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By Christopher Haycocks, Michael Karmis, David G. Lundy

Roof bolting is the most common means of support in under- ground coal mines. The main advantages of this support system are the relative ease of installation and the ability to provide a stable and unobstructed work area. Roof bolts can be broadly classified into two categories, mechanical and resin bolts. Currently, about 20% of all bolts used are the resin types, and trends show an increasing popularity of these kinds. Although the reinforcing effects of resin bolts have been well demonstrated, there is, nevertheless, a considerable lack of knowledge of their interaction with the surrounding strata. To study this interaction and to further investigate the mechanisms involved in resin bolting, an instrumentation system was designed and tested in a southwestern Virginia coal mine. The instrumentation system was composed of straingaged resin bolts, convergence and differential sag stations, and a borescope. Strain gages mounted on the bolt determined axial, bending, and shear strain at several levels along the axis of the bolt. The roof movement, as measured by the convergence and differential sag readings and as observed by the borescope, correlated well with the strains registered on the bolts.

Jan 1, 1983

By Norman Brown, Victor V. Damiano

ThE present paper proposes a mechanism of dislocation multiplication at internal inclusions or cavities and presents experimental evidence of such sources in zinc. Using an etching technique recently described by Damiano, Tint, and Herman1 to study the three-dimensional aspects of dislocations in bulk zinc crystals, an investigation was made of helically shaped and closed-loop etch patterns found to be associated with inclusions. Crystals containing 0.1 pet Cd and grown from the melt were deformed slightly by bending and then aged at room temperature to precipitate cadmium at the dislocations. The crystals were cleaved along the (0001) plane and then etched with Gilman's2 etch. Crystals were continuously viewed on the (0001) plane while the etching was in progress and numerous helical and closed-loops etch patterns were continuously recorded as shown in the sequences printed directly from the cine film in Fig. l(a) and (6). These etch patterns are not to be confused with the etch patterns previously reported by Damiano and Herman3 which revealed dissolution spirals on the (0001) plane of high-purity zinc crystals. In the present case, precipitates arranged in the form of closed loops or helicies are progressively uncovered by etching after suitable aging of cadmium doped zinc crystals. Viewed with dark-field illumination as shown in Fig. 2, portions of a helical figure and subboundaries were revealed simultaneously. Continuous viewing while the etching was in progress revealed in Fig. 1(b) that the short line segments observed on single photomicrographs were in fact continuous and described a helix which had its terminus at an inclusion. The observations suggested that a dislocation once nucleated at the interface between the inclusion and matrix may act in such a way as to produce ad-

Jan 1, 1964

By H. l. Burghoff, A. I. Blank

J. J. Kanter.*—The authors of this paper have demonstrated that at 500°F their alloy will elongate, under appropriately adjusted stress, one or two per cent over a period of 6000 hr. Then they show that after the alloy has so elongated, it will still elongate anothcr 40 per cent if it is tested at ordinary temperature. I should like to ask the authors how much more than 2 per cent over a period of 6000 hr. their alloy will elongate at 500°F. H. L. BuRghofE.—We do not know, because we have not carried out stress-rupture tests on this material. I believe your point concerning the desirability of stress-rupture testing is very well taken. In the material that we have subsequently tested we have not seen any signs of deterioration. We do not know how much further it is possible to go beyond the 2 per cent before finding grain-boundary separation. We have not encountered any under the conditions of the test. W. E. Kingston.†—IS this particular type of copper susceptible to strain-aging, and if so at those comparatively low temperatures, is that going to affect the shape of the curve? By strain-aging I mean the phenomena that certain ferrous alloys show in which the resistance to deformation increases suddenly during the low-temperature creep cycle, apparently due to some precipitation type of reaction, perhaps analogous to hydrogen embrittlement. H. L. BUrghoff.—I believe that this material is not subject to strain-aging of this type. It is very high in copper content, of course, nearly loo per cent. There are some very minor impurities and it carries a small amount of phosphorus, which, unless it is present as an oxide, should be in solid solution well within the solubility limits. I believe it does not precipitate

Jan 1, 1945

By Charles Mitke

(San Francisco Meeting, September, 1915) INTRODUCTION THE Copper Queen mine is composed of seven divisions which are operated through the following shafts: Division Shaft Depth, Air Current No. Feet Uncle Sam 600 Downcast (shut clown April, 1914, to 1 curtail production) Southwest 600 Downcast 2 Czar 400 Downcast 3 Holbrook 600 Downcast 4 Spray S00 Downcast (shut clown April, 1914, to curtail production) 5 Gardner 1,000 Downcast 6 1 Dallas 1,400 Downcast 1 Lowell 1,600 Upcast 7 Sacramento 1,700 Downcast " I I The workings of the different shafts are connected by motor-haulage drifts on the even numbered levels. The general location of the orebodies and workings is illustrated by the vertical projection of orebodies of the district as shown in Fig. 1. The Uncle Sam, Southwest, and Czar workings have many connections to the surface through raises and extensive cracks that were caused by moving ground. These divisions are cool and are ventilated entirely by natural means. The Holbrook is ventilated partly by natural and partly by artificial ventilation, while the Spray, Gardner, Lowell; and Sacramento are ventilated entirely by mechanical means. In some of the divisions mentioned above a considerable quantity of air exhausts through shafts of adjoining properties.

Jan 9, 1915

By P. E. Hopkins

In speaking of the economic geology of southeastern Ontario, W. G. Miller and C. W. Knight1 say that "there occurs in southeastern Ontario a variety of minerals and rocks of economic value, probably as great as in any district of like size on the North American continent. Some of these deposits, including marble and trap, are inexhaustible. Others, including talc and iron pyrites, have proved to be of considerable economic importance. From time to time, during the last 50 years, the following minerals and rocks have been mined or quarried with varying success: gold, iron pyrites, zinc blende, copper pyrites, galena, mispickel, magnetite, hematite, talc, actinolite, mica, marble, ophicalcite, feldspar, fluorite, apatite, corundum, graphite and sodalite. All of the economic materials, with, the exception of fluorite, appear to be of pre-Cambrian age. The fluorite veins penetrate the Ordovician, Black River, limestone." Accompanying that report was an article by the writer on the Queens-boro Pyrite Area which includes one of the two working pyrite properties in southeastern Ontario. In the present paper will be given a brief description2 of all the known pyrite deposits in the area which may at some time possess an economic value, with fuller descriptions of the two working mines—The Canadian Sulphur Ore C,o.'s mine near Queensboro, and the Nichols Chemical Co.'s property at Sulphide. The earliest mining of iron pyrites in Ontario was done in 1868 on the Billings property near Brockville. The mines were closed down in 1879 under the assumption that they were exhausted. Many other

Jan 1, 1917

By John M. Warde, Raymond M. Richardson

What to do with atomic wastes is one of the major problems of the atomic age. Unlike other waste materials, these cannot be burned, evaporated, or filtered, and the transfer of radioactive material from one physical or chemical state to another is not a complete answer, because only time diminishes radioactivity. Rate of decay of radioactive materials varies from a few seconds to several thousand years and cannot be altered by known economic methods. At present the Atomic Energy Commission and its contractors are coping with the situation adequately. Intensification of private development of atomic power could, however, pose problems in the nation's nuclear energy program.

Jan 5, 1955

By E. A. Rychkun

The transition from Larger word type computers to the small byte oriented micro-computers has allowed specialized software to be placed directly under the control of the people requiring solutions. In addition, with the advent of interactive graphics, many complex geological and mining engineering problems can be solved graphically, thereby further forcing obsolescence on larger computers. Although the industry has not yet caught on or taken full advantage of this fact, some companies have begun to move in this direction. One such case is the Coal Evaluation System presently in use at Manalta Coal Ltd. in Calgary, Alberta. This system, designed to allow interactive analysis of simple to complex coal deposits, leads one from geophysical/core log data, to geological modelling, strip or open pit design, equipment selection, cost estimation, and cash flow analysis. The micro-computer system used is portable, stands alone, and costs less than $120,000. It is the purpose of this paper to present the coal evaluation system and its development methodology which maximizes the use of the newest computer technology. Further, in order to illustrate the practical application of the system, an example application based upon a large operating coal mine will be discussed.

Jan 1, 1983

By J. S. Kirkaldy, G. R. Purdy

THE formation of ferrite in supersaturated aus-tenite has been the subject of considerable speculation and investigation. Aaronson has recently reviewed the data pertinent to this reaction.' Since these data in all cases refer to ternary or high-order alloys it is not possible to put them to the test of simple binary diffusion formalism. It has not, therefore, been possible to make a certain statement as to the controlling mechanisms in the process. An assessment of the difficulties inherent in the conventional statistical metallographic approach suggested that a study of the problem by means of a macroscopic two-phase diffusion couple might contribute useful information. Accordingly, such a couple was synthesized, and the rate of motion of a ferrite-austenite phase boundary (the growth of an austenite layer at the expense of a ferrite layer) was determined. Wagner originally produced a diffusion solution applicable to the motion of a planar phase interface in a binary diffusion couple, assuming local equilibrium throughout the diffusion zone. This solution, which is stated free of typographical error* in Ref. where a is the position of the interface in A space (A = x/fi), C; and CL1 are the equilibrium inter-facial concentrations in phases I and 11, C: and C*1 are the initial bulk concentrations in phases I and 11, and & and are diffusion coefficients (assumed constant). If a diffusion couple consisting of homogeneous layers of ferrite and austenite in equilibrium is raised to a higher temperature, the austenite layer will grow at the expense of the ferrite. Provided that the thickness of the ferrite layer is much less than the diffusion length of carbon in ferrite, we can set , so that Wagner's solution reduces to

Jan 1, 1963

By O. Lietard, J. Yvon, R. Mercier, J. F. Delon, J. M. Cases

INTRODUCTION Fineness is one of the main characteristics of powders and this parameter is the object of several definitions based on criteria connected with their uses as well as their determination methods. In trying to obtain the best reaction surface, fineness is characterized by the determination of the specific surface, but in other cases, particle size analysis is used. These two main methods are not, in fact, entirely independent and their complementary nature provides information concerning the morphology of the particles. In the case of a product formed by isodimensional spheres, the relationship between the specific surface and the diameter is well known: [S = 6 spd] where p is the specific weight of the material and d the diameter of the spheres. With no monodimensional spheres, but rather a granulometric distribution whose occurrences follow a mathematical law (1), the relationship is more complicated. The relationship between the specific surface measured by gas adsorption and the data of the particle size analysis is much more difficult to predict in the case of asymmetric porous particles, whose particle size distribution curves do not correspond to a known statistical law.

Jan 1, 1980

By R. B. Sosman, J. C. Hostetter

We have shown in the preceding paper that practically all natural oxides of iron contain a determinable percentage of ferrous iron, and in many cases the percentage approaches that in magnetite itself. Some of these oxides are true homogeneous solid solutions. Others are not homogeneous, and can be separated magnetically into fractions. The nature and cause of this inhomogeneity in certain special cases form the subject of the present paper. Magnetic FRactionation of Oxides of Iron The magnetic fractionation of a sample of oxide can be conveniently carried out by powdering the material very fine, and exposing it at various distances from the poles of an electromagnet. The magnet that we used was specially designed1 to give a strong field together with a steep gradient outside of the poles. It is set in a frame, with the pole pieces directed downward. A glass plate can bc adjusted at various distances beneath the poles. If the fine iron oxide powder is placed just beneath the glass plate, successive portions of the powder are picked up by the magnetic attraction and are caught against the glass plate, the most magnetic portions being taken up at the greatest distance from the poles. Some natural oxides can thus be separated into several fractions of different magnetic susceptibilities. Among other natural iron oxides, we examined the powder obtained by crushing some crystals of hematite from Elba.2 We found that

Jan 1, 1918

By A. S. Doty, E. I. Larsen, F. R. Hensel

The alloy under discussion is a Pig. I shows results of heat-treating tests nickel-silicon bronze and is one of many on two typical nickel-silicon bronze castings age-hardening or precipitation-hardening of the type on which the observations were copper-base alloys. The hardening constituent is a nickel-silicon compound.l The quenching temperature necessary to produce hardening by a subsequent aging treatment is a function of the composition and extends from about 700°C. to 950°C.; the aging temperature range extends from 4000 to 600°C. The work carried out by the authors of this paper was confined to cast alloys having compositions within the ranges of: 1.5 to 3.00 per cent Ni; 0.4 to 0.75 per cent Sj: balance. comer. made. A quenching temperature of 750°C. produces almost as high a hardness on subsequent aging as do quenching temperatures of 850' and 900°C. Several foundries have spent years of active and intelligent effort in trying to control the casting and heat-treating variables of nickel-silicon bronzes and finally gave up the attempts because of the inconsistencies of results.2 This undesirable characteristic was not manifest in the ultimate hardness or conductivity but primarily in tensile strength and ductility, as shown in Table I. The variation in tensile properties was often much greater than that existing on the alloys

Jan 1, 1941

By Ralph Hultgren

FEW phase diagrams of alloys composed of two transition metals have been adequately studied, probably because of the high melting points involved. Transition metals are the elements that have inner shells incompletely filled with electrons. They comprise groups IIIa to Villa of the periodic table, including more than half of all metals. We have chosen to study two systems whose comparatively low melting points allowed the alloys to be melted in a molybdenum resistance furnace. The nickel-palladium system proved to consist of a simple series of solid solutions, but iron-palladium manifested several remarkable features. The main characteristics of the latter diagram were decisively established, but lack of time prevented precise determination of phase boundaries. The gamma to alpha transformation in this system is unusual and warrants further study. Grigorjew1 determined the liquidus and solidus of the iron-palladium system by thermal methods. He found a minimum melting point, but no eutectic. He also found that palladium lowered the gamma to alpha and raised the gamma to delta transformation temperatures of iron, with a complete series of solid solutions existing between gamma iron and palladium. His measurements also indicated a compound or super-lattice near the composition FePd3. Jellinghaus2 found that annealing at 500° C. greatly increased the magnetic coercive force of an alloy of composition FePd. X-ray dif-fraction photographs showed that a tetragonal ordered phase had formed during the anneal.

Jan 1, 1939

Prof. Mathesius analyzes the running of Howland's furnace No. 19, according to the method described by him in Stahl and Eisen, 1916, Nos. 30 and, 31, and in his work "Die physikalischen und chemischen Grundlagen den Eisenhüttenwesens" (Spamer, Leipzig). By assuming 500 Cal. lost from the hearth by radiation and cooling water per kilogram of pig iron made, a throat-gas temperature of 600° C., and taking the ratio of C02/CO as 0.64, he finds that his diagram would show 0.68 kg. of carbon oxidized per kilogram of pig iron, while Howland gives 0.66 kg. He expresses himself as well satisfied with this test of the accuracy of his theory. Making the further assumption that the heat losses from the shaft are 1,000 Cal. per kilogram of pig iron (twice as

Jan 5, 1917

By James Norman

SPODUMENE is a lithium-bearing pyroxene, and is an important source of lithium compounds. Because of its high alumina and lithia content it might be a desirable constituent of glass batches. The use of spodu-mene in ceramics will undoubtedly increase, as it has been shown that a mixture of the proper proportions of this mineral with soda feldspar and potash feldspar has a much lower maturing temperature upon firing than has any one of the three components.1 The mineral spodumene seldom occurs as pure mineral, but ordinarily with feldspars, mica and quartz. All spodumene-bearing rocks tested contained these minerals as gangue. Small amounts of iron and manga-nese oxides also were present, usually as stains on the silicate grains. Mica associated with the spodumene carried a considerable amount of lithia. This was discovered in flotation tailings, which, although virtually free of spodumene grains when examined microscopically, showed 0.4 to 0.5 per cent Li20 on chemical analysis. The lithia content of micas picked from the North Carolina spodumene rock was variable. Some samples contained little lithia, others more than 3 per cent. In 1938, under the supervision of Oliver C. Ralston, ? the Bureau of Mines, in cooperation with the Tennessee Mineral Products Corporation, undertook to study the beneficiation of North Carolina spodumene by froth flotation. The Bureau had previously published investigations on the beneficiation of spodumene.2,3 The methods described in the second publication' did not give good results with badly weathered spodumene rock, so that more thorough investigation of the subject was warranted.

Jan 1, 1940

By Paul Billingsley, Augustus Locke

The mining districts of the first order' of the western United States (and borders) are those named on Fig. 1. These fall into four groups: (1) in the eastern outliers of the Rocky Mountain system; (2) in the Rocky Mountain system itself; (3) in the Great Basin; and (4) in the Sierras and Coast ranges. Of these four groups, the first three are almost entirely of Tertiary age and are within a belt of compressive folding which we shall call the Rocky Mountain-Great Basin thrust arc. The backbone of this belt is shown by the line BAC. The position of the ore districts in this belt indicates a conformance to linear elements of the continental pattern. These are additional to the peripheral elements emphasized by Butler.2 Nature of the Thrust Arc The thrust arc separates regions of contrasted kinds. To the east of it are flat-lying plateaus interrupted by earlier mountain folds; to the west, sunken basins, in which block-faulted ranges lie like an anchored fleet in a sea of desert wash or lava. The. cross-sections are as shown in Fig. 2. The backbone of the belt is the upward and eastward moving block represented by the Glacier Park, the Wasatch, and the Virgin mountains, successively. The structure represented on these sections is the culmination of events which began far back in geologic time and throughout which a contrast has existed between the regions east and west of the backbone line. Before the Pennsylvanian, as Fig. 3 shows, there was a shallow shelf on the east and a deep marine trough on the west; after

Jan 1, 1935

By Paul Billingsley, Augustus Locke

The mining districts of the first order' of the western United States (and borders) are those named on Fig. 1. These fall into four groups: (1) in the eastern outliers of the Rocky Mountain system; (2) in the Rocky Mountain system itself; (3) in the Great Basin; and (4) in the Sierras and Coast ranges. Of these four groups, the first three are almost entirely of Tertiary age and are within a belt of compressive folding which we shall call the Rocky Mountain-Great Basin thrust arc. The backbone of this belt is shown by the line BAC. The position of the ore districts in this belt indicates a conformance to linear elements of the continental pattern. These are additional to the peripheral elements emphasized by Butler.2 Nature of the Thrust Arc The thrust arc separates regions of contrasted kinds. To the east of it are flat-lying plateaus interrupted by earlier mountain folds; to the west, sunken basins, in which block-faulted ranges lie like an anchored fleet in a sea of desert wash or lava. The. cross-sections are as shown in Fig. 2. The backbone of the belt is the upward and eastward moving block represented by the Glacier Park, the Wasatch, and the Virgin mountains, successively. The structure represented on these sections is the culmination of events which began far back in geologic time and throughout which a contrast has existed between the regions east and west of the backbone line. Before the Pennsylvanian, as Fig. 3 shows, there was a shallow shelf on the east and a deep marine trough on the west; after

Jan 1, 1935

The mining districts of the first order' of the western United States (and borders) are those named on Fig. 1. These fall into four groups: (1) in the eastern outliers of the Rocky Mountain system; (2) in the Rocky Mountain system itself; (3) in the Great Basin; and (4) in the Sierras and Coast ranges. Of these four groups, the first three are almost entirely of Tertiary age and are within a belt of compressive folding which we shall call the Rocky Mountain-Great Basin thrust arc. The backbone of this belt is shown by the line BAC. The position of the ore districts in this belt indicates a conformance to linear elements of the continental pattern. These are additional to the peripheral elements emphasized by Butler.2 Nature of the Thrust Arc The thrust arc separates regions of contrasted kinds. To the east of it are flat-lying plateaus interrupted by earlier mountain folds; to the west, sunken basins, in which block-faulted ranges lie like an anchored fleet in a sea of desert wash or lava. The. cross-sections are as shown in Fig. 2. The backbone of the belt is the upward and eastward moving block represented by the Glacier Park, the Wasatch, and the Virgin mountains, successively. The structure represented on these sections is the culmination of events which began far back in geologic time and throughout which a contrast has existed between the regions east and west of the backbone line. Before the Pennsylvanian, as Fig. 3 shows, there was a shallow shelf on the east and a deep marine trough on the west; after

Jan 1, 1935

By Walter M. Small

Austria produced approximately 800 cisterns of 10,000 kg. each (56,000 bbls.) of crude oil of a 0.9428 sp. gr. during 1935. Of this Gosting II well near Zistersdorf, owned by the Erdolproduktions-Gesellschaft m.b.H., produced 86 per cent of the total, averaging a little over 1.8 cisterns, or about 125 bbl., per day. Gosting IVa of the same company was put in production early in December and produced a total of about 70 cisterns (4900 bbl.). Gosting IV was a failure, but a directional hole drilled from the same derrick produced Gosting IVa. Gosting I, a well owned jointly by the company above mentioned and the Raky-Danubia, was deepened late in the year and made about 2800 bbl. of oil at the rate of 70 bbl. per day. Completions during the year were as follows: In the Gosting pool, Gosting IV and IVa, drilled with rotary tools, the latter producing from Sarmat at a depth of 934 meters (3065 ft.); Kronberg I, of European Gas & Electric Co. with cable tools in Flysch at a depth of 566 m. as a dry hole; in the Oberlaa gas pool, one cable-tool well of the same company at a depth of 266 m. as a dry hole and one Fauck-Haiek system well of the Vacuum Oil Co. at a depth of 483 m. as a dry hole; one rotary hole of the European Gas & Electric Co. at Enzersdorf a/d. Fischa plugged and abandoned in Sarmat after a blow out and gas eruption at a depth of 699.5 meters. The status of drilling wells at close of the year is as follows: In the Gosting pool, Erdol Bohr- und Verwertungs G.m.b.H., north of the producing area, was drilling with rotary at 990 m., Raky-Danubia is rigged up to deepen the old Windisch-Baumgarten hole, Rohoel-Gewin-nungs A.G. (Vacuum-Shell combination) rigging up rotary south of the production, and Steinberg-Naphta G.m.b.H. (Musil) was deepened with light rotary to 830 m.; at Enzersdorf a/d. Fischa, the European Gas & Electric Co. E-2 rotary-drilled hole stood at 1533 m. in Miocene waiting

Jan 1, 1936

By James Norman, E. W. Gieseke

Spodumene is a lithium-bearing pyroxene, and is an important source of lithium compounds. Because of its high alumina and lithia content, it might be a desirable constituent of glass batches. The use of spodumene in ceramics will undoubtedly increase, as it has been shown that a mixture of the proper proportions of this mineral with soda feldspar and potash feldspar has a much lower maturing temperature upon firing than has any one of the three components. The mineral spodumene seldom occurs as pure mineral, but ordinarily with feldspars, mica and quartz. All spodumene-bearing rocks tested contained these minerals as gangue. Small amounts of iron and manganese oxides also were present, usually as stains on the silicate grains. Mica associated with the spodumene carried a considerable amount of lithia. This was discovered in flotation tailings, which, although virtually free of spodumene grains when examined microscopically, showed 0.4 to 0.5 per cent Li²O on chemical analysis. The lithia content of micas picked from the North Carolina spodumene rock was variable. Some samples contained little lithia, others more than 3 per cent. In 1938, under the supervision of Oliver C. Ralston,S the Bureau of Mines, in cooperation with the Tennessee Mineral Products Corporation, undertook to study the beneficiation of North Carolina spodumene by froth flotation. The Bureau had previously published investigations on the beneficiation of spodumene.2,3The methods described in the second publication3 did not give good results with badly weathered spodumene rock, so that more thorough investigation of the subject was warranted. Study of Method of Flotation Separation Most of the work on concentration of spodumene was done with rock from near King's Mountain, North Carolina. Rock from two

Jan 1, 1942

By Herman Poole

When finely divided ferrous sulphide, FeS, is roasted at a moderate, carefully-regulated temperature, the iron and sulphur are oxidized, the first products being probably ferrous oxide and sulphurous acid. In the presence of oxygen of the air the ferrous oxide soon becomes ferric oxide, and, in the presence of oxygen and the ferric oxide, the sulphurous acid oxidizes to sulphuric acid. These facts are well known, having been established by Plattner many years ago. As a further reaction, some of the sulphuric acid parts with a portion of its oxygen to oxidize more ferrous oxide to ferric oxide, and a portion of it escapes uncombined, or else unites with the iron oxides to form sulphates. Ferrous sulphate is usually soon oxidized to ferric sulphate, and if the heat becomes sufficient, this is then decomposed into sulphuric acid and ferric oxide. As a result of these reactions a mass of more or less pure ferric oxide is formed which is generally made porous by the escaping gases and, if rabbled properly, practically all the sulphur is expelled. If ferric sulphide or ordinary pyrites, FeS2, is roasted, a portion of the sulphur sublimes and usually burns to form sulphurous or sulphuric acid, although at times and under favorable conditions, some of the sulphur is driven off uncombined, and can be collected as such. Under ordinary methods of roasting, however, only a small portion escapes combustion. By the combustion of the sulphur an increase of heat is developed and, as a consequence, the reactions mentioned take place more rapidly and actively,—more sulphuric acid is formed and the oxidation is more complete—nearly all the iron being left as ferric oxide with practically no sulphate or ferrous oxide. When the iron sulphide is in lumps the roasting proceeds generally as with fines, but with some changes due to mass. The

Jan 1, 1906