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By Charles E. Nelson

In considering the types of scrap that are processed into secondary magnesium, it is important to point out that the greatest proportion of this material is fabrication, foundry and machine shop scrap that is generated during the conversion of magnesium products into the finished article. This material, then, is largely of the same composition and quality as the original ingot or heat of metal except as it may be mixed with other compositions or metals in the fabricating process. Insofar as such materials can be processed back into secondary ingots or final products which meet the composition and property standards required of the original virgin stocks, then it seems reasonable that such products are fully equivalent to the primary products. With these premises then, it is the intent of the present discussion to consider briefly some of the methods whereby scrap may be generated, segregated, shipped, and processed in such a manner that the final products will be equivalent to virgin materials. Some information on the effects of impurities will be given in order to aid in the evaluation of these products. SCRAP GENERATION The method by which scrap is generated serves in a rough way to classify the resulting materials in terms of how they may be handled and recovered. These methods will be dealt with briefly. Machining operations such as milling and turning undoubtedly provide the great-

Jan 1, 1943

By P. H. G., Durville

ANY metal which contains even a small percentage of aluminum possesses certain peculiarities of appearance and properties which are exhibited both when the metal is melted and after it solidifies. Pure aluminum, or an alloy containing a small proportion of aluminum, can be melted without flux-except for a layer of charcoal-because a film of aluminum oxide and metal forms at the surface of melted aluminum. Although very thin, this film is air-proof, and it prevents the metal underneath from oxidizing. This oxidized film does not move easily on account of its toughness and high surface tension. One very important point in connection with this process of still casting has not been strongly enough stressed, namely, that the same kind of surface film with the same peculiarities forms over the surface of all melted alloys that contain even a small proportion of aluminum. Experienced foundrymen know how desirable it is to cast aluminum under its "skin" or under the surface of the film which tends to remain still. In the case of red copper, when in fusion, the surface shows pure copper only. This' is due to the fact that liquid copper constantly absorbs the copper oxide which forms on the surface. By closely examining melting copper the oxide can be seen dissolving in the bath, and going into solution just as pulverized sugar dissolves in water. When copper is cast in the open, either in wire bars or cakes, the surface of metal exposed to the air is covered by a film of black oxide that cannot be absorbed by the metal.

Jan 1, 1927

By A. G. Moncrieff

In the paper the authors show [(Fig. 12)] in diagramatic form a "typical vacuum filtration system." This indicates a drum filter with two filtrate receivers-one for mother liquor and one for wash liquor. Have the authors ever found a drum filter that will adequately separate mother liquor from wash liquor? I recall in about 1957 being superintendent of a major copper leaching operation treating oxide flotation concentrates. The plan was being expanded, and filters installed to replace CCD following acid leaching and primary thickening of the pulp. The design of the expansion allowed the mother liquor to join the thickener overflow as feed for the electrolytic tankhouse. The water balance required that only pan of the wash liquor could be electrolysed direct, and the remainder had to be treated by lime precipitation. The design assumed the mother liquor would have the same copper content (about 50 gpl) as in the leach pulp solution, and the wash liquor about 50% of this (25 gpl from memory). You can imagine my horror when, on starting up, the solution from the mother liquor receiver contained somewhat under 40 gpl and, from the wash liquor receiver, somewhat over 40 gpl. The filters were provided by two of the most reputable manufacturers and, in the end I believe they agreed that never before had they supplied rotary drum filters that would segregate the filtrates. By changes to the valve design we made minor improvements, but eventually decided that insufficient segregation of the filtrates was possible to warrant trying to do it. On further consideration I concluded that, owing to the time delay between solution passing through the cake and entering the valve, segregation was impossible, though radical alteration of the internal piping of the filter might have improved it. I would be interested to know if anyone has found a solution to this problem using a drum filter. If not, why go on publishing information that infers that it is possible?

Jan 1, 1982

The income of the Institute is derived mainly from dues, advertising in MINING AND METALLURGY and sale of publications. These sources are fortunately supplemented by the interest from invested funds now amounting to over $500,000, a considerable portion con- stituting endowments for especial purpose?s. Aside from the medal funds the principal endowments are the James Douglas Fund for support of the Library, the Rocky Mountain Fund and the Seeley W. Mudd Memorial Fund. The income from the two last named is available for the support of research and a variety of other purposes. It is allocated by the Board of Directors upon recommendation of standing committees in each case. An active effort is being made to increase the endowments of the Institute, it being felt that unusual opportunities exist for research and public and professional service through the organization.

Jan 1, 1937

By John D. Ridge, Robert C. Barwick

The amount of lead in concentrates that moved in international trade in 1952 was only 16 pct of the world mine production of lead and was less than 27 pct of the total of lead in concentrates and lead metal that traveled from one country to another. Because almost all lead is derived from galena, lead concentrates are high grade, with a theoretical maximum of 86 pct lead, and can be shipped as such without transporting a considerable weight of waste material. It would not be surprising, therefore, to find the large share of lead in international trade moves in concentrates (Rule 5). This is not, as has just been mentioned, actually the case. There is more than one explanation for the situation. Lead smelting is not a particularly difficult process and is one for which smelting equipment can readily be made of the best size for the tonnage to be handled. Another factor that encourages local smelting is the effort of many mining countries to see that a maximum of profit from their raw materials remains in the home country. Still another factor is the newness of large scale lead mining in two of the three largest exporters of lead in concentrates. In these countries, South West Africa and French Morocco, there has not yet been time to erect enough smelting capacity to process all of the concentrate output. Even in these countries, however, it will not be long, if present trends continue and plans are fulfilled, before most or all of the lead mined is domestically smelted.

Sep 1, 1955

By R. L. Wiegel

Consideration has been given to the merging of a size reduction model and a mineral liberation model to permit prediction of mineral composition as a function of size. The results of this integration of size reduction and mineral liberation models are discussed from both theoretical and practical viewpoints using batch grinding data for a magnetic iron formation sample as a demonstration vehicle.

Jan 1, 1977

(Under this heading will be published notes sent to the Secretary of the Institute by members or other persons introduced by members.) No. 504.-Member, technical graduate, draft exempt, who has been employed as research chemist in cyanidation and flotation for past 5 years, desires position with large company as metallurgist or assistant mill superintendent. Especially experienced in flotation of gold and silver ores, but am also familiar with flotation of lead-zinc ores. Foreign service not desired. Will be at liberty after Dec. 1, 1918. No. 505.-Member, graduate mining engineer, with 8 years' practical experience, including experience as superintendent. Desires position as engineer, foreman or superintendent of mine. No. 509.-Petroleum geologist and engineer, member, now engaged in consulting work, with five years' experience in Mid-Continent and Eastern fields, desires position with responsible concern either in South or South American countries. No. 510.- Chemical engineer, member, technical graduate, at present officer in Chemical Warfare Service of the United States Army, desires position in the East. Several-years' experience in design, construction, and operation of chemical and metallurgical plants. Minimum salary, $200. Available Jan. 1, 1919. No. 511.-Mining engineer, 32 years old, single, desires position. Speaks Spanish and French. Recently manager of large copper mines. Experience in steam shovel and underground mining. No. 512.-Mining engineer, technical graduate, member, 32 years old, single, 10 years' experience in United States, Mexico and Central America in mining, prospecting, milling, chemical research and business experience. Speaks Spanish. Open for engagement as superintendent or assistant. Can give references as to ability and integrity.

Jan 1, 1919

By Axel Sahlin

The day is long past when linen and cotton rags were the exclusive raw material of the paper-trade. Wood-fiber, chemically or mechanically prepared, straw, hemp and Esparto grass have largely supplied the demand, which the old materials did not suffice to fill. But even these newer fibers have been of late supplanted, to some extent, by mineral pulp. Weighting and filling materials have also been resorted to, partly to give body to the fabric, partly to increase its weight and reduce the cost per pound. China clay, sulphate of lime and soapstone have generally been employed as loading materials. Even though these materials lack fiber, their addition must by no means be viewed, as it too generally is, entirely as an adulteration. No doubt, to a certain extent, they weaken the paper ; but for ordinary grades the addition of these non-fibrous substances is a positive advantage, as they close the pores between the fibers and lend to the paper a great degree of opaqueness and a superior finish. Fibrous talc, as a form of pulp, has the same effect, without appreciably weakening the paper. When, therefore, some fifteen years ago, fibrous talc in large quantities, and of marvellous purity and whiteness, was discovered in the neighborhood of the town of Gouverneur, it was not long before the

Jan 1, 1893

By John M. Hancock

IN beginning my remarks, may I make it entirely clear that since January 4, 1947, I have not been a member of the United States Delegation to-the United Nations Atomic Energy Commission I am speaking, therefore, in purely a personal capacity. Because of the interest of the engineering profession with reference to uranium, and because of the title assigned me for this talk, I am going to assume that you know what the United States Plan is for the control of atomic energy. At best, in the limited time, I could only summarize, at the risk of giving undue emphasis to the items mentioned, and at the risk of omitting many important parts of what seems so far to be a complete and well-rounded Plan for meeting the problem. I will aim to comment upon those aspects of the Plan that continue as problems and involve apparent, or obvious, misunderstandings and contrary views The control of atomic energy represents not only a problem but a challenge-both faced by- all the peoples of the world It involves a new approach to the problems of the kinds that arise between nations, problems that have not ever been solved even by international treaties in their efforts to outlaw weapons of war. These efforts range from the Kellogg-Briand treaty to outlaw war, and its obvious failure to prevent World War II, to the interdiction by the Pope of the use of the crossbow in the days of the Crusades. All previous plans have been failures-that makes

Jan 1, 1947

Jan 1, 1898

By Swapan Bhattacharya

United States federal and state regulatory authorities require underground mine operators to adopt adequate measures to minimize material damage to the surface caused by mine subsidence. This paper presents an approach to define and determine the extent of material damage due to subsidence from underground coal mining. The basic steps involved in the development of adequate criteria have been enumerated together with the approaches and methodologies used.

Jan 1, 1984

By E. C. Herkenhoff

THIS subject may be controversial. Personal preferences influence the final selection of cyclones, and side issues such as costs, floor areas, head room, and ease of replacing worn parts all enter the picture, but the following comments and data should apply to most cyclone selection problems. Broadly, the uses for cyclones in wet classification may be divided into three fields: 1) Open circuit operation, for two products, in which feed rate and sizing vary and the products vary. For example, feed may be divided into a sand product and a slime product. 2) Open circuit operation, for two products, in which feed varies, one product to have constant sizing. This calls for adjustment in either the apex or the vortex aperture. 3) Closed circuit operation, the finished product to have constant sizing. Most classification jobs fall in this category.

Jan 8, 1957

By J. B. Hiskey, G. Ramadorai

This paper presents the kinetics of leaching pure wulfenite (PbMoO,) with sodium sulfide solutions. Wulfenite dissolves in the presence of sulfide ion according to the following reaction: PbMoO , + S= PbS + MOO;. Synthetic galena is formed and molybdenum is released to solution as molybdate ion. The reaction follows the shrinking core model and the leaching mechanism involves mixed kinetics where both diffusion and chemical reaction are rate controlling. Molybdenum extraction is explained in terms of temperature, particle size, and sodium sulfide concentration.

Jan 1, 1977

By Terry G. Richard, Sunder H. Advani

A sequence of 250 unconfined compression tests were completed on a common marine shale indicative of the overburden strata of east- central Ohio. The samples were of a light gray clay shale of Pennsylvanian age. The shales considered are obvious layered materials with distinct bedding planes. For this reason there is sufficient evidence to consider this material as anisotropic in nature. With a properly chosen reference coordinate system this anisotropy can be reduced to a layered orthotropic characterization. This implies that the mechanical properties can be specified with regard to principal material directions. With this nature in mind a systematic study of the combined influences of strain rate and moisture conditioning was initiated. Of particular interest is the variations in unconfined ultimate compressive strength with variations in the controlled parameters of strain rate, moisture conditioning level and direction of testing. Results of this particular phase of the program are presented.

Jan 1, 1982

By G. W. Land, A. F. Duzy

There have been some problems associated with hot coal, defined as oxidizing coal heating toward ignition temperature, in shipments from the US to overseas markets. This paper will provide, first, a brief review, together with a selective bibliography. Second, a thorough discussion of coal oxidation is covered. Third, potential effects of storage are presented and, lastly, methods are suggested for the safe storage and bulk transfer of coal. The scope includes coal storage for power plants.

Jan 1, 1986

Jan 1, 1954

By Thomas M. Drown, P. W. Shimer

In a communication to this Institute at the Baltimore meeting, February, 1879,* on the "Determination of Silicon in Pig Iron and Steel," the method recommended was the treatment of the metal with nitric acid until action had ceased, and then evaporating with sulphuric acid until the nitric acid was nearly or quite driven off. After filtration of the siliceous and carbonaceous residue, and washing with hot water and hydrochloric acid, a silica was obtained, on ignition, which was quite pore. Since this paper was read before the Institute, we have had large experience with the method, and

Jan 1, 1880

By D. H. Bacon

Our Transactions contain so many suggestions of apparently trivial, yet really important, contrivances for the saving of time and

Jan 1, 1893

By A. J. W. Schwandt

Magmont is a venture jointly owned by Cominco American Incorporated of Spokane, Washington and Dresser Minerals, Division of Dresser Industries, Houston, Texas. Cominco American assumed direction of the operation in 1961 and completed exploration, preproduction planning and development, and is now the operating partner managing the operations. The plant has a rated capacity of 4200 tpd and produces in excess of 60,000 tons of lead per year. [ ]

Jan 1, 1970

By Joseph Lindmayer, Karl M. Busen

If silicon is in contact with silicon oxide, a heterojunction is formed which induces an inversion layer ("channel"). Influences of impurities and structural parameters on the channel are discussed. There seems to be no relation between surface damage in silicon and the channel. Phosphorz~s doping of the silicon oxide has no pronounced effect on the channel. Channels which were well above the range predicted by the heterojunction model were related to the action of H* at the silicon/silicon oxide interface. Channels which were well below tlze range predicted by the heterojunc-tion model were related to a transition region in the oxide adjacent to the interface. In support of the assumed transition region and the H+ are the ex-periments described on the paper. Furthermore, the concept of metastable OH groups in silzca, known from other publications, has been used to explain certain channel characteristics by the formation and the accommodation of hydrogen in the silicon oxide. THE electrical characteristics of a semiconductor device in many cases are influenced by the conditions of its surface. Because these conditions often are changing with temperature, time, ambient, or other parameters, numerous attempts have been undertaken to stabilize them by suitable processes. Several years ago Atallal studied the silicon/silicon dioxide interface and since then increasing attention has been given to the silicon dioxide as a means to stabilize silicon surfaces. This led to the evolution of the planar silicon devices where oxide layers are used to protect places at which the junctions are intersecting the surface. The formation of the oxide layers on silicon can be carried out by a variety of processes: high-temperature thermal oxidation (exposing the silicon surface to oxidizing agents such as 02, HzO, COz), evaporation of SiOz, or anodic oxidation of silicon. Originally the oxides were considered able to "passivate" the silicon surface and it was understood that they 1) protected the surface against any influence from the ambient and 2) stabilized surface conditions which were necessary for proper device performance. It soon was realized that the second quality was not always obtainable: Atalla and Tannenbaum showed that, in the process of forming a layer on doped silicon by thermal oxida- tion, electrically active impurities in the silicon near the interface are redistributed, thus giving rise eventually to the formation of unwanted charge distributions. The degradation of planar junctions during reoxidation of silicon was observed by Barson et a. Surface studies with silicon planar junction structures indicated that the breakdown voltage depended on the kind of procedure which was applied during or after oxidation.*" Yamin and worthinge report on charge storage and dielectric properties of SiOz films at elevated temperatures. Another influential parameter on the silicon surface is discussed by Lindmayer and usen,' namely the appearance of a surface potential on silicon as a consequence of the heterojunction formed by the silicon/silicon oxide interface. In the present paper the influence of impurities and structural parameters in silicon oxide in connection with the heterojunction is a particular object of our investigations. I) EXPERIMENTAL The material used was 10 ohm-cm p-type silicon slices with either damaged surfaces (mechanically lapped or polished) or damage-free surfaces (chemically polished). The majority of the slices were oxidized for 1 hr and 20 min at 1250°C in a steam + oxygen atmosphere generated by passing O2 through HzO at 90°C (wet oxygen). This led to oxide layers of about 9000 A. On some slices oxide layers were grown in pure oxygen (dry oxygen). By a photoresist process a set of 20 by 200 mil windows was then etched out from the oxide layer. The pattern of the windows is shown in Fig. 1. In a subsequent process n-type pockets with surface concentrations between 2 x 10" and 5 x 10" cm"3 were formed by phosphorus diffusion. This allowed ohmic contacts between the silicon surface and tungsten probes which for electrical measurements were placed into two adjoining windows and

Jan 1, 1965