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By Mark R. Pettitt

Noise surveys conducted in underground coal mines have consistently indicated that auger mining machines subject the operator and helpers to excessive noise exposure. The machine cutting heads have been identified as the primary noise source. This report documents the research program conducted to (1) investigate the nature of the cutting head noise problem, (2) develop noise control concepts, (3) devise in-mine survivable techniques to implement the noise control concepts, and (4) build and demonstrate prototype reduced-noise auger miner cutting heads. The dynamic forces generated during coal cutting by the brittle fracture of coal are predominently low frequency. The low-frequency (less than 1500 Hz) structural response of the cutting head, therefore, determines the noise radiated by the cutting head. The most feasible methods of reducing the cutting head low-frequency response are to increase both the structural stiffness and the low-frequency damping. A technique was devised to achieve these goals. The standard plate helix was replaced by a sand-filled hollow helix of triangular cross section, and the core diameter was increased with an attendant reduction in helix depth. Extended in-mine tests demonstrated the operational capability of the reduced-noise auger cutting heads. The simple noise control concepts are valid for all continuous miner cutting heads. The sand-filled hollow helix technique, which achieved a 10 dB(A) noise reduction for the auger, can be used on any helix-bearing Cutting head.

Jan 1, 1983

By G. E. McElroy

This report discusses the construction and use of an all-pressure psychrometric chart in which the requirements of simplicity of appearance and absolute accuracy have been waived, to a certain extent, to provide for the rapid determination of psychrometric data and for the rapid solution of air-conditioning problems of major interest to the mining industry. Many mines in which air-conditioning problems are important are situated at elevations far above sea level and embrace great differences in elevation - in excess of 8,000 feet in certain mines - throughout their airflow circuits. Under these conditions, the effects of variations in the pressure of the atmosphere upon the physical properties of the mixture of air and water vapor of which it is composed are considerable and should be taken into account in the solution of problems. The simple types of psychrometric charts in common use, such as the Carrier, Bulkeley, Hill, and Goff (American Society of Heating and Ventilating Engineers Guide), are not generally suitable, in that they are drawn for a single barometric pressure - 29.92 inches mercury.

Dec 1, 1947

By Peter Halbach

Cobalt-rich ferromanganese crusts are one type of the two oxidic metallic mineral resources in the deep ocean that incorporate metals supplied and transported from both land (aerosols, continental run-off) and sea sources (oxygen-minimum zone, hydrothermal alteration of the oceanic crust). The substances directly precipitate from cold seawater under more or less oxic conditions and form thin layers (2 up to 25 cm thick) on hard substrate rocks like volcanic hyaloclastites, weathered basaltic rocks and/or carbonate-fluorapatite; in the crusts many metals therefore exist in the highest state of oxidation. Deposits of the Co-rich ferromanganese crusts are found throughout the global oceans on the flanks, terraces and summits of seamounts and submerged volcanic mountain ranges and platforms, where the ocean currents have kept the seafloor more or less free of sediment for millions of years. The process of hydrogenetic precipitation is basically an inorganic colloidal-chemical and surface-chemical mechanism. Elements in seawater may occur as dissolved hydrated ions or as inorganic as well as organic complexes which in general have either a positive or a negative surface charge depending on the pH of the respective aqueous environment. Those complexes may form hydrated colloids that interact with each other and with other dissolved hydrous metal ions. Hydrated cations such as Co, Ni, Zn, Sn are, for example, attracted by the negatively charged surfaces of colloidal hydrous Mn-oxide particles, whereas hydrated anions (e.g. oxyanions) and elements forming larger complexes with low-charge densities (e.g. U, As, Th, Hf, REE) are attracted by the slightly positively charged hydrous Fe oxihydroxide particles.

Jan 1, 2008

A self-appointed, committee consisting of J. Waldo Smith, Chairman, Richard S. Buck, J. J. Carty, J. Parke Channing, E. L. Corthell, Alfred Craven, Thomas Crimmins, Gano Dunn, George Gibbs, Alex. C. Humphreys, F. L. Hutchinson, Charles Warren Hunt, D. S. Jacobus, John W. Lieb, William Barclay Parsons, George H. Pegram, Charles F. Rand, Calvin W. Rice, Robert Ridgway, William L. Saunders, Merritt H. Smith, Bradley Stoughton, and William H. Wiley, organized a course of seven free lectures on military engineering, which were given by Captains Thomas M. Robins, Richard T. Coiner, Edward D. Ardery, Corps of Engineers, United States Army, and which was under direction of Major General Leonard Wood. The United Engineering Society presented, without charge, the use of the auditorium for the purpose of these lectures, but the interest proved to be more than three times as much as had been expected, and it was therefore necessary to divide the courses into three parts, one of which was given in the afternoon in the auditorium of the United Engineering Societies Building, one in the evening in the same place, and another in the evening in the auditorium of, the American Society of Civil Engineers. These lectures occurred on Mondays, from Feb. 14 to Mar. 27, 1916. The subjects and speakers were as follows: Feb. 14, 1916: Organization and Duties of Engineers in War, and what Engineers in Civil Life will be called upon to do in the Defence Of the United States. Captain Thomas M. Robins, Corps of Engineers. Feb. 21, 1916: The Service of Reconnaissance Including Surveying, Mapping and Sketching, Photography and Map Reproduction. Captain Richard T. Coiner.

Jan 5, 1916

By N. W. Lord

There hare been made at one or two places in Ohio, during the last year or two, some irons of rather unusual phosphorus-percentages. The first of these which I had occasion to examine came from Moxahala Furnace, in Perry county. The furnace was built originally to smelt an ore found in large deposits near its furnace in the " black band" horizon. The deposit was easily exposed by simple stripping;" it was from six to eight feet thick, being a blne carbonate ore, very free from silica. This ore yielded, on analysis, from two to 3 per cent. of phosphorus, when carefully sampled. The furnace company had trusted entirely to old analyses made on "outcrop" ore, well weathered, and received all other results with indifference. The result of the first run of the furnace was an iron in large whitish-gray crystals, and so brittle that it could be pulverized in a mortar. This iron contained 4.90 per cent. phosphorus. A limited quantity only was made, which was gradually disposed of as a great ('softener" to foundries. The Moxahala Furnace was subsequently run on Lake Superior ore mainly. The second case of such iron occurred last summer at Mt. Vernon Furnace. A deposit of what was locally known as "Hallelujah" ore, was opened for the furnace. This ore was a blue carbonate, similar to the first-described. The iron made was pure tin-white in color, and showed large crystals without a trace of the grain of ordinary pig-iron. It was sopposed at the furnace to be spiegeleisen, and was sent to me to be

Jan 1, 1884

By Ahmadzadegan. Arash, Anil Saigal, Michael A. Zimmerman

"In this study, the rheology of liquid crystalline polymer (LCP) melts through simplified 2-D and 3-D die geometries is simulated using Polyflow™. It is known that rheological properties of LCPs are close to long chain polymers and their directionality is close to those of small molecule liquid crystals (SMLCs). As a result, different rheological models (both viscoelastic and generalized Newtonian) for long chain polymers in Polyflow™ were investigated based on the available capillary rheometer data. By varying the parameters in these models, it is possible to adjust the effect of shear viscosity, normal stress differences and relaxations times on the rheology of the polymer. The free surface of the extrudate coming out of the die is simulated and the amount of die swell for different types of rheological models is compared. This study indicates that the Bird-Carreau model best applies to thermotropic LCP materials as quantified by die swell. Since the rheology of the LCPs affects the orientation of the crystals, the result of this simulation can be further used to predict the orientation of crystallines inside and outside the die.IntroductionAny rod like molecule or crystal tends to orient itself in the direction of shear as it moves within a flow. Since polymers consist of long chains of molecules, they experience the same phenomena when flowing in the melt condition. For most polymers, the molecules change direction and distribute uniformly in space during the solidification. However due to the higher inertia of the crystals in the liquid crystalline polymers, the oriented crystals will keep their order during the solidification and as a result the final product will show anisotropy in material properties."

Jan 1, 2012

Council and Standing Committees, 1979-1980 President: D. A. Viljoen. Senior Vice-President: Dr P. R. Jochens. Junior Vice-President: G. Y. Nisbet. Honorary Treasurer: Dr D. G. Krige. Immediate Past President: Dr M. G. Atmore. Members of Council: J. D. Austin, A. N. Brown, J. A. Cruise, C. E. Fivaz, J. S. Freer, P. N. Harris, H. E. James, Dr R. P. King, Prof. F. Q. P. Leiding, Dr B. K. Love¬day, D. G. Malan, C. S. Macphail, J. C. Mostert, H. G. M. Rose, G. C. Thompson, R. A. von Maltitz, Dr H. Wagner. Past Presidents Serving on Council: R. J. Adamson, H. Britten, J. K. E. Douglas, Prof. D. D. Howat, Dr J. P. Hugo, D. G. Maxwell, Prof. R. P. Plowman, Dr R. E. Robinson, Dr M. D. G. Salamon, P. W. J. van Rensburg, P. A. von Wielligh. Chairman, Witbank-Middelburg Branch: R. B. Smith. Chairman, Orange Free State-Klerksdorp Branch: W. C. Mather. Materials Engineering Division, Chairman: Dr J. P. Hugo. Secretary: G. Pienaar. Standing Committee Chairmen: Membership, G. Y. Nisbet; Technical Programme Metallurgy, H. E. James, (Prof. R. P. King) ; Technical Programme Mining, H. G. M. Rose; Vacation School Metallurgy, J. C. Mos¬tert; Vacation School Mining, J. D. Austin; Awards, Dr M. G. Atmore ; Excursions, A. N. Brown ; Adjudications, Dr M. G. Atmore ; Constitution, Rules, and Policy, Dr M. G. Atmore ; Monograph Series, Dr M. G. Atmore ; Training and Career Guidance, P. A. von Wielligh (D. G. Malan) ; National Phoenix Committee, Dr R. E. Robin¬son; 1982 Council of Mining and Metallurgical Congress, Dr M. G. Atmore ; Mines and Works, Dr M. G. Atmore.

Jan 1, 1980

Council and Standing Committees - 1981/82 President: G. Y. Nisbet. Senior Vice-President: Prof. A. N. Brown. Junior Vice-President: Prof. R. P. King. Honorary Treasurer: Prof. D. G. Krige. Immediate Past President: Dr P. R. Joehens. Members of Council: B. C. Alberts, J. D. Austin, P. T. Fewell, C. E. Fivaz, J. J. Geldenhuys, Dr A. K. Haines, P. N. Harris, H. E. James, C. G. Knobbs, Dr B. K. Love¬day, Dr J. Lurie, C. S. MacPhail, D. G. Malan, J. C. Mostert, G. C. Thompson, Dr H. Wagner. Chairman, Witbank/Middelburg Branch: B. Rohrmann. Chairman, Orange Free State/Klerksdorp Branch: K. F. W. Eick. Chairman, Materials Engineering Specialist Division: G. Pienaar. Past Presidents serving on Council: Dr M. G. Atmore, H. Britten, Prof. D. D. Howat, Dr J. P. Hugo, D. G. Maxwell, Prof. R. P. Plewman, Dr R. E. Robinson, Prof. M. D. G. Salamon, P. W. J. van Rensburg, D. A. Viljoen, P. A. von Wielligh. Standing Committee Chairmen: Constitution, Rules and Policy, Dr P. R. Jochens; Membership, Prof. R. P. King; Training, Career Guidance and Education, P. A. von Wielligh; Journal, Prof. A. N. Brown; Monograph Series, D. G. Malan; Technical Programme - Metallurgy, C. E. Fivaz; Technical Programme - Mining, P. N. Harris; SAIMM Schools - Metallurgy, Dr B. K. Loveday; SAIMM Schools - Mining, J. D. Austin; 1982 CMMI Congress, Dr M. G. Atmore; Awards, Dr P. R. Jochens; Adjudication, Dr P. R. Joehens; Phoenix National Committee, Dr M. G. Atmore; Excursions, J. C. Mostert; Mines and Works, Prof. A. N. Brown; World Mining Congress - National Committee, Prof. R. P. Plewman.

Jan 1, 1982

By W. E. Gaby

THE form of dip chart here presented for the use of the profession was devised by the author when he was confronted with a particularly heavy job of geological section making and. did not have any of the usual tables or charts at hand. This was at the property of the Teziutlan Copper Co. in Puebla, Mexico, where the orebodies are much faulted and lie conformably with a slightly inclined and. much folded schist. Because of the low dip and the folding of the orebodies, the engineering, and geological data respecting them were best represented on vertical cross-sections quite closely spaced. A less finished form of the chart was published in the Mining & Scientific Press of Aug. 6, 1921, with an explanation of its use. I have checked the new drawing for accuracy against the calculated table given, and constructed an explanatory diagram beneath. As some geologists are accustomed to using the table, I have included it, since no advantage is obtained by mere interpolations from the chart to get the required angle, except as it gives a mental picture of this angle. The chart gives a more rapid and much easier solution when cases multiply so that it becomes desirable to eliminate the tedious manipulations of a separate protractor. In fact, using the parallel ruler as des-cribed, it is not even necessary to make note of the angle sought. It is brought out graphically, leaving the mind free to note the correlations. The chart itself may be made more convenient by reproduction on celluloid with a slot running on the zero line of the protractor.

Jan 9, 1922

By N. A. Ziegler

THE present publication is a continuation of the work on gas analysis, described in a paper presented before the Institute of Metals Division a year ago.1 While that paper was largely descriptive in character, dealing with the various parts of the apparatus and method of operations, the present one gives numerical data obtained as a result of a series of experiments with iron-carbon alloys. The apparatus and the methods applied are essentially the same as previously described, changes being only in minor details. Attention should be called to the fact that in the present work we are dealing with the gaseous mixtures obtained as a result of vacuum melting of various ferrous alloys. It should be understood that when the terms "degasified sample" and "products of degasification" are used, they refer to the sample remaining after the vacuum fusion of the alloy and the gaseous products removed therefrom, respectively. The writer does not wish to create the impression that the metallic products of this process are absolutely free from any gaseous elements, nor that the gases obtained are present as such in the original sample. These two points are not yet definitely known and are subjects for future investigation. The point, however, which has been established beyond doubt, is that all the gases dealt with come from the metallic charge and are present either in the charge as such, or are produced as a result of chemical reactions going on within the charge.. The suggestion that the gases are due to the reactions between the metallic charge and the refractory materials has no valid basis.

Jan 1, 1929

CHARLES F: WILLIS,* Bisbee, Ariz. (written discussion?).-An employment department operated only with the object of relieving the foremen from hiring and for the purpose of centralizing record keeping is not likely to be entirely successful, and is doing but a small part of the good that practice has shown is possible; although it was .probably a desire to save time and to conduct the business more conveniently that led many mining companies to centralize their employment department. The ultimate object, however, is the reduction of labor turnover, by obtaining men better qualified to fill the positions to which they are assigned, by following up their work and providing for transfer to other departments or for promotion, if advisable, by reducing the number of quits for inconsequential reasons, and by supervising such laying-off as is necessary in such a way that the permanent force is not upset. It provides a stability 'of employment, free from favoritism and paternalism, probably the best form of employment insurance that we can have. The value of the employment department is in direct proportion to the breadth of its supervisor, his ability to estimate and place men, his sympathy in dealing with their petty troubles, and his analysis of quits and the reasons therefor. There is probably no better index of the soundness of the industrial relationship between the employee and the employer than the reasons why men quit; an intelligent, unbiased analysis of these reasons tells where corrective measures are necessary. In nine cases out of ten the reasons are small grievances, easily corrected, and are things usually overlooked by mine officials.

Jan 6, 1919

Council and Standing Committees - 1983/84 President: Prof. R.P. King Vice Presidents: J.D. Austin and H.E. James Honorary Treasurer: Prof. D.G. Krige Immediate Past President: Prof A.N. Brown Members of Council: B.C. Alberts, Prof. S. Budavari, N.J. Devine, Dr C.J. Fauconnier, P.T. Fewell, C. E. Fivaz, J. S. Freer, Prof. G.G. Garrett, J.J. Geldenhuys, Dr A.K. Haines, Dr B.K. Loveday, G. Pienaar, B.E. Protheroe, Dr O.K.H. Steffen, G.C. Thompson, Dr H. Wagner, Dr P.T. Wedepohl Chairman, Witbank/Middelburg Branch: H.C. van Zyl Chairman, Orange Free State/Klerksdorp Branch: D.A. Parfitt Past Presidents Serving on Council: Dr M.G. Atmore, Dr J.P. Hugo, Dr P.R. Jochens, Prof. R.P. Plewman, G.Y. Nisbet, Dr R.E. Robinson, Prof. M.D.G. Salamon, P.W.J. van Rensburg, D.A. Viljoen, P.A. von Wielligh Standing Committee Chairmen: Adjudication, Prof. A.N. Brown; Awards, Prof. A.N. Brown; Banquets, J.S. Freer; Constitution, Rules and Policy, Prof. A.N. Brown; Excur¬sions, J.S. Freer; Journal, H.E. James; Membership, H.E. James; Phoenix National Committee, Dr M.G. Atmore; SAIMM School - Extractive Metallurgy, Dr A. K. Haines; SAIMM School - Mining, Dr H. Wagner; Special Publica¬tions, J.D. Austin; Technical Programme - Extractive Metallurgy, Dr B.K. Loveday; Technical Programme - Mining, G. C. Thompson; Technical Programme -Physical Metallurgy, G. Pienaar; Training, Career Guidance and Education, Dr M.G. Atmore; World Mining Congress - National Committee, Prof. R.P. Plewman; Working Group Physical Metallurgy, Prof. G.G. Garrett

Jan 1, 1984

By Alan G. Fricker

Cyprus Gold NZ Ltd will be recovering residual free cyanide in barren gold pulp by air stripping. Laboratory investigations by DSIR have indicated additional advantages by recovering the cyanide from pregnant pulp. These are a lower leach pH, a greater cyanide recovery and less carbon consumption. They have a net economic advantage of $1.20/tonne over recovery from barren pulp. The realisation of these advantages is dependent on three crucial technical aspects -optimum pH for dissolution, the absolute loss of cyanide and the stability of the aurocyanide ion. The laboratory investigations described herein address these aspects. Earlier work had indicated that the rate of dissolution of freely revolving gold discs at constant cyanide ion concentration increased with decreasing pH from 11 to 8. Attempts to repeat the work in a more controlled manner by measuring the corrosion potential and current density have, to date, not been reproducible, but do not contradict the earlier observations. Cyanide recoveries and balances were obtained on leaches at pH 10.5 and 9 at the same cyanide ion concentration -the lower pH requiring three times as much total cyanide. Unaccounted-for losses, unfortunately, exceed the accounted-for losses, making interpretation of the balances difficult. Nevertheless, it appears that the additional amount of cyanide at the lower pH of 9 may not be fully recoverable. It may not, however, prove necessary in practice to use more cyanide at a lower pH. Both the gold and silver cyanide complexes remain available for carbon adsorption, as do mercury, copper and iron. Zinc, and probably cadmium, nickel and lead, may precipitate during stripping, which is an environmental advantage.

Jan 1, 1991

By J. H. Slater

THERE is nothing particularly new about the use of sinter in a blast-furnace burden. For many years flue dust has been sintered at the various blast-furnace plants to put it in a form that could be recharged to the furnace with some assurance that it would stay in the second time. This paper is not a compilation of scientific data but only an attempt to give our experience with sinter. There are some unexplained discrepancies in the tests given here, such as the flue dust produced and iron tonnages, but the results given are the results that were obtained. Sinter is not the cure-all for blast-furnace problems. A good coke is still the most important factor in good furnace operation. However, good sinter is a big help. As flue dust is produced under varying operating conditions and fluctuates greatly in carbon content, it is difficult to produce from flue dust alone a uniform sinter, which will give satisfactory blast-furnace results. Sinter made from flue dust alone will change in character with every carbon variation. Almost invariably flue dust con-tains carbon in excess of the amount necessary to make good sinter, and this excess must be burned out, This, of course, necessitates reduction of the speed of the sintering machine and thus a decrease in tonnage, An alternative is to dilute with a carbon-free material to use up the excess carbon. High-carbon material when sintered results in a very dense, undesirable prod-uct, since the excess heat melts the charge into a hard, nonporous mass, and tends to form refractory silicates.

Jan 1, 1940

By F. C. Newton

REFINERS of lead by the Parkes process have always been solicitous of recovering the zinc used in the desilverization, and justly so, as the loss in zinc constitutes one of the heavy costs in this method of refining. Part of this loss is due to the absorption of zinc by lead, and in the present state of knowledge is not recoverable as metallic zinc. The remainder of the zinc, which finds its way into the precious-metal-bearing crust, is recoverable and naturally engages the operators' most exacting attention. Careful elimination of the impurities in base bullion has enabled the refiner to produce a zinc crust better adapted to retorting, which reflects favorably in the zinc recovery; and to produce a richer crust, thereby lowering the zincking cost, as the increased efficiency of the zinc results in less of it being in circulation. It is obvious that if the ratio of concentration be increased, a lessening of the amount of crust formed will ensue, throwing less work on the retorts and diminishing the amount of retort metal sent to the cupels, thus making an actual money saving in all these operations. In the effort to obtain a rich crust, the metallurgist has increased the heat to a considerable degree, upon the assumption that at the higher temperature the zinc-silver alloy could be squeezed free from the adhering lead. A further possibility for improvement suggested itself in the freezing-point curve of Prof. H. C. Carpenter, upon zinc and silver. Study of this curve disclosed the existence of a definite chemical compound, . Zn3Ag2, with a freezing point of 665° C., a promising compound for practical application.

Jan 2, 1915

By John Kafritsas

INTRODUCTION Deformations and failure of rock masses in elopes, foundations or tunnels can be caused by water pressures. On the other hand, deformations of a rock mass affect the flow of water (and hence water pressures) by changing joint apertures. Including the coupling between flow and deformation effects is therefore important both in assessing the stability and deformation of a rock mass and in determining the amount of seepage taking place through it. The model that will be presented hare treats the coupling of the flow and deformation behavior of a rock mass. Deformations are modeled using the Rigid Block Method (Distinct Element Method) (Cundall, 19741, that is by assuming that the rock mass is composed of rigid blocks with deformable contact points. Flow is modeled by recognizing its discontinuous features, as occuring in a system of interconnected conduits formed by the joints. The program can also deal with problems involving free-surface flow. Example problems involving representations of rock masses are presented. Coupled flow modeling of interconnected conduits should be contrasted to equivalent-continuum models on the one hand and to pipe network models on the other hand. Continuous models substitute an anisotropically permeable continuum for the discrete flow that occurs in rock joints. Pipe or parallel plates represent the other extreme of existing models; they account for the discontinuous character of the flow problem, but cannot model rock mass deformation and failure. The coupled rigid block-flow model can eliminate most of these restrictions. The coupling between water flow and deformation is most pronounced in rock masses which, because of the arrangement of their

Jan 1, 1984

By A. U. Seybolt, R. L. Fullman

THE Hume-Rothery rule relating the relative sizes of the solvent and solute atoms in a substitutional solid solution for moderate to extensive solubility is, of course, well known and much used in the design of alloys. No such rule has been obtained for interstitial solid solutions, although a qualitatively similar relationship would be expected. Among the most common interstitial elements, oxygen, carbon, and nitrogen which can dissolve in important amounts in the transition metals, only in the case of oxygen is there enough solubility data available for an examination of the possibilities of a simple relationship between the extent of solubility and the properties of the metal solvents. Three properties were examined: 1—size of the octahedral space V into which oxygen atoms fit, 2— the elastic modulus E, and 3—the free energy ?F of formation of a low oxide, such as is known to be, or would be expected to be, in equilibrium with the terminal solid solution. The size factor or octahedral volume is so closely associated with the well known Hume-Rothery con- cept of size factor that additional development of this subject is hardly necessary. The octahedral volume used was not corrected to an elevated temperature, as this correction would have made no significant difference. The second factor, Young's modulus E, must be considered, since it is a measure of the strain energy required to force neighboring atoms apart so that an oxygen atom may enter the octahedral volume. The temperature dependence of the elastic modulus of many metals has been reported by Köster,1 but for a rather limited temperature range. Since the

Jan 1, 1955

By Alan Stanley

R. T. Hukki (Finland Institute of Technology, Helsinki, Finland)—In the analysis of mill products containing minerals of appreciable difference in specific gravity the well-known principle of the method described by Stanley is applied in a number of ways for a variety of problems. The use of Le Chatelier bottle as explained in the paper may be a dependable and sufficiently accurate way, although no information is given as to the reproducibility of the specific gravity determinations. In the case of MacIntyre ore the method is applied for three separate products produced apparently without reagents and relatively free of fine slimes. Should it be applied for flotation products carrying a substantial amount of slimes, difficulties should be anticipated in the process of eliminating air inclusions from the sample. The difficulties mentioned above may be overcome by the use of a volumeter, an instrument designed for specific gravity determinations of finely divided solids in dry state. This instrument, see Fig. 4, is manufactured by F. Süffert-Bürner A. G. in Basel, Switzerland. Its operation is based on the law of Boyle and Mariotte. With the use of the volumeter, the specific gravities of test samples having a total volume of about 30 cm are easily reproducible within ±2 units in the second decimal of the specific gravity figure, and even better than that with utmost care. This accuracy is sufficient for ordinary operational control. How closely the specific gravity determinations follow the respective chemical assays depends primarily on the nature of the sample itself. In this respect no specific gravity instrument can give better results than those justified by the consistency of mineral distribution in samples analyzed.

Jan 1, 1954

Discussion of the paper of FRANK H. KNEELAND, presented at the New York meeting, February, 1914, and printed in Bulletin No. 97, January, 1915, pp. 61 to 65. B. F. TILLSON, Franklin Furnace, N. J.-I think it may be of interest in respect to the information we have received in regard to the danger of machinery in mining operations, to state that in the particular type of metal miming which the New Jersey Zinc Co. is doing at Franklin, during the past year, although there have been other accidents, that method of miming was free from any accident due to machinery underground. It may give a different light as to the relative degree of the importance of machinery as varying with different types of mining. ARTHUR WILLIAMS, New York, N. Y.-Mr. Kneeland's able presentation of this paper, it seems to me, bears out the suggestion which has been so frequently made that in this country we have a new profession, that of the safety expert or safety engineer, which calling, if properly carried out, would include also questions of sanitation. While Mr. Kneeland was speaking, it occurred to me that perhaps any one, however experi-enced he might be in mining generally, would pass through these mine shafts and these operating rooms, and the things which might cause accidents, which would cause accidents if the right conditions were to occur, would pass by entirely unnoticed by him, but when the safety expert goes into these places he sees these things which he immedi-ately recognizes as being spots of danger and provides means for their elimination.

Jan 5, 1915

By F. Louis Grammer

The difference between blast-furnace gas and ordinary producer-gas is chiefly that blast-furnace ga,s is higher in CO2 and lower in hydrocprbons and hydrogen, as is shown in Table I. Table I.— Volume-Composition of Producer-Gas and Blast-Furnace Gas. Producer-Gas. Blast-Furnace Gas. Per Cent. Per Cent. (Volume.) (Volume.) CO......22 to 33 25.5 CO2........ 6 to 3 13.0 H...13 to 7 1.5 CH4........ 3 to 1.5 0.0 N..54 to 60 60.0 If natural gas, water-gas, or by-product coke-oven gas be available, blast-furnace gas can be made to resemble very closely in calorific value the average producer-gas by merely mixing in one of these products, which are richer in hydrocarbons and hydrogen. Blast-furnace gas, however, possesses a virtue which is sometimes absent in producer-gas, especially with coals very high in sulphur—namely, that blast-furnace gas is relatively free from sulphur. In some regions the sulphur in coal is an acute problem, and it is highly desirable to find uses for the mine-products which are specially high in sulphur-content. An advantage would be gained if the coal were coked before charging into the gas-producers, but this adds to the expense. Sulphur may be partly eliminated from coal by washing it, the success depending upon the form in which the sulphur occurs, and upon the efficiency of the washer, but it cannot always be removed to the extent desired at most American plants. It is not practicable to remove all the sulphur from producer-gas by washing it, though Mr. Reinhardt, of Germany,

Jan 1, 1909