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By J. H. Frye, S. G. Holder, E. E. Stansbury

Internal friction studies on annealed and cold-worked pure silver and alloys of silver with 4.5 atomic pct each of Cd, Sn, and Sb are reported. Small amounts of cold work, introduced by stretching pure silver, decrease the internal friction; large amounts of cold work, by wire drawing, cause this decreased internal friction to rise. Results of severol anneoling histories on the room-temperature in-ternal friction indicate a rather complex recovery and recrystallization behavior. A rather system-atic alloy effect is observed for the elements of Period V-B in silver in both the annealed and cold-worked states. DURING recent years internal friction measurements at very small stress levels have been interpreted in terms of structural models and mechanisms occurring within the metal or alloy.These measurements have been made over wide ranges of frequency of vibration and of temperature. While the effects of impurities, alloying, and plastic deformation have been studied by numerous investigators, no investigations of the effect of a series of solutes related by their position in the Periodic Table on a given solvent seem to have been reported. The present paper reports internal friction measurements on silver and on certain silver-base solid solutions to determine the values of room-temperature internal friction associated with varying amounts of plastic deformation and after different annealing

Jan 1, 1957

By M. G. Cheney

The purpose of this paper is to review the more important developments in the production of petroleum during 1930 in Texas, excluding the Panhandle and Gulf Coast districts, giving emphasis to trends rather than to statistics. Outstanding Developments Aside from increasing curtailment of drilling operations and general prorating of production by state authority the most noteworthy developments for the year appear to have been: 1. Demonstrations of the fictitiousness of potentials as shown first by Darst Creek pool, rated at 180,000 bbl. and having actually 78,000 bbl. daily, and especially by the Hendricks pool of Winkler County, with potential of about 1,000,000 bbl. daily in mid-year and production of only 52,000 bbl. daily when opened to continuous full production in December. 2. Rapid development of the Darst Creek pool under competitive drilling. 3. Orderly and highly successful development of the Van pool under unit operation. 4. Failure of several highly rated structures southwest and northeast of Van. 5. Extension of the deep Simpson production at Big Lake and increased interest in these pre-Mississippian pays in North Central Texas and West Texas. 6. Discovery of prolific wells in northwest Rusk County from sands of Upper Cretaceous age, portending a rapid and extensive development campaign around the northwest margin of the Sabine uplift. North Central Texas It appears logical to discuss the new developments by districts as set out by the American Petroleum Institute, but North Texas and West Central Texas districts will be treated together. Pre-Mississippian,.—The pre-Mississippian beds, which in previous years yielded a few large wells in Young, Cooke and Callahan counties,

Jan 1, 1931

By Cornelius Kelley

VOLUMES have been written about the organizing genius of American industrialists. American methods of production are being studied by the manufacturers of other nations to ascertain the prac-ticability to foreign adaptation. Mass production and the mechanization of industry have become terms of popular understanding and significance. Our people think, act and talk in terms of economic nomenclature. Under these circumstances is it not a matter of supreme importance that Americans themselves should make an analysis of their own situation? National supremacy has been but a transitory event. Wealth has had no fixed abode, and commerce has followed no permanently established route. One hundred and fifty years, viewed from the abstract idea of time, is but a moment in the fact of continuous or successive existence, yet it measures. the cycle that has witnessed the growth of America from a struggling embryonic union of thirteen colonies estab-lished along the Atlantic seaboard to the nation of un-rivalled proportions, vast wealth, huge enterprises and productive energy that now exists beneath the protec-tion of and renders allegiance to the flag that but then had been created. To appreciate fully the significance of what has occurred, it is necessary that there should bee an understanding of the basic factors that have con-tributed so largely to the realization of our present situation. Among the most important were: First, the establishment of a government that was founded upon the principle of affording the widest pos-sible opportunity for individual effort and accom-plishment. Second, there existed a virgin territory of vast extent, endowed by nature with elements of potential wealth far exceeding that possessed by any other like area upon the globe.

Jan 8, 1928

By J. H. Wernick

IN a study of the rate of decomposition of %-in. cubes of limestone, dolomitic limestone, and dolomite in a sweeping nitrogen atmosphere, Joseph, Beatty, and Bitsianes' found that the zone of calcination advanced at substantially a constant rate at a given temperature. The purpose of this paper is to show that their data indicate at least two processes occurring when the above carbonates decompose. It is suggested that there are two processes occurring consecutively, one the limiting process in a given temperature range and the other the limiting process over another temperature range. The data of Joseph and co-workers have been extended by use of the Arrhenius equation, Eq. 1, a relation beween the velocity constant k of a reaction and the absolute temperature T. d In k A ' dT Rr2 A is the activation energy in calories per mol (additional energy that must be added for an average molecule to react), and R is equal to 1.986 cal

Jan 1, 1955

By Paul E. Queneau, H. J. Roorda

Cobalt consumption will increase during the next decade at an average rate at least equal that of nickel. In the past, use of cobalt has at times been curtailed by lack of availability or by high price. In the future, output of cobalt derived from copper ores and iron sulfides will continue to grow and output of cobalt from nickel ores will be greatly increased. There should therefore be an adequate supply of this metal at a reasonable price. Nickeliferous limonites constitute by far the largest known terrestrial reserves of cobalt. A process has been conceived, based upon selective reduction and aqueous chlorination for treatment of such ores. The proposed procedure permits good extraction of the ore's cobalt content, comparable to that of the nickel, and is adaptable to large-scale, automated unit operations. Chlorine leaching of the ore enhances its value as a potential source of iron and chromium. Over four thousand years ago, cobalt pigments were employed for decorative purposes in some glass and glazes of Egypt and Persia, and by 1000 B.C. they were widely used in the Middle East.' " However, prior to 1914, virtually no cobalt was produced as metal and ceramics remained the largest consumer of the element as oxide. During World War I cobalt-containing high-speed steels came into their own and the metal's merit in magnet steels was established.

Jan 1, 1971

By A. N. Roberts, N. W. Stump

New developments in on-stream analysis using immersed radioisotope gages including results from plant installations are described. The control of grinding and flotation using a small digital computer has been complemented by this development. A control scheme for grinding, which is based on maximum throughput at constant product size, and preliminary work in flotation control are also outlined.

Jan 1, 1975

An appropriate change in Art. I, Sec. 9, of the bylaws was voted by the Board on April 16 whereby, in the case of Student Associates applying for change of status to Junior Member, only two endorsers are needed instead of three, provided one of them is the same member who endorsed his original application for Student Associateship.

Jan 1, 1952

By H. N. Mills

The glass industry is a major user of many industrial minerals in the manufacture of its product. It is the intent of this chapter to: (1) acquaint the reader with the glass industry by including a few production statistics, and then (2) cover the various aspects of the major raw materials used to make glass. Some of the items covered are: type of materials, their function in glass, their composition, cost, and the relative quantity used in glass vs. totals produced. In addition, a discussion of glass raw material specifications, some byproduct materials used in glassmaking, and comments on future prospects related to the environment, technology, and growth are included. The matter of glass compositions, properties, and batches is considered beyond the scope of this chapter which deals only with raw materials. For more details on the particular minerals and rocks, the reader is referred to the commodity chapters in this book.

Jan 1, 1975

A LARGE attendance at the annual dinner of the Institute, to be held this year on Tuesday eve-ning of convention week, is already assured. Presentation of the Douglas, Hunt and Saunders medals will attract unusual attention since not only in Blaylock, Mathews and Hoover the Institute will be honoring men who have made notable contributions to the advance-ment of their profession, but as to one of them each person as he passes down the reception line will be won-dering whether in renewing acquaintance with our past-president and present Secretary of Commerce, he is not greeting the next president of the United States. Elsewhere in this issue accounts of the professional careers of these three men appear as also of the two younger men, Charles H. Herty, Jr., and P. H. Royster, who are to receive the Robert W. Hunt and the J. E. Johnson awards. Institute honors go for technical achievement, but the Institute will be proud and happy if the nation should later confirm its own judgment by placing larger responsibilities on one of its members. The medals are to be presented at the annual dinner following the President's reception and preceding the dance. There will be no. other speeches and since the occasion falls on Carnival Night a particularly gay evening is anticipated. The event will be at the Wal-dorf as usual, and members are urged to return prompt-ly the reservation cards sent them by mail. Other entertainment features will include a Smoker, Monday evening at 8.15, held at Mecca Temple and in charge of a new committee with Fred Kay of the Petro-leum Division as chairman. He promises that vocal music will not be allowed to interrupt conversation. Lunch will be served each day on the Fifth Floor of the Engineering Societies Building, and ten special luncheons and dinners have been arranged for particu-lar committees and groups as shown by the detailed program. The Woman's Auxiliary has laid out a gen-erous program including luncheons, teas, a theater party on the night the men folks go to the Smoker, visits to museums and, not the least important, a round of the leading shops. The Excursion Committee is arranging for an excur-sion sure to be of interest. The American Smelting and Refining Co. has opened its great Perth Amboy plant to the Institute, and on Thursday, Feb. 23, a party will be taken to it by bus traveling through the Holland Tunnel en route. Full opportunity will be afforded those interested to see the workings of the ventilation system of that great public work. If a sufficient number indicate interest, arrangements will be made for group excursions to other plants in the vicinity of the city.

Jan 2, 1928

By C. H. Gorski

A method for preparing titanium tetrachloride is described which consists of reducing rutile with coke and chlorinating the reduced product at 200° to 500°C. The crude distillate is purified by treatment with copper powder and distillation. Recoveries, exceeding 90 pct of the titanium in the rutile, were obtained. IN recent years considerable interest in metallic titanium has been aroused because of its outstanding physical and chemical properties. The present commercial processes for preparing titanium are modifications of the Kroll1 process and consist essentially of the reduction of titanium tetrachloride with magnesium in an inert atmosphere to produce metallic titanium with magnesium chloride as a byproduct. At present,' commercial titanium tetrachloride costs $0.32 a pound, which makes the price of the included titanium $1.28 a pound. As the titanium tetrachloride must be purified further before processing into metal, its ultimate cost obviously will be higher. Consequently, one of the prime requisites for the production of lower cost titanium metal is a source of low-cost titanium tetrachloride. Recently, Knickerbocker, Gorski, Kenworthy, and Starliper3 escribed a method for preparing titanium tetrachloride from low-grade Arkansas rutile by smelting the rutile with pyrite and coke to form a titanium matte and then chlorinating the titanium matte to prepare a crude titanium tetrachloride. This process had several inherent advantages. Low-grade rutile concentrates were utilized, the chlorination temperature was relatively low (approximately 200°C), and the reaction was strongly exothermic. However, this process had several disadvantages, chief of them being the rather low recoveries of titanium tetrachloride (65 to 81 pct) and the difficulty in purifying the crude titanium tetrachloride obtained. Because of the high-titanium and low-iron con- tents of rutile as compared to ilmenite, rutile should be of greater potential value as a source of titanium tetrachloride than ilmenite. Rutile, however, is not chlorinated directly in commercial practice, because reaction temperatures above 700 °C are required, at which point chlorine attacks most of the common materials of construction. The process now in use consists of converting the titanium in rutile to the cyanonitride by high-temperature reduction in an electric furnace, and then chlorinating this compound. The disadvantages of this process are the difficulty of producing the cyanonitride, the use of high-grade rutile concentrates in the charge, and the presence of several percent of silicon tetrachloride in the finished product. It would be of considerable interest to develop a new process for the preparation of titanium tetrachloride from rutile by chlorination at 200" to 500°C. Process Development Several investigators'-' have studied the reduction of titanium dioxide with carbon in an effort to prepare titanium monoxide. Invariably, the titanium monoxide formed in this manner was not pure, as it contained titanium carbide and one or more of the lower oxides of titanium. As these lower oxides of titanium are more reactive chemically than rutile, and as it is known that titanium carbide may be chlorinated readily, a study was made of the chlorination of carbon-reduced rutile. A sample of rutile concentrates from Hot Spring County, Ark., containing 76.19 pct TiO,, 5.65 pct Fe2O3, 4.18 pct SiO2, and 2.88 pct Al2O3, was used for this investigation. The experimental procedure consisted of making an intimate mixture of —100-mesh rutile and petroleum coke, adding water and molasses as a binder to foi-m a paste, charging into a graphite crucible that was covered, except for a vent to allow the

Jan 1, 1952

By Harry M. Mikami, Harold A. Heiligman

The term chromite is often used to cover all chrome ores and concentrates which are the designations actually employed by most industrial users and producers. Chromite is, of course, the predominant mineral in chrome ores which are aggregates of chromite and gangue minerals, most commonly magnesian silicates. Most chrome ores now used are petrographically chromitites which is a rock, rather than an individual mineral term. The title of this chapter, following past usage, is meant in the broad sense. Chromite is the only primary commercial source of chromium. This book is intended to deal only with nonmetallic minerals and rocks. Chromite uses are both metallic (ferroalloys) and nonmetallic (refractories and chemicals), but any discussion of mineralogy, geology, and mining is common for all types. A number of the major commercial ores are interchangeable, and their uses are determined by economic considerations. Mineralogy COMPOSITION [Chromite is a term embracing a wide range of chromium-bearing spinel*-group minerals the compositions of which can be expressed as (Mg,Fe2+)0.(Cr,AI,Fe3+ )203.t This can be further generalized to R2+O.R23+03 and the molecular RO: R,03 ratio is generally close to one. The exact composition may be arbitrarily expressed as a solid solution of six end-members, MgAI2O4, MgCr2O4, MgFe2O4 FeCr2O4, FeA12O4, and Fe2+.Fe23+04 with the proportions of each stated or plotted in the six-cornered prism of Johnston and Stevens61 or this scheme may be simplified to comprise only three endmembers making up a composition triangle, Fig 1. [ ] FIG 1-Triaxial composition diagram showing molecular compositions of chromites listed in Table 1. The RO.Fe2O3 corner includes Ti02 norms listed in the table. Note that the high-alumina chromites (1, 2, 3, 9), form a cluster well apart from the high-Cr2O3 chromites. There is a tendency for high-iron chromites to be higher in Fe2O3 + TiO2 but it is not a consistent or systematic relationship. The MgO/RO ratio must also be known to characterize the chromite chemically. Simplest and most convenient method is Thayer's' in which a chromite such as (Mg.65Fe.352+)O.(Cr.40Al.50Fe.103+)203 would be written as (Mge,) Cr eAlo. The molecular pro- portions of ferrous and ferric oxides can be seen at a glance as the divalent and trivalent oxides]

Jan 1, 1960

By Walter Hull Aldridge

Much has been said about the foreseeable exhaustion of known mineral reserves-particularly in the United States. It is claimed that we are about to become a have-not nation insofar as certain essential minerals are concerned; and in this respect our position is often contrasted with that of the world as a whole, largely because we have drawn so heavily on our domestic resources during the last fifty years. As a matter of fact, the difference is not great if one takes a reasonably long-term view of the situation. No one denies that nature endowed the United States richer in mineral resources than any other equal area. It is granted that we have skimmed the cream of many kinds of minerals; but in a free international trade in minerals it would not be many decades before the richer deposits-at least the deposits easy of discovery throughout the world would be depleted to much the same degree as those in the United States today. For it is a fact that the problem of satisfying the needs of our industrial society for minerals is fundamentally worldwide in scope. The singular and significant attribute to all minerals is that there is but a single crop. Forests can be grown, but mineral deposits can be replaced only by finding new ones. Thus, one of the vital tasks of the mining engineer, the petroleum engineer, and the geologist is to find these new mineral resources. Another task is to devise means and methods for the exploitation of, at costs that are economic, low-grade deposits and those deeply buried in the crust of the earth. The first need, however, is to find the deposits in the ground. If the assumptions of those who today fear an early exhaustion of all deposits are valid, the outlook for continued material and social progress is gloomy indeed. I take a more optimistic view, for it is my belief that vast new sources of needed minerals will have come to light before our known resources are gone. The real question is whether the outside layer of the crust of the earth that is accessible to engineers contains adequate mineral deposits; and whether engineers can find those deposits. The answer must be based on geologic science, geologic fact, and mining history. Every continent, and almost every country, has yielded minerals of industrial utility in substantial quantity. Mineral deposits are widespread. Geologists know the conditions that were favorable to the occurrence of ores and the types of rocks in which various kinds of ores may ordinarily be found. They know that such rocks occur over broad regions of the earth's surface. They also know that in large areas rocks that are potential carriers of ores are covered and concealed by material of entirely different character. Such cover may consist of lava flows, layers of volcanic ash, or beds of material washed down from the surrounding mountains. Sometimes those covers are thick, sometimes relatively thin. But men well-qualified to pass judgment are sure that concealed deposits, large in number and in size, exist close enough to the surface to make exploitation practical. Only by actual penetration of the surface can this contention be proved, but to conclude otherwise would be to ignore the laws of probability and to deny the over-all consistency of nature. The task of probing the crust of the earth to determine the location of these deposits, and to obtain some notion of their size and quality, poses serious problems. However, they should not be beyond human solution. Much more research must be done in analyzing and explaining the laws of ore deposition. New tools, in the shape of techniques and methods and of mechanical and electrical devices and instruments, must be developed. But no reasonable person can doubt that these objectives will be achieved. As the need becomes increasingly pressing, scientists and engineers will supply the imagination and the ingenuity that will provide the solution. The time and effort thus far devoted to the development of methods for locating hidden ore bodies have been pitifully meager. Energetic investigation of the subject of applied geophysics is essential to the success of the mineral industry, and I have no hesitation in predicting that effective techniques will be found and successfully applied. Twenty-five years ago the petroleum industry

Jan 3, 1950

By E. F. Koch, J. L. Walter

In a study of the structure and properties of tungsten wire used for lamp filaments, it became desirable to perform transmission electron microscopy on the wire in the annealed as well as in the drawn condition. Wire used for lamp filaments is generally drawn to diameters less than 0.010 in. which is too fine for the preparation of transmission samples from single wires. Thus, it is clear that some assembly of wires must be used to form a "wire sheet" similar to that used by Glenn and Duff.' Also, because recrystallized tungsten wire is brittle at room temperature, the "wire sheetJ' must be rigidly contained during any subsequent grinding and polishing operation. With these conditions in mind, a technique was devised for thinning tungsten wire of 0.001 to 0.010 in. diam for transmission electron microscopv. Sample Preparation. The commercially doped (218) tungsten filament wire was obtained from the Lamp

Jan 1, 1969

By A. K. Sinha

The market for thermal coal has recently been growing rapidly and it is projected to continue to do so in the foreseeable future. Both the national and international markets often demand high-Btu low-sulfur thermal coal in order to minimize the cost of utilization and meet the environmental restrictions. High quality thermal coal can be prepared to compete in the utility market by desulfurizing the high-Btu midwestern coal and blending it with low-sulfur western coal which is usually low in Btu content. The methods that can be used for optimizing the coal preparation plant operating parameters for physically desulfurizing coal are presented.

Jan 1, 1985

By Owen W. Ellis, Telfer E. Norman

The use of cadmium as a base for bearing metals is one of the most interesting recent developments in this field. It has caused a strong demand for cadmium and a marked rise in its price. It appeared to the authors, therefore, that the situation might be relieved for users if acceptable substitutes could be developed. A preliminary investigation has revealed that to some extent mercury may be substituted for cadmium. Whether its use is justified cannot be stated at this time. Most of the authors' work has indicated that the addition of mercury to alloys of cadmium and nickel detracts from their desirable physical properties; but this work has not been extended to cover service tests, which might reveal that the addition of low percentages of mercury to the cadmium-base alloys would improve their performance. The results of tests made by the authors are therefore briefly summarized for this paper. Table 1 gives the proportions of the metals used in preparing the alloys. After preparation of these alloys, th composition was checked by chemical analysis. Particular care taken to ensure that the nickel content did not vary appreciably from 1 per cent.

Jan 1, 1938

By Owen W. Ellis, Telfer E. Norman

The use of cadmium as a base for bearing metals is one of the most interesting recent developments in this field. It has caused a strong demand for cadmium and a marked rise in its price. It appeared to the authors, therefore, that the situation might be relieved for users if acceptable substitutes could be developed. A preliminary investigation has revealed that to some extent mercury may be substituted for cadmium. Whether its use is justified cannot be stated at this time. Most of the authors' work has indicated that the addition of mercury to alloys of cadmium and nickel detracts from their desirable physical properties; but this work has not been extended to cover service tests, which might reveal that the addition of low percentages of mercury to the cadmium-base alloys would improve their performance. The results of tests made by the authors are therefore briefly summarized for this paper. Table 1 gives the proportions of the metals used in preparing the alloys. After preparation of these alloys, th composition was checked by chemical analysis. Particular care taken to ensure that the nickel content did not vary appreciably from 1 per cent.

Jan 1, 1938

By G. H. Jardine

In future years, decision makers in the coal industry will make more and more decisions based on information from computer-based models. Whilst the use of such techniques will provide many advantages for coal companies, particularly in terms of efficient utilisation of their human resources, it is equally important for the decision makers to have an awareness of the limitations inherent in each particular computer-based model being used to provide information for the decision making process. A recommended procedure for identifying such limitations - by analysing the 3 major elements of the model - is presented. The human aspects of increased use of computer-based techniques are emphasised throughout the paper.

Jan 1, 1983

By Eric Jette

THE literature on the binary alloys of iron and silicon has been reviewed by Stoughton and Greiner.1 Another even more extensive and detailed survey of the present knowledge has been prepared under the auspices of the Alloys of Iron Research Committee by Greiner, Marsh and Stoughton. Since the latter survey has already been issued in its preliminary form, it will be unnecessary to review the literature in the present article. However, in this connection there should be noted the important work on the crystal structures of the iron-silicon alloys by Phragmén,2 who investigated the entire system, identified the various phases and determined the homogeneity ranges of these phases. It was evident in the surveys cited above that in the range from 0 to 15 per cent silicon, which includes the commercially most' important alloys, the results obtained by thermal analysis, microscopic examination and the determination of electrical, magnetic and mechanical properties were extremely confusing. From time to time various compounds between iron and silicon have been postulated to account for the results yielded by the classical methods, and much argument has ensued. It was presumed that if compounds occurred which are sufficiently diverse in their properties to account for the characteristics of the alloys, they should be recognizable as separate phases but satisfactory proof of this sort has not been found by thermal or microscopic methods. Contrib-uting to the confusion is the fact that the electrical, the magnetic and some of the mechanical properties are "structure sensitive"; i. e., they are influenced to a marked degree by the presence of minute amounts of impurities, the specific characters of these impurities, the grain size, the character of the grain boundaries, small general or local strains, etc. Thus interpretations of the discontinuities in the various property versus composition curves that identified these discontinuities with phase changes or compound formation have always been open to question.

Jan 1, 1933

By Brian W. Mackenzie

Since mineral economics is often coupled with mining engineering in the solution of mineral industry problems, it is important that the principles of this science be a part of the mining engineer's education. Essentially, mineral economics is the application of economic principles to analysis of the multistage process by which minerals are converted from geologic resources to marketable products. In some instances, it may require only the analysis of case studies from a well- developed economics core. In others, however, it requires special skills, because some aspects of the mineral conversion process--such as mineral occurrence, exploration investment and depletion-have no complete parallel in general economics. The mining engineer has been an important contributor to the analysis of mineral economics problems because of his special knowledge of the mineral industry.

Jan 1, 1971

By P. Raffinot, M. Rey, V. Formanek, G. Sitia

Six years of laboratory study, followed by three years of mill operation treating more than 10,000 tons of ore, have established the flotation of oxidized zinc ores with fatty amines as an efficient process. Recently the method has been applied with success to partially oxidized sulphide ores. In this paper the authors give an account of their research and the milling results obtained in Sardinia since 1951. CONCENTRATION of oxidized copper and lead ores by flotation has been practiced for 30 years, but flotation of oxidized zinc ores has remained unsolved until a few years ago. This problem is, however, of great importance in mining districts where large tonnages of oxidized zinc ores exist in underground mines or in dumps. Some sulphide ores also possess a degree of oxidation high enough to justify recovery of oxide zinc minerals. Various attempts have been made to float the zinc carbonate, smithsonite. It is well known' that smithsonite can be collected with fatty acids, but as the predominant gangue constituents, limestone and dolomite. are floatable with the same reagents, fatty acids are difficult to use. Gaudin has shown,' on mixture of pure minerals, that smithsonite can be floated with higher xanthates, or better, with higher mercaptans. Another procedure, briefly mentioned by Davis," consists in sulphidizing the ore, activating the zinc carbonate with copper sulphate, and floating with ordinary xanthates. This process was attempted in the writers' laboratory in 1946, but results were erratic. It has since been taken up by Italian engineers and is in operation on certain types of ores. Two other research projects should be mentioned. In 1942 Erlenmeyer and others' floated synthetic mixtures of smithsonite and gangue minerals with hydroxyquinoline, an analytical reagent for zinc. On the other hand, Bunge, Fine, and Legsdin published in 19465 Some interesting results obtained on Missouri oxidized zinc ores. With sodium oleate as a collector and a combination of sodium hydroxide, sodium silicate, and citric acid as a limestone depressor, they secured, after four cleaning operations, a good grade of concentrate. With many ores this reagent combination lacks adequate selectivity. In 1939 M. Rey initiated a program of research on this important problem. Work was pursued first at the School of Mines in Liége, Belgium"' and later in Paris in the laboratories of Société Miniére et Mbtallurgique de Penarroya and Société Minerais et Métaux. Reagents used in the beginning were higher xanthates and mercaptans, later fatty amines. Sulphidization with sodium sulphide was found necessary. These conditions make possible the flotation of zinc carbonate and zinc silicate. Two milling plants were put in operation in Sardinia in 1950 and several others are now contemplated." ' It should be mentioned that unknown to the present writers McKenna, Lessels, and Peterson were

Jan 1, 1955