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Allan Gibb, Mount Perry, Queensland, Australia (communication to the Secretary):—In drawing conclusions from his observations, Mr. Van Liew has apparently overlooked the reduction in weight that takes place in the content of the converter. The percentage-compositions of the matte, etc., are not directly comparable for determining the rate of elimination of the impurities; and, in the absence of exact weights (which in such an operation could not be obtained), it is necessary to determine the relation between the impurities and the copper with which they are combined at various stages, in order to get data that are comparable. Owing to a portion of the copper being removed in the slag, etc., the weight of copper in the converter is not a fixed quantity, but.it is sufficiently approximate to permit very reasonable comparison. The analytical data given by Mr. Van Liew, reduced to this basis (a ratio between the impurities and the copper with which they are combined), are shown in the table on page 958. From this table it will be evident that Mr. Van Liea's conclusions as to the source of heat at digerent stages are not quite correct. During the first 10 minutes, no iron is scorified, the heat being derived from the oxidation of the sulphur, of which 7 per cent. of the total is removed in this time. Prom

Jan 1, 1904

By R. E. Old

THROUGH the use of pressure and production records, formation properties and bottom-hole sample data, the performance of an oil reservoir may be studied analytically to define and evaluate the natural forces acting on and within the reservoir. Use is made of material-balance methods and the equations for natural water encroachment to estimate reserves. Methods for calculation of pressures are given. A study of the Jones sand, Schuler field, Arkansas, has been made and is given here to illustrate the value of the methods discussed.

Jan 1, 1942

By Samuel Lasky

WITH the movement of American capital into foreign investment, a new field of specialization for the American mining engineer is gradually opening a field hitherto entered almost wholly by chance and without full appreciation of its possibilities. Our age has been fitly called the "Age of Specialization." The special application of one's knowledge and ability to a definite and restricted branch of .his profession is purely a modern condition. Any profession, or branch of a profession or, industry, in which the problems may be segregated into definite types, calls for specializa-tion. Modern industry demands efficiency and that, reduction and ultimate annihilation of waste. Effort and time wasted by workers' on a problem with which they are not familiar is as flagrant a waste of money -the final standard-as any waste of materials. One of the subdivisions of mining engineering which is beginning to be recognized is of engineers who are clearly conversant with the particular and peculiar problems obtaining under foreign operating conditions. The need is as yet obscured, however, by the domestic prosperity of our American mining industry. The opportunity here lies more with the American engineer than with other nationals. The foreign en-gineer now in that service is not there through a realiza-tion of the special opportunities that exist, but through necessity, whereas, with the American engineer, more especially ,the recent graduate or those who will soon graduate, this is a new field to be entered wholly by choice. As a matter of fact, many engineering students will find it necessary to seek foreign service if they wish to remain in mining. Although the scope of the domes-tic industry is tremendous and there are many positions open to the junior engineer, there are not enough for the great number of graduates turned out yearly from our, mining schools. Educators tell us that less than 40 per cent. of the students in engineering schools gradu-ate; and of these but a minority continue in engineering. Even this minority is too great for our domestic. In-dustry, and although the young engineer realizes that condition after a few years he rarely seeks foreign work. A. perusal of the directory of the American Institute of Mining Engineers indicates that, but about one-half of one per cent of the Junior Associates are in positions outside of North America. Granting that most of them are still in school, the figure is surpris-ingly small.

Jan 1, 1927

By A. A. Collins

H. R. BIANCO*—I should like to ask Mr. Collins if that statement he made about the addition of drosses to the blast furnace slowing down the blast furnace is a result of his own experience or a result of the experience of some older metallurgists; and perhaps I should ask him to define the type of drosses that he means. A. A. COLLINS (author's reply)— That has been my own personal experience with dross. On various occasions at Chihuahua we attempted to incorporate the dross in our regular blast furnace charge and to shut down the dross re-verberatory to try to save some money. As expected, we had very poor results. I think that Ed Fleming will well remember on one occasion, that was back about 1933, when we attempted the first experiment along this line, and as a result of the sulphur addition to the blast furnace to matte out the copper we ended up with hanging furnaces and mushy slags and abandoned the dross experiment, once again turning to the use of the reverbera-tory for handling dross. H. R. BIANCO—Is that dross you refer to from the drossing kettle ? A. A. COLLINS—Yes, the dross that I am referring to came from drossing kettles. Furthermore, to back up my previous assertion, I had occasion in 1943, while up at Leadville, to once again experience the routing of dross through the blast furnace with its sulphur addition, since they had no dross re-verberatory, and to observe that once thf dross was removed, the furnace was speeded up almost 100 tons a day. All of these are personal experiences and I think that Mr. Feddersen also has had a little experience along this line —in fact, I believe all of us have had some experience. H. R. BIANCO—I know at Trail they recirculate considerable dross through the blast furnaces and we also recirculate dross at Herculaneuin and I am not aware that it has done much towards slowing down the blast furnace. A. A. COLLINS—We have always had very poor results. In the first place you have got to add a sulphur addition to pick up that copper and once you do that, that sulphur is apt to combine with some of the zinc and you are going to form a little mush; before you know it you have furnace hangs and a poor working furnace. Now of course that depends on the amount of zinc you have on charge. But in 1943, Leadville had roughly about 7 pet zinc in their slag and it worked very poorly. Previously when they had 4 or 5 pet zinc in their slag it did not matter. B. L. SACKETT* At Tooele we had a great deal of experience with copper. We have always been able to keep a lead well, however, in spite of the fact we have run as much as 5 pet copper and only 15 pet lead on the charge. But regarding the handling of dross, our dross reverberatory furnace is only 7 or 8 years old. Before that we recirculated the dross through the furnace and thought we were doing a pretty nice job. Of course these things are all more or less relative—in other words you establish a certain condition much better than one of a few years ago and possibly as good as any other of which you know and you think you have pretty good results. When we first took the dross off of the blast furnace and put it through the dross reverberatory furnace we immediately found out that we had gained something very real in furnace speed. Since that time there have been occasions when, because of the dross reverberatory being down, we have had to use dross again through the blast furnace and that has checked our original experience in slowing down the furnace very definitely. So we feel that a dross reverberatory is a very valuable asset at the Tooele Plant. A. A. CENTER*—Mr. Sackett's being here reminds me of trying to run with a minimum of lead concentrates the maximum of dross producing electrolytic zinc plant residue. He came up from International Smelting Co. to help us get started on that. We took an old copper blast furnace at Great Falls, Montana, and made a lead furnace out of it by putting a lead well on the other long side which of course is a very unorthodox lead blast furnace. Our aim was to treat the residue from the electrolytic zinc plant, as I said, with a minimum of lead concentrates. That meant a maximum amount of dross. At that time selective flotation was not general practice, so our zinc concentrates ran relatively high in copper and other dross-producing elements; and of course these were largely in the zinc plant residue. I think we might call it muscle metallurgy, but we had an interesting, successful experience there and we ran for over a year thanks to Mr. Sackett's helping us get started. I have the details, but time does not permit. We did well enough so that the A. S. and R. Co. at East Helena kept boosting up the offer to us for the electrolytic zinc plant residue and there was not enough lead concentrate to supply two lead smelters there in Montana, so the matter finally finished up by the A. S. and R. Co. taking all of the residue under long term contracts.

Jan 1, 1950

By Persifor Frazer

The rocks which cover the east flank of the South Mountain are chloritic schists typical in character. A specimen of this rock from near the Bechtel shaft, Hamilton Ban Township, Adams County, Pa., was selected and analyzed in my laboratory by Mr. C. Hanford Henderson, with the following results: Ignition,........2.740 CaO,..........7.040 SiO,,..........41.280 MgO,.......... 7.486 AI,O,,.........18.480 K,O,..........2.208 Fe,Os,.........9.440 Na,O,.........3.523 FeO,......... 8.200 100. As one penetrates the range by moving westvard, these schists are replaced either by epidotie quartz or by orthofelsite. In the former case, a belt of copper-bearing rock is traversed, but not in the latter case. Inasmuch as this junction of the chloritic schists on the southeast and orthofelsite on the northwest, separated by the epidotic quartz, is several times repeated, we find two or three copper belts arranged in general parallelism to the axis of the chain, because the copper horizon is generally at this junction. Thus, in going west from Fairfield, after entering the low spurs on the South Mountain, one is fairly within the chlorite measures. At the " Virginia Mills " a chlorite schist comes in with a dip of S. 1.5 E.-74 Half a mile up Middle Creek, large numbers of fragments of chlorite schist, decoruposed epidotic matter, and quartz are encountered. The former rock, where in place, dips E. 40" S.-57o. About 4000 feet west of the intersection of this road with the so-called Tape-Worm Railroad, near the house of one Singly, large masses of chloritie schist are found loose on the road. A hundred yards farther west, near a triangle in the road, the latter is less in quantity and much epidotic quartz appears, after which a very large display of orthofelsite succeeds on the left bank of Middle Creek. All these last-mentioned rocks, however, are in fragments. Crossing the stream again a few hundred yards farther On, the chlorite fragments at first preponderate, and then large numbers of both rocks

Jan 1, 1884

By G. Rinelli, A. M. Marabini

A wide-ranging series of experiments has been carried out on value minerals (sphalerite, smithsonite and hematite) and gangue minerals (quartz and calcite) to assess the properties of various commercially available vegetable and synthetic tannins as dispersants for these minerals in a finely ground state (<5 microns). Experiments to determine the dispersing power of each reagents on every mineral have been performed through sedimentation tests run first in water and afterwards in the presence of a collector having specific action on the mineral concerned. The tests have been extended to a wide range of dispersant concentrations, maintaining the pH and collector concentrations at the levels known to be the best for the flotation of the various minerals. By comparing the results obtained on each mineral, conclusions have been drawn on the possibility of using different classes of vegetable and synthetic tannins in the selective flotation of fine particles. These results have been related to the structure of the tanning compounds and to the surface properties of the minerals.

Jan 1, 1980

By Harrison Schmitt

SINCE the U. S. Geological Survey published the data on the Central Mining District collected by Lindgren and Graton1 and by Paige2 much new information has been obtained by development and mapping, but none of it had been published until recently when Kniffin3 published on Fierro, Lasky4 on the Ground Hog mine, Thorne5 on Santa Rita and Landon6 filed a thesis on the Fierro-Hanover-Santa Rita area at the Uni-versity of Chicago. During the years 1927-1930 much of the writer&apos;s time was spent in mapping the geology and ore deposits of this district, particularly in the area of the zinc deposits at Hanover. Some of the data collected are presented here. Previous publications have been freely drawn upon and additional data used that were generously supplied by L. M. Kniffin, Wilfred Wright and Gerald Ballmer. Thanks are due Augustus Locke, Samuel G. Lasky, Kniffin, Wright and Ballmer for suggestions and critical readings of the manuscript, and to the Empire Zinc Co. (a subsidiary of the New Jersey Zinc Co.) for the privilege of publishing material compiled largely at its expense. The relation of the Central. or the Santa Rita-Hanover-Fierro district to the Silver City district is shown on Paige&apos;s geologic map in the Silver City folio.7 Granodiorite porphyry and quartz-monzonite porphyry

Jan 1, 1933

By M. Baeyertz

SINCE 1915 many papers and books have covered industrial applications of X-rays from various angles. Two of the more recent are a paper by Fink and Archer1, which describes in detail the technique of radiography, and a paper by Clark2, which embraces the whole field of X-ray metallography. This paper, therefore, is confined to work of the X-ray Laboratory of the Western Electric Co., which naturally divides into two categories: radiography and diffraction patterns of various types.

Jan 1, 1930

By Paul Wilkinson

From the earliest times, the principal component of mallplaster has been ordinary lime. Plaster-of-Paris has also been known from early times, but never used to any extent in the actual base-work of plastering-materials; it is generally used for finishing over the brown coat and for ornamental work. As an illustration of the antiquity of the use of gypsum-plaster for mortar, I find that the analysis of the exterior covering of the pyramid of Cheops, as made by Dr. Wallace, is almost identical

Jan 1, 1898

By J. W. Rutter, K. T. Aust

The temperature dependence of the rate of grain boundary migration was measured in bicrystals of zone-refined lead containing from 20 to less than 1 ppm by wezght of tin. The apparent activation energy in the temperature range from 320" to 200oC is markedly dependent upon the solute tin concentration and upon the orientation relationship of the grains adjacent to the grain boundavy. The quantitative experimental observat~ons are compared with the predictions of various theories of grain boundary migration. In previous work.&apos;?&apos; the mobility of individual grain boundaries was studied as a function of impurity concentration and type of boundary. Grain boundary migration occurred at the expense of dislocation arrays which were introduced into the specimen during solidification. Boundary mobility in zone-refined lead at 300°C was markedly decreased by small additions of tin. 0.004 wt pct being sufficient to decrease the rate of grain boundary migration by a factor of 1000. The mobility of grain boundaries having polar orientation relationships near 38 and 22 deg about <Ill>, and 28 deg about <100>, was much less sensitive to tin concentration in the range studied. As a result, these boundaries have relatively high mobilities. The present paper is a continuation of the above study. Data are now presented on the temperature dependence of the motion of individual grain boundaries in zone-refined lead as a function of solute tin concentration and orientation relationship of adjacent grains at the grain boundary. The experimental observations are compared with the predictions of a number of theories of grain boundary migration3-8 which, prior to the present experimental investigation, could not be critically evaluated. EXPERIMENTAL PROCEDURE The striation or lineage structure of melt-grown single crystals of zone-refined lead, containing various additions of tin, was utilized to provide a driving force for grain boundary migration, as previously described.1,2 Each grain boundary under study separated the striated single crystal from another grain which was introduced by localized plastic deformation and recrystallization of a small region of the sample. The speed of migration of grain boundaries in dilute alloys of tin in zone-refined lead was investigated as a function of 1) tin concentration from < 0.0001 to 0.002 wt pct, 2) temperature in the range of 200" to 320°C, and 3) orientation relationship of the adjacent grains at the grain boundary. The substructure driving energy available for grain boundary migration was estimated to be about 4000 ergs per cu cm, within a factor of two, from specimen to specimen.&apos; The specimen dimensions, and growth and alloying procedures for the preparation of striated single crystals of lead of known tin composition, were as described previously.&apos; Each bicrystal was carefully wrapped in aluminum foil, and annealed in a well-stirred salt bath consisting of 50 pct NaNO2 and 50 pct KNO3, for known periods of time at a series of constant temperatures (*2°C). The grain boundary positions, before and after each anneal, were determined by etching lightly in a solution of 5 pct nitric acid in methyl alcohol, in order to follow the motion of the boundary and determine its rate of migration. Thus, the rate of motion of the grain boundary in a single specimen was measured at various temperatures. The above procedure was carried out for each grain boundary in seventeen different bicrystal specimens.

Jan 1, 1960

By Dennis K. Mortensen

Startup of the 9000 tpd Sacaton concentrator is expected to increase Asarco&apos;s domestic copper concentrate capacity by 21%. The plant site is located due west of the mining operations, consisting of both crushing and concentrating facilities. Arthur G. McKee & Co. served as the prime contractor for the project. The Sacaton mineralization contains both sulfide and oxide ores. Primary mineral constituents are chalcocite, azurite, malachite, chrysocolla, and minor amounts of silver and occasional gold. Sulfides are distinguished from oxides when more than half the total copper content is in the form of a sulfide copper mineral. While non-sulfide copper minerals are considerably less prevalent throughout the orebody, they tend to occur quite intimately with the sulfide minerals, particularly in the upper zones of the mineralization. For this reason the decision was made to treat all the ore in a flotation circuit using existing sulfidizing methods.

Jan 11, 1974

By C. Schlumberger, M. Schlumberger

The object of this paper is to clarify the idea, so important when exploring by potential methods, of the depth of investigation attainable by electrical measurements. After defining, with some precision, .the term "depth of investigation&apos;&apos; in geophysics, the authors show how it is possible to regulate this depth in potential methods and to obtain an &apos;electrical drilling" from surface observations. They consider also the difficulties encountered in deep measurements and indicate how it is possible to reach greater depths than those having an industrial interest. Depth of Investigation The term, depth of investigation, in its general sense, is easily understood. For instance, a driller who can pull cores from a depth of 2000 m. is capable of working, with accuracy, to that depth. By means of a properly placed drill, he may locate an orebody at a depth of 1999 m., however small this orebody may be. On the contrary, the term as used in geophysics requires precise elaboration. As a matter of fact, no geophysical method, irrespective of the physical property studied (density, magnetic permeability, conductivity), can discover a very small body at a great depth because, in practice, the physical parameter upon which such a geophysical method is based is never regular enough, throughout the ground, to distinguish the feeble anomaly caused by the small, deep-lying body from the numerous anomalies due to irregularities of the encasing terrains. Aside from this question of the ratio between the size of the body being hunted for and its depth of burial, a second factor plays its role in the possible depth of investigation; that is the difference, for the parameter under consideration, between the body and its surrounding material. The greater this difference, and the more homogeneous the encasing terrains, the greater is the possible depth of investigation. This being generally established for all geophysical methods, it is possible to distinguish two main classes of these methods, from this same point of view

Jan 1, 1932

By S. Acar, P. Somasundaran

The results obtained for the selective flocculation of natural ores do not usually agree with the corresponding properties of the constituent minerals when present alone. This is mainly due to the presence of dissolved mineral species which can interact in many ways with other components in the system and alter their behavior. In this paper, the effect of dissolved species on the flocculation and electrokinetic properties of sulfide minerals is discussed. Dissolved iron, copper, and nickel (Fe, Cu, and Ni) species are found to affect the properties of natural chalcopyrite and pentlandite in certain pH range. These effects are interpreted in terms of species adsorption leading to activation or depression of reagents, surface precipitation, and complexation of species

Jan 1, 1986

By M. A. Scheil, S. L. Hoyt

About three years ago eight standard steels were prepared for the cooperative investigation of methods for oxygen analysis, sponsored by the Iron and Steel Division of the American Institute of Mining and Metallurgical Engineers and by the National Bureau of Standards. A preliminary report of the results was made at the annual meeting of the A.I.M.E. in February, 1936. † This report showed the reliability of vacuum-fusion methods and further brought out certain advantages of the fractional vacuum-fusion method. The results obtained by the authors with the latter method will be discussed here, with some comments on the procedure for those who are interested in determinations of gases in steel. Some additional comments are offered on the use of the polarizing microscope for identifying the inclusions in the steel to check and amplify the findings of the fractional vacuum-fusion analysis. For details of the fractional method, see the paper by L. Reeve1. Degassing the Crucible One of the sources of error in vacuum-fusion methods has been the blank gases evolved from the graphite crucible after preliminary out-gassing. We have used 1750" C. as the outgassing temperature. This gives a base pressure at that temperature of less than 0.030 mm. after one hour and of 0.004 mm. on dropping the temperature to 1575" C. At lower extraction temperatures the base pressure is 0.001 mm. at 1050" C., 0.002 mm. at 1170" and 0.003 mm. at 1320&apos; C. Because of the size of our induction coil we are limited to this temperature, although it &apos;would be advantageous to use 1950" to 2000" C. Hamilton2, after outgassing at 1850" C. for 100 min., was able to reach a base pressure of 0.001 mm. for a temperature of 1700&apos; to 1725" C. This would give a blank corresponding to less than 0.00015 per cent 02 and 0.00005 per cent H2. Chipman and Marshall outgas at 2000" C. for one hour by using a special construction

Jan 1, 1937

By G. Howell Clevenger

FORMERLY great divergence of opinion existed in regard to the influence of copper in steel, as affecting its various physical properties. More recently the investigations of Stead,1 Breuil,2 Wigham,3 Burgess and Aston,4 Ball and Wingham,5 Miiller,6 Dillner,7 and others have shown fairly good agreement in the major points. Copper steel has been shown by these investigators to possess special properties which make it valuable for certain uses. The general range of composition of the useful alloys of copper and iron, and of copper, iron, and carbon, has been quite definitely established, for the former by Burgess and Aston,8 and for the latter by Breuil 9 and Stead.10 Stead 11 has removed one difficulty in reconciling certain of the earlier data by calling particular attention to the influence of carbon in copper steels. Another point which caused confusion in the earlier investigations, particularly in regard to " red-shortness," was the presence of sulphur. Failure to note the presence of sulphur often led to attributing " red-shortness " to the presence of small amounts of copper. Turner 12 has called attention to the fact that where copper exists in an iron ore it often occurs as the sulphide, so that the presence of copper in steel made from such ores might also, necessarily, mean the presence of sulphur. It is evident that the effect in this case might be quite different than where pure copper was added.

Jan 10, 1913

By Lawrence Adler

In-situ rock has well-recognized rupture and yielding responses. Attention is called to an intermediate response, granulation, which consists of an evenly distributed, small-scale crumbling accompanied by swelling. Granulation results in a negative slope for the inelastic portion of the stress-strain curve as successive interlocks are destroyed, and the load-carrying capacity of the material is reduced. Volumetric swelling with softening also takes place. The prerequisites for such a response are moderate confinement and a uniformly distributed defect pattern. Since rock masses, as well as rock as an intact material, have such patterns in their jointing and texture, respectively, granulation is characteristic of them. The presence of granulation can be demonstrated for a very wide scale, ranging from laboratory testing to regional geologic phenomena. The response of an engineered structure is considered in detail. Granulation appears to be dependent upon internal moments, the formation of which can be controlled by engineering design. The practical implications of such control can be significant in optimizing underground instability and in improving excavation techniques. Rock is usually considered to behave inelastically under high load, by fracturing as a brittle material, or by yielding as a ductile material, ignoring time dependency. These responses, which are characteristic of metallic behavior, appear idealized in Fig. 1, where linear-elasticity approximates the initial behavior. However, another major deformation mechanism peculiar to rock has long been recognized in geology, the granulation of an interlocked material. Granulation consists of a uniformly distributed fracturing and crumbling of the material, accompanied by swelling and softening. Predictably, the associated inelastic portion of the load-deformation curve has a negative slope,

Jan 1, 1971

By V. Koump, T. F. Perzak, R. G. Olsson

The rate of dissolution of recrystallized alumina in molten iron oxide in equilibrium with iron at 1450°C was studied by rotating alumina disks in the melt. The samples were rotated from 1 to 12 min at speeds from 54 to 3270 rpm. It is concluded from the experimental results that the process is limited by diffusion in the liquid boundary layer. The interdiffusion coefficient for the dissolution of alumina disks in pure molten iron oxide was estimated to be about 3 xl0-5= sq cm per sec. THE erosion of refractory materials is of considerable importance in iron- and steelmaking processes. Since many refractories contain alumina, this investigation was undertaken to develop a further understanding of the erosion mechanism. Shurygin et al.1-3 have investigated the rate of dissolution of alumina in molten silicates and molten fluorides by rotating alumina disks in various melts. The rates were reported to be limited by diffusion in the liquid boundary layer. In the present investigation the rate of dissolution of alumina in molten iron oxide in equilibrium with iron was studied in a similar manner; alumina disks were rotated at different speeds in molten iron oxide at 1450°C. The relationship between the rate of dissolution of the flat surface of the disk and the speed of rotation was used to determine whether the process is limited by diffusion in the liquid boundary layer or by some chemical reaction mechanism. APPARATUS AND EXPERIMENTAL PROCEDURE A schematic diagram of the experimental apparatus is shown in Fig. 1. The iron oxide melts were contained in 2-in.-diam high-purity iron crucibles that were centered in a cylindrical graphite susceptor. Prior to each sequence of experiments, sufficient reagent-grade ferric oxide was added to a crucible to form approximately 350 g of molten iron oxide; the depth of the melt was about 11/2 in. To prevent excessive erosion of the crucible, about 70 pct of the required iron was added to the crucible in the form of iron powder. The mixture was melted in an atmosphere of purified argon by induction heating with a 250-kc generator. After the oxide was molten, a Pt/Pt-10 pct Rh thermocouple at the exterior of the crucible was calibrated against an iron-sheathed thermocouple immersed in the melt and was thereafter used to regulate the melt temperature. All experiments were conducted at 1450°C with a probable error of 10°C. The alumina disks were constructed from pure re-crystallized alumina having a density of 3.7 g per cu cm (porosity approximately 6 pct). For each disk sample a 1-cm-diam alumina cylinder of known length (0.9 to 1.0 cm) was cemented into a ground seat at the end of a 1.27-cm-OD centerless ground alumina tube. The ends of the tube and cylinder were flush and served as the disk surface. When mounted in the apparatus the alumina tube was guided by tungsten carbide bearings and rotated by a variable-speed motor. The bearing and drive assembly could be raised and lowered in order to allow the sample to be quickly moved in and out of the melt. At the start of an experiment, a sample was preheated for several minutes directly above the melt, and then immersed in the middle of the melt to a depth of a in. and rotated for 1 to 12 min at speeds of 64 to 3270 rpm. The speed of rotation was measured by a hand tachometer. At the start and completion of each experiment, a melt sample was withdrawn with a cold copper rod and the alumina content was determined by chemical analysis. During individual experiments the alumina concentration of the melt changed by the order of 0.25 wt pct. Average melt compositions for individual experiments were used in the subsequent computations and were in the range between 0.12 and 4.3 wt pct alumina. The extent of dissolution was determined by sectioning the end of the sample and measuring the final length of the alumina cylinder with a microscope. Since the exposed end of the cylinder, i.e., the disk surface, was etched in a manner characteristic of this geometry, a number of measurements were made on

Jan 1, 1969

By Persifor Frazer

I DESIRE to say that, owing to the number of papers which have been more or less crowded at this session of the Institute, and the fact that, as one of the Local Committee, I have the distinguished honor to feel somewhat like one of the hosts, I should not tax the patience of members at this late hour, but would have my paper read by title were it in any way possible to do this. But the task I have set myself this evening is to present to the eyes of the members of the Institute certain objects which have occupied more or less of my time during the last eighteen months or two years. The objects I allude to are some of the igneous rocks of this country, which, until quite recently, have been less understood than any others. It will be well known to some of the members that some of the cooled lavas of a previous age of our planet, when not directly coarsely crystalline and granular, were considered and spoken of as " natural glasses," or perfectly uncrystalline, vitreous, or hyaline masses of matter. Among the first results of the use of the microscope was the dispersion of this fallacy. Sir David Brewster, Mr. H. C. Sorby, and William Nichol (the discoverer of the celebrated calcite prism, which bears his name), had, with greater or less success, examined sections of various rocks and minerals, both by transmitted and reflected light, and also in the form of powder. But, until the genius of Vogelsang undertook the subject, these investigations had no permanent value, nor did they constitute an independent line of mineralogical and geological research. Since the close of his labors, by Vogelsang&apos;s premature and much-lamented death, the subject has been made one of renewed interest by his brother-in-law, Ferdinand Zirkel, as well as by Rosenbusch, Tschermak, and many others abroad, and at home by the commencement of a systematic study of the traps of Connecticut by Messrs. E. D. Dana and G. W. Hawes, of New Haven, and by the splendid set of described sections of the traps of the West which have been furnished by Zirkel to illustrate Clarence King&apos;s report. I had the honor of presenting a large number of thin sections of our traps at the Washington meeting, for the inspection of the members, with the aid of a table microscope belonging to the Smithsonian Institution. Here I propose to project these sections upon the

By Robert M. Dreyer

During the past two decades, synthetic abrasives have taken over successively greater percentages of the high-grade abrasive market, so that now, with the exception of natural diamonds (discussed in section 3.15.4C of this chapter), the importance of natural high-grade abrasives is negligible. The predominance of synthetic abrasives is indicated in Table 15.4A.1. This shows that the 1968 value of domestically produced synthetic abrasives (excluding synthetic diamonds) was over $80 million, whereas the value of garnet, the largest domestically produced, natural high-grade abrasive, was less -than $2 million. The major synthetic abrasives (other than synthetic diamonds) are: alumina, silicon carbide, boron carbide, tungsten carbide, and metallic oxides, including various iron oxides. A major advantage of synthetic abrasives is that the size and shape of grain can be closely controlled during manufacture. Although Table 15.4A.1 gives the average price of synthetic abrasives, such averages are of somewhat limited value. This is because the actual price varies within wide limits, depending on composition, hardness, size, and shape of grain. In 1968 the approximate total consumption of abrasives in the United States was valued at about $200 million, of which about two-fifths was in the form of synthetic abrasives (other than diamonds), one-third in synthetic diamonds, and the remainder in natural diamonds. Natural abrasive products, such as silica sand, tripoli, and pumice, are important in the low-cost abrasive field. Of the low-cost abrasives, silica sand continues to be the most important, with domestic production of about 300,000 tons at a value of $1.8 million (see Table 15.4A.1). In general, the lower the sales price of the abrasive product, the more limited is the market which can be served from a given production center. Each abrasive has applications for which it is especially useful, but there is a continual struggle among abrasive suppliers to induce substitution of one product for another. Such substitution can be stimulated by changes in method of preparation affecting hardness, shape, and size of grain.

Jan 1, 1976

By A. H. Tousley

The cement industry is on the horns of an economic dilemma. Within the last ten years, its over- capacity in the United States has varied from 139- 127% of demand (Fig. 1). The most direct effect of this is seen in cement prices, which reached a peak in 1960, retreated steadily through 1966 and only recently climbed back to the 1960 level again. With prices in a slump and production costs estimated to be up almost 30%, there has been a steady drain on cement profits. Since 1960, labor costs have increased 86% while fuel costs have risen 18%. Meanwhile, customer service costs have also soared owing to the competition for cement customers and the wider variety of available cement products. This search for sales advantage has in turn led to a higher Blaine number, which means more grinding and hence bigger mills, more power, and, once again, higher costs. New plants as well as expansions and revisions to existing plants are also costing more owing to higher

Jan 1, 1971