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By Oscar Weiss

An aerial magnetometer survey was carried out by the author's geophysical organization over the Vrede-fort dome, where Witwatersrand beds are wrapped around a granite plug 25 to 30 miles in diameter. The well-known magnetic shales of the Lower Witwatersrand system (to be referred to as LWW) give strong negative anomalies over the out-cropping portion of the dome. This is unusual as these same shales cause positive anomalies over large areas near Johannesburg and along a strike of 130 miles between the East Rand and Klerksdorp. It is suggested that the negative polarization is caused by heat and stresses connected with the doming. This negative polarization of sedimentary beds, which usually cause positive anomalies, is a good example of how "magnetic lows" can be caused by "structural highs." Significant magnetic anomalies should be tested by gravity and seismic methods irrespective of the sign of the anomalies. South of the line X — Y (see Fig 2 and 5) the gravity anomalies are smaller over the LWW beds and magnetic anomalies suddenly become weaker and even change signs by becoming positive. This peculiar phe- nomenon is explained by faulting which truncated the nearly vertical LWW shales at depth. In this manner the mass of the LWW beds has been reduced together with the weakening of the negative magnetic anomalies by positive poles which occupy the truncated end. Furthermore, by uplifting the beds between f1 and f2 (Fig 2) positive polarization becomes predominant, thus causing positive magnetic anomalies. General The Vredefort dome is one of the internationally known geological structures, which, among others, has attracted the attention of numerous American geologists. It was for this latter reason that our aerial magnetic results over this structure were selected by us for publication in the United States of America. A full description of the exposed geology has been published by Nell and readers are referred to this paper, which is subject to only slight modifications inasmuch as the subdivision of the Witwatersrand system (to be referred to as WW system) is concerned. The Vredefort dome is about 60 miles southwest of Johannesburg. The WW system, after being exposed in the vicinity of Johannesburg, plunges with southerly dips beneath the Vent-ersdorp and Transvaal systems. Along a section southwest from Johannesburg, as shown diagrammatically in Fig 4, we see no outcrops of the WW system until the Vredefort dome, where the Upper and Lower WW system are wrapped around an almost circular arc of a granite mass. Here the whole WW system is overturned around the perimeter of a huge granite plug 25 to 30 miles in diameter. Less than half of the circumference of this dome is exposed; the rest is covered by Karroo dolerites and sediments. The determination of the exact shape of the concealed part of the dome has been a matter of considerable interest and obviously geophysical methods were eminently suited for obtaining this information. A good start was made with a gravimeter survey carried out by the Geological Survey of the Union of South Africa.2 Our own

Jan 1, 1950

By Norman Patton

THE subject assigned is so broad that thorough discussion is well-night impossible within the space allotted, and further, few specific data are available upon which to predicate conclusions concerning the efficiency of present methods of distributing anthracite. This paper treats briefly the various agencies through which both primary and secondary distribution are effected, the methods of transportation and the general interrelation of production, demand, inventories and price. AVENUES OF DISTRIBUTION "Three distinct types of primary distribution are common in the marketing of anthracite. First, though not most important, is the sale by the producer, or operator, direct to the consumer. These sales, other than to employees and the local trade, are generally confined to steam sizes for industrial uses, and are consigned to the sidings or docks of the consumer. Sales of this type often are so closely priced to compete with oil and bituminous that the addition of even a small dealer's margin is sufficient to increase the cost to the point where the business might be lost. Second, the operator sells to a wholesaler or broker for subsequent resale, either to a retail dealer for clearance through his yard or direct to large consumers. Usually this method of distribution is employed by the smaller operators, who do not find it economically feasible to maintain extensive sales organizations. In most instances, the wholesaler retains some 5 per cent for his services, paid, of course, by the producing company whose anthracite he handles. He may, and frequently does, handle the output of several different companies, suited to the varying needs of the

Jan 1, 1935

By John A. Prof. Church

ONE of the most striking phenomena connected with the mines on the Comstock lode is the extreme heat encountered in the lower levels. This heat is not due to the burning of candles, heat of the men, and decomposition of timbers, all intensified by bad ventilation, as was the case nearer the surface. It proceeds from the rock, which maintains constantly a temperature very much higher than the average of the atmosphere in Nevada. The heat of these mines is a matter of more than usual interest, for they are the only hot ones now worked in the United States, and both in the present temperature encountered and in the increase which is to be expected as greater depths are reached, they appear to surpass any foreign mines of which we have a record. Hot mines are known also in other countries, as in the tin and copper lodes of Wales, where one of the veins worked by the United Mines is known as the hot lode. It has springs which discharge water at a temperature of 116° Fahrenheit, the depth being 220 fathoms, or 1320 feet. The heat of the air in these workings is given at 100° to 113° Fahrenheit. The air is bad, and the heat in the drifts seems to be traceable to defective ventilation rather than to the real necessities of the case. Air is supplied through a small pipe, and is drawn from a place where the temperature is 95° Fahrenheit. Under such circumstances it is not surprising to read that in this hot mine the air is hotter than the rock, a state of things which I have never observed in the Comstock. Other mines have been reported to the British Coal Committee as having temperatures of 106° Fahrenheit and thereabouts, but the only positive comparisons that are available at this writing are the following, all from Cornish mines * Read by permission of Lieut. Geo. M. Wheeler, Corps of Enginerrs, U. S. Arm J, in charge of U. S. Geographical and Geological Surveys, west of the 100th meridian.

Jan 1, 1879

By B. M. Larsen, W. E. Shenk

THIS paper describes a method of reversal control of the open-hearth furnace that obtains in practice those effects considered below as essential to a completely automatic control, without appreciable interference with the natural rise and fall in temperature of the regenerative portions of the furnace system. Growing out of some studies of radiation pyrometry in open-hearth regenerators, it was developed during 1934-1938, and has been successfully applied to a number of commercial furnaces. The goal of open-hearth furnace operation is the highest rate of production of steel of proper quality consistent with good refractory life and fuel economy. This requires rapid heat transfer from furnace to charge, which in turn is dependent upon heating the furnace refractories to the highest safe operating temperature. The greater the heat input to the melting chamber, the sooner this limiting temperature will be reached, so that control methods in general that are designed to protect against overheating of refractories should help to maintain maximum fuel input and production rate. For the typical open-hearth system, with fixed regenerator capacity and with rate of fuel input usually restricted in its range of variation, our basic assumption is the idea that the only other important variable that is, the time interval between successive reversals-should also be held constant or within a small range. The present reversal control was designed therefore so that, under normal operating conditions, no arbitrary limitation is imposed other than to keep the reversal interval within the optimum time range. However, since a near approach to completely automatic operation involves protection of refractories through the balancing of furnace end temperatures as well as emergency protection against temperature peaks above some upper limit, it was also felt essential to employ, as an integral part of the control unit, a temperature-measuring instrument to register the true temperature of the refractory surfaces at some critical region in the hot ends of the regenerative zones. As the basic elements of the control, we thus have one "maximum" and one "minimum" time relay and a potentiometer recorder-controller, combined with switches and relays to operate as follows: x. Reversal normally occurs within an optimum range limited by the maximum and minimum settings to about 4 to 6 min. variation, but the actual interval usually is less variable and closer to the minimum setting. 2. The margin between minimum and maximum time is utilized, together with a "floating temperature limit" in the potentiometric control instrument, to correct any

Jan 1, 1945

By G. G. Gunther, C. L. Boeke

THE zinc deleading processes at the Parral and Santa Barbara mills are described separately to provide a basis for comparison. Although the two procedures are fundamentally alike, there are some differences in application to meet specific conditions. The Asarco mill at Parral in the State of Chihuahua is a flotation plant treating 1450 metric tons per day of complex sulphide copper-lead-zinc ores. In general, the procedure used for selective separation of the minerals into a copper, a lead, and a zinc concentrate follows the usual practice. First, a bulk copper-lead concentrate is floated and then separated into a final copper and a final lead concentrate by the sulphurous acid process. A small tonnage of high grade gravity lead concentrate is tabled from the bulk copper-lead cleaner tailing before it is reground so as to avoid undesirable over-grinding and sliming of this portion of the lead mineral. Next, a zinc concentrate is floated from the lead rougher tailing and, as described later, is separated into a final lead product and a final zinc concentrate. Finally, the zinc rougher tailing receives a strong scavenger float to remove all recoverable middling values for regrinding and return to the flotation circuits. The slime is separated from the scavenger flotation product, and only the sand portion goes to the regrind section. The minerals in the separated slime are extremely resistant to all methods of selective separation and pose one of the major problems awaiting solution. Nevertheless, the slime shows a profit when mixed with either the lead or the zinc concentrate, except when metal prices are very low, so it is accepted as a final product for lack of a more profitable method of handling it. In contrast, the minerals in the reground sands of the

Jan 1, 1953

By G. G. Gunther, C. L. Boeke

THE zinc deleading processes at the Parral and Santa Barbara mills are described separately to provide a basis for comparison. Although the two procedures are fundamentally alike, there are some differences in application to meet specific conditions. The Asarco mill at Parral in the State of Chihuahua is a flotation plant treating 1450 metric tons per day of complex sulphide copper-lead-zinc ores. In general, the procedure used for selective separation of the minerals into a copper, a lead, and a zinc concentrate follows the usual practice. First, a bulk copper-lead concentrate is floated and then separated into a final copper and a final lead concentrate by the sulphurous acid process. A small tonnage of high grade gravity lead concentrate is tabled from the bulk copper-lead cleaner tailing before it is reground so as to avoid undesirable over-grinding and sliming of this portion of the lead mineral. Next, a zinc concentrate is floated from the lead rougher tailing and, as described later, is separated into a final lead product and a final zinc concentrate. Finally, the zinc rougher tailing receives a strong scavenger float to remove all recoverable middling values for regrinding and return to the flotation circuits. The slime is separated from the scavenger flotation product, and only the sand portion goes to the regrind section. The minerals in the separated slime are extremely resistant to all methods of selective separation and pose one of the major problems awaiting solution. Nevertheless, the slime shows a profit when mixed with either the lead or the zinc concentrate, except when metal prices are very low, so it is accepted as a final product for lack of a more profitable method of handling it. In contrast, the minerals in the reground sands of the

Jan 1, 1953

By M. E. Wadsworth, D. R. Wadia

The rate of reaction of cuprite was measured in a series of sulphuric acid solutions, from which oxygen had been excluded, at various concentrations and temperatures. The overall reaction CuzO + H2S04 + Cu " + CuO + H20 + So4' may be explained quantitatively by two simultaneous rate reactions involving not only H+ but also the hydrolytic adsorption of H2SO4. The results indicate the importance of considering surface mass balance relationships associated with heterogeneous surface reactions. T EACHING has long been an important method for the recovery of metals from certain minerals. Many processes have assumed minor importance in modern practice but such operations as the recovery of uranium and present interest in high pressure-high temperature solution of sulphides' ' well illustrate the importance of leaching as a unit operation. Little quantitative information is available in a form sufficient to determine the mechanism of solution at the solid-aqueous solution interface for given systems. For this reason, it is important that fundamental studies of leaching processes be conducted so that parameters associated with such surface reactions may be understood and correlated. Cuprite was chosen for this study as a result of a recent investigation carried out at the University of Utah on ores of the Ray and Chino Mines Divs. of the Kennecott Copper Corp. These sulphide deposits contain sufficient oxidized minerals, such as cuprite, malachite, and azurite, so that recovery of metal values contained in the oxidized fraction is of primary interest. Of these oxides, cuprite (Cu,O) is the most interesting, since it dissolves in sulphuric acid by an oxidation reduction couple resulting in the formation of 50 pct metallic Cu and 50 pct cup-

Jan 1, 1956

By M. C. Leverett

Knowledge of the theory underlying the behavior of mixtures of fluids in reservoir rocks is essential to the proper solution of certain types of problems in petroleum production, but is as yet incompletely developed. The object of this paper is to show the application of well established thermody-namic and physical principles to these problems, and thus to assist in the development of the basic theory. For convenience the problems to be considered here may be divided into two groups: 1. Static problems, involving only the static balance between capillary forces and those due to the difference in densities of the fluids; i.e., gravitational forces. 2. Dynamic problems, involving analysis of the motion oi mixtures of immiscible fluids in porous media under the influence of forces due to gravity, capillarity, and an impressed external pressure differential. Capillary Equilbrium in Sands Under this heading the static type of problem will be discussed and the results of experimental investigations on the capillary properties of unconsolidated sands will be presented. Although the discussion of this section is, in a sense, prefatory to the treatment of problems of mixture flow, the concepts developed here have considerable intrinsic importance apart from their ap-plication to flow problems. For, it is reason-able to postulate that the reservoir fluids are, owing to their long existence in undis- turbed mutual contact prior to exploitation, in substantial equilibrium. It follows that their distribution in the reservoir at the time of tapping should be entirely predictable from the theory of capillary equi librium, provided certain experimentally measurable properties of the reservoir rock are known. Knowledge of the distribution of the several fluids in the reservoir is, ol course, helpful in the estimation of reserves and in other problems. It is to be emphasized that throughout the discussion of capillary statics it is assumed that the fluids are in equilibrium from the capillary standpoint. Thus, water, where it is referred to as being in a reservoir, will be understood to be interstitial water, present at the time of drilling the reservoir, commonly termed "connate" water. The theory developed here is perfectly general for any porous solid, whether a carefully prepared unconsolidated sand or a natural sandstone from an oil reservoir. At present, however, only problems involving clean, unconsolidated sands can be made to yield numerical solutions, since only such sands have been adequately investigated experimentally. Experimental evaluation of the pertinent properties 01 natural reservoir rocks will permit the extension of the numerical treatment to problems involving these materials. We shall now consider in some detail the static equilibrium of fluid mixtures in porous solids: that is, the manner in which the reservoir fluids are distributed vertically whell the Forces due to capillarity are just balanccd by those due to gravitation.

Jan 1, 1941

By M. C. Leverett

Knowledge of the theory underlying the behavior of mixtures of fluids in reservoir rocks is essential to the proper solution of certain types of problems in petroleum production, but is as yet incompletely developed. The object of this paper is to show the application of well established thermody-namic and physical principles to these problems, and thus to assist in the development of the basic theory. For convenience the problems to be considered here may be divided into two groups: 1. Static problems, involving only the static balance between capillary forces and those due to the difference in densities of the fluids; i.e., gravitational forces. 2. Dynamic problems, involving analysis of the motion oi mixtures of immiscible fluids in porous media under the influence of forces due to gravity, capillarity, and an impressed external pressure differential. Capillary Equilbrium in Sands Under this heading the static type of problem will be discussed and the results of experimental investigations on the capillary properties of unconsolidated sands will be presented. Although the discussion of this section is, in a sense, prefatory to the treatment of problems of mixture flow, the concepts developed here have considerable intrinsic importance apart from their ap-plication to flow problems. For, it is reason-able to postulate that the reservoir fluids are, owing to their long existence in undis- turbed mutual contact prior to exploitation, in substantial equilibrium. It follows that their distribution in the reservoir at the time of tapping should be entirely predictable from the theory of capillary equi librium, provided certain experimentally measurable properties of the reservoir rock are known. Knowledge of the distribution of the several fluids in the reservoir is, ol course, helpful in the estimation of reserves and in other problems. It is to be emphasized that throughout the discussion of capillary statics it is assumed that the fluids are in equilibrium from the capillary standpoint. Thus, water, where it is referred to as being in a reservoir, will be understood to be interstitial water, present at the time of drilling the reservoir, commonly termed "connate" water. The theory developed here is perfectly general for any porous solid, whether a carefully prepared unconsolidated sand or a natural sandstone from an oil reservoir. At present, however, only problems involving clean, unconsolidated sands can be made to yield numerical solutions, since only such sands have been adequately investigated experimentally. Experimental evaluation of the pertinent properties 01 natural reservoir rocks will permit the extension of the numerical treatment to problems involving these materials. We shall now consider in some detail the static equilibrium of fluid mixtures in porous solids: that is, the manner in which the reservoir fluids are distributed vertically whell the Forces due to capillarity are just balanccd by those due to gravitation.

Jan 1, 1941

By G. S. Brooks

WITH the gradual depletion of the natural-gas pools of the Kansas district, together with the uncertainty of further cheap fuel developments, some. of the western zinc companies turned to the coal fields, attracted by their permanency and the 'success of the Matthiessen & Hegeler Co. and the Illinois Zinc Co. Being then confronted with the problem of using a relatively high-priced fuel, although the ultimate' supply was very great, the fuel economies of the kilns and furnaces became of far more importance, and the more modern equipments, as a result, embodied distinct gads in this phase of the business. In addition, there have been some pronounced advances in the actual making of gas from these coals. Increased efficiency in gas making has contributed its share to lowering costs and those plants located in the higher priced fuel districts have probably been obliged to study these economies somewhat more closely. Naturally, many beneficial changes have resulted in both practice and apparatus in these sections. On, certain western coals, for instance, the actual saving in fuel consumption has been 50 per cent. By this is meant that, where about 1.75 tons were burned to smelt 1 ton of oxidized ore, 0.7 to 0.9 ton is now required. While comparisons by W. R. Ingalls1 of fuel economies in smelting in this country and Germany before the war may, in general, be correct, they do not appear to-do justice to the more progressive. American practice. It is doubtful whether German plants were substantially bettering these fuel ratios. Data furnished by Bender and Frams do not afford records averaging less than 0.9 ton coal per ton ore on materials from 40 per cent. to 50 per cent. zinc.

Jan 9, 1919

By C. A. O’Malley, F. W. Kinsey

This paper deals with an experimental study in the use of a preagglomerated burden as a means of increasing the production of sinter. The effect of a wide range of sinter burden was studied, including concentrates produced by a flotation process. Some of the important characteristics of a sinter bed are discussed along with the strength and reducibility of the sintered product. In recent years the use of sinter in blast furnaces has become increasingly important across the country—largely because of the demand for more hot iron from existing plant capacity and the increasing amount of fines in the burden materials available to the blast-furnace operator. In many instances, unfortunately, the demand for sinter has been so great that little time has been available to give the proper

Jan 1, 1960

By E. J. Duggan

THE mine and mill of the Climax Molybdenum Co. are at Climax, Colorado. Climax is on Fremont pass directly on the Continental Divide, at an elevation of 11,400 feet. DESCRIPTION OF ORE The Climax ore-bearing rock is essentially an altered and highly silicified granite, fully half of the gangue being quartz. Molybdenite is the only mineral of economic consequence and most of it is intimately associated with quartz in the form of fine veinlets and stringers. Other minerals are molybdite, pyrite, and chalcopyrite. While the molybdite may be readily extracted by hydrometallurgical methods, its content is too low to make such operations profitable. The pyrite content ranges from 2 to 5 per cent and that of the chalcopyrite from 0.03 to 0.05 per cent. There is not enough copper to make its recovery attractive and one of the metallurgical problems is the elimination of it and the pyrite from the product. On account of the dose association of the molybdenite with the quartz and the necessity of eliminating the pyrite and chalcopyrite from the final product, fine grinding followed by flotation is the only feasible method of concentration. HISTORY Construction of the first milling unit was started in 1917 and it was operated during parts of 1918 and 1919. In the postwar years, there was almost no demand for the product and production was at a standstill until 1924. The Company's research campaign to develop the use of the metal began to show results in that year. From 1926 to 1932 production ranged from 500 to 1200 tons per day. In 1931 an additional mill section was built and production was gradually increased until in 1934 and' 1935 about 3000 to 4000 tons was milled per day. This tonnage overtaxed the milling facilities, and as the demand for molybdenum was growing constantly, additional milling equipment was needed. In 1936 and 1937 another crushing plant, six additional mill sections and the necessary auxiliary plants were constructed and brought into operation. This plant was designed to mill 10,000 tons per day, but it was not long before 12,500 tons was being treated during periods of peak demands. During the summer of 1941, to meet defense needs, the mill has been required to treat 15,500 tons per day. This has been accomplished with little plant expansion and at no loss in recovery, as will be described later. To increase capacity still further, one more primary section is now being built. This will bring capacity to 18,000 tons per day, which can be stretched to 20,000 tons at a small sacrifice in recovery. CRUSHING There are two crushing plants: No. I, of 5000 tons capacity (flowsheet in Fig. 1) and No. 2, of 15,000 tons capacity (Fig. 2).

Jan 1, 1942

By Luther Lennox

THE purpose of this article is not to compare one type of grinding machinery with another and to conclude from a series of tests that one particular machine is superior to all others. Neither is the reader asked to tire himself with the details of many tests to prove the statements herein made. The Chilean mill stands today almost, in outcast from the milling world. It ranks with the applicant for a job who has been given a trial along with others and condemned because he was not able to perform the definite task assigned as well as the others, and was forever eliminated. The judges did not tarry long enough to try this aspirant in a field of a slightly different nature. Even though it has been condemned, the writer contends that the published records will indicate that the trials were never shifted into the field of greatest efficiency for the Chilean mill. Those of us who cling to this outcast as a fine grinder in our milling operations do not wish, naturally, to be condemned along with the machine, and yet we feel that we are classed as behind the times, at least in this phase of our milling judgment. Hence there is considerable personal feeling in our efforts. During the last few years there have been published several papers on the relative merits of the various grinding machines. In two of these articles a comparison was made between Chilean mills and cylindrical grinders. In each case the Chilean mill came out second best from about all standpoints. The outstanding feature in these comparisons would seem to be the decided attempt to keep all conditions the same, so that each machine could be judged on its merit. As Mr. David Cole states, "We are inclined to regard a direct comparison of grinders arranged side by side, and making a product that affords as nearly as possible the same screen measure, as the Supreme Court in these grinding matters." The writer agrees that this is the very best method for true comparison between machines. The results in the two detailed tests should give the relative merits of the two grinders in doing the work assigned. And they probably do. The conclusion drawn in each case was adverse to the

Jan 9, 1919

By W. H. Bassett, C. Davis

Although brasses and bronzes have been made for ages, a systematic study of their physical properties has been carried out only during the years of the present century. Among these properties may be included those which are to be detected by means of microscopic examination; in other words by the science of metallography. The earlier workers in this field, both in this country and abroad, gave their attention to steel. When the senior author explored the situation in 1902, there was little encouragement to be found in undertaking the study of the non-ferrous alloys. A start was made, and the metallography of the brasses and bronzes, as well as of the copper-nickel-zinc alloys developed materially under his direction. Annealing experiments were begun in 1902, and in the succeeding years the effect of temperature, and the influence of previous working, on the grain size of brass were studied. The conclusions so well known and widely published today were largely reached during those earlier years. In 1905 the first complete annealing series were made. By this it is meant that brass and copper sheet, 5 B & S Nos. hard, was machined into tensile test specimens, then annealed under accurate control for 30 min. at temperatures up to the melting point of the material. Various determinations were made, including tensile strength and elongation in 2 in. There rapidly followed similar series on all of the copper-zinc alloys from 100 to 60 per cent, copper, on the bronzes, cupronickels, and on copper-zinc-nickel alloys. At this point there was published by Grard, in October, 1909,' the very comprehensive and complete work on the tensile properties of cartridge brass, 90-10 copper-zinc, and electrolytic copper. The excellent photomicrographs in that paper illustrated the changes in structure produced by cold rolling as well as by annealing at different temperatures, but where Grard's work was confined to copper and to two alloys, the investigations in this laboratory have been over the entire fields of the commercial copper-zinc alloys, copper-tin alloys, representative copper-nickel and copper-nickel-zinc alloys as well as aluminum bronzes and others of a more special nature.

By K. P. Wang

Under the Communist regime marked industrial progress has been achieved on the China mainland. Within a decade, the country has been transformed from an economy primarily agricultural to one bristling with industrial possibilities. The industrial capacity of Communist China is beginning to approach that of Japan and will probably surpass it by 1962, the last year of the Second Five-Year Plan. The slogan already is Beat the United Kingdom by 1972, a goal which most observers feel will be achieved ahead of schedule. During the early years of the industrialization program in Communist China, emphasis has been placed on basic goods; hence additional time will be needed to make large quantities of the more complicated products. However, regardless of the current stage of industrial development, it is apparent that the necessary forward momentum has been created. The many capital construction projects being brought into production and the additional projects being initiated confirm this observation. The accuracy of Communist China's industrial statistics can be questioned, but their order of magnitude is clear. To properly evaluate the industrial capability of the country, differentiation must be made between the absolute quantities that reflect overall strength and the per capita quantities that reflect living standards. While Communist China is well on the road to becoming a world power, its living standards will remain below European levels for many years to come.

Jan 8, 1960

EVERY intelligent and practical investigator of minerals says that copper ore is found in various regions of the world and that among others Italy is very rich in it. But very little is mined there, perhaps because of a cowardly Italian avarice which has the power to make us lazy and indolent in carrying out those lofty and fine designs which should reasonably make us proceed swiftly, or perhaps because we are not prone to attempt extraordinary profit but only undertake those enterprises in which we are certain of a return on our investment. The reason for this might also be found in the meager possibility of success, which, since these things are not easily attempted because they are enormous undertakings of doubtful outcome, cools the spirit of men and in place of enthusiasm introduces the fear of loss, the fear of having to sacrifice not only time but also the work and money invested; then they think of the difficulty [II] of discovery, of the impossibility of full ownership, and of the necessity of excavating the mineral marrow from the hardest bones of the mountains with the brawn and efforts of men. To this is added the fear common to many that in attempting such things they may be called fools by certain ignorant and dissolute persons, and it seems better to them to be praised for becoming rich through usury and by many other infamous and illicit methods than to lay themselves open to the danger of censure from such as these. But there are those who deserve still greater censure, particularly princes and all rich and powerful persons, and theirs is an even more useless error than that of those who refrain for the above reasons. If the occasion and means present themselves for both attempting and continuing such a profitable and laudable affair as mining ores and if they hesitate solely because of cowardice or because they give ear to the bayings of ignorant hounds, or if because of their own willfulness they wish to remain prisoners of a detestable and ugly avarice, then this is their own loss.

Jan 1, 1942

By J. C. Coughlin, M. C. Flemings, T. Z. Kattamis

Experiments on Al-4.5 pct Cu alloy shou the dendrite arnz spacing increases with time during isothermal holding in the liquid-solid region. This coarsening of the dendrite structure is then shown to occur at roughly the same rate during solidification as during isothermal holding. Final dendrite arm spacing in both types of experiments depends primarily on coarsening kinetics. It is concluded that driving force for the coarsening is reduction of liquid-solid sur/ace area. Calculations based on two simple models show qualitative apreement with experinzent. 1 HERE has been considerable interest in recent years in determining effects of solidification variables on dendrite arm spacing in cast alloys. The interest has resulted primarily from the clear evidence that 1) the degree of homogeneity which can be obtained in a cast alloy with commercially practical homogeni- zation treatments depends on dendrite arm spacing, and 2) mechanical properties of the heat-treated casting depend on the homogeneity obtained.'-' In wrought alloys, microsegregation from the original ingot is carried to some extent into the final wrought product, and affects mechanical properties in similar fashion Experimental evidence available indicates that dendrite arm spacing in cast aluminum alloys is influenced only by cooling rate (or "local solidification timev*) and alloy content.Fig. 1, for example,

Jan 1, 1968

By W. A. Johnson, F. N. Rhines, W. A. Anderson

The rate of the high-temperature oxidation of pure copper has been measured repeatedly by numerous investigators. It appears to be generally agreed: (I) that at constant temperature, after the initial stages of oxidation have been passed and the scale has attained a substantial depth, the film thickness increases in proportion to the square root of the time of oxidation; and (2) that for any given period of oxidation the logarithm of the square of the film thickness is proportional to the reciprocal of the absolute temperature of oxidation.' These relationships are explained upon the basis that the rate of diffusion of copper to the external surface of the film is the controlling factor in establishing the rate of growth. Extensive studies have been devoted also to the mechanism and rates of the early stages of oxidation. There is thus available a reasonably well established theory of the oxidation of pure copper upon which to construct an explanation of the more complex oxidation of copper alloys. Few general principles have as yet emerged from the chaos of observations that have been reported in the field of the oxidation of alloys.2 It is evident, however, that the copper alloys may be divided into two main groups, whose oxidation characteristics are distinguish- able. The first group, composed of the alloys with the noble metals, forms substantially pure copper oxide scales; the alloying element is concentrated within the residual metal, and sometimes particles of almost pure noble metal are found in the scales completely surrounded by copper oxide. In the second group, composed of the alloys of copper with the baser metals, the alloying element appears as an oxide in the scale, often in greater concentration than in the alloy itself and sometimes to the exclusion of copper oxide. The oxide scales of the latter class have been found to be made up of one, two, and sometimes more distinguishable layers of which the innermost is often metallic in character, composed of particles of the oxide of the alloying element embedded in essentially pure copper and known as the subscale or zone of internal oxidation. The need for a thorough quantitative study of these modes of oxidation is evident. Since it is apparent that several mechanisms must be cooperating to produce the complex oxide scales found on copper alloys, the analysis of the process into its several simple operations should prove instructive. Fortunately, it is possible experimentally to produce internal oxidation in the absence of an external scale; this permits the isolation and intensive study of one of the steps in the oxidation process. In the present research the rates of internal oxidation of an extensive series of dilute solid solution alloys of copper have been measured and a theory has been developed to predict the observed

Jan 1, 1942

By W. A. Anderson, F. N. Rhines, W. A. Johnson

The rate of the high-temperature oxidation of pure copper has been measured repeatedly by numerous investigators. It appears to be generally agreed: (I) that at constant temperature, after the initial stages of oxidation have been passed and the scale has attained a substantial depth, the film thickness increases in proportion to the square root of the time of oxidation; and (2) that for any given period of oxidation the logarithm of the square of the film thickness is proportional to the reciprocal of the absolute temperature of oxidation.' These relationships are explained upon the basis that the rate of diffusion of copper to the external surface of the film is the controlling factor in establishing the rate of growth. Extensive studies have been devoted also to the mechanism and rates of the early stages of oxidation. There is thus available a reasonably well established theory of the oxidation of pure copper upon which to construct an explanation of the more complex oxidation of copper alloys. Few general principles have as yet emerged from the chaos of observations that have been reported in the field of the oxidation of alloys.2 It is evident, however, that the copper alloys may be divided into two main groups, whose oxidation characteristics are distinguish- able. The first group, composed of the alloys with the noble metals, forms substantially pure copper oxide scales; the alloying element is concentrated within the residual metal, and sometimes particles of almost pure noble metal are found in the scales completely surrounded by copper oxide. In the second group, composed of the alloys of copper with the baser metals, the alloying element appears as an oxide in the scale, often in greater concentration than in the alloy itself and sometimes to the exclusion of copper oxide. The oxide scales of the latter class have been found to be made up of one, two, and sometimes more distinguishable layers of which the innermost is often metallic in character, composed of particles of the oxide of the alloying element embedded in essentially pure copper and known as the subscale or zone of internal oxidation. The need for a thorough quantitative study of these modes of oxidation is evident. Since it is apparent that several mechanisms must be cooperating to produce the complex oxide scales found on copper alloys, the analysis of the process into its several simple operations should prove instructive. Fortunately, it is possible experimentally to produce internal oxidation in the absence of an external scale; this permits the isolation and intensive study of one of the steps in the oxidation process. In the present research the rates of internal oxidation of an extensive series of dilute solid solution alloys of copper have been measured and a theory has been developed to predict the observed

Jan 1, 1942

By Worthen 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 to the Bradley Mining Co. of San Francisco. The term "concurrent firing" for the purpose of this paper can be defined as feeding and firing a rotary kiln at the same end-that is, of course, the upper end. This is as opposed to "counter-current 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,1 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 flies 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 fifth 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: Sometimes 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, 1945