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By W. A. Griffith

Fractional replication of factorial design, a general method for planning experimentation and for analysis of data obtained, is described as applied to a flotation investigation. This method leads to determination of optimum process conditions with minimum experimental effort. Its advantages over simple factorial design are demonstrated. A METHOD for planning experimentation and for analyzing the data secured will be demonstrated. This method, termed fractional replication of factorial design, employs a relatively small number of individual experiments to determine which of a large number of process variables are controlling, to determine which combination of levels of these variables is most likely to produce optimum results, and also to predict what results will be obtained with a particular combination of conditions not already tested. Although the general method is not new, having been developed by Finney in 1945,' the extent to which it can improve the effectiveness of applied research generally has not been recognized by metallurgists. The fractional replication procedure is particularly useful in flotation experimentation and an example from such an investigation will be used in the paper. However, it has equal value in any investigation in which similar experimental difficulties are encountered. In developing a flotation process for a particular mineral separation, the investigator is inevitably confronted with the following difficulties: 1—There are a large number of potentially important process variables. 2—Results of individual experiments are not highly reproducible, due in part to the difficulty in precisely controlling all the variables. 3—Considerable effort is expended in conducting individual experiments. 4—There are practical limits on the number of individual experiments which can be made. In situations of just such a type, modern statistical methods of planning experimentation and analyzing data have their greatest value. Applications of one such technique, called factorial design, to problems of this type have been described by Dorenfeld and others.'-' The simple factorial design is an efficient procedure when the investigator hopes to provide a comprehensive understanding of the effects and interrelationships of a small number of variables over a limited range. In applied research, this is seldom the main objective. Rather, the investigator usually wishes to determine which of the many potentially important variables are in fact controlling, which levels of the controlling variables will provide opti- mum metallurgical results, and what these results will be at optimum conditions. Interest in detailed trends is limited to the controlling variables and to levels in the region of optimum conditions. Simple factorial design has serious deficiencies for such objectives and is not the most efficient method of experimental design. Deficiencies of Factorial Design In a simple factorial design, an experiment must be made at every possible combination of each level of every variable, once these have been chosen and the levels of each to be included have been decided upon. As the number of variables or levels of each increases, the experimental program quickly reaches prohibitive size. For example, an investigation of only four variables, each at four levels, requires 256 individual experiments. Often upon completion of such an extensive program, it is found that one or more of the variables has metallurgically unimportant effects or that a poor estimate has been made as to the appropriate range of levels to be investigated. The result is that only a small proportion of the data obtained falls in the range of real metallurgical interest. Indeed, it frequently can be anticipated that certain combinations of levels of variables will not produce results of interest, but they still must be included so that the essential balance, or orthogonality, of the design will be retained. It may be true that factorial design will provide the greatest amount of information from a given number of experiments, but it does not necessarily follow that it will lead to the desired information with a minimum number of experiments. Much of the information provided may be of little value. Advantages of Fractional Replication The disadvantages of simple factorial design are overcome to a great extent by a modification known as fractional replication. This is a technique for sampling systematically the potential data of a full factorial experiment, that is, the data which would have been obtained if the complete factorially designed program had been completed. Only a fraction of the total array of experiments is made, but the experiments are chosen in such a way that the important advantages of factorial design and the accompanying analysis of variance are retained. The data obtained from the first group of experiments are used to determine which of several variables are controlling and which levels of these variables are most likely to produce the desired result. Unimportant variables and levels of variables then may be

Jan 1, 1956

By A. J. Fenn

Cananea is located at an elevation of 5,200 ft in the north-central part of the state of Sonora, Mexico, about 135 miles northeast of Hermosillo, the state capital, and about 30 miles south of the United States border. A graded road runs to Cananea from the border town of Naco, near Bisbee, and a branch road turns east to Cananea at Imuris, a town 36 miles south of the border on the Nogales-Hermosillo highway. Railway service is provided by a spur from the Nogales-Naco branch of the Ferrocarril del Pacífico Railroad. Fuel for the power plant, smelter, and town (population approximately 20,000) is natural gas, supplied through a pipeline from the United States. The Compa[n]ía Minera de Cananea generates electric power for its own installations and also supplies both electricity and water to the town. HISTORY The earliest record of mining in Cananea dates back to 1760, when Jesuit fathers worked the Cobre Grande mine for silver in spite of resistance from hostile Indians. About 1800, several mines were worked on a relatively large scale by the House of Guea of Chihuahua. From then until about 1890 when William C. Greene of Fairbanks, Ariz., acquired control of a large group of properties, mining continued in a rather sporadic manner. The mineralized district is approximately 6 miles wide and 15 miles long, and the orebodies are associated with breccia pipes and granitic intrusive rock. In the early days, many small mines operated within the area on high-grade orebodies. In 1899, Greene promoted the building of a mill and smelter and established the present company, The Cananea Consolidated Copper Co., S.A., now Cia. Minera de Cananea (S.A. de

Jan 1, 1969

By Etienne A. Ritter

INTRODUCTION. THE Evergreen mine, located at Apex, in the northern part of Gilpin county, Colorado, has opened a very peculiar and interesting copper-deposit, in which both bornite and chalcopyrite occur as rock-minerals. The country-rocks are crystalline schists cut by dikes of granulite and of pegmatite. At the Evergreen property they have been cut by a dike of a new kind of eruptive rock, to which I have given the name " Evergreenite" The rock is composed of quartz, alkali feldspars, orthoclase and albite (often interlocked as microperthite), with augite of the aegirine variety and long needles of enstatite and diallage. For reasons stated below, I believe the dike to be of Tertiary age. It is- easily traced on the surface of the ground, from a point in the bottom of Pine creek, about a mile below Apex,. to the top of Nevada hill, 1,500 ft. beyond and 600 ft. above it. (See Fig. 1.) It varies from 3 to 12 ft in width, and is bounded on both sides by contact-zones about 60 ft. wide, in which the crystalline schists have been changed into pseudo-quartzites or pseudo-gneisses, according to the injection of an excess of quartz or of feldspars through the special layer of the schists.. The most interesting feature is the presence of the pyroxenes, which are always found, though in very variable proportions from place to place, in the layers of these' metamorphosed crystalline schists. The dike has torn from its walls a large number of fragments of the wall-rock. It must have been in a viscous state when that happened, because these fragments of the wall-rock do not show any sign of resorption or of assimilation by the magma. In places they are so distinct and so numerous that the rock looks to the naked eye like a pseudo-breccia, of which, never-

Jan 1, 1908

The Industrial Minerals div. has been forging ahead in formulating a program for the February Annual Meeting in Los Angeles. Several papers have been listed and more are being worked into the program. For the cement, lime and gypsum part of the sessions, papers on Gypsum in the Aircraft Industry, Geology of San Marcos Island Gypsum Deposit, and Status of New Dry Rotary Blast Hole Drills, are expected. The Chemical Raw Materials sessions will feature a symposium on potash, with 13 papers as the anticipated number to be presented. Airborne and Ground Magnetometer Work has been suggested. Eight papers have been set for Mining Geology, Four papers, Mining Phosphate Rock, Idaho Phosphorous, and Geology of Carlsbad Potash and Geology of Pearlite will be on the program. Sessions on Dimension stone and slate have been tentatively worked out with papers on Geologic Factors Affecting the Dimension Stone Industry of California, A Quarter Century of Granite Quarrying in Massachusetts, Rock Bursting and Other Geologic Problems in the Granite Quarries of Barre, Vt., Quarry Practices in the Indiana Building Stone Industry, Stratigraphy and Composition of the Salem Limestone, and Dimension Stone in the U. S. in 1952. The Rare Minerals Committee is aiming for six papers with two papers now definitely on the program.

Jan 1, 1952

By C.R. Taylor, John Chipman

The study of chemical reactions of liquid steel and basic open-hearth slag involves a complex slag system of at least eight important components, and often a number of others. In initiating an experimental program on the equilibrium relationship of slag and metal, it became evident that but little progress could be expected in the interpretation of the complex slags until an understanding had been gained of the simpler liquid systems composed of a limited number of slag constituents. The simplest system that in any way resembles open-hearth slag must contain lime, silica and iron oxide. Attempts to produce in an induction furnace slags containing only these constituents have met with serious limitations because of the solubility of refractories in the slag. Thus in acid-lined furnaces the slag is always saturated with silica and consequently contains between 48 and 63 per cent of this component. In basic-lined furnaces an undesired additional component, magnesia, is introduced to the extent of some 3 to 15 per cent, depending upon the acidity, sometimes with disastrous results to the furnace. Thus in a magnesia-lined furnace, Fetters and Chipman1 found it impossible to prepare slags in which the ratio (CaO + MgO)/SiO2 was less than that corresponding to the metasilicate (approximately 0.8:I). Between this composition and that of the true acid slags lies a field of composition about which very little is known and which cannot be explored by any ordinary means. This circumstance, as well as the desire to study the more basic slags in the absence of magnesia, calls for the development of a method by which slags may be brought into equilibrium with molten metal without coming in contact with refractory. Such a technic has been provided by the rotating induction furnace developed by Barrett, Holbrook and Wood.2 Three modifications of the rotating furnace were described by these authors. The first was essentially a rotating refractory cylinder containing the magnesia crucible, which was itself heated by a graphite crucible. In the second, only the magnesia crucible rotated, the cylindrical graphite heater being stationary. In the third, the coil and crucible revolved, and the metal was heated directly by induction. Experimental Method Furnace The furnace used in this investigation differed from previous designs and may be Sci- a fourth modification of the original rotating furnace. Its essential fea tures are shown in Fig. I' The Outer case A is a fire-clay flue liner for control of the atmosphere. The top B and base 6 are alberene stone. The coil supports D are of ""Formica," a material formed from phe-

Jan 1, 1943

By C. R. Taylor, John Chipman

The study of chemical reactions of liquid steel and basic open-hearth slag involves a complex slag system of at least eight important components, and often a number of others. In initiating an experimental program on the equilibrium relationship of slag and metal, it became evident that but little progress could be expected in the interpretation of the complex slags until an understanding had been gained of the simpler liquid systems composed of a limited number of slag constituents. The simplest system that in any way resembles open-hearth slag must contain lime, silica and iron oxide. Attempts to produce in an induction furnace slags containing only these constituents have met with serious limitations because of the solubility of refractories in the slag. Thus in acid-lined furnaces the slag is always saturated with silica and consequently contains between 48 and 63 per cent of this component. In basic-lined furnaces an undesired additional component, magnesia, is introduced to the extent of some 3 to 15 per cent, depending upon the acidity, sometimes with disastrous results to the furnace. Thus in a magnesia-lined furnace, Fetters and Chipman1 found it impossible to prepare slags in which the ratio (CaO + MgO)/SiO2 was less than that corresponding to the metasilicate (approximately 0.8:I). Between this composition and that of the true acid slags lies a field of composition about which very little is known and which cannot be explored by any ordinary means. This circumstance, as well as the desire to study the more basic slags in the absence of magnesia, calls for the development of a method by which slags may be brought into equilibrium with molten metal without coming in contact with refractory. Such a technic has been provided by the rotating induction furnace developed by Barrett, Holbrook and Wood.2 Three modifications of the rotating furnace were described by these authors. The first was essentially a rotating refractory cylinder containing the magnesia crucible, which was itself heated by a graphite crucible. In the second, only the magnesia crucible rotated, the cylindrical graphite heater being stationary. In the third, the coil and crucible revolved, and the metal was heated directly by induction. Experimental Method Furnace The furnace used in this investigation differed from previous designs and may be Sci- a fourth modification of the original rotating furnace. Its essential fea tures are shown in Fig. I' The Outer case A is a fire-clay flue liner for control of the atmosphere. The top B and base 6 are alberene stone. The coil supports D are of ""Formica," a material formed from phe-

Jan 1, 1943

By Boyd Guthrie, J. D. Lankford

A progress report on the oil-shale and shale-oil processing research program at the U. s. Bureau of Mines Oil-Shale Demonstration Plant. Legislation providing for the program and aims are briefly noted. The remoteness and rugged nature of the terrain at the plant site are important factors in construction and operations. Large-scale units now in operation are the crushing plant and two 40-ton N-T-U retorts. These are described in detail. Under construction are several retorting pilot plants and a 200 bbl per day refinery. The refineiy incorporates several types of thermal operation, three-stage low-temperature acid treating, doctor sweetening and rerunning. Data are presented on typical N-T-U retort runs. Yields of 90 to loo pct of assay are realized on 30 gal to the ton shale with a retort cycle time of 18 hr. Data also are presented showing a comparison of a Mid-Continent petroleum and N-T-U shale oil. This comparison indicates that shale oil has a high pour point, low API gravity, and contains about 0.8 pct sulphur and 2 pct nitrogen. The naphtha fraction contains 3 pct tar acids, 9 pct tar bases and jo pct olefins. The problems involved in refining shale oil into usable products are discussed in detail. Introduction The Bureau of Mines oil-shale program now under way at Rifle, Colo., was begun in July 1944 under the provisions of the Synthetic Liquid Fuels Act, which was passed in the spring of that year under the sponsorship of Senator Joseph C. O'Ma-honey of Wyoming and Congressman Jennings Randolph of West Virginia, aided by Michael W. Straus, former Assistant Secretary of the Interior, and others. The oil-shale plant is only a part of the Office of Synthetic Liquid Fuels, Bureau of Mines, which has under way projects to develop synthetic liquid fuels from coal and other solid materials at Pittsburgh and Bruceton, Pa., Morgantown, W. Va., Louisiana, Mo., as well as the Petroleum and Oil-Shale Experiment Station at Laramie, Wyo., and the oil-shale demonstration plant at Rifle. The oil-shale program is entirely experimental. It is not intended that oil will be produced in great quantities. Production will be limited to the volume obtained from plant-scale experimental operations, which will be kept to the minimum size needed to develop techniques and processes and to demonstrate costs. After the passage of the enabling act in the summer of 1944 a survey of the oil-shale resources of the Nation was made to determine the most suitable general area in which to establish the demonstration plant. The most suitable area was found to be in the Rifle-De Bequearea in Garfield County, western Colorado. Bureau of Mines field parties covered this entire area thoroughly

Jan 1, 1949

Discussion of the paper of DORSET A. LYON and ROBERT M. KEENEY, presented at the Salt Lake meeting, August, 1914, and printed in Bulletin. No. 92, August, 1914, pp. 1791 to 1800. LAWRENCE ADDICKS, Chrome, N. J.-I read this paper for the first time this afternoon, and it is really worthy of a much more careful reply than I can make with such a short time to consider it, but I just want to say that I differ with Dr. Lyon in his premises and conception of what happens in a refining furnace. He cites steel as an instance where the production of special grades justifies the high cost of power in an electric furnace, and goes on to say the same will be true in the case of copper, for the reason that you will get a better quality of product. I don't think you will get a higher grade of copper,. or a better conductivity, as I will explain in a moment. The cost of fuel in the Eastern plants is somewhere between 30c. and 40c. per ton of copper refined, and, if my memory serves me correctly, in an open-hearth steel furnace it is something like $1.25, so it is evident that steel could be handled to better advantage than copper on the basis of fuel. Now, taking the Great Falls plant to compare with is not quite fair, because that plant operates under peculiar conditions. The furnaces are relatively small; the coal is very bad and is very high in sulphur. No one would think of using a coal with 3.6 per cent. sulphur were anything better available. Due to these conditions, the amount of slag is inordinate, it being quoted as 3.5 per cent., and it is necessary to use lime, as there is a tendency to have troubles from arsenic owing to the very high current density used. I think he has taken about as hard a case as he could pick out. Now as to the conductivity of copper, my own idea about the reason that melted copper does not give as high a conductivity as pieces drawn directly from a cathode, or native copper, is that in the latter case the impurities are present as a mechanical mixture, while after melting they are chemically combined with the copper, which is a very different condition. Further, it is necessary to take the sample from a relatively smooth and consequently pure part of the cathode, as otherwise it would not draw. The same with the mass of copper; you pick out a good solid part of the copper, which is not representative. In fact, the refiners have all found they could not take fair samples of cathodes for a chemical analysis. It is always customary to use wire-bar copper -for the purpose of sampling, and the impurities are several times as great as shown by samples taken from .the cathodes. I think if we examine all of the examples he has given of cases where copper is higher in conductivity, it will fit with that explanation. For example, the Elmore process is a direct electrolytic deposit. Incidentally, at the present time there are a number of ex-

Jan 12, 1914

The Secretary of the Treasury, acting through the National War Savings Committee, soliciting the support of patriotic associations in America in the sale of War Savings Stamps, has addressed the following letter to the President of the Institute: It is particularly desirable to have you urge the members of your association to give their assistance wholeheartedly, and to this end we urgently request that you write a letter to each of your members, outlining the aims of this campaign. That you may more easily draft your letter, we mention a few things in which your members could render a special service. Agencies and Sales Stations.-We desire immediately to establish several hundred thousand agencies and sales stations. It is as easy to sell a War Savings Stamp as it is in ordinary postage stamp, and we have launched a great drive to establish sales stations everywhere. The plan is simplicity itself! Your town, city, county or State Director can furnish you with supplies, posters and publicity matter. You can get the stamps from your post office or bank. Such stations should be at every pay window of manufacturing, industrial and mercantile establishments, and at every retail counter in the country. These stamps should be the easiest bought merchandise in the world, and when these agencies are established this end will have been accom-plished. Therefore, please lay extra pressure on the thought of immediately establishing these sales stations.

Jan 3, 1918

By R. D. Fisher, A. G. Metcalfe, F. A. Crossley

AN investigation of the application of magnetic stirring to the consumable arc melting of aluminum and nickel demonstrated that grain refinement could be obtained when there was sufficient stirring force. Also, it was found that grain refinement could be obtained in aluminum by alternately reversing the polarity of the current through the magnetic stirring coil. The effect of the latter was to periodically reverse the direction of rotation of the molten metal.' Because of their promise, these findings were applied to conventionally cast aluminum. Shortly after this work was begun, Kondic2 reported experiments in which aluminum cast with 40° C (72° F) of superheat exhibited a grain size of 10 to 20 grains per cm2. When interrupted rotation was applied during solidification by mechanical means, a grain size of 800 to 1000 grains per cm2 was obtained. Magnetic Stirring Applied to Conventional Casting— The applicability of magnetic stirring to producing grain refinement in conventionally cast metal was evaluated in the following way. Three pounds of aluminum were cast into a clay-bonded graphite mold. The mold was surrounded by a magnetic stirring coil of 1000 turns. A direct current of 200 amp was passed through the casting by means of a graphite electrode which was immersed from the top. A current of 5 amp was passed through the stirring coil. The aluminum (1100 or 25) was superheated to 1600° F (871° C) and fluxed by passing chlorine gas through the melt for 2 min prior to casting. Two additional castings were made for comparison: 1) a conventional casting of metal superheated to 1600° F and 2) a similar casting through which 200-amp current was passed during solidification, but without current in the magnetic coil. Macrosections of these three ingots are shown in Fig. 1. Very remarkable grain refinement resulted in the magnetically stirred casting. It may be noted that the casting through which 200-amp current was passed has a coarser structure than the conventional casting. It would appear that this is due to the additional heat input generated by the current to the former casting. Mechanical Rotation Applied to Conventional Casting—A casting temperature of 1600° F was used throughout. Some 1 1/2 -lb castings rotated at 150 rpm were predominantly columnar with small areas of coarse, equiaxed grains close to the lower mold wall. Following these, a series of 3-lb castings was made. Macrosections of these ingots are shown in Fig. 2. The imposed rotational speed was 250 rpm. Turbulence or acceleration in the solidifying liquid was the significant factor. Fine grain size resulted in the material solidified during the period of acceleration of the liquid to the imposed rotational speed. When uniform rotational motion was achieved, the grain structure reverted to columnar. The final casting shown in the lower right-

Jan 1, 1962

By W. R. Opie, O. W. Mole

By confining the electrolytic reduction of TiCl4 to the interior of a porous basket-cathode the electrolyte between the anode and the cathode can be kept free of reduced chlorides of titanium eliminating undesirable reactions of reduced titanium chlorides with brickwork or oxygen in the cell atmosphere. Semiwalls are not needed. Operating conditions are given and discussed. Titanium yields based on TiCl4 introduced are 93 pct. Cell voltage and amperage characteristics are adaptable to multiple cathode-series cell urmngements. EXPERIMENTS conducted in the National Lead Co., Titanium Division, Research Laboratories showed that titanium metal could be deposited in an electrolytic cell in which titanium tetrachloride was introduced through a tubular cathode.' The reduced chlorides as formed were confined to the vicinity of the cathode. They were reduced to form a cocoon-shaped growth of sponge titanium metal at the end of the cathodic tube below the surface of a sodium chloride-strontium chloride electrolyte. No diaphragm was needed.' Although high-purity, coarse crystalline metal was produced in the cocoon growth, the yields of metal removed from the cell, based on the amount of titanium introduced as TiCl4, were usually only 40 to 60 pct. The growth of the cocoon deposits was away from the cathodic tube for introduction of TiC14 toward the anode following the flu lines. The reduced chlorides of titanium diffused through the deposit and were reduced to titanium electrolytically within the deposit or on the outer surfaces. Deposition within the pores of the cocoon was detrimental to further deposition because it plugged the passages used by the reduced chlorides to diffuse away from the point of titanium introduction. As plugging due to deposition in the pores proceeded, the reduced chlorides in the center of the cocoon would force their way out by forming a channel and would escape from the vicinity of the cathode without being reduced to metal. Some work had been done previously1, 2 which indicated that if the end of the cathodic tube for introducing TiC14 was surrounded by a screen connected to the tube so that it too was cathodic, growth could be made to occur within the screen. Direction of growth was observed to be from the screen toward the point of TiCl4 introduction. Through a series of design modifications a cathode evolved which consisted of an introduction tube surrounded by a perforated metal basket as shown in Fig. 1. Modifications of this design are described in Refs. 3, 4, and 5. This basic cathode designa" was incorporated in electrolytic cells containing graphite anodes and constructed of high-silica brick refractory for containing the electrolyte (see Fig. 2). The inner crucible was surrounded by insulating brick and the entire unit contained in a welded steel shell. Suitable cooling chambers with inert gas atmospheres were devised so that the cathode could be removed from the cell without exposing the deposit to air while hot. Various alkali and alkaline earth chlorides were used as electrolytes.

Jan 1, 1961

From the cold Pacific waters in June rolls a blanket of white clouds that tucks up around the mountains at around 8000 or 9000 ft. This is the way it happens in southern Peru and so the mining operations and daily living at Toquepala have an ethereal quality not often encountered. Besides looking down on the clouds from the brightly sunlit mountain tops, one can discern the trace of a different era in the brown barren mountain slopes. This trace is like a delicate net laid over the surface of the earth-a criss-crossing of innumerable trails that are so omnipresent, yet faint, that the local people have long since ceased to notice them. It is difficult at first to ask about them because no one understands what you are talking about. It finally comes out though, that the markings are indeed trails, but fossil trails made by animals in times when they were in abundance in a countryside that was green in some bygone century. In a way Toquepala is still pristine, it is the way the engineers planned it-from the ground up. There are no additions or expansions- those tackings-on that spoil the symmetry of design while increasing the profit. This does not deny that annual production has gone up over the years. Daily mill throughput has been increased from 30,000 to 42,000 tpd. Initial design of the concentrator was for 30,000 tpd but in 1964-65 milling capacity was increased to 36,000 tpd at a cost of $3 million.

Jan 11, 1969

By Keith Leonard Sutherland, Ian William Wark

Mercaptobenzthiazole and its sodium salt are marketed under the trade names Flotagen and Flotagen S respectively, for use as collectors for cerussite and other minerals. The structural formulas for sodium rnercaptobenzthiazole and for sodium ethyl xanthate are: Chemically there is a resemblance between the two compounds, though the free acid (mercaptobenzthiazole itself) is much more stable than xanthic acid. Both are readily oxidized, e.g., by iodine to disulphides, and can be estimated by iodometric titration. Qualitatively they are similar as collectors in flotation, although there are quantitative differences between them that may be important in practice. It is deduced that the influence of the nitrogen atom is subordinated to that of the sulphur atoms, and that the dominant group of these compounds is the mercapto group —SH or —5Na. The general method of investigation has been based on contact tests. Two temperatures, 10" and 35" C., have been chosen, and with a standard concentration of 20 mg. per liter of mercaptobenzthiazole (i.e., of the free acid) the influence of alkali, cyanide and copper sulphate on contact at sulphide mineral surfaces has been studied. This standard concentration corresponds to about 19 mg. per liter potassium ethyl xanthate; it brings out the differences between the minerals better than a higher concentra-

Jan 1, 1939

By Ian William Wark, Keith Leonard Sutherland

Mercaptobenzthiazole and its sodium salt are marketed under the trade names Flotagen and Flotagen S respectively, for use as collectors for cerussite and other minerals. The structural formulas for sodium rnercaptobenzthiazole and for sodium ethyl xanthate are: Chemically there is a resemblance between the two compounds, though the free acid (mercaptobenzthiazole itself) is much more stable than xanthic acid. Both are readily oxidized, e.g., by iodine to disulphides, and can be estimated by iodometric titration. Qualitatively they are similar as collectors in flotation, although there are quantitative differences between them that may be important in practice. It is deduced that the influence of the nitrogen atom is subordinated to that of the sulphur atoms, and that the dominant group of these compounds is the mercapto group —SH or —5Na. The general method of investigation has been based on contact tests. Two temperatures, 10" and 35" C., have been chosen, and with a standard concentration of 20 mg. per liter of mercaptobenzthiazole (i.e., of the free acid) the influence of alkali, cyanide and copper sulphate on contact at sulphide mineral surfaces has been studied. This standard concentration corresponds to about 19 mg. per liter potassium ethyl xanthate; it brings out the differences between the minerals better than a higher concentra-

Jan 1, 1939

By C. G. Durdaller, W. H. Robinson, G. M. Pound

The nucleation rate of the a (pay) to 0 (white) tin transformation was measured as a function of temperature and a tin particle size using an X-ray diffraction technique. The powder specimens of a tin were essentially monodisperse and the small dinzension of the particles of these specimens was varied from 13 to 75 p. Several types of nucleation sites of differing potency were fbund to be operative in the nucleation process, but it could not be determined whether these sites were on the free surface of the tin particles or within the volume. Assuming that they were on the free surface, the average density of the most potent sites was calculated to be 2.5 to 5.3 x 10' sites per sq cnz through the application of a Poisson distribztion finction to the isothermal data. Analysis of the temperature dependence' of the rate constmts at a given fraction transformed suggests that the active sites are regions of higher free energy and not catalytic interfaces. Appreciable induction periods were observed at the lower temperatures of transformation. Experimental studies1 of solid-solid phase transformations have led to the belief that the new phase nucleates at structural imperfections. The purpose of the present work was to learn more about the mechanism of nucleation in solids and the nature of the singularities at which nucleation occurs. In this investigation nucleation rates in the isothermal transformation of gray to white tin were measured by an X-ray diffraction technique using essentially monodisperse powders of gray tin. This particular phase transformation was chosen for study because it presented fewer experimental difficulties than most others. The experimental temperature-control problems were minimal because the two phases coexist in equilibrium at 13.3"C, and measurable transformation rates occur at temperatures only slightly above room temperature. The growth rate of the P phase into the a2 is sufficiently fast to make the measured transformation rate equivalent to the nucleation rate, provided that the particle size of the samples is small enough; for the experimental temperatures used in this study, the particle diameter must be less than 100 p. EXPERIMENTAL TECHNIQUE The P tin used in this study was obtained from Capper Pass and Son Ltd., North Ferriby, Yorkshire, England, and was of 99.999 pct purity. It was transformedS to the a phase and ground into a fine powder in an agate mortar. This powder was separated by a Roller air classifier into seven fractions whose dimensions, as determined by microscopic measurement of many thousands of particles, are given in Table I and whose distribution of size within each fraction is given in Figs. 1 and 2. The shape of the particles was roughly that of an oblate spheroid,

Jan 1, 1964

By Richard H. Terhune

It cannot be said that the development of processes for roasting in Utah has been evolutionary. Some of the best systems were contemporaneons with smelting here, and one of the most primitive methods, pile roasting, is still entrenched, to the exclusion of all others, at one works. This is certainly not because we have not had sulphur, in place and out of place, to contend with, but rather because roasting has not been a necessity, we having, like most other smelting districts in America, a good share of oxidized ores.

Jan 1, 1888

By C. L. Mantell

When considered from the viewpoint of world annual output, tin is one of the rarest metals. Its annual production is exceeded by that of iron, copper, lead, zinc. aluminum, magnesium; probably by that of the ferroalloys of manganese, chromium, and silicon, and possibly by the world production of sodium; while it exceeds only the output of such common metals as nickel, antimony, mercury, tungsten, molybdenum, silver, gold and the precious metals. Cassiterite, or tinstone, until the second World War was the only mineral that was an important source of tin. This mineral is frequently called "tin ore." The use of the term should be restricted to the ore containing the mineral, and not, in addition, to the concentrates of the mineral obtained from the ore or from stanniferous alluvial deposits. There is a general misuse of the term "tin ore" in the Malay Peninsula and adjacent localities, particularly where most of the mineral is obtained from secondary stanniferous deposits. The term "cassit-erite" is exclusively used in mineralogical, geological, and other scientific writings; it is unfortunate that it is not mole frequently used when referring to the occurrence of the mineral on an economic scale. Ores "Tinstone" js a very convenient old English term deserving a more frequent use. Tinstone is a dioxide of tin, or stannic oxide. When chemically Pure, as in the very rare transparent variety, it has a metallic content of 78.6 per cent tin. Frequently, however, the crystals and grains contain appreciable amounts of impurities, chiefly iron and tantalum. The impurities here referred to are those actually in the mineral itself. Tinstone usually has a deep brown or black color with an adamantine luster. Several other colored varieties are known, among them red ruby tin, yellow rosin tin, and yellow wax tin. the names jn each case being descriptive of the mineral's appearance. Ainalite is a variety of cassiterite con-taining almost g per cent of tantalum pentoxide. Sparable tin, tooth tin, and needle tin, as a result of their acute dite-tragonal pyramidal crystalline form, re-ceive their names from their crystallo-graphic appearance. Wood tin is a compact variety of cassiterite composed of radiating fibers resembling dry wood. Toad's-eye tin is a similar variety on a smaller scale in which the fibers appear to resemble the eye of a toad. Stream tin is water-worn tin-stone. Float tin is sometimes employed to describe the cassiterite occurring in soil derived from the weathered surface of a mineralized area. Stannite is an ore of tin of lesser impor-tance than cassiterite. It is a sulphide of tin, copper, and iron, sometimes known as tin pyrites or bell-metal ore. Its chemical com-position is sometimes expressed by the for-mula Cu,S.FeS.SnSz with zinc usually present in varying quantities. The tin con-tent varies from 22 to 27 per cent and there is about 29 per cent of copper, 13 per cent of iron, and 30 Per cent of sulphur.

Jan 1, 1944

By E. A. Reilly, G. R. Gardner, F. P. Lasseter

THE methods that may be applied to the treatment of slurries and water, as these are related to practical coal-preparation problems, are concerned essentially with the movements of solids suspended in water. It is assumed that there are no fundamental differences between the principles involved in the treatment of coal slurries and the phenomena encountered in general mineral-dressing practice, and the latter are presented in some detail. Basic principles ,are correlated with present practice for both the anthracite and the bituminous coal fields, and methods are discussed which are designed to utilize best all the material subjected to treatment and suggest a sound approach to the solution of problems relating to the return of clear water to process or to streams. In order to approach the practical phases of the subject with sufficient understanding of the basic principles, it is necessary to discuss two types of phenomena that are applicable. The first is flocculation and the second is sedimentation. Descriptive matter is given covering the various methods and types of equipment employed to conduct these operations, with emphasis on their application to water and coal-slurry treatment. DEFINITION OF TERMS Definitions of terms are consistent with modern developments, and on form, in general, with their usage in mineral-dressing practice. Because of variations in coal-preparation methods, it is impossible to define a rigid upper limit of particle size for a coal slurry or sludge which will apply generally. Limits vary somewhat with the particular treatment method employed at a given plant. For purposes of definition, this limit is chosen as the particle size for which preparation methods such as Chance cones and jigs are usually dispensed with, and other methods, such as the Hydrotator, tables, and froth flotation, are employed. Generally the limit will be 10 to 6 mesh. In assuming this variable upper limit of particle size in a coal slurry, it is recognized that the size ranges discussed will duplicate sizes dealt with

Jan 1, 1943

By Gustaf Ising

For relative gravity measurements, the author in 1918 described an instrument1 of which the essential part consists of a highly astatized, standing pendulum turning about a horizontal elastic axis. This type of instrument has been used recently in practical field work, therefore a description of its principle and technical development is given herein. Part I, describing the principle, is a direct translation of the original Swedish paper.l Part II gives an account of the practical elaboration of the instrument, together with some description of measurements performed. I. Principle of Using Astatized Pendulums1 In order to reduce the trouble and waste of time attending the use of ordinary pendulums in measuring the force of gravity, various instruments of another type have been suggested for relative determinations, as a rule arranged in such a way that the attraction of the earth on a certain body or mass of fluid is balanced by elastic force from a spring or a shut-in mass of gas. A change in the force of gravity is then made manifest as a change in the position of equilibrium of the body, in that the deformation of the spring (or compression of the gas) is changed. With such instruments there are, however, great difficulties in keeping the elastic force constant or its variation known with sufficient exactitude, because of elastic after-working, influence of temperature, and so on. The author suggests for relative determinations of gravity another type of instrument, in which two directional forces (control coefficients) rather than two forces are compared with one another. By "directional force" or "control coefficient" is meant that quantity in a rotatable system that, multiplied by the angle of deflection, indicates the moment counteracting the deflection. In this way it will be possible greatly to reduce the influence of the elastic after-working, which in instruments with spring devices acts so disturbingly. The instrument is made with a rotatable system arranged in such a way that the total control coefficient acting upon it, is composed

Jan 1, 1940

By Gustaf Ising

For relative gravity measurements, the author in 1918 described an instrument1 of which the essential part consists of a highly astatized, standing pendulum turning about a horizontal elastic axis. This type of instrument has been used recently in practical field work, therefore a description of its principle and technical development is given herein. Part I, describing the principle, is a direct translation of the original Swedish paper.l Part II gives an account of the practical elaboration of the instrument, together with some description of measurements performed. I. Principle of Using Astatized Pendulums1 In order to reduce the trouble and waste of time attending the use of ordinary pendulums in measuring the force of gravity, various instruments of another type have been suggested for relative determinations, as a rule arranged in such a way that the attraction of the earth on a certain body or mass of fluid is balanced by elastic force from a spring or a shut-in mass of gas. A change in the force of gravity is then made manifest as a change in the position of equilibrium of the body, in that the deformation of the spring (or compression of the gas) is changed. With such instruments there are, however, great difficulties in keeping the elastic force constant or its variation known with sufficient exactitude, because of elastic after-working, influence of temperature, and so on. The author suggests for relative determinations of gravity another type of instrument, in which two directional forces (control coefficients) rather than two forces are compared with one another. By "directional force" or "control coefficient" is meant that quantity in a rotatable system that, multiplied by the angle of deflection, indicates the moment counteracting the deflection. In this way it will be possible greatly to reduce the influence of the elastic after-working, which in instruments with spring devices acts so disturbingly. The instrument is made with a rotatable system arranged in such a way that the total control coefficient acting upon it, is composed

Jan 1, 1940