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By Walter E. Mingramm

The construction of rescue-apparatus on the principle of furnishing the wearer with air from a tank containing it under high pressure was given up by inventors about 20 years ago. Such an apparatus must supply continuously, for not less than two hours, nearly 50 liters of pure air at atmospheric pressure per minute, or a total of 6,000 liters (210 cu. ft.); and a cylinder containing this amount of air, under 2,000 lb. pressure, would weigh 180 lb. or more. Although apparatus has been recently constructed utilizing liquefied air, no experiments have been made to determine the regularity with which the air is generated, nor has its chemical composition been determined. Moreover, the chief objection to such an apparatus is the difficulty and cost of keeping on hand a large quantity of liquefied air. The system of furnishing the wearer of a breathing-apparatus with air which has given the best results, and has found

Jan 1, 1909

By Y. Dardel

Since the first determination of Dumas1 in 1880, many authors have tried to measure the solubility of hydrogen in solid aluminum, or at least the amount of dissolved gas in it. However, the interpretation of the results which have been obtained is still difficult. Sieverts? then Baukloh and Oesterlen,a during their gassing experiments could not determine any solubility of hydrogen in solid aluminum. On the other hand, Portevin, Chaudron and Moreq4 leaving the determination of the hydrogen solubility beyond the scope of their experiments, measured only the amount of gas that they could extract by high voltage positive ion bombardment and found up to 151 cm3 of gas per I00 g of metal. Winterhager,6 by repeated vacuum extraction during severe cold rolling, extracted up to 161 cm3 per 100 g. In both series of experiments, the extracted gas contained chiefly hydrogen with a small amount of nitrogen, carbon monoxide, carbon dioxide and methan. Later, Schmidt and von Schweinitze as well as Chaudron and Moreau7 showed the importance of the adsorbed layer of hydrogen, the extracted quantities being proportional to the surface and not to the weight of the sample, when its cleaning was not perfect. In earlier experiments, Steinhausers extracted from more massive samples nothing but a little amount (< 0. 5 cm3 per I00 g) of hydrogen, carbon monoxide and methane. Thus, according to these experiments the quantity of dissolved gas is probably very small and the effect of the surface could falsify the results of the extraction. However, owing to the care taken by Chaudron and his coworkers, it was clear that all the hydrogen extracted could not come from the superficial layer, or that the links which bound hydrogen to the surface were so strong that the usual method of cleaning could not destroy them. After the main parts of the experiments reported here had already been carried out, Eborall and Ransley9 published the results which they obtained with an analysor having an accuracy of 0.03 cm3 per I00 g, while that of the usual apparatus was only about 0.2 cm3 per I00 g. During all their experiments the adsorbed layer would have been a difficulty, for the value of the adsorbed hydrogen was approximately equal to that of the dissolved amount. Table i—Amount of Adsorbed and Dissolved Hydrogen (After Eborall and Ransley) Extraction Hz Adsorbed „ h2 dissolved Temperature Calculated Extraction OCcma 500 0.057 0.050 600 0.062 o.096 Since always keeping the same adsorbed layer is very difficult, an error in the correction for the adsorption can be made when using the apparatus of. Eborall and Ransley, as well as the earlier apparatus.

Jan 1, 1949

I;. D. Godshall, Everett, Wash. (communication to the Secretary) : In Mr. Morse&apos;s interesting paper several statements occur which seem to require correction and comment. This is the more appropriate, since Mr. Morse has mentioned me by name, and has cited my "Review of the Russell Process,"* so that silence on my part might be taken as indicating an assent which I cannot give. On the first page of his paper Mr. Morse says that the " goingback " of chlorination was " the only difficulty encountered at Aspen," and adds that he has " never seen any explanation " of the cause. The plain inference is that he now fills this complete

Jan 1, 1896

By H. J. Wasson

DEVELOPMENTS in Venezuela during the past few months have been obscured by the hap-penings in Seminole and, more recently, those in southwest Texas. The question has been asked whether or not the opening of these vast new, prolific areas in the United States may not have depressed prices to a point so low as to give the developments in the Caribbean countries a serious setback. Nothing of the kind, however, has taken place, and on the contrary, there has been demonstrated the fact that Venezuela can profitably produce great quantities of oil under existing market conditions, and at the same time finance the foundation for further large expan-sion in the future. The three big factors which contribute to place Venezuela in a unique position and tend to insure the steady expansion of its oil industry are, in the order of their importance: I. Reasonable oil laws backed by a sound govern-ment, which comprehends the all-important fact that the country&apos;s prosperity depends on the prosperity of its industries, in a word, perceiving that the goose which lays the golden egg merits considerate treatment. II. The low cost of placing Venezuela oil on our At-lantic seaboard; not over $0.60 per barrel. III. The uniformly high average production per well and the large area of some of the individual pools. Under these conditions Venezuelan producers may be expected to continue steady and profitable ex-pansion even in the face of further market slumps. Their position is analogous to that of the low-cost copper producers, and unless artificial barriers, such as tariffs, come into play, Venezuela will steadily grow in importance. Within less than five years it should be second only to the United States among the oil-producing countries of the world.

Jan 10, 1927

By Ralph H. Sweetser

AT the end of 1943 the charcoal pig iron capacity of the United States was at the lowest point in over 1110 years, with only one strictly charcoal blast furnace in operation, and all others permanently out of blast except one in Tennessee d reported to he running on part charcoal and part coke. Such a decrease in production has taken place in spite of the O.P A.&apos;s high-premium price on charcoal pig iron of +34 per ton f.o.b. furnace in Michigan. Depletion of the hardwood supply within fifty mlles or inure of the blast furnace is the reason why; the deplorable lack of reforesting is the cause.

Jan 1, 1944

By CARL B. SNYDER

PERHAPS the most extraordinary thing about business, the trade and production of the country as a whole, is its amazing continuity and growth, its momentum and energy. It goes on year after year, growing steadily, almost without breaks, in spite of every kind of disturbance. We have been grossly deceived into the idea that business is highly variable. We have taken a few things like pig iron, and the like, constructional activity broadly, and imagined that these are a trustworthy measure of trade. Actually they are the worst that we could find. They do not apply to more than 10 per cent or, at the most, possibly 15 per cent of the total of the country&apos;s industrial activity. The other 85 or 90 per cent, or even more, goes on growing surely and steadily just like the growth of population and the steady advance in technique, invention, discovery, and improved methods of production Let me give you what seems to me one of the most remarkable examples of this amazing momentum and regularity. You know that 90 per cent or more of the business of the country is done &apos;by means of checks. About seven-eighths of the total of all checks drawn are reported regularly every week in the newspapers. Let us follow these reports from week to week, just as they come, and plot them up against the correspond- ing weeks of last year, and the year before, and the gear before that, as far back as you would like to go. Take especially the figures for 140 selected cities out- side of New York.

Jan 1, 1929

By F. M. Morris

A large reserve of thick coal in southwest Virginia was developed by Clinch-field Coal Co. in 1957-1958 to produce a nominal rate of 1500 tph raw coal. Operation features coal cleaning in transit. Refuse removed averages 35 pct. Evolution of plant from initial conception to completion is discussed, selection of means applied is explained, and performance to date us design expectation is described. The long-range plan calls for ultimate handling capacity of 40,000 tpd raw coal with anticipated clean coal capacity of 26,000 tpd on a three-shift basis. From a materials handling viewpoint, the Moss No. 3 operation is principally of interest as an ensemble. Generally speaking, it uses time-tested equipment and ideas but some of these are employed on a scale that may be new in the industry. At present about 20,000 tpd of raw coal are being handled. This is expected to increase to 40,000 tpd as soon as business conditions justify it. The purpose of this paper is to discuss the evolution of the plant as to materials handling practices, to describe briefly the equipment and methods used, and to comment on performance in certain areas. The subject divides itself naturally into four phases: 1) operations at the mines, 2) transportation from mines to plant, 3) raw coal handling into the plant, and 4) transportation of refuse away from the plant. OPERATIONS AT THE MINES The coal reserves for Moss 3 are in southwest Virginia where Dickenson, Russell, and Buchanan Counties come together. This area contains about 15 square miles and over 100,000,000 tons of coal. Here the No. 4 (Tiller) and No. 5 (Jawbone) seams of the Norton Formation lie so closely together that for practical purposes, they constitute one seam of coal. This seam, which is called the Thick Tiller, varies from 10 to 18 ft in thickness and underlies Sandy Ridge, a mountain cresting between 2400 and 3300 ft above sea-level. At 18-ft seam height (which is considered to be the maximum practical mining height) the parting between seams will be about 3 1/2 ft thick and each bench of coal will be about 7 ft thick. Depending on the amount of impurities in the seams Drover. total reject in this height coal may approximate 50 pet by wt. It will average about 35 pet for the property as a whole. The first move in developing this resource was made in 1953 when contour maps of several square miles around Duty, Va., including all the known outcrop, were made by photogrammetry. At this time, it was felt the prospective operation would be served by the Clinchfield Railroad and a photogrammetric route survey was made by this railroad from Haysi to Duty. Study of the resulting maps indicated only one site—adversely owned—which might accommodate the size washing plant to be erected. Water resources of a dependable nature seemed nonexistent. In 1954 bulk washability tests were made on the Tiller Bench at the Moss No. 1 preparation plant. The tests indicated this portion of the seam, mined separately, would wash to 4 pet ash with good recovery. Also in 1954, development of Moss No. 2, south of Sandy Ridge, was begun. This mine is in the Tiller Seam where it is about 100 ft below the Jawbone Seam. The reasons for developing a mine in the normal Tiller Seam before tackling the Thick Tiller seemed compelling: Railroad service could be established quickly, communications were better (though not good!), more was known of the seam (it had been mined in the years 1911 to 19241, and there was no essential property to be acquired. After some legal skirmishing, the Norfolk & Western Railroad was granted the right to serve the new mine. Three decades earlier the old mine had been served by the Clinchfield Railroad. The event which triggered active development of Moss 3 was the Appalachian Power Co.&apos;s decision in 1956 to build a 450,000-kva power plant on Clinch River at Carbo. This solved the problem of marketing the steam coal which inevitably must be a product of a mine in the Thick Tiller. Management promptly decided to build the preparation plant at Carbo where an excellent site was owned; where railroad service existed; where telephone service could be obtained; and where roads, bridges, and water supply were tolerable.

Jan 1, 1961

By C. R. Knopp

Gas-oil relative permeability ratio is an important relationship in oil reservoir predictive calculations. A correlation has been developed from 107 gas-flood k/k tests on Venezuelan core samples. The correlating parameter is based on restored-state water saturation tests and&apos; is applicable to both consolidated and poorly consolidated sandstone reservoirs. Data of the correlation show that there are no distinguishah1e differences between the mass-data groupings for the two c1assifications A procedure is recommended for running .sufficient relative. permeability analyses to compute a geometric mean of the sample group. The geometric mean is more representative of the total core, and probably the entire reservoir. For example, while only one in four of the k,,/k,., test curves agreed closely with the resultant correlation of this report, the geometric mean curves of the 16 suites (three samples or more). showed good agreetment ill three cases out of four. INTRODUCTION The gas-oil relative permeability ratio is an important, fundamental relationship in most oil reservoir predictive calculations. Predictive calculations are made to estimate future reservoir production characteristics and ultimate oil recovery. The k1,/k2, relationship is specifically needed to relate the surface gas-oil ratio to the reservoir oil and gas saturation, and to calculate the relative movement of these phases within the reservoir whenever some of the more complex driving mechanisms are present. Laboratory k1/k2, tests are not generally run as a routine analysis. Consequently, k1/k2 data often are not available when needed because the cost of laboratory work could not be justified or the need for such data had not been properly anticipated. When laboratory k1/k2, data are available, they are often very difficult to interpret. For example, wide divergence is sometimes shown in a family of k1,/k1, tests representative of the producing horizon in a single well. With these considerations in mind, a study was made to determine if a relationship might exist between the k1,/k2, curve and some other simple laboratory test criteria. The most probable k1/k2, curve correlation for Venezuela described in this paper is the result of the investigation. The presented correlation defines the most probable gas-flood k,,/k,, curve through the medium of air-water capillary displacement and centrifuge water saturation tests. The laboratory procedures of these tests are. relatively simple, and inexpensive; test data should be. widely available- from routine analysis. DATA AVAILABLE, LABORATORY METHODS The report correlation utilized 107 gas-Hood k1/k2, tests run on sandstone cores of Venezuelan reservoirs. Table 1 is a general tabulation of data pertinent to the tests, while Table 2 summarizes the data. Thetests include 96 from Western Venezuela and 11 from Eastern Venezuela. Eighty-two- of the 107 test samples were sandstones that varied from poorly consolidated to-unconsolidated; 25 were consolidated. The average sample porosity was 26.7 per cent and the average permeability was 1,121 md; these values typify the better sandstone reservoirs of&apos; Venezuela. The Welge gas-flood technique,&apos; based on fundamental Buckley-Leverett frontal displacement theory, was introduced in about 1952 and is widely accepted in the industry. The laboratory procedure is relatively simple, rapid, and can be performed on small core samples. While there have been some minor variations in sample preparation and laboratory procedure in the tests used for the correlation, these tests can be generally summarized as follows. The core sample was first sol vent-extracted and dried. Connate-water saturation was restored by the oil-flushing or evaporation-blow down methods. At the beginning of gas flood the hydrocarbon pore volume was completeiy saturated with the test oil phase. Unsteady-state gas-oil displacement then began with the injection of nitrogen or helium. while the displaced oil and gas phases were incrementally metered at the out-flow face. From the test data, the k,,/k,, curve was calculated by the Welge method.&apos; The individual oil and gas relative permeabilities were also calculated." CORRELATING PROCEDURES In attempting to establish a basis of correlation, we found that broad mid-range sections of 105 of the 107 k,,/k,, test curves could be closely duplicated by a straight line. Only two curves did not show a degree of linearity in this region. Correlation-curve definition parameters were subsequently developed from this observation of consistent mid-range linearity. Possible correlating variables were limited to the physical properties measured on core samples that (1) were widely available as common test data and (2) could be easily and cheaply obtained through future laboratory work. The more obvious possibilities were porosity, permeability and

Jan 1, 1966

By B. M. Larsen, T. E. Brower

A perspective is presented of the steel plant sulphur distribution and elimination problem from coal to liquid steel ready for teeming, giving distributions of sulphur over a range of coke sulphur content, and some methods of sulphur control, in the blast furnace, external desulphuriza-tion between blast furnace and open hearth, distribution between fuel, slag, and metal, and methods and limitations of control of sulphur in the open hearth furnace. AS a part of the 1951 AIME symposium on sulphur in steelmaking, it was thought that a discussion of the distribution of sulphur throughout the whole series of operations, from coal and ore to finished steel ingots, might have some value in giving a perspective on the whole problem. The following discussion is an attempt to present such an overall picture. The order is that of the actual plant operations, beginning with a very brief consideration of the coking process. Sulphur in Coal and Coke Since by far the largest source of sulphur entering the steelmaking cycle is in the coal used to make coke for the blast furnace, it would seem reasonable to eliminate some of it, either from the coal, or the coke, or during the coking process. This has appeared impracticable up to the present, at least, for two main reasons: the low activity of the organic sulphur in either coal or coke, and because of price limitations involved in treating a low cost material such as coke. A variable portion, usually M or less, of the sulphur is present in coal in the form of pyrites or similar compounds, and a large part of this sulphur may be removed in the coal washery. Most of the sulphur, however, is normally present as "organic" sulphur, intimately associated with the coal structure. Its distribution prevents any separation by mechanical means. Its low activity makes improbable &apos; any rapid chemical removal, although hydrogen will remove sulphur from both coal and coke. Thus, prolonged recirculation of coke oven gas in the coking process would tend to leave a smaller percentage of the total sulphur in the coke residue. Table I shows a typical distribution of sulphur from coal into products in the coking process. As the sulphur in the coal increases, the sulphur in the coke tends to increase in about the same proportion. Sulphur in the Blast Furnace The best picture of the situation in the blast furnace is provided by a sulphur balance of raw materials entering, and of products leaving, the furnace. The difficulties in accurate weighing and sampling of the variable solid materials entering this process, and the number of hours required for the raw materials to descend through the furnace under variable operating conditions, make it difficult to obtain an accurate balance. However, balances made over periods of weeks or months tend to average out some of these uncertainties. Table I1 presents three typical sulphur balances similar to a number that the writers have calculated. In most of these the slag volume calculated from the sulphur balance is, in some instances more, and in other instances less, than the value corresponding to the best input and output balances of the other slag constituents (lime, silica, alumina, etc.). Probably the greatest source of error in these calculations is the sulphur content of the slag. Despite some possible inaccuracies the balances of Table II show rather definitely the following points: 1—That 87 to 95 pct of the total sulphur input is in the coke and 95 to 97 pct of the total sulphur output is in the slag. Also, that if any sulphur leaves the furnace with the gas it is relatively small, amounting to a possible 1 pct or less. 2—At the lower sulphur coke level of 0.86 pct the total amount of sulphur charged is 15 Ib of sulphur per ton iron increasing to 26 lb per ton at the higher sulphur, intimately associated with the coal struc-rare burdens containing sulphur-rich ores will the total sulphur burden fail to be nearly proportional to the content in the coke used. 3—The 7 to 9 pct of the total sulphur input from the limestone of furnaces B and C is due to the relatively high sulphur content of the stone, 0.226 and 0.265 pct, respectively. In the case of furnace A, the sulphur content of the limestone was only 0.06 pct which resulted in only 3 pct of the total sulphur input coming from this source. It is rather interesting to compare the sulphur balances of a typical ferromanganese furnace with

Jan 1, 1952

By Harry A. Lipsitt, Douglas Y. Wang

A fatigue study in completely reversed axial tension-compression has been perforried on high-purity titanium and on three high-purity alloys of titanium. The alloys each contain approxi7nately 0.75 at. pct of a single interstitial element; carbon, nitrogen, and oxygen, respectivley. The results corroborate a previously published theory which proposed that strain aging under alternating stress was responsible for the fatigue limit behavior of certain alloys. The present data indicate that in these alloys an increasing strain-talline aging effect under alternating stress is provided by oxygen, carbon, and nitrogen, respectively. CURRENT research on the nature of the fatigue limit in metals suggests that the presence of a fatigue limit in metallic materials is a manifestation of strain aging that occurs under alternating stress.lm5 A comprehensive theoretical model based on the above hypothesis has been developed to explain the existence of a fatigue limit.&apos; This model also provides increased insight into several other fatigue phenomena as under stressing, overstressing, and coaxing effects. The theory, as well, provides equal understanding for those cases where no real fatigue limit is observed. Briefly, this theory assumes that the S-N curve for a pure metal is a smooth function of the applied stress, and the effect of adding an element that is soluble (or forms a precipitate) in the pure metal is simply to shift the S-N curve to the right. If the added element confers the power to strain age, the result is a further shift of the S-N curve, this time upward and to the right. Since strain aging is not expected to be a strong function of stress, and since damage per cycle is known to be quite stress dependent, it is to be expected that there will be some limiting lower stress at which the strengthening due to strain aging will balance the damage due to crack propagation. This stress is the fatigue limit. The position of the fatigue-limit knee was thought to be a function of the magnitude of the strain-aging effect on both the finite and infinite life portions of the S-N curve. Although the strain aging hypothesis seems to be reasonably valid for bcc materials,2&apos;6 it needed to be tested for both fcc and cph metals. This report is the first of a series concerning the fatigue-limit behavior of titanium with varying amounts of the interstitial solutes (C, N,, and 4) that are known to cause static strain aging in titanium. Yield-point effects have been reported for polycrys-talline high-purity titanium alloys containing either carbon, nitrogen, or oxygen.7&apos;9 These effects were observed at testing temperatures in the range 100 to 300&apos;. In addition yield-point and strain-aging effects have been reported for single crystals of titanium containing 0.1 wt pct C plus N.&apos; These yield points were observed over a wide temperature range, but no room-temperature aging occurred. Aging at 180&apos; was required to cause the return of the yield point. The magnitude of the yield phenomena in titanium containing interstitials is not expected to be as large as is observed in bcc metals because of several factors. Titanium has a very high chemical affinity for oxygen and nitrogen. The thermodynamic stability of solutions of oxygen or nitrogen in titanium is recognized. Lattice parameter measurements of titanium containing arbon, oxygen,1° or nitrogen" show that the "c" parameter is expanded more than the "a" parameter, but that up to about 2 wt pct this results in an insignificant change of the axial ratio &apos;c/a." Ehrlich" has shown that the sites occupied by interstitial atoms in titanium are spherically symmetrical and therefore a lattice expansion, at a constant c/a ratio, results in a simple dilation of the interstitial site. Such a dilation involving no shear has been shown to react only with edge components of dislocations.13 This causes only a weak pinning action. Shear stresses would be anticipated locally when only one of the two interstitial positions was occupied. The carbon atom will cause a symmetrical distortion of the lattice whereas the oxygen and nitrogen atoms have, in addition, the previously mentioned chemical affinity of titanium for these elements. These factors will result in a considerably smaller reduction of free energy upon the association of interstitial atoms with dislocations, and therefore a much weaker pinning than has been observed for the bcc metals. These considerations would lead to the hypothesis that of the interstitial elements considered here carbon would cause the strongest pinning effect in titanium where the amount of interstitial in solution is constant. This hypothesis will be borne out in the analysis of the present results.

Jan 1, 1962

By Edna A. Dancy, Gerhard J. Derge

The specific conductance of FeOx,-CaO melts in contact with iron was found to decrease from 200 ohm-1 cm-1 for FeO, to 40 ohm-1 cm-1 for a melt containing 26.3 pct CaO at 1400°C. The temperature coefficient was positive at all compositions, but became smaller at high CaO contents. Current efficiencies for electrolysis increased from 2.5 pct in FeOx to 17.3 pct at the high CaO composition, indicating a change from predominantly electronic conduction to conduction with a substantial ionic contribution. It was shown that Ca++ ions as well as Fe++ ions carry the ionic current. A subsidiary investigation on the apparent effect of atmospheres of argon, helium, and nitrogen on the electrical conductivity showed that this could be correlated with surface temperature losses, which varied with the thermal conductivities of the gases and resulted in precipitation of metal by the reaction 3 Fe++ = 2 Fe+++ + Fe. The work described in this paper is offered as a contribution to the general fund of knowledge concerning metallurgical slags. Measurement of electrical conductivity and electrolysis are comparatively trouble -free methods for investigating molten materials, but, although these methods had been used for complex slags, it was not until the work of Bockris et al.1 that the approach of examining simple binary slag systems was employed, and CaO-SiO2, MnO-SiO2, and Al2O3-Si9 were studied. Two groups have performed work of particular relevance to the present investigation. Inouye, Tomlinson, and chipman2 studied the conductivity of wustite as a function of temperature and of the addition of 5 mol pct of a number of oxides, including CaO. They concluded that molten FeOx in equilibrium with iron is a semiconductor. Simnad, Derge, and ceorge3 demonstrated the ionic nature of liquid iron silicate slags and also concluded that, although the conductivity of FeOx in equilibrium with iron is predominantly electronic in nature, there is a small ionic contribution. The work reported here on FeOx,-CaO slags consists of three main parts, namely, the determination of the specific conductance over a wide composition range, an investigation into the nature of the conductivity through current-efficiency measurements over the same composition range, and an attempt to identify the current-carrying ions, as well as a subsidiary investigation on the apparent effect of the nature of the inert atmosphere on the conductivity. EXPERIMENTAL Materials. The slags, varying in composition from FeOx to 27 pct CaO, were prepared by heating reagent- grade Fe2O3 in an ingot iron crucible with a suitable amount of CaCO3 and, in some cases, powdered iron, in air. This prefused material was then used for the runs. At the end of each run the cell was removed from the furnace and quenched by immersing the bottom half in water. After crushing, the slags were analyzed for calcium and total iron by the usual wet methods. The oxygen content was obtained by difference. Specific Conductance: Apparatus and Method. Fig. shows the experimental setup, with the conductivity cell and leads of ingot iron. The standard four-probe method for measuring high conductivities was used. In this, the potential drop across the unknown resistance is compared with the potential drop across a known resistance connected in series, i .e., same current through both resistances. Thus there are both current and potential leads to the center electrode and to the crucible, which acts as th other electrode. Both ac and dc circuits were available for the measurements; they have been described in earlier work performed in this laboratory.4,5 The geometry of the cell was such that the center electrode was equidistant from the bottom and sides of the crucible. This ensured that the current path was the same irrespective of the magnitude of the conductivity of the material in the cell. Cell constant were measured with KC1 or NaCl solutions, which have considerably lower conductivities (0.0013 to 0.25 ohm-&apos; cm) than the slags, and this precaution in design made sure that the determined cell constants applied to the cells with contents of any conductivity. The cell-constant determinations were made with the ac measuring circuit to prevent polarization. The four-probe method eliminates lead resistance but not the resistance of those parts of the center

Jan 1, 1967

By D. S. Tomalin, D. F. Stein

The effect of reducing oxygen to low concentrations on the fracture of high-purity iron single crystals has been examined at 78° and 20°K. It is found that iron single crystals grown by the strain-anneal method usually contain a few occluded grain boundaries which may become embittled in the presence of oxygen, thereby nucleating cleavage fractures. High purity with respect to interstitial elements was found to inhibit twinning and evidence is presented for an orientation dependence of the resolved yield stress. Deformation occurred by slip rather than twinning at both temperatures of testing with elongations of as much as 9 pct at 20°K. THE fracture properties of iron single crystals have been observedl-3 to be a function of temperature, orientation, and purity. Allen, Hopkins, and McLennan1 demonstrated that at 78°K iron single crystals became increasingly brittle as the tensile axis approached the (001) pole of the stereographic unit triangle. Iron crystals with the tension axis near a (001) pole were completely brittle and orientations near the (011)-(111) boundary were very ductile, achieving a 100 pct reduction in area prior to fracture. Later work of Biggs and pratt2 and of Edmondson3 demonstrated that by reducing the carbon content of the single crystals the transition between brittle and ductile failure at 78°K could be shifted to orientations nearer the (001) pole. Ed-mondson went further and pointed out that any mechanism which tended to increase the yield strength of the iron (i.e., carbon addition, pre-strain) also increased the tendency for brittle behavior at 78°K. Thus by a reduction of carbon content Biggs and Pratt were able to obtain ductile behavior to within 20 deg of the (001) pole, and Ed-mondson was able to obtain ductile behavior to within 26 deg of the (001) pole. Edmondson&apos;s material had a total interstitial content (carbon, oxygen, and nitrogen) of approximately 60 ppm and, although Biggs and Pratt reported no analysis, indications were that their iron contained comparable impurities. Stein, Low, and seybolt4 purified iron single crystals to a total carbon, oxygen, and nitrogen content of approximately 20 ppm. They observed a lowering of the yield stress with this increased purity, and thus one might have expected an observation of increased ductility. Although they tested specimens of orientations which the previous workers had indicated should be ductile, the crystals failed at a 78°K in a brittle manner with little elongation. Stein noted,&apos; however, that about 90 pet of the failures could be traced in origin to occluded grains. Allen et al.1 and Edmondson3 do not report examination of their cleavage surfaces, but Biggs and pratt2 reported that microscopic examination of the cleavage surfaces of many of their specimens revealed the presence of small occluded grains. Honda and cohen6 and Keh7 have also observed the initiation of fracture at occluded grains in iron single crystals. Therefore, the additional complication of occluded grains must be considered in studying the properties of iron single crystals and the origin of fractures determined if the ductility exhibited by the crystals is to be considered meaningful. Various investigators8-12 have studied the effects of impurities on grain boundaries in high-purity polycrystalline iron. Rees and Hopkins10 showed that the addition of oxygen to low-carbon (0.002 pet) iron weakened the grain boundaries, causing a shift from transcrystalline to intercrystalline fracture and a progressive decrease on the brittle-fracture stress with increasing oxygen content. In addition, it has been shown by Low and Feustel11 that the addition of carbon to polycrystalline iron containing oxygen eliminated grain boundary brittleness. Thus, oxygen can embrittle grain boundaries in high-purity polycrystalline iron, but the addition of an appropriate amount of carbon can eliminate the oxygen-induced brittleness. The oxygen content (19 ppm) of the iron "single crystals" employed by Stein el al. was large enough to suspect impurity effects at the occluded grain boundaries. Allen et al.1 Biggs and pratt,2 and Edmondson3 may have masked any occluded grain problem in their specimens considering the relatively high carbon levels they employed. stein13 demonstrated that the addition of as little as 0.9 ppm C to previously purified (less than 5 x 10-3 ppm C) "single crystals" would increase the elongation from a few percent to more than 20 pet at 78°K and the fracture was not associated with grade boundary initiation.

Jan 1, 1965

By G. A. Swanquist, E. M. Morales

INTRODUCTION The idea of water management and control at the Church Rock Mill operations began to take shape in February 1979. At that time, we were already investigating the feasibility of decreasing the fresh water requirements so that the solids would become the limiting factor in tailings impoundment utilization. The area for solution evaporation could be kept at a fraction of the normal requirements under the standard process of full water usage. The Church Rock Mill is an acid leach circuit followed by solids/liquid separation with thickeners in counter current decantation, and solvent extraction. Following the normal design of acid leach circuits, reuse of tailings solution was not incorporated in the original mill process design. INITIAL WATER CONTROL INVESTIGATIONS The investigations to decrease the fresh water requirements centered around modifying the grinding circuit from the present semi-autogenous grinding (SAG) mill in closed circuit with hydrocyclones, to open circuit grinding with a rod mill. The open circuit grinding with the SAG mill and rod mill in series had the potential of decreasing the water requirements for grinding and leach dilution by approximately 50% or 1.4 m3/min (300 gpm). The grinding pulp density would be maintained at 70 to 72% solids, and the leach dilution to 50% solids would be accomplished with acid tailings liquor recycle. In such a grinding circuit arrangement, the SAG mill would provide the primary or coarse grind, and the rod mill would be used for the fine grind. By the SAG mill and rod mill series grinding method of water control and other secondary water controls in various places downstream from the grinding circuit, the required necessary evaporation area was estimated at 120 acres of liquid surface. A second method of water control at grinding was investigated. A two-stage cyclone classification circuit appeared to have a good potential of achieving the same water reduction at a much lower capital and operating cost. However, in retrospect, this would not have been a viable method since a high slime recycle load would have been established hindering classification. The use of reagents to neutralize the acid tailings solution was not considered seriously at that time, since it would have materially increased operating costs, although it would have also allowed more tailings solution recycle and consequently, less fresh water usage. However, with the tailings solution deposition area available at that time, it was not then necessary to incur the high cost of neutralization. The control expected by the series grinding of semiautogenous and rod mills would have been sufficient to maintain a water consumption/evaporation equilibrium well in line with the available land area. IMPLEMENTATION OF NEUTRALIZATION OPERATIONS During the summer of 1979, the UNC Church Rock Mill experienced a tailings dam breach which resulted in a prolonged mill shutdown. Upon resumption of operations at the end of October 1979, tailings deposition was restricted to a small portion of the tailings impoundment area. Figure 1 shows the general tailings area and the limits of the present deposition area in the central part including the borrow pits. These borrow pits had been excavated to provide materials for tailings dam construction. Immediately after resumption of operations, it became evident that it would be necessary to control the quantity of liquid to be evaporated because of the small confined area available for tailings solution deposition and to maximize the deposition time in the tailings area. The water control required had to be exercised on a large scale, and to be in operation as quickly as possible. An obvious solution was to reuse the tailings liquor in mill process. Immediate steps were taken to install the necessary equipment for tailings neutralization on an interim basis. Anhydrous ammonia was selected as the primary neutralization reagent since it was the quickest system that could be placed in operation. Previous laboratory tests indicated fair results with ammonia neutralization. Such a system required a minimum of installed equipment and handling. INITIAL NEUTRALIZATION OPERATIONS Actual neutralization operations began on November 26, 1979. The raffinate solution which normally would have been discarded was pumped to a 3.7 m (12ft) diam by 4.3 m (14ft) tank for reagent contact, see Figure 2. At this tank, anhydrous ammonia was added directly from the tanker trailers and controlled at pH 7.0 nominally. Agitation was provided by air sparging. The neutralized product formed a highly viscous slurry in the grinding circuit which resulted in pumping and cyclone classification problems.

Jan 1, 1982

By M. H. Yoo

Possible interactions of the perfect dislocations of six slip systems or the c dislocation with the (10i2f (ioii), {ioIi}(ioiZ), {1122}(1123), and {1121}(ii26) type twins in hcp metals have been analyzed from the crystallographic and the energetic points of view. Twenty-six distinct types of possible interactions were identified, and those selected based on crystallographic constraints were examined for their energetic feasibilities by use of the anisotropic energy factors. No long-range elastic interaction exists for a dislocation when its Burgers vector is parallel to the twin interface. Under a suitable applied stress, a screw dislocation can cross slip at the twin interface. For basal mixed dislocations in cadmium and zinc, the interaction with {1012} twins is found to be attractive, indicating that incorporation of these dislocations into the twins is energetically feasible and that twin growth will result. On the other hand, the interaction between both basal and Prism mixed dislocations and the {1012} and (1121) twins is found to be repulsive in Mg, Co, Re, Zr, Ti, Hf, and Be. This indicates that under an applied stress a local stress concentration will develop due to a dislocation pileup at the interface, which may result in a site for either the nucleation of other twins or the formation of a crack, depending on the cleavage strength. WHEN a metal undergoes plastic deformation, a certain configuration of slip dislocations will result in a state of dislocation pileup against an obstacle. The stress concentration thus developed may enhance the process of twin nucleation and also twin growth. Furthermore, once formed and dispersed in the crystal, twins can act as effective barriers against slip dislocations. The degree of such mutual influence or interrelation between slip and twinning is generally known to be pronounced in the case of hcp, metals. It is also known that deformation by twinning occurs more commonly in hexagonal metals than in cubic metals. In fact, under suitable stress states, all hexagonal metals exhibit {1012) <1011> type twinning.&apos; In addition to this common type, deformation by (1151) <1126> type twinning occurs in zirconium, titanium, and rhenium, which show remarkable ductility.&apos; The importance of twinning during general deformation to the ductility of hcp polycrystals has been briefly discussed in recent review works.2&apos;3 The purpose of this paper is to analyze the interaction between slip dislocations and twins in the hcp structure and to discuss the nucleation and growth processes of twinning and the role of twinning in the <"°" noil) o, 1/3[112O] (OOO2) 1/3[1123] Fig. l—-Slip systems in hcp structure. ductility of hexagonal metals. The problem will be discussed from the geometric and the energetic points of view in a manner similar to that of the previous work on zinc.4 Since hcp crystals deform by several slip and twin systems, numerous interactions result as possibilities. The Burgers vectors of six slip systems and the c dislocation shown in Fig. 1 and the four twin systems listed in Table I are considered here. A complete tabulation of the possible interactions is followed by discussion of those that are more likely to occur on the basis of crystallographic constraints and energetic considerations. 1) CRYSTALLOGRAPHY OF TWINNING The crystallographic elements, K1, K2, n1, and n2, for the four compound twin systems are now well established.= A unit cell with the base vectors n1, and n2 is shown in Fig. 2 for each twin system. The unit cell before twinning is shown in solid line, and the corresponding unit cell after twinning is shown in dashed line. Also shown in Fig. 2 are the following crystallographic parameters: S is the plane of shear, d the interspacing of the twin habit planes K1,Ø Iis the acute angle between n1, and n 2, e is a numerical factor, and q is the number of K, lattice planes intersected by 17&apos;. These parameters can be expressed in terms of the axial ratio, y = c/a, as listed in Table 11. The macroscopic shear strain of twinning, s, and the magnitude of a "unit twin dis-l~cation,"4 bt, are also expressed in terms of y and given in Table 11. In Table 11, K1 and q1 are given in both Miller-Bravais and Miller indices. In double lattice structures, shuffling of atoms in addition to a homogeneous shear of the lattice is generally required if the original crystal structure is to be restored after twinning. The extent of current understanding on this problem of atom shuffling is per- Table I. Four Twin Systems in Hcp Structure

Jan 1, 1970

By R. M. Hudson, P. E. Perry

Weight-gain data obtained by nitriding low-carbon sheet steel in an amrnonia CNH,) atmosphere indicated that the process obeyed a parabolic rate law. The calculated actization energy for nitriding in the range 964" to 1268°F agreed reasonably well with published data. At 1358"F, rate data indicated that the activation energy decreased. Weight-gain data obtained by uszng mixtures of NH3 -Nz at 1268°F containzng jrom 10 to 100 zol pct NH3 also obeyed a parabolic rate law. The rate of &apos;nitriding increased with an increase in the NH3 content of the gas Mixture. It is well-known that steel heated in gas mixtures containing ammonia (NH3) takes up much larger quantities of nitrogen than steel heated in nitrogen, both gases having a total pressure of 1 atm;&apos; this phenomenon can presumably be attributed to the catalytic decomposition of NH3 on the steel surface to furnish nascent (monatomic) nitrogen. This process was studied bv Brunauer. Jefferson, Emmett, and Hend-ricks at furnace temperatures of 752" and 831°F2 using mixtures of NH3 in Hz. Englehardt and wagner3 reported that, at a furnace temperature of 914°F and under their experimental conditions, both nitriding and denitriding were controlled by the rate of gas-metal reactions at a steel surface rather than by the rate of diffusion of nitrogen in iron. The present study was undertaken to obtain information on the kinetics of nitriding low-carbon steel strip at higher temperatures so that practical rates for short-time strip-annealing treatments could be estimated. Variables studied included time: temperature, and NH, content in the annealing atmosphere. Mechanical and chemical characteristics of steel nitrided in this manner will not be considered in the present article. MATERIALS AND EXPERIMENTAL WORK The samples used were from a commercial low-carbon steel, 0.0244 cm thick, in the cold-reduced condition. The chemical composition of this steel is given in Table I. Panels were cut to 5.1 by 17.8 cm, degreased in toluene, and weighed just before treatment. Four specimens were nitrided under each of the experimental conditions. A study was made of the nitriding rate of steel in a 100 vol pct ammonia atmosphere, 740 mm pressure, at five specific temperatures within the range 964" to 1358°F. The nitriding rates of steel in ammonia-nitrogen gas mixtures containing 10, 18, 26, 50, and 100 vol pct ammonia, 740 mm total pressure, at 1268°F were also determined. All atmospheres used were dried by successively passing them through drying towers packed with soda lime and with Linde Molecular sieve Type 4A. Quoted gas compositions refer to those entering the furnace. Specimens were held in the constant-temperature zone of a vertical annealing tube furnace for times of 14, 3, 5, 10, or 15 min. Gas flow rates were maintained at 3.8 cu ft per hr, which was nineteen volume changes per hour for the system used. The rate of flow was selected to provide a high level of free NH3 for cracking on the steel surface where the ammonia gas is most effectively used as a nitriding agent. The vertical annealing tube furnace consisted of a Hevi-Duty tube furnace with a 2 1/2-in.-ID mullite ceramic high-temperature tube. The constant-temperature zone (controlled within 10°F) was about 10 in. long. After each specimen was degreased, a hole was punched in one end, for attaching the specimen by hook to a chain so that it could be lowered into or raised from the high-temperature portion of the tube by means of a power-driven winch. A stainless-steel access port with O-ring seals was connected by suitable glass-to-metal seals to the cool upper portion of the furnace tube. After the weighed specimen was placed in the access port, the furnace tube was evacuated to approximately 10"3 torr, and then the system was flushed thoroughly with the atmosphere under study. When the gas flow rate and constant-temperature zone of the furnace were established, the specimen was lowered into the constant-temperature zone. The atmosphere flowed from the top to the bottom of the vertical furnace tube and was then vented. For all these runs, during the first 3 min of the time the specimen was in the constant-temperature zone of the furnace the specimen was heating up to the tempera-

Jan 1, 1970

By Roland J. Lapee

A history of the progress made in copper refining in Montana is presented. The casting furnaces and the newly rebuilt electrolytic refinery are descmbed and operating details are given. Experiences with various addition agents, effects of rernoval of chlorine from the electrolyte, and effects of separan on electrolyte and on copper deposit are discussed. Observatzons are made on the effect of various impurities in anode copper and behavior of thezr salts in electrolyte and in slime, on treatment of slime for removal of copper, and on electrolyte puriification problems. The improved method for production of starting sheets is described. Attention is given to new materials for construction and to improvement in matrials handling ad quality control. COPPER refining at Great Falls, Montana, dates back to 1892. The original plant produced 65,000 lb. of cathodes per day at a current density of 16 amp per sq ft. In this plant anodes and cathodes were handled to and from the cells by means of hand-operated chain blocks and were moved about the plant by hand trucks. Cathodes were melted in coal-fired, reverbera-tory furnaces, were charged by hand, and refined copper was dipped by hand and cast in iron molds. In 1916, a new, modern plant with capacity to refine 18 million Ib. copper per month was built. Two refining furnaces were built, and each was provided with a twenty-mold Clark casting wheel. In 1922, the furnaces were converted to the use of pulverized coal: in 1923, to the use of oil; and in 1928, to the use of natural gas. In 1926, the plant was enlarged 50 pct. The use of pulverized coal for refining copper at Great Falls was discussed1 in a paper presented at the Salt Lake City meeting of the Institute in September 1925. Also, a comparison of the use of various fuels in copper refining furnaces was discussed 2 in a paper presented at the New York meeting of the Institute in February 1932. Prior to 1943 the cellroom was operated with twenty-five 720-lb. anodes and 26 cathodes per cell. Four cathodes, each weighing about 165 lb., were produced from an anode. In 1943 the weight of the anode was reduced to 460 lb., and two cathodes, each weighing about 190 lb., were produced from an anode. In 1949, a Billet Casting Wheel for the production of 3 in. diam phosphor deoxidized billets was built. A paper, presented at the New York Meeting of the Institute in February 1956, describes3 this plant and operation. In the electrolytic refinery, production is controlled by variation of the current density. In 1956, germanium rectifiers on a separate electrical circuit were provided for the starting sheet section so that current density could be maintained at any desired figure. Also in 1956, a program of modernization and enlargement of the Electrolytic Copper Refinery was started. This program, when completed, will raise the capacity of the Great Falls Electrolytic Copper Refinery approximately 33 pct, to 33 million lb. of cathodes per month. Furnace capacity for melting cathodes and anode scrap is ample to take care of the increased production from the electrolytic refinery. This fortunate condition came about primarily as the result of the three following changes: 1) The furnaces were lengthened 10 ft in 1922 when the fireboxes were found unnecessary for burning powdered coal. 2) Furnace life, and hence furnace capacity, was increased by the successful efforts of the Copper Refinery staff to develop a method for sanding furnace side walls and roof. 3) The natural gas being used has a very low sulfur content. As a result, it is possible to reduce time spent rabbling and poling and thus greatly increase tons per furnace charge. TANKHOUSE AND TANKS The Great Falls Electrolytic Refinery is 535 ft long by 252 ft wide. The cells are arranged in four crane bays in which are operated seven 10 ton Whiting Cranes. The old cells are in groups of ten, with circulation of electrolyte through five cells in cascade and with aisles between the groups of ten cells. The new cells are nested in groups of sixteen with no aisles, are all on one level, and have individual circulation to each cell. Present plans call for 1792 commercial cells and 128 stripper cells. To reduce confusion during the construction period, and to use the cranes, cars, and other equipment already on hand, the cells in the rebuilt section were designed to have approximately the same inside dimensions as the cells in the old part of the

Jan 1, 1962

By W. J. Schuster

Safety in coal mines depends largely upon adequate training of the foreman. Although management must provide modern and safe equipment and at all times keep mines in first class condition from a safety viewpoint, final results will be determined by the quality of supervision. HANNA COAL CO., Division of Pittsburgh Consolidation Coal Co., operates three large underground mines in eastern Ohio. The section of Pittsburgh No. 8 coal seam in which these mines are located varies in thickness from 52 to 64 in. It is immediately overlain by a stratum of shaly material 12 to 15 in. thick locally known as draw slate, which is structurally very weak and which disintegrates rapidly upon exposure to atmosphere. Immediately above the draw slate as it is normally found is a band of extremely high ash material 6 to 12 in. thick known as roof coal or rooster coal, and above this is a stratum of conglomerate material varying from 4 to 10 ft in depth. Overlying the conglomerate is a relatively thick stratum of limestone, the first stable material above the Pittsburgh coal seam in eastern Ohio. With the method of full-seam mining that has been adopted, draw slate is shot down, loaded with the coal, and removed in the preparation plants. The roof coal then becomes the permanent roof. The major problem in mining the No. 8 seam in eastern Ohio is control of the roof. Since the strata above the draw slate contains no material with a structure firm enough to provide self-support, the roof begins to sag in a relatively short time after the coal and draw slate have been removed. The problem thus becomes one of getting temporary safety posts under this roof as quickly as possible to prevent a break or separation from occurring either in the roof coal or in the conglomerate above it. Haulage System The Pittsburgh No. 8 seam in eastern Ohio is relatively level, with only minor local dips. Throughout the Hanna Coal Co. mines, entries are generally 12 ft wide. Rooms are driven on a 60" angle on 30-ft centers and are 22 ft wide. No attempt is made to extract the 8-ft pillars between. The entire length of main line haulage is gunited in one mine, and a major portion in another. Two of the mines have single-track main haulage roads with passways. The third, a new mine, is double-tracked, and the roof is supported by steel crossbars, 60 lb or heavier, spaced on 4-ft centers and lagged. In recent years timbering on main line and secondary haulage roads has been accomplished by one of two methods: 1—crossbars are supported on a small section of post set in a hitch hole in the rib, or 2—or a hole is drilled in the rib about 12 in. below the roof, of sufficient depth to fasten securely a short length of 40-lb rail, the bottom of the rail facing the roof, on which a short post is set directly under the crossbar. At present the hitch-hole timbering method is favored. At two of the mines the main line haulage locomotives are 26-ton, 8-wheel units. These locomotives are of the axleless type, each wheel being individually mounted on the frame. The motorman&apos;s compartment is encircled by 3-in. armor plate for the protection of the occupants. At the third underground mine conventional 15-ton locomotives are being used. However, these locomotives have been completely rebuilt in the company&apos;s shops. Equipment has been streamlined and quarters have been provided for two people, who are protected by heavy steel plate in much the same way described above. This modernization program has been completed on all secondary haulage locomotives at the three mines, and the company is well on the way to similar equipment of the 6-ton section locomotives. The following additional features have been included in their modernization: 1—additional support for the motors to prevent their falling to the middle of the track and derailing the locomotives should a break occur in the suspension bar support; 2—installation of additional bracing to prevent brake rigging from becoming displaced and causing derailments; 3—enclosure of all electric wiring in conduit or raceway; 4—provision of an enclosed compartment for the storage of re-railers, jacks, and other equipment, so that they need not be carried on the outside of the motor; and 5—redesign of the end of the locomotive opposite the operator&apos;s compartment to prevent anyone&apos;s mounting from that direction. It is interesting to note that some

Jan 1, 1955

By G. B. Misra

While investigating on the aerodynamic resistance of airways supported with peripheral timber sets, at regular intervals, the following theoretical equations were developed by the author to estimate the resistance coefficient of such airways: [ ] for S < 1, where f is Darcy-Weisbach resistance coefficient of the airway, C is modified drag coefficient of the supporting member, D is equivalent diameter of the bare airway, 8 is ratio of the approach velocity over the sets to the average velocity of the bare airway, A is cross-sectional area of the bare airway, a is projected frontal area of the sets, A., is cross-sectional area of the air stream at the vena contracta inside the set, S is spacing of the sets, f, is resistance coefficient of the bare airway, l is length of aerodynamic influence of sets, p is perimeter of the bare airway, p, is setted portion of the perimeter of the bare airway, pe is unsetted portion of the perimeter of the bare airway, and P shielding factor. The equations were verified experimentally in a model rectangular airway supported with one- (bars), three-, and four-piece sets of square-section timber of three different sizes and were found to hold true. The work has been further extended to one-, three-, and four-piece sets of round timber of 2.6, 3.2, and 3.8 cm diam with the same experimental set up. Tests have been carried out for spacings of 25, 50, 75, 100, 150, and 200 cm over a regime of flow defined by the Reynolds number (with respect to the equivalent diameter of the bare duct) ranging from about 1.5 X 106 to 5 X 106 using the same experimental techniques. The values of f are calculated in the manner indicated in [Ref. 1]. Unlike with square-section timber, the resistance coefficient f of the airway setted with round timber shows a distinct variation with the Reynolds number of flow. This conforms to observations made by Sales and Hinsley.2 In order to have a comparable value of f for all types of sets with all sizes of timber, it was necessary to select the value of f at a fixed Reynolds number of flow. Since f is chiefly a function of the drag coefficient of the sets, the appropriate Reynolds number RE is that with respect to the diameter of timber in the set. Considering the diameters of timber used and the regime of flow over which measurements were made, f was chosen at a value of RE = 20,000 in all cases. The f vs. S curves are maximal in nature and in conformity with theory, the f vs. 1/S curves are straight lines up to a value of S = 1 beyond which they show a distinct flexure. The observed values of 1, the length of aerodynamic influence of sets, agree with the relation 1 = 42 e, developed for square-section timber sets, thus suggesting that the shape of timber has little influence on the length of aerodynamic influence. The value of the modified drag coefficient CD for round timber was calculated in the same way as for square timber in Ref. 1, taking the contraction factor Z = 1.5 for round-edged constrictions. CD has an average value of 0.96 with a standard deviation of 6.08% as compared to the free stream drag coefficient of 1.2 at RE = 20,000 for long cylindrical obstructions The shielding factor [ ] is plotted against S/1 in [Fig. 1]. The curves are more or less independent of the size of timber, but are different for the different types of sets, possibly due to their different degree of symmetry. Values of f calculated by the author&apos;s [Eqs. 1 and 2], using experimental values of CD&apos; and [ ] and taking I = 42 e, are plotted in [Fig. 2] against experimentally measured values of f for different types of sets with different sizes of round timber. The values agree closely with a standard deviation of only 5%, thus establishing the veracity of the theoretical equations developed by the author for round timber as well. A comparison was made between the Xenofontowa4 equations (the only other reasonable relations available for the estimation of the resistance coefficient of supported airways) and the author&apos;s [Eqs. 1 and 2] by comparing in [Fig. 3] the values of the resistance coefficient f computed by the Xenofontowa relations with those experimentally measured by the author. In order to make

Jan 1, 1975

By Carle R. Hayward

WHEN lead production began to recede from the peak productions of 1929 many plants took advantage of the curtailed operations to make necessary improvements and repairs about the plant. There followed a period of adjustment to synchronize production and demand, which merged in the present period of marking time. The lead smelting and refining industry has produced little that is new during the past year except in what might be called makeshifts, which have been introduced to make operation at fractional capacity profitable. This is more particularly true in refineries than in smelters. The Parkes process had become standardized during the period of normal production, with softening, desilverizing, and dezink-

Jan 1, 1935

[MUNOZ, P.: New Oil Fields in Trinidad, M27, 311 MUNRO, C. H., biography, M84, 354 MUNROE, H. S., biography, M83, 277 Muntz metal (See also 60:40 Brass): corrosion. See Corrosion of Metals. fatigue and corrosion-fatigue, 78, 597 heat-treated: cleavage structure, 83, 498, 505 grain growth, abnormal, 83, 503, 505 machinability, 99, 323 stress-corrosion cracking, 89, 249. 266 MURAKAMI, T.: iron-silicon diagram, 80, 253, 255 MURDOCH, J. A. W., biography, M28, 157 MURDOCK, W. J.: Discussion on Adaptability of Various Coals as Generator Fuel in Manufacture of Water Gas 78, 561, 565, 566, 568 MURPHY. D. W. AND CHIPMAN, J.: Solubility of Nitrogen in Liquid Iron (T.P. 591) 116, 179. Abs., YB35, 33; M35, 114 MURPHY, L. J.: Relative Advantages and Costa of Electric Power in Lease Operations 77, 219]

Jan 1, 1936