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By John Brownson

Ge-Si N-N heterodiodes hare been built recently which show promise as high-speed logic devices. Low-resistivity germanium is deposited on silicon substrates held at temperatures above the germanium melting point and an alloyed heterojunction formed. The diodes are fabricated from this material using conventional mesa techniques. Over-all device qualify has been greatly improved by the use of epitaxial silicon substrates, that is, a subsirale consisting of a film of thin, high -resistivity silicon on a thicker Piece of low-resistirily silicon crystal. A semimpirical device design equation has been devised which predicts switching performance fairly well within the range of resistivitics and geometries employed. Switching times 01 0.9 ns and PIV 's of —20 v are typical of the better 10-ma diodes. Switching times as low as 0.5 ns have been observed for 10-ma diodes and as low as 2.8 ns for 200-ma diodes. With further development it should be possible to improve switching speed by a factor of four. IN our laboratory, Ge-Si heterodiodes have been built recently which show promise as high-speed logic devices. The diodes have been built using a process reported in some detail in an earlier publication.' The process in short involves alloying a thin film of low-resistivity germanium into a silicon substrate. the germanium having been transported and deposited by the well-known Theuerer halide reduction process.2 This process contrasts with that reported earlier by Oldham who used an essentially conventional direct epitaxial deposition technique.3 Oldham's process, unlike ours, requires cleavage of the silicon sample inside the reactor furnace the instant prior to deposition. Our process has the advantage of yielding large-area macro-scopically plane heterojunctions. Heterodiodes in general have several interesting properties. Without attempting to summarize the theory of heterojunctions.4 two of these properties which have direct relevance should be mentioned. First, N-.V and P-P heterojunction diodes rectify alternating current. Provided that either the band gap or the electron affinity of the two materials is different (which in general is the case), electronic barriers will exist in the junction band structure. When the device is sufficiently forward-biased, the barriers shift so as to permit current flow, and when it is reverse-biased. the barriers block current flow. Second, for N-N and P-P heterodiodes. the foward-conduction process involves majority carriers only. Consequently. when such a device is turned off. there is no minority-carrier storage and hence the diodes switch on and off quite rapidly. As we have reported earlier. N-P and N-N Ge-Si heterodiodes have been built in this laboratory. As one would predict from theory, the N-P heterodiodes were rather slow in turning off while the N-N's were quite fast. Similarly, the turn-off time of the N-P's increased rapidly with forward current while that of the N-N's was independent of forward current. Both N-N's and N-P's were moderately photosensitive. Photocurrents resulting from normal room illumination were as high as 1 µa at 1 v for small-area devices. The most disappointing parameter of the early N-N devices was reverse leakage.' The reverse characteristic was invariably "soft" and leakage at only several volts reverse bias was intolerable. The reverse characteristic was greatly improved by using higher-resistivity silicon substrates. Leakage becomes large at voltages about one third of the avalanche voltage one would expect of a P-N homo-junction formed on silicon of the same resistivity. Thus leakage could be reduced to reasonable limits by using unconventionally high-resistivity silicon. Medium-power diodes formed on 30 ohm-cm substrates leaked typically 15 to 50 µa at 100 v reverse bias. The use of high-resistivity silicon substrate material, however, created a new problem. In order to have an acceptable forward-conductance characteristic. the area of the diodes had to be increased. With this increase in area, the capacitance increased. Switching time for N-N heterodiodes is essentially a linear function of capacitance. Thus when the resistivity was raised. so was the switching time. A SEMIEMPIRICAL HETERODIODE DESIGN EQUATION As a result of our experiments with a limited range of diode geometries and resistivities. a semi-

Jan 1, 1965

By T. Sekimoto, T. Kokubo, M. Yamamoto, K. Masuda, T. Moro, H. Sakamoto

The choking-free cyclone was developed primarily to remove solid particles suspended in a slurry containing fibrous materials, such as municipal solid waste. This cyclone is characterized by a screw conveyor at the underflow side of the cyclone. The screw conveyor has a hollow rotational shaft for air supply and is driven by a variable speed motor for discharge control. Even if the underflow discharge is highly concentrated, this type of cyclone can be stably operated without nozzle choking. High classification efficiency similar to that of a conventional cyclone can be obtained as a result of air introduction through the hollow rotational shaft. The recovery of organic matter and the removal efficiency of inorganic matter were actually improved by the application of this cyclone to municipal solid waste. After applying this cyclone to the desliming of fine sand, sand product of low water content was recovered.

Jan 1, 1980

By AIME AIME

DURING my senior year at college a professor said to his class that a student who failed to obtain a passing grade in that certain subject could not graduate with his class and that his diploma would be withheld until the failure had been removed. In that way for four years a diploma had been made to appear to us as the objective in attending college. We grew up to think that a diploma was the means of providing employment; consequently, a diploma could not be jeopardized and, heeding the professor's remarks, we resolved to put forth special efforts and make good. During one of our class periods this same professor digressed briefly from his prepared lecture in metallurgy and advised the boys to join a national technical society. He spoke with earnestness and sincerity. After class we students discussed those remarks. We concluded that the professor had not convinced us. We were already members of technical societies at school and saw no need of joining another. In fact, even up to that moment a society had never indicated to any of us that joining it had any relation to landing a job, and we were fully aware that joining another society meant paying out more money, for fees and dues, which money we then needed to buy food, clothes, and perhaps a new slide rule. Furthermore, we knew that joining a society was not part of the curriculum and, therefore, the diploma could not be withheld if we did not follow the advice. Our conclusion was that we would not join but would concentrate on our work that assured getting our diplomas.

Jan 1, 1936

By Francis A. Thomson

T HE engineer of today is by his training, by his traditions, and by the service which he must render, irrevocably committed to taking his part in public life along with the members of the older professions of ministry, medicine and law. Nevertheless, in comparison with these: three, so long recognized as the "learned professions-all three of which grew out of the functions of the priesthood-engineering in any modern sense of the word is a youthful profession indeed. So youthful is engineering in its present significance, that it may be said to date from the labors of John Smeaton, the lighthouse builder; of Simon Newcomen and James Watt, the inventors of the steam engine; and of George Stephenson, the inventor of the locomotive; at the dawn of the 19th century. Great works of an engineering character had, it is true, been executed long before this, but practically all of them had been rule-of-thumb enterprises, dependent upon a plethora of slave labor for their accomplishment. For illustration it is said that at Rio Tinto in the days of Hiram, king of Tyre, 40,000 men worked for a year to produce three tons of silver from the rich outcrop ore. Such an operation can scarcely be called an engineering enterprise, however, when we remember that a fourth of this number of men in these same mines, from which the richest ore was long ago extracted, produce at present over 100 tons of copper per day.

Jan 1, 1925

By AIME

TURMOIL has been rampant in the lead producing industry during 1946. The chronic labor shortage was aggravated by various work stoppages in mines, smelters, and refineries, while shortage of materials was widespread. Price uncertainties helped to confuse the situation in many countries and particularly in the United States until the removal of price control in the latter part of the year. At the end of the first year of peace, lead, which had been comparatively plentiful during the war years, was a scarce and high-priced metal throughout the world. It is the hope of the industry that the law of supply and demand, if allowed to operate without interference, will bring about a satisfactory balance between production and consumption. Under these circumstances it is not surprising that there have been few important developments in the metallurgy of lead, though a number of items of general interest to the industry have been reported. An ore body which may prove to be of considerable importance has been discovered at Mpanda, Tanganyika. The scarcity of lead ore is illustrated by the announced reopening of the La Manche lead mine in Newfoundland, idle for 56 years. A new lead producer came into production when Rhodesia Broken Hill started up its new smelter. Lead concentrate of 75 per cent grade is smelted in Scotch hearths and the lead is refined to market grade by the Harris process without desilverizing. Production is about 1000 tons per month. One Australian lead producer, Mount Isa, has returned to lead production after having operated its lead plant for the production of copper during the war. The East Chicago plant of the International Smelting and Refining Co. has been sold to the Eagle-Picher Co.

Jan 1, 1947

By H. K. Work, H. B. Emerick

IN the past year the steel industry underwent an abrupt conversion from a war tempo to a highly competitive peacetime schedule. It is still too early to gain a comprehensive picture as to which of the measures in production metallurgy, that made the war effort so successful, will remain in the postwar production of steel, but many of them undoubtedly will fill an important place after the war. Considerable speculation has developed regarding the disposition of the war-born production facilities of the steel industry. These include new open-hearth and electric furnaces, as well as vast numbers of auxiliary, supplementary, and balancing units that increased and speeded up production beyond the normal capacities of existing melting furnaces and finishing mills. Although these facilities were installed primarily to help meet war requirements, consideration was also given, in planning, to their possible peacetime use. The new equipment is generally modern and efficient, and it seems reasonable to suppose that strategically located units will gradually be absorbed by various steel companies to supplement their own facilities, or to replace in kind, obsolete and inefficient equipment now ready to be scrapped. Some, however,

Jan 1, 1946

By C. W. Davis

THE name fuller's earth, which was derived from its early use in "fulling" or removing grease from woolen goods, is a term that is generally considered to designate mineral matter, containing hydrous aluminum silicates of the clay group, which has a high capacity for removing colors from oils, whether of animal, vegetable, or mineral origin. Fuller's earths are usually dried and may be "tempered" by heating or may be treated with water or reagents to improve their efficiency. For our purpose the term "acid-treated earths" will include those products from the partial decomposition of mineral water -by acid which are equal to or more efficient than an untreated fuller's earth from Quincy, Fla., when used in bleaching mineral oil by the "contact" process. In general, the contact process for treating oils consists of heating and agitating a mixture of oil and finely divided adsorbent, the latter being subsequently removed by filtration. The term "adsorbent" is used because, although there has been a great deal of controversy over the mechanism of removal of impurities from oils by mineral matter, there is no doubt that adsorption, which involves the surface of the solid, plays a major part.1 The properties that make fuller's earth useful in the treatment of petroleum products by "percolation" and in the purification of edible oils by the contact process have long been studied, but the comparatively recent adaptation of the contact process to the bleaching of petroleum products has made desirable the further investigation of fuller's earth and other, adsorbent earths.

Jan 1, 1929

By C. W. Davis, L. R. Messer

THE name fuller's earth, which was derived from its early use in "fulling" or removing grease from woolen goods, is a term that is generally considered to designate mineral matter, containing hydrous aluminum silicates of the clay group, which has a high capacity for removing colors from oils, whether of animal, vegetable, or mineral origin. Fuller's earths are usually dried and may be "tempered" by heating or may be treated with water or reagents to improve their efficiency. For our purpose the term "acid-treated earths" will include those products from the partial decomposition of mineral water by acid which are equal to or more efficient than an untreated fuller's earth from Quincy, Fla., when used in bleaching mineral oil by the "contact" process. In general, the contact process for treating oils consists of heating and agitating a mixture of oil and finely divided adsorbent, the latter being subsequently removed by filtration. The term "adsorbent" is used because, although there has been a great deal of controversy over the mechanism of removal of impurities from oils by mineral matter, there is no doubt that adsorption, which involves the surface of the solid, plays a major part.' The properties that make fuller's earth useful in the treatment of petroleum products by "percolation1' and in the purification of edible oils by the contact process have long been studied, but the comparatively recent adaptation of the contact process to the bleaching of petroleum products has made desirable the further investigation of fuller's earth and other adsorbent earths.

Jan 1, 1929

By Michael Tenenbaum

A REVIEW of process metallurgy of iron and steel during 1944 in many ways reflects the political and military developments of the year. Early in 1944 the tremendous wartime emergency expansion program was virtually completed and the industry directed its efforts to maintaining maximum production wherever needed. The vigorous production programs inaugurated to support the Normandy invasions did not persist as Allied armies approached Germany. General public apathy which developed with the prospect of an early ending of the European fighting was reflected in a general relaxation in armament programs. Toward the end of the year, as the prospect of a prolonged war became real, the entire program revived considerably and the need for steel became acute. Between January 1940 and October 1944 more than 12,400,000 tons had been added to the nation's steelmaking capacities, and over 12,700,000 tons added to the blast-furnace facilities. The total cost of this enormous program was more than two billion dollars. By July 1, 1944, total steelmaking capacity had exceeded 94,000,000 tons, with blast-furnace capacity rated at 68,400,000. Annual steel production, which was 88,900,000 tons in 1943, increased slightly during the past year and was estimated at 89,500,000. Production of pig iron also increased somewhat from 61,800,000 tons in 1943 to an estimated output of 62,500,000 in 1944. This review deals with a few of the numerous factors involved in maintaining the wartime iron and steel program at the level necessary to accomplish this enormous output.

Jan 1, 1945

PUBLIC hearings began before the Committee for Reciprocity Information on May 24, 1950, for the purpose of unearthing data and opinion that will be helpful in the forthcoming reciprocal tariff and other trade-barrier negotiations at Torquay, England, on September 28th of this year. The conference this fall will constitute the "third round" of tariff negotiations under the General Agreement on Tariffs and Trade concluded at Geneva in 1947. The United States plans to negotiate with 17 other countries on possible tariff modifications on various articles all the way from baby carriages and bottle caps to lead and zinc-bearing ores. On May 31, June 1 and June 2, spokesmen appeared before the Committee for Reciprocity Information on behalf of the domestic lead and zinc mining industries. Producers of these metals protested the inclusion of paragraphs 391 (lead-bearing ores, dust and mattes), 392 (lead bullion, lead in pigs and bars, and scrap lead), 393 (zinc-bearing ores of all kinds), and 394 (zinc in blocks, pigs or slabs, and zinc dust) of the Tariff Act of 1930, as amended in the list of articles to be considered for possible tariff concessions at Torquay. It was pointed out that although operating costs have more than doubled since 1939 tariffs on these metals were actually higher in that year than at present. This, coupled with the detrimental effects of the recent series of devaluations, has sounded the death knell for a substantial number of domestic lead and zinc mines-a most undesirable development in the face of the ominous international situation, according to these spokesmen. It was urged that higher rather than lower tariff rates are needed on these metals. The opinion was expressed that it was inconsistent to foster a high living standard in our western areas and then, once it is attained, to undermine that condition by minimizing the protection that was partly responsible for it. The main theme of some arguments implied that although every effort should be made to close the "dollar gap" abroad, serious consideration must be given the methods employed lest our national security position be jeopardized in the process. The House Committee on Foreign Affairs completed hearings on H. J. Res. 236, to provide for United States membership and participation in the International Trade Organization. Hearings began on April 19th and ran for over five weeks. Many witnesses from industry and government presented voluminous testimony, which will not be available for public distribution for several weeks. However, it is no secret that the most controversial provisions of the Draft Charter of the ITO are: (1) Article 17 (Chapter IV on Commercial Policy) which would obligate members to negotiate for the reduction of tariffs and the elimination of trade preferences; (2) Article 20 which would prohibit the use of quantitative restrictions for protective purposes; (3) Article 16 which promulgates rules to implement the principle of non-discrimination in international trade; and (4) provisions permitting the use of protective measures for promoting economic development, particularly in backward areas, even though such provisions are inconsistent with those of the three articles cited above. United States membership in the International Trade Organization is essential to the successful operation of that body in view of this country's position as the economic giant in the present international trade pattern. Many countries are reluctant to take any action toward the ratification of the charter until it is known what course America will pursue. However desirable or undesirable the ideal of free multilateral trade may be it is unlikely that this Government's participation in the ITO will materialize soon. Advices in Washington indicate that H. J. Res. 236 will not be enacted during the present session of Congress. The legislative pattern designed to secure Congressional approval of the ITO is similar to that of the St. Lawrence Seaway project. The Seaway project was pending in treaty form for several years before the Foreign Relations Committee of the Senate and when the Administration decided to incorporate this project into bill form it was found that, while it passed the House promptly, the Senate decided to pigeonhole it because of the obvious intent to circumvent the constitutional prerogative of the Senate to advise and consent to the ratification of treaties. The ITO bill may be slated for a similar fate. It is deemed essential by western Senators and Congressmen that the present session of Congress enact some form of mining legislation before its adjournment, now set for July 31st. These legislators from prominent ore-producing states do not desire to return to their home areas in the fall emptyhanded. Aside from that, it is entirely superfluous to reiterate the necessity for maintaining a healthy domestic mining industry as a bulwark against a sharp rise in the temperature of the "cold war". Now that S. 2105 has failed a new bill is taking shape in the Senate Interior and Insular Affairs Committee. It is similar in language to H. R. 8221 (to encourage the conservation and development of the mineral resources of the United States) reported by the House Public Lands Committee on May 3, 1950, but so far has failed to receive approval of the House Committee on Rules. There are some qualified observers in high circles in Washington as well as in the mining industry who favor a tax incentive program to stimulate investment in mining enterprises, as opposed to a conservation and exploration program. The Bureau of Mines and the Treasury Department have undertaken a joint study to determine the need for modification of the tax laws as they apply to mining. The study is scheduled for completion before the end of the year, and appears to be supplementary to the investigation initiated by the National Minerals Advisory Council which culminated in the submittal of recommendations to the Secretary of the Interior in December 1949. The "cold war" is largely responsible for the increased demand for metals. Stock-pile purchases and heavy industrial demand due to military needs distort markets and disrupt normal price trends. Such activity has an unhealthy influence on metal production, luring some producers into a state of dependency on the continuation of this condition. When stock-pile objectives are met sometime in the future purchases must then come to a halt unless international "fireworks" are touched off. It can only be hoped that technological improvements and further mechanization of mines coupled with the stimulus of a rising population will offset the anticipated drop in industrial demand and cessation of stockpile purchases when the international crisis abates.

Jan 7, 1950

By John Birkinbine

(Wilkes-Barre Meeting, June, 1911). MODERN advances in practically all lines of industrial development have occurred in such rapid succession, and have been accepted so readily as accomplished facts, that a retrospect surprises us, by showing how comparatively few of the acknowledged factors of improved conditions may be considered as old. While these advances have not been confined to any country, they have been more pronounced in some than in others, and nowhere more so than in the United States, the population of which, having multiplied nearly three-fold between 1870 and 1910, demanded a proportionately greater increase in materials, supplies, and manufactured products. It therefore appears desirable to discuss mainly conditions in the United States, as concrete evidence of industrial progress throughout the world. Looking backward for but three generations, we may trace the introduction and development of canal- and steamboat-navigation; railroad-transportation; artificial illumination beyond that furnished by candles and lard-oil; quick communication by mail, and subsequently by telegraph or telephone; the manufacture of iron, beyond forms of small dimensions; the production and utilization of steel in large quantities; the economic use of mineral fuel, oil and gas, etc. The practical coincidence of the fortieth anniversary and the 100th technical meeting of the American Institute of Mining Engineers, offers temptation to recall and compare the conditions of mining and metallurgy in or about the years 1871 and 1911. A complete resume would cover phenomenal changes in mining-methods and equipment by which the output of individual exploitation has grown from scores to hundreds and even thousands of units in equal time-intervals. Extension of operations in depth and area, demanding machinery of great power

Aug 1, 1911

By D. W. Loucks

There is plenty of evidence to indicate that at least one of man's chief interests in life is to make himself as comfortable as possible. If you doubt this, just watch the fellow next to you for the next half hour trying to find the most comfortable position that a hard chair has to offer. Comfort, however, does not always mean an easy chair. To some, it may mean a wealth of money: to another, freedom from worry. But to most of us, it means first of all a comfortable atmosphere in which to live, and to a great many of us it probably also means freedom from that annoying task of firing the furnace. Today more than ever before, automatic heat is one improvement that is placed high on everyone's list. Perhaps this is because automatic heating is becoming relatively cheaper. Perhaps it is because of a good publicity campaign on the part of the oil and gas men or maybe it is just that we are getting lazier day by day. At any rate, almost every issue of Better Homes and Gardens, House Beautiful, or your other favorite home magazine carries an article extolling the virtues of this or that automatic heating system.

Jan 1, 1949

By Frank G. Breyer

C ONDITIONS have not been favorable for new developments in any line. It has been a period, how- ever in which recent developments have been subjected to the severest tests. Those which have been able to hold their own in the severe competition of 1932 must be considered fully proved commercial processes. The continuous vertical-muffle retort plant at Palmer- ton is reported to have been in operation at practically full capacity throughout the year. The high quality of metal produced and the low operating costs are factors which have kept this plant running when many of the older furnaces were shut down. The plant at Meadow- brook, W. Va., is also reported to have been in steady operation throughout the year. Average retort life is said to be better than two years with about three-quarters of the original retorts still in operation after 2 ½ years.

Jan 1, 1933

By H. B. FERNALD

THE first year to which the Revenue Act of 1936 has applied is now passed. It is appropriate to try to give some calm thought to the plan of Federal income taxation as now imposed and what it will mean to the business and industry of the country if this plan of taxation is continued unchanged. Whether or not we like to pay these taxes is beside the point. Taxes are high and may be expected to be high for many years. The important question is whether the taxes to be imposed will destroy or injure business enterprise and development, and, in so doing, lower the standards of employment, living, comfort, and welfare of our people. The power to tax is the power to destroy. That destruction may come suddenly as a cyclone, or slowly as dry rot. What, if any, features are there in the present plan of Federal income taxation that have these destructive tendencies? A few of the points follow that seem to call for consideration.

Jan 1, 1937

By P. N. Nikiforuk, M. C. Zoerb

An analog computer model has been developed of a large, walking dragline. This model permits changes in the configuration of the dragline, or changes in its digging cycle, to be readily investigated on a computer. As a result, it is possible to determine ways of improving the dragline performance without having to carry out many expensive experiments on the actual machine. This model can also be used as a simulator for dragline operator training. INTRODUCTION The movement of large volumes of material is always a costly operation and the increasing trend towards the use of large capacity equipment does not necessarily produce the economy desired. This problem is of particular concern to the mining industry in its open-pit operations where large draglines are used to remove the overburden. Since this operation often forms a very large part of the total cost of open-pit mining it is particularly important that it be kept as economical as possible. This requires that the dragline be operated at its maximum possible productivity. In order to optimize the operation of a dragline it is desirable that a suitable model of the dragline be available for study. Once such a model is available the effects of changes in the configuration of the dragline, or changes in its digging cycle, could be readily investigated on a computer and methods of improving its performance could be determined without having to carry out expensive experiments on the actual machine. Such models would be of use not only to dragline users, but also to the manufacturers of draglines for design purposes. Presumably studies of this type could eventually lead to computer-con trolled stripping operations. As far as can be determined very little work1'2 has been done on the derivation of dragline models. Such models must be derived before work of the nature indicated in the previous paragraph can be carried out. As a small contribution to this field this paper describes work that has been carried out by the senior author during the past few years on the derivation of one such model. This model describes the drag, hoist and swing operations of a 35 cu yd, commercially available, walking dragline. This model was derived for use with an analog computer and can be used either for optimization studies, or for the training of dragline operators. DESCRIPTION OF DRAGLINE General: The particular dragline for which an analog computer model was developed is owned by the Great West Coal Company of Estevan, Saskatchewan. It is a walking dragline and its function is to remove 40

Jan 1, 1967

By F. B. Plummer

PRODUCING operations abroad during 1940 were shrouded in the fog of war. Little, if any, concrete information is available, and the data that issue from the belligerent countries are too frequently distorted for military purposes, for the volume of supply of gasoline and fuel oil has become an important strategic secret. Despite this lack of information signs indicate the spread of a slow paralysis which is gripping producing operations in foreign countries. Only in the Caribbean area are developments proceeding normally and even there the destruction of the Western European market is being seriously felt. This creeping paralysis is being brought about partly by the serious shortage of materials so necessary for drilling and other producing operations such as steel, machinery, and the like-together with a scarcity of that prime munition of war-money. Markets too have been curtailed by the operation of exchange control as all exchange is needed to support war efforts. As a result, gasoline is tightly rationed in all belligerent countries. The growing casualties in shipping are fast restricting the water-borne trade in petroleum, but have had a local stimulating effect in some areas where the risk is less or where water-borne transport can be efficiently used as for instance Trinidad and Egypt. The type of product needed for war effort, particularly the great demand for aviation gasoline, has changed the schedules of .refinery operations. As a result of all these influences the world oil picture outside the United States- has vastly changed during the year.

Jan 1, 1941

By H. R. MacMichael

IN the Chihuahua district of Mexico the first smelting was that inaugurated by the early Spaniards for the production of silver bullion. The ores treated were high in silver and lead. Silver-lead bullion was first produced and the lead then cupelled to waste, with the slag produced running from 5 to 10 per cent in lead and about 25 to 40 per cent silica. The ore was mined by peon labor, often being carried out of the mine on the backs of the men, and then transported by burros. Furnaces were of primitive construction, adobe or rock being used in the earlier period and some iron later when it became available. Blast was originally supplied by bellows manually operated. Such smelting was carried on to a greater or lesser extent until the latter part of the last century, and so extensive was it that many hundred thousand tons of leady slag remained to be treated in modern furnaces. In 1908 a smelter was placed in operation at Chihuahua by the American Smelting & Refining Co. At that time the ore was practically all oxidized and by a little selection, self-fluxing mixtures could be made, but with an average lead content usually under 10 per cent and sometimes as low as 7 per cent. The bullion produced would carry from 150 to 300 oz. silver per ton. The slag made approximated 30 per cent SiO2, 42 per cent FeO, 21 per cent CaO, and perhaps 3 per cent Zn. The ores varied from hard, coarse material which was passed through a crusher, to a considerable quantity of fines which had to be smelted as it came, as crushing the coarse was the only preparation for smelting.

Jan 1, 1933

By C. W. Davis

THE name fuller's earth, which was derived from its early use in "fulling" or removing grease from woolen goods, is a term that is generally considered to designate mineral matter, containing hydrous aluminum silicates of the clay group, which has a high capacity for removing colors from oils, whether of animal, vegetable, or mineral origin. Fuller's earths are usually dried and may be "tempered" by heating or may be treated with water or reagents to improve their efficiency. For our purpose the term "acid-treated earths" will include those products from the partial decomposition of mineral water by acid which are equal to or more efficient than an untreated fuller's earth from Quincy, Fla., when used in bleaching mineral oil by the "contact" process. In general, the contact process for treating oils consists of heating and agitating a mixture of oil and finely divided adsorbent, the latter being subsequently removed by filtration. The term "adsorbent" is used because, although there has been a great deal of controversy over the mechanism of removal of impurities from oils by mineral matter, there is no doubt that adsorption, which involves the surface of the solid, plays a major part.1 The properties that make fuller's earth useful in the treatment of petroleum products by "percolation" and in the purification of edible oils by the contact process have long been studied, but the comparatively recent adaptation of the contact process to the bleaching of petroleum products has made desirable the further investigation of fuller's earth and other adsorbent earths.

Jan 1, 1929

By Robert T. DeGavre

INTRODUCTION The $645 million financing for Inco Ltd's Soroako nickel project in Indonesia not only represents a significant human achievement but also there are certain important lessons that can be derived from Inco's experience in financing the project. The paper will not present a technical assessment of the project since Inco Ltd. submitted a series of papers on this subject at the international Laterite Symposium as part of the 108th Annual Meeting of the AIME in February 1979. BRIEF HISTORY OF THE SOROAKO PROJECT Table 1 summarizes the milestones achieved in the Soroako project and its financing. Exploration Phase A contract of Work was signed on July 27, 1968 by the Republic of Indonesia and F.T. International Nickel Indonesia (P.T. Inco) covering an extensive area of over 25,000 square miles on the two southeastern arms of the island of Sulawesi. The Contract provides that P.T. Inco has the sole responsibility for financing the project and determining the terms on which the financing should be obtained, that P.T. Inco has the right to receive and hold outside of Indonesia foreign exchange revenues and to freely dispose of such revenues, and that Indonesians have the right to purchase up to 20% of the equity of P.T. Inco over a period following start of production. P.T. Inco began field investigations in the Contract Area in August 1968. Preliminary reconnaissance sampling with portable drills broadly outlined areas of favorable laterite terrain which were then systematically sampled on surveyed grids. By early 1971 sufficient exploration work had been completed to indicate that the laterite deposits near Soroako could sustain a major nickel-producing plant (figure 1). Pilot plant studies in 1970 and 1971 at Inco's research station in Port Colborne, Ontario, using two bulk samples of Soroako ore material, also confirmed that the ore could be upgraded and treated for the recovery of its metal values. Feasibility Phase Encouraged by the results of its exploration program and pilot-plant work, Inco Ltd. commissioned Toyo Engineering Company of Japan in August 1971 to prepare a capital cost estimate for a relatively small nickel project called "Stage I". Stage I was to be a single-line pyrometallurqical process plant with an annual capacity of approximately 15,000 metric tons of nickel contained in 75% nickel sulphide matte (see Figure 2). Electric power was to be supplied by a thermal power station. It is important to recognize that Inco's strategy was to develop the Soroako ore deposits in several stages: first, construct a small project to gain experience and to reduce the initial capital outlay and then later expand in one or more steps to a much larger project to achieve maximum economies. The strategy reflected both Inco's financial position in 1971 as its sales and earning dropped sharply and the difficulties previously experienced by Inco in trying to launch in the late 1960's very large "greenfield" nickel projects in New Caledonia and Guatemala. Toyo's Project Development Study was completed. in January 1972. Based upon Toyo's cost estimate for physical facilities, Inco estimated the total capital cost of Stage I to be $115 million. For the next several months, Inco ran numerous in-house financial feasibility studies, using as inputs Toyo's cost estimate and the results of its exploration and pilot plant programs. In September 1972, Inco completed a project feasibility study which was based upon a capital cost estimate of $135 million. The feasibility study was immediately made available to potential partners and lenders. Partner Negotiations The Japanese nickel market had from the outset been central to Inco's planning for the Soroako project. That market had been growing dramatically at rates in excess of 20% per annum during the 1950's and 1960's. Japan had established, for rational security and other reasons, a domestic

Jan 1, 1985

By H. J. Beach

This paper describes the properties and uses of cementitious mixtures containing 10 to 20 per cent bentonite and 2 per cent or more sodium chloride. Salt additions improve bentonite cement by increasing early strength and stabilizing viscosity without changing thickening time. The volume yield of cement is increased 20 per cent or more without lowered early strength. The unique properties of salt in this type of system make savings of more than 10 per cent possible where light-weight, low-strength cementitious material is adequate to fill behind pipe. The density range of these mixtures is 12 to 13 1b/gal and the filtration rates are medium-low, aiding the placement of long columns in primary cementing. Where available, sea water is an ideal salt source in preparing these slurries. INTRODUCTION Accelerators increase the rate of cement hydration. In speeding reaction with water, they can affect cement performance by reducing thickening time and increasing early strength after set. Accelerators that cause both effects can be considered "total", and those which produce only one effect can be called "partial". Materials that act conversely to accelerators are retarders. and they also can be total or partial. Partial retarders. make high-temperature cementing possible by prolonging thickening time while impairing early strength only slightly. Most known accelerators are total. A useful partial accelerator would increase strength without altering thickening time. This report concerns material combinations in which a normally total accelerator exerts unique partial properties. Utilizing these limited effects improves bentonite cement. SEPARATE EFFECTS OF SODIUM CHLORIDE AND BENTONITE ON CEMENT Sodium chloride and calcium chloride are commonly used in cement, and at low concentrations their effects are similar. Ludwig1 studied sodium chloride in API Class A and Class E cements.' Figs. 1 and 2 sum- marize his data taken at 140°F on slurry pumpability and early strength. Normal water-to-cement ratios are 0.46 and 0.40, respectively, for Class A and Class E cements. At saturation the salt content is 12 to 14 per cent of the weight of cement solids. The illustrations, therefore, cover the range of salt solubility in the mixing water. The data show that sodium chloride is a total accelerator of the Class E cement studied over the range of solubility. It is total in Class A cement to 6 per cent. Above this concentration salt becomes a retarder— partial from 6 to 10 per cent and total above. These results are general for different brands of Class A cement, although the shift from acceleration to retardation may occur at different salt concentrations for different temperatures. The results are specific for the Class E brand studied. In discussing his data, the investigator emphasized that different Class E cements might respond erratically to salt, depending on the brand chosen. Morgan and Dumbauld3 escribe the properties of bentonite cement in a paper that is a standard reference in using these systems. Bentonite functions in cement as an enabling agent; each bentonite addition equal to 1 per cent of the weight of dry cement makes possible the further addition of 4.5 per cent water.' Thus, 10 per cent bentonite in Class A cement, normally slurried neat with 46 per cent water, enables the slurry to contain another 45 per cent before settling. Water is one of the lightest and cheapest cement extenders; it reduces density and cost. Bentonite cements produce uniform slurries having low susceptibility to solids separation. After set, they offer low resistance to perforation.