Search Documents

By Carle R. Hayward

(Wilkes-Barre Meeting, June, 1911.) THE growing importance of metallography has caused a corresponding interest in the improvement of apparatus for preparing specimens of metals and alloys for microscopic examination. The purpose of this paper is to describe an electric heating-furnace, a grinding-and-polishing machine, and a device for mounting specimens, which are used in the metallographical work at the Massachusetts Institute of Technology. These three pieces of apparatus were designed and made in the laboratory of the Institute, and. each possesses some original features which may be of interest. ELECTRIC HEATING-FURNACE., The accurate control of heat necessary for metallographic work is best obtained by the electric-resistance furnace. Unfortunately, however, even the platinum-wound furnaces deteriorate with use and ultimately burn out, while the cheaper resistance-materials are often short-lived. Since the resistance-coil must be replaced from time to time, it is of advantage to be able to make this change with as little trouble as possible, and this is an important feature in the furnace shown in Fig. 1. A is a cylindrical galvanized-iron can, with two handles, B. A porcelain tube, C, passes through the central hole in the cover of the can and rests upon the asbestos disk, D; the bottom of the tube is held in place by the asbestos ring, E. The space, F, around the tube is filled with powdered magnesia. G is an ordinary assay-crucible, with the cover inverted so as to present a smooth top for supporting a second porcelain tube, H. The latter is wound with ?Excello " resistance-tape, 0.014

Dec 1, 1911

By Charles E. Locke

PROSPERITY of the gold miner has continued with attendant construction of numerous plants, many of them small but some of good size. Many new mills have been erected in Canada and in the Philippines, end one should mention the new mill at Cripple Creek, Colo., a custom plant allowing a choice of flotation, cyaniding, or roasting and cyaniding. Flotation is a feature of many of the new plants and some existing mills have been remodeled to use flotation in place of amalgamation and cyaniding. The Utah Copper Co. has re- opened its Arthur mill and operations are being resumed in the big Ray, Chino, and Inspiration copper mills. Examples of new construction are the Mountain City 300-ton copper flotation mill in northern Elko County, Nevada; the Star zinc mill and one or two other mills in the Coeur d'Alene district of Idaho; and the 500-ton mill for the Buena Vista mine at Stewart, B. C. The last-named is to be installed underground, following the example of the zinc mill at Gilman, Colo., and he small Doyle jigging plant in the Wisconsin zinc fields.

Jan 1, 1937

By Roger L. Goin

Maintaining smooth haulage roads is a key to significant cost savings at Kennecott Copper Corp.'s Bing- ham Canyon copper mine, located near Salt Lake City, Utah. The truck operations section of the mine moves an estimated 300,000 tpd of waste plus some ore to maintain a balanced production cycle. A three-year truck replacement program has produced a dramatic new look in both size and capacity of the truck fleet. Currently there are 95 haulage trucks in the Bingham fleet with capacities up to 150 t. The trend towards the larger haulage units places greater importance on overall truck availability. The impact of a 150-t truck being out of service is far more critical than with the former 65 or 85-t units.

Jan 12, 1974

By Francis P. Sinn

IN the zinc smelting industry the year 1947 seems to have been one of putting one's house in order rather than one of any material technical development or radical change in operating conditions. Labor generally has been in better supply but several plants report a scarcity of skilled workmen. Some plants continue to operate on the basis of a six-day week and will probably continue to do so until labor is more plentiful. Only one plant is known to have operated on a curtailed basis because of labor shortage, but here the difficulty was lack of proper housing facilities. Necessary materials and equipment for much-needed maintenance and modernization have been in short supply so these programs have often been delayed. Laborsaving devices of the "Payloader" type have been more generally used for handling materials. Slab zinc production was discontinued during the last months of the year at Danville, 111. and at Langeloth, Pa. Both of these plants used the Hegeler type of furnaces fired with producer gas. It is understood that the rolling mill and possibly the acid plant at Danville will continue to operate. At Langeloth acid will be produced from

Jan 1, 1948

By W. H. Bassett

BERYLLIUM was discovered in 1798 by Vauquelin and the metal was first produced by Wohler in 1828 about a year later than his production of metallic aluminum. Beryllium remained dormant until about 1920 when the production of the metal by the electrolysis of a molten bath was carried out by Stock in Germany, closely followed by Dickinson in the United States and by Vivian in England. This may not have been the first time the electrolytic method was thus used but was the beginning of present-day methods. I believe the first commercial attempts in this country started with the Kemet Laboratories about 1924. Siemens & Halske in Germany were working on the same problem at about the same time. The work of the Kemet Laboratories was transferred to the Beryllium Company of America and later to the Beryllium Development Corporation. In 1926 1 made a considerable study of the beryllium¬copper alloys, using beryllium purchased from the Beryllium Company of America, and read a paper on this subject at the February, 1927, meeting of the A.I.M.E. However, I failed at that time to discover the properties of precipitation hardening which such alloys have in a very marked degree. After this publication the work on beryllium-copper alloys rested awhile. One cause for this was the difficulty of securing a supply of beryllium-at least at what might be considered a reasonable price. In 1926 the price was $200 per lb., a figure which held about the same both in this country and in Germany until the beginning of 1932, when it was offered here at $50 per lb. if taken in the form of a copper alloy which carried about 121/2 per cent beryllium. Somewhat later the 121/2 per cent alloy dropped to $25 per lb. of beryllium contained, which is the present price. Promise is made that with a greater consumption, production on a larger scale warrants a reduction in price to $10 per pound or less.

Jan 1, 1933

By GUY C. RIDDELL

ZINC, manganese, and aluminum received attention at the two nonferrous metallurgy sessions at the Annual Meeting. L.P. Davidson, general superintendent of the rebuilt Monsanto zinc plant, described its operation, which reflects Polish practice and is really a combination of electrolytic, Waelz, and retort procedure. Briefly, it embraces leaching of roasted concentrate with sulphuric acid, electrolysis of sulphate solution using Tainton lead-silver anodes with ?goulac? added to the electrolyte, treatment of tailing in Waelz kilns, and retorting of the recovered zinc oxide, casting furnace dross and residues. Recovery is good, equipment and maintenance costs low. Ferrate zinc that might be lost in the electrolytic process appears to be recovered as oxide in the Waelz treatment.

Jan 1, 1942

By AIME AIME

THE initial meeting on Mining Methods* opened at 10 o'clock Monday morning with Scott Turner as chairman and W. Spencer Hutchinson as vice- chairman; about 60 attending. After preliminary announcements Theodore Marvin was called on for his paper,, entitled "Rock Tunnel Methods," which has been appearing serially in The Explosives Engineer. Marvin read the introduction and called attention to the account of one or' two particularly' interesting projects, such as the. Brooklyn water supply tunnel. E. D. 'Gardner, Char1e.s S. Hurter, L. D. Lamont and Spencer P. Howell took part in the discussion, Howell commenting on the fact that, in one case cited, misfires had occurred through detonator wires 'coming in contact with the case of an unapproved flashlight, .,: and that all flashlights should be approved.

Jan 1, 1931

By Richard F. Link, George S. Koch

Advantages and disadvantages of deflecting (wedging) diamond-drill holes to obtain sampling data are compared with the alternative of drilling additional holes. The discussion is based on a statistical analysis of a large set of deflection data from exploratory boreholes in South African gold mines. Representative cost comparisons show the conditions under which deflections are likely to be desirable.

Jan 1, 1969

By AIME AIME

A SYMPOSIUM on current. conditions in Mexico, particularly in the oil and mining industries, was a most successful feature of the May meeting of the New York Section of the A.I.M.E. Heath Steele, vice-president of The American Metal Co.. Ltd., with an intimate knowledge of Mexico gave the principal address, and asked that his analysis of the present situation he regarded neither as an endorsement of Mexico's policy nor as the criticism of a disgruntled operator. To explain the .attitude of the great mass of the Mexican people towards recent developments, he first described briefly the political, social, and religious beliefs and customs of tile Mexican Indian. In spite of their contact with foreigners these beliefs and customs have remained unchanged throughout many generations. The old communal spirit and the idea of common ownership of the land still persist especially in the rural districts and villages; the old custom of a council for local self-government is reflected in the present-day labor committee. Mr. Steele discussed in order land oil, and mines.

Jan 1, 1938

By COREY C. BRAYTON

OUR first air travel began at Barranquilla on a trip to the platinum dredging-operations at Andagoya. The fare is based on a minimum weight of passenger, and I will have to admit that the minimum is too low. To make this trip by boat would have necessitated going back to the Canal, thence down to Buena Ventura, and up the San Juan river, which would have taken, counting delays, two or three weeks. The time by Scadta airplane was six hours. We stopped at Cartagena for a day to look over that historic city. The route from there lay along the north coast to the mouth of the Atrato river, then up this river, over the jungle, and over a divide some 300'ft. in elevation and down the San Juan river a few miles to Andagoya at the junction of the Condoto. The General

Jan 1, 1930

By William J. Coulter

WITHIN the past thirty years the United States has been involved in two tragic, vicious, and costly world wars. To make the world safe for democracy was the reason given for our participation, but the confusion and misunderstanding that prevails all over the world today suggests that war is not the proper approach to the attainment of that utopia. These conflicts were conceived and prosecuted by nations far advanced in civilization and culture. Their best manhood was sacrificed, a staggering tax burden was saddled on their peoples, huge financial losses were incurred, destruction of property was appalling, and cultural and peaceful scientific advancement received a setback that may require centuries to retrieve. Therefore, some basis is established for the conclusion that progress in the past fifty years has been most outstanding in the development of instruments used for death and destruction, and that progress in this direction between the two World Wars would indicate that the next war will go far toward total destruction of world civilization.

Jan 1, 1946

By COURTNEY DE KALB

IRON ore is the cause of the present trouble in Morocco. At least three nations are interested in the outcome and private syndicates have been active. The iron deposits are found in that mountainous northern coast line known as the Rif. This is an uplift that has been cut through, by the northward drainage, representing an ancient land surface. Erosion has produced .a fiordlike coast, which circum- stance has aided contraband' traffic to the tribes dominated by Abd-el-Krim, the chief of the clan of the Beni Urriaguel, near the center of 'the north coast, opposite Alhucemas. The iron deposits are extensive in the territory of the Beni Urriaguel. They were "located," if such a term is permissible, many years ago. The first arrangements, through direct contracts with the tribal chieftains, have been reinforced by compliance with the subsequent code under the Spanish protectorate in 1914. Under those terms, the location had to be made through the Arbitral Commission sitting in Paris. These locations, or "denouncements," were made by the I-louse of Mannesmann, of Hamburg.

Jan 1, 1925

By PROCEEDINGS OF MEETINGS

THE opening session of the Institute was held at Hazle Hall, Tuesday evening, October 27th, with a large attendance of members. President Raymond called the Institute to order, and after a few introductory remarks, introduced Mr. I. Lowthian Bell, President of the Iron and Steel Institute of Great Britain, and Honorary Member of the American Institute of Mining Engineers. Mr. Bell was received with great applause, and made his acknowledgments in a brief speech, of which the following is the substance: He desired to thank the Institute personally for the honor conferred upon him in his election to membership, and also for the invitation extended last year to the body of which he was President. The difficulty felt by many members of the Iron and Steel Institute, of leaving for a long journey the works of which they had charge, aggravated by special industrial troubles at the time of the invitation, had obliged them to conclude that it could not then be accepted in a fitting manner. The iron manufacture of this country is a subject of great interest to Englishmen, who look with pride upon the achievements on this side the water of the descendants of a common ancestry. His own reception in this country had far surpassed in cordiality even the well-grounded anticipations he had formed from the assurances of the President and other friends. Notwithstanding the flattering manner in which his friend, in introducing him to the Institute, had spoken of his contributions to the science of iron metallurgy, he could not take to himself alone the significance of this welcome. He knew it was a recognition of the services rendered by the body which he had the honor to represent; and he was glad to see present a member of that body, Mr. Thomas Whitwell, who had fortunately been able to make the journey at this time, and whom he had had the pleasure of meeting on the shores of Lake Champlain. He had been requested to say something of his impressions of the American iron industry. It was not easy to digest so soon the vast

Jan 1, 1875

By P. H. Mell

THE little village, from which this formation receives its name, is situated on a bluff of the Alabama River, 175 feet above water level. This bluff is a portion of high table land that begins in the western portion of Choctaw and extends through Clarke and Monroe counties. We find points on this ridge more than 100 feet higher than Tuscaloosa, and nearly as high as the Tennessee River at Tuscumbia. Through this the Alabama River cuts its way, exposing a beautiful cross-section of the strata, of which the accompanying sketch may give some idea. The fossils are found about 75 feet below the surface and 100 feet above the level of the river. There are seven distinct strata. 1. The lowest, extending from the water's edge up the bluff 80 feet, is a soft calcareous rock containing about 15 per cent. of carbonate of lime, with occasional specks of mica. In this a few Ostrea, Turritellce, and Flustrce were found, but so friable as to fall to pieces when handled. 2. Next comes a stratum varying from 2 to 8 feet, consisting of

Jan 1, 1880

By J. George Gregr

INTRODUCTION This part contains field case studies of typical mishaps, accidents, equipment damage or post installation failures resulting from mistakes in design, manufacturing and construction, as well as improper storage, handling and installation procedures of the equipment covered in Part 1. GENERAL Certain mistakes are repeated and common rules violated on almost all industrial equipment installations, with the inevitable consequences of additional cost, construction delays and aggravation of all parties involved. The most common failures are in the following areas: Cleanliness of all components during installation and later in operation. Adherance to manufacturer' s recommendations and tolerances for equipment installation. Comprehensive, properly identified installation and maintenance records. Handling of the components. Adequate tooling and auxiliary equipment in working order. An inoperable hydraulic power unit for torque wrench or for jacking of the mill, or faulty crane can be a very costly proposition. A special area in comminution circuits are wear components. Apart from the mill liners, the wear components such as, feed chutes, rock boxes, mill trunnion liners, discharge sumps, etc. are designed to the best theoretical configuration, based on experiences in similar installations. However, each process is different to a various degree, mainly because of various types of ores and grinding requirements. Consequently the first generation of wear components is very seldom the ideal one. Based on operational experience, the shape and material of wear components should be modified, until the optimum, most economical design is achieved. SHIPPING AND STORAGE Considerable damage to the equipment can be done by careless packing, shipping or storage.

Jan 1, 1982

By Strathmore R. B. Cooke, Paul B. Queneau

The kinetics of the dissolution of scheelite in basic solutions of carbonate and fluoride were investigated. Work was also done with solutions of alkali metal chloride, hydroxide, phosphate, and mixtures of phosphate and fluoride. The study was conducted at 90 psig and at temperatures ranging from 100" to 155"C, and both natural and synthetic scheelite single crystals were used. The interaction of scheelite with carbonate solutions generally followed a parabolic rate law, and resulted in the formation of calcite crystals on the attached surface. The transport of the CO3 through the calcite to the scheelite surface was probably rate -controlling between 115" and 135°C. Positive deviations from Parabolic behavior were observed at 100" and 155?C, presumably due to the calcite grain growth, and to the formation of a noncoherent calcite layer, respectively. The leaching of scheelite with alkaline fluoride solution produced a calcium fluoride reaction-product which covered the surface as a sheet-like layer. Below 110°C the dissolution rate was parabolic; at 115" and 135°C it was linear. In the linear region, the periphery of the calcium fluoride layer lifted from the sample. Only the lower layers, braced by the scheelite substratum, remained unbroken. This bound layer, approximately constant in thickness, limited the rate at which the fluoride could attack the scheelite. The phosphate and phosphate-fluoride leaches dissolved scheelite at a linear rate; solid reaction products were respectively hydroxyapatite and fluorapatite. Sodium hydroxide and chloride were not effective leachants, and did not produce observable solid reaction products. THE feasibility of pressure leaching of scheelite pulps with basic solutions containing either carbonate or fluoride ions, as indicated by the following equations, has been established by previous investigators:1-3 200°C CaWO4s + CO37q - CaCO3s+WO4aq [1] 200°C CaWO4s + 2Faq ^ CaF2s+WO4aq [2] It is to be noted that a commercial process employing reaction [I] is in use at Union Carbide's operation near Bishop, Calif. In the earlier work referred to, it was apparent that the precipitation of the solid reaction-product on the scheelite particles sharply reduced contact of the leachant with the scheelite. We have extended this work by studying the kinetics of dissolution employing single crystals of scheelite of known exposed surface area. In addition, the effectiveness of solutions of phosphate, of phosphate with fluoride, and of chloride and hydroxide as leachants for scheelite have been investigated. EXPERIMENTAL Apparatus. The low-pressure autoclave used in this wo (100 psig maximum) is essentially that of J. Halpern4 as modified by F. A. Forward.5 Constructed entirely of 316 stainless steel, its maximum capacity is 4000 ml. The temperature in the autoclave was regulated to *0.5?C by a Wheelco thermocouple controller. A 4-in. diam, three-bladed impeller, circulated solution upward against the sample, and a strobo-scope permitted holding the stirring rate to *15 rpm. A check valve and a "pop" type safety valve were installed, a sample holder was fixed to an externally adjustable rod, and a water-cooled condenser was placed in series with the sampling valve. The stainless steel sample holder, Fig. 1, held the epoxy-mounted sample (f) five mm above the impeller. Tightening the tapered sleeve (d) positioned the epoxy-resin specimen-mount by forcing it back against the spacer (c). The mount (e) was 1 in. diam. Sample Description and Preparation. Both synthetic and natural scheelite crystals were leached. The former were single crystals of 99.95 pct purity which were leached approximately perpendicular to the "c" axis; they were supplied by the Gallard-Schlesinger Chemical Manufacturing Corp. The natural crystals, supplied by Minerals Unlimited, were transparent, analyzed 99.8 pct CaWO4, and in ultraviolet illumination exhibited the characteristic blue glow of substantially molybdenum-free scheelite. To permit exposure of an essentially constant surface area of scheelite to the leachant, the samples were mounted in Scotchcast Brand Resin No. 250 (Minnesota Mining and Manufacturing Co.). The mount-

Jan 1, 1970

By Marshall Pease, R. J. Brandon

A UTILITY that has a large consumption of coal must insure an adequate and sound supply of fuel. The Detroit Edison Co., which has an annual coal consumption of about four million tons and spends approximately $32 million a year for coal, including freight charges, has developed a program for fuel procurement and for evaluation and selection of fuel for reliable and efficient plant operation. Fuel Procurement Coal Purchasing Division: The Fuel Supply Div. of the Purchasing Dept. combines all of the procurement functions in one group, which must maintain adequate stocks of fuel. In addition to its usual purchasing duties, the division also governs transportation, follow-up, invoice and freight bill, in cooperation with the Accounting Dept. The Fuel Div. is comprised of the fuel agent, an assistant fuel agent, a coal buyer and five coal clerks, who follow the movement of each car, initially approve freight bills and invoices, and file claims whenever there is a shortage of one ton or more. The fuel agent reports directly to the purchasing agent of the Company, and all major programs are planned jointly with the chief purchasing officer. The apparent individuality of the fuel section is necessary because of the tremendous volume of coal cars handled each day, sometimes as many as 500, which must be handled promptly to complete the fastest possible move from the mines to the plants. Determining Annual Coal Volume: Through the combined studies of a Production Dept. Load Committee and the Controller's office, accurate predictions of coal requirements for any given year are provided the Fuel Dept. from 12 to 15 months in advance. This is divided into the requirements of all individual power plants and central heating plants. This in turn determines the quantity and quality for plants whose specific fuels vary with the type of equipment installed. In the Detroit area, which has a high industrial load, early estimates of annual coal consumption usually are resolved at the end of the year within 4 or 5 pct of the original plan. Operating in a highly developed industrial area eases the task of estimating primary output; and, with the residential demands increasing in a steady and fairly well-defined pattern, the overall coal schedules are not subject to radical changes during any given year. Selecting Suppliers: At any time, but especially during or before an emergency, the coal supply factor must be made secure. This is particularly true in the procurement of utility fuel. There are always extreme quantities of so-called "bargain" coal available during the buyers' markets, such as recently prevailed. These opportunistic offerings may be considered a means of averaging down overall price, rather than as a steady and dependable supply source. Coal is purchased on contract from mine operators and sales agents who have proved reliable. They are not opportunists who desert for higher dollars in times of duress; they do not fail to fulfill contracts when markets rise or overship when markets dip. The progressive operator today who is willing to expend capital to improve quality and service deserves much more consideration than a matching of short-term pennies. When a company has a high volume of annual needs, all phases of the mine supply must be considered. The mine must be able to produce the quality required at a fair price and be able to sell oversizes of coal in enough volume to screen sufficient nut and slack. It must crush coal and sell mine run at prices in line with competitive nut and slack and be willing to do so when there is no demand for prepared sizes. Determining Price: The public utility is in direct competition with any of its customers who can, if savings are guaranteed, generate their own power. Today, to a greater extent than ever before, private industry must do a better overall job than Government-controlled operations. The price of coal must be realistically balanced with the price paid by almost all industries and the railroads as well. The supply-demand ratio in coal is not difficult to discern. There is access at all times to Govern-

Jan 1, 1952

By Hsun Hu, R. S. Cline

The formation of annealing textures during the course of recrystallization in 2 pct Al-Fe crystals rolled in the (111) [112], (112) [111], and (112) [Till orientations has hem studied in detail. When the rolling texture is composed of both (111) [121] and (001)[110] components, the annealing texture consists of mainly (110) [001] and (113) [332] components. As the (001) [110] component diminishes from the surface to the interior of the rolled crystal, the relative concentration of the (113) [332] component in the annealing texture decreases accordingly, whereas that of the (110)[001] component increases with the (111)[112] component in the rolling texture. Such dependence of the annealing texture on the composition of the rolling texture is in accmdance with the oriented growth mechanism. Grain-growth characteristics during recrystallization, hence the annealing texture, can he considerablv different in (112) [111]-type crystals depending sensitively on the initial orientation of the crystal. In a previous publication,' the formation of rolling textures in 2 pct A1-Fe single crystals with initial orientations of approximately (1ll)[112], (112)[111], and (112)[111] was studied in detail. The deformation texture of these crystals consisted of either a single (111)[112] or a combination of (111)[112] and (001)[110] components in various concentrations. For the (lll)[112] crystal, the deformation texture was a single (lll)[112] up to 70 pct rolling reduction, but it became (lll)[112] plus (001)[110] after -90 pct reduction. For the (112)[113.]-type crystals, the relative concentration of the (111)[ 112] and (001)[110] components varied with the depth below the surface of the crystal, as well as with the amount of deformation. These series of specimens, having deformation textures with a range of concentration of the (111)[112] and (001)[110] components, could therefore be used for a thorough investigation of the effect of deformation-texture components on the formation of annealing textures. In a study of rolling and annealing textures in Si-Fe crystals, Dunn and Koh3 noted that the addition of a (001)[110] component to the (111)[112]-type deformation texture had practically no effect on the recrystallization texture.* According to the ori- ented growth mechanism for the formation of annealing textures, nuclei related to the deformation texture by approximately 30-deg rotation around a common [110] axis have the highest rate of growth and the resulting annealing textures generally have such an orientation relationship with respect to the deformation textures.314 It was reasoned by Dunn and Koh3 that if the oriented growth mechanism operated the recrystallization texture developed from a deformation texture containing both (111)[112] and (001)[110] components should be strongly centered around (113)[332], because (113)[332] is approximately midway between the (111)[112] and (001)[110], and is related to both of these two orientations by [110] rotations of 25 to 30 deg. Hence, nuclei of (113)[332] orientation should have a high rate of growth in the deformed matrix. However, their results were not in accord with this prediction. It was felt by the writers that a detailed study was needed to clarify the effect of deformation-texture components on annealing-texture formation. For this reason, the present investigation was conducted. EXPERIMENTAL PROCEDURE Specimens used for the present investigation were taken from the crystals rolled previously for deformation-texture studies.' In order to follow the progress of annealing-texture formation during the course of recrystallization, a single specimen was taken from each rolled crystal and its textural changes examined after successive anneals until recrystallization was complete. The specimen was carefully cut from the rolled strip with a jeweler's saw. Prior to annealing, the sawed edges were etched to remove distorted metal, while both faces of the specimen were protected from the etching solution by acid-proof plastic tape. After annealing, the specimen was etched from the "bottom" face only (the reference or "top" face of the specimen was protected by plastic tape) to one half of its original thickness, so that the texture at the surface and at the central section of the strip could be determined by the reflection technique. The

Jan 1, 1965

By P. Somasundaran, D. W. Fuerstenau

The length of the collector is found to influence the flotation of the mineral even at incipient conditions, which are below the concentration at which interaction at the solid-liquid interface begins to take place to form hemi-micelles. To study this dependence, concentration for incipient flotation of quartz was determined as a function of pH with collectors of various chain lengths. The observed effect of chain length on flotation is ascribed to that of collector adsorbed on the bubble surface. In previous studies, it was shown that at low concentrations the alkyl collector ions adsorb at the solid-liquid interface as individuals.''2 At higher concentrations, the collector ions adsorbed at the solid-liquid interface associate with each other to form two-dimensional aggregates called hemi-micelles. Above the hemi-micelle concentration, the length of the hydrocarbon chain is extremely important since the hydrocarbons are in effect removed from water during the association, making the energetic conditions more favorable for adsorption at the interface. Because of this enhanced adsorption, one observes a very rapid increase in flotation associated with the hemi-micelle formation at the solid-liquid interface. However, a dependence of flotation on the chain length at concentrations below that required for hemi-micelle association was also observed,' and this cannot be explained by the above mechanism which postulated hydrocarbon chain interactions only at the solid-liquid interface. This prompted an investigation into other possible reactions of the hydrocarbon chains and an examination of the conditions at the bubble surface involved in the flotation system and how these observations might explain the reactions at the solid-gas interface which cause the particle-bubble attachment required for flotation. To obtain more information on chain length effects, flotation, under incipient conditions, was tested by vacuum flotation techniques. The collector-concen-tration-pH relationships for flotation of quartz with alkyl ammonium acetate collectors was delineated by observing the pH at which quartz particles begin to float to the liquid surface. By investigating flotation as a function of pH, it was also possible to study the effect of neutral molecules on incipient flotation conditions, since the aminium ions hydrolyze to amine molecules at higher pH values. EXPERIMENTAL WORK Brazilian quartz specimens were crushed and sized, and the 270 x 400 mesh fraction was used for flotation studies. The samples were leached with concentrated hydrochloric acid until no coloration of the acid occurred. The leached material was washed free of chloride ions and stored in distilled water. The vacuum flotation technique developed by Schuhmann and prakash3 was used to determine the critical pH-concentration curves. This method, which can be used to delineate conditions for incipient flotation, is fairly simple and rapid. About 0.5 gm of 270 x 400 mesh quartz was placed in a 100 ml graduated cylinder which was then filled to the 100 ml mark with the collector solution made from high-purity alkyl ammonium acetate salts. The water used for the test was conductivity water saturated with air that had been passed through a cleansing train consisting of Drierite, Ascarite, a water wash bottle, and a trap. After the pH was adjusted, the cylinder was then conditioned for thirty minutes. In the tests where an acid pH was desired, sufficient acid was added before the collector solution to avoid any effect due to slow desorption of collector from the quartz surface. After conditioning, vacuum was applied to the system and the flotation or nonflotation of the quartz was noted. The pH at which the quartz particles began to float to the liquid-gas interface was taken as the critical PH. Critical pH curves were thus determined for different concentrations of the various collectors. Hallimond tube flotation data were taken from the authors' previous publication1 for correlation with that from the vacuum flotation. RESULTS AND DISCUSSION The results of vacuum flotation studies for determining critical pH-concentration curves, i.e., curves which delineate conditions for incipient flotation, are shown in Fig. I. In generaI, all the curves exhibit an upper and lower pH limit between which flotation will

Jan 1, 1969

By R. A. Greenkorn

This project originated in a practical problem—we needed five tracers that could be used together to locate flow paths in a pilot flood. While tracers for subsurface liquids have been used since the turn of the century,1-15 none of those reported in the literature appeared to be either consistent or quantitative enough for our purposes. Most were used in field systems without controlled experiments to determine the accuracy and precision of analysis, and many were tracers that could not be used collectively. The ideal tracer, of course, would follow the fiuid of interest exactly, traveling at the same velocity as the fluid front. But the ideal is impractical to attain because adsorption-desorption effects cause the tracer to lag behind the front; these effects, plus diffusion-dispersion effects, cause the tracer front to spread more than the fluid front. Thus, our objective was not to locate a tracer that would be ideal for all circumstances but rather, to find one that would approximately follow the fluid, or one that under controlled conditions could be corrected to calculate the movement of the fluid front. We considered tracers satisfactory—(1) if they were easy to analyze; (2) if their breakthrough-elution curves were not too different from those for the chloride ion, a tracer believed to follow the fluid front closely; and (3) if we could calculate from the curves a material balance, at 1.25-PV (pore volume) injected, within 5 per cent of that calculated from chloride curves. Of a possible 35 materials, we selected 13 tracers that could be quickly and easily identified and whose analysis was claimed to be accurate within 5 per cent. Only one of these, tritiated water, was a radioactive tracer. Radioactive tracers are easy to detect even in small quantities, but they require special handling and special equipment. Also, those that can be used together are limited because special equipment is required to separate emissions from the various tracers. Two of the original 13 tracers were eliminated in static tests to determine how accurately and precisely they could be analyzed, and to check on gross adsorption. The remaining 11 were flowed through a 9-ft linear sandstone model, and breakthrough-elution curves were obtained. Finally, three tracers were field-tested as breakthrough tracers. These tests are described in the following sections. The 13 tracers considered in these experiments were EDTA (ethylene diamine tetra acetic acid), fluo-rescein, picric acid, salicylic acid and ammonium, boron (as borate), bromide, dichromate, iodide, nitrate and thiocyanate ions, plus chloride ion and tritiated water. All but the chloride ion and tritiated water were subjected to static sand tests to eliminate the tracers that could not be analyzed quickly and accurately and to eliminate those that showed excessive adsorption. All but two of the tracers, EDTA and salicylic acid, qualified for flow tests on this basis. The procedures used in the static tests (see Appendix A for analytical details) were as follows. Each tracer (in the amount shown in Table 1) was dissolved in 1,000 ml of water. Then, 800 ml of this solution was added to 500 gm of sand, and the remaining 200 ml was reserved as a control standard. The sand-tracer mixture was agitated once a day over a 10-week period, and during this period we analyzed five duplicate samples from this mixture, along with five duplicate samples from the control solution. From the control-sample analyses, we constructed a control chart on which the sand-tracer analysis results were plotted. The control chart, and its use to determine accuracy and precision of analytical results, as well as the amount of adsorption, is described in Appendix B. The results of the static tests are summarized in Table 1, which lists the concentration c (concentration at time t) divided by c, (initial concentration). If there was no adsorption, c/c, = 1. The acceptable deviation from this value varied from tracer to tracer, depending upon the limits of analytical precision established for the different tracers. The best results were obtained with boron, bromide and dichromate, with all values falling within limits of accuracy and precision. Ammonium, iodide, nitrate and picric acid also were satisfactory, although the ammonium results were erratic. Flourescein and thiocyanate were unsatisfactory ini-