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By R. Michael Craig

Mr. Juvkam-Wold's article is a timely and much needed presentation of the method of depressurization to reduce ground- water inflow into mine shafts. The article is very informative and discusses the effects of depressurization upon shaft inflows adequately. However, the article omits a discussion of another important benefit of depressurization: the reduction of potential for artesian burst or, as it is also called, floor heave. Confined aquifer systems (artesian aquifers) can contain water under several hundred pounds per square inch (psi) of pressure. For example, water levels at elevations of 455 m (1500 ft) or more above the top of the Westwater Canyon member of

Jan 1, 1984

By David A. Wracher

A geologist may produce for himself a surprisingly accurate photo base map and stereo coverage at low cost without the use of expensive equipment and complex photogrammetry. If care is taken and the program well thought out, good results can be expected. The only equipment necessary in this method is a small format (small negative size) camera, a few rolls of film and the appropriate filters. A light aircraft, with an opening in the bottom, is preferable so that the pictures can be taken vertically and from inside - the aircraft. The method will produce high resolution prints at large scales in the range of 1: 1200 to 1:7200.

Jan 11, 1973

Reducing Fusion: The impure or low grade uranium concentrate is mixed with a formulated flux of sodium carbonate, salt, and sawdust or fuel oil and heated, while being stirred, to about 950°C. This reduces the uranium to the black, water insoluble uranium dioxide and with the exception of nonamphoteric metals forms water soluble sodium salts of the vanadium, alumina, silica, phosphates, and other constituents of the cake. The cooled melt is then water leached, leaving a residue of black insoluble uranium dioxide. "Green Sludge" Digestion and Liquor Purification: The green sludge is redissolved in acid, and by selective precipitation involving pH adjustments and a final neutralization

Jun 1, 1956

By J. P. Hammond, C. J. McHargue

The wire textures for cold rolled and recrystallized iodide titanium and the sheet textures for this material produced by cold and hot rolling, and recrystallization at a series of temperatures were determined. &apos;The effect of the a + ß transformation on the sheet texture was noted. UNTIL recently it was believed that all hexagonal close-packed metals deformed by slip on the basal plane, (0001), and that rolling should tend to rotate this slip plane into the plane of the rolled sheet. The pole figures of cold rolled magnesium&apos; are satisfactorily explained on this basis. There is a tendency for the <1120> directions to align parallel to the rolling direction, and the principal scatter is in the rolling direction. Zinc% as a rolling texture in which the hexagonal axis is inclined 20" to 25" toward the rolling direction. Twinning is believed to account for the moving of the basal plane away from parallelism with the rolling plane. The texture of beryllium3 places the basal plane parallel to the rolling plane with the [1010] direction parallel to the rolling direction, and the scatter from this orientation is primarily in the transverse direction. Cold rolled textures reported for zirconium&apos; and titanium5 how the [1010] directions to lie parallel to the rolling direction and the (0001) plane tilted by approximately 25" to 30" to the rolling plane in the transverse direction. Rosi has recently reported that the mechanisms for deformation in titanium are distinctly different from those commonly reported for hexagonal close-packed metals. The principal slip plane is the prismatic plane, {1010), with some slip also occurring on the pyramidal planes, (1011). However, there is no evidence for basal slip. The slip direction is reported to be the close-packed digonal axis, [1120]. In addition to the twin plane commonly reported for metals of this class, {1012), Rosi found the twin planes (1122) and {1121), with the dominant twin plane being (1121). Information regarding the recrystallization and hot rolling textures of hexagonal close-packed metals is limited. Barrett and Smigelskas report that rolling beryllium at temperatures up to 800°C and recrystallization at 700°C produce textures not differing from the cold rolled sheet texture.3 McGeary and Lustman find that hot rolling at 850°C produces the same basic texture in zirconium as rolling at room temperature.&apos; These investigators also report that the texture for sheet zirconium recrystallized at 650 °C differs from the cold rolled orientation inasmuch as the [1120] direction, instead of the [1010] direction, is parallel to the rolling direction. In the case of titanium, it is not possible to deduce which direction is preferred in the recrystallized state from the pole figures presented by Clark." The purpose of this paper is to report an extensive investigation of the preferred orientations in iodide titanium. Since the deformation mechanisms for titanium are different from those commonly given for hexagonal close-packed metals, it is not surprising to find distinct differences between the textures of titanium and other metals of this class. Materials and Methods This investigation was carried out on iodide titanium obtained from the New Jersey Zinc Co. with an analysis as follows: N2, 0.002 pct; Mn, 0.004; Fe, 0.0065; A1, 0.0065; Pb, 0.0025; Cu, 0.01; Sn, 0.002; and Ti, remainder. The crystallities of titanium were broken from the as-deposited bar and melted to form 20 g buttons on a water-cooled copper block in a vacuum arc-furnace. Hardness tests conducted on the material before and after melting differed by only two or three Vickers Pyramid Numbers, indicating no or insignificant contamination. The buttons were hot forged, ground, and etched to sizes and shapes suitable for the rolling schedule, and vacuum annealed at 1300°F. Specimens for determination of the wire textures were reduced 91 pct in diameter to 0.027 in. in 24 steps using grooved rolls. In order for the orientation of the central region to be studied, portions of these wires were electrolytically reduced to a diameter of 0.005 in. using the procedure described by Sutcliffe and Reynolds.&apos; The sheet textures were determined on titanium cold rolled 97 pct to a thickness of 0.005 in. A reduction of approximately 10 pct per pass was used, and the rolling direction was changed 180" after each pass. Specimens used for determination of the recrystallized textures were annealed in evacuated quartz tubes at 1000°, 1300°, and 1500°F. The grain size of the 1000°F specimen was sufficiently small to give satisfactory X-ray patterns with the specimen stationary. However, it was necessary to scan the surface of the other recrystallized specimens. The microstructure of each annealed specimen was that of a recrystallized material. The diffraction rings all showed the break-up into spots typical of recrystallized structures.

Jan 1, 1954

By Charles E. Wait

IN order to secure cupels uniform in size, density, etc., I have arranged a machine which has proved quite satisfactory, and is so simple and inexpensive as to be within the reach of nearly everyone. It has been in operation here about four years, and with it all cupels used in the assay department of the School of Mines have been made. As shown in the accompanying figure, it consists of a common letter-press, the movable platen of which has been removed. In place of the plate, there is attached to the screw a plunger, which turns with the screw, moving up and down, and making the depression in the cupel. The ring holding the bone-ash is held in place directly underneath the plunger by a wooden guide fastened to the base of the press. There is also fastened to the top of the guide for the ring, at a distance above the base of the press equal to the height of the cupel-ring, a piece of mood about § inch thick, under which the ring will just slide into place, and through which there is cut a circular hole exactly fitting the plunger, guiding it in its downward movement always in the same vertical line; this last guide not only directs the plunger, but also prevents the lifting of the ring by the plunger, upon the raising of the latter.

Jan 1, 1886

By John Charles

The Engineering Method. By John Charles Lou11sbul.y Fish. Stanford University Press. 1950. 186 P. $3.-This book is about the "professional habit often referred to . . . . as &apos;the scientific method&apos; . . ." It formulates for students the system of logic and reasoning that is the mark of the practicing engineer. The three chapters are, "The Method of Engineering", "Application of the Engineering Method" and "Uncertainties in Engineering." They cover logic and reasoning, terms, nontechnical problems, practical conditions controlling the engineering method, inescapable uncertainties and the method of coping with them. The author is emeritus professor of civil engineering at Stanford. The material presented here formed chapters 9, 10, and 11 of The Engineering Profession, by Hoover and Fish, second edition 1950. Elements of Ore Dressing. By Arthur F. Taggart. John Wiley & Sons, Inc., New York, 1950. $10.- A modern and practical introduction to the subject by the noted author of the Handbook of Mineral Dressing. The philosophy that a mill and all its parts comprise a single treatment process is a continuing theme in the book. Professor Taggart covers hand picking, screening, filtration, and electrical concentration. After introducing sedimentation, he takes up acceleration in free-settling, hindered-settling, sink-float, jigging, film and trough concentrators and shaking concentrators. A discussion of organic chemicals in flotation is followed by a detailed treatment of flotation. Final chapters deal with primary crushing, secondary crushing, grinding, transport, and controls and flowsheets.

Jan 3, 1951

By Rossiter W. Raymond

I DESIRE to call the attention of the Institute to an interesting experiment, which may turn out to be an indication of a valuable improvement in the manufacture of steel. As the members are aware, the addition of ordinary spiegeleisen, in the open hearth or Bessemer converter, to a bath of decarbonized iron, has a twofold object,-the recarbonization of the bath to a desired degree, and the remedy of the red shortness otherwise found to be inevitable in the final product. This red shortness is ascribed to the presence of oxide of iron in the molten metal ; and it is supposed that the manganese of the spiegeleisen, uniting with the oxygen of such oxide, carries it into the slag. At the same time there is a small percentage of the manganese usually left in the cast steel, probably to the improvement of its quality. Whatever be the true explanation the effect of the manganese is acknowledged to be not only beneficial, but necessary. But the use of spiegeleisen containing high percentages of carbon limits the quantity that can be introduced, because the carbon must be limited if soft steel is desired. This inconvenience becomes so serious as to prevent the use of ordinary spiegeleisen in the manufacture of steel containing more than, say two-tenths per cent. of phosphorus; since the quality of the steel can be made tolerable only by reducing its contents of carbon in proportion as the

Jan 1, 1875

By Wayne Anderson

Regarding the technical paper by Thomas E. Finch and Edward L. Fidler, "Recovery of Stray (Thin) Seams in Western Coal Mining." I would like to comment on this subject. In western Canada, most strip mines encounter thin seam coal or rider seams. Although the paper addresses the problems and costs associated with the recovery of this coal, it does not take into account what the savings are. Without looking at the savings, the "Total Objective" is of course not clear. I feel that in a stripping operation the mine can spend per ton (of the thin seam) up to their dragline stripping costs per ton to recover a rider seam or thin seam. The reasoning behind this is simply that this is the price the mine will have to pay to expose an equivalent amount of coal without the recovery of these thin seams. If the mine can recover a rider seam or thin seam for less than the dragline operating costs per ton, a savings will be realized. By recovering a thin seam or rider seam, the life of an ore body is extended by that amount of coal not thrown away. In addition, the cost of land acquisition, associated permits, capital, and reclamation will be reduced as more coal is delivered for a given area. When the above points are considered, the recovery of these thin seams can be very profitable and indeed worth recovering.

Jan 1, 1983

By Rossiter W. Raymond

I desire to call the attention of the Institute to an interesting experiment, which may turn out to be an indication of a valuable improvement in the manufacture of steel. As the members are aware, the addition of ordinary spiegeleisen, in the open hearth or Bessemer converter, to a bath of decarbonized iron, has a twofold object,—the recarbonization of the bath to a desired degree, and the remedy of the red shortness otherwise found to be inevitable in the final product. This red shortness is ascribed to the presence of oxide of iron in the molten metal; and it is supposed that the manganese of the spiegeleisen, uniting with the oxygen of such oxide, carries it into the slag. At the same time there is a small percentage of the manganese usually left in the cast steel, probably to the improvement of its quality. Whatever be the true explanation the effect of the manganese is acknowledged to be not only beneficial, but necessary. But the use of spiegeleisen containing high percentages of carbon limits the quantity that can be introduced, because the carbon must be limited if soft steel is desired. This inconvenience becomes so serious as to prevent the use of ordinary spiegeleisen in the manufacture of steel containing more than, say two-tenths per cent. of phosphorus; since the quality of the steel can be made tolerable only by reducing its contents of carbon in proportion as the

NORMAN B. PILLING (author&apos;s reply to discussion *).-The discussion by Mr, Bassett raised one or two points that deserve further discussion. The printed figure for the lead content of the copper used was 0.015 per cent. and not 0.15 per cent., upon which his comment was based. A copper having the latter figure would, of course, be quite unusual. Mr. Bassett takes exception to the writer&apos;s statement regarding the distribution of cuprous oxide in wrought copper and states that "the FIG. 1.--ROLLED AND ANNEALED SHEET. ETCHED WITH AMMONIA AND HYDROGEN PEROXIDE. X 75. eutectic of copper with cuprous oxide is usually found between the crystals of pure copper, whether in the cast or the wrought form." While it is very well known that during the solidification of cast copper the cuprous oxide is segregated completely as an envelope of cuprous oxide-copper eutectic around the crystals of copper free from oxide, it is the writer&apos;s opinion that, as a result of repeated rolling, this eutectic structure is quite destroyed and the small particles of cuprous oxide become widely scattered, and in the recrystallization following, during annealing, the rearrangement of the grain boundaries takes place with much indifference to the actual distribution of these particles. In the accompanying micrograph, taken from a rolled and annealed sheet, the random distribution of the small cuprous-oxide particles with reference to the location of the grain boundaries may be seen.

Jan 3, 1919

By C. K. McArthur

THE subject of classification is so broad that this discussion is con-fined to what the author believes is of prime importance in connection with proper grinding and classification. The years passed have witnessed many noteworthy changes in fine grinding and classification, which have been accompanied by a readjust-ment of ore-dressing flowsheets for the preparation of better ground and/or sized products at an expenditure of less. power, steel and main-tenance than formerly. Nowhere in the industry is more being done in the way of experimental work to lower costs than in grinding circuits, because, at best, grinding costs are high. Recent years have indicated that, on the average, finer grinding has a real application. Without careful preparation of the process feed, no operation can be highly efficient or successful. In an earlier paper, the findings of an extensive survey at representa-tive concentrators were presented1. Also, in the year of 1935, a technical discussion was given by Dr. J. V. N. Dorr (Some Notes on Classification Trends in America) before the Chemical, Metallurgical and Mining Society of South Africa. In both papers mentioned, much has been said regarding flowsheets, grinding and classification. The author is very familiar with these papers, having had considerable to do with the actual operation of the flowsheets, as well as large mills and classifiers in the work described. Some data from the second paper have been included in the following discussion.

Jan 1, 1937

C. Le Neve FosteR, Llandudno, Wales: I regret that Prof. Clowes is not here, and also that I cannot produce one of his lamps for inspection. The lamp has but just passed the experimental stage, and is now on sale in England for the purpose of testing it in practice. The only complaint I have heard made against it is the high price. It costs six or seven guineas. Possibly that would not frighten you on this side of the water as much as it does us. R. W. RaymonD, Brooklyn, N. Y.: So far as my obsrvations and experience go, we have not yet reached a state of affairs in the coal-mines of this country which calls for the general use of safetylamps by common miners. Certainly such a practice is to be avoided if possible, on account of the recklessness of miners, which it seems almost impossible to control by warning or discipliue. It is much better, if practicable, to confine the use of safety-lamps to inspectors or " fire-bosses," and not to permit the miners to work or to go where naked lights cannot be carried. In a colliery near Pottsville, Pa., with which I was connected for five years, and which had the reputation of being highly "fiery " (jets of fire-damp bubbled continually through the puddles in the gangways, and a thin sheet of it lay along the roof), we managed to avoid all serious

Jan 1, 1894

By H. L. Sheakley, D. J. Coolidge

This paper does not deal with all sands used in the glass industry in Missouri; it covers only that used in the plate-glass factory at Crystal City. However, it is probably safe to say that other sands, pro- duced throughout the state for this purpose, are of identical nature. The glass sand used in Missouri is cornrnonly called the St. Peter deposit, which is ascribed to the Ordovician Rock series in the form of sandstone. This St. Peter deposit, aside from a few small outliers, covers a large area of eastern Missouri. It forms, through a broad curve, the northeast margin of the typical Ozark region between Cape Girardeau on the southeast and Mineola, Montgomery County, on the northwest. The belt is extremely irregular, varying from one to ten miles in width; its length is 150 miles in a straight line. The outcrop near the entrance to the Crystal City mine appears in the form of a sandstone bluff approximately 30 ft. high, running along Plattin Creek (Fig. I). Above the sand rock an overburden of Joachim limestone appears, which thickens to nearly 300 ft. and forms the hill commonly called Buck Knob. Test holes where drilled at various points and the drillers&apos; log indicate that the St. Peter deposit ranges in thickness from 63 to 71 feet. Properties of the St. Peter Sand From an analysis of the glass sands of the St. Peter formation in Missouri, the follow-

Jan 1, 1948

By D. J. Coolidge, H. L. Sheakley

This paper does not deal with all sands used in the glass industry in Missouri; it covers only that used in the plate-glass factory at Crystal City. However, it is probably safe to say that other sands, pro- duced throughout the state for this purpose, are of identical nature. The glass sand used in Missouri is cornrnonly called the St. Peter deposit, which is ascribed to the Ordovician Rock series in the form of sandstone. This St. Peter deposit, aside from a few small outliers, covers a large area of eastern Missouri. It forms, through a broad curve, the northeast margin of the typical Ozark region between Cape Girardeau on the southeast and Mineola, Montgomery County, on the northwest. The belt is extremely irregular, varying from one to ten miles in width; its length is 150 miles in a straight line. The outcrop near the entrance to the Crystal City mine appears in the form of a sandstone bluff approximately 30 ft. high, running along Plattin Creek (Fig. I). Above the sand rock an overburden of Joachim limestone appears, which thickens to nearly 300 ft. and forms the hill commonly called Buck Knob. Test holes where drilled at various points and the drillers&apos; log indicate that the St. Peter deposit ranges in thickness from 63 to 71 feet. Properties of the St. Peter Sand From an analysis of the glass sands of the St. Peter formation in Missouri, the follow-

Jan 1, 1948

By M. Bourgon

The conductivity of liquid copper sulfide has been measured as a function of the mole fraction of sulfur in the melt at three temperatures: 1170°, 1250°, and 1300°C. The results show that a) the conductivity of copper-rich Cu,S is independent of the sulfur pressure in the furnace, and b) the conductivity of sulfur-rich copper sulfide increases rapidly with sulfur pressure. Assuming that the band theory is applicable to liquids leads to the conclusion that copper-rich copper sulfide is an intrinsic semiconductor, in which case electrons act as carriers. The activation energy for conduction in this case has been calculated to be 0.7 ev. On the other hand, sulfur-rich copper sulfide behaves as a p-type semiconductor, positive holes being responsible for conduction. IN order to elucidate the structure of Liquid copper (1) sulfide, Derge, Pound, and Osuchl have studied the electrical conductivity of this compound as a function of temperature. Their results showed that the conductivity is rather high, of the order of 100 ohm" cm", and that the temperature coefficient of conductivity is positive. This high conductivity seemed to indicate electronic rather than ionic conduction. This conclusion was checked further by Derge, Pound, and Yang,2 who measured the current efficiencies of copper sulfide melts at various temperatures. In all cases, the current efficiency was found to be nil, indicating the absence of appreciable ionic contribution to the conduction in

Jan 1, 1958

By Frederic H. Wright

The secondary metals industry might well be defined as the group of remelters, smelters, refiners, and manufacturers that convert scrap metals or residues to commercial forms. In this industry, scrap metals and residues are processed to pro- duce refined metals, ingot alloys, fabricated shapes, and chemical products. Secondary metal is defined as metal recovered from commercial scrap, that is, scrap that has entered the processor&apos;s plant in scrap form. Metal recovered by a manufacturer from "home scrap" generated in his own plant is not considered to be secondary, because it represents part of the original stock that simply requires additional treatment before emerging as a finished product. In any economic study, a basic point of measurement must be chosen, and in the case of secondary metals, the melting pot or its counterpart represents the stage in which metal is converted from scrap to some more usable form. Beyond this point there is often no means to distinguish between secondary metal recovered from scrap and virgin metal produced directly from ore. In the last fifteen or twenty years the secondary metals industry has grown to major importance. Some consumers distrust secondary metals, but frequently this distrust serves only to prove an inability to keep up with the times. A rapidly decreasing number of manufacturers like to boast that they use only virgin metals, but a little investigation would show them that more than one third of all

Jan 1, 1943

By E. J. Roberts, E. B. Fitch

Most classifiers in use today are, in function, settling pools. A fluid suspension of particles is passed through a pool at such a rate that only a fraction of the particles-the coarser fraction-has time to settle out of suspension. The rest are carried on out of the pool as overflow. The most fundamental way in which such classifiers differ is in the mechanism used to remove the settled particles from the pool. The particles may gravitate from the pool, as in the various sand cones, or they may be conveyed mechanically from the pool by drags, spirals, or reciprocating rakes. The mechanism of settling pool classification and its limitations are discussed. A method for calculating countercurrent classifications is presented. The practical validity of the calculation method has been confirmed through 20 years of use within The Dorr Co. During this time it has been used on diverse feeds and has been checked against many types of settling pool classifiers, with close agreement in nearly every case. Excellent elimination of third critical mesh particles and finer ones may be obtained in a countercurrent classifications series where all stages separate at the same mesh, but elimination of first and second criticals is inherently limited. Spectacular elimination of all criticals may be obtained by arranging successive stages to classify at successively coarser mesh. Improvement in elimination is obtained at the cost of an increased internal recirculation, but this may be tolerable in many cases.

Nov 1, 1956

With this issue of the Bulletin, the Institute puts into operation a plan which it has long had under consideration for enlarging its field of usefulness to its members. We refer to the Index to periodical literature bearing on mining, metallurgy, and related subjects, which will be found in the advertising section at the end of the Bulletin. The Index is printed on alternate pages so that anyone who desires to compile a card index can readily clip the items and paste them onto cards. By its affiliation with the Engineering Societies Library, the Institute possesses unexcelled facilities for the preparation of this Index, since practically every important engineering or technical paper published anywhere in the world is regularly received by the library. The items for publication in the Index are first selected by the library staff, but their final approval and their order of arrangement remains in the hands of the editor. A word should be said in explanation of the system of classification that has been adopted. It will be noted that the classification is extremely broad, no attempt having been made to gather the references into closely specialized groups. Our reason for breaking away from the modern tendency toward minute specialization is based upon the fact that the fundamental principles underlying all engineering are not by any means so diversified as has commonly been supposed. For example, it is not at, all unlikely that an engineer engaged in large-scale ore mining in the Southwest can profit by observing the methods employed by his colleagues in the Pennsylvania coal mines. It is notorious also how extensively the brotherhood of chemical engineers has profited by the. earlier experiences of the ore-dressing and metallurgical engineers. If the Index were minutely sub-divided, it would always be possible that the coal-mining engineer, for example, might fail to observe a most important paper because it happened to be listed tinder the head of iron mining. For this reason, mining practice in general is consolidated under one head. The same line of reasoning applies to other divisions as well. In order to make the Index of practical value to all members of the Institute, wherever they may be situated, the library will undertake to supply, for a nominal charge, an abstract, a translation, a typewritten copy, a photostat copy, or the original of any article in the Index. Requests for service of this character should be addressed directly to the Engineering Societies Library, 29 West 39th St., New York. Members are urged to cooperate toward the success of this new departure by sending us suggestions. Although every effort has been made to anticipate the wishes of the members, it is almost impossible to foretell what services may be most useful to our 7000 constituents. Furthermore, it is known that some men prefer one method of classification while others would find another method more convenient.

Jan 9, 1918

By H. C. Ray

ABOUT the beginning of 1930, coal preparation had reached the stage where the cleaning of coal by liquid or air had become the order of the day. Since that time many new preparation plants have been installed in spite of the years of depression in the coal industry, and this is indicative of a trend wherein the coal producer found it expedient to manufacture a cleaner product in order to compete with other fuels. It was also about 1930 that, because of the difficulties encountered with fine coal in cleaning plants, dust collectors came into use. Both cleaning plants and dust collectors, therefore, were much discussed at the engineering meetings of the early 1930&apos;s. During these meetings the many advantages to be gained through the use of dust-collecting systems were pointed out by Hebley,1 Appleyard2 and others. The great possibilities of new markets for this product were emphasized and discussed at the same time; however, the disposal of the collected dust remained a problem. Since the purpose of dust collecting is to improve the preparation and, consequently, the salability of the coal, it seems illogical to return the collected dust to any of the coal being prepared for market use, as is done in preparation plants that include dust-collecting systems. The logical thing is to dispose of the dust in some useful and practical manner outside of the tipple. As a practical matter, this can be done in one or both of two ways; either by consuming the dust at the mine&apos;s own power plant or by marketing the dust direct to the consumer. The latter method not only offers the greatest opportunities, but is the most important, because of inequalities that may exist between the quantity of dust collected and the consuming capacity of the mine&apos;s power plant. In considering the more important marketing possibilities, we are confronted immediately with the problems connected with the handling and transportation of so fine a material. It is this problem, rather than the problem of finding new markets, that has been responsible for the lack of progress in the matter of dust disposal. It is the purpose of this paper to point out again some of the potential market outlets, and also to describe an existing system of handling and transporting coal dust. To the best of the writer&apos;s knowledge, this is the first and only operation in this country that has handled fine-mesh coal in bulk 50-ton lots direct to the consumer. POtential Markets for Fine-mesh Coal Dust In general, the potential market outlets would include any operation of which the pulverization of coal is a necessary part. To be more specific, a few of the better known operations of this type must include: colloidal-fuel plants, briquetting plants, "sea coal" distributing plants, water-purification plants and, obviously, pow-

Jan 1, 1944

By G. G. Gunther, C. L. Boeke

(Any discussion resulting from presentation at the Los Angeles Extractive Metallurgy Division Meeting will appear in the November 1953 issue.) I. M. Symonds (Cia Minera de Penoles, Monterrey, N. L., Mexico)—This is a most interesting paper describing zinc deleading operations. Mr. Gunther was kind enough to show me his operation last fall. Outside of the excellent results, I was most impressed by the ease of control. I had expected a difficult operation requiring careful control and supervision, but found one requiring little attention. The only disappointing fact of the separation is the poor copper recovery in the concentrate of the deleading float. The final zinc concentrate still has about 3 pct chalcopyrite (assuming the copper is chalcopy-rite) which adversely affects the zinc grade. If the copper mineral is free, the poor recovery is probably due to the high cyanide concentration. Fortunately, about 75 pct of the copper is recovered before the pulp goes to the zinc circuit. Mr. Gunther&apos;s remarks about proper cyanide to zinc sulphate ratios cannot be overemphasized. Although our experience has been mostly confined to the conventional Pb-Zn separation, we have found these ratios most important, and more important in the mill than in the laboratory. The laboratory appears to give optimum results over a wider range of reagent control than the mill, especially in regard to the effect of cyanide. In the mill in handling relatively high grade ores, we usually find that ratios of cyanide to zinc sulphate of 1 to 10 or 20 or higher work best. Where there is a substantial amount of chalcopyrite present, it has been noted that cyanide in the range of 0.02 to 0.10 lb per ton of ore is often beneficial in zinc rejection and possibly in copper recovery in the lead concentrate, while larger amounts, say 0.20 to 0.25 lb per ton, will float more zinc and cause a serious rejection of chalcopyrite. On an ore with 15 to 20 pct Zn content, we have had to use 0.8 to 1.2 lb of zinc sulphate per ton of ore with the above cyanide to obtain optimum results. Sometime ago we made a laboratory study following Parral and Santa Barbara practice on an ore which never had a very satisfactory rejection of zinc in the lead concentrate. The results were not encouraging and a mill test was not run. Since then the study has been reopened using fresh zinc concentrate from the mill in the laboratory instead of one made in the laboratory. A reasonably clean lead float from the zinc concentrate was obtained. It has been checked several times and each time the zinc concentrate made in the mill responds and the one made in the laboratory does not. Although undoubtedly some reasonable explanations can be given, it is presented here only

Jan 1, 1953