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By C. Y. Garber

Interest in the sink-float plant operated by the Bunker Hill and Sullivan Mining and Concentrating Co. at Kellogg, Idaho, has recently been largely confined to the preparation and reconditioning of the galena medium. The ease and simplicity of these operations in a concentrating mill producing a flotation lead concentrate has occasioned enough comment to possibly justify a brief description. The subject is treated from an operator's viewpoint only; no effort is made to discuss it in a theoretical or technical manner. Plant at Bunker Hill The sink-float plant was first operated in December 1941. It was built for the purpose of quickly increasing mill capacity with a minimum of equipment. It is the Huntington-Heberlein sink and float process using galena medium and is operated under license from the Sink and Float Corporation, New York city. Lead-zinc ore from the Bunker Hill mine is crushed to pass a 1¼ in, screen and is then washed and separated on vibrating screens having 4½-mm. round-hole punched plates. The screen under-size, amounting to 33 per cent of the mill feed, is dewatered and sent to the ball-mill feed bins. The screen oversize goes to the sink-float plant, where 50 per cent of the oversize, or 33 per cent of the mill feed, is float, which is washed free of medium and disposed of as a tailing. The remaining 33 per cent is sink, which, after washing, is crushed to pass 36 in. and joins the under-size in the ball-mill feed bins. The normal plant capacity is 1700 tons per 24 hr. About 1.7 per cent of the total lead and 3.3 per cent of the total zinc in the feed is lost with the sink-float tailings (Table I). More complete descriptions of the H. H. process and Bunker Hill sink-float plant are given in several recent articles, listed at the end of the paper. Preparation OF Medium at Bunker Hill New medium is made intermittently as needed, usually 12 hr. in each 6 days. A small portion of the current mill flotation concentrate is diverted from the lead cleaner cells to a I-in. vertical sand pump and pumped to a two-cell 36-in. Agitair flotation machine, where NaCn and ZnSO4 are added and the grade of concentrate is improved as shown in Table 2. Tailing from this operation is returned by gravity

Jan 1, 1947

AT the meeting of the Board of Directors in March 1945, plans were discussed for a special General Meeting to commemorate, in an appropriate way, the founding of the Institute at Wilkes-Barre, Pennsylvania, in 1871. It was decided that seventy-five years of growth, progress, and achievement; of service to the profession, to the mineral industry in all its branches, and to society at large should be fittingly celebrated. Harvey S. Mudd, then President of the Institute, was authorized to appoint a General Committee on Arrangements as well as necessary working committees. On June 6, 1946, Louis S. Cates, as President, at a special meeting of the Pennsylvania-Anthracite Section at Wilkes-Barre, officially announced plans or a three-day meeting to be held at The Waldorf-Astoria, in New York City, September 16-18, 1946. Four major sessions to be addressed by eminent speakers had been-planned in some detail to constitute a "World Conference on Mineral Resources." The U. S. Department of State had dispatched a 1500-word airgram to all its diplomatic posts giving worldwide publicity to the scope and importance of the meeting; and formal invitations had been issued to more than 150 institutions in 40 foreign countries to send official delegates. These included scientific and engineering societies, educational institutions, and sundry government agencies connected with the mineral industry. However, about a month later it was found necessary to postpone the celebration. The reason was an unforeseen expansion in the requirements of the United Nations for hotel living space in New York to accommodate delegates to the meeting scheduled to start September 3; and, of course, U.N. delegates would be given priority. It was decided to postpone the Celebration-conference to the week beginning March 17, 1947; t6 devote the first three days primarily to the Celebration; and to follow it with the technical sessions, committee meetings, and other functions, that are regular features of the Annual Meeting. To accommodate the combined "show" it would be necessary to hold some of the Annual Meeting sessions at another hotel;

Jan 1, 1947

By E. V. Potter, H. C. Lukens

The volume of hydrogen released from electrolytic manganese at various temperatures and pressures was determined in a previous investigation1 as part of a study to determine the most practical procedure for removing the hydrogen from electrolytic manganese metal. No attempt was made to determine the absolute volume of gas in the metal at any temperature and pressure; the volume of gas released showed only the variation in solubility with temperature and pressure. The results were very similar to those obtained by Sieverts and Moritz.² Both sets of data show a minimum solubility between 500' and 700°C., but they differ in certain respects; on cooling from 500°C., our results showed an increase in solubility of about 7 C.C. as compared with an increase of 34 C.C. per 100 grams shown by Sieverts. Furthermore, the transition temperatures, as indicated by sharp breaks in the solubility curves, did not agree well with Sieverts' data. This information was of secondary importance in the earlier investigations, and the solubility at low temperatures and the transition temperatures were subject to considerable error. Therefore, a subsequent investigation, reported in this paper, was made to measure the absolute solubility at temperatures from room temperature through the melting point and make more accurate observations of the transition temperatures. Apparatus and Method The apparatus and method were essentially the same as those described in the previous work,' as shown in Fig. I. At high temperatures, the small tube containing the thermocouple in the sample container A frequently broke off, so for some of this work the thermocouple was placed outside the sample container and protected by a quartz tube of about the same wall thickness as the sample container. No significant difference was found in the transition temperatures obtained in the two ways. The automatic temperature controller was used in these tests in the regions where there was little change in solubility with temperature. In the neighborhood of the transition points a continuously variable autotransformer was used instead of the automatic controller, and the power input to the furnace was adjusted so that the temperature increased or decreased at a very slow, uniform rate through the transition range. This procedure was followed because the temperature oscillations produced by the controller were too great compared with the transition range, and the transi- . tion points determined under such conditions were less accurate. Absolute Solubility Procedure ad Results The absolute solubility of hydrogen in manganese could be determined most

Jan 1, 1947

By Gustav S. Preller, A. M. Gaudin

For the past 20 years it has been generally accepted that the flotation process is made possible as a result of the action of certain chemical substances on the surface of the mineral particles. In fact, it has been suspected, but never demonstrated, that this action produces on the mineral particles a layer of chemosorbed ions that is of the order of magnitude of a monolayer; that is, of a layer one ion deep. It is the purpose of this paper to present certain initial results on the relationship of mineral surface area and collecting-agent requirements. Up to about eight years ago, all considerations involving the surface area of finely divided solids were limited by the fact that there was not in existence any general method for determining the extent of such surfaces, especially on mixed materials. However, the method invented by Brunauer, Emmett and Teller1 has changed the situation by providing a general procedure (BET method). This procedure has already been applied to mineral dressing problems2-4 and has now received confirmation as to accuracy by an entirely independent method.' This confirmatory or "absolute" method uses a very tedious calorimetric procedure and is not suitable for routine determinations; but still another method6 now is available to relate the results obtained by the BET method to those obtained calorimetrically. This Harkins-Jura method has the advantage that it does not require an assumption concerning the parking area per molecule of adsorbate (nitrogen). In the original work by Brunauer, Emmett and Teller the parking area per nitrogen molecule was calculated to be either 13.8?2 or 16.2?2. according as the nitrogen was assumed to be closely packed as in crystalline nitrogen or loosely packed as in liquid nitrogen. The initial experimental work from this laboratory2 supported the 13.8?2. figure; that work was done on glass spheres of measurable geometric area and it was based on the assumption that the glass spheres were truly smooth; any deviation from this assumption would, of course, have made the calculated parking area higher. Harkins and Jura's results suggest that the parking area is not the same for all substrata; furthermore, the average of the 87 measurements cited indicates a "preferred" parking area for the nitrogen molecule of about 15.2?2., with extreme values at 13.7 and 16.9?2. The average of 21 determinations made in connection with this study7 gave a parking area of 14.3 ± 0.27?². In view of this result and of the Harkins and Jura

Jan 1, 1947

By John R. Lewis

DURING the past few years there has been considerable interest in the sizing and the preparation of the iron ore fed into blast furnaces. Furnacemen know that proper sizing of ore tends to increase the efficiency of the furnace. It has been shown by Joseph1 and his associates that there is a direct relationship between the porosity of an ore particle and the time required for its reduction in the blast furnace. This relationship may be stated as follows: All other factors remaining constant, the time for reduction of a given sample of ore is inversely proportional to its porosity. As a consequence, large pieces of very porous ore, say 3 or 4 in. in cross section, will be completely reduced by the time they reach the hot zone just above the tuyeres, while large pieces of dense, nonporous ore may reach the hot zone with their centers unreduced. This means that for the latter complete reduction will be accomplished by the so-called "direct method;" i.e., where carbon reacts directly with the ore. Some recent work by Philbrook2 seems to contradict this rule. He found that of two unlike ores he studied, the one with the lower porosity reduced more readily. He explained his results as "possibly due to an apparently greater tendency of the `A' ore (lower porosity) to crack during preliminary dehydration and during reduction." This brings his results in line with the rule stated above. It is not the author's intention to enter into a discussion of the merits of "direct" versus "indirect" reduction. It is enough to say that, in general, indirect reduction is desirable. For the greatest efficiency, Gruner's theorem3 requires that all reduction in the blast furnace be indirect. Joseph seems to believe this also, because in his recent article on Some Comparisons between Iron Ore, Sinter and Nodules as Blast Furnace Feed' he concludes that: "In general, the carbon in blast-furnace coke is used most efficiently when the largest amount of the carbon charged reaches the tuyeres." However, P. V. Martin,' in an excellent paper, has shown that some direct reduction may actually increase the efficiency of the furnace; that is, increase its rate of production while maintaining maximum fuel economy. For nonporous ores there is more opportunity to have an excess of direct reduction unless the factors that make for indirect reduction are favored; for instance; the proper sizing of the ore particles. Another factor that has an important bearing on the reduction rate, as it is affected by particle size, is the flow of heat into the particle. The ore particle

Jan 1, 1947

By Lloyd R. Jackson

In the past 15 years there has been a great deal of interest in the fundamentals of plastic flow and rupture in metals and a number of papers have presented substantial advances toward a fundamental insight into the mechanism of these two processes. This paper is an appraisal of the present position with respect to the following: 1. The relative importance of shear and hydrostatic stresses in controlling the plastic flow of metals. 2. The relative importance of shear and hydrostatic stresses in determining the amount of flow before rupture in metals. 3. The use of generalized strains in determining the effect of plastic flow on the work-hardening of metals. FundamentalS Involved in Plastic Flow In attempting to devise a quantitative description of plastic flow in metals, it has been customary to assume that metals are homogeneous and isotropic. The fact that neither of these assumptions is correct complicates the experimental appraisal of relations developed. Nevertheless, as will be shown, metals are close enough '0 being isotropic and homogeneous so that considerable insight into the mechanism of plastic flow can be obtained. The assumptions of isotropy and homogeneity allow both the elastic and plastic behavior of metals to be described in terms of 12 variables—six being stress variables, and six being strain variables. From this viewpoint, it should be possible to represent the stress-strain relations in the plastic range for metals by a surface in 12 dimensions. One boundary of this surface would be the surface of transition from elastic to plastic behavior; the other would be the surface of rupture. These two surfaces would be joined by the surface of plastic flow. The shape of this composite surface would depend on the test temperature and speed of straining This paper is concerned only with results obtained at constant temperature and constant speed of straining. While such a representation is conceivable, the demonstration of such a surface would present almost insurmountable obstacles. The most fruitful simplification of this concept has been the recognition that the behavior of metals in the plastic region is primarily a result of shear stresses and strains. Based on this viewpoint, it is possible to utilize stress and strain invariants that are independent of hydrostatic components to define an effective stress and strain. In effect, this amounts to reducing the task of representing stresses and strains in 12 dimensions to one of representation in two dimensions. The two invariants (one for stresses and one for strains) that have received most attention are the following: q2 = ½[(Txx= - Tyy)2 + (Tyy - Tzz)2 + (Tzz - Txx)2 + 3(Txy2 + Tyz2 + 7xx2) [1]

Jan 1, 1947

By E. H. Crabtree, Neil S. Parker

THE custom milling plant of the Eagle-Picher Mining and Smelting Co. is at Sahuarita, Arizona, approximately 20 miles south of Tucson. It is connected by a 2-mile railroad spur to the main line of the Southern Pacific Railroad between Tucson and Nogales. The capacity of the plant is 500 tons per day. The mill is conventional except perhaps in the rather wide variety of ores treated. These vary from straight copper ores, from which only one concentrate is produced, and lead-zinc or copper-zinc ores from which two concentrates are produced, to complex gold-silver-copper-lead-zinc ores, which require the simultaneous production of three or four concentrates. Custom ores are received in lots varying in size from a few truckloads to several carloads. Similar ores, after crushing and sampling, may be commingled, or individual lots may be milled individually. The ores are first dumped either into one of two 200-ton railroad bins, or into one of the two 75-ton truck bins. From these bins the lot of ore is individually crushed in a 24 by 16-in. jaw crusher to 3-in. size, and then to 1/2-in. size in a 3-ft Symons shorthead crusher. After crushing to 1/2-in., the ore is conveyed to the automatic sampling plant. This consists of three Vezin samplers in series, each successively cutting out 10 pct, to pct and 5 pct of its feed. After No. 1 sampler, the material passes through a mixing barrel and is then crushed to 1/4-in. in a set of rolls before passing to No. 2 sampler. Between No. 2 and No. 3 samplers, the ore is again mixed in a mixing barrel. The final sample, consisting of one pound per ton of ore, is taken to the laboratory, where it is further crushed to 1/8-in. in a coffeemill, and then riffled down to the size required for grinding in a pulverizer. The capacity of the crushing and sampling plant is up to too tons per hour, depending upon the character of the ore. After sampling, the ore is stored in five ore-storage bins, consisting of four 200-ton bins and one 175-ton bin. Each of these bins is discharged by means of belt feeders and conveyor to the ball mills, so that ores may be composited for milling in any required ratio, or milled separately by themselves. Fine grinding is done in one 6 by 4-ft Allis-Chalmers ball mill and one 8-ft by 36-in. Hardinge mill. These two mills both discharge to one 54-in. Akins Simplex Highweir classifier. The classifier sands can be returned to either or both mills, so that flexibility in grinding for different ores is easily obtained. Flotation equipment consists of four 66-in. Fagergren machines for copper-lead roughing and six similar machines for zinc roughing. Lead-copper bulk concentrate is cleaned and recleaned in eight No. 18-S Denver machines, and zinc concentrate is cleaned in three 66-in. Fagergrens. Copper-lead differential separation

Jan 1, 1947

By Tell Ertl, Ernest E. Burgh

INTRODUCTION THE Bureau of Mines is operating an oil-shale mine 10 miles west of Rifle, Colo., as part of its Synthetic Liquid Fuels program. The purpose of operating this mine is twofold: First, to supply oil shale to an experimental processing plant; and second, to develop practices and select methods for mining oil shale on a commercial scale at the lowest practicable cost. The second purpose-that of finding out how to mine oil shale most cheaply-entails considerable mining research. Since the drilling of oil shale probably will be one of the major items of the mining cost, factors that influence drilling speeds were investigated. One phase of the drilling program was the development of a successful hard-surfaced rock-drill bit1 that can be used for drilling long holes in oil shale without changing bits. During that phase, drilling speeds were measured and drill cuttings were collected for assay and for screen sizing. When the cuttings from the individual tests were compared, a definite relationship was shown to exist between the drilling speed and the coarseness of the drill cuttings. PROCEDURE Measurement of Drilling Speeds All drilling in the tests was done with a Model UMB-D-99W Gardner-Denver wagon drill. Round-lugged drill steel, 1 ¼ in. in diameter was used in 6, 12, and 18 ft lengths with 2 1/8 -in. Timken H-type bits hard-faced with acetylene tube borium. The tests were made in the lower adit of the Bureau of Mines oil-shale mine; the grade of the oil shale drilled ranged from 18.6 to 42.7 gal per ton. During the experiments air pressure varied between 75 and 90 psi while water pressure remained fairly constant at 75 psi. All holes were drilled almost horizontally. Each drill hole was thoroughly cleaned of cuttings after being collared. The advance of the drill along the carriage was measured and recorded as the drilling speed in inches per minute. Method of Collecting Cuttings To facilitate the collection of cuttings, each drill hole was collared in a smooth, vertical portion of the oil-shale breast (Fig 1). A galvanized-steel sheet was fastened to the breast below the area in which the hole was to be drilled. The cuttings washed out of the drill hole by the drilling water were guided by the steel sheet into a wooden box. The cuttings that remained in the drill hole after the drill was withdrawn were scraped out and placed in the same box as the cuttings washed out of the hole. After the cuttings from a 1-min. drilling interval were collected, they were placed in flat metal pans. The fines were allowed to settle and the clear water was decanted. The cuttings then were dried in the sun.

Jan 1, 1947

By C. Ernest Birchenall

AS a basis for further progress in several branches of metallurgy, particularly the study of physical properties of solid solutions and the kinetics of solid-solid reactions, a more complete understanding of the structure of solid solutions and the nature of the metallic bond is- necessary. Any investigation contributing to this understanding should be of primary interest to the metallurgist. Since the metallic bond is characteristic of an assemblage of atoms, it can be studied only where this assemblage exists. One of the most promising approaches to this study of the interactions in metals is through the general problem of binary metallic solutions. Although crystal structures of many solid metallic solutions have been determined and solubility limits for many systems are given in phase diagram studies, progress beyond this is irregular. Electromotive force and vapor pressure determinations have provided thermodynamic activity data for small concentration and temperature ranges in the amalgams and a few other systems.' In two systems, however, copper-zinc and iron-carbon, data are available for the calculation of activities over wide ranges of temperature and concentration. This activity data for the brass system is summarized in the preceding paper.= A detailed study of the solubility and distribution of carbon in iron is given by Smith and Darken.3 Their treatment of interaction energies is applicable only to dilute interstitial solutions. The objectives here will be to derive from activity gats given in the previous paper for the brasses and structural considerations as much new and detailed information as possible about the interactions between copper and zinc in metallic solid solution and the effect of these interactions in determining the short range structure of the equilibrium phases; that is, we shall investigate the energy of interaction between pairs of atoms of the same and different kinds, the deviations of the distribution of nearest neighbors from complete randomness, and show that the conclusions found are consistent with the observed behavior of the brass system. The method of treatment is fairly general for substitutional metallic solid solutions and will be applied to other systems. The determination of vapor pressures of the components of alloy systems is being undertaken in this laboratory to supply more data for this purpose. The information obtained from solid solutions may be extended by careful analogy to liquids as long as the metallic type of bonding is preserved. Since it will be necessary to employ the language of thermodynamics, a brief summary defining the terms used extensively in solution theory is given below. Solution Theory4 An ideal solution is one in which the vapor pressure of the constituent molecules

Jan 1, 1947

By William S. Hannan, H. Rush Spedden

FLOTATION may be defined as a process whereby mineral particles are concentrated by selective adhesion to air-liquid interfaces. The process involves attachment of desired mineral particles to air bubbles, and removal of the mineralized air bubbles from the surface of the pulp as a mineral concentrate. PROBLEM Although great strides have been made in understanding the principles of flotation, one part of the process which has not been adequately explained is the mechanism by which selected mineral particles become attached to air bubbles. A glance at the froth of an operating flotation cell demonstrates adequately that use of proper reagents and conditions will result in such attachments; but how such attachment takes place is not definitely known. A better knowledge of this factor might lead to improved flotation practice either through altered machine design or the application of scientific innovations. Direct observation of the behavior of mineral particles and bubbles in an operating cell does not appear promising because of the complexity of the system. For this reason, conclusions concerning the problem must be deduced from theoretical considerations or from observation of simplified systems designed to reproduce conditions thought to exist in an operating cell. PRESENT THEORIES Two mechanisms have been recognized as fundamental in particle-bubble attachment: gas precipitation and direct encounter. It is a simple matter to demonstrate in the laboratory that attachment can be brought about by either mechanism. As to the relative importance of the two in a particular flotation system, however, there is a divergence of views. Taggart1 states, Under exceptional circumstances sufficient force and time to effect attachment may conjoin in an ore pulp undergoing agitation, and a preformed bubble adhere to a collector-coated mineral particle, but the occurrence is rare. . . . Pulp-body froth flotation effects selection in the body of a conditioned pulp by causing gas bubbles to precipitate from solution in the liquid phase preferentially at the surfaces of collector-coated particles, and to cling to these particles. Gaudin2 states that, within the pulp body of an agitation machine, attachment of mineral particles to air bubbles occurs as a consequence of contact between the two. This theory has been supported by theoretical reasoning and much circumstantial evidence. Perhaps the most interesting bit of evidence in favor of this theory is the difficulty in the flotation of fines. If attach-

Jan 1, 1947

By Francis B. Foley

THE casting of steel in large molds brings into play all of the undesirable effects that result inevitably from slow cooling. The origin of the molten metal, whether basic or acid open hearth or electric furnace, has little if anything to do with the phenomena involved. If the quantity of molten metal to be cast in a single mold is large enough, there is very little one can do about it-the metal will cool so slowly that 'nothing one can do, other than to provide as good feeding as practicable from an adequate reservoir of metal in the sink head, will be of any avail. Recently we have had occasion to cast a 108-in. octagon ingot weighing 545,700 lb, necessitating the combining of metal from three 100-ton open-hearth heats. This is one of the largest ingots ever made. The body of the ingot weighed 448,800 lb, which includes a bottom pool of about 7500 lb of metal, and the sink-head weight was 96,900 lb, or about 18 pct of the total weight.

Jan 1, 1947

By Warren E. Wilson

The transportation of solids in pipe lines is a matter of deep concern in many fields of engineering. Much experimental and theoretical work has been done in an effort to devise means of designing pipe lines that will satisfactorily transport given solid loads, but there remain many unanswered questions in this field. The present discussion will be confined to a rather narrow portion of this field and will endeavor to point out certain factors that may well be considered when comparing the relative economy of various installations. The data have been presented previously but a new interpretation was prompted by a suggestion in a paper by Professor O'Brien,' of the University of California, that the friction work per pound of dry material should be considered in determining the relative efficiency of various installations. This method of considering relative economy in various pipe lines leads to some rather unexpected conclusions, especially with reference to the economy of large pipe sizes. A previous suggestion by the writer concerning the economy of a rather peculiar type of installation is strengthened. It is not believed that the considerations set forth herein apply directly in the case of dredge lines, where economy is largely a matter of a high rate of pumping in order to reduce the unit overhead charge. However, it is believed that some value may be gained from these considerations in cases involving the disposal of a fixed amount of solids per unit time with a minimum expenditure of energy and at a low cost for replacement of worn pipes. Such situations are not uncommon in the disposal of mill tailings and the disposal of solids deposited from irrigation waters. It was found that data leading to general conclusions for various pipe sizes were not available but certain definite trends are indicated and methods of analyzing available data are presented in the hope that they may be of assistance in preparing engineering estimates on designs of pipe lines of the type described above. Energy Requirements Carrying out the idea contained in Professor O'Brien's paper concerning the method of computing energy required to transport solids, the following analysis leads to some rather interesting conclusions. Let us represent: Solids load in terms of mass per unit time by w Ratio of mass of suspended solids to total mass of mixture flowing by p Volume rate of flow of mixture by Q Length of pipe by L Slope of energy grade line by s Mass per unit volume of solids by m8. Mass per unit volume of liquid by mi Mass per unit volume of mixture by 11 We then have as an expression for the solids load: w = pqmm The work done per unit mass, p, on the mixture to move it along the pipe the

Jan 1, 1947

By J. C. Williams

The operations described in this paper are those of the flotation plant of the Valley Forge Cement Co. at Conshohocken, Pa., and concern the use of a particular cationic reagent—namely, DP-243. The role of this reagent in this plant may be better understood by first considering the purpose of beneficiating cement rock in general and the specific problems at the Valley Forge plant. The ultimate purpose of beneficiating cement rock is to obtain a kiln feed of the desired chemical composition in a form suitable for the most efficient kiln operation. The chemical composition is governed by the type of cement to be made. Before government restrictions (the purpose of which is to simplify operations during wartime) limited the types of portland cement a manufacturer is permitted to produce, five principal types of cement were generally recognized by the industry. They are based upon chemical and physical specifications proposed by the American Society for Testing Materials, federal and other governmental agencies, state highway departments, water boards and other users of large quantities of cement. The physical as well as chemical specifications for any particular type of cement necessitate proper proportioning of the major components—that is, the silica, alumina, iron and lime—and it is necessary to establish and maintain definite limits for each in the raw mix. The manufacturer must then prepare a kiln feed of a composition that will yield a final product that will fulfill the desired specification. This step is further complicated for kilns using coal as fuel, by the amount and analysis of the ash introduced. The amount and nature of the dust lost during burning will also affect the composition of the kiln feed. The problem of preparing a kiln feed of the desired chemical composition is not a simple one, and it is the final product that governs the methods used to obtain such a feed. For example, in starting with a material deficient in lime for the mix sought, it may not be sufficient to raise it to the required lime content. The other constituents must also be present in the proper proportions. In some cases, it may be necessary to raise the lime content to a point greatly exceeding that of the final mix, then, by addition of one or more other materials lower in lime, obtain the mix. The rock used at the Valley Forge plant is a metamorphosed argillaceous limestone of the Jacksonburg formation, the same formation as that of the Lehigh Valley cement rock (which occurs approximately 50 miles north), and its oxide composition is similar to that of the latter. The only practical differences between the two are that, as a result of metamorphosis, crystallization of the Valley Forge rock is considerably coarser and it contains less carbon than the Lehigh Valley rock as well as slightly more magnesia in the form of magnesian mica. The calcium carbonate content of the various strata in the Valley Forge quarry ranges from about 65 per cent to over 85 per cent, the average for the entire quarry being somewhat under the requirement for manufacture of cement, which usually is from 75 to 76 per

Jan 1, 1947

By Charles Meyer, Reno H. Sales

AT Butte, successive zones of sericitized and argillized quartz monzonite occur around every ore-bearing fracture regardless of its size, attitude, or relative age. The two types of alteration always occupy the same relative positions; sericite adjacent to the ore-bearing vein, clay minerals always between the sericitized rock and fresh quartz monzonite, except where overlap of alteration effects between adjacent fissures has eliminated the lower grade mineralogical products, as is the case in much of Butte's Central zone of pervasive sericitization. As long as active circulation continued in the channel, each zone migrated away from the fissure, that is, it grew at its outer edge and simultaneously receded at its veinward edge because of encroachment by the next innermost zone. The different mineralogical and chemical responses within the wall rocks to the attack by the ore fluid are dependent not on a drastic about-face change of composition of the fluid in the channel relative to its ability to alter the quartz monzonite but on continuously varying conditions of physico-chemical environment within the wall rock outwardly from the vein.

Jan 1, 1947

By H. R. Banks

Pondering the action of a ball mill employed to carry on comminution from the product of fine crushing to the point where flotation, cyanidation or other concentrating methods are applicable, one wonders where this machine had its origin. When Henry Wadsworth Longfellow reiterated the observation of that older poet Von Logau, and wrote "Tho' the mills of God grind slowly, yet they grind exceeding small," he probably visualized the type of mill that was employed in medieval times for the production of flour, and can therefore not be considered as having gained admittance to the fraternity of millmen, on behalf of either poet. He does, however, make it quite clear that the efficiency of even these Mills of Destiny was low, and to that extent voices a characteristic of fine-grinding equipment that has been the bugbear of all metallurgical engineers. Principle of Ball Mill The principle of the ball mill probably is traceable to the action along the coast line of oceans or lakes, or in the mountain streams. Wave action on rocks and pebbles, close to the shore line, gives the potential energy to the grinding media, which, in their rolling and tossing, break down the sands, and the resultant "pulp" carried out from the shore is classified and settles out in sizes ranging downward to extremely he mesh. Surely, these are the real mills of God. If we allow our minds to dwell on the total tonnage that has been handled in this way, adding to the sands and clays at present in existence those enormous tonnages of metamorphosed sedimentaries we sense the vast quantity of rock that has been so reduced. Is it not likely, therefore, that the answer to the beginnings of pebble milling, and eventually ball milling, came through the perception of this natural mill by one of our engineering forebears? Methods of Grinding The relatively low return of mechanical input to a ball mill, in terms of useful work accomplished, has always intrigued me immensely. The potential energy absorbed by a ball raised to a high point in its path is apparently released with a very small return in useful work. Is the ball mill the most desirable means of he grinding, or is there some other method through which we can recover a reasonable amount of the energy input in terms of useful work? Some years ago, on his retirement, H. W. Hardinge was questioned as to his thoughts on the trend of fine-grinding equipment. As I recall, his prophecy at that time was that the most likely field for improvement in grinding media would be toward a charge of flat disks with some mechanical scheme to cause them to slide over each other. Undoubtedly, Mr. Hardinge went through the usual experience of the muller and bucking board, the customary introduction of the budding millman to his calling. I have often wondered, but have never got beyond the wondering stage, as to the

Jan 1, 1947

By Albert J. Phillip

Jan 1, 1947

By B. M. Larsen

IN spite of the great amount of operating experience and of studies directed toward elucidation of the interrelation of the several processes going on in the blast furnace, the present picture of its operation is based largely on indirect evidence and on speculation. The reason for this unsatisfactory situation is the extreme difficulty of making direct observations and significant measurements while the furnace is operating, and of translating laboratory experience to the conditions obtaining in the smelting process. Yet there are questions that can be investigated with some promise of a definitive answer; and it is the purpose of the present paper to set forth some of these questions, as a basis for discussion, which may, it is hoped, lead to active work on some of them. In order to provide a starting point for this discussion, some views held tentatively by the writer are outlined, along with a certain amount of evidence gathered from operating records and interpreted on the basis of the ideas expressed. These opinions may prove not to be pertinent, and may well not be in accord with the opinions of others; they have been included to encourage others to do likewise and on purpose to provoke informal discussion. In this way it should be possible to transcend the limitations of formal papers; to bring forth suggestions of new hypotheses or new methods of investigation; and to promote better understanding between investigators and operators in this difficult field. The statements made express the present views of one physical chemist who is not too familiar with all the difficulties of maintaining these enormous reaction vessels in reasonably smooth and economical operation; who, however, is persuaded that some of these difficulties would be less formidable if surer knowledge of the several interrelated and concurrent processes were available and made use of. For these difficulties arise largely, it is believed, from variation in conditions which the operator must meet as best be can, and should lessen as these conditions can be brought under control so that they are either made substantially constant or the variations are neutralized by compensating methods. A. VARIATION IN BURDEN AND IN MIXING OF CHARGE To the scientific investigator, who aims to control the conditions of experiment and to limit the number of variable factors, the most perplexing aspect of the blast-furnace process is that nothing seems to remain constant for long. Variations of burden seem to be unnecessarily frequent; and, even if the charge were constant from hour to hour, its constituents usually are not mixed as intimately as they might well be. It is understandable that separate layers of coke and of ore, also separate layers according to size, promote permeability and the

Jan 1, 1947

By J. A. Bowers

THIS investigation of the effect of bottom shape and life on slag volume was carried out in two Lectromelt top-charge furnaces whose rated capacity is 1000 lb per hour. Unfortunately, just as the work [ ] was started, our steel tonnage was reduced approximately one half, therefore we did not accumulate enough data from which to draw any definite conclusions. Furthermore, the life of the linings in these furnaces was greatly decreased by intermittent operation, which was a further handicap in making a study of this kind. The weight of the heats from which the data were taken varied 1200 lb but all the information was corrected to the standard weight charge for these furnaces of 4500 lb. Almost all the heats were plain carbon; a few contained a small percentage of added copper.

Jan 1, 1947

By A. M. Gavdin, F. W. Bowdish

Mineral dressing is an industrial art concerned with the treatment and separation of solids suspended in fluids. Knowledge and evaluation of the area of solid-fluid interface is important in all cases except those involving only large pieces of solid. In fact, many problems relating to comminution, to flotation, to thickening and classification, could be dealt with more rationally if the interfacial area were known. A number of methods have been proposed for the measurement of the surface of certain finely divided solids. Among them are methods using rate of dissolution of the solid,? its magnetic remanence,³ the turbidity of its suspension," and the character of the size distribution of the material.9 The first two are limited to one mineralogical species per sample; the third has certain optical limitations, especially for mineral mixtures, and the fourth is based on an extrapolation of uncertain validity. The need of a better and more general method of surface determination has long been felt, therefore. The method of P. H. Emmett,4 based upon the low-temperature adsorption of vapors, appears to fulfill this need. This method consists in determining the amount of nitrogen that is adsorbed by a given sample of solid at the temperature of boiling nitrogen. The more surface there is on the solid—both internal and external—the more nitrogen is abstracted. In actual operation, the method is somewhat less simple than has been stated so far, in that the nitrogen is adsorbed in an incomplete layer, the completeness and thickness of the layer being related to the pressure of the nitrogen in contact with the sample.2 This circumstance makes it necessary to determine the nitrogen adsorption for three or more values of the nitrogen pressure. Apparatus In the Richards Mineral Dressing Laboratories an Emmett apparatus has been built and tested (Figs. I and 2). A mechanical vacuum pump B and a mercury diffusion pump A work in series to give a high vacuum. The sample, placed in bulb D, can be evacuated by this pump train by suitable operation of the stopcocks in the glass tubing that connects the various parts of the apparatus. C is a McLeod gauge, used to ascertain the order of magnitude of the vacuum obtained, and not for accurate pressure measurements. Pressure measurements are made in the mercury manometer F and gas-volume measurements in the gas burette E. Gases are stored in flasks L (nitrogen) and K (helium), arranged so that definite quantities of these gases can be introduced into

Jan 1, 1947

By S. C. Oliphant, R. Floyd Farris

Presented in this paper is a summary of the results of experiments conducted in both the laboratory and the field during the past three years in connection with casing-perfora. tion problems. Included are studies of gun features that influence bullet performance and penetration, and studies of the effect of perforator bullets on casing and the neat cement in the annulus. Discussion and data are also presented relative to the accuracy of depth measurements in deep wells. Introduction It is a common practice in the oil industry to effect the completion of oil wells by setting and cementing casing through the producing horizons and perforating the section of casing opposite the desired interval by means of a gun lowered into the well on a cable or on the tubing. This practice has been followed for some time, and this method of completion has been given considerable study by the companies that render perforating service as well as by the oil companies that utilize their services. Through continued research on this subject, it has been possible to develop guns, bullets, and powder that will permit controlled firing at great depths, and penetration of as many as two strings of casing. It is the object of this paper to present the results of studies made of gun perforating in both the field and the laboratory. These studies were made to determine the factors that affect penetration of the bullet, burring of the casing, accuracy of depth measurements, and other items. It is hoped that by presenting the results of these investigations a better understanding may be obtained of certain of the factors involved in gun perforating and further investigation of the subject will be prompted. Subsurface Tests A well approximately 9000 ft deep, which was being prepared for abandonment, was selected for subsurface tests of gun-perforating experiments, In preparing the well for the experiment, 51/2-in. casing in the hole was pulled and racked in the derrick. A test section of pipe, which consisted of 65 ft of 5-in. 18-lb J-55 casing centered inside 7-in. 28-lb N-80 casing, was placed in the derrick corner and the annulus between the two pipes was cemented from the bottom up with 161/2 lb per gal neat cement, which was mixed and displaced with a cementing truck in the usual manner. After the cement had been allowed to harden for about a week, the test section was lowered into the hole on the 51/2-in. casing to a depth of 6600 ft by casing measurements. The hole was filled with drilling fluid weighing 10 lb per gallon. A perforating company was called to perforate the pipe, but was not advised that an experiment was being conducted. The company was asked to check the total depth (to cross pins in the bottom of the test section), then to raise the gun a given distance and fire a given number of shots with 1/2-in. bullets, pick up another distance and fire a given number of 3/8-in

Jan 1, 1947