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By Harold W. Smith

Ore beneficiation via grinding and flotation has traditionally been considered an art because, until recently, the beneficiation plants that operated effectively were those run by skillful personnel who had acquired an "eye" and a "feel" for the process. Today, thanks to technological developments of the past five to ten years, ore beneficiation can be tackled more scientifically. In properly chosen applications, two developments that can bring significant operational and control improvements to concentrating plants are: • X-ray fluorescent spectrometers-that continuously measure chemical composition of flotation process streams, and • Minicomputers-that are relatively inexpensive and highly reliable in data gathering and process control.

Jan 11, 1974

By C. S. Smith, Chih-Chung Wang

D. Turnbull—In the opinion of the writer the most interesting result described in this paper is that the distribution of tin with respect to solidification temperature has several fairly well-defined maxima. It appears that each peak may be associated with a catalytic impurity of some rather specific composition. Recently we have obtained some additional evidence in favor of this viewpoint in experiments on the supercooling of lead droplets coated with different surface films. The distribution of lead droplets, ostensibly coated with lead sulphate, with respect to solidification temperature exhibited two distinct and reproducible maxima, one at 20" supercooling and the other at 47". On the other hand, when the droplets were ostensibly coated with halide films, no solidification was perceptible until the aggregate was supercooled more than 55". Upon further cooling a single well-defined peak centering at 60" supercooling was observed. Since the particle size distribution was the same in these two sets of experiments it appears that the most reasonable interpretation of the results is that the sulphate surface film or its reaction products with lead are much more effective in catalyzing the nucleation of lead crystals than are lead halide films. C. S. Smith (authors' reply)—Dr. Turnbull's experiments with lead drops coated with various surface films are most interesting. However, before drawing conclusions from the cooling curves described in the paper as to the existence of a few nucleus types effective at a few different temperatures, one must consider the state of subdivision of the liquid metal. In the A1-Sn alloy used, the tin was not in uniform droplets but tended to collect in three distinct shapes—in long interconnecting prisms along grain edges, in somewhat elongated interdendritic branching pools. and in isolated droplets. A single nucleus will solidify only the metal in contact with it, and the heat evolved will be proportional to the connected volume. A uniform distribution of nuclei of random effectiveness in such an alloy will cause peaks on the specific heat curve on cooling, which correspond to the volume distribution of tin and tell nothing about the nucleus type. In any real alloy both effects will be combined, and it seems impossible at present to distinguish between them. M. B. Bever—The thesis of this interesting paper is supported by a combination of positive and negative evidence. The authors have shown that under certain conditions a liquid phase may undercool, if it is dispersed in a thoroughly discontinuous manner throughout a solid matrix. They also found that undercooling

Jan 1, 1951

By Harry W. Antes

The density changes that occurred on annealing cold-worked poly crystalline molybdenum, over the temperature range of 870" to 1630 SC, were determined. Increases in density were observed for recovery and the beginning of recrystallization. An initial decrease in density was observed during re-crystallization. A second decrease in density was observed after recrystallization was completed, as the microstructure changed from columnar grains to equiaxed gvains Both decreases in density were associated with an increase in gain boundary area to volume ratio. The second decrease in density was observed in the annealing range that immediately precedes secondary recrystallization as reported in the literature VARIOUS techniques have been used to identify the recovery, recrystallization, and grain growth processes that occur when cold-worked metals are annealed. As early as 1928 work was conducted that indicated measurable density changes occur when cold-worked single crystals of brass are annealed.' More recently, work by Murphy exhibited a corre- lation of density with microstructural changes observed on annealing cold-worked polycrystalline a brass.2 Other investigators have performed similar work on a brass and copper.324 In reviewing the literature, it was apparent that density work had been limited to fcc materials. Therefore, it was the purpose of this investigation to determine the density changes that accompany annealing the cold-worked bcc material, molybdenum. Two degrees of cold work, 30 and 90 pct reduction of cross-sectional area by rolling, were selected for this study. EXPERIMENTAL PROCEDURE High-purity vacuum arc-cast molybdenum was used in this study, the principal impurity being carbon in the amount of 80 ppm. The final rolling reductions were made at 1200°C in grooved rolls to provide 5/8-in.-diam rod. Density specimens 0.500 in. diam by 1.5 in. long were machined from the bar stock. The specimens were ground to the final dimensions to provide a smooth surface. Density measurements were made using a hydrostatic technique similar to that used by ~urphy.' This type of equipment permitted weighing in liquid immediately after the air weighing. During each weighing the temperature of the air and liquid was controlled to within 0.0l°C. This was accomplished by sealing the analytical balance in an air-tight brass chamber and surrounding it by an insulated wooden case. Preheated air was circulated in the air space between the brass chamber and wooden case by means of a blower. The temperature of the

Jan 1, 1964

By W. W. Anderson, S. Razi

Electroluminescetrce of single crystals of terbium-(loped ZnS prepared by vapor-transport technique shows the sharp line specirum characteristic of the 4f— 4ft,ansitiotzs of the trivalent Tb3 rotz. V-I tt~easuverr~ents give evidence of space-ellarge-lirrlited curvent but the thrveshold for trap-filled law behavior is not iu agreement with Lampert&apos;s theory for. Single injection. Variations of &apos;brightness with applied voltage, the observation of double peaks its brightness because joms, and the spatial distribution oi electroLur?zir~escerrce indicate that the accelet~atiotz-collision mechanism involving the bst lattice and/ov shallow traps is most likely to be responsible fov excitation of&apos; electrolnminescence. Efficiency rtreusuver)~etits show the quantwn efficiency to be about 10 pct and powev efficiency about 0.05 pct. Effect of anr~eallng the crystal in sulfur vapor is to enluztzce llle rare-earth emission. It rs pvoposed tlzat sulfitv anr~ealing crreates acceptorr-lvpe defects with which the donor-type vare-eavtll ion can associate more readily vesulting in enhanced rare-earth emission. A&apos;o such e~zlznr~cerr~etrt is obserued when the crystal is atztrealetl in zinc vapor. Photolianinescence of ZnS doped nith a variety of rare earths also shows tile slurvp l~rze rwve-eavtlz erriission which in sorrretirr~es accompanied by broad band, stvuctureless lattice emission. Photo-atrd electrolutr~itzesce?~ce of ZIIS:Tb slw~rj do!rlit~unt rare-earth emission in the ~ticirzity of 54(3OA corre-sporrdit~g to the transition D* — Fj. Hoz~!el)er, the detailed line structuve of the luo spectvtr is cliffevet~t, irzdicutit~g that different sites are active in the two processes. Decay of rave-eartlr fluorescence in ZnS doped with any of sei!evul vuve eurtlzs car1 be described by a single exporleritial e.scepl joy ZrlS:lIo. Tl~is exceptiotr can be explaitred it~ tevrr~s of tlre closely spaced er~evgy 1e1:els Jov the HO~&apos; iorr. Decay lime measurertzekzts jov ZnS:Tb, using pulsed elect,-ical ar~d pulsed opticcll excitutiorzs, (11-e itz goor1 agrcetrier~t. LUMINESCENCE of rare-earth-doped materials has been a subject of interest for the past 20 years. Within the past few years there has been a considerable increase in rare-earth research motivated in search of new and more efficient laser materials and also due to the use of certain-rare-earth compounds in the preparation of color television screens. The purpose of this study has been to seek an understanding of some of the basic processes involved in exciting the rare-earth luminescence which is associated with transitions within the 4f shell of the trivalent rare-earth ion. Single crystals of ZnS doped with a variety of rare-earth ions have been prepared by vapor-transport technique described elsewhere.&apos; Photoluminescence was excited by a high-pressure short-arc mercury lamp together with suitable glass and chemical filters. For electroluminescence, sinusoidal and pulse excitations were used. 1) ELECTRICAL CHARACTERISTICS 1.1) V-I Measurements. Electroluminescence experiments were performed on crystals of terbium-doped ZnS. The samples were cleaned and etched and indium or In-Ga alloy contacts were alloyed on by heating in H2 atmosphere to 600°C for times ranging up to 10 min. Static voltage-current measurements were made on several samples. Fig. 1 shows the results for a typical sample. For voltage V < 20 v, the V-I relationship is linear giving a resistivity of 2.5 x 109 ohm-cm for this particular sample at room temperature. In the range of 20 to 250 v, I varies as V "3 and at still higher voltages (when electroluminescence is visible to the scotopic eye) current varies as Vs up to 600 v, all at room temperature. At 77"K, for V > 200 v, / I vge5 up to 1000 v. The V-I characteristics at room temperature follow reasonably well the behavior predicted by Lampert&apos; for one carrier space-charge-limited current in an insulator with traps although, as shown later, the expression derived by Lampert2 for the threshold for trap-filled law behavior Vtfl yields an unrealistically low value for trap density if we use the experimental value of 300 v for VtfL. Assuming the case for shallow trapping, the transition from Ohm&apos;s law behavior to space-charge-limited behavior occurs at voltage Vtr given by where no = thermally generated free carrier density, L = length of the sample, e = static dielectric constant, 6 = ratio of free to trapped electron densities, e = electron charge. For the ZnS:Tb crystal, L = 0.5 mm, E = 8.3 €0, Vtr - 20 v, and no = 5 x 10&apos; per cu cm, calculated from the ohmic behavior assuming electron mobility of 100 sq cm per v-sec. This results in 9 = 0= As more and more electrons are injected the Fermi level moves up in the forbidden gap toward the conduction band. If we assume a single-energy level for traps (which is not strictly correct, as we will show later), the current voltage characteristic is profoundly affected when the Fermi level crosses the trap level. The traps are now filled and injected carriers can no longer be immobilized in traps. Hence, current rises sharply with voltage. The transition from space-charge-limited behavior to the trap-filled behavior occurs at voltage VTFL given by

Jan 1, 1968

By H. H. Waller, D. L. Monroe, D. P. R. Smyth

ORIGINALLY slusher drift development was conventional, advancing the drift full 10x13-ft size at 6 ft per round. This proved dangerous and costly because the weak fractured rock of the orebody cannot be left raw for any length of time without its reacting with air to cause spalling. With this method of drift development ground conditions were worsened by many blasts and the length of time it was necessary for the drift to remain open. The problem was practically solved by driving 5x7-ft pilot drifts, then enlarging to 10x13-ft raw size by slashing with 50 to 60-ft diamond drill holes. Calculated explosive charges are used to avoid wall and roof shattering. Still more recently jacklegs and sectional steel replaced the diamond drills, resulting in the same work for less than half the cost, see Figs. 1 and 2. Crosscuts at right angles to the main haulage drifts, which cross through the center of the ore-body, divide the ore into 200-ft blocks. Eight slusher drifts on 50-ft centers draw from one block. The slusher floor is 11 ft above the rail, inclined at 1 pct grade, and the top is 18 ft below the undercut. The finished slusher drift is 102.5 or 120 ft long, depending on whether it is north or south of the crosscut. Drawpoints are staggered on each side at 17.5-ft centers. The completed drift is concreted and has an inclined ramp and a vent at the back. When crosscuts and gangways have been excavated and concreted and slusher stations installed, slusher drift development is carried out in 10 clear-cut stages: 1—Pilot drift is driven full length, 5x7 ft. 2—Station is excavated at half-way point in pilot drift. 3—Pilot drift is enlarged to slusher drift size by drilling. 4—Lower part of slash is blasted and mucked for floor concrete. 5—Floor is poured. 6—Inside upper half of slusher drift is blasted, mucked, and concreted. 7—Outside upper half of slusher drift is blasted, mucked, and concreted. 8—Drawpoints are excavated. 9—Drawpoints are concreted. 10—Concrete ramp and sheave protection recess are constructed at back end of slusher drift. A 5x7-ft pilot drift is driven full length on the center line of the proposed slusher drift using a jackleg and detachable bits on 7/8-in. hexagon steel. A 10-hp air-driven slusher and 36-in. scraper pull muck directly into cars in the main haulage crosscut, see Fig. 2. Operations are on a three-shift basis. One man mucks the previous round, drills, and blasts his round in a shift. Average advance is 5 ft per shift. When the pilot drift is completed, 7 ft of drift in the center section is enlarged to full raw slusher drift size of 10x13 ft, for the set-up to drill long slash holes. The pilot drift is slashed to full raw size from this station with jacklegs and tungsten carbide chisel bits on 7/8-in. sectional steel. Crews line the holes without trouble, working from controls established by the engineers, and the pattern of holes for the slash is arranged to give the least shattering effect

Jan 1, 1955

By Simon T. Johnson

Potential applications for boom tunnelling machines requires reliable assessment of in-situ performance. The majority of existing classification schemes concentrate on the prediction of excavation rate, neglecting the important influence of tool consumption rates. A statistical approach is taken to the analysis of the performance data, which was obtained first-hand through in-situ monitoring, and laboratory testing of representative rock samples. A statistical discrimination technique is used to produce a scheme for the prediction of performance groups, each of which covers a limited range of cutting rate and/or tool consumption rate.

Jan 1, 1984

By Brahm Prakash, R. Schuhmann

Chemical conditions for flotation and nonflotation of quartz with oleic acid as collector and barium, calcium, aluminum, iron, and tin as activators were studied using a simple vacuum-flotation technique in glass-stoppered graduates. The detailed study of barium activation led to an interpretation based on ideal Langmuirian chemisorption.

Jan 5, 1950

Mr. Brown : .That part of the Standard Company&apos;s plant which has been added since the publication of Mr. Leggett&apos;s paper, and is described in mine, renders the single-phase, alternating system, which Mr. Hale has called " unelastic," much more elastic than it had been. The original plant at Bodie was substantially the same as the Telluride plant mentioned in his paper. The machines came from the same shops, and were practically the same; but while the Telluride Company has changed completely to a polyphase system, the Standard Company has retained its original plant, but has belted on a directcurrent generator at the receiving end, thereby converting the water-power into electricity, electricity into power, the power into electricity, and finally again electricity into power for use in the mines. This is a roundabout course, to be sure, but it shows that there are possibilities even in the out-of-date single-phase system. The only point perhaps, that deserves particular notice with respect to the hoist is the fact that the rheostat, or starting-resistance, was not built originally

Jan 1, 1897

By B. L. Averbach, E. E. Underwood

The vapor pressure of zinc in equilibrium with solid ß AgZn alloys has been measured by the dew-point method. The thermodynamic activities of silver, and the molar heats of formation have been calculated. Similar measurements have been made for the ternary alloys formed by adding gold to AgZn. An apparent particle size effect has been observed for AgZn filings. The vapor pressure of zinc over filings is 15 to 20 pct higher than over the solid alloys. STATISTICAL methods have been used to inter pret the thermodynamic activities of the components of a solid solution in terms of average equilibrium atomic configurations. In some cases, the atomic arrangements can be measured by X-ray methods, and the results are usually expressed in terms of short range order parameters. Only in the cases of Cu³Au and AgAu have there been sufficient X-ray and thermodynamic data to verify the assumed correlation between the X-ray and the thermodynamic measurements. In Cu³Au the agreement is good; negative deviations from Raoult&apos;s law are observed and the number of Cu-Au nearest neighbor pairs predicted on the basis of the thermodynamic treatments agrees quite well with the number of such pairs observed by the X-ray methods. The ß brass alloys present a different set of conditions. The ordering is so rapid in these alloys that the disordered state cannot be retained on quenching. In contrast, the disordered state in CuAu is easily retained on quenching. On heating, the ordered ß brass loses its long range order continuously as the critical temperature is approached; in Cuau the order decreases slightly on heating and then drops discontinuously to zero at the critical temperature. These differences indicate that the short range order configurations in ß brass systems may be of a different character than in Cudu systems. However, X-ray measurements of local order cannot be made in the Cu-Zn alloys because of the similarity in scattering factors. The alloy AgZn is isomorphous with CuZn, however, and recent experiments have indicated that there is a good possibility of observing short range order in this system. Another complication arises in the case of ß AgZn. The disordered body-centered cubic structure exists above 280°C. On quenching from above this temperature an ordered structure of the cesium-chloride type is formed. On slow cooling, however, a complex hexagonal structure, the 3 phase, is produced; and if an ordered quenched alloy is reheated the phase begins to form above 80°C. It is thus difficult to study local order by X-ray methods in single crystals of AgZn since the C phase formed on heating does not necessarily return to a single crystal of the original orientation. This problem has been met, however, by adding a few percent of gold to the AgZn. The gold suppresses the formation of the c

Jan 1, 1952

By C. Erb Wuensch

The Eagle mine is situated in the Kerber Creek mining district, Bonanza, Saguache County, Colo. The climate and topography of this district arc similar to those of mining camps of the Rocky Mountain region that lie 9000 to 12,000 ft. above sea level. The district is at the northeasterly edge of the San Juan volcanic region, in which successive Tertiary lavas have built up a high plateau resting upon earlier sedimentary formations, or the underlying pre-Cambrian complex. The latter was exposed in places by erosion previous to the eruptions. In the Bonanza district, proper, only volcanic formations, andesites and latites, are found. Dr. H. B. Patton,1 in his survey of the district, discriminates between several varieties of lavas and maps these as distinct flows. They are local variations within the same lava and it is impossible to determine any distinct line of demarkation between them. Structurally they are members of the same flow. There are three general types of vein occurrences: 1. Lead-zinc-copper-silver-gold veins in well-defined fissures with a quartz gangue; ill these, the various sulfides show a zonal arrangement. 2. Massive gray copper ores high in silver, in irregular fractures in the form of small lenses and pockets, in which little or no quartz is found. 3. Manganiferous quartz veins very low in silver and gold at the surface which, with depth, become important silver veins containing subordinate amounts of gold. These veins have a quartz gangue with an abundance of Phodochrosite. The silver is associated with small amounts of sphalerite, galena, and pyrite; fluorite also is present. The Eagle is the only mine that has been developed in the manganiferous quartz type of vein. It was discovered ill the fall of 1582, but little more than assessment work was done on the property for a number of

Jan 1, 1923

By C. Erb Wuensch

The Eagle mine is situated in the Kerber Creek mining district, Bonanza, Saguache County, Colo. The climate and topography of this district arc similar to those of mining camps of the Rocky Mountain region that lie 9000 to 12,000 ft. above sea level. The district is at the northeasterly edge of the San Juan volcanic region, in which successive Tertiary lavas have built up a high plateau resting upon earlier sedimentary formations, or the underlying pre-Cambrian complex. The latter was exposed in places by erosion previous to the eruptions. In the Bonanza district, proper, only volcanic formations, andesites and latites, are found. Dr. H. B. Patton,1 in his survey of the district, discriminates between several varieties of lavas and maps these as distinct flows. They are local variations within the same lava and it is impossible to determine any distinct line of demarkation between them. Structurally they are members of the same flow. There are three general types of vein occurrences: 1. Lead-zinc-copper-silver-gold veins in well-defined fissures with a quartz gangue; ill these, the various sulfides show a zonal arrangement. 2. Massive gray copper ores high in silver, in irregular fractures in the form of small lenses and pockets, in which little or no quartz is found. 3. Manganiferous quartz veins very low in silver and gold at the surface which, with depth, become important silver veins containing subordinate amounts of gold. These veins have a quartz gangue with an abundance of Phodochrosite. The silver is associated with small amounts of sphalerite, galena, and pyrite; fluorite also is present. The Eagle is the only mine that has been developed in the manganiferous quartz type of vein. It was discovered ill the fall of 1582, but little more than assessment work was done on the property for a number of

Jan 1, 1923

By Charles Catlett

The terms " developed " and " undeveloped " are necessarily relative and cover a wide range; but the latter is here applied to cases in which the information at hand falls short of a clear demonstration of values, and conclusions must be reached frorn a study of the geological conditions of the particular deposit, interpreted in the light of similar and closely-related deposits. Such an inquiry might be characterized as an effort to reach reliable conclusions from insufficient data. But the engineer

Jan 1, 1909

By Paul Rhedey

Various commercial pelroleum cokes were heat-1,reated at temperatures between 500° and 1500°C, in a nitrogen atmosphere, in laboratovy induction furnaces. The rate of tenlperature rise was varied betzveen 10" and 300°C per min, or the green cokes were flash-calcined, orv a combination of heating rates was used. Changes in the rate of heating had only negligible effects on the degree of&apos; calcination as characterized by mean crystallite thickness and the chemical properties of the calcined coke. The physical structure of the cake was however significantly affected when rate of heating during calcination exceeded 50°C per min over the temperature range of 600° to 900°C. Surface-accessible porosily increased with the .rate of temperature rise, and this was accompanied by a change in pore size distribution. Source and properties of the green coke also had an influence on the structure of the calcined coke. The evidence presented suggests a similar mechanism of porosity development in petroleuiiz coke during calcination in industvial equiplnenl, such as rotary kilns. An increase in surface accessible povosity incveased the pitch binder requirement when the coke was used as aggregate in Soderberg paste. A correlation was established between calcined coke porosity and paste binder requiremenl. ManY results have been published on the changes of properties of petroleum coke during calcination, such as chemical composition, real density, electrical resistivity, crystallite and pore structure. The correlation of these properties with temperature of calcination and time at maximum temperature has been rather well established in both laboratory and pilot plant experiments. Surprisingly little attention has been given however to the effect of calcination conditions, such as rate of temperature rise or furnace atmosphere, on the chemical and structural properties of the calcined coke. It has been observed that petroleum coke, when calcined in industrial equipment, acquires higher porosity and lower real density than those attainable in laboratory furnaces at apparently identical calcina- tion temperature and soaking time. This paper describes a study of the effect of rate of heating during calcination on calcined coke properties using green petroleum cokes of different volatile matter, hydrogen, and sulfur content. An attempt was made to correlate the changes in coke structure with the flowability of anode paste of the type normally used in aluminum reduction cells. EXPERIMENTAL Petroleum Cokes Used. In the study of release of volatile matter and sulfur during calcination and the effect of rate of heating on calcined coke properties two delayed cokes of different sulfur contents were used. The results of analysis of the green cokes are given in Table I. In the study of the effect of flash calcination thirty-six commercial petroleum cokes from twelve different refineries were used with a range of properties shown in Table 11. Calcination Conditions. Calcination experiments were carried out in a laboratory induction furnace. In each run a 200-g sample of dry green coke sized to 10 by 65 Tyler mesh was calcined in a graphite crucible. The crucible containing the sample was placed in the middle of a stack of eight others filled with metallurgical coke to reduce temperature gradients within the sample. Temperature was measured by two Pt, Pt-10 pct Rh thermocouples and controlled by a Celectray instrument. The two couples generally agreed within 5°C. In the study of volatile matter and sulfur release the samples were heated to temperatures in the range of 500" to 1500°C at a rate of 10°C per min in a nitrogen atmosphere and held at the final temperatures for 30 min. In the study of the effect of heating rate on calcined coke properties the desired rates between 10&apos; and 300°C per min were obtained by manually adjusting the power input. Flash calcination was carried out by dropping 100 g of the green coke into the graphite dish preheated to the calcination temperature. Because of the small heat capacity of the furnace the coke was introduced in 20-g portions at a time. For this purpose a 2-in.-long nipple between two 1-in. gate valves installed on the top flange of the furnace served to provide a gas seal while feeding coke to the furnace. It was estimated that the temperature of the coke reached that of the furnace at a rate of approximately 1000°C per min. Holding time at final temperature was also 30 min. Calcined Coke Proper- Determined. Porosity was determined on 20 by 35 Tyler mesh samples using an Aminco-Winslow mercury pressure porosimeter with an operating range of 1.8 to 3000 psi absolute pressure (100 to 0.05 p pore diameter range).&apos; Apparent density was obtained by the mercury poro-simeter. It represents a particle density of the 20 by

Jan 1, 1968

By J. D. Lindner, Gene E. Roark

Waterflooding operations in the Langston-Kleiner field. Young County, Tex., are described. Widespread application of formation fracturing has been practiced in both producing and injection wells. Field performance data arc cited which indicate than no detrimental effect on sweep efficiencies and that probable benefits in imectivily have resulted from the fracture treatments. I N T R O D U C I O N This paper is a report on a waterflood operation which is being carried out in the Lanpston-Kleiner field located in Young County, Tex. The oil reservoir aflected by this flood operation occurs in a Strawn sand member at an approximate depth of 3.550 ft subsurl&apos;ace. The operators of&apos; the project are Kleiner Estate. Turncr. Fiske. and West who are hereinafter collectively referred to as the Operators. Although the operation is unusual in several respects, the distinctive feature of this flood has been the widespread application of hydraulic formation fracturing treatments as a means to improve productivity and injectivity of the wells. It shall he the purpose of this paper to present basic information regarding the reservoir characteristics. op- craling practices, and waterflood behavior so that conclusions may be drawn concerning the effects which the fracture treatments have had on the performance of this water flood to datc. DEVELOP MENT Development of the 3,550 ft Strawn sand reservoir occurred during 1951 and 1952. The early development occurred on the Langston and Davis leases which arc in the northern region of the Operators&apos; holdings and the wells were drilled on 20-acre proration units according to the field rules. However, studies of the economics of this program. coupled with the decision to proceed with pressure maintenance by water injection. resulted in the adoption of wider spacing in the later stages of development. This variation in spacing is apparent upon inspection of Fig. I upon which only the 3,550-ft Strawn sand producing and injection wells have been located on the Operators&apos; properties. The development to the north of the operators leases is Ihe Garvey Strawn field and that to the south is the Taylor Strawn field. It wits determined that unitization of the leases to he involved in the waterflood program was not feasihle. Consequently. a system of offset injection wells, or lease line injection wells, was adopted from place to place as required to protect correlative rights in the program. This resulted in a dispersed array of injection and producing wells with relatively close proximity of wells along lease line areas and wider spacing toward

Jan 1, 1956

By M. A. Cook

Sutherland used an ion-pair adsorption model to derive the author&apos;s hy-drolytic pee-acid) adsorption equation for the contact bubble curves of Wark and Cox. To do so it was necessary to postulate that the sum of coverages of surface anion sites by the collector and depressant anions is practically unity. It is here shown that the free energy of Sutherland&apos;s postulated collector ion (x-)-depressant ion (OH-) exchange reaction (for no other than the OH- to compete with X-), namely EX + (OH-) Z SOH- + X-, is in some cases positive and X- should not even adsorb. Also, in many cases the (OH-) adsorption must be quite negligible even though the collector covers only about a sixth of the mineral surface at the threshold of air bubble contact. This, however, contradicts the postulate that permits one to derive the correct bubble contact eqwztion for the ion-pair model. Furthermore, the requirement for charge neutrality leads in the ion-pair model to the (impossible) constancy of the ratio @+)/(OH-) along a contact bubble curve in which pH may change by more than seven units. HYDROLYTIC ADSORPTION EQUATION Hydrolytic (free-acid or free-base) and ion-pair (H&apos;, X-, or R&apos;, OH-) adsorption models of the collector in metal sulfide and similar flotation systems are superficially alike and somewhat difficult to differentiate. This is because they yield, under seemingly valid assumptions, equivalent forms of the equations describing the distribution of the collector between the aqueous solution and the mineral surface. This has been discussed by the author and associates1-4 and more recently by Sutherland,&apos; both for simple collector-mineral and for more complicated collector-depressant-mineral systems. In the hydrolytic adsorption model the equations describing the contact bubble curves of Wark and coxeJ7 are as follows :2 Here X is the collector anion, D- the depressant anion, 9, and On are the fractions of the free-acid sites S on the surface of the mineral covered by collector and depressant free acids, respectively, and @ is the fraction of uncovered sites. Kx is the free-acid collector dissociation equilibrium con- stant, K1 that for the free-acid collector adsorption, KD that for the free-acid depressant dissociation, and K2 the equilibrium constant for the free-acid depressant adsorption. Eqs. 1 to 5 yield upon simultaneous solution the result is the critical free-acid concentration for bubble contact in the absence of depressant-free acid. Eq. 8 expresses the conditions along a simple collector-mineral contact bubble curve for the case HD = 0, or V = 0. Last and Cook showed that Eq. 6 applies generally and with good accuracy in the collector-depressant-metal sulfide mineral systems. Inci-dentally, it has been shown by infrared absorption studies that in some cases the free-acid adsorption process splits out water.&apos; In this case, Eq. 2 might be written SHOH + HX Z SHX + H20, with a similar equation replacing Eq. 4 for depressant-free acid-water exchange. This possibility does not change, however, the basic equations or considerations of the hydrolytic adsorption model. Indeed, this type of free acid-water exchange reaction was predicted for fluorite and iron ore flotation by oleic acid in the dry grinding and boiling processes.410

Jan 1, 1961

By Carl Altstetter, Roy Adams

Measurements of enthalpy changes and transformation temperatures me reported for the fcc -hcp marten-sitic transformation in pure cobalt single and multi-variant crystals andpolycrystalline specimens. From these measurements the free-energy difference between the two phases was calculated for both heating and cooling and for repeated cycles through the transformation. For heating of single crystals the average value of enthalpy change was 113 cal per mole but on cooling it was 84 cal per mole. This difference is interpreted in terms of lattice imperfections which are introduced during transformation. A calorimeter suitable for measurement of enthalpy changes of athertnal transformations is described. COBALT exhibits an allotropic phase transformation at around 417°C&apos; where an hcp phase (a = 2.507, c = 4.0686, c/a = 1.6228)~ stable at low temperatures transforms to an fcc phase stable up to 1495°C. The transformation has a hysteresis of about 30°C— the exact magnitude of the hysteresis depending on the number of transformation cycles, grain size, impurity content, and prior treatment.&apos;-6 The athermal character of the transformation and surface relief due to transformation shear indicate that the transformation is martensitic. Pole mechanisms for the transformation have been discussed by Sebilleau and Bibrin, Bilby, Seeger,&apos; and Basinski and Christian. These authors have proposed that the cooling transformation is effected by rotation of a Shockley partial dislocation around a pole dislocation with a screw component of 2a/3(111). Such a rotation would change the stacking of close-packed planes from the abcabc fcc stacking to the ababab hcp stacking sequence. This mechanism would predict a lattice correspondence of {111}fcc~~(0002~cp, have been observed. One would expect the heating transformation to occur similarly, involving dislocation movements on the (0002)hcp. However, a high density of pole dislocations and high dislocation ve- locity are required to account for microscopic observations. Furthermore, the high back stress developed on the Shockley partial dislocation as it rotates toward the sessile dislocation associated with it makes it doubtful that this is in fact the transformation mechanism. A mechanism for spontaneous nucleation of partial dislocations1*l2 seems more reasonable. If a single crystal of cobalt is cycled through the transformation but never heated above 600°C, it will remain single."13 However, if the specimen is heated through the transformation and held for a short time at or above 1000°C before cooling, the cooling transformation usually involves all four {lll}fcc habits, resulting in neighboring orientations of hcp differing by 70.5 deg. This condition is termed multivariance and has been observed by Bibring and sebilleau5 and Nelson and ~ltstetter.&apos; The latter authors used single crystals of cobalt grown in an electron beam zone refiner. They proposed that the strongly directional cooling caused the initial cooling transformation to occur on the {lll)fcc most nearly perpendicular to the temperature gradient. Transformation shear on one set of {lll}fcc planes immobilized dislocations on the other {lll}fcc planes involved in the initial transformation. Since there is only one (0002)hcp plane orientation, the product of subsequent heating transformations could have no more than two variants—the original fcc orientation or its twin. If, however, the specimen was annealed at a high temperature, such as 1000°C, there would be relaxation of dislocations into low-energy configurations, and in the absence of a sharp temperature gradient transformation on all four (111 Ifcc planes could occur. If a dislocation mechanism is responsible for the transformation, the perfection of the lattice should affect the reversibility of the transformation. Mutual constraints of neighboring grains in polycrystalline material would inhibit dislocation movement resulting in increasingly sluggish transformation. Indeed, Nelson and Altstetter found the M, to decrease and the A, to increase in going from single crystals to multi-variant specimens to polycrystals. The effect is enhanced by decreasing the grain size of a solid specimen or a powder.6&apos;14 Data on the free-energy difference necessary to initiate the transformation gives information about the driving force of the transformation. This is an important consideration in the understanding of the transformation mechanism. The free-energy change associated with the transformation of the hcp phase to the fcc phase at some temperature T different from the equi-

Jan 1, 1969

By I. Cornet

INTRODUCTION WITH the greatly expanding use of magnesium during the war, it appeared necessary to the War Metallurgy Committee that the notch sensitivity of magnesium alloy extrusions be further investigated and the influence of various factors upon notch sensitivity be noted. Accordingly, the National Defense Research Committee of the Office of Scientific Research and Development placed a research contract with the University of California, supervised by the War Metallurgy Committee. The work discussed herein was done under "Restricted" Project NRC-21, reported in Dec. 1943 1; it has been released for publication by the O.S.R.D. SCOPE OF THE INVESTIGATION The notch sensitivity of various magnesium alloy extrusions was determined under axial tension, and also under several conditions of nonaxial tension. Hardness, grain size and other metallographic features were observed; stress-strain data were obtained, and the chemical compositions of the alloys were determined, in order to correlate these quantities with the notch sensitivity. Notch sensitivity under axial tensile load was determined for a few specimens which had been cold worked to various degrees by tensile prestraining. Magnesium alloy extrusions studied included Dowmetal 0, X, J, and M. For comparison, extrusions of aluminum alloy 24S-T, cast bars of aluminum alloy I22-T2, and cast bars of magnesium alloy C were also tested, The specified chemical composition of these alloys is given in Table I. All bars tested were within specification limits of composition. Investigation of the tensile notch sensitivity of various magnesium alloy extrusions, under conditions of axial and eccentric load, showed little or no correlation with stress-strain or other conventional data. Since the many uncontrolled variables present might mask significant relationships, one alloy was selected for intensive study. Magnesium 0 alloy extrusions were subjected to experimental heat treatments, and the changing hardness, tensile strength, microstructure, and notch sensitivity observed. EXPERIMENTAL TECHNIQUES AND PROCEDURES Tensile Testing Bars used for axial loading were machined with 3/8 in.- and with 1/4-in. minimum diam, and included specimens with 6o° V notches (Fig I and 2). Each V-notched specimen was roughed out carefully and then finished with a honed tool. These V-notched bars were sampled frequently, sectioned, polished, and examined at 500 X magnification to control

Jan 1, 1948

By Edward Keller

In order to conduct intelligently the sampling of copper of various forms and grades, solid or in molten furnace-charges, a knowledge of this subject is essential. Yet figures and tests have been persistently withheld from publication, and the books at our command give us little or no information in this regard. This gap in our copper-literature has led to a series of experiments, the results of which are given below. Nearly all gold- and silver-bearing copper, destined for shipment, is cast into the form of bars or pigs. For the sampler, the question arises, Does copper, so cast, remain homogeneous ? If it does, sampling should present no difficulties; but, from experience, we know that this is not the case, and we are thus led to study the behavior of the precious metals arid impurities in copper when the latter changes from the molten to the solid state. For the purpose of the experiments here described, all available grades of copper were selected, and all of them mere subjected to the same conditions, an important requisite for proper comparison. The molten copper obtained directly from reverberatory- and blast-furnaces was cast in a cast-iron mould, the sides and bottom of which were 1 inch thick, and would, therefore, give the copper a fair length of time to chill. The inside dimensions of the mould, and, consequently, of the block of copper obtained, were: length, 10 inches; width, 9 inches; and depth, 5 inches. Fig. 1 illustrates the method employed to obtain samples from these blocks. A was cut away, and the face so produced BALTIMORE COPPER WORKS,

Jan 1, 1898

By Edwin B. Johnson

The success of self-fluxed sinter in enhancing the operation of the blast furnace during the past few years has reasonably led to the assumption that the use of self-fluxed pellets might result in even greater furnace efficiencies. A great share of development work in agglomeration has been directed towards techniques related to the production of self-fluxed pellets, but no appreciable tonnage of self-fluxed pellets had been produced on a commercial scale until this past year when The Cleveland-Cliffs Iron Co. produced 35,000 tons of such pellets by the grate kiln system at the Republic mine during the period May 21-June 5, 1962.

Jan 3, 1963

By John V. Beall

The forecast of continued growing demand for phosphate, chiefly for fertilizer, has caused a world-wide rush for deposits by a variety of companies many of which have never before mined phosphate rock. The newcomers are diversifying into this growth industry on the strength of certain capabilities. Among these are the availability of investment capital, mining or processing know-how and marketing experience. Product tie-ins have motivated some into the search. Companies with excess sulfuric acid or potential for making it are in this category. This acid is the most commonly used for dissolving phosphate rock to make phosphoric acid. Base metal smelting companies are prime candidates in this field with by-product acid from roasting processes. Producers of "sweet" natural gas, such as those in Louisiana and Texas, have a potential for recovering low cost hydrogen from excess gas production for the manufacture of ammonia, the main source of nitrogen for fertilizer. "Sour" gas producers, such as those in the Canadian fields, are making sulfuric acid that is combined with western U.S. phosphate to make fertilizer materials. The presence of one or two steel companies in the look-see for phosphate deposits is based on by-product ammonia from coke-oven gas.

Jan 10, 1966