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By E. J. Roberts

Hydrometallurgical operations and many processes in the chemical industry require the separation of dissolved material from solids. One of the decisions which has to be made in designing a plant for such an operation is how this separation shall be accomplished. It is the purpose of this paper to set forth the general principles involved in such separations in order that the optimum flowsheet and equipment may be selected. Countercurrent Decantation with thickeners, or C.C.D. as it is generally known, is, of course, only one way of separating dissolved material from undis-solved. Other unit operations such as Countercurrent Filtration (C.C.F.) and Countercurrent Classification (C.C.C.) are widely used. The same principles may also be applied to centrifugally assisted decantation, as with nozzle or solid bowl type centrifugals, and to separations using screens, either gravity or centrifugal type. Another form of countercurrent washing applicable to granular materials is practiced in continuous ion exchange operations. All of these operations depend on two basic principles, or combinations of these principles. In C.C.D. type operations the solids are concentrated into the smallest possible volume of liquor in each step and the resulting pulp then mixed with a more dilute liquor and recon cen trated, the liquors separated from the more dilute stages being advanced to dilute the more concentrated liquor in a previous solids concentrate, as is shown in Fig. I. This will be termed the solids concentration-solution dilution principle, or, for short, solution dilution. countercurrent decantation- type circuits. The second principle used in washing solubles from solids is that of solids concentration-solution displacement. Here the solids are restrained from movement while wash solution is forced through the interstices in a counter-current fashion, as in Fig. 2. In the simplest application of this principle, once the "cake" has been formed, it is not disturbed until the operation is completed. In continuous filters, the cake is merely moved under the successive washes and the displaced filtrates removed as in Fig. 4. Often, however, after one or two displacement washes, a repulping step is introduced, the cake reformed and washed again. This procedure brings the solution dilution principle into play as well as the solution displacement principle. Merely thickening ahead of filtration, which is often operationally advantageous, does not hybridize he circuit. It still can be a pure solution displacement operation from the washing

Jan 1, 1961

By W. J. Skewes, C. T. Holland

Properly constructed stopes are necessary underground for proper ventilation and safe, healthful working conditions. Mining companies are concerned with providing the best possible stoppings at an economic cost. It is important to consider 1) proper materials, 2) construction that ensures maximum performance from the material used, and 3) keeping costs within reasonable limits for the unit operation—stopping—involved. The authors investigated all aspects of the problem and have attempted to layout a study program to provide information on all phases. Mining companies every year purchase huge amounts of material for the construction of ventilation stoppings. This material by the time it is in place in the stoppings will cost the company many thousands of dollars. In addition and more importantly these stoppings are supposed to confine air travel along certain well defined paths into areas where it is needed to provide safe and healthful atmospheres for workmen. The cost of forcing this air through the mine is large and in general increases as the total quantity increases. Consequently, if the stoppings leak, increased cost results and in addition unsatisfactory ventilation may prevail in the mine. Therefore, it is essentia1 to provide the best possible stoppings at an economic cost. When attempting to provide the best stoppings possible at an economic cost, three aspects of the problem must be considered. These are 1) getting the most suitable material for stopping constructions, 2) constructing the stopping so as to get the best performance from the material used, and 3) keeping the cost of stopping construction to a minimum for a suitable stopping. This investigation is concerned with all phases of the problem and has attempted to lay out a study to provide information on all of them. In order to develop information on the best stopping material available it seemed wise, after con- sidering the job a stopping must do, to investigate the following aspects of material used for stoppings: 1) strength in compression, 2) compressibility or yield under load, 3) porosity, and 4) permeability. To provide information on the best manner of construction the following aspects of air leakage through the stopping were investigated: 1) when the stopping is built of dry stacked materials—i.e., the joints are not mortar-laid (See Fig. 1); 2) when the stopping is built of dry stacked material and then plastered on one side (see Fig. 2); 3) when the

Jan 1, 1961

By M. V. Nevitt

In the systems Ti-Mn-O, Ti-Fe-O, Ti-Co-O, and Ti-Ni-O the bounda.r-ies of the Ti2Ni-type phases were determined at one or more temperatures and the variation of the lattice parameter with oxygen content was determined. Densities were calculated from the lattice parameters and compared with measured density values. The: results indicate that the occurrence of the phase in these systesms can be correlated qualitatively with valency electron concentration, and that the role of oxygen is that of an electron acceptor. The lower limit of oxygen solubility appears to be determined by the valencies of Mn, Fe, Co, and Ni, while the maximum oxygen concentration coincides with the filling of the 16 (c) positions of the O 7h - Fd 3m space group. THE suggestion has been made by several investigators'" that the phases having the cubic E9,-type structure, and known as 17-carbide-type, double-carbide-type and Ti,Ni-type, are members of a family of electron compounds. This concept has been given additional support by recent work8 in which new isostructural phases involving second and third long period combinations were found, and which provided further evidence of the regularity of occurrence of the phase in terms of periodic table relationships. In this laboratory attention has been focused on the isomorphs containing titanium, zirconium, or hafnium, and the role that oxygen plays in their occurrence. In some binary systems Ti,Nitype* phases occur having the formula A,B where A is the titanium group element. Based on previous workq and the present investigation, oxygen is known to be soluble in two of these binary phases, Ti,Co and Ti2Ni. It is probable that oxygen is also soluble in the other phases of this kind. In other binary systems the Ti,Ni-type phase does not occur, but does occur in the corresponding ternary systems with oxygen .3-5 The experiments described here were performed to determine whether the occurrence and composition of certain of the Ti,Ni-type phases could be related to an electronic effect and whether oxygen's stabilizing role is exerted through an influence on the electron: atom ratio. The ternary systems Ti-Mn-O, Ti-Fe-O, n-Co-O, and Ti-Ni-O were selected for study for two reasons: First, several schemes have been proposed for first long period elements which, although not in quantitative agreement, show a generally consistent trend for the variation of valency with atomic number. Although for a transition metal the term valency is difficult to define and is generally not a constant number which can be applied to all alloys, it is usually assumed to be an index of the number of electrons per atom involved in metallic cohesion. Second, the determination of the Ti2Ni-type phase boundaries was facilitated by the fact that the phase relations in several of these ternary systems have been investigated by other workers."' EXPERIMENTAL PROCEDURE___________________ The alloys were prepared by arc melting crystal-bar titanium, reagent grade TiO, and electrolytic manganese, iron, cobalt, and nickel. Each button was remelted at least three times. The metals had a minimum purity of 99.9 pct except the nickel whose purity was 99.4 pct, the major impurity in this instance being cobalt. The preparation of the manganese alloys was attended by the customary difficulties associated with the vaporization of manganese. The technique used in this case was to add approximately 10 pct extra manganese to the original charge and to continue remelting the button until the final weight was in agreement with its intended weight. At least three alloys in each system were analyzed chemically and the results, even for the manganese alloys, were in good agreement with the intended compositions. A few additional alloys in the Ti-Mn-O system were prepared by the sintering of mixed powders in evacuated quartz tubes followed in some cases by arc melting. For annealing, the alloys were wrapped in molybdenum foil and placed in fused silica tubes containing zirconium chips. The fused silica tubes were evacuated at room temperature to a pressure of 1 x l0-6 mm of Hg and sealed. These capsules were then annealed for 72 hr at an external pressure of 5 x 10-5 mm of Hg in a vacuum furnace whose temperature could be controlled to + 1°C. The success of this procedure in avoiding significant oxygen or nitrogen pickup was indicated by the bright, ductile condition of the molybdenum foil and by the complete absence of a microscopic reaction layer on the specimens. This method did not permit rapid quenching of the specimens but in no case did metal-lographic examination indicate that a solid-state transformation had occurred on cooling. Metallo-

Jan 1, 1961

By S. J. Gasior

Pilot plant studies showed the technical feasibility of fluidized-bed operation for producing hydrogen and synthesis gas by the steam-iron process. A mixture of iron and iron oxide from 20-to 100-mesh was partially reduced with a simulated producer gas and then oxidized with steam and/or carbon dioxide. Results of tests show the effects of pressure, temperature, bed height, gas-to-solids ratio, type of iron oxide, and composition of gas on the gas and solids conversions during reduction and oxidation. A baffled free-fall solids system was also found operable. The short residence time of about 5 seconds limited conversion of the solids.

Jan 1, 1961

By E. S. Machlin

The kinetics of vacuum distillation, vacuum-melt surface reactions, crucible-melt surface reactions and boiling are analytically investigated. No disagreement with experiment is obtained upon applying a rigid flow model to describe the behavior of the melt in the vicinity of reaction surfaces. The theory focuses attention upon measureable parameters rather than upon the adjustable parameter, stagnant layer thickness, associated with other theories. The rigid flow theory is thus capable of quantitative evaluation and experiments to achieve this evaluation are suggested. KINETICS, rather than thermodynamics, often determine the degree of refinement achieved in vacuum melting. There is little understanding, however, of the kinetic principles involved in vacuum refining. This paper represents an attempt to achieve this understanding. There are two reactions which need to be con- sidered. The first is the refining reaction. The second shall be called the polluting reaction. It is the reaction associated with the introduction of components of the crucible into the melt. The mechanisms of both reactions are unknown. Many models can be constructed to describe either the refining or polluting reactions. For example, consider the refining reaction C + Q = CO(g). One model that can be imagined is that the carbon and oxygen combine in the melt to form CO which then diffuses to a melt-

Jan 1, 1961

By Tasuku Fuwa, John Chipman

Equilibrium data on the reactions of gases with carbon and oxygen dissolved in liquid iron are reviewed and correlated. A source of error in oxygen analysis of graphitic samples is exposed. New experimental data on the oxygen content of high -carbon iron in equilibrium with carbon monoxide indicate that the activity coefficient of oxygen is decreased by additions of carbon. The carbon-oxygen product decreases slightly with increasing carbon content. In recent years a number of investigations have been reported dealing with the equilibria between carbon and oxygen in liquid iron and gases containing carbon oxides. The laboratory study of these reactions dates back to 1931 with the publication of a paper by Vacher and Hamilton' on "The Carbon-Oxygen Equilibrium in Liquid Iron". The principal object of this study was to obtain data on the reaction shown by Eq. [3] below; their data and others by vacherZ permit evaluation of the other equilibrium constants as well. Subsequent studies have been reported by Matoba, Phragmen and Kalling and by Marshall and Chipman.5 The equilibria may be expressed by the following three equations: C + CO,= 2CO;Kl = Pc° [1] 0-+CO = CO,;K2=-P co, "0.PCO c + O = CO; K3 = In the equilibrium constants, ac and a0 are taken as equal to [% C] and [% 0] respectively in the infinitely dilute solution. At finite concentrations an activity coefficient is introduced such that ac =fc [%C], and so forth. It is to be noted that these equations represent only two independent relations, the third being derivable from any two. Richardson and Dennis have determined the conditions of equilibrium in reaction [I] at temperatures of 1560" to 1760°C. Their results have been confirmed by Rist and chipman7 who have shown how the data may be extended to cover the entire range of liquid compositions at temperatures from the eutectic up to 1760°C. An approximate confirmation has been reported by Fuwa and chipman.' These investigations also established the activity coefficient of carbon which was shown to increase rather rapidly with increasing concentration. For the very dilute solutions the value of Kl is expressed in the equation: log^i = - 7280/T+ 6.65 This equation leads to a value of Kl = 430 at 1540° C in excellent agreement with the average value of Marshall and Chipman.5 It is shown as line 1 in Fig. 1 together with the experimental observations. In the case of reaction [2] the direct experimental results can be supplemented by observations on the corresponding reaction with hydrogen, namely reaction [4]:

Jan 1, 1961

By R. H. Doremus

From measurements of carbide precipitation rates in a iron it was concluded that the carbides nucleated on dislocations in both strained and unstrained samples, except for the latter at lower temperatures and higher carbon concentrations, where there were more muclei than could form on the dislocations. The equation of Cottrell and Bilby for the segregation of atoms to dislocations was found to be inapplicable to this system. No satisfactory theory for the growth process is available. A study of the rate at which a second phase separates from solid solution can frequently reveal much about the mechanism of separation. There are still many features of the precipitation of carbon from a iron that are not understood, although this system has been examined extensively. To provide more insight into the mechanism of carbide precipitation in a iron, rates of this process were measured at different temperatures, carbon concentrations, and densities of dislocations in the iron. The concentra- tion of carbon in solution was followed from the height of the internal-friction peak; this height is directly proportional to the amount of carbon in solution and is not affected by the growing carbide particles. In this paper these rates are compared with those found by earlier investigators, and the mechanism of precipitation is discussed in light of these results as well as two earlier studies1, 2 and the electron microscopic work reported in the preceding paper. EXPERIMENTAL The amount of carbon in solution was followed by

Jan 1, 1961

By J. G. Croeni

The high thermal-neutron cross section of gadolinium and the good mechanical and corrosion properties of titanium suggest that alloys of these two metals might be useful as control rod material. To aid in establishing the feasibility of this combination, the Federal Bureau of Mines investigated the titanium-gadolinium system. The results indicate that the system is composed of a single eutectic reaction and a peritectoid reaction involving the alpha-beta transformation of titanium. The eutectic isotherm extends from 1 to 99 pct, gadolinium at 1,240° C. The established eutectic composition is about 95 pct, gadolinium. The peritectoid reaction occurs at 885° C. and extends almost over the entire composition range. Hardness increases slightly with additions of gadolinium, and little change is obtained by heat treatment. Alloys containing less than 10 pct. gadolinium are amenable to extensive cold-working, but alloys having higher percentage of gadolinium content are only moderately cold-workable. All alloys can be hot-worked in iron sheathing at 750° C. Observation indicates that all compositions possess good machinability. Corrosion resistance to water at room temperature is apparently poor, especially in the gadolinium-rich alloys. INTRODUCTION A combination of the good mechanical and corrosion properties of titanium and the variety of thermal-neutron cross sections characteristic of the rare-earth metals suggests that alloys of these metals may be used for control rod materials. For this reason the Bureau of Mines proposed a study of the titanium-gadolinium alloy system, and the Atomic Energy Commission sponsored the investigation.

Jan 1, 1961

By E. C. Stephens

The eastern Washington— Idaho clay region stretches along the northeast margin of the Columbia basin for 150 mil es. The three better known and developed clay areas are Clayton, Wash., (2 miles north of Spokane); Mica, Wash., (10 miles southeast of Spokane); and Moscow-Deary-Bovill, Latah County, Idaho (about 80 to 90 miles southeast of Spokane) see Fig. 1. Clays from the eastern Washington— Idaho clay area have been mined for more than 50 years. At present Mica, Washington deposits are used by the Gladding—McBean & Co. to make a variety of bricks and ceramic products and Latah County, Idaho clays are used by the A. P. Green Fire Brick Co. to make refractories. The Anaconda Co. made an intensive investigation of the clay deposits in the northeastern Washington-!daho area in 1919 to determine the existence of a supply of raw materials from which alumina could be made. The greater part of the work, which included systematic drilling and shaft sinking, was concentrated at Mica, Wash. This was part of a research project carrted on by the Anaconda Metallurgical Research Dept. under the direction of Frederick Laist and F. Frick and it was terminated in 4920. V. D. Perry, Vice President and Chief Geologist for The Anaconda Co., in 1952 assigned the writer to make a preliminary study of clay and other potential sources of alumina ore in the Pacific Northwest with particular emphasis on those deposits which might be of future importance to The Anaconda Co9s. then new aluminurri plant at Columbia Falls, Mont.

Jan 1, 1961

By D. S. Hutton, W. C. Leslie

Thermal etch patterns developed on poly crystalline 3.5 pct Si-Fe by heating in hydrogen or in argon have been examined. The most prominent feature of the etching is the development of striations on grains with (100) planes near the plane of the surface. These striations are probably produced by the resoution of a random, high-energy plane into (100) facets of lower energy. THE thermal etching of iron and iron-base alloys has a long history. The phenomenon was observed by Osmondl more than 70 years ago. The literature on thermal etching between that time and 1951 was reviewed by Olney,2 and a briefer review appeared in 1958. 3 The only articles which have been found dealing with the thermal etching of silicon iron are those of Dunn and Lionetti4 and of Dunn, Daniels, and Bolton,5 and they reported only grain boundary etching. EXPERIMENTAL PROCEDURES A cast 3.5 pet Si-Fe alloy was given a metallo-graphic polish and etch, then placed in flowing purified hydrogen for 6 hr at 2200°F. The same specimen was later repolished and etched to remove the thermal etching. The specimen was then held in flowing purified argon at 2200°F for 72 hr. In both instances the specimen was rapidly cooled by being pulled up quickly into the cold zone of the furnace. All photomicrographs shown are of the surface as removed from the furnace. Oblique illumination was essential for observation of the thermal-etching effects with a light microscope and was used for all the photomicrographs. RESULTS AND DISCUSSION Grain boundary etching, grain boundary movement, and contouring within grains are illustrated in Fig. 1. The contours within a single grain followed behind the advancing grain boundary. To determine the average contour interval, or step height, white light was used in an interference microscope. The steps were of the correct magnitude to separate while light into its spectrum of colors. A green light was focused at the top of a contoured area, shifting to red across the field. By using the difference in the dominant wave length of red and green light,6 and counting the number of steps across the area, it was possible to obtain a value of about 80A for the average step height. Laue back-reflection patterns of four grains with contour lines showed that the grains had a (100) plane slightly inclined to the plane of the surface (± 5 deg). Insofar as this could be determined from their irregular traces, the contour lines within a grain had a common direction, <100> ± 5 deg.

Jan 1, 1961

By W. J. Helfrich, C. L. Sollenberger

Many present direct reduction processes utilize iron ore concentrates for the production of sponge iron and the sponge iron is usually preferred as an agglomerate. Pelletizing a high grade iron oxide concentrate prior to reduction is a simple approach to the high capacity production of a uniform and agglomerated sponge iron product. The present paper describes the effect of different atmospheres and physical characteristics on the reduction of pelletized iron oxide concentrates. The kinetics of iron oxide reduction have been I studied by numerous investigators1-4 and a rate equation for the hydrogen reduction of hematite and magnetite has been proposed. Mc Kewan&apos; obtained kinetic data for the reduction of hematite spheres sintered at 13&apos;70°C (2498&apos;F&apos;). The kinetics of magnetite reduction was studied by Quets. He compacted the oxide at a pressure of 1 ton per sq cm and sintered the specimens to densities of 95 to 96 pct of theoretical. These studies demonstrated that the reduction of iron oxide is a topochemical process and that the rate of reduction is proportional to the receding surface area of remaining iron oxide. Thus, the measurement of the kinetics of iron oxide reduction depends upon the development of a measurable and well defined interface between metal and reacting oxide. It is evident that the reduction rate will be constant only when the rate of formation of the reaction product layer is constant. It was recognized by Joseph&apos; and Edstrom&apos; that the physical character of the oxide will determine the configuration of the interface between oxide and metal. The reduction of oxides which exhibit few pores or no interconnected pores should proceed by topochemical processes. However, if a massive or dense crystalline ore cracks during the reduction of the oxide, thus allowing the reduction to Proceed away from a well defined oxide/metal interface, then the observed reduction rate will vary or change during reduction. From a process standpoint, it would be difficult to apply absolute reduction rates determined for crystalline or nonporous iron oxide to the direct reduction of a porous pellet of iron ore concentrate. Most present direct reduction processes are attempts to utilize iron ore concentraates in the production of sponge iron. The sponge iron is usually preferred in an agglomerated form for subsequent melting practices. Pelletizing a high grade iron oxide concentrate prior to reduction is a simple approach to the high capacity production of a uniform and agglomerated sponge iron product. One process for preparing such a product has already been de-scribed. This paper describes the effect of different atmospheres and physical characteristics on the reduction of pelletized iron oxide concentrates. ORE CONCENTRATES STUDIED A magnetite concentrate from Reserve Mining Co. and a hematite concentrate from U.S. Steel Corp. were used in preparing pellets for these experiments. A head analysis of these concentrates is given in Table I. To compare the reduction rates of pelletized concentrates, it was necessary that each pellet contain equal amounts of oxygen which could be removed by reduction, regardless of the oxidation state, i.e., Fez% or Fe304. Also, because of the difficulty in preparing spherical pellets of uniform size, weight, density, and porosity for experimental purposes, pellets of a cylindrical shape were formed in a press.

Jan 1, 1961

By H. W. Fleming, R. R. Brooks

The Clearwater Deposit, a small occurrence of massive-sulphide mineralization enclosed in an envelope of disseminated-sulphide mineralization, was discovered as a result of an aeroelectromagnetic survey in New Brunswick in 1955. Subsequently, additional flights were made over the deposit and various ground follow-up methods were employed to ascertain the nature of their response. All methods proved to be capable of indicating the occurrence with varying degrees of precision. This paper is a presentation and a discussion of the magnetic and electromagnetic data, both airborne and ground, and the self-potential data obtained over this deposit. The attention of Canadian mining exploration companies was initially focussed on New Brunswick by the discovery, in 1953, of the Brunswick ore body. Ground electromagnetic surveys were of considerable assistance in locating and developing this deposit. In the following year, 1954, the Heath Steele base-metal deposits were discovered by employing an airborne electromagnetic device and ground electromagnetic surveys to follow-up the airborne indications. These discoveries demonstrated clearly that both airborne and ground electromagnetic techniques were applicable for locating the near-surface deposits of massive sulphides present in this region. Airborne electromagnetic equipment became available on a contract basis through Aeromagnetic Surveys Limited early in 1955 and was used extensively thereafter throughout a large portion of northern New Brunswick. It was as a result of one of these surveys with Aeromagnetic Surveys Limited equipment in the summer of 1955 that the Clearwater Deposit was detected. The airborne anomaly was located on the ground by means of an electromagnetic survey using a Swedish Slingram unit. During 1956, the region was investigated more thoroughly- in the hope that other sulphide bodies might be located. Airborne electromagnetic coverage was extended and the Clearwater Deposit itself was used as a testing ground for the various methods and types of equipment currently in use in New Brunswick. In this paper com prative data are presented for the airborne magnetic, airborne electromagnetic, ground magnetic and ground electromagnetic surveys over this deposit. The ground electromagnetic instruments used were the McPhar vertical-loop unit and the Slingram and Boliden horizontal-loop units. Self-potential surveys were carried out with a McPhar unit. From the geophysical point of view, all ground electrical methods employed indicated the presence and the extent of the massive-sulphide mineralization with a good degree of accuracy. The horizontal-loop methods however, defined the contacts more precisely as is to be expected when dealing with a flatly-dipping

Jan 1, 1961

By J. D. Meakin

The self-diffusion coefficients of ß tin have been deterttlltled using a plating and sectioning technique. The principal diffusivities pavallel and perpendicu1ar to the "c" axis are given by the Arrhenius relations Dc = 8.2 exp (-25,600/RT) sq cnl per sec and Da = 1.4 exp (-23,300/RT) sq cm) per sec. The results are discussed in terms of a vacancy mecharism of diffusion. In conjunction with an investigation of diffusion in dilute indium-tin alloys we have reexamined self-diffusion in tin single crystals. The published self-diffusion coefficients of tin, eensham&apos;) have always appeared anomalous in comparison to diffusion data for other metals and do not correlate with parameters derived from creep tests.&apos; In addition to the necessity of confirming the self-diffusion values for use in analyzing the alloy work, self-diffusion in an anisotropic lattice is of considerable fundamental interest and confirmation of the published data seemed worthwhile. For a crystal with an axis of symmetry three-fold or higher the diffusivity at an angle 6 to the axis is given by D? = (Da - Do) sin2?+ Do [1] where Da and Do are the principal diffusivities perpendicular and parallel to the axis. For a particular diffusion mechanism, again in a crystal of axial symmetry, these principal diffusivities are [2] Do - ? ?i2 COS?i In these expressions ?i is the displacement undergone by the ith atom and 8, is the angle this displacement makes with the symmetry axis. In this, as

Jan 1, 1961

By F. N. Ward, E. H. Bailey

Camp and sample-site methods useful for determining about 0.5 to 16 ppm of mercury in soils and rocks have been devised to complement the analytical methods already widely used in geochemical prospecting. In the camp-site procedure the sample solution is obtained by digesting the finely powdered sample with hot nine-molar sulfuric acid and bromine, the latter generated in place. The solution is buffered at a pH of 4 and the mercury is extracted into a relatively small volume of an organic solvent. Estimations are made by comparing the color of the mercuric dithizonate extracted from the sample with that extracted from a standard. In the sample-site method the mercury is volatilized as the iodide and the latter is dissolved in a buffer solution from which the mercury dithizonate is extracted as in the camp-site method. The estimation is made by a similar comparison with standards or by comparing the color of the mercuric dithizonate with artificial standards prepared from Orange II, an azo dye. Except for the establishment of standards, the time required by an experienced analyst seldom exceeds 10 min for a camp-site determination and 5 min for a sample-site determination. Camp-site determinations are useful for commodity studies and intensive exploration programs; sample-site determinations are applicable to extensive and reconnaissance-type geochemical prospecting programs. The results obtained on samples taken along traverses above known mercury ore deposits in the California Coast Range and western Nevada demonstrate the usefulness of both methods in geochemical prospecting. The increasing use of the mercury content of soils, rocks, plants, or water in geochemical prospecting emphasizes the need for analytical methods which are sensitive and at the same time require a minimum of readily available equipment. Sensitive methods based on the absorption of ultraviolet light by mercury vapor are common in the literature31 12. Although none of these methods have been used to analyze the large number of samples required in geochemical prospecting, they could be extremely useful except for the expensive instrumentation usually required to make the methods quantitative Also, such methods are perhaps too sensitive for field use, especially around areas of possible contamination. Other methods involve the distillation of mercury from a relatively large sample and subsequent collection of the vapors in nitric acid6. The mercury is then estimated by titration with a suitable reagent such as thiocyanate. These methods are not trace methods because the actual amount of mercury measured is often as great as 50 to 100 milligrams. Also, such methods are unsuitable for geochemical prospecting because of the amount of equipment necessary and the time required. Still other methods involve colorimetry, and the sensitive reaction between dithizone and mercury (11).. is the basis for a number of reports on the determination of mercury in biological materials 5,7. Moreover, by the judicious use of solvent extraction and suitable complexing agents, the dithiaone method can be made almost specific for mercury. However, none of the dithizone methods have yet been applied to the determination of mercury in soils and rocks. In most colorimetric methods he sample solution

Jan 1, 1961

By O. A. E. Jackson

In all three principal dunite dikes, minute disseminated grains of pyrrhotite are to be seen in the fresh rock in amounts less than 1 pct. Traces of nickel have been reported from many such specimens. Nickeliferous pyrrhotite is the principal nickel-bearing mineral, although olivine contains very minor amounts of nickel in solid solution, substituting for magnesium and iron. Such occurences are of no economic significance. Nickel analyses of possible economic significance (up to 3 pct Ni) have been returned from samples taken near the margins of the two large western dunite dikes. These samples were from schistose zones along and within the dike walls. The mineralized shear zones, up to 30 ft wide, strike N 30 W and dip from 65" to 90" west. They consist of layers of hard, fresh, green-gray dunite, mineralized with finely disseminated pyrrhotite. These layers alternate with layers of soft, black, oxidized schistose dunite up to 1 ft wide, well mineralized with pyrrhotite and tabular-fractured pentlandite in crystals up to 1/4-in. diam. Sulfides identified in polished sections were chiefly pyrrhotite and pentlandite, with much smaller amounts of chalcopyrite. There are two varieties of pyrrhotite. One develops a fine polish and conforms to published descriptions. The other is slightly darker and browner, does not polish as well, and displays flamelike growth or intergrowth structure when etched with nitric acid fumes. Pyrrhotite and pentlandite crystallized contemporaneously in the form of veins in the olivine and as fillings of the interstices of euhedral olivine crystals. Chalcopyrite replaces the other sulfides. The most striking feature of the deposits is their occurrence in intimately fractured and schistose zones in the dunite where faulting has been localized along the contacts of the sediments and the dunite dikes. Though far too little detailed work has been done to be certain, there appears to be a higher concentration of sulfides in the shear zones along the margins of dike apophyses, sediment reentrants, and strike and dip irregularities. Much more study would be required in order to submit a plausible theory of formation of the nickel deposits, supported by laboratory and field evidence. Results of the present study, especially localization of the metals by fracturing, certainly indicate that the nickel concentrations were brought about by precipitation of nickel sulfides from fluids that used the fractures as a means of ingress. Studies of nickel sulfide deposits throughout the world have demonstrated that such sulfides were deposited at considerable depths and at temperatures of several hundred degrees. This would rule out the possibility of groundwater as the transporting medium. The two possible sources of hot nickel-bearing fluids are quartz diorite and gabbro. The first possibility is that large volumes of fluids, expelled from the quartz diorite magma during its crystallization, obtained a supply of nickel by altering the nickeliferous olivine of the dunites. The likelihood of this process is lessened by the recognition that, although the dunites show some alteration to serpentine, talc, and trem-olite, they are for the most part remarkably fresh outside the schistose zones. The worldwide association of nickel with basic rocks, together with the presence of pyrrhotite in thin films on joint planes of the gabbro on Jumbro Mountain, favors the gabbro source. The writer extends thanks to C. Phillips Purdy, Jr., project chief of American Metal Climax Inc., for giving him the opportunity to study these deposits. He is also indebted to the officers of American Metal Climax Inc. and Discovery Mines Inc. for permission to publish this article.

Jan 1, 1961

By W. A. Weimer

Coal and coal mining is no longer the mighty king of industry and in our daily lives and homes that it once had the privilege of commanding. Many of you will remember that one of the chores of your youth was to bring in the scuttles of coal, morning and night, to feed the heater or stoke the furnace in the morning and bank it at bedtime. Growth of gas and oil have displaced coal in home furnaces and commercial buildings, and have taken over some segments of industrial markets. The coal burning locomotives have virtually disappeared in favor of the more efficient diesel engine. However, coal as a prime mover still holds its strategic position as is evidenced by act that the electric power industry almost entirely depends upon coal for its generation.

Jan 1, 1961

By A. W. Ruff

The seismic wave produced by an explosive is very important in blasting. A true understanding of the wave is only important when considering possible structural damage to buildings located near the blast, but it is also of primary importance when considering rock fragmentation. Because of the importance of the seismic wave to fragmentation, a finda-mental study of the seismic wave and its effect was made at the Cananea Consolidated Copper Co.&apos;s mine at Cananea, Sonora, Mexico. Strain gages were used to measure the strain in the rock when nearby explosive charges were detonated. The variance in the circuit voltage caused by changes in the resistance of the strain gage was measured with an oscilloscope and recorded with a Polaroid camera. CONFINED DRILLHOLE CHARGES To record the seismic wave from a confined drillhole explosive charge, a gage was cemented to the bottom of a 4-in diam drillhole. The horizontal gage hole and nine horizontal charge holes were drilled perpendicular to the center line of the 2-39 drift and 4 ft above the floor. The gage hole was 29 in. deep, and the charge holes were drilled so that each bottomed 1 in. deeper than the gage hole. The gage was installed with its axis horizontal and parallel to the 2-39 drift. The charge holes had the following horizontal distances from the gage: hole 3, 3 ft; hole 4, 4 ft; hole 5, 5 ft; hole 9, 9 ft; hole 10, 10 ft; hole 14, 14 ft; and hole 15, 15 ft. Figs. 1 and 2 show the relationships of the gage and the charge holes. Charges of 80 pct special gelatin, which weighed 50, 100, and 150 g were exploded in the charge holes and the seismic waves were recorded. All charges were stemmed with 200 g of mud and detonated with an electric blasting cap. Fig. 3 shows the recorded seismic waves. The reflected components of the waves were too weak to be objectional on these records. Table I shows the data taken from the wave forms. The approximate average velocity of a wave with a 9-ft travel distance was 12,900 fps. Since different charge weights were used, it was necessary to scale the data. The scaled maximum compress ion-strain data and the scaled maximum tens ion-strain data are shown in Figs. 4 and 5, respectively. Figs. 6 and 7 show the strain-distance data from Figs. 4 and 5 converted to a 1-lb charge. The results showed that the wave consisted of an initial compression pulse followed by a tension pulse. The amplitude of the tension pulse approached the amplitude of the compression pulse as the distance between the gage and the shot increased. The decay rate of the seismic wave is very important in the evaluation of the blasting characteristics of a rock. When high-amplitude stresses are produced, as in rock fragmentation, the rate of decay is much more rapid than when small amplitude stresses are produced. In underground mine blasting, the burdens are usually not greater than 6 ft and the decay is very rapid. The rapid seismic-wave decay rate in the fragmentation range means that in practice, if the minimum weight of powder is used to break a specified burden, only a very

Jan 1, 1961

By J. B. Fletcher

The Miami mine first started operations in 1910. For convenience, the history of the orebody can be divided into the following categories (Fig. 1): 1) 1910 to 1925: 24.4 million tons of high grade ore, mined by top slicing, sublevel caving, etc. 2) 1926 to 1954: 102 million tons of low grade ore, mined by block caving.

Jan 1, 1961

By C. H. Li, S. H. Bendel, J. A. Sartell

Small additions of Mg to a 62 Cu-38 Ni alloy reduce the oxidation yates drastically between 500° and 850°C. Metallographic examination of the oxide scale disclosed a continuous network, identified by X-ray diffraction as (Ni, Mg)O solid solutions, located along the former alloy grain boundaries. This network acts as a barrier to diffusion. It is thought to result from the segregation of mg to the alloy grain boundaries. Oxidation occurs preferentially in these regions because of the presence of this more active element. To substantiate these ideas, homogenized alloys ulere oxidized. No oxide network was produced and oxidation rates were the same as for the parent 62 Cu-38 Ni alloy. An interesting aspect of the oxidation of the 62 Cu-38 Ni alloy previously described by the present authors, is the relationship between oxidation kinetics and changes in the microstructure of the oxide.&apos; The oxide scale on these alloys consists of two layers: a thin layer of CuO outside a much thicker layer of Cu20 in which particles of NiO are dispersed. In addition, immediately beneath the oxide-metal interface there is an internally oxidized zone in which NiO particles are dispersed in a copper-rich alloy matrix. Experimental observations on the growth of the individual layers under isothermal conditions have led to the conclusion that the rate-determining step in the oxidation of this alloy is the diffusion of anions through the Cu20 layer. It has been found that this diffusion rate is increased by the recrystallization of the outer CuO layer. Willardson and Gorton have reported that the addition of magnesium to the 62 Cu-38 Ni alloy causes a decrease in the oxidation rate.2 The present investigation was undertaken in order to determine the mechanism by which magnesium additions improve the oxidation resistance of the 62 Cu-38 Ni alloy. EXPERIMENTAL PROCEDURE Fifty-gram ingots of Cu-Ni alloys were prepared by vacuum melting materials of 99.999+ pct purity. These ingots were then remelted in a He atmos- phere and magnesium added in the form of a previously prepared and analyzed Cu-Mg master alloy. This procedure was necessitated by the high reactivity of pure magnesium at high temperatures. The proportion of the alloying elements was adjusted so as to obtain alloys with the desired magnesium content while maintaining a Cu-Ni ratio of 62 :38 by weight. (All alloy compositions will be given in weight percent.) Since it was considered desirable to study the oxidation of only single-phase, solid-solution alloys, it was necessary first to determine the approximate limit of solid solubility of magnesium in the 62 Cu-38 Ni alloy. A series of melts with various magnesium contents was made, homogenized by annealing for 48 hr at 975OC, then cooled in the furnace. Metallographic samples were prepared, etched in a potassium dichromate solution and examined at XI500 for the presence of a second phase. The alloys were then chemically analyzed and it was found that the approximate limit of solid solubility of magnesium in the 62 Cu-38 Ni alloy was 1 pct Mg. The ingots containing less than 1 pct Mg (0.19, 0.29, 0.58, and 0.87 pct Mg) were cold-rolled down to thicknesses suitable for oxidation experiments and specimens for gravimetric studies were cut to dimensions of 3.0 by 1.5 by 0.05 cm, specimens for inert marker studies, 0.6 by 0.6 by 0.17 cm. These were heat-treated in a protective atmosphere at a temperature (975" C) well above the oxidation temperatures and furnace-cooled to insure structural stability of the alloy during oxidation. Immediately prior to oxidation, the specimens were chemically cleaned by immersion for 1 min in a solution of 2 parts nitric acid, 1 part acetic

Jan 1, 1961

By M. C. Fuerstenau, A. M. Gaudin

A homogeneous suspension is viewed by X-rays. The radiation density seen, affords a measure of the extra absorption due to the solids contained. This radiation density, at a predetermined depth, varies with time. The chart of this relationship gives the desired determination. s it is frequently necessary to know the distribu-rt tion of particle sizes in various products used in industrial applications, a number of means have been devised for these determinations. Some of them include direct microscopic measurement, screening of product, extraction of samples from a settling slurry, air and liquid elutriation, adsorption of gases and liquids, and light absorption. The absorption of light as a means for particle size analysis has been known and employed for some time. X-ray absorption has not received the attention that light has enjoyed primarily because of the complex and costly instrumentation involved with X-rays. In 1954, Brown and Skrebowskil suggested the use of X-rays for this type of determination but did not supplement their suggestion with experiment. In 1958, the authors conducted size analysis experiments on suspensions of quartz with the Trans-viewer: an X-ray unit specifically adapted for sedimentation research, and Rossa conducted experiments in a similar manner in 1959 with a stable gamma emitter, AmZ4l, on suspensions of uranium oxide. To illustrate the applicability of X-ray absorption for analyzing particle size distributions, an essentially mono-energetic and well collimated X-ray beam was used as a source. The beam was made mono-energetic by placing a zirconium filter before the counting window together with feeding the pulses from the proportional counter into a reverter, a device capable of discriminating against pulses of various heights. The sketch in Fig. 1 shows the collimation arrangement in more detail. As shown, the X-ray beam was collimated by inserting a 3/8-in. ID pipe into one of the ports of the X-ray tube and further by two small steel plates with slits 3/32-in. wide and 1/2-in. long placed in front of the window of the Geiger-Mueller (G-M) tube. One of the plates was located 1/2 in. and the other 2 1/2 in. from the window of the counter; both plates were contained in an aluminum holder mounted on the box containing the G-M tube. This type and degree of collimation should eliminate any intensity due to scattered radiation; the transmitted intensity would then be solely a functior. of the absorption by the suspension at that level. Experimentally, homogeneous suspensions of finely ground quartz were prepared, Daxad (a sulfo-nated compound made from wood) was added as dis-persant, and the transmitted X-ray intensity measured as a function of time at a fixed depth in the suspension. In more detail, the experimental procedure involved the following: 1) measuring the transmitted X-ray intensity through the Daxad solution at a predetermined position or settling depth in the absence of solids, 2) placing a known amount of dry solids into the vessel and agitating thoroughly, 3) measuring the transmitted X-ray intensity at time zero (i.e., immediately upon cessation of stirring), and 4) measuring the transmitted X-ray intensity as a function of time (a 10-sec counting interval being chosen and counting being started 5 sec before the desired time). Since a linear relationship exists between percentage solid in a slurry and the logarithm of transmitted intensity for a homogeneous material, the cumu-

Jan 1, 1961