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By J. C. Bayles

Jan 1, 1885

By Robert E. Sorenson

EXPLORATION for deep-seated orebodies in the Silver Belt area of the Coeur d'Alene mining district is complicated by meager surface expressions of diagnostic criteria, lack of knowledge of the significance of specific alteration phenomena, and the great expense involved in the exploration for ore shoots, the tops of which often occur near sea level elevation or below and as much as 4000 ft or more below the surface. Except for the early studies of Ransome and Calkins in 1903 and 1904,' little geological work was done in the Coeur d'Alene district for many years, and it is only during the last 15 to 20 years that complete and careful geological mapping has been applied to most of the mines in the area. Much early information, which now would prove invaluable, is lost in hundreds of miles of caved and inaccessible mine openings not mapped by mining geologists. In more recent years mining geology has become a tool of greater use in the district, and some measurable progress is being made in the accumulation of observations that are adding gradually to the knowledge of ore deposits in the district. The recognition of alteration phenomena and related features by Hoyt S. Gale3 in 1935, followed by the work of Shenon and McConnel in 1936-37,4 changed many of the concepts formerly held and opened the way for more critical study and mapping of alteration effects. Mapping of these effects has been in progress for several years but no well-organized, careful, and complete laboratory study of the alteration has been made by mining companies or by government agencies. Recently, Thomas Mitcham of Columbia University has been occupied in the collection and study of specimens carefully selected from several producing mines in the Silver Belt as well as from several prospects exhibiting alteration effects. Mr. Mitcham and the writer have discussed some of the preliminary results of his investigations, which indicate that definite and interesting material is forthcoming from his studies. Work of this kind, aided by careful observation by district geologists, should advance the knowledge of the environment of Silver Belt ore shoots and establish additional criteria for recognizing meager shallow expressions of deep-lying orebodies. Structural details in the Silver Belt area are extremely difficult to decipher on the surface because the area is almost completely covered by a deep mantle of surface debris and soil. A dense growth of small trees and buck brush adds to a geologist's difficulties. Often large areas reveal only scattered small outcrops with great intervening areas where the underlying formations must be deduced from small altered rock fragments. Some considerable success in obtaining surface information has come from bulldozer roads and cuts in selected areas. As this type of work receives more attention, knowledge of the surface expressions of formations, alterations, faulting, and veining is expanding and giving more reliable information to guide deeper development. Lack of diagnostic marker beds in the district contributes to a geologist's difficulties in determining fault displacements. In the Silver Belt, known commercally important sulphide orebodies commonly are associated with siderite and quartz gangue. Some of the veins at shallow horizons above productive ore shoots are composed of quartz with light-colored carbonate minerals such as calcite, ferrocalcite, ferrodolomite, ankerite, and carbonates with variable amounts of manganese. The relation of these carbonates to commercial orebodies is a problem offering possibilities for research. Shallow exposures of veins composed of quartz and the light-colored carbonates, often with some associated barite, grade into quartz and siderite veins at deeper horizons. The vertical range of these carbonates has been partially established for some veins, but no reliable method has been devised for predicting where the change in a vein may take place. Careful observation and analysis of carbonates may make it possible to predict more closely where the change to siderite may be expected. In 1926 Shannon5 pointed out some of the characteristics of the carbonate veins of the district and included a few chemical analyses. Some of the Silver Belt ore shoots have small commercial outcrops, and very shallow development of some properties has led to the opening of small ore shoots." Several small ore shoots developed at shallow depths have not been explored at deep horizons, and some important ore shoots with no commercially significant exposures at shallow horizons have been developed. The greatest problem of the mining geologist working in the Silver Belt area is to find the all-important link between the very meager shallow expressions of mineralization and the rich ore shoots that may be found below. To develop criteria for use in the recognition of the weak upper expression of ore shoots, the experience of past development programs must be relied upon heavily. The investment of more than a million dollars in the exploration for such ore shoots requires some reliable criteria if these ore shoots are to be found. Management needs some assurance that the risk involved is justified by well-developed and acceptable geological inference. The richness of some of the ore shoots found thus far has contributed greatly to the justification for a bold approach, but many negative results of blind exploration programs would lead eventually to extreme caution on the part of management. Fortunately, recent experiences of development programs have been quite successful. It is hoped that added knowledge. of the environment of Silver Belt ore shoots will contribute greatly to the sureness of approach toward their development. The Coeur d'Alene mining district is located in the panhandle of Idaho in Shoshone County. The population of the county is either employed in the

Jan 1, 1952

By C. Schlumberger, M. Schlumberger

In order to explore electrically a terrain composed of a succession of horizontal beds, a current of known intensity i is caused to flow between two grounds A and B, and the resultant drop of potential , caused by the resistance of the earth, is measured between two given points in the soil, M and N. In practice it is convenient to choose the two points M and N so that they lie on the line AB and their midpoint coincides with the middle 0, of that line, although this is not imperative. When the lengths L and I of the two lines AB and MN are varied, equations are obtained which may be solved for the resistivity p of the subsoil at various depths. Recall briefly that the formula 4 x l gives the average resistivity, in the horizontal direction, of a layer of earth which extends to a depth1 about equal to L/4. This elementary concept is adequate for numerous practical applications. Nevertheless, it must be said that, in many cases, a rigorous mathematical analysis may be made, provided it is always a question of homogeneous, superposed horizontal beds. The authors expect to publish, later on, appropriate methods of calculation for some specific cases.

Jan 1, 1932

In the Bowen Basin of central Queensland, coal production has gone from virtually nothing in 1961 to more than 24 million tons today4ut there's a cloud over this success.

Jan 1, 1977

By W. E. Wrather

DURING the war the mineral industry, and metal mining in particular, extended itself more than any other to attain the limit of its productive capacity. Likewise, probably no other industry went quite so far toward jeop¬ardizing its own economic future through depletion of material reserves. Once we looked to Europe for most of the manufactured goods we needed. Our own limited mineral requirements were easily supplied from mines near the Eastern seaboard. With expansion and industrialization, our mineral needs increased in proportion, and the centers of mining activity moved westward to Michigan, Wisconsin, Minnesota, and the Tri-State district, where seemingly inexhaustible high-grade deposits of iron, copper, lead, and zinc ores were opened and rapidly developed.

Jan 1, 1946

By David T. Day

IN 1897 I published a proposed explanation t for the variation in color and specific gravity of Pennsylvania oils. A resume of this subject was also presented at the First International Petroleum Congress, in Paris, in 1900. Since that time much experimental work bearing upon this explanation has been carried on by myself, in the United States Geological Survey, and under my direction, by Dr. J. Elliott Gilpin, Marshall P. Cram, and 0. E. Bransky, at the Johns Hopkins University. The experimental results thus accumulated seem to throw considerable additional light upon the variations in color and specific gravity of petroleum, as found in different parts of the world, and also upon the variations in chemical composition. Therefore, it seems as if a, summary of the evidence thus obtained might be of value to those members of the Institute who are interested in the examination of oil-fields. The summary is here presented for that purpose. The phenomenon has often been observed in many oil-fields that oils of different color, specific gravity, and chemical composition may be found within short distances of each other. A conspicuous example of this is the occurrence at Jennings, Welsh, and Anse la Butte, La., of petroleum chemically somewhat similar to Russian petroleum; that is, characterized by the presence of naphthenes. Another characteristic is the presence of considerable percentages of asphaltic compounds, sufficient in quantity to disguise the presence of solid paraffin wax, and perhaps also to render that paraffin wax more soluble * Published by permission of the Director of the United States Geological Survey. 1 Proceedings of the American Philosophical Society of Philadelphia, vol. xxxvi., No. 154, pp. 112 to 115 (January, 1897).

Jun 1, 1910

By H. O. Hofman

(Canal Zone Meeting, November, 19]0.) THE sudden decease, April 1, 1910, in Chicago, of Dr. Franklin R. Carpenter was a shock to his- many friends. He died in his sixty-second year, of heart paralysis. To most fellow-members of the Institute who have followed the progress of the. last twenty-five years in the mining and treatment of non-ferrous ores, the work of Dr. Carpenter in that line is familiar ; but very few, even of those who knew him well in the later years, are acquainted with his earlier struggles to satisfy an inborn hunger for knowledge. The story of his life resembles that of the pioneer who opens up new country; overcoming hardships with indomitable courage, meeting doubts and difficulties with an alert and open mind, and exercising in the face of reverses an unconquerable perseverance. It seems appropriate to place on record in the Transactions a brief outline of the life and work of this eminent engineer. During the past 15 years of his life Dr. Carpenter was much interested in genealogy. In the pursuit of this study as an avocation, he traced his own ancestry to the time when ?Hugh," called "le Charpentier" on account of the dexterity with which he had swung his battle-axe as a crusader, settled in Sussex on lands received from William the Conqueror. The Carpenters came to this country with William Penn. A prominent member of the family was Joshua Carpenter, the founder of Christ Church, Philadelphia. Dr. Carpenter's branch of -the family moved from Pennsylvania into that part of Virginia which is now West Virginia, where his grandfather settled in Harrison county, while the grand-uncle went further west, and built the first iron-furnace at Hanging Rock, Lawrence county, Ohio. In fact, since early times, the Carpenters appear to have been iron-masters. Franklin R.. Carpenter was born, Nov. 5, 1848, in Parkers-

Aug 1, 1910

By A. L. Bailey, B. A. Landry

W. W. ANDERSON and G. E. KELLER*—We want to compliment the authors on this very thorough paper. It gives information which the coal industry has needed for some time. We hope that the additional information which the authors are collecting will he available shortly. The mixing and riffling procedure that was followed for experimental purposes is obviously not practical in routine float-and-sink testing because of the particle size degradation which would result in handling the sample so many times. It is important to obtain our tloat-and-sink fractions with a minimum amount of handling of material. A statement is made in the paper (p. 80) that "the variable most likely to affect the size of sample required to meet a given preassigned accuracy would be the state or degree of mixing of the coal." We agree that this is a large factor, but do not believe it is the most important factor. Our own opinion is that the most important single factor governing the total gross weight of sample that must be collected is the percentage of the weight of material in the smallest fraction that results from the screening and float-and-\ink operations. In other words, size of sample is governed by the total number of fractionations that must he made, and the distribution of material within the fractions. We can imagine a coal with perfect mixing, but with such a small amount of material in some float-and-sink fraction in one of the coarse sizes that a much larger sample would have to be taken than would be the case with very poorly mixed material, but with a large percentage of coarse material more evenly distributed in all float-and-sink fractions. Our own observation of many float-and-sink tests that we have run in our own organization on many types of coal is that the size of sample that must be used on fine size float and sink is governed more by the requirements for weight of material to be used for analysis in the laboratory than by weight of material necessary to obtain accurate float and sink percentage of weight values. In other words, it is our opinion that very small samples can be used for float-and-sink fractionation in the fine sizes, but that accurate analysis of the fractions will depend on a larger weight of sample being pulverized for the laboratory than is necessary to establish the float-and-sink distribution with respect to weight. A. L. BAILEY and B. A. LANDRY (authors' reply)—The authors thank Messrs. Anderson and Keller for their comments based on long experience. It is agreed that the involved mixing and riming technique used may be disadvantageous from the standpoint of degradation. Fortunately, the paper does point out that the extended riming was unrewarding in causing further mixing. Two large unknowns remain, however: (1) how much of the mixing from the presumed highly unmixed state in the bed was achieved toward the random state during blasting, loading, transportation, screening, and further transportation to the point where the gross sample was taken, and (2) how much of the mixing took place during the preparation described preceding riming. As has been pointed out by one of the authors.6 the degree of mixing has a very large effect on the size of sample required and there are still too few experimental data to show at what stage of coal handling most of the mixing occurs. The discussion states that the weight of material in a screened fraction, or in a float-and-sink fraction, is more important than the mixing factor. We do not believe that these factors are comparable in this instance inasmuch as our purpose was to give minimum sampling requirements to achieve a preassigned accuracy in the percentages of float, middlings, or sink, and nothing more. The gross sample had already been screened and no further division by screening was made or contemplated; also, it was not intended that the middlings and sink fractions would necessarily be adequate for percentage ash or other determination. In other words, the sample obtained by the method outlined is not intended for washability studies but only for preparation plant control. Further experimental work has been done, since the paper was prepared, to investigate the effect of increasingly larger top and bottom sizes on the variability of float, etc., of a double-screened coal from Western Pennsylvania. Results will be published and eventually attention is to be given to the preparation of sampling specifications. E. H. M. BADGER*—I should like the authors to explain more fully the fundamental assumptions on which their Eq 4 is based. The equation is of the form s2 = p(l - p) which is the usual expression for the (standard deviation)2 when the chance of finding a particular kind of particle in the sample is proportional to the number fraetion, p. But instead of the number fraction, the authors have used the weight fraction, WF/W. The chance of finding a particular kind of particle in the sample can only be proportional to the weight fraction, if the average ?eig?ts of all kinds of particles, that is, float, midlings, or sink, are the same. Surely a much more justifiable assumption would be that the average volumes of the particles are the same, and, if this is so, Eq 4 would not be true. This may be demonstrated as follows: Let be the weight fraction of float, middlings, or sink, dl the density of this fraction, and d2 the density of the rest of the coal. Then assuming that the average volumes of the pieces in the three classes are the same, the number fraction, p, is given by ? P = d1/l-?/d2 + ?/d1 = ?d2/d1 + ?(d2-d1) The weight fraction, w, in terms of p is given by ? = pd1/(l-p)d2 + pd1 = pd1/d2 + p(d1-d2) _____ [61

Jan 1, 1950

By C. B. Foster, S. I. Freedman, E. M. Jamgochian

Coal-oil mixture (COM) combustion technology is regarded by the US Department of Energy (DOE) as near term and Potentially applicable to existing utility and industrial steam generators and for injection into blast furnaces. From work done previously, it has been established that COM can be burned in existing boilers and blast furnaces. Therefore, the issues being addressed by the current DOE program are: (1) determination of best available technology to achieve environmentally acceptable long-term reliable operation and (2) determination of applications for which COM can be utilized economically. Some of the technological options have begun to be determined by projects already under way. However, many projects are still in the early stages of development.

Jan 1, 1980

By John B. Hastings

THE occurrence of such a large amount of gold in the Hartsel granite, even though the surmised existence of similar areas is not new, brings freshly to mind the pegmatite type of magmatic differentiation lately brought again to attention by occurrences at Silver Peak, Nev., described by Spurr; and in Alaska, described by both Spurr and Brooks. In both localities graunitic rocks or dikes are thought to pass into metalliferous quartz-veins. An interesting association in this connection is the occurrence of diamonds in residual pegmatitic clay of San Juao de Chapado, Brazil, described by Derby :1 (P. 142) "Bodies of pegmatite are quite common in the older rocks of Brazil, both in the. diamond regions and elsewhere, occurring not only in the gneiss and granite, but in the schistose series as well. Those that have been examined are dike-like in their mode of occurrence and granitic in composition." (P. 143) "The question of the eruptive or secretionary origin of pegmatites has long been a subject of discussion among geologists. . . . The recent studies . . . seem to have clearly established that most if not all of them are essentially eruptive masses, though possibly modified in some way by aqueous agencies. Even before becoming acquainted with the literature of the subject this view had seemed to me to be the only acceptable one as regards the typical pegmatites of Brazil." What is pegmatite ? J. F. Kemp says ". . . veins or dikes-it is an open question which is the more correct term-are met formed of very coarsely crystalline aggregates of the same minerals that constitute granite. These are called pegmatite and in them is the home of graphic granite, the curious intergrowth of quartz and feldspar, such that a cross fracture of the blades of quartz suggests cuneiform characters. . . . In regard to the larger veins or dikes it seems improbable that true igneous fusion could have afforded such coarsely crystalline aggregates, and so we are forced to assume such abundance of steam and other vapors, i.e, mineralizers, as to almost, if not quite, imply solution."

Jan 5, 1908

By Benjamin C. Craft

As predicted, during 1937 South Louisiana witnessed one of the most active drilling campaigns in the history of the area, resulting in the discovery .of 14 new fields. The economic importance of 10,000-ft. production was far-reaching and the objective depths placed on some wildcats was 12,000 feet. Most of the important discoveries and deep tests were in the delta area between the Atchafalaya and Mississippi Rivers, where the upper Miocene sands were found productive between 10,000 and 11,000 ft. The casing program on these wells usually called for a protection string of 95/8-in. casing at approximately 9500 ft. Drilling barges with the heaviest equipment were used where water transportation was available. The oil production for South Louisiana during 1937 was 62,147,690 bbl., as compared with 51,968,727 bbl. during 1936, an increase of 19.5 per cent. There were 281 oil and gas wells and 172 dry holes completed during 1937 as compared with 262 oil and gas wells and 135 dry holes during the previous period. New Fields Gibson.—The first discovery for the year was in the Gibson area, where Shell Petroleum Corporation's Realty Operators No. 1, sec. 18, 17 S., 15 E., Terrebonne Parish, was completed flowing 780 bbl. of 38° A.P.I. oil daily through a 14/64-in. choke with a tubing pressure of 1700 lb. Production is from upper Miocene sand found from 9461 to 9483 feet. Abbevil1e.—The discovery well for the Abbeville field was Continental Oil Company's Hebert No. 1, sec. 20, 12 S., 3 E., Vermilion Parish, completed flowing 50 bbl. of distillate and 2 million cubic feet of gas through a 3/16-in. choke with a tubing pressure of 2550 lb. The well was plugged back from 12,216 ft. in the Chickisawhay, and is producing through perforations from upper Miocene sand found from 7668 to 7682 ft. Later in the year, the same operators completed Brookshire No. 1, sec. 66, 12 S., 3 E., flowing 366 bbl. of 42° A.P.I. oil per day through a 3/16-in. choke with a tubing pressure of 1800 lb. This well was com-

Jan 1, 1938

By Joseph Gurland

EVERAL carbide-cobalt compositions were pre-^-5 pared for the purpose of determining the transverse rupture strength of various carbide-binder systems. The binder content was held at 10 and 37 volume pct Co, so as to be representative of low and high bjnder compositions. The carbides used, WC, Tic, TaC, CbC, VC and ZrC, were selected on the basis of availability, knowledge of their properties, and small solid solubilities in the binder metal at room temperature. The methods of preparation and carbon analysis of the carbides are summarized in Table I. The carbides with cobalt added were ball milled, pressed, and sintered. vacuum sintering was used throughout, except for the WC-Cs alloys, which were sintered in hydrogen. The sintering temperatures ranged from 2500" to 2750°F for the low binder alloys and from 2300" to 2550°F for the high binder alloys. Compositions and properties of the sintered com- pacts are presented in Table 11. For the transverse rupture strength, the average and range of the five best samples of each alloy are listed. Discrepancies between the actual and theoretical densities are attributed to carbon deficiencies in some samples. The theoretical densities were calculated by assuming mixtures of carbides of stoichiometric compositions and cobalt. Representative microstructures are shown in Figs. 1 to 6. The porosity was A-2 or better' in all alloys except those with ZrC. A grain size of about 3 p was

Jan 1, 1958

By E. S. Grumell

THE correct sampling of coal and coke is becoming important to an ever increasing number of producers and consumers. This, therefore, may be an opportune moment to examine where we stand with regard to existing and proposed methods. In this paper an attempt will be made to review, as briefly as possible, some of the considerable amount of painstaking research which has been done in the last 10 years, and which has unquestionably led to a much better understanding of the subject. In so doing we shall try, on the one hand, to make clear where substantial progress has been made, and on the other hand, to draw attention to points that require further investigation. The paper is divided into sections in order to emphasize the major divisions of the subject; further, in order to retain this emphasis, detailed consideration of some of the points has been relegated to appendixes. No attempt has been made to give a complete survey of the literature, as this has already been done by L. A. Bushell.2 The following abbrevia-tions will be used: A.E., average error; P.E., probable error; S.W.R., size-weight ratio; B.S.I., British Standards Institution.

Jan 1, 1939

By Claude P. Heiner

While the title of this paper embraces the entire West Coast, the author, in the interest of simplification. has confined the discussion to California-particularly the central section. California's population has, risen 45 pct since 1940. Its electric requirements have also increased, not only because of the growth in industry and population but also because of the widespread tendency of all types of electric consumers to use more electricity than ever before. The growth of California's electric utilities is shown by published data covering operations, of three of its large systems and is given in Table 1.

Jan 1, 1949

By Donald B. Gillies

TO me a graduating class of engineers constitutes one ' of the finest inspirations I can imagine. You have finished your four- year scholastic career and are starting out in competition with thou- sands of other young men from other universities to make your mark. Be- cause of your training you men are such an essential part of our present- day civilization that a great weight of responsibility rests on your shoulders, especially at this time, for this is an engineering era. Today, it is the engineer who dreams the dreams and makes our civilization better. It's the engineer who carries those dreams into realization and fulfillment. No matter where we go in business and industry, we find- engineers in key positions, charged with great responsibilities.

Jan 1, 1939

Discussions of the paper of Mr. Gayley read by title at the Lake Superior hieeting, but first presented at the New York meeting of the Iron and Steel Institute, October, 1904 (see p. 746). With the exception of Mr. Pourcel's discussion (p. 1038), these papers are here published under a mutual agreement between the Councils of the two Institutes, and will also be found, with others, in the Journal of the Iron and Steel In-slitute for the pear 1904, Mr. E. Windsor Richards, Past-President,' said that in 1799 Mr. Dawson, of Low Moor, read a paper before a scientific society in York pointing out the great diff'erence in the moisture of the air going into the blast-furnace in the hot months of the year and in the winter months. A cold blast-furnace was a very sensitive instrument, and showed this very clearly, for in June, July and August the furnace did not drive so well; it did not make the quality of iron and required more fuel; so that Mr. Gayley was on the right road to effect an enormous improvement in this direction. He considered that Mr. Gayley was on the way to great success, and hoped that the apparatus would not be a very expensive one. He supposed it mas too early for Mr. Gayley to let them know what the saviug was

Jan 1, 1905

By RUSSELL C. FLEMING

GILSONITE is a brilliant black, tarry-like bitumen, classed technically with glance pitch and graharnite as an asphaltite. As found it is brittle, breaking much like ice, and has a conchoidal fracture. Purest forms are used in the manufacture of paints, varnishes, electrical irisulatiorl, and inks for rotogravure; molded articles such as switch handles, telephone mouthpieces, and but- tons are made from the intermediate grades, and the poorer grades are used for the saturation of felt. According to the U. S. Bureau of Mines figures, production grew from about 4000 tons mined in 1904 to 55,000 tons in 1929. This asphaltic substance is found only in the Uintah basin in northeastern Utah, in veins over a wide area. Veins in the vicinity of Fort nuchesne were first discovered about 18G2, on what was then the Uintah Indian reservation, and the vein matter was originally called Uintaite because of that fact, In the early days, S. H. Gilson. of Salt Lake City, was so persistent and zealous in his efforts to develop the deposits and find a market that the name gilsonite was given to the material. Later, the wider and more renowned wins near Wayson and Dragon, in extreme eastern Utah, became the main supply.

Jan 1, 1932

By E. E. AGGER, Arthur Notman

THE proposal has been made in a bill introduced into Congress at the last session by Representative Jones of Michigan that an import duty of 6 c. per lb. shall be placed on copper. This action is urged after eighty years of prosperity for the industry in this country; during most of which copper has been on the free list, and during all of which a tariff would have been without real effect. To comprehend the general situation upon which this action would be imposed, we must refer to the past history of the industry and its trends at the present time. The following table supplies us with a picture of the physical growth of the industry in this country and its relation to that of the world as a whole down to Jan. 1, 1921:

Jan 1, 1925

Oct. 8-13, 1917 The St. Louis Meeting of the Institute will be held Oct. 8-13, 1.917. Various committees are being organized to perfect the arrangements for the meeting. A number of excellent technical papers have already been secured end an attractive series of excursions has been outlined. The following is the outline plan for the meeting. More detailed announcements will be made as the plans mature. MONDAY, OCT. 8 Morning: Registration and Technical Session. Afternoon: Boat ride to Herculaneum, Mo., to visit smelter. and Evening: Dinner on boat and social evening.

Jan 4, 1917

By L. E. Shiffman

W. J. Parton—Those operators faced with the problem of treating fine coal whether in bituminous or anthracite will find this paper most timely. I would like to take this opportunity of discussing Mr. Schiffman's paper and at the same time express certain views relating to our Tamaqua plant. I would like to ask the author what type of impeller and diffuser is used in the Denver cells? Screen analysis of products from individual cells indicate that coarser material resists flotation and only floats after greater retention time in the last few cells. Also, the need for a scavenger screen to reclaim non-floated coal particles further stresses this point. I have always felt that more efficient means of cleaning coal between 10-mesh and 28-mesh existed than flotation. Reagent and power costs are high for the flotation process. When floating +28-mesh particles, cell capacity is lowered and some of the particles are lost with the refuse. The Tamaqua plant of the Lehigh Navigation Coal Co. floats —28-mesh coal and capacity of recoverable coal is 40 tph for 1800 cu ft of Denver cells; or 0.05 tons per cu ft of cell. At Kimberly 7.75 tph for 600 cu ft of cell gives 0.013 ton per cu ft of cell. At Bessie 14 tph for 800 cu ft of cell gives 0.017 tons per cu ft of cell. It would be appreciated if the author would comment on what he feels is the upper size limit of particle to attain most efficient utilization of the flotation process. The dewatering screw is a very interesting development since it offers a simple way to prepare coal sludge for more complete clewatering by drainage or mechanical dewatering on screen or filters. In other words it could be used to accomplish the same thing as a thickener tank. I would appreciate having the author's comment on how he thinks such a screw dewaterer would work on a froth.* The process as used in floating coal at the Bessie and Kimberly plants may be referred to as more of a bulk oil float in contrast to a froth flotation process. Experiments on increasing capacity of cells is most interesting since we are going through such an experi- mental period at the present time. Recently a double overflow was installed on our No. 30 Denver cells. So far results are not conclusive. In reviewing this paper the following comments are made pertaining to investigation of methods for increasing capacity: Supercharging: Supercharged air in matte flotation or for that matter the use of the normal amount of air drawn in by the impeller would in all probability cause such an aeration in the cell as to destroy the buoyant effect given to the coal particles by the excessive amount of kerosine used. In other words, air creates an agitation zone throughout the cell, creating a boiling and thereby giving a lower recovery in the cell. It would be interesting to know whether the 7 pct increase in recovery was with no air being admitted to the stand pipe. Changing Impeller Speed: The speed of a receded disc impeller for a No. 30 cell as recommended by the Denver Equipment Co. is, I believe, approximately 250 rpm. At this speed and using supercharged air in excess of 8-oz pressure, we have observed a boiling action in the cells. In our flotation we endeavor to obtain some degree of froth flotation using pine oil as a frother. The boiling action as caused by increasing the amount of air added to the cells is detrimental to recovery in froth flotation. It is our belief that to obtain increased recovery from a cell in froth flotation, additional air must be introduced but at the same time this air must be dispersed throughout the pulp in the form of small bubbles and this can only be done by increasing the speed of the impeller. Therefore, if Mr. Schiffman decreased the speed of the No. 30 impellers and at the same time continued to use supercharged air, the boiling action may have been increased because larger bubbles developed. The lower recovery as reported could be due to this factor. Decreasing the impeller speed will definitely decrease the power consumed but may have other disadvantages. First, we believe it will permit "sanding" in the cell and this in our opinion will increase the wear on the impeller and diffuser, especially so, if there is pyrite and/or sand present in the feed. "Sanding" in the cell when air is used, as in froth flotation, will effect the dispersion of this air and cause boiling.

Jan 1, 1951