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By B. H. Dunshee

THIS paper is not intended to be a technical discussion of square-set framing as used in mines, but merely a short description of the different kinds of framing that have been used in the Butte mines, and what has been decided upon, after years of practical experience, as being the best, taking into consideration the physical condition of the veins and country rock, and. also the supply of timber available for mining purposes. Butte is, essentially, a square-set district. Virginia City, Nev., was the first mining camp to use this method of timbering, and to Philip Deidesheimer, who went to the Ophir mine in 1860, is given the credit of solving the problem of square-set framing, where large bodies of ore were stoped and the timbers were supposed to hold the ground from caving without any filling. That he did his work well is shown by the fact that the main features of his framing are in use to-day. In the Butte mines the conditions are such that this method of timbering is generally used. We do not, of course, depend upon the timbers any more than is necessary. The worked-out stopes are filled with waste rock as close behind the miners as possible and not interfere with mining operations. The waste rock is obtained from development work on the different levels or from the surface. In the earlier days of mining in Butte there were numerous independent companies and naturally there were different ideas as to the best way to frame the square sets, although the general features were the same.

Jan 8, 1913

By Thomas, J. Elmer

WHEN the price of crude oil was advanced on July 26, 1928, with some 4,000,000 bbl. daily of potential production shut in under proration regulations, and with as much more new production shortly available from semi-proved undrilled reserves, students of the oil industry were made to realize that a new order of things now prevailed in petroleum economics. A new interpretation of the law of supply and demand had taken the place of the archaic method of influencing current production by changing crude price levels. Proration had caused the change. The long period of over-production just experienced, the prospects of a potential over-supply far into the future, had set up certain forces which brought about some fundamental changes. Their cause, effect and future influence can best be developed by a detailed study of the history of the period since war-time regulation

Jan 1, 1928

By Marc Lemieux

Computer pit design techniques generally make use of models in which the deposit is represented by a regular array of data. Using a regular system, the number of data points required to represent the air, waste and mineralization in a large deposit become excessive. The number of blocks used to describe the deposit is dependent upon the block size. The quality of the pit wall slope design also is dependent upon the block size used and the method of defining the slope. The error associated with reserve calculations becomes greater with increasing block size. A deposit model consisting of variable sized air and mineralized blocks has been developed at the University of British Columbia and improved upon at Climax for pit design work. The method permits put- ting the entire model in core for rapid data processing. This permits the use of a versatile cone generation technique which allows close adherence to variable slope constraints in all directions. The conical shape is approximated by rectangles on each level which equal the area of the ideal conical intersection. The shape of the intersection may vary from approximately circular to elipsoidal. The approximate cone shape is controlled by the slope constraints applicable at the point of intersection on the bench. The overall modeling technique greatly assists the pit design engineer in developing a high quality pit design.

Jan 1, 1977

By J. D. Price, G. V. Woody

MANY producers of by-product coke have spent considerable time and given considerable thought to the use of a substitute for low-volatile coal as an admixture with high-volatile coking coal for charging high-temperature by-product coke ovens. Generally speaking, there are two principal reasons for this, one being occasioned by the lack, in certain localities, of low-volatile coal delivered at a cost sufficiently low to permit its use, and another being the desirability of finding a substitute product with a delivered cost lower than the cost of the low-volatile coal. It was for the first of these reasons that the Colorado Fuel and Iron Corporation was particularly interested in this subject. This paper deals with the experimental work and the results obtained by that company in producing and using low-temperature char. OVERCOMING DEFECTS IN COKE FROM COLORADO COALS Colorado coking coals are all of the high-volatile type and were all laid down during he Cretaceous period, which makes them something like 80 million or so years younger, geologically, than eastern coals. They behave, when coked alone, something like the Pittsburgh-seam coals. They make a very brittle, highly cross-fractured, fingery coke of fair shatter value but quite low in resistance to abrasion. Mixed with a low-volatile coking coal such as Pocahontas or certain Oklahoma coals, they make a coke that is equal to virtually any of the eastern cokes. The inferior quality of Colorado coke has long been recognized, and a considerable amount of time, effort and money has been spent upon investigations of means for improving its physical properties. While it has been found that some improvement in quality of coke can be secured by the adjustment and control of such variables as pulverization, moisture content, oven temperature and bulk density of charge, and through the addition of certain inert materials such as pulverized coke breeze, pitch, high-volatile noncoking or semicoking coal, the benefits so gained have been comparatively small. There are no low or medium-volatile coking coals available within a reasonable freight-cost distance. Therefore a substitute for low-volatile coal was developed through low-temperature carbonization-or, more correctly speaking, through the partial devolatilization-of high-volatile coals. The blending of this lower volatile char with the high-volatile coking coal distinctly improves the quality of coke made from Colorado coal. There is nothing especially new about this idea. In 1908 a Japanese patent was taken out by Kotaro Shimomura, whose claim was: The method of making a nonfingery coke out of bituminous coals, without using natural coals of low-volatile matter; according to which a certain coal is heated at a temperature between about 300°C. and about 600°C. so as to leave about 15 to 25 per cent volatile matter in the coal; this coal is mixed with the

Jan 1, 1944

By Charles Parmelee

When Professor Silliman made his first examination of the newly-discovered Pennsylvania rock oil in 1859, he noted that different rates of heating produced different results in fractionation—longer heating produced larger percentages of light fractions. In 1862, it was found that when petroleum vapors are condensed in the still crown and dropped back into the hot liquid, the result of the distilling operation is materially modified. These early dates mark the beginning of what is called cracking petroleum and is explained as separating the component parts of the hydrocarbon molecules into more and smaller groups of the same elements. The phenomena were utilized for the next 30 years to increase the yield of burning oil. The procedure was that regularly practiced today in dry or destructive distillation. Considerable scientific study was given to the subject from 1862 to 1905, and a number of patents were obtained, but the work done was not continuous or intensive until about 1905, when the increasing demand for gasoline attracted attention of petroleum refiners to the possibilities of cracking. The first equipment built and operated essentially for cracking petroleum on a large scale was placed in successful operation in 1912. The commercial practice is, therefore, less than 15 years old. Comprehensive intense study of the controlling factors during this period has resulted in rapid increase in our knowledge, and material improvement has been made in the practice of the art. It is the purpose of this paper to outline briefly the state of our knowledge and to suggest some of the questions which are attracting attention of researchers at the present time. The major purposes for which petroleum hydrocarbons, including natural gas, are or have been cracked are: 1. To obtain products used to increase the heat value and illuminant content of artificial gas. 2. During the World War, to increase the supply of toluol. 3. To increase the amount of products capable of conversion into industrial chemicals. 4. To produce pure carbon.

Jan 1, 1927

By Henry A. Stiff, and Lawrence E. Davis

The authors previously presented a method for predicting the tendency of oil field waters to deposit calcium sulfate. The present paper gives a similar method for calcium carbonate. Methods for predicting calcium carbonate scaling tendencies in fresh waters have been available for some time, but these could not be used for brines. By experimentally deriving the value of the K term in the Langelier equation, a method has been developed which applies to waters of high salt content. A statistical study is included which shows that the experimentally derived values of K are in good agreement with actual conditions. Several applications of the final equation to production practice are given. INTRODUCTION The authors previously presented a method for predicting the formation of calcium sulfate scale in oil field waters.' Although calcium sulfate deposition is important in production operations, the majority of scale problems involve calcium carbonate. The present communication discusses a method by which the formation of this type of scale in oil field waters can be predicted. Calcium carbonate precipitation is caused by a shift toward carbonate in the carbonate-bicarbonate-carbon dioxide equilibrium. When equilibrium shifts in the other direction, the precipitate goes back into solution. Since there is usually considerable delay between the establishment of an equilibrium and the precipitation or solution of calcium carbonate, unstable conditions exist in which a water will precipitate or dissolve calcium carbonate on standing. Tillmans? who did a major part of the early work on carbonate scaling, pointed out that the condition of equilibrium not only indicates the tendency of a water to scale but also is an indication of its corrosive properties. Previously precipitated calcium carbonate combines with iron to form a dense crust which inhibits corrosion. If the water tends to dissolve carbonate, the scale becomes porous, and electrolytic corrosion takes place. Tillmans1 work was extended by several investigators until in 1934 Langeliers developed an equation setting forth the conditions of carbonate equilibrium. By the use of this equation the pH of a water at equilibrium can be calculated. If the actual pH is higher than the calculated pH, the water has a tendency to form scale. If it is lower. the water has a tendency to be corrosive. Langelier's equation can be expressed in a simple form as follows: SI = pH-pCa-pA lk-K where: SI is the stability index. A positive index indicates scale formation. A negative index indicates corrosion. pH is the pH of the water sample, as actually determined. pCa is the negative logarithm of the calcium concentration. pAlk is the negative logarithm of the total alkalinity. K is a constant, the value of which depends on the total salt concentration and the temperature. This equation has been shown to apply to waters with totaI solid concentrations as high as 4.000 ppm. In fact, control of fresh water treatment by means of this equation has been standard text-book practice for a number of years. Nomographs have been worked out so that the stability index of a fresh water sample can be determined in a matter of minutes. Most oil field waters, however, contain well over 4,000 ppm of salts and for this reason the usual application of Langelier's equation can not be made. By an empirical method we have extended the application of the Langelier equation to waters of high salt concentration. By the use of this equation the tendency of oil field waters to deposit calcium carbonate can be predicted.

Jan 1, 1952

By J. M. Hartman

ONE of the most important subjects to the blast-furnace engineer is a thorough knowledge of the conditions affecting the temperature in the different portions of the furnace. All efforts to decrease the consumption of fuel and improve the working of the furnace must be based upon it, and I may, therefore, be permitted to place before you the results of my observations, and detail the conclusions to which they have led me. Tracing the thermic conditions from below upwards we have at the bottom of a blast furnace making No. 3 iron a temperature of 2900° F., which increases slightly to a point a little below the tuyeres. In the immediate vicinity of the tuyeres the temperature is somewhat lower, owing to the entering blast ; but a short distance above the tuyeres, where all the oxygen of the blast has been converted into carbonic acid, the highest temperature in the furnace must be attained. This carbonic acid is, however, almost as soon as formed, converted by the glowing coal into carbonic oxide, a process which absorbs heat, reduces the temperature, and provides the active agent for the reduction of the iron ores. In its ascent the hot carbonic oxide gradually parts with its heat, first melting the descending iron and earthy materials, which drop down to the hearth of the furnace. The limit of this zone of fusion is rather sharply defined, and the temperature above this zone suddenly decreases. In its further ascent the hot gas drives off the carbonic acid from the limestone, which causes a further absorption of heat, and finally the gas escapes at the top, at a temperature of about 250° F. if the furnace is working well. These changes of temperature 1 have attempted to represent graphically,

Jan 1, 1880

President and Director GROVER J HOLT, '59, Ishpeming, Michigan Past President and Director CARL E REISTLE, JR, '58, Houston, Texas President-elect and Director AUGUSTUS B KINZEL '60, New York City Vice-Presidents and Directors W A DEAN, '58, Cleveland Ohio W W MEIN, JR, '58, San Francisco, Calif L E ELKINS, '59, Tulsa, Okla J L GILLSON,'59, Wilmington, Delaware E C BABSON, '60, Calgary, Alberta, Canada R V PIERCE, '60, Salt Lake City, Utah

Jan 1, 1957

By Mark R. Lamb

THE various methods of treating pulp in air-agitation tanks offer problems for experiment and study which are fascinating as well as practical. The usual method heretofore has been to fill each tank in turn, agitate the mixture the required period and then discharge the treated pulp into a storage-tank, from which it. is drawn to the filter as required. A later method is to run the pulp from the tube-mill, classifier, thickener, or settler into the first of a set of tanks, and thence continuously or in series through the remaining tanks, finally drawing off the pulp to a continuous filter, or to a pulp-storage tank if the filter is of the intermittent type. It is this method which I propose to discuss here in a preliminary way, with the idea of going exhaustively into the examination of the results of a series of experiments in a later paper. It may be of interest to note that the design of a cyanide-plant has recently been completed in which the estimated cost of the agitation-tanks, storage-tanks, and pumps was 30 per cent higher for the charge-agitation arrangement than for the series plan. The first question in studying the series method is, "What is the actual period of treatment undergone by the pulp?? One first supposes that by chance some of the pulp may get through with little or no treatment, while other portions may stay in the tanks a needlessly long period. The former is not probable or even possible, and the latter is, practically, true to only a limited extent. The greater the number of tanks the greater is the percentage of chance that all the pulp will be treated equally. Without going into the mathematical analysis of the problem (which is of little value, since it is based on problematical premises), its important terms may be clearly grasped by thinking of, or " visualizing," the conditions when,

Jan 1, 1910

By John Parker

During 1965, a new stoping method was developed at the Bunker Hill Mine at Kellogg, Idaho to enable the profitable mining of a large low-grade zinc orebody. This method, called the Bunker Hill pillar system, incorporates the use of the air-powered Atlas Copco T2GH or CAVO 310 as the prime production component. The method and equipment proved highly successful and was the first step in mechanizing what had been a classic example of a square-set and horizontal cut-and-fill operation. Since that time there has been a realization that the small rubber-tired type of loader could be effectively used to advantage in increasing productivity and decreasing costs in many different stoping and development applications throughout the mine. The net result since 1967 has been that a large and increasing portion of the mine production and an increasing share of the development is being done with small rubber-tired loaders. Presently, ten Atlas Copco T2GH and six CAVO 310 air-operated loaders are in use, having replaced the time-honored slusher which was first introduced into the Bunker Hill Mine in about 1898 in the form of a slip scraper. The recent advent of diesel powered loaders in the one yard size range has in 1970 further accelerated the trend toward rubber-tired mobile equipment at the Bunker Hill Mine. Although The Bunker Hill Company is using small diesel loaders of several different types and manufactures for inclines, declines and level development and will undoubtedly find stoping applications for this equipment, .the bulk of this paper will be confined to the use of the air-operated loader, leaving the diesel equipment to a future presentation. It is sufficient to say that we feel at this time that the Autoloader type air-powered equipment and the small diesel front end-loader

Jan 1, 1970

By A. M. Gaudin

A great number of hypotheses has been advanced to explain the complex phenomena that are encountered in flotation. In the days of bulk-oil flotation, when a large quantity of oil was employed, it was observed that the oil-mineral aggregate floated above the ore-pulp because of its lesser density. With the advent of froth-flotation this phase of the theory had to be modified to take into account the presence of air bubbles. The reason why the mineral-bearing froth of today rises to the top of flotation cells is, of course, because the air-mineral aggregate, with whatever reagent may be associated with it, is lighter than the pulp. In an attempt to explain froth-flotation the fact has been emphasized that certain minerals are wetted and therefore remain in water; while others are not wetted and therefore become associated in preference with air. Such an "explanation" does not explain facts, it merely states them; for instance, it does not explain why minerals are wetted under some circumstances and not wetted under others. Going somewhat further, the wetting or nonwetting of minerals by water has been ascribed' to differences in the angles of contact between oil droplets and mineral surface at the surface of the minerals. This explanation, however, was abandoned when soluble flotation reagents came to replace the so-called "insoluble" reagents. Another theory, sponsored about 10 years ago by Ralston,² involves the effects of electric charges at the surface of the mineral particles and air bubbles. This theory, unfortunately, was not developed as fully as it seems desirable. The belief that adsorption phenomena might play a preponderant role in flotation3 has been rather widespread for the last 10 years. Unfor-

Jan 1, 1928

By Richmond Bennett

Airborne geochemistry became a reality with the advent of a high-sensitivity air¬borne gamma ray spectrometer with large volume NAI(Tl) crystal detectors. The high-sensitivity spectrometer measures small variations in the concentration of potassium (as Ks°), thorium (as Tl308) and uranium (as Bi.214) along the flight lines in the area surveyed. Hydrothermal dispersion patterns are indicated by anomalous measured values of the concentrations of potassium, thorium, uranium, or their ratios. In two recent Australian survey areas, copper mineralization was located along favorable structures within hydrothermal dispersion patterns delineated by airborne geochemical surveys. In metamorphic terrane where there had been po¬tassium metasomatism, the hydrothermal dispersion patterns were indicated by high potassium/uranium ratios (K40/Bi). In a sedimentary environment that had been intruded by a stock, the path of hydrothermal fluids was indicated by uranium (Bi214), thorium (TV'), and uranium/ thorium (Bi214/Tl208) ratios.

Jan 1, 1972

By Donald F. Kennedy

During the past several years Climax Molybdenum Co. has been engaged in testing various types and sizes of hollow drill steel. The majority of tests have been on 7/8-in. hexagon st.ee1, inasmuch as it represents approximately 70% of total drill steel consumption at the Climax operation. Prior to December 1960, tests on 7/8-in. hexagon drill steel were conducted on steel with a forged collar and, in most cases, with a threaded bit connection. Through these tests and research, some improvement in steel life was achieved by making changes in heat treatment, design and alloying constituents. However, during that month, research and testing commenced on a rubber collar which was designed to replace the forged collar on 7/8-in. hexagon drill steel. Manufactured by the LeRoi Div. of Westinghouse Air Brake Co.. the collar. is very simple in design, consisting of a 1 ½ -in. diam steel cylindrical sleeve 2 in. long, containing a bonded rubber insert and attached to the steel with an epoxy cement

Jan 8, 1962

Jan 1, 1953

By G. W. Tower

THE YEAR 1931 was for most American copper producers one of restricted output but extremely low production cost.. When compared with 1929, the marked reductions in costs achieved in 1931, operating at rates in many instances a third to a half of capacity, can only be regarded as remarkable. In fact, the recent shut-down of several large operations suggests the probability that 1931 costs represent a bare minimum for many properties. Before discussing the 1931 results a few remarks on cost data are appropriate. The type of cost tabulation here presented was first published in 1929, (A. B. Parsons. E. & M. I. June 8, 1929), and has appeared each, succeeding year following in general the calculation method and company set-up of the original article. (. G. W. Tower, E. & III. L, July 8. 1930; S. D. Strauss, E. & M. J.; July 27, 1931). As far as possible the leading American copper companies are included. In considering these cost tabulations it must be borne in mind that the information from which they have been prepared is entirely contained in the annual report of each company; and that a multiplicity of interests and a condensed income statement for some of the larger companies, such as Cerro de Pasco and Kennecott, make the cost figure an arbitrary one depending upon sundry metal credits, metal products, miscellaneous income, etc. For Granby, Howe Sound. Magma, and Noranda, sundry metal credits are important. Furthermore Andes, Chile and Greene Cananea give costs only against copper sold. Although the individual costs here figured are by no means absolute they are computed by the same method each year and offer a basis of annual comparison; and with attention to footnotes the premises on which the costs are based may be easily followed.

Jan 1, 1932

By Kiyoshi Azuma, Hiroshi Kametani

The variation of the dissolution behavior of a ferric oxide with calcining temperature has been investigated. Samples were prepared by thermal decomposition of ferric hydroxide, nitrate, oxalate, and sulfate at low temperature, followed by the calcination in the temperature range between 600" and 1200°C. The samples of eight series and a fine crystalline sample of hematite were dissolved in 1 N hydrochloric acid at 55.2°C and the results are represented on double-log graphs for convenience. It is confirmed that all dissolution courses follouj either the accelerated process or the parabolic process except in the special case of the crystalline hematite which dissolced in accordance with the uniform dissolution of a particle. Examinations of the physical properties of the oxide powders revealed that the surface area measured by the permeability method is strikingly relevant to the dissolution behavior of the oxide. In the previous paper,' detailed data were presented on the effect of the kind of acid, the solution temperature, and the concentration of acid on the dissolution of two ferric oxides. It was also shown that these sam ples dissolved in strikingly different ways. The present investigation was carried out on the dissolution of various calcined samples prepared from various ferri salts by various methods to ascertain the course of dissolution. Pryor and Evans2 pointed out a change of the dissolution rate at around 700°C for a series of calcined ferric oxides prepared from the hydroxide. Several papers374 reported also the dissolution of ferric oxide samples. It seems, however, that a systematic account of the relationship between the dissolution behavior and physical properties of the oxide has not yet been given. This paper presents the variation of the dissolution of the oxide in relation to the calcining temperature and the change of physical properties of the calcines. EXPERIMENTAL Raw materials were prepared by precalcination of ferric hydroxide, thermal decomposition of ferric nitrate, oxalate, and sulfate, and aerial oxidation of ferric chloride vapor, at as low a temperature as possible. The products were crushed, ground, if necessary, and sieved with a 100-mesh Tylor screen prior to calcination, after which the specimens were dissolved in acid solution. The following is a detailed description of the preparation of the samples. Sample H. About 500 g of ferric chloride (guaranteed reagent) were dissolved in 5 liters of deionized water and filtered. Ferric hydroxide was precipitated by addition of the minimum amount of ammonium hydroxide solution, and the precipitate was washed continuously till chloride ion was not detected by silver nitrate solution, and then filtered. The filter cake was dried at 120°C for a week and ground, and the -100 mesh portion was used. Sample S. Ferric sulfate (guaranteed reagent) was pyrolytically decomposed in a crucible at 700°C for 24 hr and the product was sieved. In this case the following calcination was carried out at temperatures over 700°C. Sample B. Commercial ferric oxide (guaranteed reagent). About 15 kg of ferric nitrate were decomposed in a furnace maintained at 800°C for 2 hr. The actual temperature of the decomposition was not measured. The product was crushed and sieved, and the -100 mesh portion was used. Sample N. About 50 g of ferric nitrate (guaranteed reagent) were decomposed in a beaker in a sand bath until a red-brown dense solid was produced. This product was crushed and sieved, and subjected to complete decomposition at 500°C. The precalcined product was again sieved and used. Sample N2.5. Since the decomposition temperature was not controlled for sample AT, a different sample was prepared in a temperature-controlled furnace. The subscript represents the decomposition at 250°C. The product was treated in the same manner as sample N. Sample Nc. Under atmospheric pressure it is prac-tically inevitable that ferric nitrate hydrate melts to form a brown liquid at about 50°C before pyrolysis. For this reason, the salt was first slowly heated under reduced pressure (about 10-3 mm Hg measured in a trap refrigerated by dry ice-alcohol) to achieve dehydration without melting. About 5 hr were required for the dehydration and the partial decomposition. Then the temperature was elevated to 500° C in air for complete decomposition. The relatively porous product was sieved and used. Sample Ov. About 200 g of ferric oxalate hydrate (extra pure) were dehydrated under reduced pressure (as described above) followed by thermal decomposition at 500°C for 6 hr in air. The decomposition of this salt was accompanied by liberation of carbon monoxide, by which the ferric salt was initially reduced to a black powder. The powder changed in turn into brown ferric oxide as the gas liberation decreased and reoxidation predominated. The product consisted of sparkling fine particles passing through a 100-mesh screen. However it was ground and sieved as for the other samples. Sample D. Commercial fine powder for magnetic tape purposes. The preparation was as follows.5 Ferric chloride vapor and preheated excess air were mixed and passed into a reaction tube where oxidation took place at 450°C. The fine powder formed was collected in a cottrell chamber. The product was vacuum-degassed at 450°C for 1 hr and sieved.

Jan 1, 1969

By Carle R. Hayward

GENERAL conditions in the lead industry have registered a distinct improvement. The first signs of a strengthening market were found in an increasing demand for scrap. There is keen competition for old battery plates both by large and small dealers. The large operator smelts them either alone or in combination with ores or other lead-bearing material, giving an antimonial lead for which there is brisk demand. The small operator usually has three alternatives. He may simply melt out the metallics in a kettle at low temperature, giving an antimonial lead and a pulverulent lead oxide; he may fuse under oxidizing conditions, giving a soft lead and lead-antimony slag; or he may fuse under reducing conditions, giving a relatively low-grade antimonial lead and a low-antimony slag. In each case the metal product is used or sold, and the dross or slag sold to a large smelter. It will be interesting to see what the final outcome will be of this situation which is generally conceded to be unsatisfactory.

Jan 1, 1937

By Tracy Jarrett

IN making gold alloys possessing certain physical properties, such important factors as corrosion resistance, color, hardness and melting points must be considered. All of these requirements depend directly upon the composition. It is possible to obtain the same colored gold alloy by using different compositions, but in doing so one may bring in some undesirable property. Other investigations have been carried on in this field by F. E. Carter,1 E. M. Wise,2 and L. Sterner-Rainer.3 To make a complete study of the effect of composition upon these properties, a systematic investigation was carried on involving a range of copper content from 85 to 65 per cent. Elements such as zinc, silver and nickel were used to replace in part the copper content. The gold content in all the alloys remained constant. Only 10-karat gold alloys of those containing 41.6 per cent gold will be considered. All of the alloys were made in an induction furnace. Each alloy was cast in a 3 by ¼ by ¾ -in. ingot. The method of obtaining the melting points and making color determinations was described in a previous paper.4 The Rockwell B scale with the ball and 100-kg. weight was used for all hardness determinations. The submersion of test pieces in concentrated nitric acid is one of the standard corrosion tests used in the optical trade. A test piece in the 50 per cent cold-worked condition, ½ by 2 by 0.043 in., is blanked from a strip using a. die, and the weight, loss per square inch of surface is taken as a means of comparison. The time for this test is 2 ½ hr. of actual sub-mersion of the test piece in the acid. This standard test was applied to all of the 10-karat gold alloys discussed in this paper. The tensile tests were made upon strips of the dimensions shown in Fig. 1. The test pieces after blanking were annealed at 1300° F. for 20 min. and cooled in air. The "drop of the beam" method was used in determining the yield point, as there was a very marked "drop" when the yield point was reached.

Jan 1, 1939

By Tracy C. Jarrett

In making gold alloys possessing certain physical properties, such i~nportant factors as corrosion resistance, color, hardness and melting points must be considered. All of these requirements depend directly upon the composition. It is possible to obtain the same colored gold alloy by using different compositions, but in doing so one may bring in some undesirable property. Other investigations have been carried on in this field by F. E. Carter,' E. M. Wise12 and L. Sterner-Rainer2 To make a complete study of the effect of composition upon these properties, a systematic investigation was carried on involving a range of copper content from 85 to 65 per cent. Elements such as zinc, silver and nickel were used to replace in part the copper content. The gold content in all the alloys remained constant. Only 10-karat gold alloys of those containing 41.6 per cent gold will be considered. All of the alloys were made in an induction furnace. Each alloy was cast in a 3 by 1/4 by 3/4-in. ingot. The method of obtaining the melting points and making color determinations was described in a previots paper.4 The Rockwell B scale with the 1/16-in. ball and 100-kg. weight was used for all hardness determinations. The submersion of test pieces in concentrated nitric acid is one of the standard corrosion tests used in the optical trade. A test piece in the 50 per cent cold-worked condition, % by 2 by 0.045 in., is blanked from a skip using a die, and the weight loss per square inch of surface is taken as a means of comparison. The time for this test is 2 1/2 hr. of actual submersion of the test picce in the acid. This standard test was applied to all of the 10-karat gold alloys discussed in this paper. The tensile tests were made upon strips of the dimensions shown in Fig. 1. The test pieces after blanking were annealed at 1300" F. for 20 min. and cooled in air. Thc "drop of the beam" method was used in determining the yield point, as there was a very marked "drop" when the yield point was reached.

Jan 1, 1940

By Tracy C. Jarrett

In making gold alloys possessing certain physical properties, such i~nportant factors as corrosion resistance, color, hardness and melting points must be considered. All of these requirements depend directly upon the composition. It is possible to obtain the same colored gold alloy by using different compositions, but in doing so one may bring in some undesirable property. Other investigations have been carried on in this field by F. E. Carter,' E. M. Wise12 and L. Sterner-Rainer2 To make a complete study of the effect of composition upon these properties, a systematic investigation was carried on involving a range of copper content from 85 to 65 per cent. Elements such as zinc, silver and nickel were used to replace in part the copper content. The gold content in all the alloys remained constant. Only 10-karat gold alloys of those containing 41.6 per cent gold will be considered. All of the alloys were made in an induction furnace. Each alloy was cast in a 3 by 1/4 by 3/4-in. ingot. The method of obtaining the melting points and making color determinations was described in a previots paper.4 The Rockwell B scale with the 1/16-in. ball and 100-kg. weight was used for all hardness determinations. The submersion of test pieces in concentrated nitric acid is one of the standard corrosion tests used in the optical trade. A test piece in the 50 per cent cold-worked condition, % by 2 by 0.045 in., is blanked from a skip using a die, and the weight loss per square inch of surface is taken as a means of comparison. The time for this test is 2 1/2 hr. of actual submersion of the test picce in the acid. This standard test was applied to all of the 10-karat gold alloys discussed in this paper. The tensile tests were made upon strips of the dimensions shown in Fig. 1. The test pieces after blanking were annealed at 1300" F. for 20 min. and cooled in air. Thc "drop of the beam" method was used in determining the yield point, as there was a very marked "drop" when the yield point was reached.

Jan 1, 1940