to determine face production levels for different cut sequences and seam heights, taking into account machine performance characteristics and operational availabilities under these varying conditions. The results formed a production data base for use in the mine sequencing model, MPLAN. This model processes each of the segments of a user-defined mine sequence network (strategy tree) taking into account the equipment available for mining operations and the previously determined production scheme devised by the mining engineer. Mine ventilation was analyzed with an expanded version of the Penn State MVS Ventilation model to determine fan and ventilation shaft requirements for supporting alternative production strategies. The MCOM mine cost analysis model has been applied to evaluate the economic performance of mining alternatives. The results of these studies were used to make decisions relating to equipment selection and acquisition schedules for both room-and-pillar and longwall mining systems. The approach and procedures which were used during these studies are described.

Jan 1, 1983

By Paul A. Farrar, Louis P. Stone, Harold Margolin

The Ti-Mo-0 system was investigated in the region 0 to 45 wt pet Mo and 0 to 10 wt pet 0, from 600° to 1400°C. Solidus data are also presented. Isothermal sections at 700°, 900°, 1100°, and 1300°C, and vertical sections at 1 and 28 wt pet Mo, and 1 and 10 wt pet 0 are included. STUDY of the Ti-Mo-0 system has been carried out as part of a general study of titanium phase diagrams. The binary Ti-Mo system has been investigated in whole or in part by several investigators.1-8 It was found that molybdenum and ß-tita-nium form a complete series of solid solutions and that the ß/a + ß transus is depressed to below 600°C at approximately 30 pet Mo.* The Ti-O system has been investigated partially or fully in the range 0 to 30 pet 0 by several investigators." Extensive solubility of oxygen occurs in the field. While a is

Jan 1, 1957

By R. L. Hadley, G. Derge

The amounts of oxygen in liquid iron-titanium alloys up to 50 pct Ti were measured and the oxide phases in equilibrium with these alloys were determined by using TiO² crucibles. A minimum of about 0.003 pct 0 occurs at less than 1 pct Ti. The various liquid and solid oxide phases can be arranged on a ternary isotherm. THREE characteristics of titanium contribute to the interesting aspects of its reaction with oxygen in liquid iron: 1—It forms a number of stable oxides. 2—All oxides have large negative free energies of formation. 3—The pure metal exhibits high solubility for oxygen. In addition, the use of titanium as a stabilizing and strengthening element in alloys suggests a need for investigation of its reactions in amounts greater than those normally required for deoxidation. These higher compositions are also of interest because they occur during the addition of ferroalloys and produce deoxidation products before dilution is achieved. Titanium Deoxidation in the Literature While the use of titanium as an alloying element and deoxidizer has been common for several decades, the first detailed study of its deoxidizing characteristics was carried out by Wentrup and Hieber' in 1939. These authors determined the extent of deoxidation possible with titanium and identified, by microscopic examination, the products formed. They found that titanium in excess of 0.2 pct did not reduce the oxygen content of iron below 0.004 pct at 1600°C. They identified the spinel FeO-TiO² at low titanium concentrations and Ti2O³ in melts containing more than 0.2 pct Ti. A portion of the area surveyed by Wentrup and Hieber has been investigated recently by Evans and Sloman² using X-ray diffraction for inclusion identification. They concurred in general with the findings of Wentrup and Hieber, but reported the existence of Ti³O5 as a deoxidation product in the range near 0.1 pct Ti. Comstock, Urban, and Cohen³ discussed the deoxidation of iron with titanium, correlating the data of Wentrup and Hieber with free-energy data for the titanium oxides. Scatter at high titanium values was considered attributable either to the formation of an oxide exhibiting high solubility in liquid iron or to the entrainment of solid oxide particles leading to high apparent solubility. Chipman' has calculated the deoxidation curves for titanium based on free-energy data for titanium oxides. These calculations (Fig. 1) and those of Comstock, Urban, and Cohen involve assumptions as to the activity coefficients of oxygen and titanium in liquid iron, since such data have not been determined. Investigation of the deoxidizing characteristics of chromium" and vanadium0 have shown that these elements decrease the activity coefficient of oxygen in liquid iron, leading to a tendency toward relatively high oxygen values and experimental scatter in highly alloyed melts. Experimental This investigation involved two major objectives: 1—determination of the composition of the oxide phases in equilibrium with liquid Fe-Ti alloys, and 2—establishing the pattern of oxygen solubility in liquid Fe-Ti alloys at titanium concentrations in excess of that required for attainment of minimum oxygen content. Raw Materials Ingot iron was used having the following composition: 0.02 pct C, 0.017 pct Mn, 0.01 pct Si, 0.02 pct S, 0.006 pct P, and 0.03 pct 0. The titanium used

Jan 1, 1956

By G. W. Brock

Experiments in the form of aging of overstrained tension specimens and elevated temperature tension testing, have been carried out on recrystallized arc-cast molybdenum. The aging behavior of molybdenum was found to be strongly dependent on the degree of plastic strain present in the lattice: the reason for this being the low solid solubility for the common interstitial elements in molybdenum. GEORGE W. BROCK, formerly Research Associate, Department of Theoretical and Applied Mechanics, University of Illinois, Urbana, III., is Research Associate, Department of Engineering Sciences, IBM Research Center, Yorktown Heights, N. Y. Manuscript submitted January 19, 1961. IMD THE term strain aging is familiar in connection with the recovery of the yield point in mild steel after tensile overstraining, and there are other instances where it is known to exert an appreciable effect on mechanical properties. For example, steel exhibits a greater tensile strength at mildly elevated temperatures than at room temperature and serrated stress-strain flow curves occur under certain conditions. It has been known for a number of years that the phenomenon of strain aging is directly connected with the presence of carbon and nitrogen in the lattice; and extremely small amounts of either element are sufficient to produce the effect. In this study, the aging behavior of overstrained tensile specimens of recrystallized molybdenum has

Jan 1, 1962

The paragraphs quoted, regarding Mr. Hoover's appointment as chairman of the newly organized food board of the United States, are taken from the editorial page, of the New York Times for April 13: ?The country is fortunate in commanding the services of Herbert C. Hoover as Chairman of the newly established Food Board. This is n, problem of first importance. Few realize the extent to which American food stuffs will enter into the decision of the war, and it is doubtful if it has occurred to many minds as yet that we shall have to deny ourselves what we have regarded as necessaries in order to keep our European allies supplied. " Mr. Hoover is one of the leading mining engineers of the country. At the outbreak of the war he put his private affairs aside to become the head of the American Commission for Relief in Belgium. He has had an experience that perhaps no other man has ever had, covering the raising of money and the purchase and distribution of supplies on a large scale; He has been brought into close relations with the neutrals and the belligerents on both sides. By them all he is recognized is one of the best executives brought to the fore by the mar. Mr. Hoover is in a position now to place abilities and experience at the service of his country. He will come back with comparative data that will enable him to measure resources and deficiencies accurately. This appointment gives renewed assurance of our Government's grasp of the problems of war and its resolve to apply, business principles to their solution."

Jan 5, 1917

By H. C. Rogers

A phenomenological study of the failure of polycry stalline ductile metals at room temperature was carried out using light and electron microscopy. Tensile fractures as well as sections of partially fractured bars of OFHC copper in particular were examined. The initiation and growth of the central crack in the neck of a tensile specimen occurs by void formation. After the formation of the central crack the f'racture may be completed in either of two ways: by further void formation or by an "allernating slip" mechanism. The first leads to a "cup-cone" failure; the second, to a "double-cup" failure. In the past decade or decade and a half there has been a great deal of emphasis on the solution of the problem of the brittle fracture of metals, particularly those which normally exhibit considerable ductility such as steel. Since the problem of the fracture of metals after large plastic strains has less immediate commercial or defense significance, there has been considerably less effort expended in describing the details of the phenomenology and determining the mechanism of this type of fracture. The present research was undertaken to increase our knowledge in this area. The problem of ductile fracture has not been neglected completely, however. Ludwik1 first found by sectioning a necked but unbroken tensile specimen of aluminum that fracture began with a large internal crack which appeared to have started in the center of the neck. Examination of the fracture indicated that the crack had propagated radially with increasing deformation until a point was reached at which the path of the fracture suddenly left this transverse plane and proceeded at approximately 45 deg to the stress axis until the surface was reached. This gives rise to the commonly observed cup-cone tensile fracture. When MacGregor2 was attempting to demonstrate the linearity of the true stress-true strain curve from necking until fracture, he found that copper was anomalous in that the stress dropped off markedly from the straight line value before fracture occurred. Radiography indicated that in the copper an internal crack was formed long before the final fracture, the stress decreasing during the growth of this crack. One of the most significant advances in the understanding of ductile fracture was the result of work by Parker, Flanigan, and Davis.3 By the use of etch-pit orientations they were able to demonstrate conclusively that the fracture surface at the bottom of the cup, although on a gross scale normal to the tensile axis, did not consist of cleavage facets as had been previously supposed by many investigators. Recently, Forscher4 has shown evidence of porosity near the tensile fracture of hydrogenated zirconium which he attributes to hydride decomposition. The workers at the Titanium Metallurgical Laboratory5 have also shown evidence of porosity in a number of the commonly used metals after heavy deformation. Many metals have relatively low ductility during creep tests at high temperature. The fractures are intercrystalline, resulting from the nucleation and growth of grain boundary voids. The work in this area has been recently reviewed by Davies and Dennison.6 It is possible that some of the observations and conclusions may have a bearing on the present study? especially since at least two studies7,' have been extended down to room temperature and below using magnesium alloys. However, since magnesium does exhibit low-temperature cleavage, these results may not be pertinent to the present one. The use of the electron microscope as an aid to the study of fractures has been extensively exploited by Crussard and coworkers.9 The examination of direct carbon replicas of the fractures of a large number of metals and alloys showed that the bulk of the fracture surface was covered with cup-like indentations of the order of 1 to 2 µ in size. These frequently had a directionality by which Crussard claims to be able to tell the direction of the crack propagation. With this rather disconnected background of information, this investigation was undertaken in the hope of presenting a unified picture of the initiation and propagation of a fracture in a ductile metal. To this end all of the techniques previously used were employed simultaneously so that there might be a good correlation of the data obtained by different techniques. EXPERIMENTAL PROCEDURE The metal which was chosen as the starting material for this investigation was OFHC copper. Of the dozen or so materials considered, it best fulfilled the requirements of commercial availability in large sizes, good ductility, relatively high melting point compared with room temperature and

Jan 1, 1961

GOVERNMENT ESTABLISHES DIVISION OF ENGINEERING Government supervision of employment for technical men has been inaugurated by the United States Employment Service, through the establishment of a Division of Engineering, with A. H. Krom, of Chicago, formerly Secretary of the American Association of Engineers, as Director. War demands on the engineering profession have already caused a serious shortage of men with mechanical designing experience and those with practical experience in chemical engineering. At present the professional organizing mediums reach less than 20 per cent. of the estimated 300,000 technical men in the country. This is not a satisfactory arrangement for war times. All the technical men of the country must be reached and, in addition, all men with technical experience must be carefully registered so that they will be immediately available. The advantages of such a governmental registering and systematizing of employment will be apparent at once, to the engineer. Considering that this is principally an engineer's war, the importance of Federal direction of distribution and conservation of the technical service of the country is apparent. The Service will he started through the office of the Director of Engineering, 29 S. LaSalle St., Chicago. All technical men desiring to register for emergency Government work or permanent advancement in positions meeting their qualifications, are urged to volunteer at once for registration, classification and employment.

Jan 8, 1918

By Ford R. Bryan, Edward F. Runge

BECAUSE of the need for ductile heat resistant alloys of non-strategic composition, there has been metallurgical development of Fe-A1 alloys possessing improved ductility and hot strength, together with high oxidation resistance. Iron and alu- minum form solid solutions up to approximately 35 pct Al. Alloys in the 8 to 12 pct A1 range are characterized by excellent oxidation resistance, high electrical resistivity' and, when appropriately alloyed, have creep rupture strength equivalent to that of the austenitic stainless steels.' At higher aluminum levels, the magnetic properties are of considerable interest. Nachman and Buehler" have recently reported on the desirable magnetic characteristics of the 16 pct alloy.

Jan 1, 1957

By Eric Jette

THE alloys of gold and iron were investigated in 1907 by Isaac and Tammann,1 who determined the thermal diagram for the entire system by thermal analysis and microscopic examination. They also reviewed the previous literature. Since that time the present authors have been able to find only two additional references. Guertler and Schulze2 examined the electrical resistance of iron alloys containing up to 40 per cent by weight of gold between 0° and 200° C.; the alloys were in the form of wires. The main result of this work was to confirm the solid solubility limit found by Isaac and Tammann; namely, about 20 per cent Au. More recently, Shih3 has examined the magnetic properties of gold alloys containing up to 10 weight per cent iron and particularly the range below 5 per cent. The alloys in the lower range were found to be paramagnetic; the 10 per cent alloy was ferromagnetic. The present investigation was undertaken to determine the solid solubility limits at various temperatures, particularly below the a-y transformation point of iron, since these solubilities are of some impor-tance in connection with the working of the alloys in the manufacture of certain "grey" and "blue" golds.

Jan 1, 1934