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By Subhas G. Malghan

Feldspathic deposits occur widely throughout the United States, but North Carolina, California, Connecticut, and South Carolina accounted for over 80% of the total domestic feldspar output for the year 1973.1 Pegmatites and granites constitute the major feldspar reserves of the United States, 2 and in addition, feldspar is produced as a byproduct by firms whose major products are spodumene and mica. 3 Feldspar flotation is practiced in the United States, Mexico, Finland, Norway, West Germany, Japan, and the USSR. According to the US Bureau of Mines estimates, the production of feldspar in the United States and rest of the world were 704,000 and 2,514,000 t, respectively. Feldspar is principally used as a flux in making glass, pottery, porcelain, enamel, tile, and other ceramic products. In recent years, the domestic feldspar industry is faced with a number of problems. As a result of increased cost of energy and the introduction in 1972 of new legislative programs relating to air, water, and noise pollution, land-use restrictions, and mined-land rehabilitation, the production costs have increased. Apart from the increased cost of operation, an operational problem exists with the feldspar producers in North Carolina, especially those in the Spruce Pine area. This problem is concerned with the use of hydrofluoric acid in the feldspar flotation. Feldspar producers in Spruce Pine, NC, have been discharging process waste water into the North Toe River. The mill waste water contains active fluoride ions. Fluoride in excessive concentrations is undesirable in waters used for drinking. It is stated that water containing 0.9-1.0 ppm fluoride will seldom cause mottled enamel on children's teeth; and for adults, concentrations less than 3-4 are not likely to cause endemic cumulative fluorosis and skeletal effect. Although the literature on this subject is rather confusing and inconclusive, the inference that concentrations over 4 ppm may affect bone structure is clear. According to the recent Federal Register,4 maximum fluoride level of 1.4 ppm at 79°-98°F is considered to be adequate and safe for the protection of health of the consumers. The EPA and state environmental agencies have accelerated their drive to reduce water pollution on a faster schedule. By 1977, the EPA specifications for maximum contaminant level of fluoride ions in the discharge waters of feldspar milling operatins is expected to be reduced to 2.0 ppm. The other problems of using hydrofluoric acid are the following: toxicity, hazards of handling and storage, and high cost as compared to other inorganic acids (almost 16 times the cost of sulfuric acid). In order to reduce fluoride levels in mill discharge waters, mining companies have taken the following steps: I) Recirculating a part of their mill water. Even though recirculation of mill water seems to be a novel method of reducing fluoride contamination of the discharge water, there are certain operational and handling problems. 2) Conducting research on the treatment of fluorides in mill waste water. The technology of treatment of fluoride ions has received considerable interest in the recent years. A recent research report5 estimates that the cost of fluoride ion removal to meet the present specifications in the feldspar industry is approximately $0.25/t of ore processed, and about $0.50/t of feldspar produced. At the request of the feldspar producing industries in North Carolina, the North Carolina State University (NCSU) Minerals Research Laboratory has taken up a research program directed towards overcoming the fluoride ion pollution problem. After a close study of the operational, technical, and economic aspects of feldspar flotation, it was decided to attempt to replace the conventional hydrofluoric acid process. Conventional Feldspar Flotatin Using Hydrofluoric Acid Since the inception of the feldspar flotation process using hydrofluoric acid by O'Meara2,6 the process has achieved a great commercial success. In the conventional flotation separation of feldspar-quartz, hydrofluoric acid is used to suppress quartz and activate feldspar, and a long chain amine salt (acetate or chloride) is used as a collector. The bulk of amine collectors used in current feldspar operations are applied as the water-soluble acetates of the free-base amines. These products are pastes or waxy solids which are available in a range of acetic acid neutralization levels generally 50 to 100% neutralized. In spite of the problems mentioned in connection with the use of hydrofluoric acid, this process is extremely stable with respect to changes in the process variables. With the exception of a few operations, alaskite and pegmatite are the major sources of feldspar.7 In the flotation treatment of a pegmatite that contains iron-bearing minerals (heavy minerals), mica, feldspar, and silica, a logical order of removal presents itself considering the following:8 1) Mica is readily floated by an amine collector in a pulp pH 3.5. Some iron-bearing minerals will usually respond to amine collector in acid circuit with the mica concentrate. 2) Since iron minerals tend to occur invariably in the feldspar concentrate, it is desirable to remove most of these prior to feldspar flotation. A fatty acid or a petroleum sulfonate collector used in this flotation step in acid circuit will float iron-bearing minerals. 3) Using hydrofluoric acid to maintain pH of 2.5, an amine collector employed in a final step will float feldspar away from silica, usually leaving the latter in the tailing as a high-grade silica concentrate. The problems connected with the flotation separation of feldspar-quartz arise due to the similarities in their chemical structure. Therefore, any reagent system that is likely to succeed in feldspar-quartz separation should have adsorption affinity towards one of the minerals and depression effect towards the other mineral.

Jan 1, 1979

By Thomas Kesler

THE Cartersville mining district, 35 miles northwest of Atlanta, Ga., has been of varying but continuous importance in the southern mineral industry during the past century. Noted chiefly for its production of brown iron ore, manganese oxide ores, barite, sienna, and magnesian limestone, the district and its environs have produced brick and tile clays, slate, gold, bauxite, and graphitic schist. Minor deposits of serpentine, sericite schist, copper ore, and red iron oxide have been prospected. The obvious deposits of brown iron ore, together with some associated specular hematite, were mined out years ago, although a little ore was left in the workings. Moderately steady production of sienna reached a peak about 1930, then declined rapidly. Manganese mining passed through a relatively active period from the World War to 1931, but has subsided to a small but rather constant output for the Birmingham market. How-ever, the White Manganese Corporation has prepared for possible increased production by constructing a new washer capable of handling about 300 tons of ore per day. Principal activity in the district proper has centered for some years in the production of barite and magne-sian limestone.

Jan 1, 1940

Jan 1, 1885

By M. D. Curran

AS applied to coal, the term processing is subject to many interpretations. To some it means preparation of coal for the market by mechanical means such as crushing, sizing, washing, or treating with oil or chemicals to eliminate dust or improve combustion quality. To others it means conversion of the coal to other commodities as in carbonization to produce coke and by- products, or to liquids by application of the hydrogenation process. I prefer to classify the various forms of mechanical treatment under the heading of beneficiation and apply the term processing to those methods of treatment that destroy the coal sub- stance through distillation or hydrogenation.

Jan 1, 1939

By John W. Buch

IN my review a year ago I pointed out that a small coal-mining companies as well as large had decided that the so called ?central shop? was a benefit. These central shops replaced in a large measure the commercial shops operated by those who have no direct connection with production of cod. Central shops in this time of salvage and major repairs have proved their worth. In addition, many of the larger companies had in their central shops equipment available for the production of many thousands of parts for our vast war machine and, as subcontractors, are doing this type of work. This is a real contribution to the war endeavor. Lack of new supplies has resulted in exhaustion of those stocks formerly stored or hidden in underground shanties. This means that the small stock of repair parts likely LO be available to any mine

Jan 1, 1943

By Frederick Prime

The Great or Cumberland Valley, which (under a variety of names) extends from Canada, through Vermont, Massachusetts, Connecticut, New York, Pennsylvania, Maryland, Virginia, and East Tennessee, to Alabama, is composed in part of limestones lying immediately above the Potsdam sandstone. Geologically, they belong to the era between the Potsdam and Trenton, and are commonly termed Calciferous. A peculiarity of these limestones is their great richness in limonite or brown hematite ores, which form a large part of the charges of the many blast-furnaces situated on their outcrops. The mines from which the ores are obtained are (properly speaking) only pits or quarries, from which 'the ore is extracted by means of picks or shovels, powder being rarely employed. The ore does not occur casually at any point in the limestone, but forms regular lines, following apparently the outcrops of certain beds. In Lehigh County, Penn., where 1 have been engaged on the Geological Survey of the State, during the past season, there are three or four of these lines. During the progress of the survey I was much struck by the fact that the two most important and promising lines of outcrop were, one at the base of the crystalline schists (forming the South or Lehigh Mountain), and overlying the Potsdam sandstone conformably; the other, near the line of junction of the calciferous limestone with the slates of the Cincinnati epoch. The mines along these two lines, following the topography of the country, were in place, richer and more permanent than those of the belts between, which were generally leaner. A peculiarity of these two lines of outcrop, and one to which I particularly desire to draw attention, is the occurrence of what I at first mistook for a highly altered slaty limestone, but which subsequent analysis proved to consist in great part of damourite (hydrated potash mica). The following are analyses of this damourite slate: I. From Fogelsville, Lehigh County, within a few hundred feet of the contact of limestone and slate, by Dr. F. A. Genth. 11. From Hensingerville, Lehigh County, within 300 feet of gneiss, by Mr. Sydney Castle, of the University of Pennsylvania. 111. From Allentown, Lehigh County, within 150 feet of con

By Joseph Daniels

(San Francisco Meeting, October, 1911.) I. THE FRITZ ENGINEERING LABORATORY. TEE Fritz Engineering Laboratory was built under the direction of John Fritz, and presented by him to the University. A view of the building, looking east, is shown in Fig. 1. . The building was started in 1909, and completed in 1910, although all of the equipment was not placed until later. Mr. Fritz gave his personal attention to the details of construction and equipment, and it was his custom to drive over every day to the University from his home in Bethlehem, and spend some hours watching the work, offering suggestions, making changes, and planning new work. The result is a building and an equipment which embody his practical ideas. The laboratory structure is of the steel mill-building type, of light-colored brick, 91 by 114 ft., of which a section is shown in Fig. 2 and the floor-plan in Fig. 3. The steel frame carries the roof and traveling crane-way. Ample light has been provided by numerous windows in the side and end walls, in the clerestory, and by a skylight, 84 ft. long and 9 ft. wide, in the north roof. The main aisle of the building is 49 ft. 2 in. between centers of crane-columns, and has a clear height of 40 ft. The remainder of the width is taken up by two side aisles, 18 ft. high. The laboratory consists of four sections: (1) A general testing-section, containing the testing-machinery, a small machine shop, and an office; (2) a cement-testing room; (3) a room for making and storing concrete test-specimens; (4) a hydraulic section.

Feb 1, 1912

By C. D. Ramsden

DURING the war years of 1941 to 1945, maintenance of mine locomotives and other mine equipment took the form of rebuilding rather than of renewing. Pur¬chase of new parts became increasingly difficult and mine operators found it necessary to maintain equipment by sal¬vaging old parts. Mine-locomotive wheels, although not representing a high cost per pound of material, contain a con¬siderable amount of steel and without rebuilding would have to be scrapped long before even a moderate percentage of the steel in the wheel is actually consumed. Many mine operators have been re¬building locomotive wheels for several years with automatic open arc-welding equipment. In 1927, the Pittsburgh Coal Co. started such a program, using a single Westinghouse automatic welding head. Since that time, many refinements have been added, until in 1944 the setup was operating very efficiently. A desire to increase wheel life and to hold down rising costs led the company in 1944 to investigate the possibilities of the under¬flux arc-welding process for wheel rebuild¬ing, although at that time, little or no work had been done on multiple pass or "build-up" welding with the underflux arc. Work with this process had been confined largely to welding together flat plates in a "down hand" position. Possibilities for savings were intensified by the fact that the company has 300 locomotives in operation, using actively or as spares 1200 sets of wheels. During 1942 and 1943, about 500 sets of wheels were sent each year to the company's maintenance shop at Library, Pa., for rebuilding. Based on having 800 sets in service (many of the company's heavy locomotives have three- sets of trucks), the average life of a set of wheels was approximately 19 months. Anything that could be done to increase wheel life promised sizable annual savings. OPEN ARC WELDING With the open arc process, a set of wheels could be rebuilt for about 40 pct of the cost of new wheels. Underflux arc welding gave promise of greatly increased welding speeds, more homogeneous, dense deposits and the chance for use of a wider range in welding-wire compositions. Against this was ranged the higher cost of materials and the cost of developing the process from the theory to a practical reality. Since 1927, when a single open arc head was placed in operation, fixed welding procedures had been gradually developed, a positioner for handling a set of wheels was built, and a second head was placed in operation in order to weld two wheels simultaneously. The fixture, or posi¬tioner, which was built to position and turn the wheels under the two welding heads, included a motor drive, controlled by a rheostat, which rotated the wheels through a double set of speed reducers and a removable jaw coupling attached to one end of the axle of the wheel truck.

Jan 1, 1946

By Michael Tenenbaum

Selected characteristics of nonmetallic phases were determined in low-carbon sheet steels which had been produced by various refining; deoxidizing, and casting procedures. The results showed little influence of the refining process on the quantity, distribution, size, and character of the nonmetallic phases. The quantity of inclusions was governed by the deoxidation procedures. While the mode of casting influenced the internal structure and the pattern of inclusion distribution, it had little effect on the quantity of nonmetallics. The vast majority of inclusions were under 30 µ in diam, and there was little change in size distribution during hot and cold rolling. The composition and structure of the inclusions were expained an the basis of known equilibrium phase diagrams for the appropriate systems. Additional work is needed to explain some of the observations of this paper. HENRY Marion Howe's contributions to the metallurgical profession include his many writings, the wisdom that he imparted to his students, and the inspiration that he gave to the many scholars, teachers, and industrialists who knew him personally. It was Professor Howe's intimate colleague, Albert Sauveur,1 who, in the first Howe Memorial Lecture, could have been speaking for the metallurgist of our generation as well as his own when he wrote, "...how many of us on the point of going astray were called back to the right path by Howe's guiding torch?" More than a quarter of a century later, Francis Foley,2 one of the last in the Howe Lecture series who worked directly with the great man, delivered the ultimate tribute, "...truth, in its time is so hard to identify." While Professor Howe strove to be right, "he was content if he provoked the reader to take the next step along the path to greater knowledge." Like so many of my predecessors, I sought guidance for this lecture by referring to Professor Howe's two classic texts, Metallurgy of steel,3 and Metallography of Steel and Cast Iron: the former book interpreting the facts as he saw them near the start of his career, and the latter—published 26 years later—pointing to many fertile fields for metallurgical investigation. Those of us who harvest the fruits of Henry Marion Howe's contributions to the metallurgical profession now look with wonder at the tremendous legacy he has provided. It is rewarding to study his writings and to recognize the anticipation of such aspects of modern ferrous metallurgy as: 1) Direct reduction 2) Steelmaking reactions 3) The approaches and benefits of degassing 4) Solidification mechanisms 5) Habits and behavior of nonmetallic inclusions 6) Recrystallization phenomena 7) Slip and slip propagation 8) Dislocations 9) Discontinuous deformation 10) Microscopic and macroscopic segregation

Jan 1, 1970

By John D. Sullivan

MAJOR technical advances seldom occur in a single year, and this is especially true with aluminum and magnesium where marked improvements in metallurgical processes and products took place during the war years. Nevertheless, the light metals and alloys, particularly aluminum, are advancing in commercial importance and are finding their niche in industry. New applications during the year have resulted from a better over-all knowledge of properties, handling, etc., rather than from revolutionary new developments.

Jan 1, 1948

By John Birkinbine

(New Haven 'Meeting, February, 1909.) AWAKENED public interest in efforts to conserve natural resources will certainly be appreciated by the members of the American Institute of Mining Engineers, and a discussion upon conservation may well form a part of one of the Institute meetings, for the records of papers and discussions which appear in the 38 volumes of its Transactions are replete with evidence of effort's in this direction. Every process which reduces the fuel consumed or the power applied per unit of product; every utilization of waste material, or employment of that formerly rejected, to obtain something of value ; every feature of construction or operation which lessens the labor required or increases the output per employee, is an advance in the direction of true conservation. This may not appear from the records of late conferences or from published articles, in which the effort seems to be concentrated upon reducing the consumption and presenting to the people of the country estimates of exhaustion of natural resources. I rejoice in the awakening of public interest in a matter so important for the present and future welfare of our nation; I appreciate the possibility of much good following conferences of the Governors and delegates from various States and from national societies; and I recognize the interdependence, not only of different States, but of contiguous nations. In fact, the marvelous development of transportation by land and by water, and the decreasing rates at which commodities can be moved great distances, have in many cases practically obliterated geographical boundaries, and nearly every country on the globe can either market its product in other lands or draw upon them for raw or manufactured materials ; hence, conservation is an international subject.

Apr 1, 1909

By Thomas T. Read

AT this time of the year, engineering schools are releasing a group of young men who probably are, on the average, in much the same attitude of mind as a person arriving at the terminal station of a railway journey; namely, of having a general idea of his objective, but having to make a decision as to just where he is going and how best to get there. The man leaving the train can at first follow the crowd, but it soon breaks up, as one goes one way and one another, until he has to choose his own course. The recent graduate may do the equivalent of following the crowd by accepting the first position offered, but this only postpones a decision as to where he is going and how best to get there. So many young engineers ask for advice as to what to do that the following statement has been prepared as an attempt to make a general answer to such queries. The engineer taking his first job should realize two fundamental relations. The first is that in electing to be an engineer he has elected to be a hired man. A consulting engineer has more freedom than a man on a regular pay roll, but he is also a hired man; hired for briefer periods at a relatively high rate, but under the necessity of simultaneously doing his consulting work and developing new retainers. There is nothing derogatory in being a hired man (all doctors, lawyers and clergymen are hired men), but the tardy realization that he is one seems to give many an engineer a mental jolt that can be avoided if he accepts it from the beginning.

Jan 1, 1926

By J. V. Gluck

In the present paper," as in earlier publications, V1'2"1 the authors present experimentally obtained relations for the free energy of solution of oxygen in various metals as a function of temperature. The relations are linear and given in slope-intercept form. The authors give values for the "probable error" of the slope and intercept, citing Birge's method17 for obtaining these quantities. Birge discussed these methods as early as the period 1929-32.25726 In Ref. 25 the probable error is defined as "the numerical value which the true error is as likely to exceed as not", i.e., 50 pct probability. Ref. 26 is even more detailed and includes a lengthy discussion of the applicability of the Gaussian distribution to experimental data. However, the use of the "probable error" has come under some question. For example, Ezekiel'~ states that "the use of the probable error tends to make the results appear rather more accurate than the standard error". Moroney28 stated (in 1951) that "the term 'probable error' was used in former times to denote 0.67450 (50 pct confidence using the normal distribution)....the term, a poor one, is now very much obsolescent. It has been said that 'it is neither an error nor probable' ". Bennett and Franklin in 1954" in discussing statistical confidence levels mentioned that "the customary use of the 5 and 1 pct levels is not completely a matter of chance; these levels probably represent a balance between the desire to be correct and the desire to be specific. Also in most people's minds the borderline between something that could possibly happen and something that is not likely to happen is somewhere in this region. Certainly 5 or 1 pct confidence limits are to be preferred to limits such as the 'probable error' which has only a 50/50 chance of including the correct value." It may readily be seen that the 95 pct confidence level, which is given by 1.960 (assuming large sample size), thus corresponds to approximately three times the "probable error". Indeed, limits of one standard deviation correspond only to about 68 pct probability. Even if we triple the tolerances given by the authors in the equations of their Table 111, the deviations do not become excessive and would not detract from their excellent results. It could then be said with a high degree of confidence (95%) that the precision of the slope and intercept values is about *3-5 percent of their absolute levels rather than the 1-2 percent implied in Table 111. This is then compatible with an earlier suggestion of Gokcen~' of a probable accuracy of 5 pct in dissolved oxygen measurements by the technique employed. Alternatively, the authors could have

Jan 1, 1967

By John S. Alexander

By AIME AIME

OCTOBER will be western month for the Institute. With meetings at Spokane, Tulsa, Los Angeles, and San Francisco, and with a large number of American Institute of Mining Engineers members and their families in the party sailing out through the Golden Gate to Japan on the afternoon of the tenth, the major activities of the Institute will, for this month at least, be west of the Mississippi. Despite cancellations due to necessity, most of the officers of the Institute will be present and taking part in some one or more of the Western meetings. Prof. Robert S. Richards, our senior past-president, will attend both the Spokane and San Francisco meetings and then go to Japan. President Bradley will preside at the San Francisco meeting and then head the party going to Tokyo. At Tulsa and Los Angeles, the principal officers of the Petroleum Division will be present and active and at all the meetings, directors, ex-directors and -present and past officers will be on the job and keeping things moving.

Jan 1, 1929

By Robert L. Slobod

In much of the work reported in the literature on long cores. true connate water value, probably have not been obtained because of insufficient flow of 011 to attain equilibrium. A -.satisfactory method for establishing connate water in long cores has been developed in which oil flow is maintained until no additiona1 water is displaced. INTRODUCTION Long cores have been used by sev-erals investigators in an effort to evaluate the efficiency of oil recovery for various producing schemes. The effects of many variables such as rate of displacement. pressure drop, volume of displacing medium, gas-oil ratio, inter-facial tension, and others have been investigated, and the merits of gas drive have been compared with water drive. In the older experiments no connate water was used. but in the more recent stndies the philosophy of the experiment calls for a core containing oil and connate water (irreducible water) as the starting point of the experiment. The method generally used to establish this condition in long cores involves dynamic' displacement wherein one or more phases are forced through the core. flow being maintained at a constant rate or at a constant pressure until a steady state is reached wherein there is no change of saturation with time. It is one purpose of this paper to point out that in much of the work reported in the literature true connate water values probably have not been obtained. The reason for this failure is pointed out. and a method for obtaining more reliable connate water values on long cores is presented. It is impossible at this time to completely evaluate the effect on the conclusions in the earlier papers resulting from the failure to obtain true connate water in the long cores, but some data are presented which indicate that serious errors may he present in many cases. MATERIALS AND APPARATUS Cores cut front outcrop sandstones (Strawn. Torpedo, and Elgin sandstones) with permeabilities of the order of 300 md were used. The major experiments were made with a core 18-in. long and 2-in. in diameter. Cores of the same diameter but only 12-in. long were used in a few tests? and in some work a core I-in. in diameter and 11-in. long was used. These materials were all somewhat bentonitic. 'To reduce the effect of such constituents, one of the cores (Torpedo No. 10) on which the most work was performed was acid extracted at the start of the experiment. Brine containing 50,000 ppm chloride and naphtha (Stoddard's Solvent) were used as the water and oil phases, respectively. The core was mounted in a rubber sleeve which forms the inner lining of a brass cylinder. In this arrangement2 the rubber sleeve is forced against the core by applying pressure to water in the annular space between the rubber sleeve and the brass cylinder wall. The core is therefore sealed in rubber so that all fluids introduced at the input end of the core flow through the core. With this equipment the core may be easily removed for inspection and analysis. Also, other cores may be introduced for study with no extra time for preparation such as is required when plastic mounting is used. When pressure or conductivity measurements are desired at intermediate points along tile length of the core, the brass cylinder comprising the outer jacket of the core holder is cut into section, of the desired length. Each section is then made up as an individual unit with its own rubber sleeve (see Fig. 1). The individual units are then butted up against a ring of plastic or other insulating material which carries an electrical contact for resistivity measurements and an opening which can be used for the measurements of fluid pressures. The individual units are forced tightly against the plastic ring separators and held in place with several tie rods. Inlet and outlet end butts of the same diameter as the core and several inches in length are provided to control the introduction and withdrawal of fluids and to complete the arrangement for sealing the core within the rubber sleeve. Fluid flow is maintained either by applying pressure to the liquid confined in a reservoir or by the use of a gear pump. The latter is preferable where continuous flow at a moderate rate over a long time interval is desired since a small volume of liquid can be readily recirculated using filters to prevent plugging of the core. EXPERIMENTAL The oven-dried core is weighed and is then completely saturated with brine

Jan 1, 1950

"NAME…""Utah"" is derived from the name of the Indian tribe, variously spelled ""Yuta, “Ute"" ""Youta,"" ""Uta,"" ""Eutaw,"" and finally ""Utah."" It means ""in the tops of the mountains,"" or ""on the heights."" The state emblem is the ""Beehive,"" typical of industry. State nickname is ""Beehive State.""AREA…Utah is the tenth state in area. It contains 84,990 square miles, of which 2,806 miles are water. When admitted as a territory in 1850, Utah included all the area from the east line of California to the summit of the Rocky Mountains between the 37th and 42nd parallels, which embraced practically all of the present state of Nevada, all of western Colorado, part of Idaho and part of Wyoming, in addition to the present area of Utah.TOPOGRAPHY…Utah is generally mountainous, with several main ranges and also detached groups of mountains. The valleys are broad and level. The mean altitude of the state is 6,100 feet above sea level, which makes the state the third highest of the Union. The highest point in Utah is King's Peak (13,498) in the Uinta range. The lowest point is Beaverdam Creek (2,000) in Washington county.CLIMATE…The climate is diversified between mild temperate in the northern portion to semitropical in the southern portion. There are four distinct seasons. Snowfall is heavy at the greater altitudes and rare in the southern portion. Rainfall is moderate throughout the state. Extremes of heat and cold are unusual."

Jan 1, 1925

By Charles H. White

METHODS in colorimetry are based on the assumption that the intensity of the color of a definite volume of solution is directly proportional to the quantity of the color-producing substance' present. In the preparation and examination of colored solutions there are three ways in which the depth of color may be varied. These variables are; (1) the quantity of the coloring matter, (2) the quantity of the solvent, or the dilution, and (3) the thickness or depth of that portion of the solution examined. With these three variables as a basis, three general methods in colorimetry have been devised, all of which have been used in the determination of carbon in steel. In the first method, the quantity of the solution is kept the same for both the unknown steel and the standard, and the sections compared are of equal thickness, while the quantity of the standard is varied until the color obtained is of the same intensity as that produced by a definite quantity of the unknown steel. In laboratories where this method is used there is pre¬pared and kept for permanent use a series of solutions with varying amounts of the standard, representing the percentages of carbon from the lowest to the highest demanded in that laboratory. These standard solutions are kept in bottles, or test-tubes of equal diameter, and are arranged in series from the faintest to the most intense color, so that it is a simple matter to find the place of the unknown steel in the series, when the solution is of a definite volume and is contained in a tube of the same diameter as the standard tubes. In the second method, equal quantities of the standard and of the unknown steel are dissolved, the standard is diluted to a definite volume, and the solution of the unknown steel is di-

Sep 1, 1906

By Edwin Ludlow

T HE OPEN FORUM on this subject called by Mr. Hoover at the recent meeting of the Institute' brought out a large number of very able papers, and a very full discussion of all the problems involved. The criticisms of the bituminous industry were: 1. That it was over-developed with the possible output nearly 50 per cent. in excess of the present requirements; that during the summer there were plenty of cars and no orders, and during the winter there were plenty of orders but no cars. 2. That the mines were not properly developed from an engineering standpoint, and that the recovery of the coal varies from 50 per cent. to 95 per cent. 3. That this industry, employing over 600,000 men, could, if running full time, release 100,000 men for other work. 4. That the studies made by the engineers of the Fuel Administration showed that the cost of production increased with a loss of time and that with a 50 per cent. operation the increase in cost was about 40 per cent.

Jan 1, 1920

By A. P. Cohen, D. W. Fuerstenau

Methods of accounting for the feed size in analyzing the size distribution shift during comminution have been discussed in a number of papers.1,2,3 Based on experiments which charles2 performed with single Pyrex specimens, Schuhmann4 pointed out that the size modulus of an assembly of particles should be determined by the energy expended per unit volume (or mass), independent of the size of particle being comminuted. In this same paper, Schuhmann derived the Charles energy-size reduction relationship by considering that complex comminution operations can be considered to be the summation of many individual comminution events, each of which must be governed by Were 6wi is the mass of a particle receiving the impact, 6Ei is the energy delivered to the particle, ki is the size modulus of the product resulting from the impact, a is the distribution modulus of the assembly of particles, and A is a constant. Recent experiments on the compression loading of Pyrex spheres ranging in size from 1/8 to l-in. diam have shown that the size modulus of the fragments is determined by the strain energy at fracture per unit mass, independent of sphere diameter.' The objective of the present investigation has been to determine experimentally whether the size distribution of the product from such a complex comminution process as rod milling is determined only by the energy expended per unit mass independent of feed size. Samples of each Tyler sieve fraction ranging from 4x6 to 48x65 mesh were prepared from crushed Brazilian quartz crystals. One kilogram of each fraction was ground at 60 pct solids in an 8x9 1/4-in. mill containing 17.5 kg of rods (26 rods, 5/8-in.; 10 rods, 3/4-in.; and 5 rods, 7/8-in. diam). In each test, the mill was run at 77 rpm for 15 min. Size distributions were determined by a wet-dry sieving technique. Table I presents the size distribution of the products obtained by grinding each of the size fractions. Because the size distributions are so nearly alike, they are plotted in Fig. 1 by shifting each size distribution for the different feed sizes one screen fraction to the right. Thus, the lowest point in each size distribution represents 400 mesh and each of the other sieve sizes must be shifted accordingly. A single regression line was calculated by combining the data for the six tests, excluding the coarsest feed and the two finest feed fractions. 6 This regression line, which is given by (Y \0.88 where y is the cumulative percentage of material

Jan 1, 1962