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By Blamey Stevens

(San Francisco Meeting, October, 1911.) My previous paper is entitled, The Laws of Igneous Emanation Pressure. The present paper lays no claim to the exactitude and completeness of a law, since it is of a provisional nature and may be disregarded when experiments have established a basis for more exact reasoning. The general physical states in which aqueous emanations may occur are first considered. The possible physical conditions under which the mineral elements may occur in emanations are then discussed, and a classification of deposits, dependent on emanation, is proposed. A system of scientific experimental investigation is outlined, and it is shown that the physical and chemical properties of emanation may be exactly determined thereby. The investigation is urged as feasible and simple, and not necessarily requiring large and costly apparatus. It is the only step necessary to make possible the formulation of a complete set of laws of igneous emanation. Process of Emanation. In a rising column, magma ranges in temperature from 900° to 1,200°C. Exhalation must begin at some fairly great depth. What this depth may be we can only surmise, since no experimental evidence is available. Exhalation, however, continues as the magma flows upward, until at another level the occluded gases have all escaped. This depth is probably upward of 5,000 ft. (See Fig. 1.) All exhalations must come from between these two levels. As the whole emanation is the sum of the exhalations and residues, the residues must come from below the uppermost level. They will be most abundant when coming, from those parts of the intrusion which have solidified below the lower level.

Apr 1, 1912

By HARRINCTON EMERSON

UNEMPLOYMENT is the most ominous shadow ahead of the industrial nations today. Only two great industrial countries are free from unemployment, France and the Soviet Commonwealth. In France the social unit is the family, not the individual. This has saved France. In the Soviet Commonwealth, development is proceeding so rapidly from agricultural to industrial that there is still a dearth of muscle workers in the non-agricultural enterprises. In the other industrial countries unemployment results both from acute temporary recession in industrial activities and from the rapidly increasing substitution of the machine for the man. Temporary recessions can be mitigated, alleviated by makeshifts, often ill considered. Secular recessions due to a fundamental change in the way of accomplishing physical, chemical results cannot be cured by any makeshift. There must be a period of transition. There is therefore before us the three- fold problem, immediate, prosimate and ultimate.

Jan 1, 1930

By W. F., Dietrich

THIS paper deals with the- methods of mining the high-grade clays of California. Although the majority of the clay pits in the state are operated on a scale that is small by comparison with most metal mines, this very fact results in a diversity of methods and gives rise to problems of selection of the method best suited to given conditions. Two or three operators in California produce approximately 500 tons per day of a single kind of clay from a single pit. About five varieties of clay are mined on a scale of 200 to 400 tons per day; not over fifteen varieties are mined on a? scale of 50 to 200 tons per day; and more than 50 varieties are mined at a rate of less than 50 tons per day. It is the aim of this paper to delimit, insofar as the data at hand permit, the conditions and scale of operations that favor the selection of each dominant method of mining that is actually being applied at California properties. Details of the occurrence and utilization of the clays of California have been given in a recent bulletin and are not considered here.

Sep 1, 1928

By P. G. Shewmon, J. Y. Choi

The surface-diffusion coefficient for , has been measured on (111) and (100) surfaces of copper from 1000" to 620°C. D,(Ge) on the (111) is two to three times that on the (100) as was found earlier for copper and gold on copper. D, (Ge) on both (111) and (100) is about thirty times that found for gold or copper tracers on the same surfaces, while in the temperature range where both D,(Ge) and Ds(Au) have been measured the activation energy for germanium is the same as that for gold. The apparent activation energy for Ds(Ge) is not a constant, but decreases with temperature. In a recent paper we reported on the application of a new tracer technique to the determination of the surface-diffusion coefficient (D,) for gold and copper on (111) and (100) surfaces of copper.' In this paper, we shall give the results obtained when the same technique was used to measure Ds for germanium on the (111) and (100) surfaces of copper. In addition to providing data on D., for an additional element on copper, the longer half-life of germanium (275 days) meant that Ds could be measured down to a much lower temperature and thus over a much wider temperature range (1000" to 620°C) than was used in our gold-tracer work (1060" to 780°C) or copper mass-transport studies (1060" to 800). The apparent activation energy for D, (Ge) is essentially the same as that found for gold or copper in the same temperature range, though the values of D, (Ge) are thirty times greater than those found for gold or copper tracers. The most interesting new result found is that the apparent activation energy for Ds(Ge), and thus Do, definitely increases with temperature. Such a trend was much more apparent in Gjostein's mass-transport work on copper than in our own, though in an earlier paper we mentioned the difficulty of fitting all of our points with one straight line:= No real explanation of this is given though experiments done on grain boundary groove growth at various ambient pressures demonstrate unequivocally that vapor transport plays no part in the increase in activation energy with temperature.

Jan 1, 1964

By AIME AIME

LAST month we published (p. 440) the first half of the L discussion by O. E. Kiessling of the paper on copper by Mr. Vogelstein that appeared in the same-issue, but lack of space made it necessary to hold the remainder for this number. Mr. Kiessling now asks to have the last " sentence of the part already published revised to the form given in the first sentence which follows, and also asks that the two parts, though necessarily published separately, be read together, as a mistaken impression may be derived from the first Dart unless it is read in connection with the statement of the Bureau of Mines policy respecting secondary metals which is here published. .

Jan 1, 1931

By James P. Sloss

WHAT is the likelihood if any-that a real gold mining industry will be developed in the southern Appalachian region? Has the increase in the dollar value of gold from $20.67 to $35 per ounce potency to turn the trick? Suppose it be assumed that the price of gold will, at worst, not recede, and that the cost of digging ore and treating it of which the average level of commodity prices and wages is a fair index-will, at most, not exceed that prevailing in 1926. One may or may not accept these as reasonable assumptions; but one must arbitrarily remove some of the potential variables if one is to get anywhere on a problem like this. As a matter of fact, this article is not going to venture a conclusive answer to the question that has been posed; but it will endeavor to present some of the factors that have a bearing on the problem. The writer spent ten days visiting a dozen properties in Virginia and the Carolinas early in April, 1935, and in doing so got a first-hand slant on mining conditions in the domain of King Cotton.

Jan 1, 1935

By J. L. Huitt, B. B. McGlothlin, D. K. Lowe

Published correlations for the principal aspects of hydraulic fracturing were combined into a digital computer program to facilitate the study of interrelated variables. The computer program includes individual relationships for fracture width during pumping, fracture area generated, propping agent embedment, flow capacities of propped fractures and transport of propping agents in horizontal fractures. The effects of more than 20 treatment and formation parameters on the predicted results of hydraulic fracturing treatments were studied. The effects of these parameters were determined for (I) fracture width during injection, (2) fracture width after the overburden comes to rest on the propping agents, assumed not to be crushed, (3) generated and propped fracture area, (4) location and concentration of propping agents in the fracture when injection ceases, (5) flow capacities of the various propped sections of the fracture and (6) expected increase in the well productivity. The effects of propping agent, formation and fracturing fluid parameters on well productivity are discussed. The parameters that were found to have the most pronounced effects on hydraulic fracturing treat~nents are injection rate, treatment volume, fracturing fluid coefficient, size and amount of propping agent, spearhead volume, well drainage radius and formation capacity. INTRODUCTION Many correlations have been published for predicting effects of various parameters that are considered in the design of hydraulic fracturing treatments. The Carter equation' can be used to predict generated fracture radius as a function of fracture width, fracturing fluid leakoff and other parameters. Fracture width can be determined by use of the Perkins and Kern correlation' in which the fracture width is related to the fracture radius, fluid injection rate and certain formation and fracturing fluid parameters. Wahl and Lowe et aL4 have reported methods of predicting the location of propping agents in fractures when pumping ceases. The former study is applicable to the case where the ratio of propping agent diameter to fracture width is less than 0.1. The latter is applicable when this ratio is greater than 0.1. These studies showed that the propping agent placement in horizontal-radial fractures depends principally on how the individual particles are transported in the fracture by the carrying fluid. Particle transport in fractures is determined by local fluid velocity in the fracture, fluid and particle properties, and the size of the particle relative to the fracture width. The distribution of propping agents, effective overburden pressure and formation rock strength control the propped fracture width6 by controlling the extent to which the propping agent particles embed into the fracture faces. From the distribution of propping agents and the propped fracture width, fracture flow capacities can be calculated or the various regions of the fracture. The flow capacities and the radial extent of these regions can be combined with reservoir information to predict the productivity increases for fractured wells. In all these studies, the effects of certain treatment and/ or reservoir parameters on one facet of fracturing can be predicted only if other facets which the parameters affect are fixed. For instance, fracture width and radius are interrelated; that is, to calculate the value of one, the value of the other must be known. Also, some parameters influence more than one aspect of fracturing. For example, prop-pant transport is a function of both fracture width and fluid viscosity. but fracture width is itself a function of fluid viscosity. Since these calculations are complex and the parameters interrelated, it is not possible to write an equation with which the over-all effects of treatment parameters can be solved explicitly. For these reasons, the correlations for determining the effects of the parameters which are most significant in hydraulic fracturing treatments have been incorporated into a digital computer program. COMPUTER PROGRAM The program, which was written for an IBM 7094 computer, can be used to predict results of most of the combinations and values for the treatment parameters that are ordinarily considered for fracturing treatments. A spearhead of fracturing fluid and a propping agent-carrying fluid with different fluid properties can be taken into account. Also, the total volumes and relative amounts of the spearhead and carrying fluids can be varied. Two different propping agents (as used in tail-in operations) and a wide range of formation properties and injection rates are considered. The computer program (Fig. 12) consists of several sets of calculations. First, the final flooded fracture radius and average fracture width at the cessation of pumping are calculated. This is done by simultaneous solution of the Perkins and Kern fracture width equation and the Carter equation for flooded fracture radius (equations used in the computer program appear in the Appendix). The next step is to determine local fluid velocity in the fracture as a function of time and radius. Since it is not possible to write this function in closed form expression, a table of velocity values is generated by the program and stored for subsequent use. The time span from the beginning of

By A. J. Weinig

THE Liberty Bell cyanide precipitate is unique in that it is apt to vary widely in composition in the course of very short, periods of time, and a method of refining and melting that would prove highly satisfactory at one cleanup would yield almost an hopeless "mess" it a second. Table I gives a general conception of the wide range in grade and composition of those raw precipitates. It is evident that no one standard flux could be expected to produce a high-grade bullion with such a widely variable precipitate, and that any method of treatment with acid requires most careful consideration. Refining by Acids Naturally, our first efforts to improve our precipitates were directed along the lines of acid treatment. Table II embodies the results of careful sampling and analysis of one cleanup at the time when wet refining reached its maximum development at this mill. We have now discarded all methods of wet refining, successfully replacing them by amore scientific method of flux calculation described herein, but it is believed that a general description of this wet refining is warranted as it throws some interesting side lights on acid refining in general.

Jan 3, 1916

By Finney, W. R.

MUCH has been said and written of the "Big Inch," of the terrific obstacles encountered in its construction, of the colorful and tough men engaged in its building, but little has been publicized of the engineering and economic problems behind the scenes. Long before Pearl Harbor it was apparent to the petroleum industry that a critical oil shortage could be expected along the Atlantic seaboard, owing to delay in tanker deliveries as a result of convoy movements, and to allocation of vessels for foreign shipments. This area, with a normal consumption of approximately 1,800,000 barrels per day of oil and products, was almost entirely supplied by tanker. Pipe lines supplied an average of only 20,000 barrels per day in 1939, 40,300 barrels per day in 1940, and 55,000 barrels per day in 1941. A small amount of oil and products was also delivered via barge.

Jan 1, 1943

By K. E. Brown, F. W. Jessen

By utilizing an 8,000-ft experimental field well equipped with 10 gas-lift valves and 10 Maihak pressure recorders, gas-lift tests were conducted with port sizes ranging from 5/16 through I in. The well was equipped to provide accurate means of measuring surface pressures, temperatures, quantity of injection gas and fluid production. The tests were conducted in 2%-in. OD tubing, and the well was making 95 per cent water. A complete evaluation of gas-lift-valve port sizes shows the relationship of per cent recovery, gas-liquid ratios, minimum pressure created at the operating valve and horsepower requirements for each port. The length of time necessary for the fluid in the tubing to reach equilib.rium conditions after each cycle was recorded. Fallback of fluid at depths of 477, 969, 1,685, 2,493 and 4,290 ft was noted. For each port size, pressure loads of 2.50, 300, 350, 400 and 450 psi were lifted with a valve operating at approximately 550 psi at 6,000 ft. Gas-liquid ratios for each load were varied from excess gas to a gas volume per cycle whereby the load failed to reach the surface. Numerous curves are presented in evaluating the accumulated dara. The results show a 1-in. port to be the most efficient under all conditions. The production of intermittent liquid slugs against different-sized surface chokes was evaluated. These tests were conducted from a 7/16-in. ported valve at 4,072 ft. Tests indicate that, when possible, a %-in. in diameter choke or larger should be used at the surface. In the past few years most of the advancement in gas-lift operations has been made in continuous-flow operations. Yet, it is estimated that at least 70 per cent of the wells on gas lift in the United States are of the intermittent type. Since the term "slug flow" is sometimes used in both intermittent- and continuous-flow operations, it would be well to distinguish between the two types of flow. Continuous-flow gas lift is defined as a method whereby the fluids are produced at a continuous rate at the surface. This generally requires a continuous injection of gas through a surface choke; however, various other control devices sometimes are installed to eliminate freezing, to shut-off gas during natural flow periods, etc. The actual flow of fluids in the tubing may be of the slug type (one of many flow patterns known to exist in continuous flow). Intermittent flow is defined as a method of gas lift whereby the liquid is produced in separate piston-type slugs. Perhaps this type of flow could best be thought of as a ballistic-type flow where the liquid leaves bottom as a piston, propelled by a slug of expanding gas. Gas generally is injected through some type of control at the surface at predetermined intervals. However, the valve may have characteristics whereby gas can be injected through a small choke and still result in a ballistic-type flow. The purpose of the experimental work was to evaluate the most efficient port size to be used on the operating valve for the ballistic type of lift and, in addition, to establish the importance of utilizing a surface choke large enough to allow slugs to be produced without detrimental effects. This work is part of a compre- hensive study of both intermittent-and continuous-flow gas lift, representing a joint project conducted by the Ohio Oil Co., the Sun Oil Co., Otis Engineering Corp, and The U. of Texas. The problem of evaluating port sizes has been given little previous attention. Some work undoubtedly has been done which has not been published to date. Some tests were conducted when the wireline, mechanically-opened valve (Nixon) first came on the market. This valve was capable of utilizing full tubing area as its port size. It is known that this was a very efficient valve, but to the authors' knowledge the results of tests have never been published. EXPERIMENTAL EQUIPMENT These tests were conducted on an actual field well, the Ohio-Sun Unit Well No. 2-E, in the North Markham-North Bay City field, Matagorda County, Tex. The well incorporated 23/8-in. OD tubing and produced 95 per cent water. Since the running of equipment was to be quite elaborate and expensive, a well was selected in which both intermittent- and continuous-flow tests could be conducted. This particular well was capable of producing in excess of 1,000 B/D of liquid (95 per cent salt water), yet with a 3/64-in. in diameter bottom-hole choke, production was controlled to 82 B/D. Most of the intermittent tests were conducted at this low rate. Figs. 1 and 2 show all the surface and down-hole equipment. As can be seen, every attempt was made to insure that ample equipment was available for reliable testing procedures. Fig. 1 shows the surface testing equipment. The input gas was controlled first by a regulator, then

By A. Lubinski, W. D. Greenfield

Bumper subs are currently used in offshore operations to permit a constant weight to be carried on the bit while drilling, regardless of the vertical motion imparted to the drill pipe by drilling vessel heave. As shown in this paper. the vertical motion of the lower end of the drill pipe (the bumper sub end) may be appreciably greater than the vessel heave. Therefore, the necessary stroke of bumper .rubs for successful operation is greater than thought in fie past. Also, there is an appreciable tendency of the drill pipe to buckle above the unbalanced type of bumper sub. Thus, more drill collars than previously used should be carried above unbalanced bumper subs to keep drill pipe straight. INTRODUCTION Drilling bumper subs are placed in the drilling string for various reasons. This paper is concerned with their use only as an expansion and contraction joint while drilling from a floating rig. In this application the bumper subs are normally located just above the drill collars and their function is to allow the driller to maintain accurate weight control on the bit regardless of up-and-down movement of the drilling vessel. This paper analyzes the effects of bumper subs on the drilling string and presents recommendations for their future use. When subjected to vertical oscillations, the drilling string behaves like a long, distributed system of mass and spring. The magnitude of vertical motion at the bumper sub is always greater than the heave of the drilling vessel due to the dynamic reponse of the drilling string. The ratio of these motions increases with the length of the drilling string, and may reach values of 1.5 or even 2 with strings 16,000 ft long. Thus, the total travel required in bumper subs can be considerably more than the motion of the drilling vessel. Lack of knowledge of this fact could have contributed to problems previously experienced with bumper subs. This fact can also lead to fatigue problems in the drilling string for very deep wells. Satisfactory operation should be obtainable whether hy-draulically balanced or unbalanced bumper subs are used in the drilling string. Theoretically, the balanced sub is preferable since its use does not require placing drill collars above the bumper sub to prevent drill-pipe buckling, an inherent characteristic of the unbalanced bumper sub. The current method of calculating weight of drill collars required to prevent helical buckling of drill pipe above unbalanced bumper subs is erroneous. Placing drill collars above the sub to prevent drill-pipe buckling has the same effect on dynamic response as increasing the length of the drilling string by an equal weight of drill pipe. Thus, total travel required in the subs is increased. Means for calculating the correct weight, which is much greater than previously thought, are given in this paper. BALANCED VS UNBALANCED BUMPER SUBS A drilling bumper sub is essentially a telescopic joint capable of transmitting torque at every position of its stroke. Thus, it allows the operator to isolate the weight of the drilling string from the weight of the drill collars above the bit. This permits the driller on a floating rig to maintain accurate control over the weight on bit — a control that is unaffected by vertical motion, due to wave and tide action of the drilling vessel. UNBALANCED BUMPER SUBS The unbalanced bumper sub is simply a splined tele~copic joint (Fig. I). Ordinarily, this arrangement will operate satisfactorily, but the presence of drilling fluid under pressure results in a pressure force that acts downward on the drill collars and bit, tending to open or extend the bumper sub. This downward force is equal to the pressure drop across the bit times the area indicated by diameter d2 in Fig. 1. Denoting this force by Fd, and the pressure drop across the bit by ?p yields Fb = (p/4)d22(?P) .........(1) There is also an upward-directed force given by Fu = (p/4) d22-d21)(?p) .......(2) which puts the drill pipe immediately above the bumper sub in compression, resulting in helical buckling. However, buckling is actually more severe than expected in that buckling occurs as if the compression were equal to Fd, rather than to Fu. This surprising phenomenon is well known as far as tubing is concerned;1-3 but, in contrast with the case of tubing, this force may shorten drill pipe only a few inches. Thus, this cannot explain the operating difficulties that sometimes have been encountered. However, having the drill pipe in compression and helically buckled is contrary to current practice; therefore, drill collars whose weight in mud is equal to the force Fd should be added above the bumper sub. Since the value of Fd depends on the pressure drop across the bit, the

By LESTER W. STRAUSS

OUR early knowledge of history and geography attracted most of us to the mineral resources of South America. The romantic tales of the Spanish activities, which were curiously alluring, and Prescott's exceptional bi-Conquest histories-Mexico and Peru-no doubt fired our minds with the .then metallic wealth of the Spanish colonies. Later developments, intensified within the past eighty years, have, however, changed its fame which now rests on such metallics as copper and tin, and among the non-metallics on nitrate of soda and petroleum. South America proper, excluding Panama, is made up of thirteen countries, a coincident parity with our original thirteen States. Its area is given as 7,231,300 square miles, or slightly less than North America (8,037,000 square miles), is made up as follows:

Jan 1, 1930

By Paul A. Taylor

MUCH information concerning pegmatites which was thought to be true a few years ago has been proved false, and what is now actually known about some pegmatites is not true of many others. The erratic and seemingly unpredictable structure and variable composition of this class of mineral deposits has been widely emphasized. Even parts of the same pegmatite body exhibit marked differences in texture, mineral composition, width, and attitude. Constructive geological thinking in respect to pegmatites now aims to establish general laws rather than to stress the confusing diversity of features having no special economic significance. Substantial progress has been made in classifying different types of these deposits according to general features, internal structure, mineralogy, and origin. In some cases it has even been possible to block out tonnage reserves in advance of mining. It is still easy, however, to make highly erroneous predictions after a preliminary examination of a pegmatite prospect. Pegmatites are important to the economic well being of the country and to its military security. They furnish virtually all the feldspar, strategic mica, beryl, columbium, tantalum, and caesium utilized in the United States, as well as sundry other minerals and significant amounts of lithium and rare earth minerals and gems. With the exception of vermiculite, occasional ilmenite-rutile, and perhaps soda-lime feldspar and garnet deposits, basic pegmatites are of little economic importance. Consequently in this paper, as in common parlance, the term pegmatite generally relates to coarsegrained acidic rocks or what is aptly called giant granite. Available data indicating the size and importance of the production and trade in specified pegmatite minerals are summarized in Table I. Geological Features Much of the latest thinking on the economic geology of pegmatites is now available in a 115-page monograph' by a group of experts who participated with geologists of the Federal Geological Survey in the widespread wartime investigations. Doubtless the most significant feature of the monograph is indicated by the title, The Internal Structure of Pegmatites, but it also contains a vast amount of other new information and includes the assimilated concepts of many earlier writers, whose works are given in a comprehensive list of references. The shape, size, attitude, and continuity of many pegmatite bodies is controlled by the structure of the older rocks in which they occur. If the older rocks are easily penetrated, e.g., biotite schist, most of the pegmatites in a given district will be found outside the parent granite mass as exterior pegmatites. Marginal pegmatites are more prevalent if the older rocks are massive, unsheared, and sparingly jointed. Networks of pegmatites are abundant in highly-jointed rocks. In strongly foliated schists the bodies are usually lenticular, whereas in highly-folded areas they assume tear drop, pipe or pod-like, bow-shaped, or sinuous forms. Jahns2 recognizes five major shape classes: l—dikes, sills, pipes, and elongate pods; 2— dikes, sills, pipes, and pods with bends, protuberances, or other irregularities; 3-—trough-or scoop-shaped bodies with or without complicating branches; 4—bodies with the form of an inverted trough or scoop; and 5—other bodies, including combinations of the above and miscellaneous shapes. Many pegmatite deposits are scarcely big enough to be recognizable as such. Most of them, in fact, are small tabular deposits less than 4 in. wide and usually without economic concentrations of minerals. On the other hand, some pegmatites are more than a mile long and over 500 ft wide. The ratios of length to breadth range from 1 : 1 to 1 : 100. Although the vertical dimension bears no invariable relationship to strike length, tabular deposits or large lenses are often symmetrical enough to show nearly as much continuity down dip as in their horizontal extension, and some pipes or pods are amazingly persistent in the vertical plane. Small pegmatites often string along a fairly definite trend line; in a given district major bodies may lie roughly parallel, and where only a few of them do not, the erratically disposed bodies generally differ in composition from those conforming to the regular pattern. This does not apply, however, in all districts. Characteristically, pegmatite veins pinch and swell or split into branches. When they pinch out entirely it is often possible to find a new body by prospecting the extension of the strike or dip, but the chances of finding a hidden deposit are ordinarily too uncertain to justify much subsurface prospecting. Diamond drilling may yield valuable information as to the continuity of known deposits whose upper portions are well-exposed. Some deposits, in fact, can be proved up for hundreds of feet by surface trenching and then intersected by drill holes at various depths like any other vein-like deposit. Others twist and branch, apparently defying all efforts to explore them short of actual mining.

Jan 1, 1954

By Lane, K. S.

The problem of stability of slopes in reservoirs is one of real interest in civil engineering. The problem is whether the valley walls will remain stable or whether they are likely to slide as conditions are changed by storage of water in the reservoir. If major slides are indicated, as on the walls of relatively steep canyons, one must estimate whether they will be so located and of sufficient size as to interfere with operation of the reservoir-as by blocking the outlets, or by displacing sufficient water to over-top the dam in a huge wave. Some cases involve problems in soil mechanics for slides in earth or weaker rock; other locations need the assistance of rock mechanics for slides in harder rock. While this is not a new problem, attention has recently been focused on its importance by the hugh landslide into the Vaiont reservoir in 1963, which claimed the lives of over 2000 people and forced abandonment of the dam and powerhouse.

Jan 1, 1969

By O. E. KEOUGH

AT the Tooele custom lead-zinc ore concentrator,' two sections, each having a daily capacity of 500 to 600 tons, are operated on slightly different types of ores with but little difference in flow sheet and reagents. The ores comprising the two general classes are the coarsely crystalline type, with low pyrite and sphalerite low in iron content, from the Park City district, and the more finely disseminated higher pyrite ores from Bingham, which are more difficult to treat by flotation. Laboratory testing determines with which general class a new ore will work better. The ores are crushed to minus 1 1/4-in. size at either the Utah Ore Sampling Company's plant at Murray, Utah, the Tooele smelter sampling plant, or the crushing plant at the concentrator. The ores for each section are mixed to maintain as nearly as possible uniform lead and zinc contents.

Jan 1, 1930

By Klaus Schwerdtfeger

The equilibria in the Cr-N system have been investigated in the temperature range 1100° to 1310°C by reacting chromium powder with Nz-Hz gas mixtures. The solubility of nitrogen in chromium in equilibrium with chromium subsitvide ("Cr,N") is given by Chromium subnitride is nonstoichiotnetric; its nitrogen content is always less than that corresponding to the formula CrzN. The lattice paranzeters of quenched samples have been measured; c, and a. parameters are found to increase with increasing nitrogen content. The growth rate of the subnitride layer on chromium plates was measured by a thermogravimetric technique, using a silica spring balance. The self-diffu-sivity obtained from the theoretical analysis of the parabolic rate constant is found to decrease with increasing nitrogen content, i.e., with decreasing vacancy concentration in the nitrogen sublattice. The intrinsic nitrogen diffuivity is derived from another series of rate measurements using "CrzN" plates; the intrinsic diffusivity, DN = 3.2 X 10-a cmZ sec-' at 1200 C, is found to be essentially independent of- the subnitride composition. The concentration gradient was measured in a chromium subnitride layer by the X-ray method and found to be consistent with the derived diffusivity value. TWO chromium nitrides are known to exist:' the nonstoichiometric subnitride "CrzN" and the nitride CrN. In the present work the kinetics of the formation of chromium subnitride from chromium and nitrogen have been investigated at 1100" and 1200°C. In additional experiments the relevant equilibria have been measured. The data are used to evaluate the diffusivity of nitrogen in chromium subnitride. Since chromium nitrides are often found in chromium-containing steels, the results are expected to be helpful in the interpretation of the chemical reactions between chromium steels and nitrogen. Equilibria in the Cr-N system have been determined by several investigators.2"3 The rate of nitriding of chromium was measured by Arkharov et a1 .' in ammonia in the temperature range 800" to 1200°C. The parabolic rate law was observed. Due to the undefined nitrogen activity of the ammonia atmosphere, it is dif- ficult to interpret these rate data theoretically. An additional difficulty arises from the fact that the two-layer scale consisting of CrN and "Cr2N" was formed at the temperatures below 1030°C. The rate of nitriding of technical chromium (95 pct) was measured by Zaks in nitrogen at -1 atm in the temperature range 800" to 1300°C. EXPERIMENTAL METHODS The chromium samples were reacted with Nz-HZ gas mixtures in a vertical tube furnace, wound with Pt-10 pct Rh resistance wire. The gas-tight reaction tube was of high-purity recrystallized alumina. In nitrogen solubility measurements the nitrogen content of chromium was determined by the Kjeldahl method, on samples quenched in the cold part of the furnace. The nonstoichiometry of the subnitride and the nitriding rates were measured thermogravimetrically using a sensitive (+0.1 mg) silica spring balance. For the equilibrium measurements samples of 1 g of chromium powder contained in high-purity alumina crucibles were used. In order to remove most of the oxygen and nitrogen impurities from the chromium, the samples were initially annealed in purified hydrogen until a constant weight was obtained. The chromium plates (approximate dimensions 2 by 1 by 0.08 cm) used for the rate measurements were machined from ingots obtained by arc-melting of iodine-processed chromium. According to manufacturers' specifications the purity of the chromium powder was 99.9 pct Cr and that of the iodine-processed chromium 99.99 pct Cr. Our own spectroscopic analysis of the chromium powder yielded 0.02 pct Fe, 0.05 pct Mn, 0.05 pct Si, and 0.02 pct Ti as major impurities with all the other detectable elements below 0.005 pct. The nitrogen partial pressure of the gas phase was controlled by mixing prepurified hydrogen and nitrogen with constant pressure head capillary flowmeters. Oxygen and water vapor were removed from the mixed gas by passing it through columns of platinized asbestos (450°C) and anhydrone. The gas flowed upward in the furnace with flow rates of 300 to 500 cu cm per min (25"~). Gas tightness of the furnace system was ensured by pressure checks at regular intervals. The furnace temperature was controlled electronically in the usual manner. The reported temperatures were measured with a Pt/Pt-10 pct Rh thermocouple and are estimated to be accurate within ±$C The X-ray measurements were made with a Debye-Scherrer camera and a diffractometer using chromium radiation {\Ka = 2.29092A). EQUILIBRIUM MEASUREMENTS The experimental results of the equilibrium measurements are contained in Tables I to In. Fig. 1 shows the solubility of nitrogen in solid chromium in the temperature range 1100" to 1310°C. In Figs.

Jan 1, 1968

By T. Fraser, F. F. Giese, R. L. Sutherland

Under a cooperative agreement between United States Bureau of Mines and the Truax-Traer Coal Company, some operating-scale experiments have been made with the cyclone thickener in the preparation plant of the Shamrock No. 1 mine at Kayford, West Virginia. These tests were made with a 14-in. cyclone of the type developed by the Dutch State Mines in Limburg. It was applied experimentally to the thickening of solids in washery water to obtain performance data to show the range of sizes that may be recovered and other operating characteristics that would indicate the field of usefulness of this device in coal preparation practice. This is a progress report only. It covers results obtained in a series of 17 tests of the operation of what has been considered a unit of commercial size operating on suspensions of fine coal mixed with a relatively small amount of free impurities. The underflow material, after further dewatering in centrifuges, is a marketable grade of coal. The coal at Shamrock No. 1 is mined from the No. 2 Gas seam. It is made up essentially of a low ash coal suitable for byproduct use with one or more bands of splint coal of higher ash content suitable for industrial fuel. The washing plant was installed for the two-fold purpose of removing the free impurities incident to mechanized mining and to separate the run of mine coal into the two types. To accomplish these results it is necessary to make a separation at a specific gravity of about 1.4 to recover the byproduct coal and to separate the splint coal from refuse at a higher gravity. The coarse coal section of the washing plant was put into service about 10 months before the fine coal section was completed. Inadequate screening capacity in the raw coal preparation plant resulted in a portion of the fine coal being fed to the jigs. No provision for preliminary dedusting of the raw coal feed was incorporated in the design. Under the conditions in the initial operating period, separation at the desired lower gravity was not realized, apparently because of the presence of an excessive amount of fine solids in suspension in the wash water. Difficulty in wetting the fine coal may also have been a contributing factor. Additional facilities for the removal of the fine solids from the wash water was indicated. Information then available on the Driessen cone for this purpose was studied and a cooperative agreement with the Bureau of Mines for experimental work with a unit of standard size as developed by the Dutch State Mines was arranged. During the time required for construction of the cone it was found the addition of a small amount of wetting

Jan 1, 1950

By B. B. Gottsberger

IT SEEMS strange that so many years after the pas¬sage of the first acts requiring registration or licensing of engineers, so few members of the mining branch of the profession are aware of what has taken place. Laws regulating the practice of engineering have now been passed in 19 states of this country, and in many others, such legislation has been proposed. That such laws are necessary for the protection of life, health and property, as is stated in most of them, is doubted by many. That the standing of the engineering profession will be improved by them is certainlyy open to question. That such laws are a welcome addition to the regulation of business by governmental agency, is not likely to be a general opinion. That once more, and in spite of appeals to engineers to interest themselves in affairs of government, an active minority has succeeded in imposing its will on a passive majority, seems but too true. However, the laws are there and information regarding them should be of use and interest to those most directly concerned.

Jan 1, 1921

By L. Weaver

THE Tennessee Copper Co.'s mines are in the southeast corner of the state of Tennessee, Polk Co., in the well-known Ducktown copper basin. Their new circular production shaft will eventually be the only ore hoisting shaft, and is located for handling ore from Boyd, Calloway, Mary, and Cherokee mines. A circular, rather than a rectangular, shaft was decided upon because: 1-The circular shaft section is stronger when lined with concrete. Reinforcing steel was not required, thus reducing lining cost by one- quarter. 2-Water sealing was desired; it was thought it could best be done with a concrete lining followed by pressure grouting to eliminate water seeps. 3-The shaft labor saving equipment could best be used in a large opening, so the round section was made for economy, sinking, mucking, concreting and water sealing. Less shaft steel is used than could have been possible with steel sets. There are no posts required; center beams and Tee plate assembly placed at 10 ft hold the 100 lb steel guide rails.

Jan 1, 1950

By Benjamin F. Tillson

Although portable fire extinguishers are valuable for fires in an incipient stage, some medium that will dissipate a large amount of heat is needed to fight a fire in mine timbers, because of the size to which the fire will probably have grown before it is discovered. Scaling off, or otherwise smothering such a fire with gases that will not support combustion, is often ineffective for the residual heat will cause reignition when the area is opened and fresh air reaches the hot charred timber. The most effective ways of fighting mine fires, therefore, are to drown and cool the hot zone with water, and to "load out" the partly burned material. Either of these methods requires a direct attack of water ; upon the inflamed material; therefore, every mine containing a large ' quantity of timber or other combustible should be as completely equipped with a fire-hydrant system as it is with compressed-air mains. Mine managers may object to the expenditure, especially if they have not suffered from mine fires. The cost of such preventative measures, however, is only a small portion of the possible losses, and the water pipes can be used for other purposes, which will pay the carrying charges. They can supply water to the rock drills, which will encourage more wet drilling with hollow-drill steel, for the trouble and expense of packing water to individual tanks at the drills will be removed. The carbon-tetrachloride hand extinguishers seem to have no place in mining except for fires that start in electrical equipment. They give off noxious gas, which may prove poisonous in confined quarters; and as it is heavier than air it is of no value for smothering fires overhead or in side timbers and would be dissipated by a good ventilating draft. The old soda-acid extinguisher or the more modern "foam" types ' are preferable. The former probably does not rely for its efficacy on the carbon dioxide generated but on the smothering and cooling effect of the water and the trajectory of stream that may be obtained because of the gas pressure developed. The production of a foam having a tough film to smother a fire, even on overhead surfaces, with the added

Jan 1, 1923